This paper reports about the first Micromegas-based telescope built for applications in muon tomography. The telescope consists of four, 50×50cm2 resistive multiplexed Micromegas with a 2D layout and ...a self-triggering electronics based on the Dream chip. Thanks to the multiplexing, the four detectors were readout with a single Front-End Unit. The high voltages were provided by a dedicated card using low consumption CAEN miniaturized modules. A nano-PC (Hummingboard) ensured the HV control and monitoring coupled with a temperature feedback as well as the data acquisition and storage. The overall consumption of the instrument yielded 30W only, i.e. the equivalent of a standard bulb. The telescope was operated outside during 3.5months to image the water tower of the CEA-Saclay research center, including a 1.5-month campaign with solar panels. The development of autonomous, low consumption muon telescopes with unprecedented accuracy opens new applications in imaging as well as in the field of muon metrology.
Why do we flush gas in gaseous detectors? Procureur, S.; Attié, D.; Bouteille, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2020, Letnik:
955
Journal Article
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The effects and the origin of the gas degradation in a gaseous detector-based tracker are investigated. The study focused on the so-called T2K gas, which turned out to be highly sensitive to ...pollutants. In particular the H2O and O2 concentrations were monitored online in different conditions to establish their influence on the gain of the detectors. This pollution was first mitigated by a recirculating and accelerating gas system with the use of a turbine and different absorbers. Further measurements revealed that this pollution originates from a continuous permeation process through the different materials of the gas circuit. In particular, polyurethane-based gas pipes or polyester materials largely increase the level of humidity. As a direct consequence of this work, the gas autonomy of the muon telescopes currently deployed inside the Khufu’s pyramid have been dramatically improved.
For measuring gamma rays from low energy to high energy and cover the gap between 1 MeV and 300 MeV in space measurements, Time Projection Chambers (TPC) are a promising solution. In order to read ...the data out of these TPCs, one needs a dedicated electronics to be flexible to cover a wide range of detectors types, with a good resolution over a large dynamic range of incoming charges. The ASTRE chip, a radiation tolerant chip for these applications is described in this article. This Application Specified Integrated Circuit (ASIC) permits the amplification, filtering, triggering and analog storage of 512 samples at a flexible sampling frequency up to 100 MHz. The power consumption is less than 10 mW/channel, with 64 channels per ASIC. The charge range of ASTRE is from 120 fC to 10 pC with 4 programmable gains. The filtering supports 16 peaking times (from 60 ns to 8μs). The ASIC can read negative or positive signals and return a multiplicity signal for triggering and selective readout. In addition it has a programmable internal trigger readable with Low Differential Voltage Signal (LVDS) outputs. The chip was fabricated in August 2016 and is under test. The results of this ASIC to Single Event Latchups, made at the Universite Catholique de Louvain (UCL) are detailed below.
The performance of the first large resistive Micromegas detectors with 2D readout and genetic multiplexing is presented. These detectors have a 50×50cm2 active area and are equipped with 1024 strips ...both in X- and Y-directions. The same genetic multiplexing pattern is applied on both coordinates, resulting in the compression of signals on 2×61 readout channels. Four such detectors have been built at CERN, and extensively tested with cosmics. The resistive strip film allows for very high gain operation, compensating for the charge spread on the 2 dimensions as well as the S/N loss due to the huge, 1nF input capacitance. This film also creates a significantly different signal shape in the X- and Y-coordinates due to the charge evacuation along the resistive strips. All in all a detection efficiency above 95% is achieved with a 1cm drift gap. Though not yet optimal, the measured 300µm spatial resolution allows for very precise imaging in the field of muon tomography, and some applications of these detectors are presented.
