GNIRS Cold Motor Qualification

NOAO is planning to use internal (cryogenic) stepper motors to drive the GNIRS instrument cold mechanisms.

Motor qualification is in process and will entail the selection, preparation, testing, and usage of a stepper motor for the approximately 60 degree Kelvin vacuum environment of GNIRS.

Initial motor testing involves the usage of 2 alternative motors:

1) A commercial "cryogenic" motor, Phytron #VSS 42.200.1.2-E-UHVC-X.
    This motor is supplied by the vendor ready for cryogenic usage.
    The Phytron series of cryogenic motors is being specified by the IfA
    for their Gemini NIRI instrument, and also by UC-Irvine for a KECK
    mid-IR imager.

2) An "in-house" modified motor, API-Portescap #P530-258-004-10.
    Usage of this motor requires modification of the supplied motor bearings
    for cryo usage (removal of grease and application of dry lubrication).
    The Portescap series of motors has been successfully used in cryogenic
    applications by several other groups developing IR astronomical
    instruments (Ohio State Univ, U. Florida, CTIO, UCLA).

A final decision on cold motor usage should be achieved by June 1999, and will be based upon economic and technical considerations.  Initial testing of a modified Portescap motor in the NOAO cryogenic test chamber "CROC" was underway as of Mar. 25, and a Phytron cryogenic motor is on order.

Andy Rudeen      29 Mar 99

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