SNS Tuner Motor Prototype/Production Issues E. Daly ILC Tuner FNAL 13OCT2014

Overview Developed prototype tuner with small lots from vendors Conducted Accelerated Life Testing of stepper motor & harmonic drive Ordered production components Found “stuck” tuners in production CM testing –Vendor changed internals of stepper motor

Tuner Assembly w/ Piezo Actuator Piezo Actuator in SST Cartridge (Model # PSt 1000/16/200 VS25) Flexure Connection to Cavity (2X) Flexure Connection to Helium Vessel (2X) Motor: Phytron VSS-52, 52 in*oz. Harmonic Drive: HDC ASP With 100:1 Reduction 316L Stainless Steel Frame Dicronited Beryllium Copper Drive Screw, M12 x 1.5

Accelerated Life Test: Tuner Assembly and Vacuum Tank

ALT Tuner Assembly: LVDT & Diodes Installed

History Purchased small quantity of Phytron VSS-52 stepper motors for Prototype & ALT –Installed 3 in first SNS MB prototype –Conducted ALT for 30 yrs equivalent life successfully Purchased large quantity for production –Installed in production MB CMs –Thermal cycled to 77K as acceptance test at JLab –After cooldown in CMTF of MB-01, tuners were “stuck” Evaluated production motors in VTA –Found that sticking occurred at 20K Upon disassembly, found internal difference between prototype and production motors –Vendor validated change with testing to 77 K  INSUFFICIENT! –Returned production quantity Replaced motors in CMs using access ports (~ 4 MB CMs)

Comparing SNS Tuner Motor Shafts: Prototype (left) and Production (right) The prototype motor has a series of wavy washers that are used to provide a pre-load on the shaft while allowing compliance during cooldown and operation at 4K. The production motor has a single wavy washer to the right of the bearing to provide this pre-load and compliance. The compliance is drastically reduce when compared with the prototype motor. Wave washers Single larger wave washer (not shown) Rotor from accelerated life test motor Rotor from M-01 Cav. #2 Tuner

Stepper Motor Inspection Summary M-01 Cav. #2 motor –History: Intermittent behavior in CM testing –Significant metallic particulate, iron(?) whiskers and other junk  given to Staff Materials Scientist for identification –Wear on shaft bearing race, destroyed bearing during disassembly Accelerated Life Test Motor (prototype shaft design – 6 to 7 small wave washers) –History: cycled for 30 yrs equiv. life –No particulate found –Noted differences between this motor shaft and M-01 #2 shaft (wave washer count & location) M-01 Cav. #1 motor (production shaft design – 1 large wave washer) –History: Failed in CM testing, sent to vendor for re-build, received at JLab, inspected, cycled and then inspected again –Upon initial receipt inspection from vendor, found four to six 1/16” metallic slivers –Cycled motor to 77K, ran for 1-1/2 hrs, and then re-inspected; similar number of slivers found Production Motor (production shaft design – 1 large wave washer) –History: Taken from inventory, no previous handling or tested at JLab –Found 1/16” metallic slivers similar M-01 Cav. #1 motor

Conclusions Plan for extensive testing on prototype tuner and components Include ALT for specific components Ensure production procurements are consistent with testing! Perform integrated system acceptance tests Provide access to maintain/repair components

Back Up

Materials in Motor Components Housing – stainless steel Stator assembly – copper, stainless steel, kapton Rotor assembly – Nickel plating, Al-Ni-Co (rare- earth magnet), stainless steel, other… Bearings – stainless steel, gold plating, Tungsten- disulfide coating on ball bearings, other… Wave washer – spring steel Hardware – stainless steel bolts, some type of loc- tite (?) on threads