Attached are TFs to the GS13s with the ISI damped and the OPO damped.  The higher number refs, the lower three of the six traces in the TFs, are the ones just run.  The low ref numbers are from March when it looks like the OPO or something else was not damped.  Today's TFs look cleaner around the 1hz area.

Prior to our big 2017-2018 vent we had a cage servo engaged to keep SR3 pitch at a hand-set OSEM value.  We have not been using this cage servo in the runup to O3, and I wanted to confirm that we shouldn't need it any more.  (Obviously we've been doing okay without it.)

In the attached plot, I show both the oplev and OSEM monitors of SR3 as well as the temperature of the corner station (nice and constant!) and our BNS range (calibration not certified good for all times, so this is just a rough figure of merit).  I think that these show that SR3 isn't moving too much, and we shouldn't worry about it too much.  In particular, we used to servo only pitch, since the concern was with wire heating, and pitch is even more constant than yaw. 

WP7954

Jenne, Jonathan, Dave:

Today I recompiled all the models with the old driver to ensure that the models compile without errors. We found some new input ports needed connecting on h1susmc[1,2,3], which was fixed by Jenne. A new, clean H1.ipc file was then created and all the models compiled with zero errors. I verified that the SHMEM channels used by h1psliss were not changed, so we should not need to restart PSL models tomorrow.

I have put back the original H1.ipc file (called archive/H1.ipc.19nov2018) in case we have to restart models overnight. We will complete the install first thing tomorrow.

I transitioned the LVEA back to laser safe after transitioning to hazard for a quick alignment fix in HAM6.  

the CO2 lasers are on since Thomas says he got approval from P King to leave them on in laser safe.  Added locks to the PSL light pipes.  

Ground loop checks for HAM1 and HAM6 are now complete. Not all issues were addressed either to limited access to chamber feedthroughs and cabling.

HAM1:
RM2 (Cable label ISC-229) Pin 13 shorted to ground

HAM6:
ZM1 (Cable label SUS_SQZ-20) Pin 2 shorted to ground
VOPO (Cable label SUS_SQZ-2) Pin 13 shorted to ground

F. Clara, C. Gray, K. Kawabe, R. McCarthy, M. Pirello, H. Radkins

TITLE: 11/19 Day Shift: 16:00-00:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
INCOMING OPERATOR: None
SHIFT SUMMARY:
LOG:

16:29 Peter out to the PSL enclosure

16:30 Keita and Georgia back

17:00 Vent meeting

17:44 Chris out to EY - retrieve swivel hook for forklift

18:00 Jason out to PSL

18:05 Hugh out to LVEA - HAM6 plug in ISI and damp

18:07 Chris back - headed out to LVEA

18:35 Richard out to LVEA - check on FIl doing gnd loop checks

18:39 Karen out to EY

18:40 Corey out to LVEA - HAM1 photos and witness wafer

19:01 Hugh has turrned on HAM6 ISI

19:30 Peter back

20:00 Jason Back

20:27 Jim doing measurements on HAM6

20:28 Jeff out to LVEA to get status on gnd loop checking

20:33 Jeff back

20:45 Everything tripped in HAM2 except HEPI and PRM

21:09 Richard out to LVEA - HAM1 area

21:13 Moved HAM2 to ISI_DAMPED_HEPI_OFFLINE

21:50 Corey and Hugh back

21:53 Peter out to the optics lab

22:04 Jason out to PSL

22:09 Terry and Nutsinee out to the PSL - Squeezer table

22:10 Richard out to LVEA

22:32 Fil and Richard out to HAM6

22:34 Cheryl out to the PSL

22:35 Corey out to HAM1

22:36 Corey out to HAM1

23:17 Chandra out to LOVE - valving in RGA on output tube

23:52 Marc, Richard, and Fil out

Added constant 1 to h1susmc2, as well as the M1 and M2 stages of HSTS_MASTER (which serves MC1 and MC3).  Also added 1s to the inputs of ZM1 and ZM2 in h1susopo, since they use the same HSSS_MASTER as the RMs and OMs.

