physics.ins-det

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physics.ins-det 2026-05-14 2 theorems

GPU solver speeds 3D diamond sensor simulations

GPU-Accelerated Simulation of 3D Diamond Sensors Using the TeRABIT Infrastructure

Porting the third-order PDE solver for time-dependent weighting potentials to GPUs cuts computation time and enables geometry optimization.

abstract click to expand

Diamond detectors with electrodes orthogonal to the surface, engraved via laser-induced graphitization, are full-carbon sensors of interest for a wide range of applications, spanning from High Energy Physics to Nuclear Medicine and dosimetry. In recent years, significant progress has been made in graphitization techniques, enabling the fabrication of lower-resistance electrodes. This has resulted in faster sensors, achieving time resolutions better than 100 ps. However, simulating signal formation in these devices remains a challenge. The effects of fluctuations in energy deposition, carrier transport, signal propagation, and readout electronics intertwine in a way that is non-trivial to disentangle. We have developed an innovative simulation approach based on an extension of the Ramo-Shockley theorem, modeling propagation effects in a theoretically sound manner by introducing time-dependent weighting potentials. These are obtained by solving a third-order partial differential equation derived as a quasi-static approximation of Maxwell's laws. The numerical solution of this equation emerged as the main challenge of the new approach. In this contribution, we discuss an innovative solver that uses fundamental solutions to impose boundary conditions and spectral methods to extend the solution to the bulk of the diamond detector. We report on how the solver has recently been ported to GPUs and distributed across multiple computing sites, leveraging the TeRABIT HPC Bubbles and the InterLink protocol. This drastically reduces time-to-insight and effectively enables what-if studies on sensor geometry.

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physics.ins-det 2026-05-14

Simulation flow predicts MAPS timing from charge creation to digital output

Application of exhaustive simulation flow for advanced performance prediction of monolithic active pixel sensors

Layout wells and Monte Carlo-SPICE coupling give leakage currents and ToA/ToT under irradiation for Belle II sensors

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Monolithic active pixel sensor (MAPS) developments have pushed the detection performance in various directions, especially relative to timing where nanosecond-level precision is now considered. This evolution calls for a simultaneous upgrade of the simulation tools. We have developed a simulation flow that covers steps from the signal creation in the sensitive volume to the output of the pixel digital logic that performs the time-of-arrival and time-over-threshold (ToA/ToT) measurements. This approach adds several new features to the traditional use the of the TCAD - Allpix Squared duo, among which : the integration of the pixel wells from the layout in order to precisely describe the pixel key characteristics such as leakage and punch-through currents and the coupling of Monte Carlo simulations (Allpix Squared) with high precision electrical simulations (SPICE). The first (Allpix Squared) for the precise description of the current induced at the collection electrode and the second (SPICE) to guarantee high precision simulation of the front-end electronics using realistic signal events. Irradiation is also modeled, both from the charge propagation side (charge trapping) and from the front-end response side (high input signal discharge). We have applied this methodology to the MAPS developed in the context of the Belle II vertex detector upgrade. In this contribution, we detail the key features of the exhaustive simulation flow, present the outcome of the comparison with the TJ-Monopix2 measurements and discuss the interest of the methodology for the development of modern MAPS.

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physics.ins-det 2026-05-14

Neural net boosts neutron-gamma ID at low signals

SINAPSE: A lightweight deep learning framework for accurate and explainable neutron-γ discrimination

Dual-branch model trained on augmented high-SNR data outperforms traditional cuts and bases decisions on physical pulse features.

abstract click to expand

Traditionally, neutron-$\gamma$ discrimination in organic scintillators relies on techniques such as time-of-flight (ToF) selection and pulse-shape discrimination (PSD). However, particle identification through graphical cuts remains challenging in the low-charge regime due to poor signal-to-noise ratios (SNR). In this work, we propose SINAPSE, a lightweight deep learning framework for accurate and explainable neutron-$\gamma$ discrimination in the low-charge regime. The framework employs a dual-branch architecture that combines a 1-dimensional convolutional autoencoder for waveform denoising with a classifier for particle identification. Random augmentations are applied to high-SNR waveforms to simulate low-charge conditions, enabling robust extrapolation into regimes where conventional PSD labels are unreliable. We show that SINAPSE achieves superior denoising performance compared to conventional digital signal processing techniques, and outputs well-calibrated probabilities, consistent with traditional graphical cuts. Finally, we apply SHAP (SHapley Additive exPlanations) values to show that model decisions are driven by physically meaningful pulse-shape features, confirming consistency with established PSD principles.

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physics.ins-det 2026-05-14 2 theorems

OBELIX sensors upgrade Belle II vertex detector for 6x luminosity

Upgrade of the Belle II Vertex Detector with Depleted Monolithic CMOS Active Pixel Sensors

Predecessor chip tests confirm operation below 40C after heavy irradiation for hit rates up to 120 MHz per cm2.

abstract click to expand

The Belle II experiment, operating at the asymmetric SuperKEKB $e^+e^-$ collider, is preparing an upgrade of its vertex detector to cope with an increased luminosity of $6 \times 10^{35}$ cm$^{-2}$s$^{-1}$. The upgraded vertex detector (VTX) will consist of five or six layers of depleted monolithic active pixel sensors (DMAPS), with a total material budget of approximately $3\%$ $X/X_0$. The OBELIX chip, derived from the TJ-Monopix2 sensor and fabricated using Tower Semiconductor 180 nm CMOS technology, is being developed for this upgrade. It features a 33 $\mu$m pixel pitch with a time-stamping binning of $50-100$ ns, along with a dedicated digital periphery compatible with the Belle II trigger system, supporting rates up to 30 kHz. The sensor is designed to operate under the high background conditions expected at the target luminosity, with radiation tolerance up to $5 \times 10^{14}$ $n_{eq}$/cm$^2$ and 100 Mrad, while targeting a power density of about 200 mW/cm$^2$. This corresponds to hit rates up to 120 MHz/cm$^2$. Beam test and irradiation studies of TJ-Monopix2 demonstrate that the operating sensor temperature should stay below $40^\circ$C after irradiation up to $5 \times 10^{14}$ $n_{eq}$/cm$^2$. This report reviews the proposed VTX concept, sensor performance, and ongoing R$\&$D activities.

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physics.ins-det 2026-05-14 Recognition

Gamma-trained ML rejects alphas in Ge detectors at 27,000-to-1

Pulse shape discrimination for α event rejection in BEGe-type high-purity germanium detectors

Multilayer perceptron preserves over 80 percent of signal-like events while cutting background-like survival below 20 percent.

abstract click to expand

High-purity germanium detectors are widely used in rare-event searches due to their excellent energy resolution and extremely high intrinsic (radio)purity. In experiments searching for neutrinoless double beta decay in $^{76}$Ge such as LEGEND, pulse shape discrimination is required to suppress multi-site $\gamma$ events. In this work, we investigate whether pulse shape discrimination classifiers trained exclusively on $\gamma$ ray data can be used to identify and reject $\alpha$ events, without the need for dedicated $\alpha$ training. In detectors such as LEGEND, the total number of registered $\alpha$ events over the experiment lifetime is expected to be insufficient to train dedicated classifiers, while still contributing to the background. Two approaches based on machine learning are studied: a multilayer perceptron and a projective likelihood classifier. The p+ surface of a point-contact semi-planar germanium detector was exposed to $^{209}$Po and $^{210}$Po sources deposited on a thin gold foil. Two measurement campaigns were performed, yielding $1.36\times10^{5}$ and $1.87\times10^{6}$ $\alpha$ events, respectively. Both classification methods achieve efficient separation of single-site and multi-site $\gamma$ events while strongly reducing the $\alpha$ component. The multilayer perceptron provides the best overall performance, with a signal-like event survival greater than 80%, a background-like event survival below 20%, and an $\alpha$-rejection factor exceeding $2.71\times10^{4}$. These results demonstrate that robust pulse shape discrimination for high-purity germanium detectors can be achieved using training information derived solely from $\gamma$ events, providing a promising strategy for next-generation neutrinoless double beta decay searches.

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physics.ins-det 2026-05-14 2 theorems

Ultra-thin 3D sensors reach 50-micron thickness with small pixels

Development of Small-pitch, Ultra-thin 3D Silicon Sensors at USTC

50-micrometer active layers and 25-micrometer pixels are built to deliver simultaneous position and time information from each pixel.

abstract click to expand

We report on the development of 3D silicon sensors at the University of Science and Technology of China (USTC). The sensor involves columnar electrodes (5 um in diameter) of both doping types, etched from the same wafer side. The p+ electrodes pass through the epitaxial wafer, whereas the n+ electrodes stop at a short distance from the opposite side of the epitaxial wafer. With respect to previous generations of 3D sensors, they feature an ultra-thin active substrate (50 um) and a small pixel size of 50 um x 50 um or 25 um x 25 um. This R&D project aims to establish a sensor technology to simultaneously measure position and time information at the single-pixel level. The first run with one merged wafer layout has been completed. The design, fabrication, and characterization of the sensors are reported in this paper.

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physics.ins-det 2026-05-14 1 theorem

SiC PIN detector keeps 99 percent CCE after Ta ion exposure

Stable Charge Collection and Sub-45 ps Time Resolution in a 4H-SiC PIN Detector Irradiated With Low Fluence 16.5 MeV/u Ta Ions

Time resolution holds at 45 ps with leakage current and doping unchanged, supporting radiation-hard use in physics and space.

abstract click to expand

A silicon carbide PIN detector was fabricated and its radiation tolerance under Ta heavy ion irradiation of 2370 MeV was evaluated. Its electrical properties, charge collection performance and time resolution of $\beta$-particles ($^{90}$Sr) are reported. The leakage currents for unirradiated and irradiated 4H-SiC PIN detectors are $1.47 \times 10^{-10}$~A @ 300 V and 1.49~$\times$ 10$^{-10}$A@ 300 V. The effective doping concentrations for unirradiated and irradiated 4H-SiC PIN detectors are $6.23\times 10^{13}$~cm$^{-3}$ and $6.13\times 10^{13}$~cm$^{-3}$. The irradiated detector exhibits good electrical performance and stable device architecture. The 4H-SiC PIN detector exhibits a charge collection efficiency (CCE) of 99.24\% under Ta Heavy Ion Irradiation. The time resolutions of the detector before and after irradiation are 40 ps and 45 ps, respectively. Experimental results indicate that the CCE and time resolution performance exhibit good stability before and after irradiation. These results demonstrate stable performance under Ta heavy ion irradiation, highlighting the detectors potential for radiation-hard applications in high-energy physics, space missions, and nuclear reactor monitoring.

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physics.ins-det 2026-05-14 2 theorems

Four-face SiPM readout hits 68 ps timing resolution

Development of a sub-100 ps Time-of-Flight detector with SiPM-readout scintillator for measurement of cosmic muon velocity

Series-connected modules on scintillator sides beat hybrid design for precise cosmic muon speed measurement

abstract click to expand

Accurate Time-of-Flight (TOF) measurement with sub-100 picosecond resolution is a critical requirement for particle identification in future high-energy physics experiments, such as the Belle II $K_{L}$ and Muon (KLM) detector upgrade. Achieving this precision with large-area Silicon Photomultipliers (SiPMs) is challenging due to the inherent junction capacitance, which degrades signal rise time. In this work, we developed and evaluated a high-time-resolution cosmic ray detector based on plastic scintillators and customized SiPM arrays. To optimize the readout for block-shaped scintillators, we systematically compared different sensor topologies. We demonstrate that a multi-face readout topology, utilizing low-capacitance 4-series (4S) SiPM modules coupled to four faces of the scintillator, achieves an excellent coincidence time resolution of approximately 68 ps, outperforming the $\sim$100 ps resolution of the concentrated 4-series 3-parallel (4S3P) hybrid topology. Furthermore, to validate the system's practical performance, we successfully measured well-known cosmic ray observables, specifically the relativistic muon velocity via TOF reconstruction. These results highlight the potential of the multi-face 4S configuration as a high-precision solution for future TOF detector upgrades.

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physics.ins-det 2026-05-14 2 theorems

The paper describes tests of a portable RPC telescope at the ELBA laser-plasma facility…

RPC Telescope Tests for Muon Detection at Laser-Plasma Accelerators

RPC detectors were tested at a laser-plasma accelerator and demonstrated reliable operation for potential muon detection despite limited…

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We report on a feasibility study conducted at the ELBA facility at ELI Beamlines in 2025 to investigate the possible production of muons from high-energy electron beams generated by extended laser-plasma interactions in optically generated plasma waveguides. Our team operated a portable, autonomous, and compact telescope based on Resistive Plate Chamber (RPC) detectors, positioned to detect high-penetration charged particles originating from the beam dump. The campaign demonstrated that RPC detectors can operate reliably and safely in the ELBA environment, even under intense radiation and electromagnetic conditions. The collected datasets, though statistically limited and affected by lack of beam control, allow detailed characterization of the background and validated the detectors' stability and tracking performance. These results confirm the feasibility of the approach and provide the foundation for a dedicated future run under optimized beam conditions, where muon detection sensitivity will be substantially improved.

