Silicon detectors are expected to experience an unprecedented radiation flux in the future upgrades of the detectors at the Large Hadron Collider (LHC). The challenging radiation environment of these ...experiments will severely affect the performance of such detectors, degrading their detection capabilities and imposing severe operational conditions. The modeling of the detectors through Monte Carlo simulation represents a necessary step for the detailed understanding of the silicon detector performance before and after radiation damage; also for setting up optimized design rules aiming to mitigate the detrimental effect of the radiation damage. In the present work, a comparison of simulation results, obtained from- Technology Computer-Aided Design (TCAD) simulation software: Silvaco and Synopsys- used to predict silicon detectors performance, is presented. The effects of radiation damage are incorporated in the TCADs, using an effective multiple traps model. A systematic study of the sensitivity of the silicon detector's macroscopic parameters to the modeling of traps is performed. The simulation results for static electrical parameters, such as the leakage current and the full depletion voltage, obtained by the TCADs are presented and compared.
The CMS Phase-1 pixel detector upgrade Lowette, S.; Moortgat, S.; Deng, W. ...
Journal of instrumentation,
02/2021, Letnik:
16, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The CMS detector at the CERN LHC features a silicon pixel detector as its innermost subdetector. The original CMS pixel detector has been replaced with an upgraded pixel system (CMS Phase-1 pixel ...detector) in the extended year-end technical stop of the LHC in 2016/2017. The upgraded CMS pixel detector is designed to cope with the higher instantaneous luminosities that have been achieved by the LHC after the upgrades to the accelerator during the first long shutdown in 2013–2014. Compared to the original pixel detector, the upgraded detector has a better tracking performance and lower mass with four barrel layers and three endcap disks on each side to provide hit coverage up to an absolute value of pseudorapidity of 2.5. This paper describes the design and construction of the CMS Phase-1 pixel detector as well as its performance from commissioning to early operation in collision data-taking.
The TOTEM detector at LHC Antchev, G.; Aspell, P.; Atanassov, I. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2010, Letnik:
617, Številka:
1
Journal Article
Recenzirano
The TOTEM experiment, small in size compared to the others at the LHC, is dedicated to the measurement of the total proton–proton cross-sections with a luminosity-independent method and to the study ...of elastic and diffractive scattering at the LHC. To achieve optimum forward coverage for charged particles emitted by the pp collisions in the IP5 interaction point, two tracking telescopes, T1 and T2, will be installed on each side in the pseudo-rapidity region between 3.1 and 6.5, and Roman Pot stations will be placed at distances of 147 and 220
m from IP5. The telescope closest to the interaction point (T1, centred at
z=9
m) consists of Cathode Strip Chambers (CSC), while the second one (T2, centred at 13.5
m), makes use of Gas Electron Multipliers (GEM). The proton detectors in the Roman Pots are silicon devices designed by TOTEM with the specific objective of reducing down to a few tens of microns the insensitive area at the edge. High efficiency as close as possible to the physical detector boundary is an essential feature. It maximizes the experimental acceptance for protons scattered elastically or interactively at polar angles down to a few micro-radians at IP5. To measure protons at the lowest possible emission angles, special beam optics have been conceived to optimize proton detection in terms of acceptance and resolution. The read-out of all TOTEM subsystems is based on the custom-developed digital VFAT chip with trigger capability.
The injection of a seed in a free-electron laser (FEL) amplifier reduces the saturation length and improves the longitudinal coherence. A cascaded FEL, operating in the high-gain harmonic-generation ...regime, allows us to extend the beneficial effects of the seed to shorter wavelengths. We report on the first operation of a high-gain harmonic-generation free-electron laser, seeded with harmonics generated in gas. The third harmonics of a Ti:sapphire laser, generated in a gas cell, has been amplified and up-converted to its second harmonic (λ(rad)=133 nm) in a FEL cascaded configuration based on a variable number of modulators and radiators. We studied the transition between coherent harmonic generation and superradiant regime, optimizing the laser performances with respect to the number of modulators and radiators.
