J. Driggers, S. Dwyer, J. Kissel, E. Merilh, K. Merfeld

After the EQ, we've been having a lot of trouble even getting past the ALS of lock acquistion. We think we might have traced the problem down to the DIFF beatnote (H1:ALS-C_DIFF_A_DEMOD_RFMON) being too low. 
How did we come to this conclusion? A trend of the DIFF beat note over the past many moons revealed that on July 31 / Aug 1 -- when we changed the global alignment -- the trend of the DIFF beatnote consistently dropped from -10 dBm to -25/-26 dBm. Suspecting that 
    (a) this is yet another knock-on effect of the new global alignment position, and 
    (b) that we've just been Aerosmithing our way through life (living on the edge) the past few weeks,
and confirming improvement by adjusting the beam splitter alignment just after an initial alignment (3 urad! in yaw) to regain ~5 dBm of power, we've taken the following actions:

    (1) [After restoring the beam splitter alignment] we've gone out to ISCT1 and adjusted the alignment on to the DIFF beatnote PD.
    (2) Added a check to the ALS_DIFF guardian in the "run" part of its PREPARE state to spew out a notification (sadly only at the ALS_DIFF guardian level) and loaded it. We set the threshold to -26 (dBm).

I measured the output power of the recently-removed SQZ NPRO laser SN 8552.  The laser settings were found as last set by the SQZ team:

• NPRO Crystal Temp: 31.68 °C
• Diode Current: 2.025 A
• Diode Temp: 20.21 °C

I set the laser settings to those specified in the original data sheet; the set value for the NPRO Crystal temp is slightly different from the actual value, and the power supply reports both numbers so I recorded the actual crystal temp as well.

• NPRO Crystal Temp: 25.10 °C
  • Actual Temp: 25.11 °C
• Diode Current: 2.15 A
• Diode Temp: 20.20 °C

I allowed the laser to warm up for ~5 minutes before taking the first power measurement.  For the measurement I used an Ophir VEGA power meter with an Ophir PD300-3W head.  After the intial reading, the power was slowly increasing, so I waited until it stabilized, noting the power measured a few times over the duration:

• Intial measurement, t0: 0.925 W
• t0 + 10min: 1.015 W
• t0 + 25min: 1.054 W
• t0 + 35min: 1.055 W

The data sheet reports an output power of 1.05 W using the initial settings, so this laser seems fine from an output power standpoint.  I took one last reading of the laser settings to see if things had changed since I started; they had, albeight slightly:

• NPRO Crystal Temp, actual: 25.12 °C
• Diode Current: 2.149 A
• Diode Temp: 20.18 °C

Since the NPRO only had a couple hours to acclimatize to the optics lab environment, I'll let it sit overnight and repeat these measurements tomorrow to make sure everything is unchanged.  As of right now though, the power out of the NPRO matches the original data sheet.

J. Driggers, S. Dwyer, J. Kissel, T. Sadecki

We were able to successfully move the spot position on ITMY this afternoon, while in otherwise Nominal Low Noise at 37W, in order to make progress toward reverting the global alignment position to prior to the position found to work on July 30 / 31, as part of the plan to fix several problems that have arisen because of the new position (see LHO aLOG 51262). 

Progress was stalled then halted due to a GW event candidate (yay!), and 30 minutes later a lockloss from an earthquake in Mexico (boo!).

Here's a mid-adventure report so there's less to talk about later.

The path for the spot position move was to swing *around* the point absorber. As such, Jenne and Sheila did the following:
    - Increased the gains on the ADS YAW 3 loop (from 1.0 to 10.0) and the SRC1 PIT / YAW loops (from 12 to 18, and from 4 to 6, respectively)
    - slowly adjusted the A2L gains on ITMY (H1:SUS-ITMY_L2_DRIVEALIGN_P2L_SPOT_GAIN and H1:SUS-ITMY_L2_DRIVEALIGN_Y2L_SPOT_GAIN) 
        - first swinging "out wide" in YAW, increasing the gain from 0.0 to 3.5
        - then restoring the PIT position / gain to the Prior-to-July values (from -2.0 to -3.0)
        - then restoring the YAW position / gain from 3.5 to 0.0
        - then changing the ITMX PIT and YAW positions to minimize the coupling to DARM (the ITMX position and ITMY position are closely coupled by the ASC system, but we don't use the ADS system to servo the spot position on ITMX to the same place.)
Notably, we were discussing a path forward when the GW candidate came through, so we had not yet moved the spot positions on the ETMs before we lost lock.

