Measurements of the reverse current of highly irradiated silicon sensors to determine the effective energy and current related damage rate

The reverse current of irradiated silicon sensors leads to self heating of the sensor and degrades the signal to noise ratio of a detector. Precise knowledge of the expected reverse current during detector operation is crucial for planning and running experiments in High Energy Physics. The dependence of the reverse current on sensor temperature and irradiation fluence is parametrized by the effective energy and the current related damage rate, respectively. In this study 18 n-in-p mini silicon strip sensors from companies Hamamatsu Photonics and Micron Semiconductor Ltd. were deployed. Measurements of the reverse current for different bias voltages were performed at temperatures of −32 ° C, −27 ° C and −23 ° C. The sensors were irradiated with reactor neutrons in Ljubljana to fluences ranging from 2×1014neq∕cm2 to 2×1016neq∕cm2 . The measurements were performed directly after irradiation and after 10 and 30 days of room temperature annealing. The aim of the study presented in this paper is to investigate the reverse current of silicon sensors for high fluences of up to 2×1016neq∕cm2 and compare the measurements to the parametrization models

Development of a Tabletop Setup for the Transient Current Technique Using Two-Photon Absorption in Silicon Particle Detectors

The transient current technique (TCT) is widely used in the field of silicon particle detector development. So far, only laser wavelengths with a photon energy larger than or similar to the silicon bandgap (single photon absorption) were used. Recently, measurements using two-photon absorption (TPA) for silicon detector testing have been carried out for the first time. Excess carriers are only created at the focal point of the laser beam and thus resolution in all three spatial directions could be achieved. The resolution perpendicular to the incident laser beam could be increased roughly by a factor of 10. First measurements using this new method were performed at the Singular Laser Facility of Universidad del Pais Vasco (UPV)/Euskal Herriko Unibertzitatea (EHU). Following the initial success of the method, a compact TPA-TCT setup is under development. A first description of the setup and laser system is presented in this articleThis work was supported in part by the Spanish Ministry of Economy and Competitiveness (MINECO) under Grant FPA2013-48387-C6-1-P and in part by the Wolfgang Gentner Programme of the German Federal Ministry of Education and Research under Grant 05E15CH

The ABC130 barrel module prototyping programme for the ATLAS strip tracker

For the Phase-II Upgrade of the ATLAS Detector, its Inner Detector, consisting of silicon pixel, silicon strip and transition radiation sub-detectors, will be replaced with an all new 100 % silicon tracker, composed of a pixel tracker at inner radii and a strip tracker at outer radii. The future ATLAS strip tracker will include 11,000 silicon sensor modules in the central region (barrel) and 7,000 modules in the forward region (end-caps), which are foreseen to be constructed over a period of 3.5 years. The construction of each module consists of a series of assembly and quality control steps, which were engineered to be identical for all production sites. In order to develop the tooling and procedures for assembly and testing of these modules, two series of major prototyping programs were conducted: an early program using readout chips designed using a 250 nm fabrication process (ABCN-25) and a subsequent program using a follow-up chip set made using 130 nm processing (ABC130 and HCC130 chips). This second generation of readout chips was used for an extensive prototyping program that produced around 100 barrel-type modules and contributed significantly to the development of the final module layout. This paper gives an overview of the components used in ABC130 barrel modules, their assembly procedure and findings resulting from their tests.Comment: 82 pages, 66 figure

Silicon Detectors for the LHC Phase-II Upgrade and Beyond – RD50 Status Report

A large R&D; program has been underway to develop silicon sensors with sufficient radiation tolerance for LHC-Phase-II trackers and the next generation of collision experiments. Key areas of recent RD50 research include new technologies such as CMOS and Low Gain Avalanche Detectors (LGADs), where a dedicated multiplication layer to create a high field region is built into the sensor. We also seek for a deeper understanding of the connection between macroscopic sensor properties such as radiation-induced increase of leakage current, effective doping concentration and trapping, and the microscopic properties at the defect level. Another strong activity is the development of advanced sensor types, like 3D silicon detectors. We will present the state of the art in silicon detectors at radiation levels corresponding to LHC-Phase-II fluences and beyond. Based on our results, we will give an outlook towards the silicon detectors to be used for particle detectors at future colliders like the FCC

