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Operation and performance of the CMS silicon strip tracker with proton-proton collisions at the CERN LHC

T0 review · 1 major / 5 minor · reviewed 2026-08-15 · deepseek-v4-flash

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Pith's one-line read This paper argues that the CMS silicon strip tracker remained fully operational through LHC Run 2 — with per-module hit efficiency above 99% after masking — that the APV25 preamplifier saturation seen in early 2016 was understood and…

desk verdict The definitive Run 1+2 operations paper for the CMS strip tracker, with a genuinely new APV25 saturation story and an end-of-life projection that deserves a sensitivity study before being quoted as a hard number. read the letter →

arxiv 2506.17195 v2 pith:3FWDS5V5 submitted 2025-06-20 physics.ins-det hep-ex

CMS Collaboration This is my paper · ORCID
classification physics.ins-dethep-ex
keywords siliconstriptrackerAPV25preamplifiersaturationradiationdamageleakagecurrentdepletionvoltagehitefficiencyLorentzangleLHCRun2
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

This paper reports the operational history and measured performance of the CMS silicon strip tracker, the largest silicon detector ever built, during LHC Runs 1 and 2. The central claims are that the detector kept its per-module hit efficiency above 99% once known bad modules are masked; that a saturation effect in the APV25 readout chip's preamplifier, seen in early 2016 at high luminosity, was traced to a temperature-dependent discharge time constant and cured by changing a single chip setting; and that radiation damage to sensors and optical links evolves as simulation predicts, with only about 1.5% of modules predicted to become inoperable by the design-integrated luminosity of $500~\mathrm{fb}^{-1}$. If true, the paper establishes that a large silicon tracker can be operated close to its design performance for a decade without physical access.

What carries the argument

The central object is the APV25 chip, the 128-channel analog readout ASIC ("analog pipeline voltage", 250 nm CMOS) whose preamplifier feedback network — a capacitor shunted by a field-effect transistor controllable through the VFP bias — sets how quickly the amplifier recovers after a large charge deposit. That time constant $\tau$ is the quantity that misbehaved at low temperature and the knob that fixed it. The second piece of machinery is the radiation-damage model built around the leakage-current damage rate $\alpha$ and the full-depletion voltage $V_{\mathrm{dep}}$, expressed through the effective doping concentration $N_{\mathrm{eff}}$, with annealing (beneficial and reverse) superimposed on the fluence delivered by a radiation-transport simulation; this model is what converts recorded luminosity into the end-of-life projections of leakage current, thermal runaway fraction, and depletion voltage.

What would settle it

Compare the per-module leakage currents measured after the LS2 warm period with the simulation re-run using the actual warm-day count and temperature ($+16~^\circ\mathrm{C}$ rather than $+18~^\circ\mathrm{C}$): if the measured values are systematically more than 20% above the re-run prediction, the fluence or annealing model underlying the 1.5% thermal-runaway forecast is biased, and the forecast should be revised.

Watch

Extended reading notes

Core claim

Seen in the paper's own terms, the discovery is that the two things that could have killed the tracker did not. First, the APV25 preamplifier, whose feedback capacitor must discharge between collisions, discharges far more slowly at subzero temperatures than at the $+4^\circ\mathrm{C}$ operation of Run 1; combined with the higher occupancies of Run 2 this caused charge build-up, a compressed signal-to-noise distribution, and a hit-efficiency loss that reached more than 7% in TOB layer 1 at $1\times10^{34}~\mathrm{cm}^{-2}\mathrm{s}^{-1}$. Setting the preamplifier feedback voltage bias (VFP) to its lowest value shortened the discharge time to below 1 $\mu\mathrm{s}$ and fully restored the Landau-like response. Second, the radiation-damage program shows that measured leakage currents and depletion voltages track simulation; the leakage-current damage rate is measured to be $(3.5\pm0.1)\times10^{-17}~\mathrm{A/cm}$, and extrapolation to $500~\mathrm{fb}^{-1}$ predicts about 1.5% of modules in thermal runaway, almost all in regions with known cooling defects, with the highest expected depletion voltage around 275 V, well below the 600 V supply limit.

