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Entry  Mon May 3 11:59:28 2010, Zach, Laser, GYRO, modifications 
    Reply  Mon May 3 12:19:52 2010, rana, Laser, GYRO, modifications 
Message ID: 746     Entry time: Mon May 3 11:59:28 2010     Reply to this: 747
Author: Zach 
Type: Laser 
Category: GYRO 
Subject: modifications 

 Pending a T measurement on the second 9-m Y1S mirror, we will be installing these in the place of the 6-m ones that are in the cavity right now. The reason is twofold:

  1. the T of the 6-m mirrors appears to be way off of what it should be, for one reason or another, and
  2. our final arrangement has always called for the 9-m mirrors, as they give us better HOM rejection and a lower optimum modulation frequency of fmod = 26 MHz (vs. the 33 MHz for the 6-m's).

The input waists for the cavity given these mirrors (the average, for spherical MM, and the two orthogonal waists, for cylindrical) are:

  • R = 9 m:                                  w0,avg =  928.6 µm
  • Rx = R cos 45° =   6.643 m:        w0x =  842.9 µm
  • Ry = R/cos 45° = 12.728 m:        w0y = 1019.7 µm

Since we will have to realign the cavity after replacing the mirrors anyway, we are going to slide everything down the table a pinch so that we can make room for the final MMT (the table is just too crowded for a proper IOO solution right now). After this, we will work out both a cheap (read: quick) modematch to the the average, and a full cylindrical modematch. The former will allow us to continue working on the experiment while we wait for parts for the latter to arrive.

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