Back to observing at 2057UTC.

Maintenance recovery was slowed by ITMY CPS glitching (alog72683) that Jim fixed by replacing a CPS card. This was also the cause of some lock losses last night.

Jim kindly agreed to sweep the LVEA and didn't notice anything amiss.

J. Kissel, J. Warner

More details to come, but after trending around this morning, Jim found that Ryan's issues with lock losses last night were coincident with H1:ISI-ITMY_ST1 and ST2 capacitive position sensor (CPS) glitching as loud as ~4 micron jumps in 65-100 Hz band limited RMS.

Attached are trends of the new-ish band-limited RMS channels installed in April 2023 (see CPS BLRMS ECR installation mentioned in LHO aLOG 68798, and design in SEI aLOGs 1849 and 1867) compared against the ISC_LOCK_STATE_N, where 600 in NOMINAL_LOW_NOISE.

The 2nd row of both plots show the ST1 and ST2, H2 and V2 CPS BLRMS trends for both the 65-100 and 130-200 Hz bands. One can see the loudest of glitching in these sensors, where the y-axis is in nano meters.

These 4 sensors are all in the corner two "rack," but each sensor has its own readout card. 

The loud glitches correspond to times of ITMY watchdog trips too, which is what Ryan saw in LHO aLOGs 72671 and 72666.

Jim is swapping out some of the cards as I type, and will aLOG accordingly.

TLDR - Looks llike it was a race condition between during a lock loss and a timer never getting reset. Put in some code to hopefully get around this.

Recently we've seen IFO_NOTIFY alerting as soon as we get to the state NOMINAL_LOW_NOISE on a few locks, rather than waiting for the camera servo timer or the nln timer. Ryan S and I took a look at it last week and didn't find the issue, but left some more log messages to help us debug. These messages showed that the timer for nln was getting reset at a lockloss. The only way for this to happen is if during a lock loss the IFO node went out of its Observing state before ISC_LOCK went out of NOMINAL_LOW_NOISE. This happened twice last night because of the ITMY ST2 trips (alog72666), but looking at slow channels for other times make it difficult to confirm.

I added a reset for the timer to some absurdly large number when ISC_LOCK is in DOWN. This should stop this past situation and let us use IFO_NOTIFY during commissioning times if we wanted. I loaded it into the node, hopefully this is the fix.

Maintenance almost wrapped up, starting to relock now.

Tue Sep 05 10:07:08 2023 INFO: Fill completed in 7min 4secs

Looking over the PSL this morning, I noticed the RefCav TPD dropped from ~0.86V to ~0.8V over the Labor Day weekend (see attachment).  Checked with the on-duty Operator to ensure no one was using the IMC (no one was), so we took it to offline and I remotely tweaked the beam alignment into the RefCav to attempt to recover some of the lost TPD signal.  I was able to get the TPD up to ~0.885V with the IMC unlocked (~0.86V with the IMC locked, unsure why the difference).  Will keep an eye on this, looks like we may need a PSL enclosure incursion sometime in the next couple weeks to adjust the FSS path alignment on table.

WP11409

A new h1hpiham1 model was installed on h1seih16, no DAQ restart was needed.

TITLE: 09/05 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Preventive Maintenance
OUTGOING OPERATOR: Ryan C
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 3mph Gusts, 1mph 5min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.13 μm/s
QUICK SUMMARY: PEM injections and SUS charge are finishing up, IFO locked for 45min. Maintenance about to start

The ITMY ISI watchdog tripped, hasn't shown up on H1locklosses yet.

ITMY stage2 watchdog tripped and killed the lock, not sure why it tripped. Its the second time in a row that it's happened.

Vicky and I went to SQZT7 while calibration work was happening, to follow up on some of our observations from 72525 (and Vicky's comment). 