The CMS High Granularity Calorimeter for the High Luminosity LHC

The CMS Collaboration is preparing to build replacement endcap calorimeters for the High Luminosity LHC (HL-LHC) era. The new high-granularity calorimeter (HGCAL) is, as the name implies, a highly granular sampling calorimeter with approximately six million silicon sensor channels ($\approx 1.1~\mathrm{cm^2}$ or $0.5~\mathrm{cm^2}$ cells) and about four hundred thousand scintillator tiles readout with on-tile silicon photomultipliers. The calorimeter is designed to operate in the harsh radiation environment at the HL-LHC, where the average number of interactions per bunch crossing is expected to exceed 140. Besides measuring energy and position of the energy deposits the electronics is also designed to measure the time of their arrival with a precision on the order of 50 ps. In addition to the hardware of the HGCAL, developing a reconstruction sequence that fully exploits the granularity to achieve optimal electromagnetic and hadron identification, as well as a good energy resolution in the presence of pileup, is a challenging task

Recombination, selection, and the evolution of tandem gene arrays

Multigene families-immunity genes or sensory receptors, for instance-are often subject to diversifying selection. Allelic diversity may be favored not only through balancing or frequency-dependent selection at individual loci but also by associating different alleles in multicopy gene families. Using a combination of analytical calculations and simulations, we explored a population genetic model of epistatic selection and unequal recombination, where a trade-off exists between the benefit of allelic diversity and the cost of copy abundance. Starting from the neutral case, where we showed that gene copy number is Gamma distributed at equilibrium, we derived also the mean and shape of the limiting distribution under selection. Considering a more general model, which includes variable population size and population substructure, we explored by simulations mean fitness and some summary statistics of the copy number distribution. We determined the relative effects of selection, recombination, and demographic parameters in maintaining allelic diversity and shaping the mean fitness of a population. One way to control the variance of copy number is by lowering the rate of unequal recombination. Indeed, when encoding recombination by a rate modifier locus, we observe exactly this prediction. Finally, we analyzed the empirical copy number distribution of 3 genes in human and estimated recombination and selection parameters of our model

High resolution 3D characterization of silicon detectors using a Two Photon Absorption Transient Current Technique

Trabajo presentado a la 15th Vienna Conference on Instrumentation (VCI), celebrada en Viena (Austria) del 18 al 22 de febrero de 2019.Peer reviewe

High resolution 3D characterization of silicon detectors using a Two Photon Absorption Transient Current Technique

The Two Photon Absorption Transient Current Technique (TPA-TCT) is a tool to characterize semiconductor detectors using a spatially confined laser probe. Excess charge carriers are produced by the simultaneous absorption of two sub-bandgap photons in the material. The current induced by the motion of carriers is studied using well known TCT systems. Differently to standard TCT where the energy deposition (pair creation) is continuous along the beam, TPA-TCT reduces this region to an ellipsoidal volume, achieving thus, true 3D spatial resolution. This paper gives an overview of the technique and shows its performance in irradiated detectors, in particular diodes and High Voltage CMOS detectors.This work was performed in the framework of the CERN-RD50 collaboration under the projects 2016-04, 2017-02. Activity partially supported by the Spanish Ministry of Science grants FPA2015-71292-C2-2-P and FPA2017-85155-C4-1-R; and the European Union’s Horizon 2020 Research and Innovation program under Grant Agreement no. 654168 (AIDA-2020).Peer reviewe

High resolution 3D characterization of silicon detectors using a Two Photon Absorption Transient Current Technique

The Two Photon Absorption Transient Current Technique (TPA-TCT) is a tool to characterize semiconductor detectors using a spatially confined laser probe. Excess charge carriers are produced by the simultaneous absorption of two sub-bandgap photons in the material. The current induced by the motion of carriers is studied using well known TCT systems. Differently to standard TCT where the energy deposition (pair creation) is continuous along the beam, TPA-TCT reduces this region to an ellipsoidal volume, achieving thus, true 3D spatial resolution. This paper gives an overview of the technique and shows its performance in irradiated detectors, in particular diodes and High Voltage CMOS detectors