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physics.ins-det 2026-05-13 2 theorems

Generative models learn neutron sources from Monte Carlo lists

Machine Learning for neutron source distributions

After training, the models generate new particles rapidly and without storing the original data, offering a lighter alternative for neutron-

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In light of the recent advancements in machine learning, we propose a novel approach to neutron source distribution estimation through the utilisation of probabilistic generative models. The estimation is based on a Monte Carlo particle list, which is only required during the training stage of the machine learning model. Once the source distribution has been learned, the model is independent of the original particle list, allowing for further sampling in an efficient, rapid, and memory-costless manner. The performance of various generative models is evaluated, including a variational autoencoder, a normalizing flow, a generative adversarial network, and a denoising diffusion model. These approaches are then compared to existing source distribution estimations, and the advantages and disadvantages of each approach are discussed. The results demonstrate that source distributions can be modeled through the use of probabilistic generative models, which paves the way for further advancements in this field.

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physics.ins-det 2026-05-13 Recognition

Large patches and x-prediction cut calorimeter shower generation cost

CaloArt: Large-Patch x-Prediction Diffusion Transformers for High-Granularity Calorimeter Shower Generation

Voxel-space diffusion transformers match top fidelity scores on two challenge datasets while finishing each shower in about 10 ms on one GPU

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High-granularity calorimeters make ML-based fast shower simulation a high-dimensional generative modeling problem, where voxel-space generators must balance physics fidelity with training and inference cost. This work studies large-patch tokenization with x-prediction, enabling efficient raw voxel generation. We propose CaloArt, a modernized DiT-style backbone with 3D positional encoding and architectural refinements, trained via conditional flow matching with decoupled prediction and loss spaces. On CaloChallenge Dataset 2, where small patch size remains affordable, v-prediction performs well, and CaloArt achieves the best FPD, strongest high-level metrics, and strongest ResNet classifier metrics. On CaloChallenge Dataset 3, the 40500-voxel grid makes large patches necessary; x-prediction improves all reported metrics over v-prediction and places CaloArt on the quality-generation-time Pareto frontier. The final CCD2 and CCD3 models both retain O(10) ms single-GPU generation time, with 9.71 and 11.14 ms per shower. These results support large-patch voxel-space diffusion transformers with x-prediction as a compute-efficient route to high-granularity calorimeter shower synthesis, reducing training and inference cost without a pretrained latent tokenizer.

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physics.ins-det 2026-05-13 Recognition

0.7-4 MeV neutron source validated at CN Van de Graaff

Development and validation of a forward 0.7--4 MeV quasi-monoenergetic neutron capability at the CN Van de Graaff of LNL

Forward 7Li(p,n) neutrons achieve 9 percent fluence accuracy after ToF checks and consistent transport calculations.

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The CN Van de Graaff accelerator of INFN--LNL provides forward-angle quasi-monoenergetic neutrons in the 0.7--4 MeV range via the 7Li(p,n)7Be reaction on thin metallic lithium targets. This work describes the development and experimental validation of this forward neutron capability, combining comparisons of commonly used transport tools with time-of-flight (ToF) measurements. Neutron yields calculated with EPEN, FLUKA, MCNPX, and PINO are compared over the CN energy range in order to assess model-dependent variations relevant for fluence estimates. For zero incident-energy spread, a mutually consistent set of transport calculations agrees within 5% and is used as a practical reference for normalisation. The effect of incident-energy convolution on the predicted yields is examined. Time-of-flight measurements performed using a sub-nanosecond secondary pulsing system verify the timing structure and forward-angle kinematics of the quasi-monoenergetic neutron component at the detector position, with neutron arrival times consistent with the expected forward kinematics within the experimental resolution. Using measured proton currents and transport calculations based on this reference set, forward neutron fluences at the device position are estimated with an overall uncertainty of approximately 9%, including contributions from current integration, target thickness, and geometry. A short device irradiation, carried out in parallel with the ToF campaign, demonstrates measurable response under CN beam conditions and confirms the practical usability of the beam for low-MeV neutron studies. Together, these results establish the current operational performance of the CN 0{\deg} forward quasi-monoenergetic neutron capability in the 0.7--4 MeV range and identify the steps required toward routine calibrated operation.

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physics.ins-det 2026-05-13 Recognition

Pixel sensor reaches 100% efficiency over 226 micrometers

TPA-TCT Analysis of the RD50-MPW4 Monolithic Pixel Particle Detector

Backside laser mapping of the RD50-MPW4 shows full charge collection and edge sharing between neighboring pixels.

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The RD50-MPW4, a Depleted Monolithic Active Pixel Sensor (DMAPS) was analyzed using a Two Photon Absortion Transient Current Technique (TPA-TCT). This technique provides sensitivity maps with micrometer-scale spatial resolution, enabling the resolution of the boundaries of the detector's sensitive volume, even for small-area pixels (62x62 squared micrometers in this study). With a full 3D resolution, the depletion depth, the boundaries of the detector electric field, the 3D hit detection efficiency and the charge sharing between neighboring pixels were measured. The RD50-MPW4, a multi-project wafer chip developed by the HV-CMOS working group within the CERN RD50 collaboration, features a 64x64 DMAPS pixel matrix. Illuminating the chip from the backside, the TPA-TCT technique can characterize any pixel element in the matrix because silicon is transparent for near infrared laser light (1550 nm). Electron-hole pairs are generated only around the light focal point, deep in the silicon, so that any charge collected is precisely only from the focal point. With the TPA-TCT technique, the RD50-MPW4 was found to be have a 100\% charge collection efficiency and a depletion depth of 226 $\upmu$m. It was also found that part of the charge in the periphery of the pixel was collected in the neighboring pixel. A 3D map of the sensor clearly shows the in-pixel electronics and the limits of the depletion region.

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physics.ins-det 2026-05-13 2 theorems

Hyper-K outer detector cuts cosmic muons to one in a million

Outer Detector of Hyper-Kamiokande

OD-based cuts reach 10^{-6} inefficiency alone and 10^{-9} with fiducial cuts, making backgrounds negligible for rare-event searches.

abstract click to expand

Hyper-Kamiokande (HK) is the world's largest water Cherenkov ring-imaging detector, planning to start data taking in 2028. The Outer Detector (OD) surrounds the Inner Detector and plays a critical role in rejecting background events entering from outside, particularly cosmic-ray muons. We report on the selection of $8\,\mathrm{cm}$ diameter photomultiplier tubes (PMTs) for the OD, comparing Hamamatsu R14374 and NNVT N2031 candidates, and present the evaluation of cosmic-ray muon background reduction performance using a full detector simulation. Hamamatsu PMTs were adopted for their superior in-water detection efficiency in deep-UV and stability. The cosmic-ray muon reduction inefficiency reaches $O(10^{-6})$ with OD-based cuts alone, and $O(10^{-9})$ is expected when combined with fiducial volume cuts, which is sufficiently negligible for nucleon decay and atmospheric neutrino analyses.

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physics.ins-det 2026-05-13 2 theorems

EMFC method now exceeds 1000 tesla for material studies

Bridging the Gap between Extreme Environments and Precision Measurements: Recent Progress in Megagauss Physics

Miniaturized cryostats enable precise quantum measurements under these extreme pulsed fields

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Ultrastrong magnetic fields, ranging from 100~T to 1,000~T, are generated exclusively by destructive pulsed magnets. While various generation methods exist, this review focuses on the Single-Turn Coil (STC) and Electromagnetic Flux Compression (EMFC) techniques, which provide optimal environments for high-precision measurements in materials science. First, we present recent technological breakthroughs in the EMFC method that have successfully achieved fields exceeding 1,000~T. We then describe specialized measurement infrastructures for magneto-optics, magnetization, and magneto-transport, highlighting the development of miniaturized all-plastic cryostats and custom sample holders designed for the dual extremes of cryogenic temperatures and megagauss fields. Representative physical phenomena revealed through these techniques are discussed, including quantum phase transitions in frustrated magnets, Aharonov--Bohm effects in carbon nanotubes, and semiconductor-to-metal transitions in strongly correlated systems. Furthermore, we address emerging measurement platforms such as magnetostriction, specific heat, and ultrasound velocity. Throughout this review, we emphasize the instrumentation and experimental refinements that ensure reliable data acquisition in the ultrastrong pulsed field regime.

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physics.ins-det 2026-05-12 2 theorems

Opaque scintillator pilot confines light below 2 cm

Construction, commissioning, and beam test of a pilot 3D-projection opaque water-based liquid scintillator detector

Proton beam tests show tighter radial distributions than 2 cm simulation and 0.17-0.28 ns hit timing, validating 3D-projection readout.

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We report on the design, construction, and beam test of a pilot three-dimensional projection detector based on opaque water-based liquid scintillator (oWbLS). The detector consists of an $8 \times 8 \times 16$ cm$^3$ acrylic vessel instrumented with three orthogonal planes of Kuraray Y11 multi-clad wavelength-shifting fibers read out by Hamamatsu multi-pixel photon counters. The readout electronics are based on the CITIROC front-end boards developed for the WAGASCI and SuperFGD detectors of the T2K experiment. The detector was filled with oWbLS and tested with cosmic rays and proton beams of 50, 100, 250, and 500 MeV kinetic energy at the NASA Space Radiation Laboratory at Brookhaven National Laboratory. We present three-dimensional event displays of cosmic muon and proton beam candidates, and a study of transverse light confinement via radial charge distribution measurements. The measured data show tighter light confinement than a Geant4 simulation with a 2 cm scattering length, placing the effective scattering length well below 2 cm and confirming effective optical confinement of scintillation light in the oWbLS medium. A first measurement of the hit-level timing resolution using 500 MeV proton beam data yields a single-channel timing resolution of $\sigma_t \approx 0.17$--$0.28$ ns with good photostatistics. These results demonstrate the viability of the 3D-projection oWbLS technology as a scalable, fully-active detector concept for next-generation particle physics experiments.

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physics.ins-det 2026-05-12 2 theorems

Gamma flux in LNGS Hall C averages 0.46 per cm² per second

Environmental γ-Ray Flux in Hall C at LNGS and Its Correlation with Radon Activity

Eight-site mapping shows the rate tracks radon concentration from its short-lived daughters.

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We report a comprehensive measurement of the environmental $\gamma$-ray flux in Hall C of the Gran Sasso National Laboratory. A spatial mapping of the radiation was carried out using a high-purity germanium detector mounted on a movable cart and deployed at eight locations within the hall. The detector response function and full-energy-peak efficiencies were determined through Geant4 simulations validated with calibrated $\gamma$-ray sources, with particular attention devoted to the efficiency modeling and associated systematic uncertainties. In the energy range of 57-2800 keV, the average $\gamma$-ray flux is measured to be $(\mathrm{0.46} \pm \mathrm{0.06}_{stat} \pm \mathrm{0.03}_{syst})$ $\mathrm{cm}^{-2}$ $\mathrm{s}^{-1}$. The radon level was monitored for about a month using a radon detector mounted on the same cart, and a clear correlation is observed between the environmental $\gamma$-ray rate and the ambient radon concentration, consistent with the short-lived daughters of $^{222}\mathrm{Rn}$. This result represents the first high-precision and efficiency-corrected mapping of the $\gamma$-ray flux in Hall C, substantially improving its radiological characterization and providing key input for future rare-event experiments operating in this hall.

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physics.ins-det 2026-05-11 Recognition

Geometric transforms reverse STEM scan distortions

Correction of STEM Distortions

The explicit coordinate mappings that restore true atomic positions in electron micrographs

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The manuscript considers Scanning Transmission Electron Microscopy (STEM) images and derives transformations needed to correct various distortions occurring during scanning. These transformations form the basis for the correction algorithms implemented in the CEOS Panta Rhei and TEMDM software. The manuscript is intended as a technical reference and is meant to be published only on arXiv rather than in peer-reviewed journals.

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physics.ins-det 2026-05-11 Recognition

New spectrometer records electron-particle coincidences in nuclear reaction

The ICESPICE demonstrator for particle/γ-e⁻ coincidence experiments at Florida State University

ICESPICE tests with 207Bi source and 208Pb(d,t)207Pb run show gamma-electron correlations and prompt triton-electron signals.

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The Internal Conversion Electron SPectrometer In Coincidence Experiments (ICESPICE) demonstrator has been developed at Florida State University to enable particle/gamma-electron coincidence measurements in low-energy nuclear structure studies. ICESPICE is based on the mini-orange spectrometer concept and features a modular design using commercially available permanent magnets arranged in toroidal configurations to transport internal conversion electrons to room-temperature PIPS detectors while suppressing background from undesired particles. The system was optimized through SolidWorks modeling, COMSOL magnetic field simulations, and Geant4 particle tracking to maximize the magnetic transmission probability for electrons around 1 MeV. Commissioning tests using a calibrated 207Bi source demonstrated the performance of multiple spectrometer-detector configurations. Coincidence measurements between CeBr3 detectors from the CeBrA array and PIPS detectors revealed clear gamma-electron correlations. The first in-beam particle-electron measurements using ICESPICE were performed with the Super-Enge Split-Pole Spectrograph (SE-SPS) in the 208Pb(d,t)207Pb reaction. Prompt coincidences between tritons detected with the SE-SPS and electrons detected with ICESPICE were observed. The presented results show that ICESPICE is a promising ancillary detector system for in-beam internal conversion electron spectroscopy at the FSU SE-SPS.

