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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.

We report the performance of a THick Gas Electron Multiplier (THGEM) fabricated by drilling holes in a gold-clad ceramic substrate using the standard PCB (Printed Circuit Board) technology and etching rims. The THGEM has a total thickness of 200 ?m with a hole diameter and rim size of 200 ?m and 80 ?m, respectively. In order to carry out a performance study, a detector was assembled by putting the THGEM inside a versatile chamber and irradiating it with a 55Fe X-ray source (5.9 keV). An Ar/CO2 gas mixture was flushed inside the chamber at a pressure of about 1 atm, with volume ratios varying between 70/30 and 90/10. Pulse height spectra of the detector were recorded by a multichannel analyzer to investigate the gain and energy resolution at different drift and induction electric fields. The variations in the gain and energy resolution were also interpreted using simulations. The gain and resolution data of the THGEM were compared with those of a standard GEM which was measured using the same experimental setup.

The effective gain variations as a function of the drift electric field strength ( E d ) are measured in a ceramic thick gas electron multiplier (THGEM) and a standard GEM using the same experimental setup. Significant differences in the variations are observed between the THGEM and the standard GEM. The effective gain variations with E d are quantitatively reproduced by calculations via investigating the respective influence of E d change on the electron collection efficiency and the gain. The differences in the effective gain variation with E d between the THGEM and standard GEM are thus explained.

An important instrumental development work has been done in the last two decades in the field of neutron and gamma ray spectroscopic measurements of magnetic confinement plasmas. Starting from the present state of the art instrumentation installed at JET, this paper reviews the recent development that has been carried out within the EUROFUSION programme for the forthcoming high power JET D and DT campaign. This development was dedicated to the realization of new compact neutron and gamma-ray spectrometers which combine very high energy resolution (typically better than 5%) and MHz counting rate capabilities allowing for time resolution in the 10 ms time scale. One of the advantages offered by the compact dimensions of these spectrometers is to make possible their use in multiple sight-line camera configurations, such as for future burning plasma reactors (ITER and DEMO). New compact neutron spectrometers based on single crystal diamond detectors have been developed and installed at JET for measurements of the 14 MeV neutron spectrum. Measurements on a portable DT neutron generator have shown that neutron spectroscopy of the accelerated beam ions at unprecedented energy resolution (∼1% at 14 MeV) is possible, which opens up new opportunities for diagnosing DT plasmas. For what concerns gamma ray measurements, the JET gamma ray camera has been recently upgraded with new compact spectrometers based on a LaBr3 scintillator coupled to Silicon Photomultiplier with the dual aim to improve the spectroscopic and rate capabilities of the detectors. The upgrade camera system will reconstruct the spatial gamma ray emissivity from the plasma in the MeV energy range at MHz counting rates and energy resolution in the 2-4% range. This will allow physics studies of gamma rays produced by the interaction of fast ions with impurities in the plasma and bremsstrahlung emission from runaway electrons.

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.

Silicon Carbide (SiC) is a relatively new entry in the world of solid-state detectors. Although SiC response to neutrons is more complex than the one obtained with diamonds, the measured energy resolution (FWHM/ E d 4 % ) makes SiC an interesting alternative to diamond and silicon detectors for fast neutrons. The results obtained from the measurements of the response of a 100 μ m thick SiC detector to neutrons in the energy range between 3 and 20 MeV at the n_TOF spallation source at CERN are presented in this paper. By selecting the neutron energy by means of the time of flight, the detector response to quasi-mono-energetic neutrons was measured. The main neutron-induced nuclear reactions were identified in the measured pulse height spectrum. Detection efficiency as a function of neutron energy was measured and interpreted based on available neutron cross section and by making use of Monte Carlo simulations.

The experimental thermal neutron cross sections of the 20 proteinogenic amino acids have been measured over the incident-neutron energy range spanning from 1 meV to 10 keV and data have been interpreted using the multi-phonon expansion based on first-principles calculations. The scattering cross section, dominated by the incoherent inelastic contribution from the hydrogen atoms, can be rationalised in terms of the average contributions of different functional groups, thus neglecting their correlation. These results can be used for modelling the total neutron cross sections of complex organic systems like proteins, muscles, or human tissues from a limited number of starting input functions. This simplification is of crucial importance for fine-tuning of transport simulations used in medical applications, including boron neutron capture therapy as well as secondary neutrons-emission induced during proton therapy. Moreover, the parametrized neutron cross sections allow a better treatment of neutron scattering experiments, providing detailed sample self-attenuation corrections for a variety of biological and soft-matter systems.

