System level design of the Tangential visible and infrared viewing system for DTT

The Divertor Tokamak Test facility (DTT) is a superconducting tokamak under construction in Frascati (Italy). Its main goal is the study of strategies for the management of plasma exhaust in a reactor-grade tokamak plasmas, to support ITER operation and the design of DEMO. It will incorporate a visible and infrared viewing system dedicated to machine protection and plasma physics. This system, called Tangential Viewing System (TVS), consists of 6 Line-of-Sight (LoS) located in 3 sectors in equatorial ports. Each LoS provides a wide-angle view of 44 degrees x 60 degrees, with the first wall being the main area of surveillance. This paper details the work on TVS during its initial concept development, focusing on defining requirements, verifying preliminary performance, and developing potential design solutions. Each LoS is made of a Front Mirrors Unit collecting and transferring the light outside the vacuum vessel through a sapphire window. To optimize the performance in both channels, the visible and infrared beams are separated behind the window by a large dichroic. Then in each channel, an objective lenses creates a collimated beam which is propagated by an optical relay system up to the detector. In terms of the performance, the preliminary assessment of the spatial resolution and coverage is described. The spatial coverage of the outer and inner walls is evaluated to 97 % and 30 % respectively, which allows the first wall protection.