Late entry: yesterday we measured the hard loops with the sweep sine templates. Results attached.

The strange thing is that CHARD has a much lower phase margin than expected, and lower than DHARD. Our expectation would be that the C and D loops should be similar. Also, it looks like CHARD has an additional slope at low frequency.

The templates XML files are in /ligo/svncommon/IscSVN/iscmodeling/trunk/ALIGOH1/ASC_loops/Measurements/DHARD and /ligo/svncommon/IscSVN/iscmodeling/trunk/ALIGOH1/ASC_loops/Measurements/CHARD: CHARD_P_OLG_SS_2W.xml, CHARD_Y_OLG_SS_2W.xml, DHARD_Y_OLG_SS_2W.xml, DHARD_P_OLG_SS_2W.xml

16:15 HAM6 tripped, I went out and poked around at the satellite rack, but didn't find anything

16:45 LSC model crashed, Dave & JeffK recover

17:45 Nutsinee to ISCT6

18:00 Gerardo to MX

18:00 Ed to HAM7

19:00 Marc to CER

21:45 Terry to ISCT6

WP 7856

Per Chandra's request I have changed the low alarm limit for H0:VAC-LY_CP1_II170_AIP_IC_LOGMA from -2 to -3.5: caput H0:VAC-LY_CP1_II170_AIP_IC_LOGMA.LOW -3.5

This is only done in EPICS, so will be reverted if the IOC gets restarted.

Same as was done at an earlier date for CP2 (WP 7787 and alog 43593).

Attached are the VPW desiccant plots with the last month's added data.  All 4 data readers are recording data as they should.  Nothing out of the ordinary shown.

FRS11570

Jeff, Gabriele, Dave

This morning we had another instance of the H1LSC_SRCL1 filter-module giving a very high output when an offset is enabled and FM1 is attempted to be switched ON.

The attached image shows:

1. Input is turned OFF
2. OFFSET is set to 1.0 and is turned ON
3. FM1 has been attempted to be turned ON

The result is that FM1 is not turned ON, but the output of the filter-module goes very high (1.2e+10).

On Monday changes were being made to this filter around the time the problem occurred. Today it appears to have broken spontaneously.

As with Monday, restarting the h1lsc model fixes the problem.

Here is the "+106dB" filter line in the H1LSC.txt filter file:

 LSC_SRCL1 0 12 1   4915      0 +106dB     2.000000000000000000000000e+05   0.0000000000000000   0.0000000000000000   0.0000000000000000   0.0000000000000000

Georgia, Terry, Sheila

Over the past couple of days we have set up the OSA at the AS port.  We had used this to tune differential CO2 powers to reduce the sideband imbalance before O2.   We set the OSA up behind the squeezer laser, and added and ROC= +150 lens to roughly collimate the beam. The OSA is a coherent 216G, we used a Thorlabs PDA100A to monitor the transmitted power.  The trigger channel and the output of the diode are plugged into a couple of extra ADC channels from the squeezer, H1:SQZ-EXTRA_AI_1 is the diode signal and EXTRA_AI_2 is the trigger.  

Attached is a plot of the scan taken part way through the power up to 15W (REF0) and about 1 minute after powering up to 15W.  We would like to look at this during a longer lock.  

TVo and I closed the iris to cover the problematic back reflection on HWS ITMX this evening. Screenshot with the Hartmann plate off attached.

We looked on the ccd for some dust that would cause the circular fringes in the image but it looked clean.

We restarted the Hartmann code for ITMX at 1222663398. At this time the ifo was locked at 2W and there was 500 mW of CO2X on.

If you run the filter_diffs command with a -m option, it will display the differences using meld instead of vim. Meld is a more visually appealing display, but it is graphical and so won't work remotely unless you have set up X forwarding. Vim on the other hand is text based and will work remotely.

the output of

filter_diffs -m h1asc

is shown in the attachment.

16:00 Betsy Hugh to MY

17:00 Karen to MY

17:30 Betsy, Christina, Nichole to MY

18:00 Nutsinee to ISCT6

20:00 Sheila to ISCT6

21:00 Nutsinee to ISCT6

21:30 HAM6 trips on CPS, doesn't look like any one is around

23:00 Terry to ISCT6

This afternoon, HAM6 ISI tripped all on it's own, seems like it was probably some sort of glitch in the CPS. Attached trip plot shows all 4 cps in one satellite rack see a sharp spike, that the other 2 CPS don't see. The GS13s also don't see this spike, suggests to me it wasn't real motion and has something to do with satellite rack. Looking at trends of the HAM6 wd, there have been 2 other trips on the HAM6 since the beginning of the month. More investigation is required.