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physics.ins-det 2026-05-11 Recognition

GPU platform sustains zero-dead-time acquisition up to 1 GB/s

A Modular Zero-Dead-Time Data Acquisition and Real-Time GPU Processing Platform for High Throughput Physics Experiments

Phase continuity tests limit data loss below 10^{-12} while enabling real-time averaging that reduces storage needs.

abstract click to expand

High-throughput physics experiments require efficient and increasingly complex real-time processing. This paper presents a modular, software-defined platform combining high-bandwidth PCIe digitizers with consumer GPUs to achieve continuous, zero-dead-time data acquisition. Utilizing NVIDIA CUDA, the system provides a scalable pipeline for real-time fast Fourier transforms and statistical averaging. Benchmarks demonstrate that the platform can sustain continuous processing at sampling rates up to 500 MSa/s, effectively managing data throughputs of 1 GB/s. To validate the in-situ zero-dead-time architecture, end-to-end phase continuity tests were conducted, constraining fractional data loss to below $10^{-12}$. Furthermore, long-term system stability was demonstrated through an uninterrupted one-month data acquisition run. In its current deployment for the WISPLC dark matter experiment, the platform operates at 124 MSa/s with a resolution bandwidth of 0.1 Hz. This implementation enabled a significant reduction in data storage requirements using real-time spectral averaging. The callback-driven software architecture, multi-GPU workload distribution, and custom hardware shielding solutions are detailed, establishing this platform as a flexible and cost-effective alternative to traditional hardware-based pipelines.

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physics.ins-det 2026-05-11 2 theorems

CFD simulations guide dry-nitrogen flushing to protect ATLAS tracker

Characterisation of the Thermoflow due to the Dry Nitrogen Flushing Scheme in the ATLAS Inner Tracker using Computational Fluid Dynamics

Models identify flow changes that keep dew points below -60 °C when coolant drops to -55 °C

abstract click to expand

The planned High Luminosity upgrade to the Large Hadron Collider at CERN aims to increase the instantaneous luminosity peak to about 7.5 x 10^{34} cm^{-2}s^{-1}. The ATLAS detector will be extensively re-designed to meet the challenges of this upgrade. This paper focuses on the use of computational fluid dynamics to characterise the thermoflow in order to model the dry nitrogen flushing scheme in the Common Environmental Monitoring and Interlock System for the ATLAS Inner Tracker as part of the upgrade process. The Technical Design Report considers the possibility for the bi-phase CO2 coolant temperature to drop to as low as -55 degrees C in the case of a fault. The specification for the highest Relative Humidity within the ITk volume is therefore equivalent to a dew point temperature at or below -60 degrees C in order to prevent condensation which could damage the detector electronics. The design accommodates for humidity monitoring to detect the onset of such events and dry nitrogen flushing to remove moisture. Therefore, it is important to thoroughly understand all consequences of atmospheric air ingress due to air-leaks and/or air-ingress from the outlets due to the over-pressure. The computational fluid dynamics model presented in this study was used to provide quantitative and qualitative insight into the various operational and failure conditions, informing engineering design changes to optimise the flushing scheme and ensure that the ITk remains dry and within the design specification of the acceptable dew point range.

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physics.ins-det 2026-05-11 2 theorems

AstroPix-v3 images EM showers and separates them from hadrons at 68% efficiency

Test-Beam Performance of the AstroPix Silicon Sensor for Imaging Calorimetry

Interleaved pixel layers in lead-scintillating-fiber modules record broader hit patterns for electrons than pions in few-GeV beams.

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AstroPix is a high-voltage CMOS HVCMOS monolithic active pixel sensor MAPS developed for future space-based gamma-ray missions. It is also a candidate technology for the imaging layer of the Barrel Imaging Calorimeter BIC in the ePIC experiment at the future Electron-Ion Collider EIC. We report the first AstroPix test-beam results obtained at the KEK Photon Factory Advanced Ring PF-AR and the CERN Proton Synchrotron PS T10 beam line in 2025, using the third prototype AstroPix-v3. AstroPix-v3 sensors were operated as both standalone tracking layers and imaging layers interleaved with prototype lead/scintillating-fiber Pb/SciFi calorimeter modules, using electron and hadron beams in the few-GeV/c momentum range. Event synchronization between the continuous readout of AstroPix-v3 and the trigger-based readout of the Pb/SciFi calorimeter was achieved using a common timestamp. The AstroPix-v3 sensors exhibit stable performance, reaching a maximum hit efficiency of 68 percent at a bias voltage of -400 V under pion-dominated beam conditions. When combined with the Pb/SciFi calorimeter, the AstroPix layers successfully capture the development of electromagnetic showers. Using Cherenkov-based particle identification, electron-induced events exhibit significantly higher hit multiplicities and broader spatial distributions than pion-induced events, thereby providing clear discrimination between electromagnetic and hadronic showers. These results demonstrate that AstroPix-v3 provides effective, high-granularity imaging of shower development and is well suited as an imaging layer in future calorimeter systems for both collider and space-based experiments.

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physics.ins-det 2026-05-11 2 theorems

Optimized phonon collectors raise CRESST sensor performance

Optimisation of TES design for the CRESST experiment

Changes to thickness, size, and material in W-TES devices improve signal quality for sub-GeV dark matter searches.

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The CRESST experiment aims at the direct detection of sub-GeV dark matter particles via elastic scattering off nuclei in different target crystals at cryogenic temperatures. The advancement in W-TES sensors allowed the CRESST detectors to reach energy thresholds of 10 eV and lower, opening the way to the exploration of dark matter masses as low as 70 MeV/c2. This work presents optimisation studies of W-TESs aimed at further improving the signal-to-noise ratio and overall detector performance. In particular, we investigate the thickness, dimensions and material composition of phonon collectors and assess their impact on detector response. The results demonstrate a significant performance enhancement and establish new benchmarks for the sensors used within CRESST.

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physics.ins-det 2026-05-11 Recognition

ATLAS track reconstruction stays efficient with 80 pile-up collisions

Track and Vertex Reconstruction with the ATLAS Inner Detector

Run 2 and Run 3 studies confirm good resolution and low fake rates for tracks and vertices even at highest overlap.

abstract click to expand

Charged-particle reconstruction is a fundamental part of the event reconstruction in modern multi-purpose high-energy physics detectors. This paper describes the algorithms used to reconstruct charged particles and primary vertices with the ATLAS Inner Detector. The most recent software configuration deployed for data-taking is described, and the performance obtained when this software is used to process Run 2 (2015-2018) data, a subset (from 2022) of Run 3 (2022-2026) data, and corresponding simulated data is presented. The ATLAS track and vertex reconstruction performance is shown for up to 80 simultaneous proton-proton interaction. It maintains a high efficiency, good resolution for key parameters, and low rates of mis-reconstructed candidates for Run 2 and Run 3 conditions.

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physics.ins-det 2026-05-11 2 theorems

SiC sensors reveal RF-modulated micro-spills in medical accelerator beams

Measurements of the micro-spill structure of medical cyclotron and synchrotron beams and its impact on pulse pileup

Sub-nanosecond arrival times tied to accelerator frequencies enable quantitative pileup estimates for detector design

abstract click to expand

Detector characterization and instrumentation testing are often performed at cyclotron and synchrotron facilities, many of which were originally developed for medical applications in cancer therapy. For particle physics experiments requiring a single-particle resolution, pileup can significantly degrade data quality, making precise knowledge of the beam time structure essential for selecting appropriate readout parameters. However, such information is often unavailable from the facilities and challenging to determine experimentally. Here, we report measurements of the spill time structure at two medical accelerator facilities using a silicon carbide (SiC) particle sensor coupled to a high-frequency readout system. Owing to its high carrier saturation velocity and the tolerance to large bias voltages, SiC is well suited for fast readout and measurements requiring precise timing. Using a 6 GHz readout with custom SiC diodes, we characterize the micro-spill structure of both cyclotron and synchrotron beams on a sub-nanosecond timescale. The measured arrival-time distributions exhibit modulation with the accelerator RF frequencies, reflecting features of the extraction process. The resolved micro-spill structure enables quantitative estimation of pileup contributions and provides design constraints for future readout electronics. The presented results emphasize the importance of the characterization of the beam time-structure characterization for the development of precise readout systems.

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physics.ins-det 2026-05-11 2 theorems

TES detectors reach 86% efficiency with dark counts below 6 mHz

Characterization of a Two-Channel Optical and Near-infrared Transition Edge Sensor System for Rare-Event Searches

Energy resolution lets the system register 1064 nm signals at rates of 2.7e-5 Hz within 20 days at 5 sigma .

abstract click to expand

Transition edge sensors (TESs) are superconducting energy-resolving microcalorimeters that have demonstrated low background rates as well as quantum efficiencies close to unity for photons at optical and near-infrared wavelengths. This makes these detectors well suited for rare-event searches. We report on the comprehensive characterization of a two-channel detector module consisting of two tungsten TESs optimized for the detection of photons with a wavelength of 1064nm. The devices achieve a system detection efficiency of $(86\pm1)$%, an energy resolution better than 7%, and a background dark-count rate of photon-like events below 6mHz when coupled to an optical fiber. Using an unbinned likelihood framework, we find the dark count rate to be compatible with blackbody radiation from the room-temperature laboratory environment. Thanks to the energy resolution of the TESs, we show that it is possible to detect monochromatic signals at 1064nm with photon rates $\geqslant 2.7_{-0.6}^{+0.8} \times10^{-5}$Hz, which corresponds to a power of $\geqslant(5.0_{-1.1}^{+1.4})\times10^{-24}$W, within 20 days of measurement time at the 5$\sigma$ confidence level. This makes our detectors well suited for searches for hypothetical axions and axion-like particles with experiments such as the Any Light Particle Search II (ALPS II) or axion interferometers. The developed methodologies are not only applicable to axion searches, but are also relevant for rare-event searches with TESs in general.

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physics.ins-det 2026-05-11 2 theorems

Racetrack electrode design yields 50 ps timing in silicon sensor

Design and Characterization of Racetrack 3D-Trench Silicon Sensor Based on 8-Inch Process with Excellent Time Resolution

Continuous trenches remove field saddle points, enabling scalable 4D tracking for high-radiation environments.

abstract click to expand

In the extreme environments of high-luminosity colliders, traditional planar silicon sensors suffer severe radiation-induced performance degradation and fail to satisfy the stringent demands of high-precision tracking and high-speed timing in particle physics. 3D silicon sensors enhance radiation hardness by shortening charge collection distance, yet conventional designs with columnar or square-cell trench electrodes exhibit non-uniform electric fields, including saddle points and low-field regions, which degrade charge collection efficiency and timing resolution. This work presents a novel racetrack 3D-trench silicon sensor with continuous racetrack electrodes surrounding a long central collection electrode, aiming to eliminate electric field inhomogeneities. For the first time, a 23 $\mu $m shallow-etched device was fabricated on an 8-inch platform, which provides a promising basis for its subsequent mass production and engineering applications. The device performance was systematically evaluated through theoretical analysis, 3D TCAD simulations, and characterization using semiconductor parameter analyzers and transient current technique (TCT) measurements. The sensor achieves leakage current below 0.2 nA, breakdown voltage above 110 V, full depletion voltage as low as a few volts, capacitance as low as 650 fF, collected charge of 4 fC, time response of about 640 ps, and time resolution of 50 ps. This large-scale manufacturable, shallow-etched racetrack 3D-trench silicon sensor provides a competitive device solution for portable radiation detection and next-generation 4D tracking under high-radiation and high-event-rate conditions.

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physics.ins-det 2026-05-11 Recognition

GeSi SPADs reach room temperature for SWIR single-photon detection

Review of germanium-silicon single-photon avalanche diodes

Review follows progress from 2011 cryogenic start to 2024 uncooled operation, opening practical sensing applications.

abstract click to expand

While it took about a decade for a germanium (Ge) thin film grown on a silicon (Si) substrate to be successfully applied as a detector material for high-speed optical fiber communication application, it took about another decade to further expand its usage as a sensor material for active optical sensing and imaging applications. In this paper, we shall review the progress of a shortwave infrared (SWIR) single-photon detection (SPD) with germanium-silicon (GeSi) single-photon avalanche diode (SPAD), ranging from the first demonstration at cryogenic temperature (Z. Lu et al., 2011) to the recent demonstration at room temperature (N. Na et al, 2024). Potential new applications will also be discussed.

