A gas electron multiplier (GEM)-based detector was utilized for the first time on a spherical tokamak, MAST-U, during the 2023 campaign to investigate soft x-ray (SXR) radiation (1-20 keV) emitted from the plasma. GEM detectors, chosen for their resilience to harsh fusion environments and their ability to provide energy-resolved (E-res similar to 25% at 8 keV) SXR emission images (with a spatial resolution of few centimeters) with sub-millisecond time resolution, are a relatively new diagnostic compared to standard semiconductor diodes. In this study, the GEM detector features a pinhole geometry outside the vacuum chamber and observes the plasma through a beryllium window. Filled with an ArCO2 mixture, the detector consists of an Aluminized Mylar cathode, three Aluminum-coated GEM foils, and an anode made of a 16 x 16 matrix of 6 mm(2) pads for 2D readout. It employs custom GEMINI ASICs (Application Specific Integrated Circuits) for signal readout, enabling single photon-counting techniques with Time over Threshold analysis on each detector channel, for a maximum rate of 1 MHz per channel. Preliminary results from the 2023 campaign highlight the GEM detector's ability to complement existing SXR camera systems by adding energy-resolved information to the spatial and temporal data. Case studies demonstrate the detector's capability to capture Magnetohydrodynamic instabilities, such as Snake instabilities, while utilizing its energy-resolved measurements to analyze plasma events, including Internal Reconnection Events. Additionally, the GEM detector enables the estimation of Electron Temperature in Maxwellian plasmas from SXR measurements. These findings underscore the potential of the GEM-based diagnostic system to enhance the understanding of tokamak plasmas by providing simultaneous spatial, temporal, and energy-resolved insights.

In the context of magnetic confinement fusion, the Megavolt ITER Injector and Concept Advancement (MITICA) project is supported by another experiment called High-Voltage Padova Test Facility (HVPTF): a device designed to improve the knowledge of high voltage holding in a vacuum. HVPTF includes a vacuum chamber containing two electrodes separated by an insulator or a vacuum gap, across which electrical discharges can develop. The electrodes are powered by two independent Cockcroft-Walton power supplies, allowing for a total voltage difference up to 800 kV. The current, voltage, and pressure inside the chamber are monitored at a sampling rate of 100 Hz. Studying the physics behind electrical discharges is fundamental to prevent their development in MITICA, where they can lead to structural damage to the experimental components. For this reason, in April 2022, a gas electron multiplier (GEM) detector was installed at HVPTF, allowing to perform X-ray measurements resolved in time, space, and energy at high rates ( >1 MHz ) without incurring severe pile-up problems. This work describes the analysis of data coming from current, voltage, and pressure sensors, and the X-ray GEM (XR-GEM) detector at HVPTF during two 2022 experimental campaigns. Correlations between sensor signals with the X-ray measurements have been highlighted. Experimental results indicate the presence of characteristic X-ray emissions from anode atoms during electrical discharge events in the needle-plane electrode configuration. An algorithm was developed for generating synthetic detector data based on user-defined X-ray emissions within the vacuum chamber and performing tomographic reconstructions using actual or synthetic detector data. Preliminary results indicate possible gas emissions from the anode's surface during electrical discharge events.

Inertial Confinement Fusion and Magnetic Confinement Fusion (ICF and MCF) follow different paths toward goals that are largely common. In this paper, the claim is made that progress can be accelerated by learning from each other across the two fields. Examples of successful cross-community knowledge transfer are presented that highlight the gains from working together, specifically in the areas of high-resolution x-ray imaging spectroscopy and neutron spectrometry. Opportunities for near- and mid-term collaboration are identified, including in chemical vapor deposition diamond detector technology, using gamma rays to monitor fusion gain, handling neutron-induced backgrounds, developing radiation hard technology, and collecting fundamental supporting data needed for diagnostic analysis. Fusion research is rapidly moving into the igniting and burning regimes, posing new opportunities and challenges for ICF and MCF diagnostics. This includes new physics to probe, such as alpha heating; increasingly harsher environmental conditions; and (in the slightly longer term) the need for new plant monitoring diagnostics. Substantial overlap is expected in all of these emerging areas, where joint development across the two subfields as well as between public and private researchers can be expected to speed up advancement for all.