The BAND-GEM detector represents one of the novel thermal neutron detection devices that have been developed in order to fulfil the needs of high intensity neutron sources that, like ESS (the European Spallation Source), will start operation in the next few years. The first version of this detector featured a detection efficiency of about 40% for neutrons with a wavelength of 4A, a spatial resolution of about 6mm and a rate capability in the order of some MHz/cm2. The novelty of this device is represented by an improved 3D converter cathode (10 cm thick) based on 10B4C-coated aluminum grids positioned in a controlled gas mixture volume put on top of a Triple GEM amplifying stage. The position where the neutron interacts in the converter depends on their energy and it was observed that the first version of the detector would suffer from an efficiency decrease for long ( $> 5$ A) neutron wavelength. This paper describes how the new 3D cathode allowed improving the detection efficiency at long neutron wavelengths while keeping all the benefits of the first BAND-GEM version.

A new position-sensitive thermal neutron detector based on boron-coated converters has been developed as an alternative to today's standard 3 He-based technology for application to thermal neutron scattering. The key element of the development is a novel 3D 10 B4 C converter which has been ad hoc designed and realized with the aim of combining a high neutron conversion probability via the 10 B(n , α )7 Li reaction together with an efficient collection of the produced charged particles. The developed 3D converter is composed of thin aluminium grids made by a micro-waterjet technique and coated on both sides with a thin layer of 10 B4 C. When coupled to a GEM detector this converter allows reaching neutron detection efficiencies close to 50% at neutron wavelengths equal to 4 A. In addition, the new detector features a spatial resolution of about 5 mm and can sustain counting rates well in excess of . The newly developed neutron detector will enable time-resolved measurements of different kind of samples in neutron scattering experiments at high flux spallation sources and can find a use in applications where large areas and custom geometries of thermal neutron detectors are foreseen.

The paper describes a new compact neutron spectrometer optimized for the detection of 2.5 MeV neutrons for fusion plasma applications. The first neutron spectroscopy measurements on a nuclear fusion plasma experiment (EAST) with this detector are also reported together with the data interpretation. The detector allowed separating the different neutron emission components from the plasma and to validate the effectiveness of the Neutral Beam Injection (NBI) heating. A possible improvement of the diagnostic has been also identified in order to increase the detector sensitivity to weak components of the neutron spectrum, such as those due to the Ion Cyclotron Resonace Heating (ICRH). The relatively simple response function of the (CLYC)-L-7 detector to 2.5 MeV neutrons together with its good capability in the n/gamma discrimination, makes this detector an interesting spectrometer for deuterium (D) plasma diagnostics. In particular, its compactness allows for integration in a multi-line of sight camera where space constraints are present.

The so-called 'He-3-crisis' has motivated the neutron detector community to undertake an intense R&D programme in order to develop technologies alternative to standard He-3 tubes and suitable for neutron detection systems in future spallation sources such as the European spallation source (ESS). Boron-based GEM (gas electron multiplier) detectors are a promising 'He-3-free' technology for thermal neutron detection in neutron scattering experiments. In this paper the evolution of boron-based GEM detectors from planar to 3D converters with an application in diffraction measurements is presented. The use of 3D converters coupled with GEMs allows for an optimization of the detector performances. Three different detectors were used for diffraction measurements on the INES instrument at the ISIS spallation source. The performances of the GEM-detectors are compared with those of conventional He-3 tubes installed on the INES instrument. The conceptual detector with the 3D converter used in this paper reached a count rate per unit area of about 25% relative to the currently installed He-3 tube. Its timing resolution is similar and the signal-to-background ratio (S/B) is 2 times lower.