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physics.ins-det 2026-05-08 2 theorems

Gradient stopping at boundaries gives stable derivatives for detector design

Exploring the Boundaries of Differentiable Radiation Transport and Detector Simulation

Halting flow through unstable material crossings in particle transport produces usable gradients without altering the simulation itself.

abstract click to expand

We present an application of automatic differentiation for particle transport through matter using a Geant4-like radiation transport simulation with a full electromagnetic physics model. When differentiating this step-based transport, we observe exploding gradients driven by rare but extreme sensitivities at material boundaries, which propagate through subsequent transport and shower development. To obtain usable derivatives for optimization, we introduce a targeted mitigation strategy that stops gradient propagation through boundary-crossing operations under identifiable unstable conditions while leaving the forward (primal) simulation unchanged. We demonstrate that this enables stable, optimization-ready gradients in a detector-design problem.

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physics.ins-det 2026-05-08 Recognition

Impurity relaxation makes sapphire resonator frequency rate-dependent

Dynamic thermal sensitivity of microwave cryogenic sapphire resonator

A memory effect from Cr3+ produces a stability bump at 10 s averaging times in cryogenic sapphire oscillators.

abstract click to expand

We have discovered a memory effect in the temperature sensitivity of a cryogenic sapphire microwave resonator, at the heart of the ultra-stable Cryogenic Sapphire Oscillators (CSOs). Such effect is due to the relaxaxtion time of Cr3+ impurities, and results in hysteresis in the frequency vs temperature behavior, These paramagnetic impurities, always present in synthetic sapphire, produce a temperature turning point which is necessary to achieve ultimate frequency stability. The practical implication on the CSO is that the sapphire resonators's frequency depends on the rate of temperature change. This dynamical thermal sensitivity results in a wide bump in the Allan deviation at 10 s integration time, where the frequency stability is degraded. The actual degradation depends on the specie and on the amount of the dominant paramagnetic impurity.

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physics.ins-det 2026-05-08

Timepix network maps neutron and hadron backgrounds at MoEDAL

Analysis of Mixed Radiation Fields at the MoEDAL Experiment Based on Real-Time Data from a Timepix Detector Network

Real-time pixel data reveals fluences and directions of particles that can mimic monopole tracks in passive detectors.

abstract click to expand

The primary objective of this work is the determination of fluences and characteristics of fast neutrons, other hadrons, and highly ionizing particles in the environment of the MoEDAL experiment at the Large Hadron Collider. These particles constitute an experimental background for the passive Nuclear Track Detectors (NTDs) used by MoEDAL to search for tracks potentially produced by Dirac magnetic monopoles, in particular by particles indistinguishable in NTD from monopoles. The study is based on data acquired by the Timepix hybrid silicon pixel detector network, which represents the first and only active detector system installed and operated as part of the MoEDAL experiment from 2013 to 2018. The Timepix detector network enables real-time measurements of mixed radiation fields, including the composition, spectral properties, and directional characteristics of individual radiation components across different regions of the MoEDAL experimental area. The paper presents detailed results of the radiation field analysis with emphasis on neutrons and highly ionizing particles, including their directional distributions. The first results demonstrating the spatial tracking capabilities of the Timepix detectors are also reported, illustrating the reconstruction of particle direction and energy-loss profiles from individual detector frames.

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physics.ins-det 2026-05-07

NDR bias raises HEB mixer conversion gain

Hot-electron bolometric mixer with negative differential resistance

Circuit redesign damps oscillations and enables stable higher-gain operation at 2.5 THz.

abstract click to expand

We demonstrate that the conversion gain of a superconducting hot-electron bolometer (HEB) mixer can be increased by biasing the device within the negative differential resistance (NDR) region of its current-voltage characteristic. Although NDR biasing has historically been avoided due to MHz-range resistive oscillations, we show that these oscillations arise from an LC resonance formed by the bias-T inductance and the effective thermal capacitance of the HEB. By applying stability criteria analogous to those developed for tunnel diodes, we redesigned the embedding circuit to suppress this resonance and achieve stable NDR operation. Direct measurements using two monochromatic 2.5-THz sources confirm the predicted gain enhancement. These results establish NDR biasing as a viable method for improving HEB mixer performance and motivate further studies of noise behavior and circuit optimization.

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physics.ins-det 2026-05-07

Sidewall implant and microwave anneal reduce sensor edge leakage

Active Edge Silicon Sensors Fabricated With Edge Ion Implantation and Microwave Annealing for Dopant Activation

Simplified doping technique tested on silicon devices shows lower current at the edges, supporting compact active-edge detectors.

abstract click to expand

Silicon detectors typically require an insensitive area around their periphery to accommodate guard rings, which help maintain the electric field uniformity around edge pixels and isolate the high leakage current from the physical edges of the detector. Minimization of this insensitive region is desirable for applications in high-energy physics, X-ray experiments, and medical imaging. Existing active edge technology offers a solution for reduction or total elimination of the insensitive region, via a continuation of the highly doped backside up the sidewalls of the device. However, current methods for realizing this technology are complex and expensive. We propose a new technique that simplifies the fabrication of highly doped edges using side ion implantation and microwave annealing. Tests demonstrating the feasibility of this proposed process were performed on a set of sensors, and current versus bias voltage measurements probing the edge effects were performed before and after the edge implantation and annealing. To aid in interpretation of the results, TCAD simulations of the test devices were performed. Significant improvement in the edge leakage current is observed, indicating the promise of this simplified process for fabrication of active edge sensors.

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physics.ins-det 2026-05-07

Simulations match ATLAS pixel degradation after 2e15 n-eq/cm2 fluence

Study of Particle Fluence Effects on Collected Charge and Depletion Voltage of the ATLAS IBL Planar Pixel Sensors

Bias scans over ten years show charge loss and rising depletion voltage follow TCAD and Monte Carlo predictions that include radiation-dam

abstract click to expand

After ten years of operation at the LHC, the planar pixel sensors of the innermost barrel layer of the ATLAS Pixel detector have accumulated an average bulk damage fluence in excess of $2\times10^{15}$ 1 MeV-neutrons equivalent/cm$^2$. The macroscopic effects of this radiation are an increase of the sensor leakage current, a loss of charge collection efficiency and an increase of the depletion voltage. Using regular bias voltage scans performed at the beginning and end of each data taking campaign the evolution of the pixel cluster charge and bulk depletion is studied as a function of particle fluence. Results are interpreted with the modelling provided by standalone TCAD and ATLAS Monte Carlo simulation including radiation damage effects. The dependence of the collected charge and the depletion voltage with integrated luminosity are studied through the full period of operation.

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physics.ins-det 2026-05-07

ML infers nuclear test yields from gamma spectra with 95% accuracy

Machine learning inference of fission yields from gamma spectroscopy for very low-yield nuclear test verification

Models trained on 66 million simulations classify yields near 1 kg TNT and estimate them with 12.4 percent error from measurements taken a 1

abstract click to expand

Very low-yield nuclear tests pose a major verification challenge for the zero-yield standard of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The zero-yield standard prohibits any explosive experiment that produces a self-sustaining fission chain reaction while allowing subcritical experiments. Previous research shows that on-site gamma spectroscopy of post-test debris provides useful insight into the criticality level, although it remains heavily dependent on knowledge of certain experimental settings. Here, we adopt a new approach whereby machine learning models are trained on simulated gamma spectroscopy data to infer the fission yield of a nuclear very low-yield test. Using high-fidelity 3D Monte Carlo particle transport simulations, we generated gamma spectra measured outside containment vessels after very low-yield tests for 66 million representative scenarios. From these spectra, we extracted 82 fission-product-to-plutonium-239 peak ratios, then trained ML models for two tasks: (1) binary classification of whether a test exceeded a chosen yield threshold, and (2) regression to estimate the actual yield. We find that XGBoost performs best on the classification task across the most policy-relevant yield range. The classifier achieves high accuracy even for yields near the chosen threshold (e.g., >95% for yields +-100 g around a threshold at 1 kg TNT), and the regressor presents a mean absolute relative error of 12.4% for measurements taken a month to a year after the test. These results demonstrate that using machine learning to infer the yield of a past very low-yield nuclear test from gamma spectroscopy data is feasible and accurate. This approach can support efforts to establish a robust verification protocol for the zero-yield standard and could pave the way for a future yield threshold-based verification regime that is both technically feasible and politically viable.

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physics.ins-det 2026-05-07

SiC detector keeps over 90% CCE after 1 MGy 160 keV X-ray dose

Stability of Charge Collection Efficiency in a Novel Graphene-Optimized Silicon Carbide Detector Under 160 keV X-Ray Irradiation

Leakage and rise time change only modestly, with no sign of displacement damage in the semiconductor bulk.

abstract click to expand

A novel graphene-optimized silicon carbide PIN detector was fabricated. Its electrical properties, charge collection performance and signal rise time were evaluated under non-irradiated conditions and under X-ray irradiation with an energy of 160 keV at doses of 0.1 MGy and 1 MGy. The leakage currents of the detectors under non-irradiated, 0.1 MGy, and 1 MGy irradiation conditions are approximately 1.45e-10 A, 1.51e-10 A, and 1.57e-10 A, respectively. The effective doping concentration of the detector is approximately 8.08e13 cm^-3 before and after irradiation, with no significant change. The rise times of the signals from alpha particles signal detected by the detector under unirradiated, 0.1 MGy, and 1 MGy X-ray irradiation conditions are 336 ps, 368 ps, and 387 ps, respectively. The rise times of the beta particles signal detected by the detector under unirradiated, 0.1 MGy, and 1 MGy X-ray irradiation conditions are 342 ps, 375 ps, and 398 ps, respectively. After 0.1 MGy and 1 MGy X-ray irradiation, the charge collection efficiencies (CCEs) of the detector for alpha particles are 97.2% and 90.0%, respectively; for beta particles, they are 100.0% and 97.0%, respectively. Experiments confirm that 160 keV X-ray irradiation may not cause significant displacement damage in the 4H-SiC, and the minor performance degradation may be attributed to ionization induced changes in the graphene electrode. The detector exhibits excellent charge collection performance and fast time response. These results demonstrate stable performance under extreme X-ray exposure, highlighting the detector's potential for radiation-hard applications in high-energy physics, space missions, and nuclear reactor monitoring.

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physics.ins-det 2026-05-06

Compact cavity achieves sub-femtometer displacement sensing

Demonstration of a compact optical resonator-based displacement sensing technique with sub-femtometer precision

Heterodyne tracking of a proof-mass cavity reaches 1 fm/√Hz above 8 Hz and spans ten orders of magnitude in range.

abstract click to expand

We demonstrate sub-femtometer displacement-sensing results achieved with a compact optical resonator-based laser interferometry technique called heterodyne cavity-tracking, intended for local displacement or inertial sensing with ultra-high sensitivity. Displacement sensing at this sensitivity is required for ambitious improvements to current gravitational-wave detectors and to enable future ground- and space-based observatories. The optical topology employs a centimeter-scale dynamic cavity incorporating a proof mass, and the relative length fluctuations of this cavity are measured using a heterodyne readout. The fundamental limits of the technique lie significantly below the femtometer level and are ultimately defined by the coating thermal noise of the cavity mirrors. In our experimental demonstration, we achieve a sub-femtometer per Hz$^{1/2}$ displacement sensitivity for Fourier frequencies above 8 Hz and a sub-picometer per Hz$^{1/2}$ sensitivity above 3 mHz, with the sensitivity at lower frequencies limited by mechanical and temperature-induced noise sources. When the length of the dynamic cavity was intentionally actuated, the technique could track a maximum motion of about 0.6 $\mu$m, thereby achieving a dynamic range of roughly ten orders of magnitude in displacement sensing. We thus demonstrate the key features of this scheme - sub-femtometer performance and a dynamic range spanning ten orders of magnitude - in a laboratory setting, paving the way for development of an integrated system. Such a system is a currently unrealized technology that is necessary for precision physics experiments in the coming decades.

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physics.ins-det 2026-05-05

The paper describes the design

Characterisation and Monte Carlo validation of a compact AmBe neutron irradiation facility providing fast and thermal neutron fields for detector development

A compact AmBe-based neutron irradiation facility with moderator was designed, commissioned, and validated via FLUKA simulations…

abstract click to expand

We report the design, commissioning and benchmarking of a compact AmBe-based neutron irradiation facility capable of providing both fast and thermal neutron dominated fields through multiple detector positions within a moderator assembly. Detailed radiation transport simulations using the FLUKA Monte Carlo code were performed to model the radiation environment at different detector positions. The inclusion of a single-crystal CVD diamond neutron detector in the simulations enabled direct comparison with experimental measurements, providing confidence the radiation fields are well understood. The simulations also provided a detailed breakdown of energy deposition mechanisms in the diamond sensors, including nuclear recoil, neutron capture reactions and secondary proton production from surrounding materials, highlighting the influence of detector housing materials on the local radiation environment and detector response. The facility provides a practical and accessible platform for neutron detector development and benchmarking in typical university laboratories, with dose rates outside the facility below typical natural background levels.

