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arxiv: 1906.11379 · v1 · pith:CGNIVRXEnew · submitted 2019-06-26 · ⚛️ physics.ins-det · hep-ex· nucl-ex

Studies on small charge packet transport in high-resistivity fully-depleted CCDs

Miguel Sofo Haro , Guillermo Fernandez Moroni , Javier Tiffenberg This is my paper

Pith reviewed 2026-05-25 14:48 UTC · model grok-4.3

classification ⚛️ physics.ins-det hep-exnucl-ex
keywords CCDcharge transportdiffusionhigh-resistivity siliconionization depthfully-depleted detectorslateral spreadcharge packets
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The pith

A new technique measures lateral charge spread as a function of ionization depth in thick high-resistivity CCDs.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper develops a physical model for the transport of small charge packets through the bulk of thick, high-resistivity, fully-depleted CCDs before they reach the pixel wells. It introduces a measurement technique that determines how far the charge spreads laterally depending on the depth at which ionization creates it. Results from CCDs already operating in scientific instruments are shown and checked against a new mathematical algorithm that extends the standard model based solely on diffusion of charge in silicon.

Core claim

The transport of small charge packets in the bulk of thick high resistivity CCDs is modeled and measured, with a new technique providing lateral spread versus ionization depth, validated by an algorithm extending the diffusion model.

What carries the argument

A new mathematical algorithm that extends the diffusion-only model of charge transport in silicon by incorporating dependence on ionization depth.

If this is right

  • The extended model improves predictions of charge collection efficiency in thick CCDs used for scientific imaging.
  • Lateral spread can be calculated as a function of depth for different operating conditions.
  • The technique allows validation of diffusion-based models using data from existing instruments.
  • Charge packet behavior in the bulk can be simulated more accurately without full device-level Monte Carlo runs.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The method could be adapted to correct depth-dependent blurring in astronomical or particle-tracking images.
  • Similar depth-resolved measurements might apply to other thick silicon detectors such as CMOS sensors.
  • If the algorithm generalizes, it could simplify design iterations for future high-resistivity sensors.

Load-bearing premise

Charge transport in the CCD bulk is governed primarily by diffusion in silicon, without dominant contributions from other mechanisms such as trapping or field distortions.

What would settle it

Direct comparison of measured lateral spreads for controlled ionization depths against the algorithm's predictions; significant unexplained deviations would falsify the extension.

Figures

Figures reproduced from arXiv: 1906.11379 by Guillermo Fernandez Moroni, Javier Tiffenberg, Miguel Sofo Haro.

Figure 1
Figure 1. Figure 1: A small charge packet, with size less than [PITH_FULL_IMAGE:figures/full_fig_p001_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Pixel cross section of a 250 µm thick CCD developed on Lawrence Berkeley Laboratory. Also, the electrostatic po￾tential generated by the three phases under the gates is shown as function of depth (Y axis) and one of the lateral directions (X axis). Image extracted from [4]. type) are drifted towards the collection wells of the CCD pixels, and it is related with the depth of charge generation point in the b… view at source ↗
Figure 5
Figure 5. Figure 5: Collection time of an event produced at depth [PITH_FULL_IMAGE:figures/full_fig_p003_5.png] view at source ↗
Figure 7
Figure 7. Figure 7: Example of a likelihood fit for a 20 e − event. In grey are the pointlike event pixels, and in red is the likelihood function fit with the events pixels. Then, fP can be used to estimate the spread the original spread of the carriers (σs) using a likelihood estimator L(Nc, xg, zg, σs) = max Nc, xg, zg, σs fP(p; Nc, xg, zg, σs) (13) For this work the maximization of the algorithm is imple￾mented using the M… view at source ↗
Figure 6
Figure 6. Figure 6: Simulation of 500 holes charge packet at two different [PITH_FULL_IMAGE:figures/full_fig_p005_6.png] view at source ↗
Figure 8
Figure 8. Figure 8: X-ray with an incident angle Θ and a interaction depth of y. distribution GF σs (σs) can be measured from the events in the output images of the experiment as GˆF σs (σs) = NF e (σs) NT GF Y (yw) (15) where NF e (σs) is the number of events with spread from 0 to σs, NT is the total number of events detected and GF Y (yw) is the known theoretical cumulative deposition distribution evaluated at the CCD edge.… view at source ↗
Figure 10
Figure 10. Figure 10: Cumulative distribution GY (y; θ) of the Kα1 lines from copper and rubidium fluorescence for an incident angle θ = 90◦ . 0.1 0.2 0.3 0.4 0.5 0.6 (pixel-size) σs pointlike event spread −0.06 −0.04 −0.02 0 0.02 0.04 0.06 0.08 0.1 (pixel-size) s σ-s σ 1 Cu Kα 1 Rb Kα [PITH_FULL_IMAGE:figures/full_fig_p007_10.png] view at source ↗
Figure 12
Figure 12. Figure 12: Charge spectrum of the events recorded with the CCD, [PITH_FULL_IMAGE:figures/full_fig_p007_12.png] view at source ↗
Figure 13
Figure 13. Figure 13: Measured GˆF σs (σs) distribution of each X-ray. As is indicated in equation 15, they were normalized by GF Y (yw), that is the expected absorbed number of X-rays in the 250 µm of the CCD silicon. 100 120 140 160 180 200 220 interaction depth y (µm) 0.3 0.35 0.4 0.45 0.5 0.55 (pixel-size) s σ pointlike event spread measurement 1 Cu Kα measurement 1 Rb Kα simulation 1 Cu Kα simulation 1 Rb Kα [PITH_FULL_I… view at source ↗
Figure 14
Figure 14. Figure 14: Measured spread-depth function, σs(y), for charge packets produced by X-rays. In dashed lines are the simulation results. of 50 V/cm) were used in the simulation and compared to results in [PITH_FULL_IMAGE:figures/full_fig_p008_14.png] view at source ↗
read the original abstract

