[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:
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:
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:
For convenience while vented, I made the following guardian changes so far:
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.