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physics.ins-det 2026-05-05

FPGA prototype reconstructs tracks on live LHCb data

A real-time demonstrator of track reconstruction with FPGAs at LHCb

Demonstrator runs at 30 MHz using optical-linked cards and stays synced with alignment constants during physics runs.

abstract click to expand

The upgraded LHCb detector has started its Run 3 of data taking in 2022, with a completely overhauled DAQ system, reading out and processing the full detector data at every LHC bunch crossing (30 MHz average rate). At the same time, an intense R&D activity is taking place, with the aim of further improving the real-time data processing performance of LHCb, in view of "Upgrade II", where luminosity will be increased. In this work, we describe the experience gained with a prototype device for a 30 MHz real-time tracking in the LHCb VELO detector, implemented in state-of-art PCIe-hosted FPGA cards interconnected by fast optical links. The system has been processing live LHCb data opportunistically during physics data taking, thanks to a dedicated TestBed facility fed by the experiment monitoring system. We describe, amongst other things, the system used to organise and optimise the high-speed distribution of data to the components, and the synchronisation with the most updated alignment constants to be used in track reconstruction.

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physics.ins-det 2026-05-05 Recognition

Analytical model gives temperature-dependent inelastic neutron scattering law

Temperature-Dependent Neutron Moderation Model Including Inelastic Scattering in Reactor Media

Formulas for flux density and moderation spectra in reactor cores now include medium temperature via gas-model kinematics.

abstract click to expand

In this study, a mathematical model of neutron moderation is developed that accounts for the temperature of the fissile medium and the contribution of inelastic neutron scattering on heavy nuclei of uranium 238 in reactor cores. Within the gas model framework, an analytical expression for the inelastic neutron scattering law for an isotropic neutron source is derived for the first time, incorporating the temperature of the moderating medium as a parameter. The scattering law is obtained from the general kinematic solution of inelastic neutron nucleus interactions in the laboratory system, where both particles possess arbitrary velocity vectors. Based on the newly derived inelastic and previously obtained elastic scattering laws, analytical formulas for the neutron flux density and moderation spectrum are presented, both of them dependents on the medium temperature. The calculated deceleration spectra exhibit two distinct maxima (a high energy and a low energy peaks). The low energy maximum is consistent with the analytical solution of the neutron balance equation, confirming the validity of the proposed model. The developed approach provides a deeper understanding of neutron energy distribution in temperature dependent reactor media and can be applied to improve the accuracy of neutron kinetic calculations in thermal and fast reactor systems.

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physics.ins-det 2026-05-04 1 theorem

Single positron sustains quantum cyclotron in Penning trap

One-Positron Quantum Cyclotron

The indefinite suspension enables higher-precision magnetic moment measurements and CPT tests against the electron.

abstract click to expand

A one-positron quantum cyclotron is realized with a single positron suspended indefinitely in the magnetic field of a Penning trap. This opens the way to quantum measurements of the positron magnetic moment, to a precision much higher than attained with classical cyclotron motion. Comparing the magnetic moments measured using positron and electron quantum cyclotrons should provide the most stringent test of the fundamental CPT invariance of the Standard Model of particle physics in the lepton sector.

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physics.ins-det 2026-05-04

Optimal drive sets new limits for nanomechanical radiation sensors

Detectivity and bandwidth limits of cooled and uncooled light detection using nanomechanical resonators

Model shows best amplitude differs from nonlinearity threshold, enabling universal bounds for cooled and uncooled detectors

abstract click to expand

Nanomechanical resonators (NMRs) offer a promising alternative to traditional thermal-based radiation detectors due to their immunity to electrical noise. In recent years, these sensors have reached the previously unattained theoretical detectivity limit set by the fluctuation noise of thermal photons at room temperature. Beyond this point, improvements of NMR resonators do not translate into greater detectivity, but in greater effective bandwidth. There is, however, no simple model predicting the limits of this bandwidth enhancement. Likewise, models predicting the performances of NMR-based radiation sensors under active cooling have not been derived. To address these gaps in knowledge, a key missing ingredient consists of defining the NMR optimal driven amplitude that minimizes additive frequency noise, but without performance degradation from nonlinear phenomena. We find that, in the context of NMR-based radiation sensing, this optimal amplitude ($a_\mathrm{opt}$) is dramatically different than the commonly assumed critical amplitude ($a_\mathrm{c}$) that defines the onset of non-linear phenomena in nanomechanical resonators. Our proposed model for this optimal amplitude allows us to quantify the maximum bandwidth enhancement in NMR-based radiation sensors. We also derive simple equations predicting the maximum detectivity in cryogenically cooled sensors. Finally, combining these two models allows us to define new universal performance limits. This unveils important general conclusions on the ideal geometry of NMR radiation sensors. We find that thermomechanically-limited sensors should be as thin and extended as possible. In contrast, readout-limited sensors should also be thin, but should be just large enough to make radiation heat transfer dominant compared to conduction.

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physics.ins-det 2026-05-04 2 theorems

N-BEATS predicts KATRIN tritium source recovery time

Forecasting Source Stability in Scientific Experiments using Temporal Learning Models: A Case Study from Tritium Monitoring

Deep learning on sparse beta X-ray data enables scheduling during stabilization periods in neutrino mass measurements.

abstract click to expand

The Karlsruhe Tritium Neutrino Experiment (KATRIN) aims to measure the absolute neutrino mass with unprecedented sensitivity, requiring precise monitoring of the windowless gaseous tritium source, where tritium beta decay occurs. To track variations of the source activity, beta-induced X-ray spectroscopy provides real-time diagnostics. However, traditional drift detection methods struggle with the infrequent and transient nature of instability events in gaseous tritium. This study bridges the gap between state-of-the-art time-series forecasting models and real-world experimental applications by leveraging deep learning to predict the time to stability after instabilities. Unlike standard benchmarking approaches that emphasize algorithmic performance on fixed datasets, we apply forecasting models -- including LSTM, N-BEATS, TFT, NHITS, DLinear, NLinear, TSMixer, and Chronos-LLM -- to complex, large-scale experimental data. Our findings highlight two challenges: learning from sparse instability events and forecasting long time horizons (i.e., predicting hundreds of future points), both of which are ongoing challenges in time-series forecasting and remain active areas of research. This prediction task has direct experimental value by enabling better scheduling and maintenance planning. A reliable forecast of stability time allows for more efficient measurement and task management during stabilization periods. Through model selection, we identified N-BEATS as the top performer, excelling in accuracy and repeatability, demonstrating that deep learning can optimize large-scale physics experiments.

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physics.ins-det 2026-05-04

Researchers optimized the geometry and readout circuit of qPlus sensors for atomic force…

Optimization of qPlus sensor geometry and circuit for high-speed atomic force microscopy in liquid environments

A redesigned qPlus sensor reaches 9.3 fm Hz^{-1/2} displacement noise (one-third of conventional values), halves the minimum detectable…

abstract click to expand

Atomic force microscopy (AFM) using qPlus sensors is a powerful tool for high-resolution analysis in various liquids, including high-viscosity or opaque environments. However, the relatively high displacement sensor noise density (n_{ds}), combined with the high spring constant and the low resonance frequency, limits force sensitivity and has hindered high-speed imaging. In this paper, we clarify the dominant factors governing n_{ds} and the minimum detectable force gradient (F'_{min}) through a comprehensive analysis of sensor geometry and circuit theory. Based on these findings, we developed a low-noise qPlus sensor that achieves an n_{ds} of 9.3 fm Hz^{-1/2}, which is approximately one-third that of conventional sensors, and reduces F'_{min} by half. Using this sensor, we demonstrated high-speed, atomic-resolution imaging of a molten gallium interface at a frame rate of 6.6 s frame^{-1} (39 lines s^{-1}), proving its advantage for analyzing fast interfacial dynamics in liquid environments.

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physics.ins-det 2026-05-04

Command-line tool lets agents reduce SANS data by natural language

EQSANS-CLI: A natural-language, agent-ready command-line tool for small-angle neutron scattering data reduction at EQ-SANS

A working table and shared handler turn the full reduction pipeline into commands an external agent can drive from a phone with one skill

abstract click to expand

Small-angle neutron scattering (SANS) data reduction at user facilities follows a largely repetitive workflow. Runs are first classified in the catalog and matched to transmission, background, and empty-beam references within the same instrument configuration. The data are then reduced, placed on an absolute scale using a standard, and stitched across configurations. Although these steps are individually well understood, they remain weakly connected, producing a coordination burden that scales with the number of runs and configurations. This paper describes EQSANS-CLI, a command-line tool that organizes this workflow into a coherent, scriptable, and agent-addressable system. The design rests on four principles: a shared command-handler layer that all input paths converge on; a persistent \emph{working table} that holds every reduction decision as editable rows; two input surfaces (an interactive terminal and a headless JSON mode) that compile to the same handler entry point; and a status-driven re-reduction model that treats parameter changes as first-class events. An \texttt{/autopilot} command chains the full pipeline from the IPTS number to stitched $I(Q)$ curves in one invocation. A Slack bot demonstrates that the headless interface, together with a single skill document loaded into an external agent's system prompt, is sufficient to drive complete reductions by natural language from a mobile device. The architecture is intentionally minimal on the agent side: the CLI is the authoritative executor, and the agent's only job is to translate human intent into commands on a stable contract.

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physics.ins-det 2026-05-01

ML improves SiW-ECAL photon resolution by 20 percent at low energies

Optimisation of a silicon-tungsten electromagnetic calorimeter energy response to photons

The gains also correct high-energy leakage and enable a reoptimized design for future circular collider detectors

abstract click to expand

An innovative path for the detectors at future colliders to achieve higher performances is to use a Particle Flow approach, which requires highly granular calorimeters to image individual showers. The silicon-tungsten electromagnetic calorimeter (SiW-ECAL) aims at fulfilling all the expected physical and technical requirements. SiW-ECAL has been developed by the CALICE and ILD collaborations for more than two decades and is now reaching maturity, for linear machines. However, with the tendency towards circular machines, the progress of electronics and the rapid advancement of machine learning (ML) techniques, the SiW-ECAL design needs to be reoptimised to enhance its performance. This study develops ML-based reconstruction approaches for SiW-ECAL, achieving an approximate 20% improvement in energy resolution in the low-energy range and effectively correcting energy leakage in the high-energy range. Subsequently, the SiW-ECAL design is reoptimized based on this method.

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physics.ins-det 2026-05-01 1 theorem

Stronger fields improve LAS angle resolution while cutting acceptance

Ion-Optical Tuning of the Large Acceptance Spectrometer for Improved Angular Resolution and Acceptance

Simulations show resolution reaches 5.5 mrad at +20% field but with reduced solid angle.

abstract click to expand

The trade-off between angular resolution and acceptance in scattering-angle measurements with a magnetic spectrometer is quantitatively evaluated for the Large Acceptance Spectrometer (LAS). The dependence on the multipole magnet field strength is investigated. Third-order transfer matrices were calculated with GICOSY, and particle transport was simulated with MOCADI. The vertical angular resolution is defined as the standard deviation between reconstructed and true angles, while the acceptance is determined from the transport efficiency within an elliptical gate in target angle space. The resolution improves with increasing field strength, reaching $\sigma_b \sim 5.5$ mrad at +20\%, consistent with $5.43 \pm 0.20$ mrad. In contrast, stronger fields reduce the vertical acceptance and solid angle. These results demonstrate a trade-off between resolution and acceptance. Enhanced vertical focusing shifts the focal condition away from the nominal focal plane, enabling high-precision reconstruction.

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physics.ins-det 2026-05-01

Glass GEMs spread avalanche light to neighboring holes

Optical effects in Gaseous Electron Multipliers (GEMs)

This optical effect boosts track intensity and width by as much as 26% and 31% in simulations, explaining MIGDAL observations

abstract click to expand

Optical time projection chambers (OTPCs) are well suited for applications that require the highest spatial resolution for particle track reconstruction. The MIGDAL experiment uses a glass GEM-based OTPC and observes a systematic excess in both the intensity and width of particle tracks in its optical readout, when compared with charge readout simulations. One hypothesis is that scintillation light produced inside a GEM hole during the avalanche propagates through the GEM substrate and exits neighboring holes. We present lab measurements testing this hypothesized optical broadening effect in three types of GEM substrates: glass, ceramic, and FR4. Our observations quantify this optical broadening and demonstrate it to be strongest in glass GEMs. Additionally, we use Geant4 simulations to both reproduce our observations and quantify optical broadening effects in realistic charge avalanches. Applying our glass GEM effects to simulated particle tracks yields increases of track intensity and widths by up to around 26% and 31%, respectively. This may explain the larger than expected intensity and track widths observed in the MIGDAL OTPC and is expected to be an observed effect in all GEM-based OTPCs.