In this work, we will present a physical model and measurements of the transport of small charge packets in the bulk of thick high resistivity CCD before being collected by the pixel potential wells. A new technique to measure the lateral spread of the charge as a function of the ionization depth in the bulk is presented. Results from measurements on CCD currently in use for several scientific instruments are shown and validated with a new mathematical algorithm to extend the current modeling based only on the diffusion of the charge in silicon.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 1 minor

Summary. The manuscript presents a physical model and measurements of the transport of small charge packets in the bulk of thick high-resistivity fully-depleted CCDs. It introduces a new technique to measure the lateral spread of the charge as a function of the ionization depth in the bulk. Results from measurements on CCDs currently in use for several scientific instruments are shown and validated with a new mathematical algorithm to extend the current modeling based only on the diffusion of the charge in silicon.

Significance. If the measurements are accurate and the validation demonstrates that the diffusion-only model can be extended without other mechanisms dominating, the work could improve charge-transport modeling for high-resistivity CCDs used in scientific instruments, aiding design and performance predictions.

major comments (1)
  1. [Abstract] Abstract (final sentence): the central claim that results are 'validated with a new mathematical algorithm to extend the current modeling based only on the diffusion of the charge in silicon' requires an explicit demonstration that diffusion is dominant. No quantitative test (depth-dependent residuals, temperature scaling, or comparison against independent drift maps) is referenced to bound contributions from trapping or field distortions; without this the algorithm risks absorbing those effects into an effective diffusion constant rather than extending the model.
minor comments (1)
  1. The methods section should specify the data acquisition and handling steps for the new measurement technique so that the lateral-spread extraction can be reproduced independently.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the constructive feedback on our manuscript. We address the single major comment below and will make corresponding revisions to clarify the scope of our validation.

read point-by-point responses

  1. Referee: [Abstract] Abstract (final sentence): the central claim that results are 'validated with a new mathematical algorithm to extend the current modeling based only on the diffusion of the charge in silicon' requires an explicit demonstration that diffusion is dominant. No quantitative test (depth-dependent residuals, temperature scaling, or comparison against independent drift maps) is referenced to bound contributions from trapping or field distortions; without this the algorithm risks absorbing those effects into an effective diffusion constant rather than extending the model.

    Authors: We agree that the abstract phrasing risks implying a stronger demonstration of diffusion dominance than is provided. The manuscript validates the extended diffusion algorithm through direct comparison to the new depth-dependent lateral-spread measurements on operational high-resistivity CCDs, showing good agreement across the explored ionization depths. However, the paper does not include the specific quantitative tests listed (depth-dependent residuals, temperature scaling, or independent drift-map comparisons) to bound possible contributions from trapping or field distortions. We will revise the abstract to state that the algorithm extends the diffusion framework and is validated against the measured depth dependence, and we will add a short discussion paragraph noting the operating conditions (bias, temperature) under which other mechanisms are expected to remain subdominant. These changes will be made without introducing new data. revision: partial

Circularity Check

0 steps flagged

No circularity identified; derivation self-contained against external benchmarks

full rationale

The abstract describes a physical model, measurements of lateral charge spread vs. ionization depth, and validation via a new algorithm extending a diffusion-only model. No equations, self-citations, fitted parameters renamed as predictions, or load-bearing uniqueness theorems are quoted in the supplied text. Without explicit reduction of any result to its own inputs (e.g., Eq. X defined in terms of Y or a fit called a prediction), no circular steps meet the strict quotation requirement. The central claim remains independent of the listed circularity patterns.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Abstract-only review yields no explicit free parameters, invented entities, or additional axioms beyond the domain assumption of diffusion-dominated transport; ledger kept minimal accordingly.

axioms (1)
  • domain assumption Charge transport in the CCD bulk is governed primarily by diffusion in silicon
    Stated in the abstract as the basis for the current modeling that the new algorithm extends.

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Forward citations

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