aLIGO LHO Logbook

H1 SQZ (DetChar)

camilla.compton@LIGO.ORG - posted 11:32, Thursday 27 July 2023 - last comment - 15:45, Thursday 27 July 2023(71761)

Increased OPO ISS setpoint from 50uW to 65uW.

Vicky, Camilla. Out of Observing today for squeezing optimization. No SQZ time 16:44UTC to 16:55UTC and 17:01UTC to 17:27UTC. See SQZ Troubleshooting Wiki for instructions.

Can see an increase in SQZ 350-1700Hz BLRMS comparing before and after this optimization.

NLG Increased:

As Austin had the ISS saturate with a 80uW set point and dropped it down to 50uW 71675 following 70050, I have increased opo_grTrans_setpoint_uW in sqzparams.py from 50 to 65uW at 16:45UTC. Hoping this is a sustainable level that we can stop changing. Readjusted TEC and accepted in sdf. As Corey states in 71613, we are aiming to not let H1:SQZ-OPO_ISS_CONTROLMON be set below 2.5 to 3V as that is close to 0V where the control loop bottoms out and unlocks. Can't lock with 75uW, 70uW = 1.8V, 65uW = 3W CONTROLMON.

The higher the setpoint, the higher the NLG and higher squeezing we get, see attached BLRMS, where lower is better.

Tagging DetChar - This NLG change may effect range. See change in H1:SQZ-OPO_TRANS_LF_OUTPUT and 71691 on how DARM changes with NLG.

AS42 SQZ offsets offloaded:

Followed instructions in 71083.

Take SQZ_MANAGER to "NO_SQUEEZING"
From sitemap > SQZ > SQZ ASC IFO > see screenshot circling buttons to click:
- First, purple button that says "! reset AS42 nosqz". Wait for script to run (it averages for ~30 sec). Log/post a screenshot of the output if you can. Close pop-up terminal when done.
- Next, purple button for "! graceful clear history". Close terminal when finished.

Attempted to increase SHG output H1:SQZ-SHG_GR_DC_POWERMON:

FIRST:

Aligned fiber polarization using pico waveplates on SQZT0, reduced H1:SQZ-SHG_FIBR_REJECTED_DC_POWERMON from 0.12 to 0.03mW with below procedure, see Vicky's attached screenshot.

Take SQZ_OPO_LR to "LOCKED_CLF_DUAL_NO_ISS" (ensure that SQZT0 screen AOM box is yellow)
Enable waveplate PICOs before fiber (L/2, L/4) -- (C_PICO_I_MOTOR_3_X/Y) (Pico settings {medium, walk} is fine. {small, walk} works if you are optimizing and very close)
SQZT0 medm > click "! fiber pol" to launch scope
Minimize SHG_FIBR_REJECTED green trace by using _X and _Y motors in turn until minium reached.

SECOND:

Tried to adjust SHG temperature via SQZT0 > SHG > H1:SQZ-SHG_TEC_SETTEMP, didn't make a difference so reverted.

THIRD:

Tried to adjust SHG beam pointing via mirror picos on SQZT0 > BEAM STEERING red triangles, didn't make a difference.

Vicky also checked the amount of lights throughput and suggests that we may need to go onto SQZT0 to and adjust the SHG aom pump alignment if we need more squeezing.

Images attached to this report

Comments related to this report

victoriaa.xu@LIGO.ORG - 14:21, Thursday 27 July 2023 (71771)

Link

Last time we re-aligned the pump aom due to clipping was in June, LHO:70198. In summary, I'd expect the power launched to the fiber, "H1:SQZ-SHG_REJECTED_DC_POWERMON", to be ~70% of the SHG output power, "H1:SQZ-SHG_GR_DC_POWERMON".

I added some scopes to the SQZT0 medm screen to make this easier to check, it is in:
--> $userapps/sqz/h1/Templates/ndscope/check_pump_aom_clipping.yaml
or from sitemap > SQZT0 > purple "! SQZT0 scopes" > "check pump aom" from the dropdown list.

From today's scope,
--> with all power going through the AOM (H1:SQZ-OPO_ISS_DRIVEPOINT = 0),
--> it looks like we're only getting ~22 mW out of the pump AOM (sum of bottom 2 traces)
--> when we should be getting 45.8*0.7 ~ 32mW, if the pump aom throughput was normal.

So, if we want to turn up squeeze levels, or if we start to get unstable at this sqz level, we could go into SQZT0 on a Tuesday to check the pump aom + fiber input alignments.

Images attached to this comment

victoriaa.xu@LIGO.ORG - 14:23, Thursday 27 July 2023 (71773)

Link

Also adding in a screenshot for how we "Aligned fiber polarization using pico waveplates on SQZT0..," circling the relevant parts of medm screens.

Images attached to this comment

victoriaa.xu@LIGO.ORG - 15:45, Thursday 27 July 2023 (71775)

Link

No-sqz times from this work, 1374512130-1374512500.