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physics.ins-det 2026-04-30

Six isotope gases open route to kiloton-scale 0νββ TPCs

Gaseous forms of ⁷⁶Ge, ⁸²Se, ⁹⁶Zr, ¹⁰⁰Mo, ¹²⁴Sn, and ¹³⁰Te: new avenues to future 0νββ time projection chambers

Electropositive compounds support electron drift and gas gain, allowing mature TPC readouts in 100-ton detectors without xenon limits.

abstract click to expand

Searches for neutrinoless double beta decay are growing larger, with tonne-scale targets in several nuclides still far from exhausting the discovery space. What's beyond ton scale? Time projection chambers (TPCs) are one option for building large (100~T or kiloton-scale) instruments, but filling them with the familiar $^{136}$Xe for a $0\nu\beta\beta$ search is a problem: xenon is a scarce element whose atmospheric-extraction supply chain is small and hard to grow. If future $0\nu\beta\beta$ searches wish to exploit TPCs' known hardware scalability, we need to fill them with non-xenon target materials. Of particular value would be a TPC that can drift electrons, rather than ions, letting us use mature readout schemes which require gas gain. In this paper, we identify a set of previously-unappreciated, affordable gases which are likely to be electropositive, allowing electron drift and gain in gas-phase TPCs sensitive to $0\nu\beta\beta$ with the help of track-topology background rejection. We identify candidate $^{76}$Ge, $^{82}$Se, $^{96}$Zr, $^{100}$Mo, $^{124}$Sn, and $^{130}$Te compounds suitable for gas-phase electron-drift TPCs; some may be suitable for liquid-phase TPCs as well. Using a figure-of-merit that emphasizes the need for track topology for background rejection, we argue that 100~T and kiloton-scale gas TPCs are realistic without unprecedented underground infrastructure.

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physics.ins-det 2026-04-30

Tests validate CMS Phase-2 pixel modules for HL-LHC

Comprehensive Design Validation of serially powered CMS Phase-2 Pixel Modules

Prototype qualification and thermal stress results confirm bump-bond strength and prompt HDI adjustments.

abstract click to expand

After the Large Hadron Collider (LHC) upgrade into High Luminosity LHC (HL-LHC), the instantaneous luminosity is expected to reach values up to 7.5x10^34cm^2/s, causing a harsher radiation environment as well as a significant increase in data rate. The current CMS Tracker detector would not be able to operate under these conditions and it will be replaced by an upgraded version known as Phase-2. In view of the detector upgrade and as part of the design validation process, a Quality Control (QC) test flow has been developed to characterize the first pixel modules prototypes and evaluate their performance. The results of this procedure were the starting point for small design adjustments, especially for the the High Density Interconnect or HDI, the flexible low mass PCB that distributes power and signals to the module and controls the readout through a high speed data transmission channel. This talk includes qualification tests performed on the CMS Phase-2 design to ensure that all the pixel module components satisfy the upgrade specifications, for example in terms of power consumption and leakage current stability. Additionally, stress tests were conducted to probe the limits of the design, demonstrating the robustness and endurance of the module layout. Due to the differing material properties of the HDI copper layers and the silicon sensor and readout chip, temperature gradients induce different thermal expansion and contraction, resulting in mechanical stress on the bump-bond interface. For this reason, among the destructive measurements, dedicated thermal stress tests were carried out to evaluate the bump-bond strength and durability for different bump bonding techniques.

0

physics.ins-det 2026-04-30

Superconducting amp reaches 30 dB gain with 1.2 half-quanta noise

A cm-wave quantum noise limited resonant superconducting parametric amplifier

Resonant CSRR device at 400 mK shows four K-band resonances and near-quantum performance for dark matter searches.

abstract click to expand

Superconducting Parametric Amplifiers (SPAs) have seen great interest in recent years due to their high gain and quantum limited noise performance. Among these amplifiers, resonant SPAs have been widely developed for experiments where ultra low-noise narrow-band amplification is of interest, such as the search for Axion dark matter in particle physics and the detection of spectroscopic lines in astrophysics, while also finding applications in quantum computing. This work presents an amplifier based on a Complementary Split Ring Resonator (CSRR), patterned on a NbTi coated sapphire substrate embedded within a waveguide, designed to work at a set of four narrow frequency bands throughout K band (18-27 GHz) using the kinetic inductance of the superconducting film. The S-parameters measured at 400 mK, using a sorption cooler, show the four resonances between 23.3 and 26.3 GHz at 1 GHz spacing, with a maximum transmission on resonance of -1 dB. Four-wave mixing has been observed with each resonance, and a maximum signal gain of 30 dB has been measured, corresponding to 29 dB of insertion gain. The noise performance of the amplifier has been measured, showing an added noise of 1.2 half quanta at 400 mK. These results are relevant to high-frequency Axion dark matter experiments and help motivate the exploration of higher frequencies in quantum technologies.

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physics.ins-det 2026-04-30

Two TCAD tools align on irradiated silicon pixel detector metrics

Comparison of Silvaco and Synopsys TCAD Predictions Including the Perugia Radiation Damage Model in Silicon Pixel Detectors for the HL-LHC

Silvaco and Synopsys predictions match for leakage current, depletion voltage and electric field under the Perugia model at HL-LHC fluences

abstract click to expand

At the High Luminosity Large Hadron Collider (HL-LHC), silicon pixel detectors will be exposed to radiation fluences about 5 to 10 times larger than those experienced by the current innermost pixel layers up to today. Signal loss will be the main limitation to tracking and vertexing performance due to radiation damage in hybrid pixel detectors, with the increase in leakage current and depletion voltage posing severe constraints on operating conditions. It is important to have reliable predictions for all observables - such as charge collection performance, leakage current level and breakdown voltage - after irradiation, in order to estimate operational voltage values and to test the robustness of tracking algorithms. In this paper, the predictions of Silvaco and Synopsys TCAD device simulations are compared when the surface and bulk defects and traps of the ``Perugia radiation damage model'' are included. The results are quite promising regarding leakage current, depletion voltage, electric field and trap statistics, at two distinct reference temperatures and fluences.

0

physics.ins-det 2026-04-29

The paper shows that machine learning models can separate Cherenkov and scintillation…

Machine Learning Enables Real-Time Waveform Decomposition for Dual-Readout Calorimetry

Machine learning achieves comparable waveform decomposition performance to template fitting for dual-readout crystals at reduced sampling…

abstract click to expand

Dual-readout calorimeters achieve superior energy resolution by simultaneously measuring Cherenkov and scintillation signals for event-by-event electromagnetic fraction correction, making them attractive for next-generation Higgs factories. However, if a full waveform readout is required for time-based analysis to separate Cherenkov and scintillation signals, high off-detector data rates might present challenges. These challenges can be mitigated by real-time signal processing in front-end electronics. We present a systematic comparison of machine learning (ML) and template fitting approaches for the separation of scintillation and Cherenkov light components in homogeneous dual-readout calorimeters across three representative crystal types. ML models achieve comparable signal extraction performance at lower sampling rates than template fitting. A single model trained over a range of incident particle energies demonstrates robust performance, and FPGA-compatible compression achieves latencies suitable for real-time application. This work establishes both baseline template fitting performance and ML-enhanced alternatives for crystal-based dual-readout calorimeters, offering practical pathways towards front-end feature extraction in future detector design.

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physics.ins-det 2026-04-29

New filament improves 3D-printed scintillators

A new diffuse reflector filament for additive manufacturing of 3D printing finely-segmented plastic scintillator

Lower crosstalk and higher yield in compact segmented detectors match standard performance

abstract click to expand

This study presents the development and the characterization of novel white reflective filaments suitable for additive manufacturing of finely segmented plastic scintillators. The filament is based on polycarbonate (PC) and polymethyl methacrylate (PMMA) polymers loaded with titanium dioxide (TiO$_2$) and polytetrafluoroethylene (PTFE) to enhance reflectivity. A range of filament compositions and thicknesses was evaluated through optical reflection and transmittance measurements of reflective layers made with the Fused Deposition Modeling (FDM) technique. A 3D-segmented plastic scintillator prototype was made with fused injection modeling (FIM) and tested with cosmic rays to assess the light yield and the optical crosstalk. The results demonstrate the feasibility of producing compact and modular 3D-printed scintillator detectors with a performance analogous to standard plastic scintillator detectors. Owing to the improved optical properties of the new reflector filament, a lower light crosstalk and a higher light yield, compared to past works, is obtained.

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physics.ins-det 2026-04-29

JUNO small-PMT electronics hit 0.04 photoelectron noise

Embedded underwater front-end electronics for the 3-inch photomultipliers in the JUNO experiment

Validated boards deliver under 0.4 percent crosstalk and 57 MB/s bandwidth for reliable single-photoelectron detection in the 20-kton scint

abstract click to expand

The Jiangmen Underground Neutrino Observatory (JUNO) is a 20-kton liquid scintillator-based, low-radioactivity, multi-purpose neutrino detector located 693 meters (1800 m.w.e.) underground in the Guangdong province, China. To detect scintillation light produced in the target, the detector is equipped with 17,612 20-inch photomultipliers (PMTs), forming the Large PMT system (LPMT). In addition, 25,600 3-inch photomultipliers (the Small Photomultiplier System or SPMT) are deployed in the gaps between the LPMTs. This paper presents the design and performance of the underwater front-end electronics developed for the SPMT system. It details the individual electronics boards and their key components, the inter-board interfaces, the system-level design, and the firmware architecture that supports data acquisition and control. It also outlines mechanical and thermal integration, board validation procedures, and system performance metrics. The readout chain includes digitization of 128 PMT channels per unit, synchronized time-stamping, charge measurement, event packaging, and bandwidth management. Comprehensive validation confirms the system's readiness to meet JUNO's stringent physics goals. The underwater electronics achieve noise levels as low as 0.04 photoelectrons with minimal crosstalk (below 0.4%) and a bandwidth of 57 MB/s, ensuring reliable single photo-electron detection and operation under high-rate conditions. The SPMT system has now been fully integrated and installed in JUNO. Its commissioning and physics performance will be reported in a future publication.

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physics.ins-det 2026-04-29

Transparent electrodes boost few-photon detection in cryogenic silicon detectors

NTL-amplified cryogenic light detectors with optically transparent electrodes

ITO layers on silicon supply both the bias field for NTL amplification and anti-reflection, simplifying devices tested at millikelvin scales

abstract click to expand

The Neganov-Trofimov-Luke (NTL) effect is used by experiments based on cryogenic detectors to boost the sensitivity of light-sensitive devices down to a few optical photons. In this work we introduce a silicon light-detector technology that implements NTL amplification at millikelvin temperatures using transparent indium-tin-oxide (ITO) electrodes. The ITO electrodes enable an electric field perpendicular to the wafer surface, mitigating surface charge recombination, and thanks to their optical properties, simultaneously serve as an anti-reflective coating. By combining these two functions in a single element, the fabrication process is simplified, yielding more robust and cost-effective devices. We report on the production and characterization of the first batch of these detectors. We performed a room-temperature characterization of the ITO electrodes, verifying the structural and optical characteristics of the deposited electrodes. We then operated 2 of these devices as cryogenic calorimeters at millikelvin temperatures. Finally, we develop a consistent analytical model for the NTL gain for both ionizing particles and optical photons, successfully describing the gain dependence on the NTL bias and explicitly accounting for the partial electrode coverage of the device surface.

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physics.ins-det 2026-04-29

Calibrated radon counter now measures backgrounds for dark matter searches

A radon emanation measurement system at the Carleton Noble Liquid Detector Laboratory

The COLD lab system quantifies radon from materials and gases to support future rare-event detectors.

abstract click to expand

Radon is one of the most important sources of background in rare event search experiments, such as those searching for Dark Matter and neutrinos, due to its unavoidable production from natural uranium. In low-background experiments, radon emanation from detector materials and components accounts for a major portion of contamination. To investigate this, a radon detection system was developed at the Carleton nOble Liquid Detector Laboratory (COLD Lab). The setup consists of a stainless steel emanation chamber, a low-background ZnS(Ag) cell, and an assembly for radon transfer and collection. This setup was used to study radon emanation from materials under vacuum conditions. Additionally, a charcoal trap made of activated charcoal and equipped with a flow meter was constructed to study radon levels in nitrogen gas and the residual radon in the gas filter used in the DEAP-3600 processing system. The radon concentration in the glove box, where critical DEAP-3600 internal detector components were completed, was also calculated based on these measurements. Now calibrated and in-use, the COLD lab radon emanation counter is an essential diagnostic tool for reducing backgrounds in future rate-event search experiments.

