Lock acquisition

• After the input alignment changes this morning we had trouble with DRMI ASC
  • We updated the offsets in the POP QPD which is used for PRC1 ASC (DRMI only, in full lock we use the dither alignment). See first attached screenshot.
  • For this lock we aligned PRM by hand, we haven't tried reacquiring with the new POP offsets.
• For our afternoon lock (~1334706032 - 1334713369) we powered up on RF with no annular CO2X. We powered up on RF partly because we wanted to do OMC scans, and partly because the IY mode6 violin was so badly rung up DC readout was impossible. We turned off CO2 X by hand because we wanted to get a fresh ITMX absorption measurement with the HWS.

CO2 Y improves POPAIR RF18 and sideband imbalance at AS port

• We turned on CO2 Y central heating in lock to see if we could see the effect on the OMC scans following Gabriele's suggestion
• Craig took a reference OMC scan, and other scan with CO2Y on, an interactive plot is here
  • Blue is with the CO2 lasers off, Red is with CO2Y on at 1W (though not fully thermalized)
  • The +9MHz 20 mode went from 52mA (no CO2Y) to 1.61mA (1W CO2Y) - this is a great success!
• 1W of CO2 Y was a little bit too much (second attachment), we eventually had an ASC-esque lockloss. I'd suggest if we want to set the CO2 laser again we should try for ~0.8W
  • Note I'm quoting measured powers here, the rotation stage needs recalibrating and the requested power was a bit off

ITMY mode6

• Since we were on RF darm the sensor in our violin mode loop is different to yesterday. I tried many settings for ITMX mode6
  • First I switched the actuation from Yaw to Pitch
  • I tried FM1/FM2/FM10 (-60 degrees phase) with increasingly negative, I also tried setting the phase to 0. None of this yielded anything good.
  • I tried switching the actuation of Length with FM1/FM2/FM10 and -0.1 gain. This also did nothing
  • I don't know if we have to drive harder, or use a broader filter. Nothing I did seemed to have any effect (third attachment).

Notes for the next commissioners:

We have left the ifo in down to get a nice cooldown curve for ITMX. The POWER_UP_ON_RF flag in lscparams is still TRUE, if future commissioners want to go to DC readout this will need to be updated.