Mechanical design of the bolometric and Soft-X ray diagnostics for DTT

Abstract In the European roadmap towards nuclear fusion, the new Italian project DTT (Divertor Tokamak Test), currently under construction at the ENEA Frascati Research Centre, aims at exploring alternative solutions for the divertor, in support to the optimization of the divertor configuration foreseen for DEMO. A dedicated set of diagnostics are planned to measure the total radiated power and to monitor plasma processes by means of Soft-X emission measurements. The total radiated power acquisition will rely on commercial metal resistor bolometers, while for the SXR range of energies a new technology based on custom Chemical Vapor Deposition diamonds (CVD) will be adopted. This work focuses on the mechanical layout design of these fundamental diagnostics, respecting geometrical and functional constrains of DTT and minimizing the diagnostics volume inside the access pipe. An integrated and compact solution, allowing flexible positioning and easy maintenance of the two systems has been identified, with a structural layout based on a modular approach. The detectors of the two diagnostics are installed on a common frame, with adjustable mounts for an independent fine-tuning of their alignment. The high heat load from the plasma is coped with by means of a custom active water-cooling system, to protect the sensors while ensuring stable and reliable operations. To allow a good physical exploitation of the collected data, i.e. with tomographic reconstructions, the lines of sight of both systems must be properly arranged on the poloidal section of the plasma. The proposed mechanical design foresees a customized chassis for each of the four poloidal ports of the DTT vacuum vessel, assuring a suitable coverage of the plasma's poloidal cross-section.