Load-bearing premise

The end-of-life projections assume the radiation-damage simulation converts recorded luminosity into sensor fluence and annealing correctly; the paper itself reports that the simulation underestimates barrel leakage current by about 20% and underestimates the reverse-annealing step near 30 $\mathrm{fb}^{-1}$, and it assumes 120 warm days during LS2 while the tracker was actually warm about 160 days.

Editorial extensions

If this is right

  • The 2016–2018 data-taking is fully usable: after the VFP change, hit efficiency recovers to the pre-saturation level, and the simulation of the preamplifier saturation describes early-2016 data well enough for physics analysis.
  • The tracker can run at twice its design instantaneous luminosity without occupancy exceeding a few percent; readout deadtime only appears above 8% occupancy.
  • Signal-to-noise at the design end-of-life $500~\mathrm{fb}^{-1}$ is extrapolated to 12.4 (thin) and 16.7 (thick) sensors, above the design specification of 10.
  • Only about 1.5% of modules are projected to become inoperable by $500~\mathrm{fb}^{-1}$, concentrated in regions with known cooling problems; the predicted maximum depletion voltage of about 275 V leaves ample margin under the 600 V bias limit.
  • The 1% residual hit inefficiency is dominated by highly ionizing particles that saturate an APV25 for about five bunch crossings, a mechanism consistent with prior beam-test measurements.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • If the reported 20% underestimate of leakage current in the barrel reflects a fluence normalization bias rather than cooling-contact uncertainty, the thermal-runaway fraction at $500~\mathrm{fb}^{-1}$ would rise; the paper's own comparison provides the calibration point to check this.
  • The APV25 saturation mechanism — a temperature-dependent preamplifier recovery time — implies that any future silicon tracker using deep-submicron analog front-ends at low temperature should verify preamplifier recovery under pileup before data taking, not after.
  • The annealing treatment assumes 120 warm days during LS2 against roughly 160 actual warm days; re-running the projection with the true thermal history would give a sharper end-of-life estimate.
  • The observed suppression of thermal runaway when the coolant set point dropped from $-15~^\circ\mathrm{C}$ to $-20~^\circ\mathrm{C}$ suggests that operating temperature, not just fluence, is the controllable variable that sets the tracker's usable lifetime.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

1 major / 5 minor

Summary. This paper reports the commissioning, calibration, and operational performance of the CMS silicon strip tracker (SST) during LHC Runs 1 and 2, covering 2009–2018 with a total integrated luminosity of 192.3 fb^-1, and projects the detector state at 500 fb^-1 at the end of Run 3. The central claims are that the SST remained fully operational through Run 2 with an end-of-Run-2 hit efficiency above 99% after masking known bad modules; that the APV25 preamplifier saturation observed in early 2016 was understood and remedied by changing the VFP feedback setting; and that radiation damage to optical links and silicon sensors is generally consistent with simulation, with about 1.5% of modules expected to become inoperable by 500 fb^-1. The paper documents temperature-dependent calibration (noise, ENC scaling, LLD gain), the simulation chain and its material-budget validation, occupancy at up to twice the design luminosity, S/N evolution, Lorentz angle measurements, single-hit resolution, particle identification via dE/dx, and detailed comparisons of leakage current and depletion voltage with FLUKA-based simulations.

Significance. If the results hold, this is the definitive public reference for the operational performance of the world's largest silicon strip tracker over a full LHC run, and it will be cited by the tracker-operations, radiation-damage, and HL-LHC upgrade communities. The paper's strengths are its transparency and its quantitative validation: the APV25 saturation analysis includes a dedicated simulation model that is shown to reproduce the affected data (Figs. 25–28); the HIP deadtime hypothesis yields a testable prediction (efficiency versus bunch position within a train, Fig. 40) that agrees with data for a five-bunch-crossing deadtime; the cross-talk inputs come from a dedicated 2018 zero-field cosmic measurement; and the authors explicitly flag the known limitations of their radiation-damage model, including the ~20% leakage-current underestimate, the underestimated reverse-annealing step, and the LS2 warm-days assumption. The main weakness is that the single headline longevity number (1.5% inoperable modules at 500 fb^-1) is quoted without an uncertainty or sensitivity band even though the underlying simulation is documented in the same chapter as biased on three separate axes.

