NAOJ GW Elog Logbook 3.2
I checked the alignment to the green AOM (FC first stage length control).
Initially the following signal was applied to the AOM: 109.036 035 615 MHz, 5 dBm signal generator amplitude + 18 dB RF amp, 24V 0.5A power supply to RF amplifier
I used the " BSN10 GR 90/10" (as it is labelled) to move the beam into the AOM, then kept going to align the first order diffracted beam into the iris (figure 1). The following power levels were measured:
Power from SHG: 270 mW
Power into AOM: 47.0 mW
Power after AOM (no signal): 46.0 mW
Power after iris (23 dBm signal): 22.0 mW
(c.f. reference levels 2764: 48.6 mW in, 24.3 mW out)
I took a few different measurements of the first order power for different RF signal amplitude - not really a comprehensive characterisation, just a quick check. Seems roughly consistent with old measurements (531 1679), but I wasn't trying to be too precise for now. I didn't rotate the AOM at all though.
22 dBm -> 18.6 mW (40%)
23 dBm -> 22.0 mW (47%)
24 dBm -> 26.0 mW (55%)
25 dBm -> 30.0 mW (67%)
26 dBm -> 33.2 mW (70%)
The green beam is roughly aligned close to the PR targets (figure 2). There shouldn't be too much adjustment needed, though it is a 2 person job.
Through the time I was in the cleanroom the SHG unlocked a few times, maybe once every 45 minutes or so.