27 research outputs found
Modeling of Surface Damage at the Si/SiO-interface of Irradiated MOS-capacitors
Surface damage caused by ionizing radiation in SiO passivated silicon
particle detectors consists mainly of the accumulation of a positively charged
layer along with trapped-oxide-charge and interface traps inside the oxide and
close to the Si/SiO-interface. High density positive interface net charge
can be detrimental to the operation of a multi-channel -on- sensor since
the inversion layer generated under the Si/SiO-interface can cause loss of
position resolution by creating a conduction channel between the electrodes. In
the investigation of the radiation-induced accumulation of oxide charge and
interface traps, a capacitance-voltage characterization study of n/-
and -irradiated Metal-Oxide-Semiconductor (MOS) capacitors showed that
close agreement between measurement and simulation were possible when oxide
charge density was complemented by both acceptor- and donor-type deep interface
traps with densities comparable to the oxide charges. Corresponding inter-strip
resistance simulations of a -on- sensor with the tuned oxide charge
density and interface traps show close agreement with experimental results. The
beneficial impact of radiation-induced accumulation of deep interface traps on
inter-electrode isolation may be considered in the optimization of the
processing parameters of isolation implants on -on- sensors for the
extreme radiation environments.Comment: Corresponding author: T. Peltola. 24 pages, 17 figures, 6 table
Charge Collection and Electrical Characterization of Neutron Irradiated Silicon Pad Detectors for the CMS High Granularity Calorimeter
The replacement of the existing endcap calorimeter in the Compact Muon
Solenoid (CMS) detector for the high-luminosity LHC (HL-LHC), scheduled for
2027, will be a high granularity calorimeter. It will provide detailed
position, energy, and timing information on electromagnetic and hadronic
showers in the immense pileup of the HL-LHC. The High Granularity Calorimeter
(HGCAL) will use 120-, 200-, and 300- thick silicon (Si) pad
sensors as the main active material and will sustain 1-MeV neutron equivalent
fluences up to about . In order
to address the performance degradation of the Si detectors caused by the
intense radiation environment, irradiation campaigns of test diode samples from
8-inch and 6-inch wafers were performed in two reactors. Characterization of
the electrical and charge collection properties after irradiation involved both
bulk polarities for the three sensor thicknesses. Since the Si sensors will be
operated at -30 C to reduce increasing bulk leakage current with
fluence, the charge collection investigation of 30 irradiated samples was
carried out with the infrared-TCT setup at -30 C. TCAD simulation
results at the lower fluences are in close agreement with the experimental
results and provide predictions of sensor performance for the lower fluence
regions not covered by the experimental study. All investigated sensors display
60 or higher charge collection efficiency at their respective highest
lifetime fluences when operated at 800 V, and display above 90 at the
lowest fluence, at 600 V. The collected charge close to the fluence of
exceeds 1 fC at voltages
beyond 800 V.Comment: 36 pages, 34 figure
The CMS Phase-1 pixel detector upgrade
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.Peer reviewe
Response of a CMS HGCAL silicon-pad electromagnetic calorimeter prototype to 20-300 GeV positrons
The Compact Muon Solenoid Collaboration is designing a new high-granularity
endcap calorimeter, HGCAL, to be installed later this decade. As part of this
development work, a prototype system was built, with an electromagnetic section
consisting of 14 double-sided structures, providing 28 sampling layers. Each
sampling layer has an hexagonal module, where a multipad large-area silicon
sensor is glued between an electronics circuit board and a metal baseplate. The
sensor pads of approximately 1 cm are wire-bonded to the circuit board and
are readout by custom integrated circuits. The prototype was extensively tested
with beams at CERN's Super Proton Synchrotron in 2018. Based on the data
collected with beams of positrons, with energies ranging from 20 to 300 GeV,
measurements of the energy resolution and linearity, the position and angular
resolutions, and the shower shapes are presented and compared to a detailed
Geant4 simulation
Precision measurement of the structure of the CMS inner tracking system using nuclear interactions
A search has been performed for heavy resonances decaying to ZZ or ZW in 2l2q final states, with two charged leptons (l = e, mu) produced by the decay of a Z boson, and two quarks produced by the decay of a W or Z boson. The analysis is sensitive to resonances with masses in the range from 400 to 4500 GeV. Two categories are defined based on the merged or resolved reconstruction of the hadronically decaying vector boson, optimized for high- and low-mass resonances, respectively. The search is based on data collected during 2016 by the CMS experiment at the LHC in proton-proton collisions with a center-of-mass energy of root s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1). No excess is observed in the data above the standard model background expectation. Upper limits on the production cross section of heavy, narrow spin-1 and spin-2 resonances are derived as a function of the resonance mass, and exclusion limits on the production of W' bosons and bulk graviton particles are calculated in the framework of the heavy vector triplet model and warped extra dimensions, respectively.A search has been performed for heavy resonances decaying to ZZ or ZW in 2l2q final states, with two charged leptons (l = e, mu) produced by the decay of a Z