The calibration of H1:CAL-DELTAL_EXTERNAL_DQ is off. The calibration team will work on rough calibration, so we need to wait for that to see reasonable data for the entire band.

For the moment, though, the high frequency part seems to be a factor of 4-ish too large (see attached).

• Running A2L helped sensitivity.  Script seems like it reverted the A2L gains, and we lost the improvement after the script finished ETMY P2L.  I trended the P2L value, and setting it back to the 2.2 it was during the time that the range was good (vs. the 2.8 it decided on) brought the range back up. This is a 5% range increase.
  • Probably when the A2L value started far from the correct answer, we need to run it again. We should add a warning or summary of then/now a2l gains at the end of the a2l script.
  • Happened again, after moving CSOFT P offset.
• 6:45am, starting to go up in power, very slowly. 
  • 7:03, arrive at 15W injected.
• Moving SOFT and PRC1 offsets:
  • Dither CSOFT_P at 0.03 Hz.  Can see with even amplitudes of 0.003 that we could improve the power buildup in the arms.
    • Had to move PRC1_P offset to keep POP_B_18 high and POP_B_90 low.  Alternated between CSOFT_P and PRC1_P offsets.
  • DSOFT_P had almost no effect on circulating power.
  • CSOFT_Y improving circulating power.  No need (yet) to change PRC1 offsets.  POP18 staying high, POP90 actually getting better.
  • Since SRC ASC loops are open, Gabriele moved SRM to get POP 90 power low.
  • Moved offsets from the loop error points to the QPDs themselves for TRX, TRY, POPA.
  • Ending recycling gain = 49
• Ran A2L
• Increasing power again at 8:45am to 20W injected.
• PRCL gain is too low (MICH, SRCL okay). PRCL UGF was 30 Hz with 26 deg phase margin with digital gain of 8.  Increasing to 12.
• Increasing power again at 8:57am to 26W injected.
• Fast lockloss after ~5 min at 26W injected.  Guardian lockloss time: 1222617719.9375. Actual lockloss is at about -2.88s from there.
  • CHARD sees something at -3.9s
  • LSC-MICH sees a small glitch at -3.9s
  • LSC-POP_A_RF45_DEMOD_RFMON starts walking upward from -27 toward +8.5, starting at -5.2s, and hitting +8.5 just before the lockloss.  Other DEMOD_RFMONs don't see this walk-away.  POPAIR_B_RF90 doesn't start increasing until much closer to the lockloss. 
• Re-exectued TCS CO2 guardians so that it will turn on preheating.
• Initial alignment.
  • Xarm green ASC worked, but only after I hand aligned it to be quite close. 
• Relocked to 15W with no problems, other than a long time to acquire both PRMI and DRMI.
  • Gabriele has measurements of the HARD ASC loops, they seem much more marginal than they were in O2.  Other than a sign flip in the filter bank gain (haven't checked if there is a matching / undo sign flip elsewhere yet), the gains and filters are the same as during O2.  The DHARD gains are a little higher now, but all the filter modules have stayed the same.
  • Lost lock reducing CHARD_P gain while trying some lownoise ASC tuning.

While h1psl0 is running without its Dolphin cable attached, there are two IPC errors on the overview screen for the models h1psliss and h1lsc. I've notched these out for now and will return them when the PSL dolphin is restored.

[Jenne, Gabriele]

Trying to understand why locking PRMI and DRMI takes much longer, we looked at a few things:

• in PRMI, we checked that the REFL9 and REFL45 demodulation phase are ok.
• in PRMI also the loop shapes and unity gain frequencies are ok

Then we moved to DRMI and found that the demodulation phases for REFL9 and REFL45 were a bit off. So we retuned them(REFL9 from -23 to -20, REFL45 from 97 to 88)

Then we measured the longitudinal loop gains (with DRMI still locked on REFL 1F), and found

• SRCL is ok (there were some wiggles before the phase tuning, due to PRCL cross coupling).
• MICH has higher gain in DRMI than PRMI, but still in the stability margins
• PRCL instead showed some large and weird wiggles at frequencies between 15 and 40 Hz. The structures there are smaller when DRMI is locked on 3F, but still there. They are gone when we switched off the BS bounce and roll notches: with the notches off there are no more weird structures, but the phase still rotates a bit too much. So we have a large cross coupling from MICH to PRCL, that causes a lot of phase rotation and amplitude changes in the PRCL open loop gain when we are on REFL 1F. This surely can't make the lock acquisition any easier.