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physics.ins-det 2026-04-29

ImageJ plugin removes noise from microscopy images while keeping signal

Background Remover -- an effective tool for processing noisy microscopy images

Background Remover differentiates signal and noise pixels to enable analysis of varying-intensity objects in low signal-to-noise conditions.

abstract click to expand

Background Remover (BGR) is a novel software tool developed as a plugin to the well-known ImageJ program and designed to address the challenges of analysing fluorescent microscopy images characterized by low signal-to-noise ratios and heterogeneous backgrounds. The used algorithm effectively differentiates between signal and noise pixels, preserving the signal while eliminating noise. This functionality enables the analysis of images with objects of varying intensities, allowing for reliable identification even in low signal-to-noise ratio conditions. Furthermore, BGR offers the capability to determine the intensity of identified objects, enhancing its utility for researchers in the field. The paper describes the algorithm and the program functioning, as well as the carried out tests of its performance. The program is freely downloadable from the website https://kilianna.github.io/background-remover/

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physics.ins-det 2026-04-28

X-ray scans confirm uniform response in MuPix11 pixels

Investigation of the in-pixel response of the Mupix11 monolithic pixel sensor using a microfocus X-ray beam at Diamond Light Source

At nominal voltage the 3-micron beam tests find consistent detection across the matrix, supporting reliable use in particle tracking.

abstract click to expand

MuPix11 is a High-Voltage Monolithic Active Pixel Sensor (HV-MAPS) developed for the tracking system of the Mu3e experiment. The in-pixel photon response of a MuPix11 sensor thinned to 70 {\mu}m was measured using an 8 keV X-ray beam with a 3 {\mu}m spot size at the B16 beamline at Diamond Light Source, emulating the passage of a minimum ionising particle (MIP). At nominal operating voltage and threshold, high-resolution scans across the pixel matrix show the detector response to be uniform. In the absence of reverse bias (0 V), the relative sub-pixel response is location-dependent as a reduced detection rate is observed at pixel boundaries.

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physics.ins-det 2026-04-28

DUNE prototype validates charge readout electronics for full detectors

Design of the DUNE horizontal drift far detector charge readout electronics and performance in ProtoDUNE-HD

Tests in the 770-ton ProtoDUNE-HD show the design meets noise and stability needs for neutrino oscillation measurements.

abstract click to expand

DUNE (Deep Underground Neutrino Experiment) is a long-baseline neutrino oscillation experiment currently under construction, whose far detectors will be the largest liquid argon time projection chambers ever built. This detector design calls for custom-built cryogenic front-end electronics to attain the required detector performance. This paper describes the charge readout electronics that will be used in the DUNE horizontal drift (HD) far detector and presents performance results using data from the ProtoDUNE-HD detector, a 770 ton liquid argon time projection chamber operated at the CERN Neutrino Platform in 2024 that served as the final prototype of the DUNE HD design.

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physics.ins-det 2026-04-28

Carbon implantation alone improves LGAD radiation tolerance

Systematic Investigation of Acceptor Removal in HPK LGADs with Modified Gain Layers

Tests of HPK prototypes show it outperforms oxygen modifications and compensation after proton and neutron exposure.

abstract click to expand

Low-Gain Avalanche Diodes (LGADs) are fast silicon sensors with internal charge multiplication and are key candidates for precision timing layers in future high-energy hadron colliders. Their operation in harsh radiation environments, however, is limited by acceptor removal in the gain layer, which reduces the active acceptor concentration and degrades the internal electric field required for avalanche multiplication. Improving the radiation tolerance of the gain layer is therefore essential for future 4D tracking applications. In this work, we investigated several LGAD prototypes produced in collaboration with Hamamatsu Photonics K.K. (HPK), featuring modified gain-layer designs, including oxygen-modified, carbon-implanted, and boron--phosphorus compensated structures. The sensors were studied after proton and reactor-neutron irradiation. Radiation tolerance was characterized using the acceptor-removal coefficient extracted from IV measurements and the operation voltage required to recover the timing performance after irradiation. The results show that carbon implantation is the only approach among those studied here that provides a clear improvement in radiation tolerance. In contrast, neither oxygen-related modification, including the Partially Activated Boron (PAB) approach, nor gain-layer compensation alone yields a significant improvement, and the compensated carbon-implanted structure shows no clear advantage over the carbon-only case. In addition, the acceptor-removal coefficient is found to depend on the irradiation particle type and energy.

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physics.ins-det 2026-04-28

Depletion nonuniformity causes GaN detector energy tail

Development and Performance Study of Vertical GaN α-Particle Detector with High Energy Resolution

Geant4 model matches experiment and shows how to suppress the tail for 2.69 percent resolution

abstract click to expand

High-energy-resolution GaN $\alpha$-particle detectors have significant potential for space radiation, nuclear instrumentation, and harsh-environment applications. However, existing GaN $\alpha$-particle detectors still face several key challenges, including reducing the dead-layer thickness, suppressing leakage current under high reverse bias, improving energy resolution, and clarifying the physical mechanism underlying the low-energy tail phenomenon. This study presents a vertical homoepitaxial GaN $\alpha$-particle detector integrating a 20-nm ultrathin dead layer and a guard-ring structure. The detector exhibits an ultralow leakage current of 2.195 nA at -200 V and an intrinsic energy resolution of 2.69% with a charge collection efficiency (CCE) of 95.9% at -260 V. More importantly, this work demonstrates for the first time through Geant4 simulations that depletion-width nonuniformity is the dominant source of partial energy leakage, leading to an extended low-energy tail in the energy spectrum. We establish a depletion-width nonuniformity model and observe good agreement between simulation and experiment. This finding provides practical guidance for the design and optimization of high-performance GaN-based radiation detectors.

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physics.ins-det 2026-04-27

Thermal aberrations split mode mismatch into low-pass and high-pass types

Squeezed state degradations due to mode mismatch and thermal aberrations in gravitational wave detectors

Quadratic wavefront mismatch limits squeezing at low frequencies while higher orders act at high frequencies, affecting current and future 3

abstract click to expand

To date, frequency-dependent squeezed light has been used to reduce quantum noise in interferometric gravitational wave detectors by 6.1 dB (a factor of two). Future upgrades and detectors aim to both reduce quantum noise by 10 dB (a factor of three) and to increase the circulating power in the interferometer arm cavities. Achieving these goals will be extremely challenging due, in part, to the degradations to the squeezed state caused by mode mismatch between the internal interferometer optical cavities and between the auxiliary external cavities. It is therefore imperative to gain a detailed understanding of all sources of mismatch and to obtain experience in mitigating their effects in the current detectors in order to improve astrophysical sensitivity now and in the future. Two types of internal mismatch are identified which are due to the thermal aberrations generated when the test mass optics absorb a small fraction of the circulating arm power. It is found that the dynamics responsible for the degradations caused by the mismatch between the quadratic part of the wavefront of two modes has a characteristic low-pass frequency dependence while the dynamics of the mismatch due to all higher order thermal aberrations has a high-pass behavior. As a consequence, the two types of mismatch are predominantly responsible for different squeezing degradations -- some of which are significant for the current detectors and some of which will only be important for future detectors with longer arms. The behavior of these two types of internal mismatch are described and the implications for detector design, operation, and characterization are discussed.

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physics.ins-det 2026-04-27

Automated resin process makes 2D scintillator arrays in hours

Pixelated Plastic Scintillator Array Manufacturing using Fast-, Photo-Curable Resin

Custom photocurable material and machine yield pixel grids with per-pixel readout and gamma-neutron pulse separation.

abstract click to expand

Pixelated plastic scintillator arrays can serve as high efficiency and high resolution neutron imaging detectors. Manufacturing these arrays is intensive in both time and labor. This work presents a fabrication method based on additive manufacturing for two-dimensional plastic organic scintillator arrays using a custom-built automated assembly machine and a custom photocurable resin that has significant non-aromatic acrylate oligomer content. The process involves two main stages: fully autonomous production of one-dimensional layered arrays, followed by semi-autonomous cutting and stacking to form two-dimensional pixel arrays. One-dimensional arrays were manufactured at a rate of around 4 layers per hour with minimal defects and tight dimensional tolerances, while two-dimensional arrays up to 7 x 7 pixels and 70 mm in length were completed in approximately 3.5 hours. Final arrays exhibited dimensional deviations of less than 0.5 mm. Two-dimensional arrays read out by a multi-anode photomultiplier tube demonstrated per-pixel position resolution and pulse-shape discrimination, enabling gamma-neutron interaction separation in mixed radiation environments.

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physics.ins-det 2026-04-27

KIDs hold steady after 10-year-equivalent proton dose

Effect of total dose proton irradiation on the performance of Kinetic Inductance Detectors for far-Infrared space observatory

Tests at 120 mK find unchanged lifetime and responsivity, with noise rise traced to data analysis limits.

abstract click to expand

Kinetic Inductance Detectors (KIDs) are a promising technology for future space missions, where exposure to high-energy particles may affect detector performance. In this work, we irradiated two types of KID arrays, absorber coupled and antenna coupled, with high-energy protons at 120 mK. We used a total dose equivalent to approximately 10 years of operation at the L2 Lagrange point. A comparison between pre-irradiation and post-irradiation measurements (24 hours after a 5.7 krad total dose) was done, while keeping the detectors at 120 mK. We find that there is no significant change in the quasi-particle lifetime {\tau}_qp and the dark responsivity d{\theta}/dPdark, but we do observe an increase in the noise and NEP that is tentatively attributed to limitations in the post radiation data analysis.

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physics.ins-det 2026-04-27

Quad and pixel AI readouts reach 90% pion-kaon ID in high background

Readout and PID using AIML for SoLID High Background Cherenkov Detectors

MAROC sum electronics and multilayer perceptrons outperform simple cuts for SoLID Cherenkov PID.

abstract click to expand

We present the development of readout electronics and artificial-intelligence-based particle-identification methods for the SoLID Cherenkov detectors at Jefferson Lab. To operate in the high-rate, high-background SoLID environment, we designed a MAROC sum readout system for multianode photomultiplier tubes that provides simultaneous pixel, quadrant-sum, and total-sum signals. Bench studies show that the system can sustain rates at or above those expected for SoLID while maintaining acceptable pedestal behavior and signal linearity. Using realistic Geant4 simulations for the heavy-gas Cherenkov detector, we then investigate $\pi/K$ separation with beam-related background. A simple photoelectron-counting cut is insufficient under these conditions, whereas multilayer perceptron models trained on PMT, quad, and pixel readout data perform substantially better. The quad and pixel readout schemes achieve pion and kaon efficiencies above 90\% and clearly outperform PMT-only readout. These results demonstrate that the combination of high-rate MAROC sum electronics and AIML-based pattern recognition provides a practical path toward robust SoLID Cherenkov PID.

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physics.ins-det 2026-04-27

Tabletop Kibble balance holds constant velocity over 180 μm

Recent Advances in Tabletop Kibble Balance -- KBmini

A higher-turn coil and multi-harmonic drive create a flat induced-voltage region above 1 V, preparing the system for accurate mass checks up

abstract click to expand

This paper presents recent advances in the KBmini Kibble balance, a tabletop system for E2-accuracy mass calibration up to 1 kg. The $Bl(z)$ profile is characterized by manually setting the magnet at different vertical positions, and the extremum point is selected as the weighing position. The spring constant of the weighing cell around this point is measured. With a new coil of a larger number of turns and a multi-harmonic excitation technique, a near-constant velocity profile over a moving range of 180 $\mu$m, producing an induced-voltage flat-top region exceeding 1 V, is achieved. These results establish a foundation for subsequent mass calibration experiments.

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physics.ins-det 2026-04-27

Tabletop Kibble balance advances in electrical and mechanical systems

Status of the Tsinghua Tabletop Kibble Balance

Progress since 2024 enables initial weighing and velocity measurements toward SI mass calibration.

abstract click to expand

This paper reports on the status of the Tsinghua tabletop Kibble balance experiment, aiming to deliver a mass calibration instrument for kilogram realizations in accordance with the new International System of Units (SI). Major progress since 2024 in different aspects, i.e., electrical, magnetic, mechanical, and optical, is presented. The primary weighing and velocity measurement results are discussed.

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physics.ins-det 2026-04-27

Negative impedance enables tunable RLC oscillations

Oscillation with Negative Impedance

Cross-coupled transconductance pairs provide energy to L and C for resonance, with frequency shifted by added passive R, L, and C elements.

abstract click to expand

Oscillation and frequency modulation have been leveraged for applications in detection (or sensing), data processing, and telemetry. This work provides a theoretical analysis of oscillation phenomena with negative impedance implemented using a cross-coupled transconductance pair. The negative impedance can consist not only of a negative resistance but also of a negative inductance and a negative capacitance, where the negative resistance supplies energy to the inductance and capacitance, causing oscillation at a resonant frequency. Also, the resonant frequency can be modulated by combining with passive components such as a resistor, an inductor, and a capacitor. In this work, a comprehensive circuit analysis employing small-signal models and transfer functions is performed to understand the oscillation phenomena and resonant frequencies arising from a combination of active and passive RLC circuits, in which the active RLC circuit is modeled as a negative impedance and implemented using a cross-coupled transconductance pair.