boson, and two quarks produced by the decay of a W or Z boson. The analysis is sensitive to resonances with masses in the range from 400 to 4500 GeV. Two categories are defined based on the merged or resolved reconstruction of the hadronically decaying vector boson, optimized for high- and low-mass resonances, respectively. The search is based on data collected during 2016 by the CMS experiment at the LHC in proton-proton collisions with a center-of-mass energy of root s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1). No excess is observed in the data above the standard model background expectation. Upper limits on the production cross section of heavy, narrow spin-1 and spin-2 resonances are derived as a function of the resonance mass, and exclusion limits on the production of W' bosons and bulk graviton particles are calculated in the framework of the heavy vector triplet model and warped extra dimensions, respectively.The structure of the CMS inner tracking system has been studied using nuclear interactions of hadrons striking its material. Data from proton-proton collisions at a center-of-mass energy of 13 TeV recorded in 2015 at the LHC are used to reconstruct millions of secondary vertices from these nuclear interactions. Precise positions of the beam pipe and the inner tracking system elements, such as the pixel detector support tube, and barrel pixel detector inner shield and support rails, are determined using these vertices. These measurements are important for detector simulations, detector upgrades, and to identify any changes in the positions of inactive elements.Peer reviewe
Experimental study of different silicon sensor options for the upgrade of the CMS Outer Tracker
During the high-luminosity phase of the LHC (HL-LHC), planned to start in 2027, the accelerator is expected to deliver an instantaneous peak luminosity of up to 7.5×1034 cm-2 s-1. A total integrated luminosity of 0300 or even 0400 fb-1 is foreseen to be delivered to the general purpose detectors ATLAS and CMS over a decade, thereby increasing the discovery potential of the LHC experiments significantly. The CMS detector will undergo a major upgrade for the HL-LHC, with entirely new tracking detectors consisting of an Outer Tracker and Inner Tracker. However, the new tracking system will be exposed to a significantly higher radiation than the current tracker, requiring new radiation-hard sensors. CMS initiated an extensive irradiation and measurement campaign starting in 2009 to systematically compare the properties of different silicon materials and design choices for the Outer Tracker sensors. Several test structures and sensors were designed and implemented on 18 different combinations of wafer materials, thicknesses, and production technologies. The devices were electrically characterized before and after irradiation with neutrons, and with protons of different energies, with fluences corresponding to those expected at different radii of the CMS Outer Tracker after 0300 fb-1. The tests performed include studies with β sources, lasers, and beam scans. This paper compares the performance of different options for the HL-LHC silicon sensors with a focus on silicon bulk material and thickness
Beam test performance of prototype silicon detectors for the Outer Tracker for the Phase-2 Upgrade of CMS
The DAQ and control system for the CMS Phase-1 pixel detector upgrade
In 2017 a new pixel detector was installed in the CMS detector. This so-called Phase-1 pixel detector features four barrel layers in the central region and three disks per end in the forward regions. The upgraded pixel detector requires an upgraded data acquisition (DAQ) system to accept a new data format and larger event sizes. A new DAQ and control system has been developed based on a combination of custom and commercial microTCA parts. Custom mezzanine cards on standard carrier cards provide a front-end driver for readout, and two types of front-end controller for configuration and the distribution of clock and trigger signals. Before the installation of the detector the DAQ system underwent a series of integration tests, including readout of the pilot pixel detector, which was constructed with prototype Phase-1 electronics and operated in CMS from 2015 to 2016, quality assurance of the CMS Phase-1 detector during its assembly, and testing with the CMS Central DAQ. This paper describes the Phase-1 pixel DAQ and control system, along with the integration tests and results. A description of the operational experience and performance in data taking is included
The DAQ and control system for the CMS Phase-1 pixel detector upgrade
Abstract: In 2017 a new pixel detector was installed in the CMS detector. This so-called Phase-1 pixel detector features four barrel layers in the central region and three disks per end in the forward regions. The upgraded pixel detector requires an upgraded data acquisition (DAQ) system to accept a new data format and larger event sizes. A new DAQ and control system has been developed based on a combination of custom and commercial microTCA parts. Custom mezzanine cards on standard carrier cards provide a front-end driver for readout, and two types of front-end controller for configuration and the distribution of clock and trigger signals. Before the installation of the detector the DAQ system underwent a series of integration tests, including readout of the pilot pixel detector, which was constructed with prototype Phase-1 electronics and operated in CMS from 2015 to 2016, quality assurance of the CMS Phase-1 detector during its assembly, and testing with the CMS Central DAQ. This paper describes the Phase-1 pixel DAQ and control system, along with the integration tests and results. A description of the operational experience and performance in data taking is included