major comments (1)
  1. [7.2.3] Section 7.2.3 (with Figs. 53–55) and the summary in Section 8 state that about 1.5% of SST modules are expected to become inoperable through excessive leakage current or thermal runaway at 500 fb^-1, but this figure is given without any uncertainty band or sensitivity study despite three documented biases in the same chapter: (i) Section 7.2.1 and Fig. 49 report that the FLUKA-based simulation underestimates the layer-averaged leakage current by about 20% consistently for TIB and TOB, a discrepancy stated to be 'not yet understood'; (ii) Section 7.2.2 and Fig. 51 report that the reverse-annealing step near 30 fb^-1 is underestimated in magnitude; and (iii) Section 7.2.3 notes that the simulation assumes 120 warm days during LS2 whereas the actual warm period was about 160 days. Because leakage current drives the thermal runaway condition (Eqs. 9–10 and the example in Fig. 44), and because Fig. 54 shows the affected fraction rising steeply above 300 fb^-1, a 20% current underestimate could shift the 1.5% figure substantially and nonlinearly. I request a sensitivity statement or an uncertainty band for this projection (for example, a rescaling of the current-related damage rate or of the simulated fluence), plus a corresponding qualifier in Section 8. This concern does not affect the direct Run-2 performance measurements, but the quantitative longevity claim is currently stronger than the documented model biases justify.
minor comments (5)
  1. [2] The sentence 'A more detailed description of the CMS apparatus is report in Refs. [1, 12]' should read 'is reported in Refs. [1, 12]', and there is a stray period in Section 6.3 in 'regularly exceeded 3x10^33 cm^-2 s^-1., which means more than 20 interactions per bunch crossing'.
  2. [6.9] The sentence introducing Fig. 41 is garbled: 'The SST hit resolution measurements performed during the last year of Run 2 are shown in Fig. 41 41 functions of these parameters' should read 'are shown in Fig. 41 as functions of these parameters'.
  3. [6.5] The S/N extrapolation to 500 fb^-1 (Fig. 29) quotes 12.4 for thin and 16.7 for thick sensors without uncertainties; since these values are well above the design specification of 10 but the trend lines are fitted to data with spread, a brief statement of the extrapolation uncertainty would strengthen the longevity argument.
  4. [7.2.1] The text around Fig. 48 states that the simulation slightly overestimates the per-module leakage current in the TIB but underestimates it in TID, TOB, and TEC, while the following paragraph around Fig. 49 states that the simulation underestimates the leakage current by about 20% consistently for all TIB and TOB layers; the two statements should be reconciled or explicitly distinguished (per-module instantaneous comparison versus temperature-scaled layer averages), since the reader cannot tell which comparison the 20% figure refers to.
  5. [7.2.3] In the discussion of the LS2 warm-period assumption, the text states that the assumed 120 days at +18 degrees Celsius is compensated by an actual 160 days at +16 degrees Celsius, but the net effect on the simulated annealing is not stated; since Section 7.2.2 already reports that reverse annealing is underestimated in the simulation, an explicit statement of which assumption dominates would help in interpreting the Vdep projections in Fig. 55.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: this is an operational measurement paper whose fitted quantities are empirical characterizations, and whose extrapolations rest on stated physical models rather than on the quantities they claim to predict.