The design of a compact 2 x 2 diamond matrix with independent and redundant pixels optimized for the spectrometric neutron camera of the SPARC tokamak is presented in this article. Such a matrix overcomes the constraints in dynamic range posed by the size of a single diamond sensor while keeping the ability to perform energy spectral analysis, marking a significant advancement in tokamak neutron diagnostics. A charge pre-amplifier based on radio frequency amplifiers based on InGaP technology transistors, offering up to 2 GHz bandwidth with high robustness against radiation, has been developed. A first single-channel device has been tested and proven to provide a fast signal development time of 20-25 ns, necessary to mitigate pileup effects while offering precise energy measurements. As the diamond sensors may suffer from polarization effects due to the trapping of charges at the diamond/metal interface, a periodical bias inversion can guarantee optimal performance. To facilitate that, a reversible high voltage power supply has been developed. The ongoing development of data acquisition equipment and real-time processing algorithms based on programmable gate arrays further enhances the neutron camera's capabilities.

A multipurpose software, called Revolt, has been developed to fully exploit the imaging capabilities of Triple-GEM 2D cameras for X-rays and neutrons detection. Both tomographic inversion techniques and synthetic data production methods are based on the modeling of a transport matrix between the 2D spatially resolved signal on a detector and the 3D signal emission in the experimental space. The core task of the Revolt software is to provide a transport matrix between the two quantities via a numerical-geometrical approach. The method is based on the analytical evaluation of detector pixels Line Of Sight generated via a Monte Carlo method to include obstacle shading on the detector image. The Revolt implementation and validation are described in this work, which provides a solid base for future application of tomographic inversion techniques in the context of fusion plasma physics.

Neutron detection is nowadays mostly based on 3He gas detectors, but its shortage and the continuous upgrades of the neutron facilities require new devices to perform experiments with maximum performances. This work presents a new detector based on the Gas Electron Multiplier (GEM) combined with several boron layers. This detector combines the features of GEM technology with the properties of boron as a neutron converter and the device is produced to sustain high neutron fluxes with high detection efficiency. The detector has been characterised at the ISIS Pulsed Neutron and Muon Source (UK). Based on the analysis of our results, the detector has shown a good response to thermal and epithermal neutrons reaching a detection efficiency of 16% at 1.8 & Aring; (25 meV). The good detection efficiency (even increasable with the addition of further boron GEM foils) and the good time resolution, make the detector a unique device for the neutron techniques. In particular, its use can easily be envisaged in techniques involving neutron transmission measurements, that require high fluxes impinging on the detectors, with the added bonus of a 2D-resolved capability due to the padded anode.

Thermal neutron imaging can be a useful tool in the study of the internal structure of an object. The different attenuation properties of the materials with respect to X rays give rise to different interactions and the result is a complementary non-destructive analysis, which can provide important additional information. This technique has been successfully employed in different areas of work, especially in material science and cultural heritage studies. This paper describes the development of a new detection system and its characterization performed with X ray emissions. The system features the use of a gaseous detector, based on the Gas Electron Multiplier technology, and a fully digital electronic readout, with a combination of custom-made ASICs (called GEMINI) and FPGA boards, enabling fast single photon counting. The detector can be thus used directly for X ray imaging, while the addition of a suitable converter in its active volume will allow for detection of neutrons and for reconstruction of their tracks. The readout system is based on a x-y strip structure and features the reconstruction of single events through the center of mass methodology, allowing for accurate tomography, with sub-mm spatial resolution, in combination with sub-ms time resolution and high rate capabilities (up to MHz/mm 2 ).