The tracking detector of ATLAS, one of the experiments at the Large Hadron Collider (LHC), will be upgraded in 2024–2026 to cope with the challenging environment conditions of the High Luminosity LHC ...(HL-LHC). The LPNHE, in collaboration with FBK and INFN, has produced 130μm thick n−on−p silicon pixel sensors which can withstand the expected large particle fluences at HL-LHC, while delivering data at high rate with excellent hit efficiency. Such sensors were tested in beam before and after irradiation both at CERN-SPS and at DESY, and their performance are presented in this paper. Beam test data indicate that these detectors are suited for all the layers where planar sensors are foreseen in the future ATLAS tracker: hit-efficiency is greater than 97% for fluences of Φ≲7×1015neq∕cm2 and module power consumption is within the specified limits. Moreover, at a fluence of Φ=1.3×1016neq∕cm2, hit-efficiency is still as high as 88% and charge collection efficiency is about 30%.
The development of n-on-p “edgeless” planar pixel sensors being fabricated at FBK (Trento, Italy), aimed at the upgrade of the ATLAS Inner Detector for the High Luminosity phase of the Large Hadron ...Collider (HL-LHC), is reported. A characterizing feature of the devices is the reduced dead area at the edge, achieved by adopting the “active edge” technology, based on a deep etched trench, suitably doped to make an ohmic contact to the substrate. The project is presented, along with the active edge process, the sensor design for this first n-on-p production and a selection of simulation results, including the expected charge collection efficiency after radiation fluence of 1×1015neq/cm2 comparable to those expected at HL-LHC (about ten years of running, with an integrated luminosity of 3000fb−1) for the outer pixel layers. We show that, after irradiation and at a bias voltage of 500V, more than 50% of the signal should be collected in the edge region; this confirms the validity of the active edge approach.
► We conceive n-on-p edgeless planar silicon sensors. ► These sensors are aimed at the Phase-II of the ATLAS experiment. ► Simulations show sensors can be operated well in overdepletion. ► Simulations show the sensor capability to collect charge at the periphery. ► Simulations prove the above statements to be true even after irradiation.
For the high luminosity upgrade of the LHC at CERN, ATLAS is considering the addition of a High Granularity Timing Detector (HGTD) in front of the end cap and forward calorimeters at |z|=3.5 m and ...covering the region 2.4<|η|<4 to help reducing the effect of pile-up. The chosen sensors are arrays of 50μm thin Low Gain Avalanche Detectors (LGAD). This paper presents results on single LGAD sensors with a surface area of 1.3×1.3 mm2 and arrays with 2×2 pads with a surface area of 2×2 mm2 or 3×3 mm2 each and different implant doses of the p+ multiplication layer. They are obtained from data collected during a beam test campaign in autumn 2016 with a pion beam of 120 GeV energy at the CERN SPS. In addition to several quantities measured inclusively for each pad, the gain, efficiency and time resolution have been estimated as a function of the position of the incident particle inside the pad by using a beam telescope with a position resolution of few μm. Different methods to measure the time resolution are compared, yielding consistent results. The sensors with a surface area of 1.3×1.3 mm2 have a time resolution of about 40 ps for a gain of 20 and of about 27 ps for a gain of 50 and fulfil the HGTD requirements. Larger sensors have, as expected, a degraded time resolution. All sensors show very good efficiency and time resolution uniformity.
The radiation hardness of the AToM chips of the BaBar Silicon Vertex Tracker has been investigated by means of irradiation with photons from a /sup 60/Co source and 0.9 GeV electrons. The increase in ...noise and the decrease in gain of the amplifier have been measured as a function of the applied capacitive load and the absorbed dose. Different beam intensities have been used to study the effect of different dose rates to the AToM radiation damage. The chip digital functionalities have been tested up to a dose of 5.5 Mrads for the /sup 60/Co photons and 9 Mrads for the 0.9 GeV electrons. In addition a pedestal shift for the irradiated channels has been observed in the test with electrons but is not present in the irradiation with photons. This effect reproduces qualitatively the behavior observed since 2002 in the front-end electronics of the installed BaBar Silicon Vertex Tracker. After some investigation of the chip layout, this peculiar behavior could be associated to radiation damage in a well-identified component of the AToM. The results of the radiation tests are presented and used to extrapolate the lifetime of the installed detector and its performance in the next few years.
