This morning, with an hour long 60mpc lock behind us, Evan and I cleared SDF from the weekend commissioning efforts.  We:

- accepted most of the re-phasing of the ASC/LSC PDs that was done (we reverted a few of his changes which he did not like). 

- set the SDF to ignore the LOCKIN channels that had been used over the weekend.

- zeroed out a few ASC loop offsets (MICH, DHARD, etc.) that were put in over the weekend during testing, but were then turned off.

- accepted Dan's change of the 4 OMC dither path gains from 0.1 to 1.0 on Wed Aug 6th (H1:OMC-ASC_P1_CLOCK_GAIN, ...)

J. Kissel, S. Dwyer

Sheila put together a new MEDM screen for the updates I made to the violin mode monitoring system (see LHO aLOG 20177). see attached. These have been used profusely during the ETMY 508.29 [Hz] violin mode saga (see LHO aLOG 20316).

Attached are plots of the NPRO output power, the output power of the NPRO pump diodes, and the output of the front end laser for the past 4 years.  Whilst there's not much wiggle room left on the NPRO pump diodes, there's room left on the power amplifier pump diodes.  The laser output should be good through to the end of O1.

The IFO was not locking for hours so I took the SEI to READY at EndX and restarted the Pump Servo.  This required a trip to the end station.  The controller started without issue and while the platforms were down, I captured safe.snaps for the ISI and HPI.  It has been a long time since we've had a pump controller hang like this, maybe I can pull this from the log.

The ISI did trip on the T240s but I don't know exactly what the platform was up to at the time.  I isolated fully second attempt no problem.

This is an alog about the (aborted) attempt between Saturday and Sunday to make the interferometer work at 0.43 W of TCS power.

The locking sequence was fine up through the dc readout step. However, the interferometer would lose lock at 10 W or higher. We've seen this kind of behavior before, and the culprit is usually the SRC1 yaw loop. I rephased ASA36 by driving SRC1 yaw at 0.3 Hz. Segements 3 and 4 (the two that we're using) both gained 25°. Segments 1 and 2 still have less signal than 3 and 4, which is what we saw before. At the end of the night I reverted these phasings. I also redid the dark offsets on these segments, and have left them there.

Rephasing ASA36 didn't seem to fix the problem, so I went through and rephased Refl A 9, Refl B 9, AS A 45, Refl A 45, and Refl B 45. For Refl 9, I drove cHard at 8 Hz in pitch . For Refl 45, I drove PR3 at 9.1 Hz. For AS A 45, I drove dHard pitch at 8 Hz. Many of the original segment settings were so far off in phase that I suspect they are bad even at the lower TCS power, so I did not revert these new settings at the end of the night.

I also looked into the subtraction of the Refl 9 signal from the PRC2 loop by driving cHard in pitch again. The ratio of the signal in the 45 MHz and 9 MHz WFS was Refl A 45 / Refl A 9 = −0.79 and Refl B 45 / Refl B 9 = −0.76. Our current subtraction settings in the input matrix assume a ratio of −0.60 for both A and B. We should recheck this at the lower TCS power and update the Guardian settings.

Finally, I looked at rephasing the LSC in full lock. I drove PRCL at 136 Hz and then rotated POP9 from 90° to 95° to minimize the apperance of the line in POP9Q. I repeated this for SRCL, but no rephasing was required. However, the subtraction of POP9I into SRCL was quite bad. I drove PRCL again while watching the SRCL error signal, and based on this I changed the matrix element for POP9I→SRCL from −0.04 to −0.012. This setting is in the Guardian (and should be rechecked at the lower power).

The CW injections were turned back on at gps = 1123224216. I believe they have been off since Jeff noticed on 21 July:

https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=19817

The hwinj team is in the process of setting up a monit / crontab to auto-restart the CW injections after failures.

J. Kissel, D. Tuyenbayev.

At the request of Duncan MacLeod, we've svn updated the CAL_INJ_CONTROL.adl MEDM overview screen for the hardware injection system. 

J. Kissel, C. Cahillane, J. Driggers

Today we explored some of the potential systematics in using the ALS DIFF VCO to calibrate the DARM ETM actuation scale factor, as has been done prior to ER7 (see LHO aLOG 18711). Specifically, we've tried to precisely measure the frequency dependence of the the famous z:p = (40:1.6) [Hz] filter just before the low-noise VCO (see LowNoiseVco, and D0900609). However, because the VCO (an MFC9119-10) is a non-linear actuator, it must be locked to a carrier frequency. We want the carrier to be what is nominally used to control the arms during ALS DIFF using the same Phase-Locking Loop (D1300812) and Frequency Difference Divider (see T1400317) to remain in the regime where we get the same amount of [Hz/ct] out of the PLL's control signal.