Note that these models don't need restarting immediately with these changes, but when they are next built and restarted (which we're doing for an upcoming RCG upgrade) a DAQ restart will be required.

Pulled from LLO the MC_MASTER part, which they also use for their recycling cavities instead of RC_MASTER.  This is why I had to modify h1susmc2.

Also updated LLO's HSTS_MASTER (pulled the common part for them), and put in the constant 1 trigger overrides in l1susopo so they won't get errors next time they try to compile.

Introduction

The goal of this entry is to describe a method to characterize the non stationary of SRCL noise coupling to DARM, by identifying the coupling modulation. In the near future this should also provide a technique to do non-stationary noise subtraction.

Observations

When SRCL noise is injected and the SRCL feed-forward path is active, we see

1. DARM noise can be made to increase by a factor ~100 at all frequencies above 10 Hz
2. but the coherence between DARM and SRCL is very good only below 20 Hz. Above it averages to a level of 0.8-0.9, which is much lower than what you would expect given how much the SRCL noise is dominating DARM

In the plot below, the coherence is computed while SRCL noise was being injected.

The observations above seems to hint to some non-linear or non-stationary coupling of SRCL to DARM, especially at frequencies above 20-30 Hz

Algorithm

Past observations showed the SRCL coupling to be modulated by residual angular motion. To characterize this more precisely, I used the following algorithm:

1. assume the source of the noise is SRCL (LSC-SRCL_OUT_DQ to be precise) and that the modulation is slow and due to residual angular motion (ASC-*_INMON to be precise)
2. build a set of modulated noise signals, by multiplying SRCL with each of the angular signal independently (and by each of the ASC signal squared to include quadratic modulations). If s is the source SRCL noise, and a_i are the ASC signals, we build s_i = s a_i
3. we then build a linear combination of the modulated signals 
   
4. We can look for the optimal value of the alpha_i coefficients to maximize the coherence of this signal with DARM, or equivalently to minimize the power spectral density of the subtracted signal (DARM - x)
5. We can allow the coefficients alpha_i to be frequency dependent and complex, thus describing the transfer function from each modulated signal to DARM
6. A closed form solution can be found, making this approach fast to implement

Although the alpha_i are frequency dependent, they are not enough to describe any frequency dependency in the way the angular signals are affecting DARM. For example, if one of the angular signals modulates the coupling with a delay, or after the signal is passed through any time-domain filter, this algorithm will not model that. In other words, this algorithm is capable of finding and modeling things like DARM = TF[ SRCL * ASC_i] but not like DARM = SRCL * TF[ASC_i].

This algorithm is essentially equivalent to implementing an a-causal Wiener filter that uses as input the modulated signals s_i

Results

The two plots below shows the effectiveness of this algorithm. While the coherence of DARM with SRCL is relatively low during the noise injection, the coherence of the (optimally) modulated signal is high everywhere, as one would expect given the SNR of the noise injection. The second plot shows that if we subtract SRCL from DARM using a constant transfer function (i.e. DARM - TF * SRCL) we cannot get more than a factor ~10 subtraction. However, if we use the signal x that takes into account the modulation, we can get a much improved subtraction at all frequencies. For comparison the plot shows a typical level of DARM noise.

The algorithm work in frequency domain, so for each of the modulation channels (SRCL times a_i or a_i^2), we get a transfer function that determines how that couples into DARM. I don't have a way yet to rank the most important modulations, but simply looking at the amplitude of the transfer function gives an idea of which angular signals are the most important. The plot below shows the amplitude and phase of each transfer function. So the title of each panel gives you the source of the modulation (1 means no modulation) and the plot is actually the transfer function from SRCL times that modulation to DARM. 

The most important modulations are: DHARD_P, DHARD_Y followed by SRC1_P, MICH_P and PRC2_P

Next steps

This algorithm does not provide yet a way to build a time domain subtracted channel. To do that we have to convert the transfer functions to time domain filters.

