The laser was off this morning.  The chiller indicated that there was a "Flow sensor 1" error.

While the laser was down I mounted a B&K voice coil shaker on the +X, +Y corner of the table to study the PSL jitter contribution to DARM noise in the 80-200 Hz region. I doubt it will affect alighnment but be aware since it is quite heavy.

BP

Following Friday night's lock, I looked at the spectrum and saw some regular structure, looking like a 2Hz comb at odd frequencies.This looks like a new comb. [figs 1&2]

As followe up, I ran coherence with all of the EBAY magnetometers and saw strong coherence is some places with this 2Hz comb, as well as the persisting 0.5Hz comb (see plots below)

0.5Hz comb: https://ldas-jobs.ligo.caltech.edu/~brynley.pearlstone/comb_investigations/May_2016_comb/H1:PEM-EX_MAG_EBAY_SEIRACK_Z_DQ_25_40Hz.png

0.5Hz comb + 2Hz comb: https://ldas-jobs.ligo.caltech.edu/~brynley.pearlstone/comb_investigations/May_2016_comb/H1:PEM-EX_MAG_EBAY_SEIRACK_X_DQ_25_40Hz.png

Note: These two are the same magnetometer (MAG_EBAY_SEIRACK), looking at 2 different axes. Both combs were also seen in other magnetometers.

Full list of plots: https://ldas-jobs.ligo.caltech.edu/~brynley.pearlstone/comb_investigations/May_2016_comb/

Previous efforts to mitigate the 0.5Hz comb was focussed on powering the timing card independently in the CS EBAY LSC-C! I/O chassis which handles DARM. This has not worked to eliminate the comb. I can't report any reduction yet, as Friday's lock was not sensitive at low (<100Hz) frequencies.

This 2Hz comb on 1Hz offset is the transform of a 1Hz square wave. The 2Hz comb might have to do with the 0.5s and 1s structure seen it Keith's data folding studies here: https://alog.ligo-wa.caltech.edu/aLOG/index.php

Evan, Sheila

Today we blended CHARD P, with the same blend filters Craig and I used last night for yaw. This went smoothly and the attached screenshot shows the settings, which are accepted in SDF and shouldn't need to be in the guardian since they don't need to change.  WE haven't made it to low noise to see what kind of improvement this gives us.

We also had a look at dithering SRM and demodulating DARM control to get an alignment signal for SRM.  The SNR was not good for a 4Hz or 9 Hz dither, but for a 15 Hz dither there is clearly a signal, although the lock point was not good. I've added filters we could try to supress the length coupling in MICH2, SRCL2, PRCL2 filter banks, but we didn't get a chance to try this again.

Evan noticed that there is an instability in CHARD P at 0.2Hz when we tried to power up past 20 Watts or so last night, so we redisgned the boost that comes on at 17Watts to be gentler and have higher frequency zeros, (the new filter is MSBoost2 and in FM1).  With this we seems to be stable at 30Watts, at least for 5 minutes (we broke lock by trying to go to 35W). 

We had a bit of trouble with the laser today, nothing that can't be fixed easily ( noise eater and ISS oscialltions, difficulty locking the FSS).  Evan changed the temp search ramp parameters for the FSS. 

Attached are 7 day pitch, yaw, and sum trends for all active H1 optical levers.

State of H1: locked in Low Noise, with 68.4Mpc

Activities:

• EY chiller shut off, Bubba restored, temperature excurrsion was about 1.5F
• couldn't set the Guardian Intent Bit but the Observatory Mode did go to Observing, though long after H1was actually undisturbed
• 08:22:58UTC GRB arrived, I silenced, H1 was undisturbed before/after

Sheila, Craig, Cheryl

Tonight we are stable at 25 Watts, without the ISS 3rd loop on and no SRM control.  The range is just below 70 Mpc, and the spectrum seems non stationary with lots of loud glitches which aren't due to anything much that we have been doing.  

