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Entry  Tue Jan 7 23:24:41 2014, Jenne, Update, General, IFO plan, list o' things to do 
    Reply  Wed Jan 8 13:46:39 2014, Jenne, Update, General, IFO plan, PRM baffle PRMcage_6Sept2012.JPG
    Reply  Wed Jan 8 17:53:26 2014, manasa, Update, General, IFO plan, IPANG telescope IPANG_layout.pngIPANG.png
       Reply  Thu Jan 9 17:21:45 2014, rana, Update, General, IFO plan, IPANG telescope 
    Reply  Thu Jan 9 10:34:58 2014, Steve, Update, PSL, PSL pointing changes in pitch Lfnfdnc.png24hPSLpointing.png
       Reply  Fri Jan 10 10:28:03 2014, Steve, Update, PSL, PSL pointing changes  clamped.png
Message ID: 9538     Entry time: Wed Jan 8 13:46:39 2014     In reply to: 9534
Author: Jenne 
Type: Update 
Category: General 
Subject: IFO plan, PRM baffle 


While we're in there, we need to also put a baffle on the back side of the PRM cage, to protect the OSEMs from stray light.  Den and I discovered before Christmas that turning off the OSEM and OpLev damping to the PRM (while using the POP QPD for ASC) significantly reduced the power fluctuations in the PRC.  We still had arm power fluctuations, but I believe those are likely because our ALS system can't hold an arm precisely at full resonance.  So, putting a black glass baffle with ~2 inch aperture right up against the OSEMs should help a lot.  This week, I'll ask Steve to make me a quickie to-scale cardboard version of the baffles that he has had cut, so I can try securing it to the dirty suspension cage that we have out.  I will also check to make sure I have seen with my own eyes the baffles that I need, and copper wire to tie it to the cage.

Steve may actually be onto something with the clamps that he had made a year and a half ago.  These clamps hold the glass, and then clamp to the base of the suspension cage.  Not the table, but the base of the suspension cage. The drawings are in elog 6344.  I'm not sure that the 1/4-20 holes in the clamp things are exactly where we'll want them, but we should be able to just dog it down to the base of the suspension.  I need to check this, but it may be even easier than tieing the glass to the cage.

Also, something to think about is that the earthquake stop screws extend backwards farther than the OSEMs.  I'm not sure anymore if we have shorter 1/4-20 earthquake stops around (if we do, they should be in the cleanroom shelves), but if we can't swap those out, they'll limit how close we can get to the OSEMs. 

Here's an overhead photo from 6 Sept 2012:


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