In this paper we present the design of a photon pre-amplifier based on a photo-cathode coated Thick Gas Electron Multiplier (THGEM). Such device is crucial in application where a weak light signal produced in a radiation detector must be amplified so that it can be carried to a photo-detector by means of optical fibres. An example of a device where a light signal must be amplified is a gamma-ray Cherenkov detector for fusion power measurements in magnetic confinement devices. In such application the active part of the detector must be located very close the plasma, typically in a harsh radiation environment where standard photodetectors cannot operate. The photon pre-amplifier allows to increase the signal generated in the active part of the detector so that it can be easily detected by the photodetector located outside the harsh environment. We present the conceptual design of a THGEM based photon pre-amplifier supported by Garfield++ simulations. The device working principle is the following: primary photons impinge on the photo-cathode and extract electrons that are accelerated by the THGEM electric field. Upon collisions with the accelerated electrons, the gas molecules in the pre-amplifier are brought to excited states and de-excite emitting scintillation photons. Since each electron excites multiple gas molecules, the scintillation photons outnumber the primary photons, leading to the amplification. In addition, we present the first observation of measurements of Nitrogen gas scintillation in a THGEM device. We devised an experimental setup consisting of a vacuum chamber containing a THGEM and an alpha particle source. The vacuum chamber is filled with pure nitrogen and is coupled to a photomultiplier tube via a view-port to detect the scintillation photons generated in the THGEM. For sake of simplicity the electrons that induce the scintillation are generated by the ionization track of an alpha particle rather than by the THGEM photo-cathode coating. A good qualitative agreement between simulations and experiment has been found, however no quantitative conclusions can be made due to the lack of N2 excitation cross sections in the Garfield++ code.

GyM is a linear plasma device operating at Istituto per la Scienza e Tecnologia dei Plasmi, Consiglio Nazionale delle Ricerche, Milan, with the original aim of studying basic plasma physics, such as turbulent processes. Since 2014, GyM experimental program has been mainly focused on the issue of plasma-material interaction (PMI) for magnetic confinement nuclear fusion applications. GyM consists of a stainless steel vacuum chamber (radius and length of 0.125 m and 2.11 m), a pumping system, a gas injection system, 10 magnetic field coils and two magnetron sources at 2.45 GHz, capable of delivering a total microwave power up to 4.5 kW. Highly reproducible steady-state plasmas of different gas species, at a maximum working pressure of ~10-1 Pa, can be obtained by electron cyclotron resonance heating in the resonance layer at 87.5 mT. Plasmas of GyM have electron and ion temperature <=15 eV and ~0.1 eV, respectively. The electron density is in the range of 1015-1017 m-3 and the ion flux is <=5 × 1020 ions?m-2s-1. Main plasma diagnostics of GyM comprise Langmuir probes, an optical emission spectrometer, a mass spectrometer and a fast camera system equipped with an image intensifier unit. For the purpose of investigating the topic of PMI, GyM is provided with two sample exposure systems. Both are biasable at a negative bias voltage down to -400 V, to tune the energy of the impinging ions. One of them is also equipped with a heating lamp and can reach and sustain a temperature of 990 K for several hours, thus allowing to study the role of sample temperature during the plasma-material interaction. This contribution presents the layout of GyM, the diagnostics, the sample exposure systems and the typical plasma parameters. A brief overview of the main PMI activities carried out so far and a description of future machine upgrades are also given.

Since the 2018 IAEA FEC Conference, FTU operations have been devoted to several experiments covering a large range of topics, from the investigation of the behaviour of a liquid tin limiter to the runaway electrons mitigation and control and to the stabilization of tearing modes by electron cyclotron heating and by pellet injection. Other experiments have involved the spectroscopy of heavy metal ions, the electron density peaking in helium doped plasmas, the electron cyclotron assisted start-up and the electron temperature measurements in high temperature plasmas. The effectiveness of the laser induced breakdown spectroscopy system has been demonstrated and the new capabilities of the runaway electron imaging spectrometry system for in-flight runaways studies have been explored. Finally, a high resolution saddle coil array for MHD analysis and UV and SXR diamond detectors have been successfully tested on different plasma scenarios.

