An overview is presented of the progress since 2021 in the construction and scientific programme preparation of the Divertor Tokamak Test (DTT) facility. Licensing for building construction has been granted at the end of 2021. Licensing for Cat. A radiologic source has been also granted in 2022. The construction of the toroidal field magnet system is progressing. The prototype of the 170 GHz gyrotron has been produced and it is now under test on the FALCON facility. The design of the vacuum vessel, the poloidal field coils and the civil infrastructures has been completed. The shape of the first DTT divertor has been agreed with EUROfusion to test different plasma and exhaust scenarios: single null, double null, X-divertor and negative triangularity plasmas. A detailed research plan is being elaborated with the involvement of the EUROfusion laboratories.

In the frame of the design activities of the Divertor Tokamak Test (DTT) facility the development of a comprehensive set of neutron and gamma-ray diagnostics is on-going in order to enable measurements of: neutron yield, neutron yield rate, neutron emissivity over a poloidal section through the plasma; neutron emission spectrum; runaway electrons induced bremsstrahlung radiation and gamma-ray emission from reactions between fast ions and plasma impurities. The present paper provides an overview of the DTT neutron and gamma-ray diagnostics and describes the present status of their design including main components and interfaces, detector types and performances.

The Radial Neutron Camera (RNC) is a diagnostic system located in ITER Equatorial Port #1 providing several spatial and time-resolved parameters for the fusion power estimation, plasma control and physics studies. The RNC measures the uncollided 14 MeV and 2.5 MeV neutrons from deuterium-tritium (DT) and deuterium-deuterium (DD) fusion reactions through an array of neutron flux detectors located in collimated Lines of Sight. Signals from RNC detectors (fission chambers, single Crystal Diamonds and scintillators) need preamplification because of their low amplitude. These preamplifiers have to be as close as possible to the detectors in order to minimize signal degradation and must be protected against fast and thermal neutrons, gamma radiation and electromagnetic fields. The solution adopted is to host the preamplifiers in a shielded cabinet located in a dedicated area of the Port Cell, behind the Bioshield Plug. The overall design of the cabinet must ensure the necessary magnetic, thermal and nuclear shielding and, at the same, satisfy weight and allocated volume constraints and maintain its structural integrity. The present paper describes the nuclear design of the shielded cabinet, performed by means of 3D particle transport calculations (MCNP), taking into account the radiation streaming through the Bioshield penetrations and the cross-talk effect from the neighboring Lower and Upper Ports. We present the assessment of its nuclear shielding performances and analyze the compliancy with the alert thresholds for commercial electronics in terms of neutron flux and cumulated ionizing dose.

The paper presents an overview of the design status of the Radial Neutron Camera (RNC), that, together with the Vertical Neutron Camera, will provide, through reconstruction techniques applied to the measured line-integrated neutron fluxes, the time resolved measurement of the ITER neutron and α-source profile (i.e. neutron emissivity, neutrons emitted per unit time and volume). The RNC is composed of two subsystems, the In-Port RNC and Ex-Port RNC located, respectively, inside and outside the Plug of Equatorial Port #01. The In-Port subsystem is in a more advanced design stage since it has recently undergone the Final Design Review in the ITER procurement process. The paper describes the diagnostic layout, the interfaces, the measurement capabilities and the main challenges in its realization. Prototyping and testing of neutron detectors and electronics components were carried out and led to the choice of the component solutions that can match the environmental and operational constraints in terms radiation hardness, high temperature and electromagnetic compatibility. The performance of the RNC in terms of neutron emissivity measurement capability was assessed through 1D and 2D reconstruction analysis. It is proven that the neutron emissivity can be reconstructed in real-time within the measurement requirements: 10% accuracy, 10 ms time resolution and a/10 (a = plasma minor radius) space resolution.

This paper studies the Electromagnetic Compatibility (EMC) compliance of a diagnostic system intended for the nuclear fusion reactor ITER. Specifically, a neutron detection chain is analyzed, where the electrical signals emitted by a diamond matrix hit by neutrons. A non-conventional design of such an electronic chain is requested, to meet the specific requirements within the particular constraints imposed for such an application. This results in specific EMC issue related to the effect of common mode noise on the signal integrity. The EMC analysis is carried out on a mock-up system, and solutions to face the above issues are designed, implemented and experimentally validated.

