The CMS Outer Tracker Upgrade for the HL-LHC Dierlamm, Alexander
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2019, Letnik:
924
Journal Article
Recenzirano
Odprti dostop
The LHC is planning an upgrade program, which will bring the luminosity to about 5−7×1034 cm−2 s−1 in 2026, with a goal of an integrated luminosity of 3000 fb−1 by the end of 2037. This High ...Luminosity LHC scenario, HL-LHC, will require a preparation program of the LHC detectors known as Phase-2 Upgrade. The current CMS Tracker is already running beyond design specifications and will not be able to cope with the HL-LHC radiation conditions. CMS will need a completely new Tracker in order to fully exploit the highly demanding operating conditions and the delivered luminosity. The new Outer Tracker system is designed to provide robust tracking as well as Level-1 trigger capabilities using closely spaced modules composed of silicon macro-pixel and/or strip sensors. Research and development activities are ongoing to explore options and develop module components and designs for the HL-LHC environment. The design choices for the CMS Outer Tracker Upgrade are discussed along with some highlights of the R&D activities.
Particle therapy is a well established clinical treatment of tumors. More than one hundred particle therapy centers are in operation world-wide. The advantage of using hadrons like protons or carbon ...ions as particles for tumor irradiation is the distinct peak in the depth-dependent energy deposition, which can be exploited to accurately deposit doses in the tumor cells. To guarantee this, high accuracy in monitoring and control of the particle beam is of the utmost importance. Before the particle beam enters the patient, it traverses a monitoring system which has to give fast feedback to the beam control system on position and dose rate of the beam while minimally interacting with the beam. The multi-wire chambers mostly used as beam position monitors have their limitations when a fast response time is required (drift time). Future developments such as MRI-guided ion beam therapy pose additional challenges for the beam monitoring system, such as tolerance of magnetic fields and acoustic noise (vibrations). Solid-state detectors promise to overcome these limitations and the higher resolution they offer can create additional benefits. This article presents the evaluation of an HV-CMOS detector for beam monitoring, provides results from feasibility studies in a therapeutic beam, and summarizes the concepts towards the final large-scale assembly and readout system.
This contribution summarizes an extensive simulation study of three different bias rail approaches for segmented strip and pixel sensors, comparing their charge collection efficiency and the maximum ...electric field in the bulk. Therefore a combined heavy ion and transient simulation was performed. By moving the interception point of the particle and integrating over the induced current at the pixel contacts and the backside, a spatial dependency of the charge collection efficiency (CCE) was obtained. The results show that a common p-stop configuration, where the bias rail is effectively shielded by the p+ implantation, leads to a constant CCE close to 100% along the sensor and the lowest maximal electric field in the bulk. The results have been utilized in the design process of a new macro-pixel prototype which is shown at the end of this contribution.
•TCAD simulations of bias rail approaches for segmented silicon sensors was performed.•A spatial dependency of the charge collection efficiency (CCE) was obtained.•Common p-stop configuration leads to a constant CCE close to 100%.•Common p-stop shows lowest maximum electric field in the bulk.
CMS Tracker upgrade issues and plans Dierlamm, Alexander
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2009, Letnik:
604, Številka:
1
Journal Article
Recenzirano
The LHC accelerator complex will undergo a programme of consolidation and upgrade of various components, with the goal of exceeding a peak luminosity of
10
34
cm
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2
s
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1
(original design figure) ...around the year 2012; to eventually reach values close to
10
35
cm
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2
s
-
1
. The increase in luminosity poses new challenges to the detector operation, both in terms of instantaneous and integrated particle rates. In CMS, the systems that have been identified as requiring substantial upgrades are the Tracker and the Level 1 trigger. The tracking system needs higher readout granularity and higher radiation tolerance, at the same time with reduced power dissipation and a smaller material budget, which are already limiting the performance of the present detector. The trigger system needs to include tracking information at Level 1, to maintain an acceptable rate without losing efficiency for physics channels. These requirements further complicate the design of a new Tracker detector and its readout architecture. This report describes the current status of our CMS Tracker upgrade activities.
In this work we address the effects of bulk and surface damages on detectors fabricated by Hamamatsu on standard float zone (FZ) p-type material with an active thickness of 290 µm or thinned to ...240 µm. In order to disentangle the effects of the two main radiation damage mechanisms, ionization effects and atomic displacement, the structures underwent two types of radiation: X-ray with doses from 0.05 to 70 Mrad (SiO2) and neutron in the range of 1−10 × 1014 neq/cm21MeV equivalent. The combined surface and bulk damage could be investigated in structures that underwent both types of irradiation. A wide set of measurements has been carried out on the test structures for a complete characterization.
