History: In alog 64353 we saw a beam high and right on the OFI_PD_A (B:PD:1). When in chamber we aligned this PD "via ndscope" alog60317 using a beam retro-reflected after B:M4.
Today (Camilla, Vicky): Starting at 19:07 UTC, we shuttered all SQZ beams and opened the beam diverter. IFO at 2W input locking at PREP_DC_READOUT with 4uW on PD_A (measure of 1% of s-pol light after OFI in HAM7), 140uW on PD_B (measure of s-pol light in HAM5 before OFI). In turn I adjusted ZM4,5,6 P and Y keeping all others at current "IFO aligned" values. OFI_PD_A didn't increase much, meaning with the current alignment the beam is on the PD, but not centered.
Attached are the values of ZMs that this PD started to clip at. During the alog 64353 photos (5th Aug), the ZMs were past these "starting to clip" values. So we expect the beam was clipped. Vicky verified this as the power on OFI_PD_A during photos was 3uWm, max we've seen is ~12uW.
See attached ndscope trend for when Robert took HAM7 IR photos ~8/5 PM when OFI_PD_A ~ 3uW, compared to OFI_PD_A ~ 12uW from 12 days ago (rightmost side of trend). AS_C_NSUM_OUT reports 0.6W into HAM6 at both times.
On Friday afternoon we attempted to take the HAM7 IR scattered light photos with different ZM alignments with the IFO in single bounce with 35W input power (alog 64716). This gave us 4uW on B:PD1( OFI_PD_A), a factor of 4 less light than we saw with IFO in full lock (12uW). Robert's 26th Aug ~5pm photos we saw none of the bright spots that we saw in alog 64353. Maybe the alignment of IFO light into HAM7 was different enough to not see the spots. We expect themto be visible with x4 power decrease. Plan to retake these images when the IFO is locked.
| 05/08 Photos taken (expect PD clipping) | 26/08 good OFI_PD_A alignment | |||
| PIT | YAW | PIT | YAW | |
| ZM4 | -408 | 376 | -188 | 177 |
| ZM5 | -548 | 640 | -384 | 432 |
| ZM6 | 662.3 | 923 | 732.3 | |
[Robert, Camilla, Vicky]
Late post of activity log from Robert's IR photos last Friday 8/26, ~5pm, for the record:
| 1345593754 | opened beam diverter, w/ifo in single bouce ~35W input |
| 1345594721 | zm4/5/6 set to "aligned" on ofi_pd_a (ie, clicked "set zm ifo") |
| 1345595155 | zm4/5/6 set to "misaligned/clipping" on ofi_pd_a |
| 1345595290 | set to "extremely misaligned", zm4 p/y = -600 / +550 |
| 1345595677 | set to "aligned" |
| 1345595704 | set to "intermediate clipping" in pit @ zm4p = -300 (down from -188) |
| 1345595760 | set to "aligned" |
| 1345595772 | set to "intermediate clipping" in yaw @ zm4y = 275 (up from 177) |
| 1345595925 | turned off vopo coil drivers |
| 1345595988 | set to "misaligned/clipping" |
| 1345596109 | set to "aligned" on ofi_pd_a |
| 1345596178 | turned on vopo coil drivers |
| 1345597045 | closed beam diverter |