I attach a PDF of the entire system which is a copy of what was discussed in T1500383. Also attached are plots of the measurement.

The idea: 
- Lock the PLL to an independent frequency reference (a marconi in the CER) in place of the DIFF RFPD input to the Phase-Frequency discriminator. The IFR carrier is tuned to be of frequency roughly the nominal ALS DIFF frequency 157.84 [MHz], but refined further to make the H1:ALS-C_DIFF_PLL_CTRL_INMON as close to zero as possible. It's that PLL_CTRL signal that's used as an error signal for the ALS DIFF arm feedback when ALS DIFF is locked. Today, the carrier was tuned to 157.783 [MHz] to minimize PLL_CTRL. Again, this ensures that the [Hz/ct] of the DIFF_CTRL_INMON signal (or more precisely the VCO itself) remains in the linear regime exactly surrounding the carrier frequency we use for during a nominal ALS DIFF lock.
- Measure the PLL Open Loop Gain TF, using an SR785 connected to the PLL (whose inputs are in the back of the rack); Source -> EXC, Test2 -> Ch1A (Ch1B 50 [Ohm] terminated), Test1 -> Ch2A (Ch2B 50 [Ohm] terminated). Once we have the Open Loop Gain transfer function -- down to the very *very* low frequency of ~1 [Hz], then we can model the entire loop, extracting out all of the frequency dependence -- namely, the 40:1.6 Hz filter.

It turns out, measuring this OLGTF is hard and time consuming, given the extreme amount of gain the loop has at low frequency. In other words, in the nominal configuration, with a 55 [kHz] UGF loop and boosts, the PLL is *very* good at suppressing your 10 [Vpp], ~1-100 [Hz] excitation, so you have to drive at the limit of your analog driver, and integrate for a very long time. Indeed, the only way to get *any* coherence below ~1 [kHz] is to turn the boosts OFF.

As such, we took a ~2 [hr] long TF of the loop with boosts OFF, and then characterized the boosts independently.

Craig and I continue to model the results, but the GPIB templates for the measurements, the measurements themselves, and notes on the measurements live here:
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/PreER8/H1/Measurements/ALSDIFF/2015-08-09/
# notes
Notes_ALSdiffPLL_9Aug2015.txt

# templates
TFSR785_DiffBoostsOLGTF_10_100k_09Aug2015.yml
TFSR785_DiffPLLOLGTF_0p5_200_09Aug2015.yml
TFSR785_DiffPLLOLGTF_100_100k_09Aug2015.yml

# olgtfs
PLLOLGTF/TFSR785_09-08-2015_144001.txt   << High Freq, Boosted
PLLOLGTF/TFSR785_09-08-2015_144447.txt   << High Freq, No Boosts
PLLOLGTF/TFSR785_09-08-2015_155915.txt   << Low Freq, No Boosts

# boost TFs
PLLBoostTF/TFSR785_09-08-2015_190215.txt   << Boost 1, z:p = (2k:40) [Hz]
PLLBoostTF/TFSR785_09-08-2015_185858.txt   << Boost 2, z:p = (17k:2k) [Hz] 

As it stands, the UGF of the ALS DIFF PLL (in the nominal, boosted configuration) is 54.8 [kHz], with a phase margin of 48 [deg].

Many thanks to Jenne for her help today!

Jenne, Gabriele, Sheila

After the calibration work and before the Solomon Islands earthquake, we got a chance to try phasing refl 9 WFS.  The first of the attached screenshots show the phase before we started, and the second shows the phases now.  

We tuned them by injecting a line in the mode cleaner length at 11Hz, with the ASC on and 3 Watts of input power.  When we started the signal in I and Q was about equal, when we finished most of the quadrants had a factor of 3-4 more signal in I than Q.  REFL B quadrant 1 was strange, we weren't able to change the amplitude of the line, but the noise in the two quadrants was clearly changing as we rotated the phase.  

We then made a pitch excitation in CHARD and saw about 8 dB more signal in I than Q for both REFL A and B.  

We think these settings should be OK for relocking, because the IFO stayed locked while we were changing them.  We haven't tested this though because of the earthquake.  

J. Kissel, J. Betzweiser, D. Barker
WP: 5418
ECR: E1500332
II: 1091

I'll put in a more detailed entry describing all the changes once I've finished with the MEDM screen updates, but I've installed an updated CAL-CS front-end model as per all of the documentation mentioned above. This required a DAQ restart, which thankfully was much more successful than is has been in the recent past.

