This paper introduces a new concept of silicon radiation detector with intrinsic multiplication of the charge, called Low Gain Avalanche Detector (LGAD). These new devices are based on the standard ...Avalanche Photo Diodes (APD) normally used for optical and X-ray detection applications. The main differences to standard APD detectors are the low gain requested to detect high energy charged particles, and the possibility to have fine segmentation pitches: this allows fabrication of microstrip or pixel devices which do not suffer from the limitations normally found 1 in avalanche detectors. In addition, a moderate multiplication value will allow the fabrication of thinner devices with the same output signal of standard thick substrates.
The investigation of these detectors provides important indications on the ability of such modified electrode geometry to control and optimize the charge multiplication effect, in order to fully recover the collection efficiency of heavily irradiated silicon detectors, at reasonable bias voltage, compatible with the voltage feed limitation of the CERN High Luminosity Large Hadron Collider (HL-LHC) experiments 2. For instance, the inner most pixel detector layers of the ATLAS tracker will be exposed to fluences up to 2×10161MeVneq/cm2, while for the inner strip detector region fluences of 1×1015neq/cm2 are expected.
The gain implemented in the non-irradiated devices must retain some effect also after irradiation, with a higher multiplication factor with respect to standard structures, in order to be used in harsh environments such those expected at collider experiments.
Background People with developmental disabilities are at high risk for a limited participation in leisure activities. The aim of this study was to investigate the participation in, preference for ...and interest in leisure activities of young and adults with developmental disabilities, and to examine the factors associated with leisure activity.
Methods A cross‐sectional design was used with a convenience sample of 237 people aged 17 to 65, living in the community. Leisure participation was assessed with the Spanish version of Leisure Assessment Inventory. Percentages were calculated by types of activity, and repeated measures anovas were used to analyse the differences between types of activities, and mixed anovas to analyse the factors that explain differences in leisure activity participation, preference and interest.
Results Leisure social activities and recreation activities at home were mostly solitary and passive in nature and were identified as those being most commonly engaged in. Respondents expressed preference for more social and physical activity, and they were interested in trying out a large number of physical activities. Age and type of schooling determine participation in leisure activity. The results underscore the differences in leisure activity participation, preference and interest depending on the severity of the disability.
Conclusions The findings reveal interesting patterns of participation in leisure activities from the viewpoint of youngsters and adults with developmental disabilities. Leisure participation among people with developmental disabilities is likely to be more affected by environmental factors than by personal factors.
The ATLAS experiment is going to replace the current Inner Detector with an all new inner tracker (ITk) in the ATLAS detector for HL-LHC at CERN. Silicon strip detectors cover the outer layers of the ...barrel and the endcap sections. We have designed and fabricated a prototype single-sided n+-in-p AC-coupled silicon strip sensor for the outer barrel layer with long strips (LS), ATLAS17LS. It is of the maximum allowable size to fit in a 6-in. silicon wafer, with an outer dimension of 9.80(width)×9.76(length)cm2. The sensor features two rows of LS strip segments, 4.83 cm strip length per segment, a strip pitch of 75.5 μm, and a slim edge design. We have implemented technology for high voltage operation of up to 1000V, with a good signal collection after irradiation fluence of 5.6 × 1014neq∕cm2at the end of HL-LHC operation.
We had two objectives for the ATLAS17LS fabrication: qualification of the sensor design and fabrication quality, and providing an adequate number of the sensors for prototyping the building blocks of the strip detector. The sensors were fabricated in 3 batches by HPK with standard wafers from the foundry (320 μm physical thickness). Additional 10 sensors were fabricated with a thinner active thickness of 240 μm to investigate the influence of active thickness on charge collection. Another additional 5 sensors, with special passivation to investigate the influence of passivation on humidity sensitivity. The visual inspection of fabricated sensors revealed an inadequacy that the designed metal width of 10 μm was too narrow. The initial measurements by the vendor showed that the sensors fulfilled the specifications: onset voltages of Microdischarge VMD above the operation voltage VOP (700V for the 1st and 2nd batches; 500V for the 3rd batch, which has improved the yield), leakage currents of < 0.1μA/cm2 at VOP, full depletion voltages VFD< 330V, and rates of bad strips <<1%.
The improved radiation hardness of p-type Si detectors is hindered by the radiation-induced acceptor removal process, which is not fully understood yet. Through atomistic modeling of displacement ...damage and dopant interactions, we analyze the acceptor removal under neutron irradiation, providing physical insight into its microscopic origin. Our results show that the fast decay of the effective dopant concentration (Neff) at low irradiation fluences is due to B deactivation caused by Si self-interstitials. The intriguing increase of the acceptor removal parameter with the initial dopant concentration (Neff,0) is explained by the limited number of mobile Si self-interstitials that survive annihilation and clustering processes. The sublinear dependence of the removal parameter on Neff,0 is associated to the inhomogeneity of damage for low Neff,0 and the formation of B-interstitial clusters with several B atoms for high Neff,0. The presence of O and C modifies B deactivation mechanisms due to the key role of BiO defects and the trapping of vacancies and Si self-interstitials, but for the impurity concentrations analyzed in this work (O >> C) it has little effect on the overall amount of removed acceptors. At high irradiation fluences, the reported increase of Neff is attributed to the formation of defect-related deep acceptors. From the analysis of the defect concentrations resulting from neutron irradiation and the occupancy of small clusters with acceptor levels reported in literature, we point out the tetra-vacancy cluster as one of the main contributors to Neff with negative space charge.