At the next lock attempt, we should try to switch off the BS notches and see if this makes the lock acquisition easier. We should also improve the REFL 1F sensing matrix to get rid of those cross couplings.

Niko, Tvo, Georgia

A couple of weeks ago (alog-44087) TVo and I posted a comparison of HWS contours for the ring heater, IFO beam, and CO2 beam positions on the HWS. Niko has since added a feature to the HWS contour code to calculate the centroid of the contours, which I am still tweaking up. This will help work out spot (mis-)centering on the ITMs using the Hartmann

Attached screenshot is the same contours as those from TVo's log with the centroids added (see blue spots, and position info in the plot titles). The full IFO and CO2 positions relative to the ring heater centroids is tabulated below:

I don't think the 5mm shift in the IFO beam x position between September 12 and 13 is real but rather an indication of the uncertainty. It's interesting that we seem to generally be better aligned in x (yaw), and worst in y (pitch) given the snowman mode we see at the AS camera with the CO2 lasers on.

Currently the centroid calculation only uses the highest 1/3 of the wavefront contours, as using the full data biased the data away from the beam center. It also currently only works for cool-down data.

TVo, Georgia

Last night we powered up to 20 W before losing lock. Today TVo and I had a look at the ETM HWSs to see if we can see any thermal lensing caused by absorption. There is some absorption visible on ETMY HWS.

The first screenshot shows the PSL power [W], ETMX HWS spherical power [diopters], and ETMY HWS spherical power [diopters]. We can estimate the absorption of the optic from the circulating power, the measured thermal lens on the HWS, and the substrate and surface deformations (or lensing per unit power). A back-of-the-envelope calculation puts a first estimate of total absorption at 0.21 ppm. The absorption on ETMX is not visible above the noise.

The HWS beam passes through the substrate of the ETM, reflects off the HR surface, and passes through the substrate again. It samples the substrate lens twice and the surface lens once. So the thermal lens measured on the HWS is

L_tot [D] = (2 A_sub [D/W] + A_surf [D/W] ) * P_circ [W] * alpha

Where L_tot is the total lens in diopters, A_sub and A_surf are the substrate and surface deformations respectively in diopters per W, P_circ is the circulating power in the arms, and alpha is the optic absorption.

Going from 2 W to 15 W we see ~15 uD of thermal lens on the Hartmann. The circulating power at 15 W is ~95 kW (assuming 45 PR gain, 280 arm gain, and 50% reflectivity of the beamsplitter). The substrate and surface deformations as assumed to be 3.86e-4 D/W and -2.93e-5 D/W respectively (numbers acquired from the TCS simulation tool, not sure if they need updating with new test mass coatings).

This gives us an absorption of 0.21 ppm, which seems reasonable.

Final screenshot shows the HWS contour plots between the cold and hot ETM states.

Sheila, Georgia, Craig

Today we changed the phasing on REFL9 from 5.9 to 84.8 degrees.

We've been investigating fast locklosses, probably caused by CARM.  We noticed that if we moved the CARM servo board common offset around, we would win or lose arm power and see a change in the amount of DC power on REFL LF.  (Pic 1)
We also noticed that when powering up, we saw the offset in REFL9 I change by a lot, along with weird glitches in Q associated with servo board IN1 gain changes. (Pic 3)

We went out to the racks, injected a line into CARM above the UGF of about 10 kHz, and checked the REFL9 I and Q monitors. We found that the phasing was terrible: there was far more signal in Q than I.  We adjusted the phase, while measuring CARM and lowering the CARM IN1 gain from 3 dB to -9 dB to maintain our UGF.

After adjusting the phase, we tested the CARM servo board common offset again and found the arm power and REFL LF to be relatively insensitive.  (Pic 2)

Sheila and Georgia are changing the guardian so that our digital CARM gain is lower since we have so much more optical gain now.  I remeasured the CARM loop and posted the results in the pdf.  The gains are in flux right now, for this plot CARM servo board IN1 gain = 1 dB, and Sum Node A IN2 gain = -15 dB at 5 watts of input power.  

We powered up from 5 watts to 15 watts, and I watched REFL9 I offset again (Pic 4).  It still changed, but by about half as much as it did when we previously went from 2 watts to 5 watts in Pic 3.  We are sitting much closer to the resonance now that we aren't dumping a factor of 5 of our optical gain.