Sheila, Camilla, Madi and Rahul
This morning we went into HAM7 chamber and reduced the pre-load on ZM4 (PSAMS) to 65in-lbs (down from 75 in-lbs ). The pre-load on ZM4 was last adjusted in Feb 2024 (see LHO alog 75677).
This work was done as per the request of SQZ team, who wanted the pre-load on ZM4 to be reduced by 10in-lbs - see Sheila's comment on LHO alog 90919.
Given below are the steps we followed to reduce this pre-load on PSAMS,
After setting ZM4 into SAFE state (Camilla reduced the voltage on ZM4 an ZM5 PSAMS to ZERO and then I switched OFF the chassis) we locked all three stages of the suspension. We had already taken healthy TF measurements before starting our work.
- PSAMS (D1900092) cable was disconnected and carefully re-routed so that it stays away from the fixture plate.
- four add-on masses (basically 1/4-20 screws with washers) attached to PSAMS(D1900092) was then removed.
- bottom mass Fixture plate (D2100121) was attached to the structure using four 8-32 screws.
- PSAMS (D1900092) (already locked using EQ stops) was then further clamped using two 1/4-20 screws through the fixture plate. We had to adjust the height of PSAMS to the align the threads with the holes on the fixture plate.
- Once PSAMS was securely clamped, we removed the three set screws on the Mirror Pusher.
- Using a torque wrench (allen size 0.5inch - thanks to Mitchell for finding it), at first I slightly loosened (1/4 turn counter-clockwise) the Piezo Mirror Pusher (D1900123) and then set the pre-load to 65in-lb as requested by Sheila.
- We then followed all the above steps backwards (i.e set screws, add on mass put back, fixture plate removed, cable re-connected and the suspension set free).
- Once all done, we started damping the suspension and checked for any BOSEM flag changes - looks all good.
- We took all the tools out and put the curtains back on HAM7 chamber.
- Finally, I took the transfer function measurements and ZM4 is looking healthy like before - see L, P, Y dof.
Next, we will go into laser hazard with SQZ team and check for any changes in beam alignment and make adjustments as required.
