Feasibility study of graphite-based unidirectional diagnostic calorimeter

For optimizing the neutral beam injector which will heat the nuclear fusion experiment ITER, it is necessary measuring the beam properties with a high spatial definition. For this reason, the test facility SPIDER, which is under construction in Padova, aims to realize the transport of a negative ion current similar to the one that will be used in ITER. The diagnostic calorimeter STRIKE will be employed to study the beam properties produced in SPIDER, by focusing its attention in particular on the beam uniformity and divergence. Probably, the most important pending issue in STRIKE design is how to obtain a preferential way for heat transferring into the tiles. Various solutions have been tested, including the possibility to recreate the required thermal property with an appropriate mechanical manufacturing on a graphite tile. In particular experimental conditions, an unexpected phenomenon of optical aliasing has been noticed during the LASER tests of the graphite tile prototype. The proposal of this work is to study the opticalaliasing patterns occurring on the tile surface in diferent experimental conditions. Therefore, the attention will be focused in simulating the interaction between the thermal camera and the calorimeter. An IDL code has been developed to make possible the simulated reproduction of the patterns the thermal camera sees on the calorimeter, in all possible mutual positions of the two devices. After that, the images produced during the simulations will be compared with the real images obtained during the tests, to better comprehend the phenomenon which causes these optical aliasing patterns and to evaluate the possible consequences on STRIKE measures.