Daniel, Dave:

h1ecatc1, the Beckhoff slow controls system, crashed at 15:38 this afternoon. The EDC is showing 35365 disconnected channels. The computer is completely unresponsive, including its management port. It will need a manual reset.

The alarms system restarted itself at this time. The ongoing HAM6 alarms remain bypassed, and in addition I have bypassed some invalid temperatures channels

Bypass will expire:
Tue Feb 20 03:49:26 AM PST 2024
For channel(s):
    H0:VAC-LX_Y0_PT110_MOD1_PRESS_TORR
    H0:VAC-LY_Y1_PT120B_PRESS_TORR
    H1:PEM-C_CER_RACK1_TEMPERATURE
    H1:PEM-C_MSR_RACK1_TEMPERATURE
    H1:PEM-C_MSR_RACK2_TEMPERATURE
    H1:PEM-C_SUP_RACK1_TEMPERATURE
 

WP11702

The file copy completed at 12:23 Sun 18th Feb. This morning I reconfigured NDS1 daqd to serve the past 6 months of data from the permanent archive area, daqd was restarted at 08:44 this morning.

The old files were then deleted from TW1's SSD-RAID between 08:53 and 10:54, taking 2hours 1min.

Mon Feb 19 10:11:56 2024 INFO: Fill completed in 11min 52secs

Start time has been changed to 08:00 for tomorrow's early fill prior to CDS network upgrades.

Sun Feb 18 10:10:41 2024 INFO: Fill completed in 10min 37secs

Sat Feb 17 10:10:46 2024 INFO: Fill completed in 10min 42secs

WP11702 TW1 offload

I've started the process of offloading the past 6 months of raw minute trends from TW1's SSD-RAID to h1ldasgw1's permanent storage.

The first step was to freeze the almost full directory and switch TW1 over to writing to a new empty area, and then temporarily configuring NDS1 to serve data from the frozen dir while the file copy is in progress.

To this end, NDS1 daqd was restarted at 10:14 PST this morning.

Today's activities:
- HAM7 pumpdown status: ~3.3E-6 Torr
- Corner pumpdown status: ~3.9E-1 Torr. On Tuesday, transitioning to Turbo (Y-manifold; OMC; HAM6)
- EX pumpdown status: 3.75E-8 Torr: the post-vent RGA scan is ready, the results will be in the comment comment section, once they are published. The comparison with past RGAs is also coming next week. If the results will be considered satisfactory, the Ion-pump will be valved in. The GV will remain closed during FAC works
- The purge air supply at FCES is switched on, in order to start HAM8 vent first thing next week

Naoki, Nutsinee, Daniel

We installed all the optics for PMC and locked the PMC with p-polarization. We will lock the PMC with s-polarization and align SHG, CLF, seed next week.

First we put a HWP before PMC and changed the beam to the p polarization since the p-pol has much lower finesse in PMC and it is easy to align. The HWP angle is 152 for p-pol and 108 for s-pol. 

We aligned two steering mirrors before PMC. Fig. 1 and 2 show the PMC trans (blue) and refl (red) with PMC scan. The mode matching is 93% and the refl dip reaches 88% from the maximum.

We found that the label of the pick off mirror before PMC REFL PD says R=5% for s-pol, but it was actually R=90% for s-pol and R=70% for p-pol. The PMC REFL power is ~30mW and more than 20mW was injected to PMC REFL PD, which is a lot. So we replaced this mirror with the mirror which is R=8% for s-pol and R=1% for p-pol.

Then we adjusted the demod phase of PMC PDH signal and locked the PMC with p-pol. The UGF is 1.3 kHz and phase margin is 67 deg as shown in Fig. 3. We accepted the SDF related to PMC as shown in Fig. 4. 

Note that we will have 20 times more optical gain with s-pol because of higher finesse. Also we will have 8 times more power at PMC REFL PD with s-pol because of the pick off mirror. So we need to reduce the gain by 160 with s-pol to have the same UGF as p-pol.

TITLE: 02/16 Day Shift: 16:00-00:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: Another busy day; CS volumes still pumping down.

• SQZ PMC work continued (LVEA remains in laser HAZARD)
  • HAMs 6 & 7 ISIs tripped during this work
• A plugged in forklift near HAM8 tripped the breaker powering the RGA tree; caught and fixed this afternoon
• Top monitor of nuc28 is dead

LOG:

Fil, Luis, Camilla. FRS 26828#c11 Previous troubleshooting in alog 74951, 74750.

Today Fil went onto the HWS table and verified the HWS cameras are connected straight to the external power supply (photos in FRS26828#c8) via cables connected together. The HWS camera fiber CLink box is powered by the HWS breakout chassis D1200934 (originally designed to power cameras too).

Fil theorized that the HWS grounding is due to the power supply to fiber CLink connection grounding the cameras! With a multi-meter, we verified the HWS camera is grounded to the table when the CLink power cable is connected but when we disconnect CLink power, the camera is not grounded to the table (has Kapton tape and plastic bolts).

Step 1 (Completed): I removed the grounding cables from the HWS external power supply as Luis suggested in FRS 26828#c11, to avoid us holding the cameras negative terminal at mains ground. Photo of current connections attached. 

Step 2 (Planned): After verifying step 1 doesn't effect the combs (need overnight "quiet" data), Fil will make a new cable to power both the camera and CLink's via the external supply (14V is fine for both). 

