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Entry  Fri Dec 12 04:33:49 2014, Jenne, Update, ASC, ASS retuned 
    Reply  Wed Dec 17 01:51:44 2014, rana, jenne, Update, ASC, ASS retuned ASSconfig_141217_0205.png
       Reply  Wed Dec 17 19:04:12 2014, jenne, Update, ASC, ASS retuned 
          Reply  Wed Dec 17 19:31:55 2014, Koji, Update, ASC, ASS retuned 
             Reply  Tue Jan 27 21:33:39 2015, Koji, Update, ASC, ASS retuned 
Message ID: 10807     Entry time: Wed Dec 17 01:51:44 2014     In reply to: 10789     Reply to this: 10812
Author: rana, jenne 
Type: Update 
Category: ASC 
Subject: ASS retuned 

Did a big reconfig to make the Y-arm work again since it was bad again.

  1. Undid Koji's topology change. The A2L loops now feedback to the arm mirrors to adjust the cavity axis. The cavity transmission signals now feedback to the input beam.
  2. The UGF of the Trans->Input beam servos is ~5-10x higher than the A2L servos.
  3. The Trans loops have a ~10-15 s settling time.
  4. The Input Matrix has been adjusted to fit with our intuition:The ETM tilt moves the beam equally on the ITM and ETM faces.
  5. The Output Matrix has also been adjusted to do like this: we're using an intuitive matrix inverse rather than one based on measurement. It turns out to be a reasonable guess and we can tune this later.
  6. Seems stable with many kinds of steps and misalignments. Seems not reliable if the arm power is less than ~0.5.
  7. Reducing the dither amplitudes to make the power fluctuation less than 5% made it much more stable.

With the arm aligned and the A2L signals all zeroed, we centered the beam on QPDY (after freezing the ASS outputs). I saw the beam going to the QPD on an IR card, along with a host of green spots. Seems bad to have green beams hitting the QPD alogn with the IR, so we are asking Steve to buy a bunch of the broad, dielectric, bandpass filters from Thorlabs (FL1064-10), so that we can also be immune to the EXIT sign. I wonder if its legal to make a baffle to block it on the bottom side?

P.S. Why is the Transmon QPD software different from the OL stuff? We should take the Kissel OL package and put it in place of our old OL junk as well as the Transmons.

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