full rationale

The paper's main claims—hit efficiency above 99% after masking, the APV25 saturation diagnosis and VFP remedy, and radiation-damage trends—are direct measurements or empirically validated models, not derivations that feed their own outputs back in as inputs. The equivalent-noise-charge scaling, S/N degradation slopes, Lorentz angle values, and the alpha parameter are fits to observed data and are presented as characterizations, not as predictions of those same data. The APV25 preamplifier saturation model is compared against independent data (early-2016 runs) and the VFP remedy is verified on later runs, so the explanation is not the thing being predicted. The HIP deadtime model uses a deadtime parameter, but the paper ties the resulting five-bunch-crossing deadtime to previous dedicated beam tests (Ref. [41]), and the underlying hit-efficiency measurement is direct rather than derived from the model. The end-of-life projection of about 1.5% inoperable modules at 500 fb-1 does rely on FLUKA fluence and annealing assumptions, and the paper itself reports a ~20% underestimate of leakage current in TIB/TOB and underestimated reverse annealing; however, this is an acknowledged model-uncertainty and extrapolation-risk issue, not a circular reduction. The projection does not use the 1.5% figure as an input, nor does it define any fitted parameter in terms of the projected outcome. The only self-citations are contextual references to prior CMS detector descriptions and projections; none is used as an unverified load-bearing theorem. Thus no step in the paper's argument reduces by construction to its own inputs.

Assumptions & free parameters 7 free parameters · 5 assumptions · 0 invented entities

This is an experimental characterization paper, so no invented entities are introduced. The free parameters are empirical constants from fits (noise scaling, S/N slopes, alpha parameter, HIP deadtime) and a calibration normalization, all clearly defined in the text. The key axioms are the validity of the FLUKA fluence simulation and the radiation damage annealing models, together with standard physics of energy loss in silicon. These are domain assumptions, not ad hoc constructions, and they are stated openly in Sections 5, 6, and 7.

free parameters (7)
  • ENC offset (ENCoffset) = 699 +/- 92 e, then 677 +/- 26 e plus 0.6 +/- 0.3 e per fb-1
    Linear fit of equivalent noise charge versus strip length in Section 4.2, Eqs. (1) and (2).
  • ENC slope (ENCslope) = 51.2 +/- 6.9 e/cm, central value 49.4 +/- 1.3 e/cm
    Slope of the same noise scaling fit, Eqs. (1) and (3).
  • S/N degradation rate = 0.12 per fb-1 (thin), 0.14 per fb-1 (thick)
    Linear fits to S/N versus integrated luminosity in Section 6.5, Figure 29, extrapolated to 500 fb-1.
  • alpha (current-related damage rate) = (3.5 +/- 0.1) x 10^-17 A/cm
    Linear fit of leakage current per volume scaled to +20 C versus fluence, Section 7.2.1, Figure 45.
  • HIP deadtime = 5 bunch crossings
    Parameter in the HIP inefficiency model, Section 6.8.3, Figure 40; compatible with beam tests in Ref. [41].
  • APV25 preamplifier discharge time constant tau = varies with VFP setting and temperature (Fig. 24), below 1 microsecond for VFP=0
    Used in the APV25 saturation model, Section 6.3, to simulate the reduced charge response in early 2016 data.
  • Signal equalization gain factor G = normalized to 300 ADC counts/mm
    Chosen calibration constant in Section 6.6 used to equalize cluster charge across the tracker; affects dE/dx and cluster charge monitoring.
assumptions (5)
  • domain assumption FLUKA simulation of the CMS geometry provides an accurate mapping from delivered luminosity to 1 MeV neutron equivalent fluence at each module position
    Used throughout Section 7 to convert luminosity to fluence (Fig. 45, Fig. 52) and to project end-of-life damage; if the fluence is biased, the alpha parameter and all projections shift.
  • domain assumption Radiation damage in silicon sensors is described by the NIEL hypothesis with current-related damage rate alpha, plus annealing models for leakage current and depletion voltage
    Invoked in Sections 3 and 7.2.1 to interpret leakage current and depletion voltage measurements and to simulate their evolution.
  • standard math Energy loss of charged particles in thin silicon follows a Landau distribution, and the Bethe-Bloch formula describes mean energy loss
    Used in Sections 6.5, 6.8, and 6.10 for signal-to-noise fits, hit efficiency measurements, and dE/dx particle identification.
  • domain assumption The GEANT4-based CMS simulation with the digitization steps described in Section 5 (pulse shape, noise, pileup, cross talk) models the strip tracker response
    The simulation is used in Section 6 to compare cluster charge and efficiency with data, and in Section 6.3 to model APV25 saturation.
  • domain assumption The cluster-size minimum as a function of track incidence angle measures the Lorentz angle (method of Ref. [39])
    Section 6.7 uses this method to measure Lorentz angle and to apply hit position corrections.