Fri Feb 16 10:11:32 2024 INFO: Fill completed in 11min 28secs

Gerardo confirmed a good fill curbside.

This log follows up some previous work that's been done to understand the LSC, in particular MICH, noise coupling that we have observed. The most recent work done on this front was by Dana, in alogs 74477 and 74787.  Notably, the MICH coupling follows an interesting shape here, especially below 20 Hz. For MICH, we expect a flat coupling depending only on the finesse, Gm = pi/2*F. Evan Hall made some great measurements of this coupling years ago and you can see the results in Fig 2.17 of his thesis(link to thesis)- without any feedforward the magnitude of the coupling is flat in frequency down to 10 Hz. However, Dana's measurements clearly show a frequency dependent coupling below 20 Hz. Also, Dana mentions that the MICH coupling is about 40% too high than we expect based on finesse.

I'll add here a quick note that currently the UGF of MICH is about 8 Hz and the UGF of SRCL is about 11 Hz, so I think it's safe to assume that we are not seeing any significant closed loop effects from either of these loops down to about 12 Hz in these measurements.

Something to remember here is that when we measure the MICH coupling we drive the beamsplitter which does induce a change in the MICH length, but it also changes the SRCL and PRCL length. Therefore, we should expect to pick up SRCL coupling along with the MICH coupling when we measure. Evan's thesis also includes the form of the SRCL coupling in Eq 2.29: Gs = 0.012 [m/m] * Pa/750 [kW] * dL/10 [pm] * F/450 * (10 [Hz] / f)^2 (I am only including the first term that dominates at low frequency). The SRCL coupling results from radiation pressure in the SRC due to the DARM offset (dL), power in the arms (Pa), and finesse (F) and follows a 1/f^2 slope (again, I am ignoring the second term here that rises like f^2 at high frequency). We are operating at much higher power and double the DARM offset, Pa=370 kW and dL = 20 pm (and F = 440).

Regarding the 40% excess MICH coupling, if you divide Dana's result by an additional sqrt(2), it lines up exactly how you would expect. Is there a chance the MICH calibration is missing a rt2 factor related to the fact that we measure from the beamsplitter?

Assuming I'm correct about the sqrt(2) factor, and plotting the magnitude of the expected MICH and SRCL coupling along with Dana's calibrated measurement, our expected O4 SRCL coupling lines up almost exactly with the response at 20 Hz and below (see first attached plot).

I think this effect has always been there, but not easily observable because the SRCL coupling was much lower due to lower operating power and smaller DARM offset. Comparing Evan's MICH coupling measurement (Fig 2.17) with his SRCL coupling measurement (Fig 2.18), the SRCL coupling at 20 Hz was close to an order of magnitude lower than the MICH coupling.

I think this understanding of the coupling better explains why we need to put so much work into the LSC feedforward. Specifically, we measure the coupling for MICH and SRCL, and then usually tune MICH first and then SRCL. Then, to do our iterative tuning, we redo the MICH coupling. It's likely we could do a better job first just tuning SRCL and then measuring and tuning MICH, since we need to subtract the SRCL coupling well enough to get a "true" measure of the MICH coupling.

Furthermore, the SRCL coupling is dependent on our DARM offset. When we make changes to OM2, for example, we change the mode matching at the output. Since we servo to keep the amount of light on the DCPDs constant, we could be changing the required length to achieve this amount of light slightly. In principle, this should only effect the SRCL coupling, but since SRCL shows up in our MICH coupling measurement, it effects both.

Finally, it appears in Dana's measurement that there is a rising trend above 30 Hz, which I have no explanation for. I don't think that can be explained by the SRCL coupling. A look at that second term in the SRCL coupling equation: Gs = 3e-5 [m/m] * phi_s/10 [deg] * dL/10 [pm] * F/450 * (f / 100 [Hz])^2 (Evan's thesis Eq 2.29), I estimate that with a SRCL detuning of about 1 deg, around 30 Hz the SRCL coupling term with an f^2 slope is about 5.3e-7 m/m. This is both too small and the wrong slope to explain that feature.

TITLE: 02/16 Day Shift: 16:00-00:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 12mph Gusts, 10mph 5min avg
    Primary useism: 0.03 μm/s
    Secondary useism: 0.31 μm/s
QUICK SUMMARY: Corner volume continues to pump down; temperatures below freezing around 24F/-4.5C on-site.

Today's activities:
- The Annulus Ion Pump of HAM7 - after ~1.5 days of pumping - is now switched on. There was a leak at the septum plug - temporarily it is solved, the annulus pressure now is in the E-5s
- HAM7 pumping status: ~7.8E-6 Torr
- Corner pumpdown status: ~1.2 Torr
- EX pumpdown status: 3.88E-8 Torr: ready for an RGA scan
- A pre-vent RGA scan was made on HAM8. The results will be available in the comment section, once they are published

Copied from LLO (LLOalog69495), I've added this test to our DIAG_MAIN. I haven't tested by putting the CPSs into a bad state, but Jim and I will do this next week.

TITLE: 02/16 Day Shift: 16:00-00:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: Pumpdown efforts continue, SQZ table work created a local hazard in the East bay.
LOG:

The temperature of the chilled water loop at Mid Y was lowered from 46F to 42F to bring it more in line with the other buildings. Other than the initial pulldown, the effect will be minimal but will allow for a more consistent temperature trend.