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physics.ins-det 2026-04-27

Beam test characterizes Pb/SciFi calorimeter prototype

Beam test of a Pb/SciFi prototype for the Barrel Imaging Calorimeter at the Electron-Ion Collider

Electron beam data from CERN offers metrics for energy and timing to support EIC detector optimization

abstract click to expand

A Lead-Scintillating Fiber (Pb/SciFi) prototype for the Barrel Imaging Calorimeter (BIC) at the Electron--Ion Collider (EIC) was tested with electron beams at the CERN PS T10 beam line in August 2024. The prototype consisted of unit modules with a sampling structure of lead sheets and scintillating fibers, corresponding to a total depth of approximately $10.9\,X_{0}$. Beam tests were performed with electron momenta between 0.5 and 3~GeV/$c$ to evaluate the energy and timing performance of the prototype. This study characterizes the performance of a Pb/SciFi prototype and provides input for future beam tests, calibration and readout optimization, and the development of larger-scale prototypes.

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physics.ins-det 2026-04-24

AI agents optimize full detector parameters in one simulation loop

Phenomenological Detector Design and Optimization in Vertically-Integrated Differentiable Full Simulations with Agentic-AI

Bilevel framework lets language models tune crystal geometry, ADC bits, and clustering radius together for a dual-readout calorimeter.

abstract click to expand

We present the first implementation of AI agents into the design and optimization of detectors in high-energy physics experiments via a bilevel optimization framework that vertically integrates detector geometry, front-end digitization, and high-level reconstruction algorithm parameters in differentiable full simulations. Using the example of a dual-readout, segmented crystal EM calorimeter with a baseline resolution of $3\%/\sqrt{E}$, we investigate the capabilities and value propositions of AI agents in the identification and reduction of key detector parameters and in the nonlinear traversal of a given detector design's full parameter space. We find that LLM-based reasoning models today, without being given additional experiment-specific context, are able to effectively execute complex workflows and proactively suggest generic but relevant avenues for further study or improvement. Here, we demonstrate an AI agent's ability to use the workflow to simultaneously optimize a representative subset of vertically integrated detector parameters: crystal granularity and length, number of ADC bits and sampling rate, and center-of-gravity hit-clustering radius. We find that effective integration of agents into the complex workflows of frontier areas of research not only significantly reduces labor and compute, but opens up efficient avenues for computational validation of first-principles design choices. While the ability to make autonomous leaps of physics-motivated judgment or insight is not demonstrated in this work, this study defines the current frontier of experimental design methods in high-energy physics.

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physics.ins-det 2026-04-24

Lab tests set stable operating conditions for R760 tubes in PLUME

Performance characterisation of the Hamamatsu R760 photomultiplier tube for the PLUME detector

Gain, timing drift, linearity, dark current and ageing measurements define parameters for reliable luminosity data in Runs 3 and 4.

abstract click to expand

The Probe for Luminosity Measurement detector is a novel luminometer designed to monitor the luminosity and beam conditions of the Large Hadron Collider at the interaction point of the LHCb experiment, starting from Run 3. The detector is based on a hodoscope composed of 48 Hamamatsu R760 photomultiplier tubes, which detect the Cherenkov light produced by charged particles originating from the interaction region. The accurate and stable operation of these sensors is essential to ensure reliable luminosity measurements throughout the full data-taking period. This paper presents a detailed characterisation of the photomultiplier tubes currently installed in the detector. In particular, their absolute gain, transit-time drift, linearity, dark current, and ageing behaviour are systematically studied under controlled laboratory conditions. The results provide a comprehensive assessment of the performance of the detection modules and establish the optimal operating conditions required to ensure stable and precise measurements throughout Run 3 and Run 4.

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physics.ins-det 2026-04-24 Recognition

Liquid argon test stand reaches 0.25 ppb impurity level

Liquid argon purification and purity monitoring: apparatus and first results

Yields 1.5 ms electron lifetime at 500 V/cm to support large detector readout development.

abstract click to expand

We report results from a 13-liter purified liquid argon test stand at Wellesley College. The system includes a single-pass liquid-phase purification column, a double-gridded purity monitor to assess the electron lifetime, and a slow control and data acquisition system. Initial measurements demonstrate an O$_2$-equivalent impurity concentration of 0.25 ppb, corresponding to an electron lifetime of 1.5 ms at a drift field of 500 V/cm. This test stand supports ongoing detector R&D on charge and light readout technologies for future large-scale liquid argon time projection chambers, such as Q-Pix and other cold electronics systems, as part of a facility at Wellesley College for fundamental studies of LArTPC readouts.

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physics.ins-det 2026-04-24

Liquid argon purification reaches 0.25 ppb impurity level

Liquid argon purification and purity monitoring: apparatus and first results

A 13-liter test stand yields 1.2 ms electron lifetime at 500 V/cm, sufficient for meter-scale charge drift in future detectors.

abstract click to expand

We report results from a 13-liter purified liquid argon test stand at Wellesley College. The system includes a single-pass liquid-phase purification column, a double-gridded purity monitor to assess the electron lifetime, and a slow control and data acquisition system. Initial measurements demonstrate an O$_2$-equivalent impurity concentration of 0.25 ppb, corresponding to an electron lifetime of 1.5 ms at a drift field of 500 V/cm. This test stand supports ongoing detector R&D on charge and light readout technologies for future large-scale liquid argon time projection chambers, such as Q-Pix and other cold electronics systems, as part of a facility at Wellesley College for fundamental studies of LArTPC readouts.

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physics.ins-det 2026-04-23

GEM gain rises with radiation then reverses when rate drops

Charging-up and reverse charging-up phenomena in a double-mask triple GEM detector

Charging-up of the dielectric foil increases the gain at high irradiation rates, while reverse charging-up restores the original gain as the

abstract click to expand

The Gas Electron Multiplier (GEM) detectors are widely used in high-energy physics (HEP) experiments as tracking devices because of their excellent position resolution and to handle high particle rates capability. Charging-up effect is a well known phenomenon in GEM detectors because of the presence of the dielectric medium -- Kapton in the foil. Charging-up of GEM foil takes place when it is exposed to high radiation after application of high voltage. A new phenomenon of reverse charging-up, a complementary behaviour is also observed when the irradiation rate is reduced, where the gain relaxes gradually towards its initial value. In this study, the charging-up and reverse charging-up effects are investigated for a double-mask triple GEM chamber operated with an Argon and Carbon dioxide (70/30) gas mixture. The measurements provide a detailed understanding of the gain variation under irradiation and its stabilisation behaviour. The experimental setup, methodology and results are presented in this article.

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physics.ins-det 2026-04-23

260-liter argon test stand hits 0.5 ms electron lifetime

A 260-Liter Test Stand for Liquid Argon R&D

Pump-free purification and seven-day cycles enable rapid component testing for large LArTPCs

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We describe the design and performance of a 260-liter liquid argon (LAr) cryogenic test stand for liquid argon detector research and development at BNL. The system uses gas-phase argon purification with continuous pump-free circulation, in which boil-off argon gas is purified, recondensed, and returned to the cryostat by gravity without a mechanical recirculation pump; it also incorporates an upgraded condenser that increases the effective thermal contact area by a factor of 13 relative to the previously developed 20-liter system reported perviously. A liquid argon purity monitor is installed to measure the electron lifetime directly in LAr, enabling quantitative characterization of charge attenuation due to electronegative impurities. Under the operating conditions reported here, the demonstrated electron lifetime is 0.5 ms. The system is designed to enable rapid iteration of detector components in complete operational cycles, including pump-down, leak verification, cryogenic fill, stable operation, and warm-up, which can be completed within 7 days. Such a fast turnaround time, together with the medium-scale liquid volume and direct purity diagnostics, makes the facility well suited for testing and refining detector designs in support of large liquid argon time projection chamber (LArTPC) experiments.

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physics.ins-det 2026-04-23

Live scan offsets remove drift from STEM image sequences

Predictive drift compensation of multi-frame STEM via live scan modification

Predictive framewise and pixelwise adjustments to the next scan grid preserve usable area across multiple frames.

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Scanning transmission electron microscopy (STEM) is widely used tool for materials characterisation. However, being a scanned technique, STEM is susceptible to sample, stage or beam drift, manifesting as distortions within images or movement in the field-of-view during multi-frame imaging. Often this is corrected post-acquisition using image registration of multiple frames, but drift reduces the usable area common to all frames. Here we present a method to mitigate sample drift by analysing past frames to predict the sampling-grid points for the immediately future frame. We present this correction across two time-scales and two lengthscales. By offsetting the scan-grid framewise we remove long-range drift, and offsetting pixelwise we minimise intra-image warping. Examples are presented for both atomic-resolution imaging and lower-magnification in-situ video capture. The framework is general to raster, serpentine, interlaced and other scan patterns, as well as sequential or scan-rotation series STEM.

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physics.ins-det 2026-04-23

Graphene-SiC detector holds 58 ps timing after 1 MGy X-rays

Stability of Charge Collection Efficiency and Time Resolution in a Novel Ultra-fast Graphene-Optimized Silicon Carbide Detector Under X-ray Irradiation

Charge collection stays at 99 percent and leakage current remains low, enabling use in high-radiation environments.

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A graphene-optimized silicon carbide PIN detector was fabricated and its radiation tolerance under X-ray irradiation of 160 keV was evaluated. Its electrical properties, charge collection performance and time resolution of beta-particles (90Sr) are reported. After 1 MGy irradiation, the detector maintains an ultralow leakage current of approximately 2.2e-10 A @ 300 V and the C-V characteristics are basically consistent with full depletion at 120V. The time resolution of the graphene-optimized silicon carbide detector is 58.0 ps. The time resolution is comparable to that of state-of-the-art 4H-SiC low-gain avalanche detectors (LGADs). The G/RE 4H-SiC PIN detector exhibits outstanding time resolution performance. Compared with the time resolution of the RE 4H-SiC PIN detector, the time resolution of the G/RE 4H-SiC PIN detector has decreased by 39.6%. This demonstrates the significance of the graphene electrode design. The graphene detector exhibits a charge collection efficiency (CCE) of 99.24% after X-ray irradiation, along with excellent stability. The graphene-optimized silicon carbide detector maintains good timing resolution: 58.0ps before and 64.0ps after X-ray irradiation. Experimental results indicate that the CCE and time resolution performance exhibit good stability before and after irradiation. These results demonstrate stable performance under extreme X-ray exposure, highlighting the detectors potential for radiation-hard applications in high-energy physics, space missions, and nuclear reactor monitoring.

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physics.ins-det 2026-04-22

Fast snapshot reference removes drift from slow electron scans

Drift Correction of Scan Images by Snapshot Referencing

A high-signal quick image calculates per-pixel corrections for analytical maps without extra hardware.

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Reliable quantitative analysis in scanning (transmission) electron microscopy (S(T)EM) is often hindered by image drift during long-duration spectral mapping for elemental analysis or for various material functions. We here present snapshot-referencing (SSR) drift correction, a retrospective approach to eliminate spatial distortions based on the temporal nature of the scanning process; A continuous drift vector for every pixel is calculated for a normalized time-field of the scan pattern (e.g., serpentine or raster) utilizing a high-signal, fast-scan "snapshot" as a drift-free reference to guide the correction of simultaneously acquired analytical maps. To describe the drift, we employed Bezier basis functions to model smooth thermal or mechanical drifts and piece-wise linear basis for high-frequency "spiky" shifts such as those caused by charging. We demonstrate the efficacy of this approach on experimental cathodoluminescence (CL) datasets, showing that it effectively restores spatial integrity to hyperspectral data cubes without the need for specialized hardware. This flexible, software-based solution is broadly applicable to any probe-based analytical technique where a fast imaging signal can be recorded alongside slow spectroscopic data.

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physics.ins-det 2026-04-22

Hybrid optical-waveform readout achieves 44° 3D electron track resolution

Three-dimensional recoil-electron reconstruction using combined optical imaging and waveform readout for electron-tracking Compton cameras

The approach improves angular accuracy by a factor of 1.3 over strip readouts while avoiding the data overload of full 3D systems for large

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Accurate reconstruction of recoil-electron directions is critical for enhancing the point-spread function of electron-tracking Compton cameras (ETCCs) in gamma-ray imaging. Although full three-dimensional (3D) readout systems achieve high-precision reconstruction, they are impractical for large-area detectors because of the enormous data volume. This study proposes and demonstrates a practical alternative for inferring the 3D recoil-electron direction in Compton scattering. This method combines a high-resolution two-dimensional optical image, a one-dimensional waveform signal, and a deep-learning-based method through simulations. The proposed method achieved an angular resolution of approximately $44^\circ$ for the recoil-electron direction in the 40-50 keV range, corresponding to an improvement of a factor of about 1.3 compared with our previous strip-readout approach using pseudo-experimental data generated by Geant4 and MAGBOLTZ simulations for an argon-based gas time projection chamber. In addition, the starting-point resolution of the electron track was improved over the previous method across the 5-50 keV electron energy range. These results demonstrate that complementary information from the transverse image and longitudinal waveform can effectively recover the 3D track topology without requiring full 3D readout. The proposed approach provides a realistic pathway for improving ETCC imaging performance.

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