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The planned upgrade of the Large Hadron Collider, the HL-LHC, requires the development of improved tracking silicon sensors for the main CERN experiments. These devices must fulfil the specifications ...established by the different detectors for the adverse HL-LHC working conditions, in order to guarantee the proper performance of the tracking systems during the lifetime of the experiments. In the framework of the ATLAS Inner-Tracker sensor Market Survey, a prototype strip sensor layout has been designed by the collaboration, and fabricated in 6-inch substrates by Infineon Technologies AG. This work presents a set of test structures included in this prototype, capable to evaluate key device and technological parameters as strip implant resistivity, bias resistance, coupling capacitance, surface currents, or the influence of the sensor edge design in device breakdown voltage. A complete analysis of these parameters before and after proton and gamma irradiations, up to fluences and doses similar to the ones expected in the future HL-LHC experiments, is presented. This study shows the relevance of microelectronic test structures in the development of technologies of tracking silicon sensors for High Energy Physics experiments.
The ATLAS collaboration is designing the all-silicon Inner Tracker (ITk) that will operate in the HL-LHC replacing the current design. The silicon microstrip sensors for the barrel and the endcap ...regions in the ITk are fabricated in 6 inch, p-type, float-zone wafers, where large-area strip sensor designs are laid out together with a number of miniature sensors. The radiation tolerance and specific system issues like the need for slim edge of 450 μm have been tested with square shaped sensors intended for the barrel part of the tracker. This work presents the design of the first full size silicon microstrip sensor for the endcap region with a slim edge of 450 μm. The strip endcaps will consist of several wheels with two layers of silicon strip sensors each. The strips have to lie along the azimuthal direction, apart from a small stereo angle rotation (20 mrad on each side, giving 40 mrad total) for measuring the second coordinate of tracks. This stereo angle is built into the strip layout of the sensor and, in order to avoid orphan strips, the sensor edges are inclined by the stereo angle. On top of this, the top and bottom edges are designed as arcs to have equal length strips. Together with the design of this new Stereo Annulus sensor, we will report on the initial measurements of the leakage current as a function of bias voltage, after dicing, and the depletion voltage.
Measuring the border of the active area on silicon strip sensors Santpur, S.; Blue, A.J.; Buttar, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2021, Letnik:
985, Številka:
C
Journal Article
Recenzirano
Odprti dostop
Silicon strip sensors for the ATLAS Inner Tracker (ITk) have been designed to provide reliable particle detection in the high-radiation environment of the High-Luminosity Large Hadron Collider. One ...important design criterion for their development is the minimization of inactive sensor areas, which affect the hermiticity of particle detection inside the detector. In previous measurements of ATLAS silicon strip sensors, the charge-collecting area of individual strip implants has been mapped and found to agree with the sensor strip pitch and strip length. For strip implants next to the sensor bias ring, the extent of their charge-collecting area towards the inactive sensor area was previously unknown, which limited the accuracy of both overall detector hermiticity estimates and the position resolution for particle detection at the sensor edge. Therefore, measurements were conducted to map the area of charge collection for sensor strips at the edge of the active sensor area using a micro-focused X-ray beam. This publication presents measurements showing the extent of charge collection in the edge strips of silicon strip sensors for two generations of ATLAS ITk strip sensor modules. The measurements confirmed that charge deposited in a strip implant that is neither connected nor grounded leads to capacitive coupling to the adjacent strip, where it is indistinguishable from a hit in that strip.
The ATLAS detector community is entering in the final stages of sensor development for the future upgrade of the Large Hadron Collider (LHC). An increase by an order of magnitude of the LHC ...luminosity, up to 1035 cm−2s−1, will lead to an increased radiation dose delivered to the detector, especially for the devices located in the Inner Tracker. In 2018, an experimental study of the damages induced by a beam-loss over silicon strip detectors was done in the High-Radiation to Materials facility at CERN. A progressive number of proton bunches was extracted from the CERN Super Proton Synchrotron, and focused directly over the strip sensor, in order to emulate the large amount of charge typically generated in a beam-loss failure. This work presents the results obtained during this experiment, showing that Punch-Through Protection effectively protects the AC-coupling capacitors of the silicon sensors from large charge accumulations, but still this scenario could induce damages on the read-out electronics.
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