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Cite this review

Pith. "Pith review of Operation and performance of the CMS silicon strip tracker with proton-proton collisions at the CERN LHC." pith.science (2026). https://pith.science/paper/3FWDS5V5

@misc{pith2026250617195,
  author       = {Pith},
  title        = {Pith review of: Operation and performance of the CMS silicon strip tracker with proton-proton collisions at the CERN LHC},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/3FWDS5V5}},
  note         = {Machine review of arXiv:2506.17195}
}
read the original abstract

Salient aspects of the commissioning, calibration, and performance of the CMS silicon strip tracker are discussed, drawing on experience during operation with proton-proton collisions delivered by the CERN LHC. The data were obtained with a variety of luminosities. The operating temperature of the strip tracker was changed several times during this period and results are shown as a function of temperature in several cases. Details of the system performance are presented, including occupancy, signal-to-noise ratio, Lorentz angle, and single-hit spatial resolution. Saturation effects in the APV25 readout chip preamplifier observed during early Run 2 are presented, showing the effect on various observables and the subsequent remedy. Studies of radiation effects on the strip tracker are presented both for the optical readout links and the silicon sensors. The observed effects are compared to simulation, where available, and they generally agree well with expectations.

Figures

Figures reproduced from arXiv: 2506.17195 by the authors.

