Hypothetical low-mass particles, such as axions, provide a compelling explanation for the dark matter in the universe. Such particles are expected to emerge abundantly from the hot interior of stars. ...To test this prediction, the CERN Axion Solar Telescope (CAST) uses a 9 T refurbished Large Hadron Collider test magnet directed towards the Sun. In the strong magnetic field, solar axions can be converted to X-ray photons which can be recorded by X-ray detectors. In the 2013-2015 run, thanks to low-background detectors and a new X-ray telescope, the signal-to-noise ratio was increased by about a factor of three. Here, we report the best limit on the axion-photon coupling strength (0.66 × 10-10 GeV-1 at 95% confidence level) set by CAST, which now reaches similar levels to the most restrictive astrophysical bounds.
Due to their simplicity and accuracy for reconstructing particle trajectories, Micromegas (Micro-MEsh-GAseous Structure) and Gas Electron Multiplier (GEM) detectors are commonly used as readout ...systems in Time Projection Chambers (TPCs). The main limitation of these two types of detectors is the ion backflow (IBF), which may result in space charge in a TPC. We present in this article a new Micro-Pattern Gaseous Detector (MPGD) structure, which combines a micro-mesh and a set made of a GEM surmounted by a micro-mesh at only a few hundreds μm above. We report the performance results of two prototypes using this new structure, and compare them to a single Micromegas and a hybrid detector composed of a Micromegas and a GEM with a few millimeters gap. Finally, we show that this new detector is capable of reducing the ion backflow to less than 0.2% for a total gain of around 2000.
Recent developments have shown that coupling a Micromegas gaseous detector on a glass substrate with a transparent anode and a CMOS camera enables the optical readout of Micromegas detectors with a ...good spatial resolution, demonstrating that the glass Micromegas detector is well-suited for imaging. This feasibility test has been effectuated with low-energy X-ray photons also permitting energy resolved imaging. This test opens the way to different applications. Here we will focus on two applications. Namely, neutron imaging for non-destructive examination of highly gamma-ray emitting objects, such as irradiated nuclear fuel or radioactive waste. And secondly, we are developing a beta imager for the cell tagging in the field of anticancerous drug studies.
Both applications require to design the detectors in view of the specific constraints of reactor dismantling and medical applications: spatial resolution and strong gamma suppression for neutron imaging and precise rate and energy spectrum measurements for the beta.
A dedicated system consisting of a glass Micromegas detector and an ultrasensitive camera has been designed and assembled. Here we present the first results from the characterization of the detectors, as well as the first acquired images.
For many years 3H and 14C labelling of molecules of pharmaceutical interest has been performed to study their in vivo biodistribution on animal tissue sections through β-particles detection. Film ...autoradiography has progressively been replaced by digital β-imagers capable of high sensitivity, real-time imaging and activity counting for absolute quantification of radioactive compounds in tissue sections. After the discovery of the tumor heterogeneity phenomenon, research efforts for characterizing cell heterogeneity have been at the heart of oncology research, aiming at a better understanding of the causes and progression of the disease. This new perspective has also allowed for cell-targeting drugs, and radically changed both sample sizes and radiotracer activities. In this context, Medica-Plus, a transversal project gathering biologists, microfluidics specialists and detector developers, intends to perform quantification of low dose 3H- or 14C-labelled drugs inside single cells. This article reports preliminary results obtained with a prototype detector measuring tritium-generated signal.
Radiation imaging with glass Micromegas Brunbauer, F.M.; Desforge, D.; Ferrer-Ribas, E. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2020, Letnik:
955
Journal Article
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Optically recording scintillation light emitted by MicroPattern Gaseous Detectors (MPGDs) with imaging sensors is a versatile and performant readout modality taking advantage of modern high ...granularity imaging sensors. To allow scintillation light readout of a detector based on MicroMesh Gaseous Structure (Micromegas) technology, we have integrated a Micromegas on a glass substrate with a transparent anode. In addition to optical detection of scintillation light emitted during electron avalanche multiplication between the micromesh and the anode, this setup also achieves a good energy resolution. A glass Micromegas detector was operated in an Ar/CF4 gas mixture and showed a response comparable to conventional Micromegas detectors. The spectrum of the emitted scintillation light was recorded and shown to be equivalent to the one obtained with other gaseous detectors in the same gas mixture. Optically read out images were recorded with CCD cameras and integrated X-ray radiographic imaging with good spatial resolution was demonstrated. A spatial resolution of 440μm (10% MTF) was found. Single X-ray photon detection with a high-sensitivity camera was achieved, which potentially permits energy-resolved X-ray fluorescence imaging.
Optical readout of Micromegas gaseous detectors has been achieved by implementing a Micromegas detector on a glass substrate with a glass anode and a CMOS camera. Efficient X-ray radio-graphy has ...been demonstrated due to the integrated imaging approach inherent to optical readout. High granularity values have been reached for low-energy X-rays from radioactive sources and X-ray generators taking advantage of image sensors with several megapixel resolution. Detector characterization under X-ray radiography opens the way to different applications from beta imaging to neutron radiography. Here we will focus on one application: neutron imaging for non-destructive examination of highly gamma-ray emitting objects. This article reports the characterization of the detectors when exposed to a low activity neutron source. The response of the detector to thermal neutrons has been studied with different field configurations and gap thicknesses.
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.
MicroMegas detectors are versatile gaseous detectors which are used for ionizing particle detection. A MicroMegas detector consists of two adjacent gas-filled volumes. One volume acts as a drift ...region with an electric field operating in the ionization chamber regime, the second volume is the amplification region acting as a parallel-plate avalanche counter. The use of the microbulk technique allows the production of thin, radiation resistant, and low-mass detector with a highly variable gain. Such MicroMegas detectors have been developed and used in combination with neutron time-of-flight measurements for in-beam neutron-flux monitoring, fission and light-charged particle reaction cross section measurements, and for neutron-beam imaging. An overview of MicroMegas detectors for neutron detection and neutron reaction cross section measurements and related results and developments will be presented.
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