Lately the problem of 3He replacement for neutron detection stimulated an intense activity research on alternative technologies based on alternative neutron converters. This paper presents briefly the results obtained with new GEM detectors optimized for fast and thermal neutrons. For thermal neutrons, we realized a side-on GEM detector based on a series of boron-coated alumina sheets placed perpendicularly to the incident neutron beam direction. This prototype has been tested at n@BTF photo-production neutron facilty in order to test its effectiveness under a very high flux gamma background. For fast neutrons, we developed new GEM detectors (called nGEM) for the CNESM diagnostic system of the SPIDER NBI prototype for ITER (RFX-Consortium, Italy) and as beam monitor for fast neutrons lines at spallation sources. The nGEM is a Triple GEM gaseous detector equipped with a polyethylene layer used to convert fast neutrons into recoil protons through the elastic scattering process. This paper describes the results obtained by testing a medium size (30 × 25 cm2 active area) nGEM detector at the ISIS spallation source on the VESUVIO beam line. © 2015, Società Italiana di Fisica and Springer-Verlag Berlin Heidelberg.

The first boundary feedthroughs of the ITER heating neutral beam (HNB) injectors are key components of the neutral beam system. They allow the penetration of signals and power from/to the beam line components (BLC) and front end components (FEC), through the confinement boundary of ITER. The design status of the two types of feedthroughs is presented in the first part. This includes the design requirements, cabling strategy, the analysis done and the maintenance strategies. The second part deals with the qualification of the feedthroughs. Being made of brittle material and not covered by mechanical standard a qualification by testing strategy is proposed based on existing rules and norms. The design of the feedthroughs is almost finished and satisfies all the requirements. The next step is the procurement for their integration in the MITICA [1] test bed and the detailed definition of the qualification tests to be carried out for the HNB feedthroughs.

The research of reliable substitutes of He-3 detectors is an important task for the affordability of new neutron scattering instrumentation for future spallation sources like the European Spallation Source. GEM (Gas Electron Multiplier)-based detectors represent a valid alternative since they can combine high-rate capability, coverage of up to 1 m(2) area and good intrinsic spatial resolution (for this detector class it can be better than 0.5 mm). The first neutron diffraction measurements performed using a borated GEM detector are reported. The detector has an active area of 10 x 5 cm(2) and is equipped with a borated cathode. The GEM detector was read out using the standard ISIS Data Acquisition System. The comparison with measurements performed with standard He-3 detectors shows that the broadening of the peaks measured on the diffractogram obtained with the GEM is 20-30% wider than the one obtained by He-3 tubes but the active area of the GEM is twice that of He-3 tubes. The GEM resolution is improved if half of its active area is considered. The signal-to-background ratio of the GEM is about 1.5 to 2 times lower than that of He-3. This measurement proves that GEM detectors can be used for neutron diffraction measurements and paves the way for their use at future neutron spallation sources. Copyright (C) EPLA, 2014

The ITER project requires additional heating provided by two injectors of neutral beams resulting from the neutralization of acceleratednegative ions. To study and optimise negative ion production, the SPIDER test facility (particle energy 100keV; beam current 50A) is under construction in Padova, with the aim of testing beam characteristics and to verify the source proper operation.The SPIDER beam will be characterised by the instrumented calorimeter STRIKE, whose main components are one-directional carbon fibre carbon composite tiles. Some prototype tiles have been employed as a small-scale version (mini-STRIKE) of the entire system to investigate the features of the beam of the device BATMAN at IPP-Garching. The present contribution gives a description of the mini-STRIKE, which is made of two tiles arranged in the vertical direction and exposed perpendicularly to the beamin order to characterise the vertical beam profile. The measurement position is about 1m from the accelerator, where the beamlets composing the beam are largely overlapping. To provide local measurements of the beam features, in front of the tiles an actively cooled copper mask was located provided with some apertures. Calorimetry of the mask was performed, whereas the temperature map on the rear side of the tiles was measured by a thermal camera and compared to some local thermocouple measurements. Indicationson the beam are also provided by a thermocouple installed on the mask. The first results of the investigation of the BATMAN beam are described in various operating conditions. The data analysis is presented, including the dependence of the beam featureson plasma grid voltage, extraction voltage, radiofrequency power and filling pressure. This work was set up in collaboration and financial support of F4E.