We noticed several things along our journey and about our end positions -- to see these conclusions, check out the trends of relevant channels during the spot moves today (2019-08-14_DuringSpotMove_After.png), and just before we moved them on July 31 (2019-07-31_DuringSpotMove_Before.png):
    (1) [Row 0, Column 2] RF45 Noise has returned to July-level noise -- drastically reduced. Great! (as displayed by H1:LSC-REFL_A_RF45_DEMOD_RFMON) 
    (2) [Row 0, Column 0] The POP18 build up is actually a bit *higher* than July-level. Great! (as displayed by H1:LSC-POPAIR_B_RF18_I_NORM_MON)
    (3) [Row 1, Column 3] The DARM coupled cavity appears to be a bit higher than the July-level. Great! (as displayed by H1:CAL-CS_TDEP_CAVITY_POLE_RAW_F_C_MON / 400 Hz) 
    (4) [Row 0, Column 0] PRC gain is roughly the same. Good. (as displayed by H1:LSC-PR_GAIN_OUT16)
    (5) [Row 1, Column 3] The DARM loop optical gain (\kappa_C) is a bit lower,  but we haven't tuned up the OMC ASC alignment offsets yet. OK. (as displayed by H1:CAL-CS_TDEP_CAVITY_POLE_KAPPA_C_MON)

Also note that a before vs. after spot position move drastically cools the HWS image around the point absorber -- consistent with the fact that the new positions no longer heat up the point absorber (see 2019-08-14_H1HWSData_FromReferenceToHoldPoint_2.png).

These effects lead us to believe that we're doing the right thing by going back toward the pre-July spot positions. Indeed, we are even considering *not* moving the ETM spot positions, because the cavity pole and DRMI power / POP18 buildups are a bit better than before. Jenne remind us that the ETM spot positions were chosen *solely* because they were the former positions that had the highest buildups back in the late Apr / May, so we're not married to them.


However, since all this was half-way through our goals for the day, we now have the following ideas/plans forward if we relock quickly:
    (a) Re-lock the IFO without doing any initial alignment -- hoping that our work will not have gotten lost with the EQ.
    (b) Re-acquire all the way to DC readout at 2W (i.e. after full IFO alignment, and SOFT LOOPS have been engaged).
    (c) Gather/Record initial alignment references at both centered spot positions (all zero A2L gains) as well as either today's new positions (IY and IX restored, but with ETMs still at Early Aug values) or Pre-July positions. 
        >> decision point at this time unknown -- to which do we set the initial alignment offsets -- centered, Pre-July, or New?
    (d) Head up to full 37W.
    (e) Tune up OMC ASC alignment loop offsets to regain as much DARM loop optical gain as possible
    (f) Remeasure sensing function.

We'll see how far we get. We're still formulating a plan for "what if we don't get even past (b)" for the operator corp to do overnight.

For future reference, I also attach a more detailed but more rough diary of the afternoon's activity (2019-08-14_SpotMove_Diary.txt).
I also attach a screenshot of the spot positions I reference in this aLOG: Pre-July 30/31, Post July 31, and Today. (2019-08-14_H1TM_SpotPositions.png)

TITLE: 08/14 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Lock Acquisition
OUTGOING OPERATOR: Travis
CURRENT ENVIRONMENT:
    Wind: 14mph Gusts, 12mph 5min avg
    Primary useism: 0.07 μm/s
    Secondary useism: 0.14 μm/s
QUICK SUMMARY:

Still struggling with the lock as a result of beam pointing changes. EM follow up channel still abuzz with Superevent chatter from S190814bv.

TITLE: 08/14 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Lock Acquisition
INCOMING OPERATOR: Ed
SHIFT SUMMARY:  Currently relocking after EQ.  Commissioners will continue with spot moving after reacquisition. 
LOG:

16:01 Set to Calibration mode for calibration measurements

16:49 Back to Observing

19:44 Commissioning mode for spot move work

20:05 GRB alert. Trigger duration too long.  Carrying on with commissioning.

20:08 Ethan to optics lab

20:35 Peter to optics lab

20:46 Ethan out

21:12 Superevent candidate S190814bv

21:43 Jason to optics lab

21:51 Lockloss due to Mexico EQ

21:55 Peter out

Used the downtime from the earthquake to optimioze the steering into the SHG using the pico motors. Gain about 3% of green power.

Also added the green AOM to the squeezer overview screen.

We noticed some curious jumps in the CLF power as measured by the CLF REFL PD. These jumps are also visible in CLF launch and rejected monitors. They are not visible in any of the other PDs on ISCT6 that are not associated with the CLF. See attached plot 1. We see coherent jumps in the RF output power readback of the 200MHz AOM driver. See plot 2.

