On-ground calibration of the ART-XC/SRG instrument

The Astronomical Roentgen Telescope - X-ray Concentrator (ART-XC) is a medium X-ray instrument with operating energy range 4-30 keV which will be launched onboard the Spectrum Roentgen Gamma (SRG) mission. ART-XC consists of seven co-aligned mirror modules coupled with seven focal plane CdTe double-sided strip detectors. The mirror modules were fabricated and calibrated at the NASA Marshall Space Flight Center (MSFC). The Russian Space Research Institute (IKI) developed and tested the X-ray detectors. Flight mirror modules and detector units were integrated into the ART-XC instrument in 2016. For more detailed studies we have used the spare mirror module and spare detector unit. We present some results of the on-ground calibration of the ART-XC spare detector unit without a mirror system and estimation of the detector efficiency.