The silicon sensors to be deployed in the next generation high energy physics experiments for operation in high luminosity scenarios, will require a high level of radiation tolerance. AC-coupled ...silicon strip sensors integrated with biasing poly-silicon resistors have been fabricated in collaboration with the Bharat Electronics Limited foundry using 4 inch n-type wafers in p-on-n configuration. Several sensors were irradiated with protons at different fluences at the Karlsruhe Cyclotron facility under the Advanced European Infrastructures for Detectors at Accelerators (AIDA) program. This paper reports on these radiation hardness study performed on the AC-coupled silicon sensors fabricated in India. The characterization comprises of electrical tests, including total current, voltage and strip scans and charge collection studies.
The discovery of a new boson with a mass of approximately 125 GeV in 2012 at the Large Hadron Collider1, 2, 3 has heralded a new era in understanding the nature of electroweak symmetry breaking and ...possibly completing the standard model of particle physics4, 5, 6, 7, 8, 9. Since the first observation in decays to γγ, WW and ZZ boson pairs, an extensive set of measurements of the mass10, 11 and couplings to W and Z bosons11, 12, 13, as well as multiple tests of the spin-parity quantum numbers10, 11, 13, 14, have revealed that the properties of the new boson are consistent with those of the long-sought agent responsible for electroweak symmetry breaking. An important open question is whether the new particle also couples to fermions, and in particular to down-type fermions, as the current measurements mainly constrain the couplings to the up-type top quark. Determination of the couplings to down-type fermions requires direct measurement of the corresponding Higgs boson decays, as recently reported by the Compact Muon Solenoid (CMS) experiment in the study of Higgs decays to bottom quarks15 and τ leptons16. Here, we report the combination of these two channels, which results in strong evidence for the direct coupling of the 125 GeV Higgs boson to down-type fermions, with an observed significance of 3.8 standard deviations, when 4.4 are expected.
P-on-n silicon strip sensors having multiple guard-ring structures have been developed for High Energy Physics applications. The study constitutes the optimization of the sensor design, and ...fabrication of AC-coupled, poly-silicon biased sensors of strip width of 30μm and strip pitch of 55μm. The silicon wafers used for the fabrication are of 4 inch n-type, having an average resistivity of 2–5 kΩ cm, with a thickness of 300μm. The electrical characterization of these detectors comprises of: (a) global measurements of total leakage current, and backplane capacitance; (b) strip and voltage scans of strip leakage current, poly-silicon resistance, interstrip capacitance, interstrip resistance, coupling capacitance, and dielectric current; and (c) charge collection measurements using ALiBaVa setup. The results of the same are reported here.
A tagging algorithm to identify jets that are significantly displaced from the proton-proton (pp) collision region in the CMS detector at the LHC is presented. Displaced jets can arise from the ...decays of long-lived particles (LLPs), which are predicted by several theoretical extensions of the standard model. The tagger is a multiclass classifier based on a deep neural network, which is parameterised according to the proper decay length cτ0 of the LLP. A novel scheme is defined to reliably label jets from LLP decays for supervised learning. Samples of pp collision data, recorded by the CMS detector at a centre-of-mass energy of 13 TeV, and simulated events are used to train the neural network. Domain adaptation by backward propagation is performed to improve the simulation modelling of the jet class probability distributions observed in pp collision data. The potential performance of the tagger is demonstrated with a search for long-lived gluinos, a manifestation of split supersymmetric models. The tagger provides a rejection factor of 10 000 for jets from standard model processes, while maintaining an LLP jet tagging efficiency of 30%-80% for gluinos with 1 mm≤cτ0≤ 10 m. The expected coverage of the parameter space for split supersymmetry is presented.
High-voltage particle detectors in commercial CMOS technologies are a detector family that allows implementation of low-cost, thin and radiation-tolerant detectors with a high time resolution. In the ...R/D phase of the development, a radiation tolerance of 1015neq/cm2, nearly 100% detection efficiency and a spatial resolution of about 3μm were demonstrated. Since 2011 the HV detectors have first applications: the technology is presently the main option for the pixel detector of the planned Mu3e experiment at PSI (Switzerland). Several prototype sensors have been designed in a standard 180nm HV CMOS process and successfully tested. Thanks to its high radiation tolerance, the HV detectors are also seen at CERN as a promising alternative to the standard options for ATLAS upgrade and CLIC. In order to test the concept, within ATLAS upgrade R/D, we are currently exploring an active pixel detector demonstrator HV2FEI4; also implemented in the 180nm HV process.
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