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Cryostat mechanism design and fabrication

The harsh operating environment of high vacuum and extremely low temperature poses several challenges to cryogenic mechanisms. These challenges include out-gassing, physical property change of metal and nonmetal materials, differential thermal shrinkage of different materials. Many motorized cryogenic mechanisms have been designed and fabricated for various IR instruments at the Institute for Astronomy. These mechanisms include detector focus stages, filter wheels, 2 and 3-position bema selectors, lens switchers, grating tilt stages and gimbal mirror mounts. Cryogenic motors are used for all these mechanisms. The following topics will be discussed in this paper: motor selection, material selection, stress relieve and surface treatment, ball bearing and ball screw selection and treatment, bushing materials, lubrication methods, flex pivots, and Hall effect sensors.