Development of a large aperture testing capability at Orion

Development of the Large Aperture Damage System (LADS) within the Orion laser facility provides a new capability for operational damage testing. LADS uses the 1053 nm, nanosecond output (≤ 10 ns) of a single beamline reduced in aperture to approximately 80 mm, at a fluence of up to 25 J/cm², providing system-relevant performance. LADS provides an operational understanding rather than exact LIDT thresholds, with the intention of reducing system risk, improving efficiency and lowering future costs. LADS uses a 25.5 m focal length mirror, propagated 17m, to reduce the 290 mm beam to ~80 mm (depending on the position of the test optic). LADS can be configured for either HR or AR optics, with a spatial profile similar to that of the main laser system. The early tests on LADS have focused on providing data for reduced specification optics, with a modest LIDT requirement of 5 J/cm² and several microns of reflected wavefront error. The results indicate satisfactory performance for polyurethane polished optics, enabling confidence in quicker production. The polyurethane optics showed better performance when evaluated on LADS than that expected from sample testing thresholds, highlighting the difficulties in testing and operational performance. Some initial work has also been done on infrastructure-related contamination issues and their impact on in-service optics, beginning with investigating the difference in LIDT of different contamination scenarios. The successes of the LADS platform have delivered a new capability in Orion, and the design is complete to deliver a 3rd harmonic (351nm) capability.