The development of MITICA, the prototype for a neutral beam injector for ITER, drives the interest in investigating high HV insulation in vacuum. The High Voltage Padova Test Facility (HVPTF) is an experimental device with the aim of studying the fundamental processes leading to discharges, offering a framework to develop new diagnostics, models, and mode of operations for MITICA. For this purpose, HVPTF features a vacuum chamber containing two electrodes which can achieve an HV difference up to 800 kV. X-ray bremsstrahlung radiation produced by free charges accelerated by the HV was proven to be a promising monitoring mechanism in the past; as such, two scintillating crystals, a LYSO and a LaBr 3, coupled with fast electronics were used to conduct hard X-ray spectroscopy. This work describes a newly custom-developed software tool to analyze the spectroscopy from scintillators and integrate it with the HVPTF analog data. The tool was employed to study two experimental sessions, reaching promising results in the characterization of microdischarges, especially in terms of time resolution. Detection limits imposed by pile-up and other processes were identified and addressed, finding the best range of operation of the two scintillators. The performed study opens the way for the analysis of data obtained in all 2020 and 2021 experimental campaigns, thus giving the possibility to implement future improvements in HVPTF X-ray spectroscopy.

At present, the only method for assessing the fusion power throughput of a reactor relies on the absolute measurement of 14 MeV neutrons produced in the D-T nuclear reaction. For ITER and DEMO, however, at least another independent measurement of the fusion power is required. The 5He* nucleus produced in the D-T fusion reaction has two de-excitation channels. The most likely is its disintegration in an alpha particle and a neutron, D + T -> 5He* -> ? + n, by means of the nuclear force. There is however also an electromagnetic channel, with a branching ratio ~10-5, which leads to the emission of a 17 MeV gamma-ray, i.e. D + T -> 5He* -> 5He + ?. The detection of this gamma-ray emission could serve as an independent method to determine the fusion power. In order to enable 17 MeV gamma-ray measurements, there is need for a detector with some coarse energy discrimination and, most importantly, capable of working in a neutron-rich environment. Conventional inorganic scintillators, such as LaBr3(Ce), have comparable efficiencies to neutrons and gamma-rays and they cannot be used for 17 MeV gamma-ray measurements without significant neutron shielding. In order to overcome this limitation, we here propose the conceptual design of a gamma-ray counter with a variable energy threshold based on the Cherenkov effect and designed to operate in intense neutron fields. The detector geometry has been optimized using Geant4 so to achieve a gamma-ray to neutron efficiency ratio better than 105. The design is based on a gas Cherenkov detector and the photo-sensor is still to investigated.

Among other effects of interest for the optimisation of fusion plasma machines, plasma-wall interaction is one of the most investigated. Through plasma-wall interaction, the first wall material may be eroded and impurities enter into the plasma, where they can produce soft X-rays (SXR) from 5 to 20 keV. To study the rate and energy of such SXR emission it is necessary to develop adequate SRX diagnostic devices. One of the best choices is represented by gas detector based on Gas Electron Multiplier (GEM) technology. GEM detectors are very promising thanks to their possibility to cover large areas, good detection efficiency, good spatial resolution (in the order of 5 mm), and capability to sustain high counting rates (>MHz/mm2). The latter feature, in particular, is possible thanks to the use of a custom electronic readout called GEMINI, an ASIC in 180 nm CMOS. This paper shows the characterisation of a triple GEM detector equipped with GEMINI readout and optimised for SXR detection with Aluminium GEM foils, instead of the standard copper GEM foils. Copper in fact has a prominent 8.04 keV K-alpha line which is in the same energy region of the interesting SXR emission, thus forbidding its use as part of an optimised diagnostic for this application; Aluminium, on the other hand, only emits X-rays at 1.5 keV. GEMINI ASIC is made of a charge preamplifier (providing an analog signal proportional to the charge deposited into the detector) and a discriminator providing a digital Time-over-Threshold (ToT) signal. Operating in ToT, this digital electronics can sustain rates in the order of MHz per channel. In this paper, a careful study and comparison of digital ToT and analog signals is performed with pulses obtained in realistic conditions (with different X-rays sources). Spectral distribution of the sources (in particular, of Molybdenum and Titanium) have been obtained from both kind of signals; because no significant differences have been found, the two implemented procedures are demonstrated to be equivalent. In conclusion, we demonstrate that the GEMINI-based electronic readout chosen for GEM detectors is adequate to sustain the high SXR rate from the plasma.