The jumps in the CLF power are as large as 20%, whereas the RF power to the AOM only jumps by 5% or less.

JeffK noticed that the PCal X was glitching and corrupting the DARM spectrum.  We had a quick look at the PCal MEDM screen and nothing seems awry.  Perhaps more investigation should be done to find the cause of the new glitchiness?

Both chillers were full and required 0 additional water.  Both filters look good. FAMIS 10522.

J. Kissel

I wanted to get one last (a third) measurement of the sensing function in the current spot positions before we make the change back to the pre-July 31st positions (see plans in LHO aLOG 51262), such that we can confirm th pattern we've seen that -- in this spot position -- the low frequency response is consistent and casual.

I've successfully completed the measurements, and the data looks good [I even added a few more data points at low frequency to better resolve the feature, since our MCMC fitting algorithm continues to be quite confused by it]. Processed results to come later, but at first glance they indeed confirm that the low frequency response is quite similar.

Data lives and has been committed here: 
2019-08-14_H1_DARM_OLGTF_LF_SS_5to1100Hz_15min.xml
2019-08-14_H1_PCALY2DARMTF_LF_SS_5t1100Hz_10min.xml
2019-08-14_H1_PCALX2DARMTF_LF_SS_5t1100Hz_10min.xml
2019-08-14_H1_OMCDCPDSUM_to_DARMIN1.xml
2019-08-14_H1_PCALX2DARMTF_BB.xml
2019-08-14_H1_PCALY2DARMTF_BB.xml

The water level for the TSC-X chiller is good. No additional water added.
Added 200ml water to the TCS-X chiller. 
All else with the chillers looks good. 

  Closing FAMIS 11504. 

J. Kissel, K. Kawabe, D. Sigg, J. Driggers, S. Dwyer

This is just a heads up for folks off site, and for historical record of motivations: The commissioning team plans to restore IFO beam spot positions on Test Masses today.

The major reasons cited for "why"
    - RF build-ups are poor LHO aLOG 51175
    - ITMY spot position is on top of the point absorber LHO aLOG 51225
    - Lock acquisition vs. initial alignment has been a bear, e.g. from LHO aLOG 50952 to LHO aLOG 51112
    - New low-frequency glitching LHO aLOG 50973

So the plan is to remeasure the DARM loop sensing function (which has been stable and more physical in this position) one last time before the spot move (at ~9a local), then break the lock (at ~12-12:30p local), and move the spot positions at 2W.

TITLE: 08/14 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Observing at 99Mpc
OUTGOING OPERATOR: Corey
CURRENT ENVIRONMENT:
    Wind: 5mph Gusts, 3mph 5min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.17 μm/s
QUICK SUMMARY:  Lock is 16.5 hours old.  No issues to report.

Starting at ~9:31 utc have noticed elevated levels for DARM BLRMS bands:

• 500-1kHz
• 1kHz-2kHz
• And higher as seen on DARM spectrum

The noise went off and on for 45 min (so far) and looks to start/stop suddenly and then last on the order of a minute and over 10mins (attachment#1 is the DARM blrms where you can see the steps up in noise over most of the 45min.  Time periods for some of these are about:

• 9:50-10:02utc  Attached is a DARM spectra (w/ quiet reference)
• 10:05-10:06 this was quieter than above and not quite as broadband, see attachment

NOTE:  H1 range did not take a hit during this time.  It's been almost 2hrs since this noisy period last occurred.

Summary: I've an estimate of the squeezing angle fluctations caused by phase noise at the OMC DCPDs from the interferometer control sidebands(~6mrad rms), which is far too small (~6mrad) to explain our apparently high level of phase noise infered from squeezing and anti-squeezing measurements (on the order of 100mrad).  There are several assumptions that go into this, but for reasonable values of the sideband imbalance, sideband power at the AS port or contrast defect won't result in 100mrad phase noise.  However, if the power at the AS port is mostly in a higher order mode for the sidebands, and that higher order mode has a larger transmission through the OMC than what I have used, we could potentially generate much higher levels of RF phase noise.  At LHO we have seen evidence of a 9th order 9MHz mode being transmitted through the OMC, so it may be worth using the information from a OMC scan with Koji's model of OMC transmission for higher order modes to check how much sideband higher order mode we could have at the AS port.

Details:

Power percentages at AS port: 19.4% carrier, 74.3% 45 MHz, 6.3% 9 MHz alog 48595  The 9MHz power for L1 could be much smaller, we don't understand the 9MHz power levels in H1.