Abstract
The Large Hadron Collider at CERN will undergo an upgrade in
order to increase its luminosity to
7.5 × 10
34
cm
-2
s
-1
. The increased luminosity
during this High-Luminosity running phase, ...starting around 2029,
means a higher rate of proton-proton interactions, hence a larger
ionizing dose and particle fluence for the detectors. The current
tracking system of the CMS experiment will be fully replaced in
order to cope with the new operating conditions. Prototype planar
pixel sensors for the CMS Inner Tracker with square
50 μm × 50 μm and rectangular
100 μm × 25 μm pixels read out by the
RD53A chip were characterized in the lab and at the DESY-II testbeam
facility in order to identify designs that meet the requirements of
CMS during the High-Luminosity running phase. A spatial resolution
of approximately 3.4 μm (2 μm) is obtained using the
modules with 50 μm × 50 μm
(100 μm × 25 μm) pixels at the optimal
angle of incidence before irradiation. After irradiation to a 1 MeV
neutron equivalent fluence of
Φ
eq
= 5.3 × 10
15
cm
-2
, a resolution of
9.4 μm is achieved at a bias voltage of 800 V using a module
with 50 μm × 50 μm pixel size. All modules
retain a hit efficiency in excess of 99% after irradiation to
fluences up to 2.1 × 10
16
cm
-2
. Further studies of
the electrical properties of the modules, especially crosstalk, are
also presented in this paper.
Abstract
The CMS Inner Tracker, made of silicon pixel modules, will
be entirely replaced prior to the start of the High Luminosity LHC
period. One of the crucial components of the new Inner Tracker
...system is the readout chip, being developed by the RD53
Collaboration, and in particular its analogue front-end, which
receives the signal from the sensor and digitizes it. Three
different analogue front-ends (Synchronous, Linear, and
Differential) were designed and implemented in the RD53A
demonstrator chip. A dedicated evaluation program was carried out to
select the most suitable design to build a radiation tolerant pixel
detector able to sustain high particle rates with high efficiency
and a small fraction of spurious pixel hits. The test results showed
that all three analogue front-ends presented strong points, but also
limitations. The Differential front-end demonstrated very low noise,
but the threshold tuning became problematic after
irradiation. Moreover, a saturation in the preamplifier feedback
loop affected the return of the signal to baseline and thus
increased the dead time. The Synchronous front-end showed very good
timing performance, but also higher noise. For the Linear front-end
all of the parameters were within specification, although this
design had the largest time walk. This limitation was addressed and
mitigated in an improved design. The analysis of the advantages and
disadvantages of the three front-ends in the context of the CMS
Inner Tracker operation requirements led to the selection of the
improved design Linear front-end for integration in the final CMS
readout chip.
Abstract
The Large Hadron Collider (LHC) at CERN will undergo major
upgrades to increase the instantaneous luminosity up to
5–7.5×10
34
cm
-2
s
-1
. This High Luminosity
upgrade of the LHC (HL-LHC) ...will deliver a total of
3000–4000 fb
-1
of proton-proton collisions at a
center-of-mass energy of 13–14 TeV. To cope with these
challenging environmental conditions, the strip tracker of the CMS
experiment will be upgraded using modules with two closely-spaced
silicon sensors to provide information to include tracking in the
Level-1 trigger selection. This paper describes the performance, in
a test beam experiment, of the first prototype module based on the
final version of the CMS Binary Chip front-end ASIC before and after
the module was irradiated with neutrons. Results demonstrate that
the prototype module satisfies the requirements, providing efficient
tracking information, after being irradiated with a total fluence
comparable to the one expected through the lifetime of the
experiment.
The increase of intracellular Ca
2+
concentration, produced principally by its influx through the L-type Ca
2+
channels, is one of the major contributors to the ischemia-reperfusion injury. The ...inhibition of those channels in different experimental models was effective to ameliorate the post-ischemic damage. However, at a clinical level, the results were contradictory. Recent results of our group obtained in an ¨
ex vivo
¨ heart model demonstrated that a chemical derived from acetazolamide, the N-methylacetazolamide (NMA) protected the heart against ischemia-reperfusion injury, diminishing the infarct size and improving the post-ischemic recovery of myocardial function and mitochondrial dynamic. A significant inhibitory action on L-type Ca
2+
channels was also detected after NMA treatment, suggesting this action as responsible for the beneficial effects on myocardium exerted by this compound. Although these results were promising, the effectiveness of NMA in the treatment of ischemic heart disease in humans as well as the advantages or disadvantages in comparison to the classic calcium antagonists needs to be investigated.
We present the experimental demonstration of a new scheme for the generation of ultrashort pulse trains based on free-electron-laser (FEL) emission from a multipeaked electron energy distribution. ...Two electron beamlets with energy difference larger than the FEL parameter ρ have been generated by illuminating the cathode with two ps-spaced laser pulses, followed by a rotation of the longitudinal phase space by velocity bunching in the linac. The resulting self-amplified spontaneous emission FEL radiation, measured through frequency-resolved optical gating diagnostics, reveals a double-peaked spectrum and a temporally modulated pulse structure.
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