I've confirmed that all old CAL model, bare-essentials, functionality is up and running:
- Whitening filter recently installed for DELTAL_CTRL has been moved to DELTAL_CTRL_SUM, because the filter bank has changed name
- Turned on the newly named DARM_LINE oscillator at 37.3 [Hz], with an amplitude of 0.08 [ct] (I don't think this amplitude is right; I'll confirm the amplitude with Darkhan shortly, it hasn't been aLOGged).
- Filled in the new TM_OUTPUT_MTRX to pass through ETMY into DELTAL CTRL.

I can see that this functionality has returned, as Evan is able to get the IFO back to some power level, and the DELTAL ASD lies roughly on the reference.

Stay tuned for more detail!

I injected particulate by tapping on the beam tube at various locations with a scissors, imitating the taps that the cleaners make by accident. The acceleration measured on the beam tube for similar taps was around 0.1 g with a frequency peak at about 1000 Hz (Link). At each location I made the first tap at the top of the minute and made a tap at every multiple of 5 seconds for 1 or 2 minutes. My tapping uncertainty was about 1 second.

To observe the glitches in DARM I filtered the time series of H1:CAL-DELTA_RESIDUAL_DQ to be dominated by the 120-1000 Hz band, with violin modes notched. The table shows the time and the fraction of taps that made glitches. The distribution of glitch sizes is shown in the Figure. There were roughly the same number of glitches in each size decade.

In summary:

1) Glitches were produced from most regions of the beam tube.

2) Only about 20% of taps produced glitches

3) 9/252 taps produced multiple glitches 

4) Only 1 glitch of size comparable to the particulate glitches was observed more than 1s from a tap time in the entire 2 hour lock (DetChar may want to double check this). Thus the data suggest that there is not a reservoir of particles that are freed by the taps but fall later at an exponentially decreasing rate (so it is very unlikely that midnight glitches are particles freed by cleaning and cleaning is unlikely to have increased the background rate).

5) The figure shows that the number of glitches in each size decade was about the same, not increasing with smaller size. 

• quadmodelproduction-rev7652_ssmake4pv2eMB5f_fiber-rev3601_h1etmx-rev7641_released-2015-08-07.mat
• quadmodelproduction-rev7652_ssmake4pv2eMB5f_fiber-rev3601_h1etmy-rev7640_released-2015-08-07.mat

I can't find the posts now, but several months ago, an intermittent issue with ETMX was spotted that was narrowed down to the CPS's, possibly specfically the corner 2 cpses (?). This problem then somehow "fixed" itself and was quiet for months. As of the night of the 4th, it seems to be back, intermittently (first attached image, spectr should be pretty smooth around 1 hz, it's decidedly toothy). Looking at the Detchar pages, it shows up about 8 UTC and disappears sometime later. I took spectra from last night (second image) and everything was normal again.

Still don't know what this is. Anybody turn anything on Monday afternoon at EX that shouldn't be?

Based on measurements of the DARM OLTF and the EY PUM/test crossover that Jeff and I took last week, we can estimate the current value of the EY ESD actuation coefficient. It is 1.45×10⁻¹⁰ N/V², with a 20 % uncertainty. This is an 80 % increase compared to the previous value (0.8×10⁻¹⁰ N/V²) which was measured at the end of May.

This number mostly relies on the crossover measurement, since above 10 Hz, the effect in the OLTF of changing the actuation coefficient is largely the same as changing the optical gain. Additionally, this number requires us to assume a number for the PUM actuation coefficient. Here I assume that it has not changed since the May calibration (i.e., I use 7.0×10⁻¹³ m/ct at dc).

Note that the modeled crossover doesn't really agree well with the measurement above 80 Hz. More investigation is required, particularly since during ER7 we already knew there was an issue with the DARM model around 10 Hz. (This discrepancy is why I say the uncertainty in the coefficient is no better than 20 %.)

To generate this number, I took Jeff's ER7 calibration script and made a version (H1DARMXO.m) that models the crossover. Both scripts (and the parameters file for the July 25 measurement) live in the CalSVN under Runs/PreER8/H1/Scripts/DARMOLGTFs. All parameters were left the same as their ER7 values except for the optical gain (I use 1.0×10⁶ ct/m), the DARM pole (I use 330 Hz), and the EY L3 drive strength (I use 11×10⁻¹⁵ m/ct at dc). By tuning the L3 drive strength to match the measured crossover, we can extract the ESD actuation coefficient, assuming the rest of the L3 signal chain has been well-characterized. This is how I get the number quoted above.

The 80 % increase is sort of consistent with the 70 % increase that we saw when retuning the L3 digital gain post-vent. Strictly speaking, that was a measurement of the relative strengths of EX and EY. However, the DARM OLTF (with the retuned EY L3 gain) stayed roughly the constant before and after the vent, indicating that this 70% increase really is a change in EY.