At present, the only method for assessing the fusion power throughput of a reactor relies on the absolute measurement of 14 MeV neutrons produced in the D-T nuclear reaction. [1] For ITER and DEMO, however, at least another independent measurement of the fusion power is required. The 5Henucleus produced in the D-T fusion reaction has two de-excitation channels. The most likely is its disintegration in a particle and a neutron, D+T->5He->?+n, by means of the nuclear force. There is however also an electromagnetic channel, with a branching ratio ~10-5, which leads to the emission of a 17 MeV gamma-ray, i.e. D+T->5He*-> 5He+?. [2] The detection of this gamma-ray emission could serve as an independent method to determine the fusion power. In order to enable 17 MeV gamma-ray measurements, there is need for a detector with some coarse energy discrimination and, most importantly, capable to work in a neutron rich environment. Conventional inorganic scintillators, such as LaBr3(Ce), have comparable efficiencies to neutrons and gamma rays and they cannot be used for 17 MeV gamma-ray measurements without significant neutron shielding. In order to overcome this limitation, we here propose the conceptual design of a gamma ray counter with a variable energy threshold based on the Cherenkov effect and designed to operate in intense neutron fields. The detector geometry has been optimized using Geant4 so to achieve a gamma-ray to neutron efficiency ratio better than 105. The design is based on a gas Cherenkov detector and uses a CsI coated scintillating GEM (Gas Electron Multiplier) as photon pre-amplifier, together with a wavelength shifter to minimize the sensitivity to neutrons. Photons produced in the GEM are collected by an optical window and a bundle of optical fibers, which guides them towards an array of silicon photomultipliers (SiPMs) located further away from the plasma, in a region at low nuclear radiation.

The development of MITICA, the prototype for a neutral beam injector for ITER, drives the interest in investigating HV insulation in vacuum. The High Voltage Padova Test Facility (HVPTF) is an experimental device which has the double aim of studying the physical phenomena underlying the voltage holding in vacuum and testing technical solutions to increase the breakdown threshold. HVPTF features a vacuum chamber containing two stainless steel electrodes separated by an adjustable gap of few centimeters. Electrodes are available in different shapes and can achieve an HV difference up to 800 kV. Both the current and the voltage of the electrodes are sampled at a 100 Hz rate along with the vacuum pressure and the gas composition. Two scintillating crystals, a LYSO and a LaBr3, are installed to detect the hard X-ray bremsstrahlung radiation produced by the interaction of the free charges accelerated by the HV difference on the electrode surfaces. Both scintillators are coupled to photomultipliers and have small active volumes and fast electronics, resulting in very fast signals (40-100 ns); this minimizes the pile-up effect and enhances time resolution, allowing for the measurement of X-ray emission spectra to up to 500 keV with a time-width of few hundreds of ?s. The electrodes are subject to a conditioning process through which the breakdown voltage is gradually increased until the system reaches a saturation value. Between major breakdown discharges a series of current micro-discharges are observed, during which the number of bremsstrahlung photons drops almost to zero. A global increase in gas emission is measured in correspondence of such events, likely due to degassing induced by the discharges. The aim of this contribution is to expand the knowledge around the micro-discharge dynamics focusing on the bremsstrahlung spectra obtained through the scintillators. Different micro-discharge types will be characterized and put in relation with the different electrodes and the conditioning phase.

The diagnosis of soft X-ray (SXR) emission from tokamaks represents a unique source of information, since it allows the study of several plasma parameters, such as the electron and ion temperature, the investigation of the ionization equilibrium, particle and runaway transport and the study of MHD fluctuations and disruptions. A new 2D-SXR diagnostic system called EXODUS (Enhanced X-ray Optimized Detector for Use in multiple Scenarios) has been developed with the aim to combine 2D energy resolved SXR emission profiles from the plasma with a high time (< 0.1 ms) and spatial resolution (< 3 mm2). The EXODUS system is based on the Gas Electron Multiplier (GEM) technology coupled with a padded anode readout and a new data acquisition system custom designed for GEM called GEMINI. In this contribution we will describe the laboratory characterization carried out on the first detector prototype using a quasi-monochromatic X-rays beam at very high rate (> 150 MHz) and the design of a enhanced version of the detector that is planned for installation on a tokamak in the near future. Preliminary measurements taken on plasma will be also shown.

Neutron spallation sources always require new instrument upgrades and innovations in order to improve the quality of their experiments. In this framework, the capability to accurately measure total neutron cross sections at the VESUVIO instrument at the ISIS Facility can be boosted by a tailored transmission detector. For this reason, the first double ceramic thick GEM detector has been realised. Detectors based on GEM technology are broadly developed thanks to their characteristics, such as good spatial resolution (< 0.5 mm), good detection efficiency, high rate capability (MHz/mm(2)) and a possible coverage area of some meters at low costs. This article shows the realisation of a GEM detector made of a (B4C)-B-10 cathode, two ceramic thick GEM foils and a padded anode, as well as the device characterisation on the VESUVIO beam line, where stability, gamma-sensitivity, imaging capability and sample analysis have been studied. The successful results confirm that the ceramic thick GEM detector performs well in thermal and epithermal neutron detection and it will allow the scientific user community of the instrument to perform better quality transmission measurements so as to determine more accurate total neutron cross section of condensed-matter systems.