1. one approach would be to just fit the TF obtained above, as we would do for a simple linear subtraction
2. one other approach would be to do the subtraction using FFT, which might be ok for off-line subtraction, but cannot be implemented online
3. the most interesting approach would be to extend te algorithm to fit directly IIR filters, instead of a frequency domain transfer function. 

I will try out (1) in the near future. (2) can be left as a fallback solution, since it's known to be working.

I have some plans to try (3), which is the most interesting of the three approaches. If working, it might also provide a way to directly gte IIR filters from the Wiener algorithm.

Finally, sooner or later, I will prepare a write-up of the algorithm for the DCC.

J. Kissel, after conferring with F. Clara, S. Dwyer, M. Pirello, D. Sigg, and J. Warner

Marc informs me that he and Fil have completed the standard checks for pins shorting between ground and chamber, and ground and any signal pins, aka "ground loop" checks on all SUS inside HAM6, and those tests have passed.
EDIT:  Some confusion betwen verbal communications. There are SUS that were not yet checked at the time of (previously) writing the aLOG.
There are some shorts that we're currently investigating delaying the closure of HAM6.

We've punted on checking any ISC sensors, namely
    - LSC OMC DCPDs
    - ASC OMC Input QPDs
    - ASC AS A & B WFS
    - ASC AS C QPD
    - SQZ Green & CLF rejected polarization PDs
because
    (a) Sheila & Co. did not touch (i.e. disconnect or reconnect, or move any cable routing)  any photodiode cables. 
    (b) If there were problems with these cables, we wouldn't be able to reach the feedthroughs and cable routing in order to fix them.
Sheila and Daniel sign off on this decision. The last time this chamber has been checked thoroughly was at the close-out of the Sep 2017-Jun 2018 vent; see LHO aLOG 41709, in which Keita found many ISC sensors shorted to the chamber, and fixed all of them.

We also punted (and always punt) on checking seismic sensors, because they "by design" intentionally grounded everything to the chamber inside, instead of at at the rack like ISC and SUS.

This makes "ground loop" checking in HAM6 complete.
Investigation on going.

Both chillers are still currently overfilled. No water was added. The logs were updated.

Dither alignment for soft loop:
======================

Instead of doing A2L decoupling repeatedly LLO does control the soft loops DC continuously using 8 dither lines between 7 and 9 Hz. That system seems to work well for them. LHO currently uses the end station QPDs, as well as effectively the POP QPD to fix the DC positions. While I have no indication that LHO's system is unreliable, I have noticed that S2L seems to change when we change arm power. So I would suggest just copying LLOs dither system - at least as independent diagnostics. WE can still decide whether or not we want to run with it continuously.

LSC DC DQ channel:
===============
H1:LSC-POP_A_LF_OUT_DQ H1:LSC-REFL_A_LF_OUT_DQ and H1:LSC-REFL_B_LF_OUT_DQ are currently only recorded at 2048Hz in Hanford. Those channels have interesting information  about intensity noise and RF sideband intensity noise at higher frequencies, and should be recorded at 16384Hz (that's what they are at LLO).

WP7954 Dolphin Upgrade.

In preparation for an upgrade, I am rebuilding the H1.ipc IPC Table File from scratch.

Please do not recompile or restart any models over the next 24 hours.

Bypass will expire:
Tue Nov 20 11:44:41 PST 2018
For channel(s):
    H0:VAC-LX_Y0_PT110_MOD1_PRESS_TORR
    H0:VAC-LY_X0_PT100B_PRESS_TORR

Ryan, Carlos, Jonathan

At 18:56 UTC today, while following up on a note from LLO aLOG #41844 , one of the processes on the core router responsible for maintaining connectivity with our Internet providers encountered a segmentation fault. Carlos and Jonathan were called and they connected to the console to debug with me. The routing process was restarted and reconnected to our providers at 19:10 UTC. I believe this is directly related to the connectivity issues that Keith logged Friday night / Saturday morning and am checking for updates that may be related to the routing process crash issue.

