The GEMPix detector Murtas, F.
Radiation measurements,
11/2020, Letnik:
138
Journal Article
Recenzirano
Odprti dostop
The GEMPix is a novel detector developed at CERN, designed and built by coupling a small triple Gas Electron Multiplier with a quad Timepix ASIC for the readout. This structure has the advantage to ...have higher sensitivity to soft X-ray and high radiation tolerance for good spatial resolution of 2D images of intense particle beams. Several applications of this detector have been studied in the last years and some of them will be described in detail.
•The GEMPix is a novel Micro Pattern Gas Detector with a sub-millimetric pads readout performed using 4 Timepix ASIC chip.•This detector is radiation tolerant, sensitive to soft X-rays (below 5 keV) and able to measure high flux of particles.•The detector has been used in Burning Plasma diagnostics and in 3D reconstruction of the Bragg peak of Hadron-therapy beam.•It can be used also for the studies and optimization of gas detectors.•Future use in micro dosimetry measurements using tissue equivalent gas mixture.
Micro-Pattern Gaseous Detectors (MPGD) have opened the way for the construction of detectors whose performance surpasses that of the previous generations in terms of spatial resolution, high-rate ...capability and increased radiation hardness. Led by the Micro-Mesh Gaseous Structure (Micromegas) and the Gas Electron Multiplier (GEM), some MPGDs are mature technologies used in a variety of experiments at high energy physics. What we report in this article is the experience explored in the last years with a compact GEM detector system in several applications as medical imaging, dosimetry and beam diagnostics for high energy beams and for nuclear reactors. For sake of shortness, only performance on soft X-ray and neutron detection will be described in detail. Also a description of the new promising highly pixelated GEM detector will be presented.
Abstract
The GEMPix is a small gaseous detector with a highly
pixelated readout, consisting of a drift region, three Gas Electron
Multipliers (GEMs) for signal amplification, and four Timepix ASICs
...with 55 μm pixel pitch and a total of 262,144 pixels (512×512
pixels). A continuous flow of a gas mixture (here propane-based
tissue equivalent gas) is supplied externally at a rate of
5 L/h. By placing a sealed
241
Am source outside of the
detector and varying the source-detector distance, the residual
energy of alpha particles entering the sensitive volume of the
GEMPix through a thin Mylar window is varied. An alpha spectrometry
measurement was performed to determine the emission spectrum of the
source, and this spectrum was then used as an input to a FLUKA Monte
Carlo simulation to obtain the residual energy of the alpha
particles. Thus, a calibration curve from 5.9 keV (from an
55
Fe source) up to more than 2 MeV was obtained, which is
needed for future applications of the detector, in particular for
microdosimetry.
The W-MON project goal is to establish an automatic control mechanism of the presence of radioactive material in conventional waste containers at CERN using a distributed network of interconnected ...low-power radiation sensors. This network facilitates continuous data recording, transfer and storage in a database while allowing online and offline data analysis, in addition to alarm triggering. Data transmission, processing and evaluation is achieved by a centralized IoT end-to-end data architecture that has been developed for real-time monitoring and visualization of the radiation levels in waste containers. In this paper the results of field tests of the W-MON system described in two previous papers are presented for three different types of sensors. Estimation of failure detection probability, long-term stability tests and sensitivity studies carried out using radioactive samples of various activities placed in standard waste containers are described. A comparison between the manual monitoring procedure currently used at CERN and the W-MON system is discussed in detail.
•W-MON system is a network of low-power radiation sensors.•Automatic control of radioactive material in waste containers at CERN.•Centralized IoT architecture enables continuous data transmission.•Real-time monitoring and visualization of radiation levels.•Long-term stability tests using radioactive samples in standard containers.•W-MON system can efficiently replace existing manual monitoring procedures.
We present the measurement of negative ion drift velocities and mobilities for innovative particle tracking detectors using gas mixtures based on SF6. This gas has recently received attention in the ...context of directional Dark Matter searches, thanks to its high Fluorine content, reduced diffusion and multiple species of charge carriers, which allow for full detector fiducialization. Our measurements, performed with a 5 cm drift distance Negative Ion Time Projection Chamber, show the possibility of negative ion operation in pure SF6 between 75 and 150 Torr with triple thin GEM amplification, confirming the attractive potentialities of this gas. Above all, our results with the mixture He:CF4:SF6 360:240:10 Torr demonstrate for the first time the feasibility of SF6− negative ion drift and gas gain in He at nearly atmospheric pressure, opening very interesting prospects for the next generation of directional Dark Matter detectors.