Figure 1
Figure 1. Peak luminosity delivered to CMS during stable pp collisions for 2010–2012 and [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. An r-z view of one quarter of the CMS silicon strip tracker. Layers with stereo mod￾ules (details are given in the main text) are drawn as blue lines, layers with single modules as red lines. The Phase-1 pixel detector, installed in 2017, is shown in green. TEC also contain stereo modules. The modules in the TID and the TEC are wedge-shaped with the strips pointing radially outwards from the nominal beam line to ena… view at source ↗
Figure 3
Figure 3. Overview of the control and readout scheme of the SST. [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figures from the paper (52 more)
Figure 4
Figure 4. Figure 4: Module types of the SST. detector locations, as well as the number of APV25 chips per module is given in [PITH_FULL_IMAGE:figures/full_fig_p007_4.png]
Figure 5
Figure 5. Figure 5: Functional schematic of a single channel of the APV25 chip. [PITH_FULL_IMAGE:figures/full_fig_p008_5.png]
Figure 6
Figure 6. Figure 6: Example of an APV25 chip output signal. A data frame consists of a 3-bit start-of [PITH_FULL_IMAGE:figures/full_fig_p009_6.png]
Figure 7
Figure 7. Figure 7: Tracker map where each silicon module is represented by a rectangle in the barrel and [PITH_FULL_IMAGE:figures/full_fig_p012_7.png]
Figure 8
Figure 8. Figure 8: High-resolution time domain capture of the tick marks from two APV25 chips (1 laser) [PITH_FULL_IMAGE:figures/full_fig_p014_8.png]
Figure 9
Figure 9. Figure 9: Illustration of pulse modulation by the LLD (left) and visualization of the bias setting [PITH_FULL_IMAGE:figures/full_fig_p014_9.png]
Figure 10
Figure 10. Figure 10: Chosen gain settings at different operating temperatures. The expected migration to [PITH_FULL_IMAGE:figures/full_fig_p015_10.png]
Figure 11
Figure 11. Figure 11: Example distributions of tick heights for each of the four laser driver gain settings for [PITH_FULL_IMAGE:figures/full_fig_p016_11.png]
Figure 12
Figure 12. Figure 12: Noise measured in the optical link chain during optical link setup runs at temper [PITH_FULL_IMAGE:figures/full_fig_p017_12.png]
Figure 13
Figure 13. Figure 13: Equivalent noise charge as a function of the strip length. [PITH_FULL_IMAGE:figures/full_fig_p017_13.png]
Figure 14
Figure 14. Figure 14: Offsets (left) and slopes (right) as a function of the integrated luminosity, derived [PITH_FULL_IMAGE:figures/full_fig_p018_14.png]
Figure 15
Figure 15. Figure 15: Left: average delay adjustment relative to the original sampling point for each layer [PITH_FULL_IMAGE:figures/full_fig_p019_15.png]
Figure 16
Figure 16. Figure 16: Material budget in units of radiation length (left) and interaction length (right) as [PITH_FULL_IMAGE:figures/full_fig_p020_16.png]
Figure 17
Figure 17. Figure 17: Simulated APV25 pulse shape (deconvolution mode) in the CMS simulation soft [PITH_FULL_IMAGE:figures/full_fig_p021_17.png]
Figure 18
Figure 18. Figure 18: Simulated and measured cluster charge normalized with the track path length for [PITH_FULL_IMAGE:figures/full_fig_p022_18.png]
Figure 19
Figure 19. Figure 19: Path length ℓ of a particle crossing a detector of thickness d at an angle θ. a second consecutive bad strip is encountered the search is terminated. A cluster candidate is retained if the summed signal of all strips in the cluster candidate is larger than five times …
Figure 20
Figure 20. Figure 20: Example of a signal-to-noise distribution from the TOB recorded during 2018 at an [PITH_FULL_IMAGE:figures/full_fig_p024_20.png]
Figure 21
Figure 21. Figure 21: View of the SST mean strip occupancy in the [PITH_FULL_IMAGE:figures/full_fig_p025_21.png]
Figure 22
Figure 22. Figure 22: Positions of the defects within the SST at the module level at the end of 2017. Dis [PITH_FULL_IMAGE:figures/full_fig_p026_22.png]
Figure 23
Figure 23. Figure 23: Fraction of bad channels as a function of the delivered LHC integrated luminosity. [PITH_FULL_IMAGE:figures/full_fig_p027_23.png]
Figure 24
Figure 24. Figure 24: Simulated discharge behavior of the APV25 preamplifier for different temperatures [PITH_FULL_IMAGE:figures/full_fig_p028_24.png]
Figure 25
Figure 25. Figure 25: Left: cluster charge distribution for clusters on reconstructed particle tracks in the [PITH_FULL_IMAGE:figures/full_fig_p029_25.png]
Figure 26
Figure 26. Figure 26: Tracking efficiency estimated using a tag-and-probe method as a function of the [PITH_FULL_IMAGE:figures/full_fig_p029_26.png]
Figure 27