PeterK, RickS

Jason tweaked the alignment into the 70-W amp a bit late Friday afternoon.  It seemed that the pedestal in the 70-W output beam had been reduced and the beam didn't look too bad.

Today, we aligned into the PMC, adjusted the modematching lenses, adjusted the 70-W diode temperatures, and adjusted the pump currents.

We now have about 60 W (59.9 W) in transmission with about 10 W (9.7 W) reflected from the PMC.  This is about 86% visibility using the power monitors.  The visibility measured with the DC out of the RFPD (using the no-light level when the PD is blocked, about 14 mV) is (238-26)/238 = 89% (see attached scope image).  An improvement over what we had last week.

The ~60 W in transmission is close to what we need for O3.

The FSS is locked, but the ISS AOM is still removed from the beam path so the ISS is inoperable.

Sheila, Terry, Haocun, Daniel, Nutsinee

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

Summary: Dichroic flipped, measured some red losses (roughly 96% transmission from first dichroic to the bottom periscope on SQZT6), fixed the polarization issue (rotated in-vac half-waveplate by 7deg), aligned pump to OPO better (91% mode matched), and measured some distances from OM3 to AS_A and B. Ready for closeout ceremony

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

Details:

Dichroic flipped and red losses

We flipped the first dichroic BS that was mounted backward (alog45288) and corrected the beam translation with the first and second dichroic steering. That went well. After that we locked the OPO on duel resonance at non-nlg temperature (51.2C), then measured red power just after the first dichroic and just before the bottom periscope on SQZT6. We took two sets of measurement:

Each measurement has +-3uW uncertainty. Note that before we still have green reflected after the first dichroic we had to block seed and measured green so we can subtracted that out from the transmission calculation. Green didn't make it all the way to the periscope. We just took the average of the two transmission measurements and called it 95.7%

Fixed Polarization Issue

For quite some time we were not able to get rid of the wrong polarization of the OPO refl (green) with just a half waveplate and the beam splitter cube on the SQZT6 alone but was able to get it down to <1% with a combination of half and quarter (alog43443). So we concluded that whatever came out of the vacuum was not linearly polarized. We turned the in-vac half waveplate by 7 deg and that solved the problem. I think the wrong polarization is now <1% of the total reflected power when OPO is unlocked, it jumped up by ~50% (of the OPO unlocked, wrong polarization power) when the cavity is locked. I'll have to get these number later. But it's all better that it used to be.

Pump alignment

Better than ever. The new fiber works so far. The data here has been darknoise subtracted. 88% total mode matched (all visible peaks taken into account) with the misalignment (10 mode) being just 4% of the 00. The forth peak on the far right (0.04) is likely mode mismatched and I'm not sure what 0.024 was, higher order mode wrapped around? The 80MHz modulation was unplugged when the scan was taken so there's no sidebands here. The wrong polarization peak exists between the 3rd and the 4th peak and it's ~1% of the 00 mode (visible when you zoom way in on StripTool, barely visible here). We only knew it's there because the Hansch-coullaud locking signal was visible on the OPO refl rejected.

OM3 to AS_A, B distances

Here I posted the number I was given as Haocun and Sheila did the measurement. Yes it's a mix of inches and mm. I'll let the conversion up to the user.

Still need to dump the close-out photos from the SD card. Will post that later.

