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Message ID: 1342     Entry time: Mon Mar 7 15:53:43 2011
Author: Alastair 
Type: Laser 
Category: GYRO 
Subject: Vacuum pumpdown part 2... 

I realigned the beam into the cavity using the last two steering mirrors.  I was able to get the signal on the transmission PD to come back to the level it was at before the pumpdown.  Having said that I think it is close to (or actually) saturating the PD, so we don't have a good measure of the change in transmitted power.  I measure 48mW transmitted with 108mW incident on the input mirror.

EDIT: I turned the beamsplitter at the output a bit to reduce the power incident on the PD, and added a beamdump for the reflected beam.  It's not saturating now (it has 20mW on it, whereas before it had 25mW) but it only a bit below this level.  I wasn't able to improve the alignment any further.  I wanted to try maximizing the transmission moving the lenses in our modematching, but one is at the max of the range on the translation stage, and the other isn't on a movable stage.  We should replace that and move the other one to the middle of the range so that we can optimize.

Attachment 1: pumpdown2.eps  16 kB  | Hide | Hide all
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