Single Crystal Diamonds (sCD) have been selected as neutron detectors for the ITER Radial Neutron Camera (RNC). This paper investigates experimentally the hardness of these detectors to 14 MeV neutrons in order to have indications of their limits of applicability in the RNC. The experiment has been performed at the Frascati Neutron Generator (FNG) facility using three sCDs of different thickness (500, 300,100 mu m). The degradation of the sCD Charge Collection Efficiency (CCE) with increasing 14 MeV neutron fluence has been found to be lower with decreasing sCD thickness. Strong polarization effects produced by the trapping of charge carriers in the defects produced by the neutron irradiation are observed already at about 4. 10(14) n/cm(2) in the 100 mu m thick sCD. A software correction of the polarization effect is proposed, which enables to extend the sCD range of operation up to higher fluences. Taking into account such correction, a 50 mu m thick sCD is expected to reach 10(15) n/cm(2) with a CCE greater than 0.7.

Single Crystal Diamond (sCD) are candidate neutron detectors for the ITER Radial Neutron Camera (RNC) due to their capability of performing both neutron counting and spectroscopy while withstanding high levels of radiation. This paper presents a study on methods of separation between neutron and gamma events, through the analysis of the pulse shapes of a 500μm thick sCD. Methods for gamma rejection may be beneficial especially during ITER deuterium–deuterium operation to extract the 2.5 MeV neutron signal. Four neutron/gamma separation algorithms for sCD neutron detectors are presented. Three algorithms rely on pulses shape information and one on the frequency analysis. The final experimental implementation based on multi-step separation approach achieved above 90% of correctly discriminated pulses.

The present paper describes the architecture and the performances of a diamond detector data acquisition system based on PXIexpress (one of the standards suggested by ITER). Performances have been evaluated by feeding the digital acquisition system with pulses generated by a digital detector emulator replicating the shape and energy distribution expected for a Single Crystal Diamonds (sCD) neutron detector in deuterium-tritium plasmas.

In several nuclear applications, scintillators, coupled with a photomultiplier and pulse amplifier, are used in order to detect high energy particles, i.e. neutrons and gamma rays. The different particles incident on the scintillator produce electrical pulses having different shape; moreover, the amplitude of these signals is related to the particles energy. The electrical pulses of the scintillator chain are acquired by digital systems that, generally, perform a triggered acquisition consisting of a stream of pulse windows. The aim of this study is the development of a simplified clustering algorithm able to produce reference patterns in compliance with the pattern recognition algorithm based on the matched filter technique, starting from a stream of pulses generated by particles having different energy and type. This paper contains a general description of the clustering algorithm and of the main customizations performed for the scintillator signals. In order to test in real case the efficiency, the algorithm has been applied on the data acquired during a radiation test performed at Frascati Neutron Generator for Stilbene scintillator. The results show that this algorithm works properly, deriving the centroids of the clusters representing the neutron and gamma shapes, together with their occurrences in the analysed data stream.

The ITER Radial Neutron Camera (RNC) is a multichannel detection system hosted in the Equatorial Port Plug 1 (EPP 1). It is designed to measure the uncollided neutron flux from the plasma, providing information on the neutron emissivity profile and total strength. The RNC structure consists of two sub-systems based on fan-shaped arrays of cylindrical collimators: the ex-port system, covering the plasma core with 2 sets of lines of sight lying on different toroidal planes, and the in-port system, enclosed in a dedicated cassette within the EPP1 diagnostic shielding module, for the measurement of neutrons generated in the plasma edge. Due to the harsh environment in which it has to operate, the design of the in-port RNC system is particularly critical both from the measurements point of view (low signal to noise ratio induced by the high level of scattered neutrons at the detector positions) and from the structural point of view. The paper presents the results of the neutronic analyses performed with the MCNP Monte Carlo code with the aim of optimizing the in-port RNC design in order to enhance the diagnostic measurement performance and evaluating the nuclear loads that have to be withstand by its structural elements, detectors and associated components.

The main goal of the ITER Radial Neutron Camera (RNC) is to provide the plasma neutron emission profile (neutron emissivity) through measurement of the uncollided 14 MeV and 2.5 MeV neutrons from deuteriumtritium (DT) and deuterium-deuterium (DD) fusion reactions. The system is based on an array of detectors (diamonds are among the candidate detectors) located in collimated lines of sight (LOS) viewing the plasma through the ITER Equatorial Port Plug #1. Tomographic reconstruction techniques are used to calculate the neutron emissivity. The contribution of random noise on diamond detector pulses to the count rate uncertainty is investigated in this paper. The energy spectrum of the neutrons impinging on the detector has been calculated by means of MCNP calculations for one line of sight of the RNC In-Port system. The spectrum has been convoluted with the diamond detector response functions and the Pulse Height Spectrum (PHS) has been obtained. Experiments have been carried out with the CAEN (TM) 5810D detector emulator, that is able to produce arbitrary pulse height distributions as those expected in the ITER RNC. Random noise has been added on each detector pulse of the distribution using the detector emulator. The resulting uncertainty produced on the count rate has been evaluated as a function of the random noise level.

