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Triple Gas Electron Multipliers (GEM) for slow and fast neutrons were employed at the n_TOF facility at CERN as online beam imaging monitors and for energy spectra measurements via the time-of-flight technique. The detectors were exposed to the neutron spectrum ranging from thermal to 1 GeV, produced by spallation of 20 GeV/c protons in a lead target with a maximum intensity of 7·10 12 protons per pulse. The spectrum and the 2D count distribution of the neutron beam were measured and compared at two distances from the target, 185 m and 200 m. The detectors showed radiation hardness, linear response and the ability to monitor the beam profile online with high spatial resolution. [ABSTRACT FROM AUTHOR]

The study of Soft X-ray emission can be a source of fundamental information, particularly for what concerns tokamaks and plasma diagnostics, but also in general in the fields of high energy and nuclear physics. Detection systems based on Gas Electron Multipliers (GEM) technology can be of particular use in the context of X-ray analyses, being relatively low cost while maintaining good spatial and temporal resolution and capability to sustain high counting rates (up to MHz/mm2). The development of these new and improved detectors is thus of interest, especially in the research about diagnostic and control of machines for fusion energy. In this work, the performance of a new triple-GEM detector, characterized by an aluminum metallic coating on both layers of the GEM foils, is presented and a comparison is made with the more conventional design employing copper coating. The performances of an aluminum-coated GEM (Al-GEM) detector and of a standard copper-coated GEM (Cu-GEM) detector in revealing quasi-monochromatic X-ray beams coming from different fluorescence materials are compared. The Al-GEM detector is shown to less suffer the issue of unwanted background on the signal caused by the presence of copper inside the detector itself. The suppression of this noise source encourages the use of Al-GEM detectors to perform spectroscopy in harsh environments, such as tokamak machines, where soft X-rays are useful probes to control different plasma properties and parameters. [ABSTRACT FROM AUTHOR]

The GEMTEQ is a gaseous detector with Gas Electron Multipliers for signal amplification and Timepix ASICS as highly pixelated readout. It is based on the GEMPix detector and designed for microdosimetry. This paper describes the vacuum chamber developed to house the three versions of the GEMTEQ and to operate the detector in sealed-mode and at low pressure. A sealed version avoiding the need of a gas system offers clear advantages for its transport and use, e.g., for measurements at a clinical particle therapy centre. Operating the detector at a pressure lower than atmospheric increases the spatial resolution, one of the key parameters in microdosimetry. A gas-tight detector housing, a pumping system, and a pressure and temperature monitoring system were developed and tested in operational conditions. These extensive tests have proven the vacuum chamber to be gas tight and well suited for the foreseen microdosimetric measurements: the GEMTEQ can be operated for several weeks at 1000 mbar without noticeable degradation of the detector signal. First measurements have been carried out successfully at pressure values as low as 200 mbar. Further tests are planned to reach the design goal of 10 mbar. Overall, the vacuum chamber fulfils the requirements for a sealed-mode and low-pressure operation of the GEMTEQ. Measurement campaigns using this setup for example for LET measurements in hadron beams have already been carried out and will be discussed in forthcoming papers. [ABSTRACT FROM AUTHOR]

Abstract: This paper is focused on the soft X-ray tomography system set-up at Tore Supra (DTOMOX) and the recent developments made to get precise information about plasma features from a raw or inverted data. The ultimate aim is not only to use this information in real time for visualisation but also for potential feedback, with a particular emphasis on the optimisation of the reconstruction technique and on simple analysis tools developed for an automatic treatment of these inverted data. Recent progress made on the optimisation of free parameters used for the tomographic inversion will be explained. Finally, future techniques using advanced imaging detector will be presented. In particular, preliminary investigation on the use on Tore Supra of Gas Electron Multiplier (GEM) detector for imaging purposes will be described also including some first observations in situ. [Copyright &y& Elsevier]

A triple gas electron multiplier (GEM) detector has been built and characterized in a collaboration between ENEA, INFN and CEA to develop a soft X-ray imaging diagnostic for magnetic fusion plasmas. It has an active area of 5×5cm2, 128pixels and electronics in counting mode. Since burning plasma experiments will have a very large background of radiation, this prototype has been tested with contemporary X-ray, neutron and gamma irradiation, to study the detection efficiencies, and the discrimination capabilities. The detector has been preliminarily characterized under DD neutron irradiation (2.45MeV) up to 2.2×106 n/s on the detector active area, showing a detection efficiency of about 10−4, while the detection efficiency of X-rays is more than three orders of magnitude higher. The detector has been also tested under DT neutron flux (14MeV) up to 2.8×108 n/s on the whole detector, with a detection efficiency of about 10−5. The calibration of the γ-rays detection has been done by means of a source of 60Co (gamma rays of energy 1.17MeV and 1.33MeV) and the detection efficiency was found of the order of 10−4. Thanks to the adjustable gain of the detector and the discrimination threshold of the electronics, it is possible to minimize the sensitivity to neutrons and gamma, and discriminate the X-ray signals even with very high radiative background. [ABSTRACT FROM AUTHOR]

Thermal neutron detection technologies alternative to 3He, featuring a rate capability matching the high flux expected at the European Spallation Source (ESS), are one of the main present challenges of neutron science. A new thermal neutron detection technology was recently developed named the BAND-GEM, a Gas Electron Multiplier (GEM)-based detector provided with a borated 3D converter to reach high efficiency. In this paper the results of a count rate test performed on the BAND-GEM at the ORPHEE reactor are presented. The results show that the detector can easily reach a neutron count rate of 2 MHz/cm2 while maintaining a good linearity and it is able to reach 8 MHz/cm2 with a measurable loss of linearity η and with no sign of instability. [ABSTRACT FROM AUTHOR]