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Entry  Tue Nov 19 00:07:16 2013, Jenne, Update, LSC, Green status 
    Reply  Tue Nov 19 01:11:19 2013, Jenne, Update, LSC, Green status 
    Reply  Tue Nov 19 14:47:59 2013, manasa, Update, LSC, Green status 
       Reply  Tue Nov 19 17:47:17 2013, Jenne, Update, LSC, PRMI+2arms attempt 
Message ID: 9405     Entry time: Tue Nov 19 00:07:16 2013     Reply to this: 9407   9411
Author: Jenne 
Type: Update 
Category: LSC 
Subject: Green status 

After I aligned the IR interferometer (no ASS - we still need to figure out what's going on with that), I am trying to find the green beatnotes for each arm.

First, I locked the green lasers to each arm.

I then went out to the PSL table and aligned the Green Yarm path by overlapping the near-field and far-field of the yarm transmission and the PSL green pickoff.  I then turned on the power for the Beat PDs, since it was off (I confirmed that the outputs were plugged into the beatbox, so they are seeing 50 ohms).  I assume that the beat PDs were off since Manasa pulled the Beatbox last week, but there is no elog reference!!  Anyhow, after seeing a real signal, I maximized the DC power on the beat PD for the Yarm.  I then maximized the light on the DC transmission PD for the Yarm.

I looked at the Xarm, and the near-field alignment looks okay, but I haven't checked the far-field.

I started looking for the beatnotes from the control room:

I am changing the SLOW_SERVO2_OFFSETs by 30 counts, and then unlocking and relocking the arms, and checking to see if I see a peak on the RF spectrum analyser. 

The Y offset started at -10320, and I found a beatnote at -11230 (beatnote is about 26MHz).  The X offset started at 4500.  Going larger seemed to get me to a less bright TEM00 mode, so I switched and have been searching by going down in offset, but haven't yet found the beatnote.  I suspect that I actually need to align the X path on the PSL table.  The Y beatnote is very small, about -30dBm, so I also need to tweak the alignment by maximizing the peak value.

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