Purpose:
Newport's thermal drift testing of mirror mounts has two purposes: (1) to measure the maximum deflection during a peak temperature shift (after a soaking period) and (2) to measure the shift in position after temperature cycling and return to initial temperature.

Method:
A mirror mount, with mirror installed, was securely fixed to a 1.5"-diameter solid steel pedestal post. This assembly was then placed inside of a climate-controlled environmental chamber and mounted to a stainless steel optical table.  Upon fastening to the table, the mirror mount was set to nominal and zeroed to set the initial position. Throughout the test, an independently thermally isolated CONEX-LDS Autocollimator was used to monitor the reflected beam position. After initial alignment adjustments, the mirror mount was left to rest for two hours to allow the internal kinematic forces to reach equilibrium. Then, the mirror mount was subjected to a 10°C increase in temperature for one hour through convection heating. After a thermal soaking period to ensure the mount is sufficiently heated through, the mirror mount was returned to its original temperature, completing a cycle. This temperature cycling process was repeated 10 times over the duration of 62 hours, with deflection during peak temperature and shift after the end of each cycle recorded.