OMC transmission: Finesse 390 FSR 264.8MHz (T1000276).  Power transmission of 00 mode for 9 MHz 3.53e-4; power transmission for 45 MHz 2.08e-5

Power on DCPDs: 

• total power on DCPDs is 23.3mW (20mA, responsitivity of 0.858A/W), assume this is nearly all carrier. 
• 45 MHz power is 1.86uW
• 9MHz power is 2.67uW
• Here I am acting as though all of the power is in the 00 mode, although as we have seen there is a higher order mode for 9MHz which also has a high transmission for the H1 OMC and could contribute.

Contrast defect:

• Most recent measurement was by Craig at 2W input power was 8ppm of input power (46142).  If we scale this with input power, we would predict 0.15mW of contrast defect light on the DCPDs at 37W input power, although the power recycling gain drops as we go to 37W input power and the contrast probably gets worse due to point absorbers. 
• Evan Hall's 2016 measurement 30573 was made with 50W input power, which would have been fairly similar to our current circulating power with the reduced recycling gain at the time.  With different fitting methods he and Gabriele found 1.8 to 5 mW contrast defect light, so one order of magnitude larger than Craig's measurement. The current situation might be better than this since the point absorber on ITMX is no longer bothering us.
• There's about an order of magnitude difference between these two estimates, but I will use the numbers measured at higher power since that seems like the most simliar situation.  I do think that there is a more recent measurement of contrast defect at high power, I will update this entry if needed.

Sideband imbalance:

• We would ideally use OMC scans to estimate the sideband imbalance for the 00 modes, as well as any other modes that are large enough after filtering through the OMC to have an impact.  We do have OSA scans that give us some estimate of the sideband imbalance with all the modes included: 44582  By eye, there is about a 20% difference in power between the upper and lower sidebands of 45MHz, and about a 60% difference for 9MHz.

The rms phase noise due to contrast defect light is given by eqn 5.60 here the phase noise due to sideband imbalance is given by 5.62, although there is a factor of 2 in 5.62 that I don't understand (think could be wrong) and am leaving out here. With the assumptions above I estimate:

The quadrature sum of these contributions is 6 mrad, which is enough to have an impact on our total budgeted phase noise, but not nearly enough to help explain the large excess of aparent phase noise based on measured squeezing and anti-squeezing.

During the current lock and after being at NOMINAL LOW NOISE on the order of 45 min, all of a sudden have begun to see a broadband bump on DARM (attached is a screenshot showing instance where the bump is seen on the DARM spectrum & you can also see how often it is occurring on the DARM BLRMS striptool).  It is also seen on DMT Omega.  The range has only taken a small hit of about 5Mpc (down to 112 Mpc from 117Mpc).

Only difference I accepted for this lock was the enabled filter for ASC PRC1_P FM1 (-20dB). 

Will start taking a look at the H1 Summary Pages to see if I can glean anything from them.

Note: 

• I increased the Y-axis on DARM BLRMS for the 500-1k & 1k-2k axis from 0.100 to 0.300 so this noisy period could be viewed on the StripTool.
• From 12:37 to now (~8min) it has not been noticeably observed.

I calibrated the DARM offset at 20 watts input power.  The calibration of the H1:OMC-READOUT_X0_OFFSET channel counts into picometers is 0.636 pm/cts.  

I did so using the antisymmetric power on the OMC DCPDs [mA] compared to the DARM optical gain [W/m] as calculated by the ratio of the 331 Hz PCAL line [m] and OMC SUM [mA] response at the same frequency.  The math looks the same as here but I have accounted for the slight drop in response from the DARM pole.


Numbers used:
-------------------------------
DCPD Responsivity = 0.858 A/W
DCPD Quantum Efficiency = 0.98
DARM pole = 421 Hz
PCAL Line Frequency = 331.8 Hz


Plot 1 is the antisymmetric power vs the DARM offset.  (I also did this at 2 W.)  Things here are consistent with very little contrast defect light in full lock, we'll have to lock RF DARM and the OMC to carrier to see what our actual contrast defect is.
Plot 2 is the DARM optical gain vs the DARM offset.

I put this calibration into the H1:OMC-READOUT_X0 filter module but did not engage it.

---------------------------------------------------------------------------------------

What's interesting here is that if you work out Kiwamu's theoretical calculations from page 8, eq 11 of here, things don't line up at all (~factor of 4 difference in calculated DARM offsets).  I'll need to think more deeply on this, because we could learn something about the state of the IFO (signal recycling gain, arm reflectivity derivatives).  In the real IFO there are some power losses here and there (OFI trans, OMC trans, OMC mode match, etc) that could confuse us as well, we can use 20 W vs 2 W to eliminate those.