40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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Message ID: 1095     Entry time: Mon Oct 27 14:48:27 2008
Author: Yoichi 
Type: Configuration 
Category: PSL 
Subject: EO shutter installed to the reference cavity 
I'm now preparing for cavity ring down measurements of the reference cavity.
An EOM for polarization rotation is installed between the two steering mirrors for the reference cavity.
The location is before the polarized beam splitter (used to pick-up the reflected light from the cavity) and
after the half-wave plate. So we should be able to use the PBS as a polarizer.
While setting up the high voltage pulse generator, I realized that we don't have enough cables for it.
It uses special kind of connectors (Kings 1065-N) for HV connections. We need three of those but I could find
only two. I asked Bob to order a new connector.

For the moment, the EOM is left in the beam path of the reference cavity until the connectors arrive (Wed. or Thu. this week)
and the measurements are done.
The EOM distorts the beam and degrades the mode matching to the reference cavity.
I optimized the alignment of the crystal so that the RC transmission is maximum.
Even though, the transmission of the reference cavity is down from 2.8 (without EOM) to 1.7 (with EOM).
I increased the common gain of the FSS from 7dB to 10dB to compensate for this.
The mode clearner locks with this configuration.

If the EOM is really disturbing, one can just take it out.
Since I did not touch the steering mirrors, the alignment to the reference cavity should be recovered immediately.
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