This paper describes the high-priority testing activities supporting the ITER radial neutron camera (RNC) design, performed by a consortium of European institutes within a framework contract placed by fusion for energy, the ITER European Domestic Agency. The main role of the RNC is to measure the uncollided 14- and 2.5-MeV neutrons from deuterium-tritium and deuterium-deuterium fusion reactions through an array of flux monitors/spectrometers located in collimated lines of sight viewing the plasma through the ITER equatorial port plug #1. The line-integrated neutron fluxes will be used to evaluate, through reconstruction techniques, the radial profile of the neutrons emitted per unit time and volume (neutron emissivity) and, therefore, the neutron yield and the alpha particles' birth profile. The activity of high-priority testing is dedicated to the preparation and the design of experimental test environment, the conduction of appropriate tests and reporting of test results for the high-priority prototypes, clarifying or verifying the expected key function and system behavior, and enhancing learning on specific issues (potential showstoppers).

During the International Thermonuclear Experimental Reactor (ITER) reactor operation time, the plasma will give rise to high energy neutron and gamma flux, and this intense radiation field will result in serious radiation damage and activation effects on various detectors components. In this paper, neutron detector candidates for the ITER radial neutron camera (RNC), i.e., scintillator components [crystal and plastic scintillators, optical windows, and photomultipliers (PMTs)] and single-crystal diamond detectors, were investigated to establish their radiation hardness and stability under gamma irradiation. Radiation test was carried out at the Italian National Agency for New Technologies, Energy and Sustainable Economic Development Calliope plant (Casaccia R.C., Rome, Italy). The facility is a pool-type irradiation plant equipped with a Co-60 source (energy = 1.25 MeV). Gamma radiation tests were performed in the dark and at room temperature for different total absorbed doses, as required for the application in ITER RNC. Scintillators, PMTs, and optical windows were irradiated up to around 100-kGy absorbed dose, while single-crystal diamond detectors up to around 5 MGy. Scintillators and optical windows transmittance measurements were performed in the UV-VIS range (300-700 nm), paying particular attention to the behavior at 390 and 420 nm (scintillating emission wavelengths). Samples were measured in the dark before and after irradiation and their performances were monitored at room temperature for some weeks in order to study the damage recovery in different conditions. For plastic scintillators, photobleaching and optical bleaching followed by thermal annealing processes in air were made to reduce the radiation damage. Quantum efficiency measurements were performed on the PMTs, and the pulse-height spectra and pulse shape capability of the scintillators were investigated by using gamma and neutron sources. The most relevant results of this paper concern the radiation damage observed in scintillators and diamond detectors. The crystalline scintillator sample showed much less radiation resistance than plastic scintillators. A strong damage to the silver deposition of the diamond contacts was observed already at 1.0 MGy, almost leading to contact destruction at 4.7 MGy.

The Radial Neutron Camera (RNC) of ITER (International Thermonuclear Experimental Reactor) is a multichannel detection system designed to measure the uncollided neutron flux from the fusion plasma, providing information on the neutron emissivity profiles and source strength. Fission chambers and diamond detectors are candidate detectors for the RNC In-port subsystem. This is a high radiation environment (up to ∼5 MGy gamma dose and ∼ 2×10 16 n/cm2 neutron fluence) where about 500 baking cycles up to 240 °C are foreseen over the whole ITER lifetime. In order to assess the feasibility of using diamond detectors in such harsh conditions, and to study the best technological solutions, we are currently performing a set of tests to understand the behavior of diamond detectors under radiation and thermal stresses: (1) thermal stress tests at constant temperature of 240 °C and thermal cycling between 100 °C and 240 °C; (2) gamma-hardness test up to a total dose of 4.7 MGy; (3) neutron-hardness test (limited to 2 ×1014 n/cm2 in this work).

System Level Design and Performances of the ITER Radial Neutron Camera D. Marocco, B. Esposito, G. Brolatti, M. Cecconello, D. N. Dongiovanni, O. Ficker, J.Kotula, A. Mancini, J. Mlynar, F. Moro, F. Belli, D. Bocian, C. Centioli, S. Conroy, F. Crescenzi, N. Cruz, L. Di Pace, A. Hjalmarsson, R. Kantor, D. Marzullo, G. Mazzone, R. Miklaszewski, F. Pompili, M. Riva, R. C. Pereira, S. Podda, A. Zimbal, R. Barnsley, L. Bertalot, V. Krasilnikov, A. Loarte, S. D. Pinches, A. Polevoi and B. Brichard. ENEA C. R. Frascati, Dipartimento FSN, Frascati, Italy. Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden. 3Institute of Plasma Physics of the Czech Academy of Sciences, Prague, Czech Republic. Institute of Nuclear Physics Polish Academy of Sciences, Kraków, Poland. Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal. 6 Consorzio di Ricerca per l'Energia e le Applicazioni Tecnologiche dell'Elettromagnetismo, Napoli, Italy. Institute of Plasma Physics and Laser Microfusion, Warsaw, Poland 8 Physikalisch-Technische Bundesanstalt, Braunschweig, Germany. 9ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France Fusion for Energy, Barcelona, Spain E-mail contact of main author: daniele.marocco@enea.it

