The GMTIFS beam steering mirror uses piezo-walk actuators and a combination of eddy current sensors and interferometric sensors to achieve this dynamic range and control. While the sensors are rated for cryogenic operation, the actuators are not. We report on the results of prototype testing of single actuators, with the sensors, on the bench and in a cryogenic environment. Specific failures of the system are explained and suspected reasons for them. A modified test jig is used to investigate the option of heating the actuator and we report the improved results. In addition to individual component testing, we built and tested a complete beam steering mirror assembly. Testing was conducted with a point source microscope, however controlling environmental conditions to less than 1 micron was challenging. The assembly testing investigated acquisition accuracy and if there was any un-sensed hysteresis in the system. Finally we present the revised beam steering mirror design based on the outcomes and lessons learnt from this prototyping.
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J. Davies, G. Bloxham, R. Boz, D. Bundy, B. Espeland, B. Fordham, J. Hart, N. Herrald, J. Nielsen, R. Sharp, A. Vaccarella, C. Vest, P. J. Young, "GMTIFS: the adaptive optics beam steering mirror for the GMT integral-field spectrograph," Proc. SPIE 9912, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II, 991217 (22 July 2016);