In-Vacuum Testing of LIGO Next-Generation Adaptive Optics

All optical hardware deployed within the Laser Interferometer Gravitational-Wave Observatory (LIGO) must undergo rigorous testing to ensure compatibility with the ultra-high vacuum (UHV) environment of the interferometer. This maintains a cleanliness standard that is critical to avoiding contamination that can cause sensitivity losses and, at most extreme, destroy the optical coatings of the high-power optics. We present a custom UHV system currently in use at the University of California, Riverside (UCR) to test newly developed adaptive optics for LIGO such as the FROnt Surface Type Irradiator (FROSTI). We focus on key aspects such as the UHV system's characteristics and specifications, the custom ISO Class 5 cleanroom that houses the entire system, and how they are utilized in crucial probing of the behavior of these novel wavefront actuators. Specifically, we highlight the tests performed on FROSTI confirming low outgassing rates, characterizing the thermal response of its internal heating elements, and demonstrating the device's capability to function properly as an effective LIGO component.