[Sheila, Kiwamu, Matt, Jenne, etc]

We changed the TCS CO2 settings after we had thermalized at 20 W for a while, and were watching several metrics.  Here I'll talk about the frequency line at 900 Hz, and Sheila will append her OSA plots as a function of time.

I injected a line at 900 Hz into H1:LSC-EXTRA_AO_2_EXC, which goes to H1:LSC-REFL_SERVO_COMEXC.  I demodulated Refl 9 and Refl 45 like Stefan did last night (alog 29509), and also added another demodulator of OMC DCPDs.  For each of these, I ran a zservo to adjust the demod phase to keep the Q signal at zero. 

In the attached plot, bright red is the PSL power, and yellow and taupe are the X and Y TCS CO2 powers.  Purple, cyan and brick red are Q-phase signals, so can be ignored.  Green is REFL 9, blue is REFL 45. Orange is OMC DCPDs, indicating the coupling of frequency noise to DARM.  Note that the range for blue, green and orange are all symmetric about zero, so while it looks like the frequency coupling is decreasing, in fact it is increasing.  Sorry for a poor choice of demod phase.

After about 40 min at 20 W, the CO2 powers were stepped differentially.  X went from 0.2 W to 0 W, while Y went from 0 W to 0.2 W.  When this happens, you can see that the frequency coupling to DARM gets worse even faster than it had been while thermalizing with the usual TCS settings at 20W.  The REFL 45 and REFL 9 traces don't change in character when we alter the TCS settings.  Clearly this is the wrong direction for freq noise coupling, but it's nice to see that we can definitely affect it.  Sheila will post her results when her plots are ready, but it looks like the sideband imbalance gets worse when we made this TCS step, so it's good that everything hangs together.

Next lock, we'll try increasing the ITMX CO2, and leave the ITMY CO2 at 0 W.  This is a combination of common and differential, but it's all we can do before stepping the ring heaters later tonight.

Jenne, Chris Whittle

When exciting H1:SUS-ITMX_L3_LOCK_L_EXC using awggui for ongoing ITMX charge investigations, we observed an output voltage with a sinusoid offset from 0 (i.e. varying between 0 and 1k counts instead of +/-1k), despite having explicitly set offset to 0. This also resulted in a pervasive comb in DARM. We saw this at excitation frequencies 16 Hz and 16.55 Hz (no others were tested).

Closing and restarting awggui resolved the issue.

16:15 Chris S. moving rigging racks from highbay back into LVEA.

15:19 Karen to Optics lab

15:32 Fil to PSL rack isntalling ISS out of loop chasis

15:50 Karen out

          Gerado to MX

16:01 Richard to LVEA

10:05 Richard out

16:48 Karen to light bulb room and H2

16:45 Fil back

17:05 Fil+Richard pulling ISS chasis back in

17:15 John to LVEA

17:33 John out

17:53 Kyle to MY

18:07 Fil out

18:24 Kyle back

18:25 Keita+KAGRA crew out of LVEA (was there for ~1hr -- tour)

20:01 Fire drill. Fire alarm in the VEAs *might* have caused a lockloss. There were high frequency noise visible in DARM as soon as the alarm started prior to the lockloss. Will look more into this.

20:26 Karen to MY

21:31 Kyle back

21:50 Kyle leaving MY

22:51 KAGRA crew drive down to EX -- sightseeing(?)

Shortly after 1 P.M. local time, LHO held it's annual fire drill. Response was great, THANKS TO EVERYONE.

This was done at John's suggestion so as to reduce the risk of over pressurization of the LN2 inner vessel during dewar deliveries (Due to obstructed sensing line, the LN2 level for CP3 is determined by a manual setting of the fill valve which maintains the level adequately only for static conditions and must be adjusted as a function of dewar liquid height and vapor pressure)

following a lengthy summer break, and with ER10 approaching, the daily restart report is back. 

model restarts logged for Wed 07/Sep/2016

Per FAMIS #7070, Reset HAM4's HEPI L4C Accumulated WD Saturation Monitor (it was at 774 counts).  While clearing this Hugh was looking over my shoulder and noticed that HAM1 is missing from the medm screen (he put it on his "To Do" list).

Attached is a plot of IM4 Trans qpd and ISS 2nd Loop qpd signals.

First plot - top - shows that IM4 Trans Pitch and ISS 2nd Loop Pitch don't match well

First Plot - bottom - shows that IM4 Trans Pitch is a good match to the ISS 2nd Loop Yaw signal (yaw modified: multiplied by -0.7 and an added offset of 0.005)

Second Plot - top - shows the IM2 Trans Yaw and ISS 2nd Loop Pitch - raw data

Second Loop - bottom - shows the IM2 Trans Yaw and ISS 2nd Loop Pitch (pitch modified: multiplied by -0.3 and an added offset of 0.8)

The DCS Disk2Disk scripts at LHO, which copy data from CDS to the LDAS archive and scratch disks have been restarted to use the CDS h1fw1 framewriter as the primary source of frames. The backup is h1fw0. This will prevent LDAS from picking up "bad" h1fw0 frames, except in the very unlikely event h1fw1 is down and h1fw0 writes a bad frame at the same time. (See: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=29521 for the latest on the h1fw0 issue.)

