[Julian, Naoki, Camilla, Sheila, Vicky]
Summary to get SQZ alignment beam: Launched 76mW into seed fiber, ~25 mW incident on opo cavity, ~0.85 mW transmitted through opo cavity. Had to find opo transmission past the VIP, for this we used green SK path as a reference. This ~0.85 mW opo transmission was bright on an IR card at the HAM5 gate valve, and enough to iris the SQZ beam in HAM7 and HAM6 (for OMC work 75512). DC 3/4 centering loops engaged easily, then OMC A/B QPD's saw the sqz beam.
----------- Notes from today ------------------------------------------
Launched power into SEED fiber (SQZT0): 76 mW
OPO IR REFL (CLF_TRIG_REFL_DC_POWERMON @ SQZT7): 24.8mW (when opo is dither-locked).
Fiber rejected power PD in HAM7 (CLF_REFL_REJ) is 5.3 mW.
--> Seed fiber coupling: ~34% of the seed fiber launched power was incident on the opo cavity.
--> 40% coupling through fiber, ~6% mispolarized and rejected after fiber. This is similar to recent fiber alignment 75344, even after more recent on-table work 75486.
We had to find the OPO IR transmitted beam after the VIP. Nothing at first despite restoring suspensions 75502. Notes to self on what worked to find the SQZ beam post-vent:
- Started with no opo trans after the VIP, despite checking SQZT7 periscopes and the HAM7 RLF QPD's (which we use for FC WFS).
- 75502 saw ZMs had shifted after vent. Naoki 1) offloaded all FC+SQZ ASC and set all PSAMS offsets back to "nominal", then 2) he and Austin restored ZM1-6 + FC1 slider values to the same P/Y damp values as we last had in observe. Still did not see beam past the VIP (nothing on RLF QPD's, nothing on SQZT7 IR camera).
- SK path was helpful to find the VIP transmitted beam.
- Looking at the bottom SK periscope mirror on SQZT7 like here, we walked FC1 P/Y sliders to overlap FC_GR_REFL (which sees FC REFL), with OPO_REFL (which does not see FC REFL, and thus is a good alignment reference for the FC REFL path including ZM1-2-3-FC1).
- Used FC1 P/Y sliders to overlap FC_GR_REFL with OPO_REFL (looking at an IR card on the periscope lower mirror). While doing this, we found OPO IR TRANS on the RLF QPD's.
- Then we walked FC1 and ZM3 to maximize transmitted power, ie OPO_IR_DC_POWERMON. Not totally optimized, but seemed reasonable to keep going.
OPO IR TRANS (OPO_IR_PD_DC_POWERMON @ SQZT7): 0.85 mW -- Just before opening the HAM7/5 gate valves. Opened the beam diverter, SQZ beam was bright on an IR card held at the HAM5 gate valve.
After opening gate valve, immediately saw the beam on AS A/B/C QPDs.
ASC-AS_A/B_DC_SUM_OUTPUT ~ 60. ASC-AS_C_NSUM_OUT16 ~ 0.65-0.67.
HAM6 crew irising SQZ beam, 75512.
HAM7 crew irising SQZ beam. Julian has some photos of HAM6 and HAM7 irses. Sheila -- looks like there is some clipping on the VIP (we have not totally optimized FC_REFL path slider alignments post-vent, just found the beam). Revisit this FC REFL alignment later.
Engaged DC 3/4 centering. It just worked. Control signals near 0.
We see the beam on the OMC QPD's, power is consistent with ASC-AS_C power, around 300-400e-6 on each OMC QPD A/B. Power goes away when SQZ beam diverter is closed. See omc powers screenshot with as_wfs powers.
TO-DO SQZ work later:
- more photos of HAM7 irises
- measure sqz beam powers with power meter
- undo VIP clipping (using e.g. FC1/ZM3) - we didn't fully optimize this FC REFL alignment yet after venting.
tagging for EPO
Accepted ZM1,2,3,4,5,6, FC1,2 OPTICALIGN sliders in sdf. Attached is the photo so we'll know where to bring them back to after pumpdown.
ZM4,5,6 are not monitored - should remember why that is....
Camilla, Naoki, Vicky
Next day 1/23, we tried to help check OMC alignment, but after turning the SQZ laser back on, we didn't find the beam past the VIP at first.
To re-find the sqz beam, we had to move FC1 quite a bit (pitch slider by 100 counts, yaw slider by 65 counts). See FC1 SDF's of today's move, compared to what Camilla just accepted in SDF after we first found the beam yesterday 75517.
Naoki checked FC1 and ZM1-2-3-4-5-6 SUS, and did not see any anomolous movements of the optics.
We left FC1 with an alignment that maximizes signal on both HAM7 FC WFS (RLF QPD's). Both QPD's are now saturated with 75mW into the fiber. With 5mW into the fiber to un-saturate, both QPD's are close-ish to centered.
Hopefully this is enough to use AS A/B WFS centering tomorrow. Today when we tried it, DC3 worked, but DC4 railed as the beam wasn't hitting AS_B well.
Sheila, Camilla, Vicky
We re-found the SQZ beam in HAM6 this morning after opening the ham5 gate valve. Steps taken this morning 1/24, after yesterday using FC1 to align onto the HAM7 FC WFS QPD's:
- With TTFSS locked, 75mW launched into seed fiber, brought SQZ_MANAGER to LOCKED_SEED_DITHER
- Watch using opo-ir-dither-locking scope to make sure OPO dither locked properly on red. Can check OPO IR REFL locks at its aminimum (see H1:SQZ-CLF_TRIG_DC_POWERMON, or SHUTTER_I_TRIGGER on the opo-ir-dither scope, successful dither lock example here).
- Check there is power on the HAM7 FC WFS QPD's. When aligned to OMC, we've been saturating RLF_QPD_A, and ~40-70 on RLF_QPD_B.
- Open HAM7 SQZ beam diverter
- Open HAM6 Fast shutter
- (check AS WFS DC centering is off, check that suspension histories on OM1,2 are clear)
- Use ZM5 P/Y to align onto AS_C, AS_A, AS_B
- If beam is hitting AS_A/B, the AS_WFS_P/Y_INMON input signals should all be < 1. When the beam was missing AS_A/B, their WFS_P/Y_INMON signals were ~1e6. Once the beam start to hit QPD's, INMONs were < 1.
- With SQZ beam launching 75mW, except SQZT7 OPO_IR_PD ~1mW. Then open gate valve -- expect AS_C ~ 600e-6, AS_A/B ~ 60-70. Screenshot of powers after refinding SQZ beam on AS WFS.
- With the beam hitting AS_WFS, turn on inputs for DC3/4 WFS centering, control signals ~ 0.
For convenience while vented, I made the following guardian changes so far:
- SQZ_MANAGER -- these changes can be reverted post-break
- "LOCKED_SEED_DITHER" is now requestable from drop-down menu -- Line 597 -- change back later
- "DOWN" no longer closes squeezer beam diverter -- commented out Line 213 -- change back / re-evaluate later
- SQZ_OPO_LR: trying to improve dither lock's lockless detection -- keep these changes
All guardian edits (+sqz angle servo flag in sqzparams.py) commited to svn revision 27088.
Attached Julian's photos of the iris locations on HAM6 and HAM7.