K. Kawabe, J. Kissel, G. Mansell, D. Sigg

We've achieved the following in HAM1 today:
    - Measured beam profile on LSC side (reflection side) of LSC/ASC REFL Beam Splitter (M6 on D1000313) down stream of the lens L1 (without LSC REFL A or LSC REFL B, or LSC A/B beam splitter in place)

    - Re-installed LSC REFL A/B beam splitter, and LSC REFL A PD 

    - Installed new LSC REFL B PD

    - Aligned beams on to LSC REFL A and B using LSC/ASC beam splitter, LSC A/B beam splitter

    - Aligned LSC REFL A and B PD such that their reflections are dumped appropriately

    - Verified the distances between LSC A/B beam splitter and each PD which we believe will result in a beam radius of ~240 um (details to be posted later)

    - WFS B beam dump black glass** has been replaced, as discussed in LHO aLOG 45279

    - We found that physical ASC REFL B was read out in the digital system as ASC REFL A (both DC and RF), and vice versa

    - Attempted to figure out what was wrong with ASC REFL A segment 4 DC, tried many things including various cable swaps, ended up reverting to the original configuration as we found it. DB25 for physical ASC REFL B (digital ASC REFL A) was not secured at all. This was reseated and secured. This somehow repaired the faulty segment, but we can't really identify exactly what fixed it.

    - We measured the laser power at various points in HAM1 with a dodgy OPHIR power meter:
        IMC_PWR_IN reports 250 mW.

        Inside HAM1, that same input beam as it flies through HAM1: 234 mW
        IFO REFL beam coming back into HAM1: 227 +/- 50 mW
        REFL AIR path: 4.1 +/- 0.5 mW
        In front of LSC REFL A: 1 +/- 0.5 mW
        In front of LSC REFL B: 0.87 +/- 0.5 mW

        LSC-REFL_A_LF_OUT16 reports 0.8 +/- 0.01 mW
        LSC-REFL_A_LF_OUT16 reports 0.735 +/- 0.01 mW

    - We checked all new components for being bolted to the table, and we cleared the table of all tools we used today.

**The existing black glass stock all appear to have water marks of some sort, so Keita took the best he could find, and used a pre-soaked wipe to clean off what fogginess he found.

We have left the IFO with both the main PSL input light pipe and the ALS light pipe shuttered.

What's left to be done:
- Verify that LSC REFL A and B's RF signals are functional (we only verified that DC signals are functional). Currently the cable that connects the TNC to 5-way coax piece is missing at the chamber feedthrough.
- The chamber-closeout ground loop check

Detailed blow-by-blow log is attached. Also attached are some relevant screen captures of the state of things after we'd finished with the IMC locked on 250 mW input power, the IMs, RMs, and PRM aligned, and with the REFL DC centering loops engaged.



Pictures, and plot of LSC REFL path beam radius evolution to come in a bit.

We finally got a chance to test a new "high vacuum" style 1600 l/s NEG pump, installed at only EY, on BSC6, at relatively high pressures after the BSC10 vent. At around 3e-5 Torr, I valved in the HV1600 (turned its built-in 10 l/s IP off first), shortly after having spun up the main 2000 l/s turbo pump. After three hours of pumping, I cycled valves in time series below, all while running the RGA in faraday mode. Times are local.

(turbo pump valved in at start)

1. 2:45p:  pressure = 3.4e-6 Torr; valved out NEG
2. 3:00p:  pressure = 3.6e-6 Torr; valved in NEG
3. 3:05p:  pressure = 3.4e-6 Torr; valved out turbo
4. 3:11p:  pressure = 6.9e-6 Torr; valved out NEG (both NEG & turbo valved out here)
5. 3:18p:  pressure = 1.0e-5 Torr; valved in NEG
6. 3:48p:  pressure = 1.2e-5 Torr: valved in turbo

Annotated pressure plots attached.

• PT-410 is cold cathode gauge
• PT-425 is hot cathode wide-range gauge*
• PT-428 is hot cathode wide-range gauge* on NEG housing

*these hot cathode wide-range gauges have a large offset and don't follow pressure readings from cold cathode gauges until it changes emission current at 5.6e-6 Torr

By itself, this NEG pump is not able to maintain the gas load, but does contribute to pumping in high vacuum region.

I haven't had a chance to look at partial pressures yet, but RGA scan is attached.