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Reports until 12:35, Monday 26 September 2022
H1 ISC (SQZ)
sheila.dwyer@LIGO.ORG - posted 12:35, Monday 26 September 2022 - last comment - 11:21, Tuesday 05 September 2023(65110)
HAM6 aux laser removed, HAM7 beam checked: throughput good

Camilla and I removed the auxillary laser from HAM7 this morning, but left the irseses in place. 

Before removing the laser we noted that there was 0.25 NSUM counts on both OMC QPDs, with 21mW out of aux laser.  This is with the laser current at 150 mA, and the OMC QPD sums were similar to last week. 

We then switched to the squeezed beam from HAM7, using the OPO dither lock.  We temporariy turned the power into the seed fiber (which has no fiber switch right now) to 77mW, and measured 1.18mW  leaving HAM7 at the gate valve.  We measured 0.78mW arriving at HAM6 before OM1, which agrees well with SRM transmission of 34.34%.  We saw the SQZ beam on the OMC QPDs, 0.015 and 0.013 counts NSUM.  (This is a slightly higer ratio of NSUM counts to measured power incident on OM1 than for the aux laser.  Keita tell us this is not suprising since the aux laser beam size was large.  

We wrapped the breadboard that the aux laser was on in foil and brought it to the optics lab, and Camilla turned the seed power back down.

Comments related to this report
sheila.dwyer@LIGO.ORG - 11:21, Tuesday 05 September 2023 (72680)

The SRM transmission above was wrong, we have SRM06 which has a reflectivity of 32.34% according to E1700158 https://galaxy.ligo.caltech.edu/optics/

This means that our measurement above of 66% transmission from HAM7 to HAM6 indicates 97.6% transmission taking out the SRM transmission, which seems reasonable for two passes of the OFI with this kind of measurement accuracy. 

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