Fiber optic sensors in the ATLAS Inner Detector Scherino, L.; Schioppa, E.J.; Arapova, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2022, Volume:
1029
Journal Article
Peer reviewed
Open access
A prototype system of Fiber Optic Sensors (FOS) for the accurate measurement of temperature and relative humidity, has been installed inside the Inner Detector volume of the ATLAS experiment at the ...LHC. The goal is to evaluate the behavior of the technology against radiation effects, and possibly to assess its suitability for future collider experiments, starting from HL-LHC. It follows the description of the work that has led to the choice of the sensors, their testing and calibration in the laboratory, their successive installation and operation in ATLAS, and the development of the data acquisition chain. The first results on performance are reported.
Body size is influenced by the interaction of multiple forces, whose effects can determine the occurrence of sexual size dimorphism (SSD). Rensch's rule is the increase of SSD with body size in taxa ...where males are the largest sex, and the opposite pattern in female‐biased SSD taxa. This pattern was detected in many animal groups, but contrasting results were also highlighted. This study evaluated the existence of Rensch's patterns for body size and for the number of caudal vertebrae in salamandrid caudate amphibians. Furthermore, we tested the support of alternative hypotheses on processes that may determine allometric patterns: sexual selection, fecundity selection and constraining selection by performing separate analyses on species with male‐ and female‐biased SSD. We used the literature and original data to gather information on body size and number of caudal vertebrae in 52 species of salamandrids over four continents. We then tested the support of the three hypotheses using a phylogenetic approach. Rensch's rule was valid for body size in salamanders only for species with male‐biased dimorphism. No allometric relationships were detected by analyses on all the species, or by analyses on female‐biased SSD species. Analyses performed on the number of caudal vertebrae showed no significant patterns. Our study supports the role of sexual selection in promoting positive allometry for body size in male‐biased SSD species, whereas the alternative hypotheses were not supported by our data. These results highlight the importance of distinguishing male‐ and female‐biased species as different evolutionary pressures and constraints may be at the basis of evolution of SSD in these groups.
Effective population size (Ne) is a key determinant of genetic diversity of populations. In amphibians, the ratio effective population size/census size (Ne/N) is often very low, raising concerns for ...the long‐term persistence of genetic diversity in isolated populations. It has been proposed that the phenomenon of ‘genetic compensation' increases the ratio Ne/N in small populations, but the underlying mechanisms are poorly understood. Polygyny can decrease Ne/N because of the negative relationship between polygyny and Ne. We used genetic information (microsatellites) to evaluate the relationship between census size, polygyny and Ne in populations of the threatened Italian agile frog Rana latastei. We reconstructed parentage in tadpoles from nine populations with eight to 32 breeding females, using a likelihood‐based method; we analysed simulated datasets with known properties to confirm the reliability of this approach in reconstructing polygyny. Furthermore, we estimated Ne using approximate Bayesian computation. The level of polygyny differed strongly among populations (average number of mates per breeding male: 2-6.4). Polygyny was greater in populations with larger census sizes. Moreover, variance in male mating success was larger in large populations. Effective population size increased with population size, but was negatively related to polygyny; as polygyny increased in large populations, this was associated with reduced Ne/N. In polygynous species, increasing levels of polygyny in large populations may explain the low Ne/N values, with important implications for the conservation of genetic diversity and for long‐term population persistence.
Measurement results of the MALTA monolithic pixel detector Schioppa, E.J.; Asensi Tortajada, I.; Berdalovic, I. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Volume:
958
Journal Article
Peer reviewed
MALTA is a full scale monolithic pixel detector implemented in TowerJazz 180 nm CMOS technology. The small pixel electrode allowed for the implementation of a fast, low noise and low power front-end, ...which is sensitive to the charge released by ionizing radiation in a 20–25 μm deep depleted region. The novel asynchronous matrix architecture is designed to ensure low power consumption and high rate capability. Such features make MALTA a possible candidate for the outer layer of ATLAS Inner Tracker (ITk) upgrade. Unirradiated and irradiated MALTA sensors have been extensively tested in laboratory and with high energy particle beams. Results of this measurements campaign are shown, and the further improvements that are being implemented in the next versions of the chip are discussed.
X-ray transition radiation detectors (TRDs) are used for particle identification in both high energy physics and astroparticle physics. In most of the detectors, emission of the X-ray transition ...radiation (TR) starts at Lorentz factors above γ∼500 and reaches saturation at γ∼2÷3⋅103. However, many experiments require particle identification up to γ∼105, which is very difficult to achieve with conventional detectors. Semiconductor pixel detectors offer a unique opportunity for precise simultaneous measurements of spectral and angular parameters of TR photons. Test beam studies of the energy and the angular distributions of TR photons emitted by electrons and muons of different momenta crossing several types of radiators were performed at the CERN SPS with a 480 μm thick silicon detector bonded to a Timepix3 chip. High resolution images of the energy−angle phase space of the TR produced by different radiators were obtained and compared with MC simulations. The characteristic interference patterns are in agreement with the theoretical models with an unprecedented level of details. The studies presented in this paper also show that simultaneous measurements of both the energy and the emission angles of the TR X-rays could be used to enhance the particle identification performances of TRDs.
A 300 μm thick thin p-on-n silicon sensor was connected to an energy sensitive pixel readout ASIC and exposed to a beam of highly energetic charged particles. By exploiting the spectral information ...and the fine segmentation of the detector, we were able to measure the evolution of the transverse profile of the charge carriers cloud in the sensor as a function of the drift distance from the point of generation. The result does not rely on model assumptions or electric field calculations. The data are also used to validate numerical simulations and to predict the detector spectral response to an X-ray fluorescence spectrum for applications in X-ray imaging.
The last couple of years have seen the development of Depleted Monolithic Active Pixel Sensors (DMAPS) fabricated with a process modification to increase the radiation tolerance. Two large scale ...prototypes, Monopix with a column drain synchronous readout, and MALTA with a novel asynchronous architecture, have been fully tested and characterized both in the laboratory and in test beams. This showed that certain aspects have to be improved such as charge collection after irradiation and the output data rate. Some improvements resulting from extensive TCAD simulations were verified on a small test chip, Mini-MALTA. A detailed cluster analysis, using data from laboratory and test beam studies, at different biases, for high and low thresholds and before and after irradiation is presented, followed by detailed simulations showing that the digital architecture for both chips is capable of dealing with data rates of around 80 MHz/cm2 similar to what it is expected in the outer layer of the ATLAS inner tracker upgrade for the HL-LHC. The data rate capability and output bandwidth are studied using realistic hits generated by the ATLAS detector simulation framework.
Detector prototypes are commonly characterised in testbeams, either using charged particles or X-rays. Charged particles are used to quantify detector performance in terms of absolute efficiency, ...while X-rays can provide additional information about the detector structure. This paper presents an alternative approach to calculating charged particle efficiencies, using the results of an X-ray testbeam of the mini-MALTA CMOS prototype at Diamond Light Source, and additional laboratory measurements. Results are presented for an unirradiated and an irradiated sample and compared to the results of charged particle testbeams at SPS and ELSA. The extrapolated efficiencies are in agreement with the measured values. Additionally, the extrapolated efficiency maps provide more insight about the location of the pixel inefficiencies, due to the better spatial resolution of the X-ray testbeam.
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