Thermal simulations for characterization of ATHENA mirror modules with a radiating box in the BEaTriX facility

Abstract

The BEaTriX facility is currently in the realization phase at INAF - Osservatorio Astronomico di Brera in Merate (Italy) and it will be used as demonstrator for the acceptance test (PSF and Aeff) of the ATHENA Mirror Modules (MMs), with a rate of 3 MMs/day. The BEaTriX facility is a compact X-ray test facility (13m x 6 m x 2m) working in low vacuum at the energies of 1.5 keV and 4.5 keV. The testing optic is placed into a small chamber (MM chamber), that allows a fast MMs replacing time. All the MMs will be tested at room temperature (20°C), but the possibility of X-ray characterization at different temperature (-10°C / +50°C) is also foreseen. For this task a modular thermal box is designed and will be installed inside the MM chamber. The thermal box radiatively heats or cools the MM, by means of heat pipes that transfer the desired heat from dedicated chillers. It is designed to be able to impose a uniform temperature across the MM or impose also some gradient in order to characterize the optical performance of the MM in different thermal condition. In this paper, we present simulations of the temperature distribution at the MM level, as function of the thermal box design, which has been optimized considering the space envelope and result of the FEM simulations.