Daniel Brown, Cheryl Vorvick, Haocun Yu, Terry McRae, Georgia Mansell
Summary: Today we started recovering the corner IFO after the vent. We worked on IMC/IO revival, alignment, and squeezer alignment. The IMC recovered well and we have reasonable transmission and reflection levels.
We are currently having a guardian/front end problem when locking PRMI - The ISC_DRMI guardian tries to turn on H1:LSC-MICH1_FM2 when it reaches the PRMI_LOCKED state. This filter module has a yellow "LC" flag above it on the MEDM screen (does this mean it is under local control?), and toggling the button or trying to set it in a guardian shell does not work. We're not sure how to get around this. First attachment is the guardian log when trying to toggle FM2.
While PRMI acquires easily we're having trouble locking DRMI (a familiar situation with short locks but nothing that holds well).
General vent recovery
- I transitioned the LVEA to laser hazard
- Turned on the HAM6 PZT HV and fast shutter HV
- Turned on the fast shutter chassis (in the rack next to isct6), and enabled its high voltage
- note HAM6 HEPI is locked, so we left its guardian paused, in the READY state, and the SEI_HAM6 guardian in ISI_DAMPED_HEPI_OFFLINE
- We've set the gate_valve_flag parameter in lscparams to True, so we can do DRMI without arms
IMC revival
- We locked the IMC at 2 W, it was clearly misaligned in yaw to start off with. We adjusted MC2 so we could lock on the 00 mode nad used the WFS to fix the alignment
- Note to self, to get the WFS going from a pretty rubbish first alignment we had to lower the trigger threshold (from 40 to 21), then increase the IMC WFS gain by hand from 0.04 to 0.4. We waited for the WFS to converge then offloaded them with the IMC_LOCK guardian.
- The reflected power of the IMC is at 8.3 mW [edit: this was a typo, it's at 0.083 mW with ~1.9W input power], reduced again after two-tuesdays-ago's mystery excursion.
- Cheryl ran the IMC-spot-position measuring script. She tried to restore the IMC mirrors to their positions back in August, using the witness sensors, but found this was not a good alignment. She later found a good alignment.
Corner station alignment
- We mostly got through initial alignment with the ALIGN_IFO guardian without too many problems, we couldn't do input align without the arms locked though
- We first did MICH_DARK and MICH_BRIGHT to check the contrast defect with the new TCS settings. Initially we measured ~1% contrast defect, however after we tweaked up the input alignment this was reduced to ~0.65%.
- To adjust the input alignment we went to the PRC_ALIGN state of ALIGN_IFO and adjusted IM4 and PR2 by hand to increase LSC_POP_A_LF. The input alignment might not be optimal yet.
Squeezer work
We repeated the squeezer single-bounce tests reported in alog 45375, with more seed power. We have ~20 counts on AS_A and AS_B when bouncing the seed beam off the SRM, compared with 8 counts 1 week ago. We still didn't have enough power to see the squeezer beam reflected off ITMX when SRM is misaligned. The second attachment shows the squeezer seed beam, as reflected off SRM, visible on the AS_AIR camera on ISCT6. Qualitatively, it does not look obviously astigmatic.
Daniel Brown, Thomas Vo, Georgia Mansell
- Today we locked DRMI-no-arms with a couple of different IFO alignments. The buildups we saw on POPAIR_B seemed quite reasonable. In PRMI_LOCKED we saw ~34 on RF18 and ~47 on RF90.* In DRMI_LOCKED we saw ~30-40 on RF18 and ~12 on RF90.
- We saw lower counts on RF18 with what looked like a more stable DRMI lock, and with a nicer beam on ASAIR. So we went to ISCT1 to check the alignment onto POPAIR_B. The alignment seemed fine. We note that the beam on AS AIR with DRMI locked looks pretty good which suggests our 50W TCS settings haven't messed things up too bad.
- TVo fixed our trigger mask problem which was preventing us from engaging the integrator (MICH1 FM3) with PRMI locked, as mention in the above alog. The DRMI_MICH_FMs threshold was too high for PRMI with no arms. We made a new lower set of thresholds in lscparams for DRMI with no arms.
- Dan and I plugged in and realigned the OSA on the AS port (on a pick off from the AS AIR camera path) to use as a diagnostic while tuning common/differential CO2 power. Dan will post an image of the scan currently.
- At the end of the evening we lost the PSL with what looks like another crystal chiller trip.
*actual channels I'm quoting are POPAIR_B_RF[18/90]_I_NORM_MON
Images of AS AIR on DRMI lock today with the current 50W pretunings.
We also began tuning CO2 differentially to see how the sideband build up on the OSA changes. The OSA scan attached is after the first step of 100mW change. Another 100mW change was applied but we lost DRMI and then the PSL went down.