We report on bipolar NPN phototransistors fabricated at ITC-IRST on thick high-resistivity silicon substrates. The phototransistor emitter is composed of a phosphorus n+ implant, the base is a ...diffused high-energy boron implant, and the collector is the 600–800
μm thick silicon bulk, contacted on the backplane. We have studied the current amplification for two different doping profiles of the emitter, obtaining values of
β ranging from 60 to 3000. For various emitter and base configurations, we measured the static device characteristics and extracted the leakage currents and the base resistance, verifying the fundamental relationship between them and the total base capacitances. The use of such phototransistors to detect ionizing particles is exploited and discussed.
We have investigated the depletion voltage changes, leakage current increase and charge collection efficiency of a silicon microstrip detector identical to those used in the inner layers of the BABAR ...Silicon Vertex Tracker (SVT) after heavy nonuniform irradiation. A full SVT module with the front-end electronics connected has been irradiated with a 0.9 GeV electron beam up to a peak fluence of 3.5/spl times/10/sup 14/ e/sup -//cm/sup 2/, well beyond the level causing substrate type inversion. We have irradiated the silicon with a nonuniform profile having /spl sigma/=1.4 mm that simulates the conditions encountered in the BABAR experiment by the modules intersecting the horizontal machine plane. The position dependence of the charge collection properties and the depletion voltage have been investigated in detail using a 1060 nm LED and an innovative measuring technique based only on the digital output of the chip.
Lessons learned from the BaBar Silicon Vertex Tracker Calderini, Giovanni
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2005, Letnik:
541, Številka:
1
Journal Article
Recenzirano
The Silicon Vertex Tracker (SVT) of the BABAR experiment at the PEP-II asymmetric B factory consists of a five-layer double sided, AC coupled silicon microstrip detector. It represents a key element ...to measure with precision the decay position of B mesons, satisfying the severe constraints imposed by the accelerator design, in terms of geometry of the interaction region and conditions of operation. In the following paper, a critical review of the SVT general design and performance is made, with special attention to those details of the design and the assembly procedure that are considered a source of possible problems given the experience accumulated during the construction, the commissioning and the first 5 years of operation.
This work studies the feasibility of a new implementation of CMOS monolithic active pixel sensors (MAPS) for applications to charged particle tracking. As compared to standard three MOSFET MAPS, ...where the charge signal is readout by a source follower, the proposed front-end scheme relies upon a charge sensitive amplifier (CSA), embedded in the elementary pixel cell, to perform charge-to-voltage conversion. The area required for the integration of the front-end electronics is mostly provided by the collecting electrode, which consists of a deep n-type diffusion, available as a shielding frame for n-channel devices in deep submicron, triple well CMOS technologies. Based on the above concept, a chip, which includes several test structures differing in the sensitive element area, has been fabricated in a
0.13
μ
m
CMOS process. In this paper, the criteria underlying the design of the pixel level analog processor will be presented, together with some preliminary experimental results demonstrating the feasibility of the proposed approach.
We measure the total branching fraction of the flavor-changing neutral-current process B → X s ℓ + ℓ − , along with partial branching fractions in bins of dilepton and hadronic system ( X s ) mass, ...using a sample of 471 × 1 0 6 Υ ( 4 S ) → B ¯ B events recorded with the BABAR detector. The admixture of charged and neutral B mesons produced at PEP-II2 are reconstructed by combining a dilepton pair with 10 different X s final states. Extrapolating from a sum over these exclusive modes, we measure a lepton-flavor-averaged inclusive branching fraction B ( B → X s ℓ + ℓ − ) = 6.7 3 + 0.70 − 0.64 ( stat ) + 0.34 − 0.25 ( exp syst ) ± 0.50 ( model syst ) × 1 0 − 6 for m 2 ℓ + ℓ − > 0.1 GeV 2 / c 4 . Restricting our analysis exclusively to final states from which a decaying B meson's flavor can be inferred, we additionally report measurements of the direct C P asymmetry A C P in bins of dilepton mass; over the full dilepton mass range, we find A C P = 0.04 ± 0.11 ± 0.01 for a lepton-flavor-averaged sample.
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