Developing an infrared APD array camera for near-infrared wavefront sensing

We will be upgrading the MMT Observatory's (MMTO) Adaptive Optics (AO) system with a novel Pyramid Wavefront Sensor (PWFS). Our camera will utilize Leonardo's SAPHIRA, a low-read-noise electron Avalanche Photodiode (eAPD) array. By observing natural guide stars in the near-infrared, we will improve the sky coverage at the MMTO by an order of magnitude. We have developed a compact cryostat that utilizes Sunpower's CryoTel MT cryocooler to reduce the SAPHIRA's dark current and thermal background radiation. Our camera's cooling performance and cryocooler induced vibrations have been quantified and the results are presented here. Upon characterizing the laboratory performance of our camera at various reverse-bias voltages, this instrument will be integrated with MMTO's adaptive optics system. The successful implementation of this wavefront sensor will pave the way for future applications using this technology in AO systems of extremely large telescopes.