Polarization issue:

​​​​​​​With the seed dither locked, we placed a PBS before the half wave plate in the homodyne sqz path and measured 67.2uW transmitted (vertical pol) and 750uW reflected (horizontal) (817uW total, 8% in the wrong polarization, 16.5 degrees polarization rotation).  After the half wave plate we measured 5.48uW transmission through the PBS (vertical) and 802uW reflected (horizontal) ( 807uW total, 0.7% in the wrong polarization, polarization less than 5 degrees away from horizontal).  We also placed the PBS right at the bottom of the periscope, and there measured 70uW transmitted and 820uW before the PBS was inserted (8.5% in the wrong polarization, 17 degrees polarization rotation away from horizontal).  This would not limit the squeezing measured on the homodyne since we are able to correct it with the HWP, but measuring the same polarization rotation at the bottom of the periscope suggests that the beam could be coming out of HAM7 with this polarization error, which would look like an 8% loss to the squeezing level in the IFO. 

In Sept 2022, during the vent for the OM2 swap, we measured the throughput of the seed beam from HAM7 to HAM6 65110, which agreed well with the only loss between HAM7 and HAM6 being the 65.6% reflectivity of SRM, and suggests that there was not an 8% loss in the OFI at that time. 

Loss on SQZT7 (not bad):

Comparing the total power measurements here, we have 820uW at the bottom of the periscope, and 807uW measured right before the homodyne, so we have something like 1.6% loss on SQZT7 optics (small compared to the type of loss we need to explain our squeezing level).  

Seed transmitted power over reflected power ratio has dropped:

We also measured the seed power reflected from the OPO, so that we could compare the ratio of transmitted to reflected seed measured at the time of the squeezer installation in HAM7 in Feb 2022: 61904 (3.9% trans/refl). Today we saw 0.82mW seed transmitted, and 27mW of reflected seed at the bottom of the periscopes (3.03% trans/refl).  This is 78% of the ratio measured at installation.  Because this seems like a large drop, we repeated the measurement twice more, and got 3% each time.  We also checked that the dither lock is locking at the maximum seed transmission.  

Homodyne PD QE check (QE of PDB might be low):

We used an Ophir which was calibrated in 2018 to measure the LO power onto the homodyne PDs, the filter and head are SN 889882 and the controller is SN 889428.  For PDA we saw 0.6mW, for PDB we saw 0.63mW.

Both the PDs are calibrated into mA in the front end, which includes anti-gain of gain(0.25)gain(0.22027), transimpedance of 0.001 (1kOhm), two anti-whitening filters (and cnts2V and mA factors).  For PDA there is a fudge factor in the filter gain, if we divide this out, the readback is that the PDA photocurrent was 0.512mA, and 0.5126mA for PDB (with a drift of 0.5% over the measurement time).  This gives a responsivity of 0.855A/W for PDA and 0.813A/W for PDB.  For QE of 1, the responsivity would be e lambda/(h c) = 0.8582 A/W, so our measurement is 99.6% QE of PDA, and 95% QE for PDB.  (See Vicky measured higher reflection off PDB than PDA in 63893 and Haocuns' measurement in 43452).  

The nominal value of the squeezer laser diode current was change to 1.863 from 1.95. The tolerance is unchanged at 0.1. Looking at trends we sometimes read a value just below 1.85 leading to a failed laser condition which in turn triggers a relocking of the squeezer laser. However, since we are already locked, all we see is the fast and commen gains ramping down and up.

Camilla and I removed the auxillary laser from HAM7 this morning, but left the irseses in place. 

Before removing the laser we noted that there was 0.25 NSUM counts on both OMC QPDs, with 21mW out of aux laser.  This is with the laser current at 150 mA, and the OMC QPD sums were similar to last week. 

We then switched to the squeezed beam from HAM7, using the OPO dither lock.  We temporariy turned the power into the seed fiber (which has no fiber switch right now) to 77mW, and measured 1.18mW  leaving HAM7 at the gate valve.  We measured 0.78mW arriving at HAM6 before OM1, which agrees well with SRM transmission of 34.34%.  We saw the SQZ beam on the OMC QPDs, 0.015 and 0.013 counts NSUM.  (This is a slightly higer ratio of NSUM counts to measured power incident on OM1 than for the aux laser.  Keita tell us this is not suprising since the aux laser beam size was large.  

We wrapped the breadboard that the aux laser was on in foil and brought it to the optics lab, and Camilla turned the seed power back down.