Four hybrid pixel detectors of Timepix3 technology, installed in the ATLAS experiment, were continuously taking data from April 2018 until the end of the Run-2 data taking period (December 2019). ...These detectors are synchronized with each other and the LHC orbit clock. They are capable of resolving the bunch structure of the LHC beams due to their time resolution of ∼2ns. Thus, they allow the characterization of the radiation field inside and outside bunch-crossing periods. This is shown for Timepix3 detectors at the extended barrel (x=-3.58 m, y=0.97 m, z=2.83 m). We apply pattern recognition methods to decompose the radiation field and determine the directionality of the minimum ionizing particles (MIP) component of the radiation field.
Abstract
Timepix3 pixel detectors have demonstrated great potential for tracking applications. With 256 × 256 pixels, 55 µm pitch and improved resolution in time (1.56 ns) and energy (2 keV at 60 ...keV), they have become powerful instruments for characterization of unknown radiation fields. A crucial pre-processing step for such analysis is the determination of particle trajectories in 3D space from individual tracks. This study presents a comprehensive comparison of regression methods that tackle this task under the assumption of track linearity. The proposed methods were first evaluated on a simulation and assessed by their accuracy and computational time. Selected methods were then validated with a real-world dataset, which was measured in a well-known radiation field. Finally, the presented methods were applied to experimental data from the Large Hadron Collider. The best-performing methods achieved a mean absolute error of 1.99° and 3.90° in incidence angle
θ
and azimuth
φ
, respectively. The fastest presented method required a mean computational time of 0.02 ps per track. For all experimental applications, we present angular maps and stopping power spectra.
The performance and response of a Timepix3 detector with a 500 μm thick GaAs:Cr sensor layer was investigated in different radiation fields. The sensor resistivity was ρ≈109Ω cm. Fitting different ...modified Hecht functions, which take the small pixel effect into account, the mobility-lifetime products of μeτe=(0.773±0.018)×10−4 cm2V−1 and μeτe=(0.996±0.056)×10−4 cm2V−1 were determined. Hereby, the latter value is favored due to the better agreement of fit and data. In a measurement in a 40 GeV/c pion beam, the drift times and charge collection efficiencies were studied as a function of the interaction depth. We present the measured drift velocity as a function of the electric field strength and compare the determined dependence with a model. In a measurement in a mixed ion beam, we study the capability of the detector to separate different ion species. We show the detector response in the form of tracks and discuss heavy ion track features.
The response of a Timepix3 detector (256×256 pixels, pixel pitch 55 μm) with a 300 μm thick silicon sensor was studied in relativistic charged particle beams at the Super-Proton-Synchrotron at CERN . ...The detector was irradiated at different angles in a 400 GeV/c primary proton beam and in a mixed beam created by a 330 GeV/c Pb beam hitting a beryllium target. We present and discuss energy deposition spectra and particle track features for relativistic particles of different stopping power. The proton data shows that a relative energy resolution of approximately 9 % can be achieved. Analysis of deposited energy spectra and tracks in the detector produced by heavier ions are carried out with the aim to investigate the capabilities of the Timepix3 detector for decomposing the mixed beam. Using spectrum stripping technique by iterative Landau curve fitting charge discrimination could be done up to Z=7 for impact angle of 60 degrees (with respect to the sensor normal). For smaller impact angles the particle charge separation is decreased due to the saturation of the pixel electronics (∼600 keV) . Previous works describing the 3D track reconstruction for minimally ionizing particles (Z=1) were extended in the present work by adding the methodology of heavier ions track reconstruction in 3D.
The capability of Timepix3 detectors installed in ATLAS to measure luminosity is evaluated. It is described how noisy pixels are identified and excluded. Two different methods for luminosity ...determination, i.e. cluster counting and thermal neutron counting are described and compared with each other. The achieved short-term relative precision with both methods is determined by modeling the luminosity curve. It is shown that using cluster counting a short-term relative precision of <0.5 % can be achieved for 60 s time intervals. For thermal neutrons, a short-term relative precision (for 60 s intervals) of ≈2 % was found. Hereby statistics was the limiting factor. The findings are discussed in view of Timepix3 upgrade plans for LHC Run-3.
New developments of pixel detectors based on GaAs sensors offer effective registration of the transition radiation (TR) X-rays and perform simultaneous measurements of their energies and emission ...angles. This unique feature opens new possibilities for particle identification on the basis of maximum available information about generated TR photons. Results of studies of TR energy-angular distributions using a 500 |j.m thick GaAs sensor attached to a Timepix3 chip are presented. Measurements, analysis techniques and a comparison with Monte Carlo (MC) simulations are described and discussed.
Growing energies of particles at modern or planned particle accelerator experiments as well as cosmic ray experiments require particle identification at gamma-factors (γ) of up to ∼105. At present ...there are no detectors capable of identifying charged particles with reliable efficiency in this range of γ. New developments in high granular pixel detectors allow one to perform simultaneous measurements of the energies and the emission angles of generated transition radiation (TR) X-rays and use the maximum available information to identify particles. First results of studies of TR energy-angular distributions using gallium arsenide (GaAs) sensors bonded to Timepix3 chips are presented. The results are compared with those obtained using a silicon (Si) sensor of the same thickness of 500 μm. The analysis techniques used for these experiments are discussed.
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