The CLAS12 Micromegas Vertex Tracker Acker, A.; Attié, D.; Aune, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2020, Letnik:
957, Številka:
C
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The Micromegas Vertex Tracker was designed to improve upon the tracking capabilities of the baseline design of the CLAS12 spectrometer in Hall B at Jefferson Laboratory. A Barrel Micromegas Tracker ...made with six concentric cylinders, each made of three 120∘-sector tiles, surrounds the Silicon Vertex Tracker, and a Forward Micromegas Tracker composed of 6 disks is placed 30 cm downstream of the liquid-hydrogen target. Both trackers sit in a 5 T solenoid magnetic field. All Micromegas elements are based on resistive technology to withstand luminosities up to 1035 cm−2 s−1, as well as on bulk technology to enforce gain uniformity and mechanical robustness. Due to the high magnetic field, dedicated electronics have been designed and displaced ∼2 m away from the detectors. The electronics readout is based on the DREAM ASICs that allow sustained operation up to 20 kHz trigger rate at the maximum luminosity.
We analyse the performance of a gas time projection chamber (TPC) as a high-performance gamma-ray telescope and polarimeter in the e+e− pair-creation regime. We use data collected at a gamma-ray beam ...of known polarisation. The TPC provides two orthogonal projections (x, z) and (y, z) of the tracks induced by each conversion in the gas volume. We use a simple vertex finder in which vertices and pseudo-tracks exiting from them are identified. We study the various contributions to the single-photon angular resolution using Monte Carlo simulations, compare them with the experimental data and find that they are in excellent agreement. The distribution of the azimuthal angle of pair conversions shows a bias due to the non-cylindrical-symmetric structure of the detector. This bias would average out for a long duration exposure on a space mission, but for this pencil-beam characterisation we have ensured its accurate simulation by a double systematics-control scheme, data taking with the detector rotated at several angles with respect to the beam polarisation direction and systematics control with a non-polarised beam. We measure, for the first time, the polarisation asymmetry of a linearly polarised gamma-ray beam in the low energy pair-creation regime. This sub-GeV energy range is critical for cosmic sources as their spectra are power laws which fall quickly as a function of increasing energy. This work could pave the way to extending polarised gamma-ray astronomy beyond the MeV energy regime.
The R&D activities for the Linear Collider TPC (LCTPC) are currently focused on the adoption of the Micro-Pattern Gaseous Detectors (MPGDs). Different MPGD modules which are commissioned on the ...endplate of a Large Prototype TPC (LPTPC) at DESY, were tested with a 5 GeV electron beam, under a 1 T magnetic field. During the tests, reduced signal sensitivity as well as distortion in the reconstructed track, were observed at the boundary of these modules. We have numerically investigated the origin of the track distortions observed close to the edges of the Micromegas modules. The study clearly shows that the electric field non-uniformity near the inter-modular gaps is responsible for such track distortion. We have been able to simulate the observed patterns and magnitudes of distortion successfully. The obtained agreements with 2015 beam test data encourage us to continue with the study and, to propose module design modifications that can alleviate the problem of electrostatic field distortion at the module boundaries.
Potential applications of muon tomography, or muography, as non-invasive scanning method have increased in the last years together with the performance of the particle detectors used for muon ...detection, known as muon telescopes. A new concept muon telescope is presented, which could enlarge even more the range of application of this technique. It is based on a compact TPC equipped with a 2D pixelized Micromegas detector with multiplexed readout. This detector will overcome some of the constraints of the instruments currently used, as they limited acceptance, while keeping other features required for muography as stability, robustness or portability. Moreover, it will be capable to reconstruct the 3D direction of the incident muons with a single instrument. With its design and features, this kind of detectors can be fitted at boreholes from where they can scan the surroundings, being an interesting technique for mining exploration, geotechnics or monitoring of dykes or bridges which has arouse the interest of industry. In a further phase it is expected to develop a network of these detectors which will allow the 3D reconstruction of the studied object by the combination of the images registered by each of the telescopes. Main features and first tests and results of this new instrument will be presented together with some studies, performed by Monte Carlo simulations, of the capabilities of this muon telescope and the analysis principle.
HARPO is a time projection chamber (TPC) demonstrator of a gamma-ray telescope and polarimeter in the MeV-GeV range, for a future space mission. We present the evolution of the TPC performance over a ...five month sealed-mode operation, by the analysis of cosmic-ray data, followed by the fast and complete recovery of the initial gas properties using a lightweight gas circulation and purification system.
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