aLIGO LHO Logbook

H1 SQZ

daniel.sigg@LIGO.ORG - posted 14:45, Tuesday 10 September 2019 - last comment - 10:07, Tuesday 01 October 2019(51856)

Replacing heliax cable, feethrough and SQZ AOM1

Kara Sheila Fil Daniel

Continuing replacing cabling for the CLF AOM1, old alog 51537.

We replaced the feedthrough and the helix cable to AOM1 of teh CLF. First, we saw the RF power monitor coming back to the old value of 33.5dBm. After a minute or so it went down to 5dBm. Most likely the RF amp blew. Unclear why, but after replacing it we carefully measured the RF power delivered to the AOM. We needed an additional 3dB attenuation to get back to the previous value of 34dBm, see alog 40071. Maybe the cable was defective and we got more power than the AOM could handle? Assuming the AOM potententially has a problem, we swapped it with the spare and reconnected. A lot of alignment tweaking was required to get back to the previous difraction power. All seems to be working again.

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daniel.sigg@LIGO.ORG - 16:07, Tuesday 10 September 2019 (51863)

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We also installed a 1064nm wavelength filter, Thorlabs FLH1064-8, in front of the CLF launch PD. This PD was very sensitive to the table lights. The filter transmission at 1064 should be >90%.

daniel.sigg@LIGO.ORG - 16:15, Tuesday 10 September 2019 (51865)

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CLF power level trend

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kara.merfeld@LIGO.ORG - 16:17, Tuesday 10 September 2019 (51866)

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We made the following measurements of the power on ISCT6:

After 1st periscope mirror: 3.32mW
Out of vacuum: 3.32mW
After 2nd periscope mirror: 3.25mW
Input to cube: 3.24mW
Output of Cube: 3.16mW
wrong polarization: .09mW
Front of Detector: 3.11mW

We made the follow power measurements on the Squeezer table:

OPO REFL: 3.06mW and 1.28v
Output monitor: 32.6dBm
Drive into AOM: 33.7dBm

daniel.sigg@LIGO.ORG - 10:07, Tuesday 01 October 2019 (52237)

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Yesterday, I tested, if the removed AOM still looks like a 50Ω load to make sure we didn't fry the input circuit. Indeed, it looked like a 150-250 MHz bandpass with proper 50Ω termination. However, I noticed that the SMA bulkhead thread of the AOM is tad bit too short. Out of 5 male SMA I tired 4 bottomed out, which potentially prevents a proper electric connection. This probably explains the flaky behaviour we observed.