One of the main configuration of Fast Ion Loss Detectors (FILD) installed in present day tokamaks and stellarators consists of a collimator and a scintillator coupled to a suitable optical system. In view of their use at the JT-60SA and ITER tokamaks, the impact of the background radiation induced by fusion born neutrons on the instrument must be quantified. In JT-60SA the interaction is predominantly due to 2.5 MeV neutrons born from D -D reactions while, at ITER, 14 MeV neutrons born from D -T are of additional concern, as their flux is expected to be the same as the one from the escaping ions at the position of the FILD. In particular, the generation of background charged particles when neutrons interact with the FILD supporting structure is of most relevance, both at JT-60SA and ITER. In this work we present the results of a study on the neutron sensitivity of the whole FILD setup to 2.5 MeV and 14 MeV neutrons. A set of GEANT4 simulations with a detector geometry derived from the current CAD model of the proposed FILD design has been carried out. Modelling has been validated at the Frascati Neutron Generator, where aspects of the interaction of MeV range neutrons with the FILD setup have been tested. Based on our simulations, we predict that neutrons will induce a measurable background on the FILD, both at JT-60SA and ITER, but they will also not impede measurements.

The High Voltage Padova Test Facility (HVPTF) is an experimental device for investigating HV insulation in vacuum, in support of the realization of MITICA, the prototype of a neutral beam injector for ITER. The facility investigates the physical phenomena underlying voltage holding in vacuum, such as the mechanisms causing breakdowns and the electrode conditioning process, along with testing technical solutions to increase the breakdown threshold. Inside a high vacuum chamber, two stainless steel electrodes, separated by a few centimetres gap, can achieve HV values for a maximum of 800 kV potential difference. The conditioning process consists of the gradual increase of the breakdown voltage in time, until the system achieves a saturation value. Between two consecutive breakdown events, current micro-discharges involving the electrodes are observed; high energy X-rays (up to hundreds of keV) and a global increase of gas emission (in particular H 2 and CO 2 are detected by the Residual Gas Analyser) are measured in correspondence to the current events. Two new X-rays detectors have been recently installed: a small LYSO and a LaBr 3 (Ce) scintillating crystals, coupled to photomultipliers. They all are small sized scintillators, with very fast pulses (40-100 ns) in order to minimize pileup effects during the high intensity discharges. However, the high Z and densities guarantee a full energy absorption of the X-rays (they can measure up to 500 keV), with a significant probability, in spite of the small sizes. In this contribution we present a characterization of the microdischarge dynamics occurring during the conditioning phase, focusing on the new details uncovered via the new diagnostics.

The High Voltage Padova Test Facilities (HVPTF) is a R&D project focused on understanding the physical processes behind breakdown and micro-discharges in high-voltage insulation, as well as developing new diagnostics, models, and operational modes to address these challenges and aid in the stable operation of MITICA. The X-rays produced during breakdown have a spectrum that extends from low energy (~ keV) up to several hundreds of keV and a flux that can reach 10 6 photons/cm 2 s. This paper shows the development and preliminary results of a newly designed X-Ray diagnostic based on Gas Electron Multiplier (SXR-GEM). This detector is able to stand very high rate (> MHz) in single photon counting mode and can cover the energy range from 3-50 keV. The XR-GEM detector is equipped with anodic pads (256 pads 6x6 mm 2 ) readout with a new data acquisition system called GEMINI, which gives the possibility to obtain a counting rate of several MHz and sub-ms time resolution together with mm spatial resolution. Preliminary measurement shows that this kind of diagnostic is able to reconstruct the time evolution of the discharge at very high rates and to provide X-rays imaging.

A state-of-the-art EJ276 plastic scintillator-based detector for neutron spectroscopy has undergone detailed characterization both in a controlled laboratory and on-site at the SPIDER negative ion source facility in Padua. The device will be used for the spectroscopy of 2.5 MeV neutrons produced from Deuterium-Deuterium fusion reactions occurring inside the SPIDER beam dump. A plastic based scintillator with neutron/gamma discrimination has some key advantages over the commonly used organic liquid scintillators with regards economic cost and handling safety. The purpose of this characterization is to determine the operational functionality and reliability of this new breed of detector material. Several tests were performed to verify expected operation with regards to signal reproducibility, long-term stability, and pulse shape discrimination (PSD) capabilities. It was found that the detector system (EJ276 scintillator + photomultiplier tube) performed well in terms of reproducibility and PSD, however the long-term stability of the scintillator light output was seen to diminish considerably over time (>50% decrease) and must be consistently monitored in order to have an accurate conversion scale needed for energy spectroscopy.

