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The main purpose of the divertor tokamak test (DTT) facility is to study alternative solutions to mitigate the issue of the power exhaust, under integrated physics and technical conditions relevant to ITER and DEMO. One of the most complex and innovative subsystems of the entire project is certainly the negative-ion-based neutral beam injector (NBI), meant to inject 10 MW of auxiliary power with a beam of 510 keV deuterium neutrals. This contribution describes the conceptual design of the beamline for the DTT NBI system, with a particular focus on the innovative technical solutions adopted to fulfill the requirements and maximize the performance. The DTT NBI is required to operate with high efficiency in several operating scenarios, covering a large range of beam energies, between 10% and 100% of the nominal value (510 keV). To reach this challenging goal, an innovative accelerator design, the spherical and lemon hyperlens grids (SLHGs), has been developed. The implementation of this design concept of the accelerator has recently become possible thanks to recent improvements in additive manufacturing (AM) technology. Another original aspect of the DTT NBI, compared to existing devices, regards the vacuum pumping system, which will be based on nonevaporable getter (NEG) pumps. This will represent the first application of the NEG technology to an NBI for the heating and current drive system of a fusion experiment, with a possible simplification of the overall construction, with respect to typical solutions based on cryogenic pumps. Other innovative solutions are the cylindrical sawtooth structure (CSS) for the neutralizer panels and the stray field shielding system (SFSS) with encapsulated neutralizer. This article provides an overview of the injector for DTT NBI with a particular focus on innovative technical solutions.

An overview of the recent operations and the main results of cesium injection in the Source for the Production of Ions of Deuterium Extracted from Rf plasma (SPIDER) negative ion source are described in this contribution. In experiments without cesium injection, all SPIDER plants were tested to verify the basic expectations on the operational parameters (e.g., electron cooling effectiveness of magnetic filter field) and to determine its operational region. For beam properties, it was shown that the current density varies across the beam in the vertical direction. In preliminary cesium experiments, the expected increase of negative ion current and simultaneous decrease of co-extracted electrons were found, along with the influence of the control parameters (polarization of the plasma electrodes, magnetic filter field) on the SPIDER beam uniformity in the horizontal and vertical directions. It was shown that non-Gaussian tails can be identified in the angular distribution on the plane perpendicular to the beam propagation direction. Stray particles, nonhomogeneous beam and large divergence might result in unexpected heat and particle loads over ITER neutral beam injector (NBI) accelerator grids; it is the goal of SPIDER to assess and possibly to identify suitable methods for controlling these beam features. A major shutdown, planned for late 2021, to solve the issues identified during the operation and to carry out scheduled modifications, is outlined. Such improvements are expected to allow SPIDER to pursue the ITER requirements in terms of negative ion current, electron-to-ion ratio, and beam duration.

The design of an inspection system for the RFX first wall is reported. A crossed tracked vehicle is proposed to overcome the problem of possible overturning. The vehicle is equipped with a frontal TV camera and communicates with its off-board control, placed outside the vessel, by means of an umbilical cord which includes signal and power cables and can be used to recover the vehicle in case of failure. Since the inspection will be performed without venting the vessel, all components must be compatible with UHV condition. An insertion system made up of two telescopic elements and a rotating chute was also designed to introduce the vehicle into the vessel in safe conditions.