ART-XC/SRG: results of thermo-vacuum tests

ART-XC - a medium-x-ray-energy survey instrument for SRG project is being developed in Russia. Space Research institute (IKI) and Federal Nuclear Center (VNIIEF) has developed and tested the STM (Structural and Thermal Model) of ART-XC/SRG Instrument. The STM was tested in a 40 m(3) vacuum chamber, equipped with black cryogenic screens, cooled by liquid nitrogen. During the tests various thermal telescope modes were simulated. In particular we have simulated emergency mode, when mirrors heaters were switched-off. During the tests temperature of instrument's structure was controlled by 64 independent sensors. Stability of optical axis of mirror systems was also measured. STM test has shown that temperature of mirror system was lower than required, temperature of detectors met the requirements. The test also confirmed geometrical stability of the carbon fiber housing despite of significant temperature gradients. Additional experiments with two mirror systems, each containing a full set of simple nickel shells, were performed. In these experiments we have measured longitudinal and transverse temperature gradients of mirror systems. Next thermo-vacuum tests of the qualification model of the ART-XC instrument are being prepared. Results of STM tests are presented in this paper.