Design and technical requirements of the thermal shield for the system for the DTT facility

The Divertor Tokamak Test (DTT) facility, currently under construction at ENEA Frascati, includes a Thermal Shield System (THS) designed to protect the superconducting magnets from radiative heat loads coming from warmer surrounding components. The THS comprises three modular, helium-cooled sub-systems — the Vacuum Vessel Thermal Shield (VVTS), the Port Thermal Shield (PTS) and the Cryostat Thermal Shield (CTS) — all manufactured from AISI 316L stainless steel with restricted content of high-activation impurities (Co, Ta, Nb). VVTS and PTS adopt a single-shell, actively cooled 5 mm panel, while the CTS uses a single 3 mm cooled shell fitted with Multi-Layer Insulation (MLI) on the cryostat side. The cooling system relies on fully redundant, continuous seamless ¼" STD pipes, intermittently welded to the panels and operated with gaseous helium at 16 bar / 80 K (inlet); PTS 1–5 each have dedicated parallel paths, the VVTS follows a toroidal sector-based periodicity with its own dedicated manifold, and the CTS is fed by separate manifolds for its cylindrical body (3 sectors) and top lid (2 sectors) — all configured to maximize surface coverage. The THS is anchored to warm components (Vacuum Vessel, Ports, Cryostat) via gravity supports rated for plasma operation and baking up to 300 K, using G-10 epoxy for thermo- electrical insulation and slotted holes to accommodate thermal contraction. A full-scale VVTS prototype validates welding, distortion management, surface finishing and gravity-support performance under representative loads, de-risking series manufacturing ahead of the procurement campaign for VVTS, PTS and CTS.