Field-effect transistors (FETs) fabricated on hydrogen-terminated diamond surface have been heavily irradiated with 14.8-MeV neutrons in order to evaluate their possible application in very high neutron fluence environments. The dc performance of the diamond-based FETs, such as drain saturation current and maximum transconductance, has been studied as a function of a 14.8-MeV neutron fluence up to 1014 n/cm 2 , delivered in five steps. The effects on electrical properties of H-terminated diamond surface have also been investigated during the neutron irradiation experiments. The Hall parameters, i.e., sheet hole concentration, hole mobility, and sheet resistance, were monitored before and after each irradiation. The performance remains stable during all the neutron fluence steps, thus assessing a remarkable radiation hardness of diamond-based devices. To the best of our knowledge, this is the first published data on 14-MeV neutron tolerance of diamond FET devices.

In this paper we present the measurement of the response of 50 pm thin diamond detectors to 14 MeV neutrons. Such neutrons are produced in fusion reactors and are of particular interest for ITER neutron diagnostics. Among semiconductor detectors diamond has properties most appropriate for harsh radiation and temperature conditions of a fusion reactor. However, 300-500 pm thick diamond detectors suffer significant radiation damage already at neutron fluences of the order of 10(14) n/cm(2). It is expected that a 50 mu m thick diamond will withstand a fluence of >10(16) n/cm(2). We tested two 50 mu m thick single crystal CVD diamonds, stacked to form a "sandwich" detector for coincidence measurements. The coincidence between two diamonds allows to suppress background and increase detection efficiency. The detector measured the conversion of 14 MeV neutrons, impinging on one diamond, into a particles which were detected in the second diamond in coincidence with nuclear recoil. For C-12(n, alpha)Be-9 reaction the total energy deposited in the detector gives access to the initial neutron energy value. The measured 14 MeV neutron detection sensitivity through this reaction by a detector of an effective area 3 x 3 mm(2) was 5 x 10(-7) counts cm(2)/n. This value is in good agreement with Geant4 simulations. The energy resolution of the detector was found to be 870 keV FWHM, but according to Geant4 simulations only about 160 keV FWHM were intrinsic. (C) 2016 Elsevier B.V. All rights reserved.

In this paper we describe the development and first tests of a neutron spectrometer designed for high flux environments, such as the ones found in fast nuclear reactors. The spectrometer is based on the conversion of neutrons impinging on Li-6 into alpha and t whose total energy comprises the initial neutron energy and the reaction Q-value. The (LiF)-Li-6 layer is sandwiched between two CVD diamond detectors, which measure the two reaction products in coincidence. The spectrometer was calibrated at two neutron energies in well known thermal and 3 MeV neutron fluxes. The measured neutron detection efficiency varies from 4.2 x 10(-4) to 3.5 x 10(-8) for thermal and 3 MeV neutrons, respectively. These values are in agreement with Geant4 simulations and close to simple estimates based on the knowledge of the Li-6(n,alpha)t cross-section. The energy resolution of the spectrometer was found to be better than 100 keV when using 2.5 or 5 m cables between the detector and the preamplifiers. (C) 2015 Elsevier B.V. All rights reserved.

A prototype of neutron spectrometer based on diamond detectors has been developed. This prototype consists of a 6 Li neutron converter sandwiched between two CVD diamond crystals. The radiation hardness of the diamond crystals makes it suitable for applications in low power research reactors, while a low sensitivity to gamma rays and low leakage current of the detector permit to reach good energy resolution. A fast coincidence between two crystals is used to reject background. The detector was read out using two different electronic chains connected to it by a few meters of cable. The first chain was based on conventional charge-sensitive amplifiers, the other used a custom fast charge amplifier developed for this purpose. The prototype has been tested at various neutron sources and showed its practicability. In particular, the detector was calibrated in a TRIGA thermal reactor (LENA laboratory, University of Pavia) with neutron fluxes of 108 n/cm2s and at the 3 MeV D-D monochromatic neutron source named FNG (ENEA, Rome) with neutron fluxes of 106 n/cm2s. The neutron spectrum measurement was performed at the TAPIRO fast research reactor (ENEA, Casaccia) with fluxes of 109 n/cm2s. The obtained spectra were compared to Monte Carlo simulations, modeling detector response with MCNP and Geant4.