We have completely lost our beam into the 3 km Michelson because of the vacuum works around MCF to PRM chambers.
Now the beam spot on PR2 (2 inch mirror) is at the edge (attached).
This means that the input beam into PR2 is roughly shifted by ~1 mrad.
The beam from PSL and the IMC transmitted beam also shifted by ~25 urad.
What happened?
15:26 (JST) When we (Nakano, Enomoto, Nagano, Hasegawa) were aligning PR3 and ETMX to get the beam back and forth to REFL PD, we suddenly lost our beam.
- lost the beam into EX2 camera and REFL PD at the same time
- but Kimura-san confirmed that the GV close to IXA is still opened
- IMC transmitted power and the beam spot on IMMT1 transmission QPD didn't changed
- PR3 was working fine
-> IMMT1, IMMT2, or/and PR2 should be the ones who were tilted
We were not sure what happened at this point, and tried to align PR3 again, but could only see slight amount of light at EX2.
16:32 (JST) IMC transmitted power K1:IMC-MCL_TRANS_OUT dropped to 0.25 (was 0.42) suddenly.
- the beam spot on IMMT1 transmission QPD was jumped by 1.4 mm in yaw
- DC alignment of IMC mirrors using oplevs were on, and the OLDAMP outputs for MCi and MCo jumped very much (MCe was OK)
-> MCi, MCo, MCi oplev, or/and MCo oplev was shifted
- Kokeyama-san found the beam spot on PR2 was completely mis-centered; the beam was at the very edge
At this time, Tomaru et al. were working on tightening some bolts for MCE to PRM chambers. We stopped them to work on MCF next.
16:59 (JST) IMC EOM alignment was done by Nakano-kun
- this was done to restore the EOM alignment (see klog #1362)
-> PSL output beam (IMC input beam) could be slightly shifted
Investigation on 16:32 IMC incident
1. We (Aso, Enomoto, Michimura) tried to restore the IMC alignment by making MCi and MCo coil outputs to be the same values before the incident, but this gave worse IMC alignment. So we concluded that MCi and MCo (both in MCE chambers) mirrors are tilted. Their oplevs could be shifted also.
2. We (Nakano, Michimura) aligned IMC using picomotors and coils to maximize the IMC transmission. We could restore the transmitted power, but the beam spot on IMMT1 transmission QPD was shifted by -67 um in pitch, +360 um in yaw. This means that the PSL output beam was shifted by roughly 25 urad.
3. Below is the summary of channel values around 16:32 IMC incident. MCi was the one tilted very much, and the tilt was 17.7 urad in yaw.
before incident after incident after IMC restoration
K1:VIS-MCI_TM_OPLEV_PIT_OUT -0.7 urad 1.5 urad
K1:VIS-MCI_TM_OPLEV_YAW_OUT 6.9 urad 24.6 urad
K1:VIS-MCO_TM_OPLEV_PIT_OUT -9.7 urad -9.3 urad
K1:VIS-MCO_TM_OPLEV_YAW_OUT 1.5 urad 2.0 urad
K1:VIS-MCE_TM_OPLEV_PIT_OUT 0.8 urad
K1:VIS-MCE_TM_OPLEV_YAW_OUT -2.9 urad
K1:LSC-IMT_QPDA1_SEG1_INMON -29200 -20300 -31600
K1:LSC-IMT_QPDA1_SEG2_INMON -16700 -630 -12300
K1:LSC-IMT_QPDA1_SEG3_INMON -3660 -180 -3040
K1:LSC-IMT_QPDA1_SEG4_INMON -7570 -5000 -8960
beam spot on IMMT1T QPD in P -1150 um -1140 um -1080 um
beam spot on IMMT1T QPD in Y 630 um 2060 um 990 um
MCI OLDAMP P 1940 21500 OLDAMP turned off
MCI OLDAMP Y -400 -10200 OLDAMP turned off
MCO OLDAMP P 10400 5340 OLDAMP turned off
MCO OLDAMP Y -450 8190 OLDAMP turned off
MCE OLDAMP P -300 -300 OLDAMP turned off
MCE OLDAMP Y -1730 -1730 OLDAMP turned off
Note that calibrated signal from IMMT1 transmission QPD was not recorded properly because matrices and gains were reset, but I calibrated manually using SEG1,2,3,4 signals and Enomoto's calibration (klog #912).
Investigation on 15:36 IMM-PR2 incident
1. After the IMC restoration, the beam spot on PR2 was still at the edge (attached). PR2 is a 2-inch mirror and IMMT1 to PR2 length is 23 m, IMMT2 to PR2 length is 20 m. This means that the input beam into PR2 is roughly ~1 mrad shifted. This cannot be explained by PSL output beam ~25 urad shift.
2. Since Tomaru-san calims he was not working on PR2 chamber, IMMT1 in IMM chamber or/and IMMT2 in IFI chamber are the suspicious ones (needs confirmation tomorrow).
What to do tomorrow
1. make PR2 camera show brightness center
2. check beam at IMMT1T QPD
3. make snapshots for IMMT1T QPD settings
4. open IMM and IFI chambers to see the beam spot on IMMT1 and IMMT2
5. align IMMT1 and/or IMMT2 to center the beam on PR2 (and IMMT2), using PR2 camera
6. check beam at BS
7. sweep PR3 and wait for the beam to reach EX2 camera
8. if no success, use both IMMT2 and PR3 for the sweep
