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Message ID: 10348     Entry time: Thu Aug 7 16:47:35 2014
Author: ericq 
Type: Update 
Category: SUS 
Subject: Oplev Checkup 

 I noticed some weird behavior on the ETMY oplev that led me to check them all out. 

The short of it is that the ETMY oplev has a pretty small angular range, compared to the displays and other oplevs. I measured how much angular motion each oplev can sense before the beam no longer hits all four quadrants (thus losing the ability to sense).  This could account for some of the additional angular motion of the mirrors... maybe. 

Also, some of the QPD quadrants had offsets as big as 400 counts, thus distorting the zero point. Anyways, here are the angular ranges of each QPD, assuming the current urad/cnt calibrations are valid. 

EMTY

  • P: +- 25urad
  • Y +- 30urad

ITMY

  • P:+-160urad
  • Y:+-172urad

 

BS

  • P:+-43urad
  • Y:+-40urad

 

ITMX

(Note: ITMX's oplev pitch and yaw is almost 30 degrees off of the alignment sliders' pitch/yaw coordinates. Steve tells me this is due to the tight nature of getting the oplev beam to the mirror without clipping.)

  • P:+-110urad
  • Y:+-80urad

 

ETMX

  • P:+-45urad
  • Y:+-85urad

 

PRM

  • P:+-50urad
  • Y:+-45urad

 

SRM

  • P:+-80urad
  • Y:+-80urad

I wrote a script to zero all of the QPD quadrants' offsets (it lives in /scripts/OL) and have used it successfully. The oplev laser must  be off before using it. 

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