There is a broad peak around 60Hz, which is not something I've seen before, Craig found there is coherence with LSC signals there.  As expected we have a lot of noise from CHARD below 30 Hz.  We decided to try blending with the transmon QPDs.  We started with a simple blend, two poles at 4 Hz for the refl WFS and a complimentary filter for the QPDs.  This reduced the noise (and the coherence) but we still need to improve this a bit, probably with a .  We simply used the combination of TMS QPDs that is orthogonal to what we are using for the soft loops, so we might be able to find a combination that has better SNR for CHARD than what we are currently using.  Once the coherence with CHARD yaw was reduced we have more coherence with pit, so blending this will probably be one of our next jobs.  The current settings are in the screenshot.

The IFO has been basically undisturbed since 6:05 UTC, but we aren't easily able to hit the intent button, maybe because of old excitations...  

Evan, Kiwamu,

In this afternoon, we closed the ISS third loop which are meant to damp the arm power fluctuation.

We confirmed that it suppressed the common arm power fluctuation at around 0.5 Hz by 10 dB nominally. We tested this loop at various PSL power from 2 to 25 W. Further sophistication of the loop shape can be done if necessary.

[nominal settings]

• Hit the SECONDLOOP_CLOSED on the upper right in PSL_CUST_SECONDLOOP.adl
  • This enables the thrid loop signal to change the 1st loop error point
• Set the servo to the nominal setting as shown in the first attached.
  • Also the second attachment shows a measured open loop transfer function, but before adding FM4 which is designed to reduce the gain below 0.2 Hz by a factor of 0.25. By the way, we do not fully understand the behavior of the phase.
  • Probably the current ramping time of 10 sec is too long and can be shorten, but it helped reducing unnecessary kicks to the first loop.
• Open the third loop when changing the PSL power.
  • We had one incident where having the third loop engaged during the power up for some reason kicked the first loop enough that it eventually unlocked and the first loop and subsequently the interferometer.
  • Later, Evan found that the power normalization had an unnecessarily long ramping time of 3 sec. We reduced it to 0.5 sec. So maybe the situation is better now.

[injection point changed]

The original plan was to inject the third loop signal to either TRANSFER1 or 2 input. However it turned out that they have seem to have a factor of 10 attenuation, we ran into a range issue where the DAC output and SR560 (which is meant as a dewthitening filter) saturated before getting to the nominal servo gain. We instead moved the injection point to the one for the second loop by disconnecting the second loop and plugging the third loop cable.

Also, there is a low-pass-ish response somewhere in the second loop injection path which let us put a lead filter in FM3.

[Instability at 25 W]

With a 25 W PSL, we see an instability that occured at 0.24 Hz. Similarly to the usual arm power instability at 0.4 - 0.5 Hz, it modulated the arm power, but the frequency seems to be a bit low and it coupled to the HARD mode. This instability seems to happen regardless of whether the third loop is closed or not. A possible source might be an unstable ASC loop. Currently  under investigation.

I just received a call from Cheryl in the control room saying the chilled water pump at EY was in alarm. I looked at the screen and chilled water pump #1 had tripped. I started pump 2.

Richard changed PID settings on CP 5 & 6 today. Current settings:

CP5
Gain: 7
Integral: 460
Set Pt: 90

CP6
Gain: 6
Integral: 360
Set Pt: 88

Set points are set lower than nominal 92% so PID experiments can continue Monday.

1:30pm local

1/2 turn open on LLCV bypass --> took 33:17 min. to overfill CP3. 

Raised LLCV from 20% to 21%.

It looks like we need to do something about the triple coil drivers that we switch in lock, especially PRM M3.  We have lost lock a good fraction of the times that we have tried to switch in the last month or so.  Screenshot is attached, I also filed an FRS ticket hoping that someone might make an attempt to tune the delays while people are in the PSL tomorrow morning.  FRS ticket #5489 

C. Cahillane

I have generated corner plots of the time-dependent kappas to check their covariance.

There are six kappa values: 
1) Kappa_tst Mag
2) Kappa_tst Phase [Rads]
3) Kappa_pu Mag
4) Kappa_pu Phase [Rads]
5) Kappa_C
6) Cavity Pole F_CC

We do get some values of covariance that are comparable with variance... However, all values, including variance, are sub-percent.  
I anticipate that if propagated into the uncertainty budget, all covariant terms would be negligible.  We cannot be sure, however, without doing the work.

For the LLO Kappa Triangle Plots, please see LLO aLOG 26134