A novel MicroMegas detector based on microbulk technology with an embedded XY strip structure was developed, obtained by segmenting both the mesh and the anode in perpendicular directions. This ...results in a very low-mass device with good energy and spatial resolution capabilities. Such a detector is practically “transparent” to neutrons, being ideal for in-beam neutron measurements and can be used as a quasi-online neutron beam profiler at neutron time-of-flight facilities. A dedicated front end electronics and acquisition system has been developed and used. The first studies of this new detection system are presented and discussed.
Amorphous and smooth GeTe thin films are deposited on 200 mm silicon substrates by plasma enhanced-metal organic chemical vapor deposition (PE-MOCVD) using the commercial organometallic precursors ...TDMAGe and DIPTe as Ge and Te precursors, respectively. X-ray photoelectron spectroscopy (XPS) measurements show a stoichiometric composition of the deposited GeTe films but with high carbon contamination. Using information collected by Optical Emission Spectroscopy (OES) and XPS, the origin of carbon contamination is determined and the dissociation mechanisms of Ge and Te precursors in H2 + Ar plasma are proposed. As a result, carbon level is properly controlled by varying operating parameters such as plasma radio frequency power, pressure and H2 rate. Finally, GeTe films with carbon level as low as 5 at. % are obtained.
Axion helioscopes aim at the detection of solar axions through their conversion into x-rays in laboratory magnetic fields. The use of low background x-ray detectors is an essential component ...contributing to the sensitivity of these searches. Here we review the recent advances on Micromegas detectors used in the CERN Axion Solar Telescope (CAST) and proposed for the future International Axion Observatory (IAXO). The most recent Micromegas setups in CAST have achieved background levels of 1.5 x 10 super(-6) keV super(-1) cm super(-2) s super(-1), a factor of more than 100 lower than the ones obtained by the first generation of CAST detectors. This improvement is due to the development of active and passive shielding techniques, offline discrimination techniques allowed by highly granular readout patterns, as well as the use of radiopure detector components. The status of the intensive R&D to reduce the background levels will be described, including the operation of replica detectors in test benches and the detailed Geant4 simulation of the detector setup and the detector response, which has allowed the progressive understanding of background origins. The best levels currently achieved in a test setup operating in the Canfranc Underground Laboratory (LSC) are as low as ~ 10 super(-7) keV super(-1) cm super(-2) s super(-1), showing the good prospects of this technology for application in the future IAXO.
New large-size Micromegas detectors are being developed for the future physics program of the COMPASS experiment at CERN. These detectors will have a pixelised readout in their center to detect ...particles in the beam region, where the particle flux can reach several MHz/cm super(2) in nominal conditions, and will have to handle high intensity hadron beams (up to a few 10 super(7) hadrons/s) with a discharge rate lower than 0.01 to 0.001 discharge/s. Several prototypes with two different discharge rate reduction technologies (preamplification stage with a GEM foil and resistive read-out with buried resistors) have been studied in the COMPASS beam since 2010. Four of them have been included in the spectrometer since 2012, and have been used for the track reconstruction. Their performance (detection efficiency, space and time resolutions, and discharge rates) for different beam intensities and magnetic fields environments are presented. These detectors play an important role in the track reconstruction at very small angle; their impact is presented, with a particular emphasis on the effect of the background reduction due to an improved cluster selection.
Low Background Micromegas in CAST Garza, J G; Aune, S; Aznar, F ...
Journal of physics. Conference series,
11/2015, Letnik:
650, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Solar axions could be converted into x-rays inside the strong magnetic field of an axion helioscope, triggering the detection of this elusive particle. Low background x-ray detectors are an essential ...component for the sensitivity of these searches. We report on the latest developments of the Micromegas detectors for the CERN Axion Solar Telescope (CAST), including technological pathfinder activities for the future International Axion Observatory (IAXO). The use of low background techniques and the application of discrimination algorithms based on the high granularity of the readout have led to background levels below 10-6 counts keV cm2 s, more than a factor 100 lower than the first generation of Micromegas detectors. The best levels achieved at the Canfranc Underground Laboratory (LSC) are as low as 10-7 counts keV cm2 s, showing good prospects for the application of this technology in IAXO. The current background model, based on underground and surface measurements, is presented, as well as the strategies to further reduce the background level. Finally, we will describe the R&D paths to achieve sub-keV energy thresholds, which could broaden the physics case of axion helioscopes.
New Micromegas (Micro-mesh gaseous detectors) are being developed in view of the future physics projects planned by the COMPASS collaboration at CERN. Several major upgrades compared to present ...detectors are being studied: detectors standing five times higher luminosity with hadron beams, detection of beam particles (flux up to a few hundred of kHz/mm super(2), 10 times larger than for the present Micromegas detectors) with pixelized read-out in the central part, light and integrated electronics, and improved robustness. Two solutions for a reduction of the impact of discharges have been studied, with Micromegas detectors using resistive layers and using an additional GEM foil. The performance of such detectors has been measured during beam test periods. A large size prototype with nominal active area and pixelized read-out has been produced and installed in the COMPASS spectrometer in 2010. In 2011 prototypes featuring an additional GEM foil, as well as a resistive prototype, were tested in similar conditions and preliminary results from those detectors are very promising. We present here the project and report on its status, in particular the performance of large size prototypes with an additional GEM foil.
The steadily increasing luminosity of the LHC requires an upgrade with high-rate and high-resolution detector technology for the inner end cap of the ATLAS muon spectrometer: the New Small Wheels ...(NSW). In order to achieve the goal of precision tracking at a hit rate of about 15 kHz/cm2 at the inner radius of the NSW, large area Micromegas quadruplets with 100µm spatial resolution per plane have been produced. IRFU, from the CEA research center of Saclay, is responsible for the production and validation of LM1 Micromegas modules. The construction, production, qualification and validation of the largest Micromegas detectors ever built are reported here. Performance results under cosmic muon characterization will also be discussed.
A novel large volume spherical proportional counter, recently developed, is used for neutron measurements. The pure N2 gas is studied for thermal and fast neutron detection, providing a new way for ...neutron spectroscopy. The neutrons are detected via the N14(n,p)C14 and N14(n,α)B11 reactions. The detector is tested for thermal and fast neutrons detection with Cf252 and Am241−Be9 neutron sources. The atmospheric neutrons are successfully measured from thermal up to several MeV, well separated from the cosmic ray background. A comparison of the spherical proportional counter with the current available neutron counters is also presented.
We present particle beam test results using a high-rate, high-position and high-time-resolution gaseous detector, ‘Micromegas’, of
15×15
cm
2
. The rate capability was measured with 10
MeV protons ...from a TANDEM accelerator. No effect on gain was observed at particle rates up to
10
9
mm
−2
s
−1. With an argon and DME filling the gain was stable up to 50 mC total charge on a
3
mm
2
area. With minimum-ionizing particles in a CERN beam a high efficiency, close to 100%, was measured, under stable conditions. A first space-resolution measurement of
50
μ
m
±20
μ
m was obtained. The operation of the chamber shows that it is possible to optimize the geometrical parameters in order to improve the space resolution and bring the time resolution low enough to contain the events of each beam crossing (every 25
ns) in the European Large Hadron Collider. Further work in this direction is being actively pursued.
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