Abstract
The present work is focused on the characterization of a
Timepix3 (TPX3) based test system for the identification of
particles produced by the complex decay chain of
222
Rn. The
detector ...used is composed of a pixelated Cadmium Telluride (CdTe)
semiconductor (500 μm thick) bump-bonded on an ASIC TPX3
chip. Measurements were carried out at the NIXT Laboratory (ENEA
Frascati) using radioactive sources and exploiting the presence of
natural radon gas by collecting its decay products on the sensor
surface. Estimation of the radon gas risk is one of the most
important problems in radiation protection and has stimulated
further development of new advanced methods suitable for detecting
this gas in confined environments. A study of the spatial uniformity
and high energy calibration is also presented and an improved
cluster analysis is introduced. The performance highlighted in this
study will allow a detailed and faster analysis of the radon
products and may have an important impact on the environmental
radioprotection applications. This paper describes the application
and use of this test system to identify the different decay
signatures and follow the temporal evolution of the Radon decay
chain.
A pixelated 2-D detector combining chemical-vapor-deposited diamond and the Timepix3 chip ("Diamondpix") is presented. Its conceptual design with a brief description of the Timepix3 chip acquisition ...modes is outlined. The performance has been tested with fluorescence X-rays, fast neutrons, and electron beam. A first energy calibration has been obtained with X-rays and compared with an equivalent silicon Timepix3 detector. Measurements on fast neutrons and other radioactive source demonstrated a good gamma/neutron rejection capability. Moreover, Diamondpix has been exposed to a beam of ultrarelativistic electrons showing that it can act as a very powerful monitor of beam position, measuring simultaneously the charge released inside the detector and the time of arrival (ToA) of the particles by reconstructing the time profile of the beam bunches. Finally, high-intensity measurements show some delayed signals probably related to the trap defects inside the diamond. The first study of their spatial distribution correlated with the measurements of the charge released inside the diamond and ToA is also discussed.
The particular physics of Laser Produced Plasmas (LPP) needs some diagnostic requirements. Specifically, the X-ray monitoring of the plasma is known to be difficult since typically X-ray emissions ...are concentrated in bursts from a few tens of ps to few ns, based on the power and pulse time width of the laser. Therefore, the energy measurement of the radiation coming from a single experimental run is basically unfeasible using conventional techniques. Additional particles can be produced from LPP experiments, especially high energy gamma photons and electrons. As a case study in recent experiments, carried out on VEGA-2 laser facility (CLPU, Salamanca, Spain), the aim was to produce neutrons through photonuclear reactions on different types of solid targets. We have used the Timepix3 chip, in a “side-on” configuration, in order to produce a quick estimate of the gamma photons energy involved in the reactions. This detector, based on silicon, is realized with a single chip of 256 × 256 pixels bump-bonded with a 14 mm × 14 mm × 300 μm silicon layer. Interaction of gammas with the detector in this configuration produces some characteristic clusters of pixels and, for each cluster, a variety of physical and morphological parameters can be defined. Based on some of these parameters, we have characterized the detector response using some known laboratory gamma sources and the related Geant4 simulations. This allows quick energy discrimination for the gamma photons coming from different experimental runs.
The W-MON project aims to improve and automatize the control of the presence of radioactive material in conventional waste containers at CERN using a distributed network of interconnected low-power ...radiation sensors. The key development is the integration of a lightweight but sensitive radiation sensor in a powerful network that allows continuous data recording, transfer and storage in a database for alarm triggering and subsequent data analysis. The Chiyoda D-shuttle personal dosimeter was used as proof-of-concept. Extensive tests performed with the commercial version of the D-shuttle showed that its robustness, stability under variable thermal conditions, high sensitivity and hourly dose logging capabilities make it a strong candidate for the project. To comply with the requirements of remote operation and wireless data transmission to a central server, a customized version of the D-shuttle has been developed. Two additional radiation sensors are also currently being considered. The sensors have been coupled to a custom-made communication board allowing for long-range low-power LoRa wireless data transmission. A centralized IoT (Internet of Things) end-to-end data architecture has been developed for real-time monitoring and visualization of the radiation level in waste containers before the final integration into REMUS, the overall CERN Radiation and Environment Monitoring Unified Supervision service.
•Environmental radiological monitoring for conventional waste.•Lightweight and smart radiation sensors for real-time monitoring of the radiation level in waste containers.•Distributed network of interconnected low-power radiation sensors with LoRa wireless data transmission.
We describe the performance of the Timepix silicon detector operation at the SPS and H8 extracted beam line at CERN. Some detector calibration results and tuning will be discussed and a new cluster ...analysis algorithm, to reconstruct the particle hits, is described as well. We investigated the optimal acquisition setup for the Timepix device in order to use its full capabilities. A setup of 4 planes of the Timepix hybrid silicon pixel detector is tested as a hodoscope in the H8 180 GeV/c extracted pion beam, and also with a special 3 ns channeled proton bunch sequence inside the SPS accelerator. Spatial and angular distributions are measured.
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