Large MCT FPA (≥ 2k2) are demanded to satisfy the current scientific needs to cover large portions of the sky in the range of near- and shortwave-infrared wavelength. The European Union has founded the ASTEROID project, a consortium of key research institutions and industrial partners to develop an European MCT FPA of 2k2 class in the state of the art of this technology. In order to validate the hybridization reliability of the resulting ASTEROID detector, several setups were developed at IFAE with capabilities to perform thermal cycles while the detector is capturing images. Since the detector prototypes were built with a special pixel configuration forming a "chessboard" with pixels at two levels, the damaged pixels by thermal stress were identified based on their position and signal level using machine vision algorithms. After 30 thermal cycles performed in the range from room temperature (293K) up to 50K, just few damaged pixels were found out before any thermal stress, thus likely damaged during the manufacturing process, being the number of damaged pixels by thermal stress negligible.
The ASTEROID project is a H2020-COMPET EU project whose main goal is to provide Europe with the capability to manufacture high performance infrared focal plane arrays (FPA) devoted to scientific and astronomical space and ground telescope missions. The european consortium is composed by key research institutions (CEA-Leti, CEA-Saclay and IFAE) and industrial partners (Lynred, EVG and ADDL) being the resulting detector a SWIR hybridized MCT (mercury-cadmium-telluride) FPA of 2k x 2k pixels and 15 μm of pixel pitch. The project also looks for the validation of a thermo-mechanical model for large FPAs by reducing the stress build up in the ROIC and wafer bonded structures, both resulting in better detector reliability. On this framework, a cryo-vacuum system has been developed at the IFAE mechanical workshop with capabilities to perform low temperature thermal cycles in the MCT detector range and up to ~50K. The large volume cryostat (~120 liters) is cooled by a helium compressor and a single stage cold head, hosting the detector and its preamplification stage to provide a suitable light path and radiation shield for thermal background control. Most of the inner light path parts has been developed using off-the-shelf optomechanical components which allow us to modify the incoming light performance with standard 1 or 2-inches optical components. The cryostat design, configuration and the whole system performance will be reported on this paper with the aim to test the hybridized FPA to assess the reliability at operating temperature after several thermal cycles..
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