Naoki, Vicky, Camilla
At the end of maintainance:
- Tried to restart the SHG TRANS camera by unplugging and re-plugging, no success.
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Moved the temporary SQZ-SPARE_A_DC PD from BPS1 transmission (alog 68632) to the reflected beam of the isolator (not on the D1201210 layout but between MR22 ans DS2). Photo attached, we dumped the reflection. This should allow us to monitor the SHG power drift. Updated Pd calibration and accepted in sdf.
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Attached SHG scan at gps time 1368317210 + 800 seconds (4 x 200 second ramps).
- Top to bottom: SHG PZT, SHG TRANS, SHG REFL, SHG GREEN OUTPUT
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- Increased power into the SHG usign HW9 half wave plate. Started with 220mw before isolator, 200mW after isolator and green SHG 40mW output, turned it up to 255mw before isolator, 235mW after isolator and green SHG 48mW output (may change with thermalization). We expect this will allow us to increase NLG from the current value ~4.
Some interesting trends to see what SHG output is sensitive to, knowing that SQZT0 hasn't fully theramlized yet after just 30 minutes of closing up. So far, I tried things with marginal gains like pico-ing the input IR alignment (marginal gain), tweaking SHG CMB servo gain (marginal, but bad if too high > -9), SHG TEC temperature (marginal gain, original setting was pretty close), as well as things which surpringly had an effect like changing the SHG common servo offset. We can get to higher NLGs now, and will work on this soon, in coordination with PEM work.
In addition, the opo pump aom's diffraction efficiency is still reasonbly good, see trends from varying the pump power. With no diffraction, there's about 21mW through the AOM 0-order (which goes to the OPO). With full diffraction drive, there's ~8mW in the 0-order which is dumped. This is like (21-8)/21 ~ 62% diffraction efficiency of the pump aom, so PUMP ISS should have sufficient range.
