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Entry  Fri Sep 12 00:40:23 2014, Jenne, Update, LSC, DRMI locking 
    Reply  Fri Sep 12 11:25:42 2014, Koji, Update, LSC, DRMI locking 
       Reply  Fri Sep 12 12:00:59 2014, ericq, Update, LSC, DRMI locking 
    Reply  Fri Sep 12 14:11:17 2014, ericq, Update, LSC, DRMI locking 7x
       Reply  Wed Sep 17 15:40:00 2014, ericq, Update, LSC, DRMI locking dcAngleDiff_srcL.pdfdrfpmiVertexSensing.zip
          Reply  Tue Sep 23 17:37:10 2014, ericq, Update, LSC, DRMI locking SRCcorrection.pdf
             Reply  Wed Sep 24 11:02:38 2014, manasa, Update, LSC, Moving SRM 
                Reply  Thu Sep 25 11:33:41 2014, Jenne, Update, LSC, POY alignment laser 
Message ID: 10527     Entry time: Tue Sep 23 17:37:10 2014     In reply to: 10514     Reply to this: 10531
Author: ericq 
Type: Update 
Category: LSC 
Subject: DRMI locking 

Rather than using a CAD drawing, I used Gabriele's code from ELOG 9590 to try and judge if we could shorten the SRC by the appropriate length, without clipping the SR3-SR2 beam. 

Specifically, I used these lines:

% Move SRM 7.5 towards SR2, parallel to beam


dAS = BS2-AS; Vector from SRM to SR2

dASmag = sqrt(dAS(1)^2+dAS(2)^2);

dMove = delta*dAS/dASmag;  delta times unit vector

CS = CS+dMove;

draw_sos(CS, 180/pi*angles)

to help generate this plot:



As a reminder, Gabriele's code used the following logic:

  • We know the nominal dimensions of all of the suspensions
  • We hand measured various distances between features of the suspension structures. (Corner to corner)
  • A global fit, minimizing the maximum error, reconstructed the positions of the suspensions. 
  • Beam positions assumed to be ideally aligned. 
  • Beam trajectories traced out, and optical path lengths estimated (taking into account changing indices of refraction due to flipped mirrors)

In my opinion, this is the best estimate of beam trajectory that we currently have.

Thus, from looking at the plot above, I claim we can correct the SRC length without clipping the beam by moving the SRM forward by the required 7.5cm.

Although the measured distance may be off on the order of a cm (since our PRC correction had a 0.5cm disagreement between interferometric and hand distance measurements), this will nevertheless markedly improve our 3F DRMI sensing, based on my previous ELOG. 


Hence, given our discussions last week, Jenne and I will proceed to ready the interferometer for venting in the morning, by following the vent checklist.

Our sole objective for this vent is this move of the SRM. 

Steve, please check the jam nuts, and begin the vent when you get in.  Thanks!

ELOG V3.1.3-