Figure 27. Figure 27: Evolution of the cluster charge normalized to unit length as a function of the inte [PITH_FULL_IMAGE:figures/full_fig_p030_27.png]
Figure 28
Figure 28. Figure 28: Signal-to-noise ratio for clusters on reconstructed particle tracks in TOB layer 1 [PITH_FULL_IMAGE:figures/full_fig_p030_28.png]
Figure 29
Figure 29. Figure 29: Signal-to-noise ratio as a function of the integrated luminosity for modules from [PITH_FULL_IMAGE:figures/full_fig_p031_29.png]
Figure 30
Figure 30. Figure 30: The distribution of the charge normalized to the path length after the tick mark [PITH_FULL_IMAGE:figures/full_fig_p032_30.png]
Figure 31
Figure 31. Figure 31: Cluster charge normalized to the path length after the offline calibration for the SST [PITH_FULL_IMAGE:figures/full_fig_p033_31.png]
Figure 32
Figure 32. Figure 32: Illustration of the shift due to the Lorentz force along the sensitive coordinate [PITH_FULL_IMAGE:figures/full_fig_p033_32.png]
Figure 33
Figure 33. Figure 33: Lorentz angle measured at the end of Run 2 for the different SST layers of the TIB [PITH_FULL_IMAGE:figures/full_fig_p034_33.png]
Figure 34
Figure 34. Figure 34: Evolution of the Lorentz angle during Run 2, for modules with strips oriented along [PITH_FULL_IMAGE:figures/full_fig_p034_34.png]
Figure 35
Figure 35. Figure 35: Hit efficiency for the various layers of the SST at the end of Run 2. Known faulty [PITH_FULL_IMAGE:figures/full_fig_p035_35.png]
Figure 36
Figure 36. Figure 36: Hit efficiency as a function of the instantaneous luminosity for the modules in the [PITH_FULL_IMAGE:figures/full_fig_p036_36.png]
Figure 37
Figure 37. Figure 37: Hit efficiency for different layers in the TIB (left) and TOB (right) as a function of the [PITH_FULL_IMAGE:figures/full_fig_p036_37.png]
Figure 38
Figure 38. Figure 38: ADC counts of the six APV25 chips in a TIB module during a collision in 2016. The [PITH_FULL_IMAGE:figures/full_fig_p037_38.png]
Figure 39
Figure 39. Figure 39: Average probability of HIP event occurrence per pp interaction (left) and normalized [PITH_FULL_IMAGE:figures/full_fig_p038_39.png]
Figure 40
Figure 40. Figure 40: Evolution of the hit efficiency as a function of bunch number within the train for TIB [PITH_FULL_IMAGE:figures/full_fig_p038_40.png]
Figure 41
Figure 41. Figure 41: Single-hit resolution as a function of the strip pitch (left) and for different detector [PITH_FULL_IMAGE:figures/full_fig_p039_41.png]
Figure 42
Figure 42. Figure 42: Energy loss measurement in the SST during LHC Run 2. Expected losses for pion, [PITH_FULL_IMAGE:figures/full_fig_p040_42.png]
Figure 43
Figure 43. Figure 43: Laser driver threshold increase versus time for laser drivers in TIB (upper) and [PITH_FULL_IMAGE:figures/full_fig_p042_43.png]
Figure 44
Figure 44. Figure 44: Thermal runaway observed in one power group of the TIB during the 2017 running. [PITH_FULL_IMAGE:figures/full_fig_p044_44.png]
Figure 45
Figure 45. Figure 45: Leakage current per unit volume and integrated luminosity, scaled to [PITH_FULL_IMAGE:figures/full_fig_p044_45.png]
Figure 46
Figure 46. Figure 46: Leakage current and temperature measured by the DCU compared with simulation [PITH_FULL_IMAGE:figures/full_fig_p045_46.png]
Figure 47
Figure 47. Figure 47: Silicon temperature as measured by the DCUs of the individual modules after [PITH_FULL_IMAGE:figures/full_fig_p046_47.png]
Figure 48
Figure 48. Figure 48: Left: leakage current as measured by the DCUs of the individual modules after [PITH_FULL_IMAGE:figures/full_fig_p046_48.png]
Figure 49
Figure 49. Figure 49: Leakage current for each layer scaled to unit volume and 0 [PITH_FULL_IMAGE:figures/full_fig_p047_49.png]
Figure 50
Figure 50. Figure 50: Example of the determination of the full-depletion voltage using the intersection of [PITH_FULL_IMAGE:figures/full_fig_p048_50.png]
Figure 51
Figure 51. Figure 51: Left: mean cluster width as a function of the sensor bias voltage for one module [PITH_FULL_IMAGE:figures/full_fig_p049_51.png]
Figure 52
Figure 52. Figure 52: Left: change of the full-depletion voltage in different tracker layers as a function of [PITH_FULL_IMAGE:figures/full_fig_p050_52.png]
Figure 53
Figure 53. Figure 53: Tracker map of predicted leakage current at the end of life of the SST, where each sil [PITH_FULL_IMAGE:figures/full_fig_p051_53.png]
Figure 54
Figure 54. Figure 54: Fraction of modules affected by thermal runaway as a function of the integrated [PITH_FULL_IMAGE:figures/full_fig_p051_54.png]
Figure 55
Figure 55. Figure 55: Tracker map of predicted full-depletion voltage at the end of life of the SST, where [PITH_FULL_IMAGE:figures/full_fig_p052_55.png]

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