The High Voltage Padova Test Facility (HVPTF) is an experimental device for investigating HV insulation in vacuum, in support of the realization of MITICA, the prototype of a neutral beam injector for ITER. The facility investigates the physical phenomena underlying voltage holding in vacuum, such as the mechanisms causing breakdowns and the electrode conditioning process, along with testing technical solutions to increase the breakdown threshold. Inside a high vacuum chamber, two stainless steel electrodes, separated by a few centimetres gap, can achieve HV values up to 400 kV each. The conditioning process consists of the gradual increase of the breakdown voltage in time, until the system achieves a saturation value. Between two consecutive breakdown events, current micro-discharges involving the electrodes are observed; high energy X-rays (up to hundreds of keV) and a global increase of gas emission (in particular H2 and CO2 are detected by the Residual Gas Analyser) are measured in correspondence to the current events. Three new Xrays detectors have been recently installed: a small LYSO (4 × 4 × 20 mm3), a LaBr3 (1" x 3/4") and a thin YAP (1"x 2 mm) scintillating crystals, coupled to photomultipliers. They all are small sized scintillators, with very fast pulses (40-100 ns) in order to minimize pile-up effects during the high intensity discharges. However, the high Z and densities guarantee a full energy absorption of the X-rays (they can measure up to 500 keV), with a significant probability, in spite of the small sizes. Energy resolutions are less than 9%. In this contribution we present a characterization of the micro-discharge dynamics occurring during the conditioning phase, focusing on the new details uncovered via the new diagnostics.

The inaugural Deuterium acceleration campaign in the SPIDER negative ion source facility in Padua has recently taken place. The first neutrons generated by Deuterium-Deuterium fusion reactions (2.5 MeV) have been recorded, occurring from the collision of accelerated Deuterium with Deuterium absorbed by the beam dump of SPIDER. A neutron detector based on a novel EJ276 plastic scintillator has been employed to successfully measure the neutron flux, which shows strong agreement with the extracted current of the acceleration grid. We have performed a neutron-gamma pulse shape discrimination characterization of the EJ276 detector at the ISIS Neutron source (241AmBe up to 10 MeV), as well as direct spectroscopic comparisons of the D-D neutrons with data from the Frascati Neutron Generator (241AmB quasi-monoenergetic 2.5 MeV). Despite the low statistics produced in this first campaign, both pulse shape discrimination and spectral analysis of the fusion neutrons was viable. The success of these first measurements has led to the installation of an array of 6 new scintillators to be used for further physical studies in future campaigns.

SPIDER, the full size ITER NBI ion source, aims to prove the ITER requirements in terms of the ion source performance, a beam uniformity better than 90% and a low beam divergence. The SPIDER experiment can operate in deuterium, thus producing beam-target D-D fusion neutron emissions. These emissions can be used to evaluate the beam uniformity as well as machine parameter dependence, since the neutron flux is proportional to the beam power. To this end, a new neutron diagnostic array, consisting of a mix of seven crystal, plastic, and liquid scintillators, has been installed externally on the beam dump side of the vessel. Six of them are capable of neutron/gamma discrimination and are positioned to study the beam uniformity and allow parametric comparisons. An NaI scintillator-based gamma detector allows for the energy spectra reconstruction of incident gamma rays without neutron interference. In this work, the scintillator array's capability and arrangement, together with first results achieved during the deuterium campaigns performed in SPIDER, are presented and discussed.

This paper presents the Mechanical Ventilator Milano (MVM), a novel intensive therapy mechanical ventilator designed for rapid, large-scale, low-cost production for the COVID-19 pandemic. Free of moving mechanical parts and requiring only a source of compressed oxygen and medical air to operate, the MVM is designed to support the long-term invasive ventilation often required for COVID-19 patients and operates in pressure-regulated ventilation modes, which minimize the risk of furthering lung trauma. The MVM was extensively tested against ISO standards in the laboratory using a breathing simulator, with good agreement between input and measured breathing parameters and performing correctly in response to fault conditions and stability tests. The MVM has obtained Emergency Use Authorization by U.S. Food and Drug Administration (FDA) for use in healthcare settings during the COVID-19 pandemic and Health Canada Medical Device Authorization for Importation or Sale, under Interim Order for Use in Relation to COVID-19. Following these certifications, mass production is ongoing and distribution is under way in several countries. The MVM was designed, tested, prepared for certification, and mass produced in the space of a few months by a unique collaboration of respiratory healthcare professionals and experimental physicists, working with industrial partners, and is an excellent ventilator candidate for this pandemic anywhere in the world.