Began 15:22 UTC, finished 15:24 UTC

As soon as the restart finished IPC was red. I hit diag reset button and it went away. OAF_L0_MADC1_EPICS_CH25 started to overflow pretty much as soon as the model restart was done.

TCS chillers and lasers are recovered.

The laser tripped this morning.  From the laser MEDM screen it looked like the NPRO had tripped which would pull
the entire system down.  However the Beckhoff screen indicates otherwise; that the fault is associated with the
crystal chiller.  It should be noted that the crystal chiller has 10468 hours on it.

    Logs indicate that it tripped around 3 am.  Unfortunately I did catch the trip.

    Further inspection shows that the laser tripped not because of the crystal chiller (see AMPFlow.png).

    Might be due to flushing of the newly deployed (old) manifold.

Sheila, Terra, Jamie

Today I set up an OSA on ISCT6 to look at sideband assymentry at the AS port.  Mark stayed late to get an MHV cable together,  and we were able to look at the asymmetry in some of the 50 Watt locks that Jenne and Stefan had.  Roughly, we saw that the asymmetry of the 45 MHz sidebands is 66% in power, while the 9 MHz sidebands are about a factor of 3 different in power.  We have left the set up in place for now, and we will make some plots tomorrow.

Keita Marc Fil Daniel

We realized that we can implement the required compensation for the second loop by using the whitened monitor signals (TP10) from the transimpedance board as the inputs to the sum of PD1-4 and PD5-8, respectively—instead of the unwhitened outputs from the transimpedance amplifiers.

The required modifications are:

1. Add a 220K resistor in parallel to C29 and C30 (4x channels on 2x boards)
   This limits the AC coupling and gives a DC gain around 1.
2. Replace C25 and C26 (4x channels on 2x boards) with 47 pF.
   This gives the signals a wider bandwidth.
3. Lift the input side of R48/R49/R51/R52 and jumper it to TP10 (4x channels on 2x boards)
   This rewires the inputs of the sum amplifiers.
4. Change R38 and R39 to 4.87K (from 4.53K).
   This brings the poles better in agreement with the ones form the second board.

I stopped and reran the Hartman code for ITMX at around 21:30 local.

Kiwamu, Nutsinee

A code is scheduled to run at 9 pm tonight. The code will power up CO2 to 1.3W and power it back down to 0W after 6 hours. Please do not touch ITM optics.

Last night, we ran a quick TCS test where we attempted to minimize the intensity noise coupling to the DCPDs by changing the CO2 differential heating.

It seems that the following CO2 setting gives a much better intensity noise coupling when the PSL power is 25 W:

• CO2X = 460 mW
• CO2Y = 0 W

This did not improve the recycling gain so much. It seems to have increased by 2% only.

According to a past measurement with a lower power PSL of 2 W (alog 26264), a good differential CO2 power had been found to be P_{co2x} - P_{co2y} = 270 mW (or probably less than 270 mW because I did not explore the lower differential power).

This could be an indication that ITMY has a larger absorption for the 1064 nm light such that the differential self-heating linearly changes as a function of the PSL power. We should confirm this hypothesis using the HWS signals.

[The test]

No second or third loops engaged, DC readout, no SRC1 ASC loop.

• 3:34 UTC, full resonance with 2 W PSL
• 4:12 UTC, PSL --> 25 W
• 4:24 UTC,  CO2Y 260 mW --> 0 mW
• 4:49 UTC, PSL --> 22 W for letting the 0.5 Hz instability go away
• 4:56 UTC, CO2X 480 mW --> 790 mW
• 5:12 UTC, lock loss

Drastic reduction of the intensity noise coupling was observed mostly between 4:24 and approximately 5:00, indicating that reducing the CO2Y power helped improved the coupling. After 5:00 UTC, we did not see a significant reduction. This may mean that we might have been already close to an optimum point where the coupling is minimized. The attached shows DARM spectra from various time during the test.

A broad peak at around 400 Hz is my intentional excitation to the first loop with band-passed gaussian noise in order to check the coupling to the DCPDs. As shown in the spectra, the reduction from the beginning to the end of the test is about a factor of 5. As reported in 27370, broad noise above 100 Hz up to several kHz is indeed intensity noise and therefore we see the noise floor in this frequency band decreasing too.

I reset the ITMY HWS magnification to 7.5x (it's set to 17.5x by default in the code).

aidan.brooks@opsws4:~$ caput H1:TCS-ITMY_HWS_MAGNIFICATION 7.5

Old : H1:TCS-ITMY_HWS_MAGNIFICATION  17.5

New : H1:TCS-ITMY_HWS_MAGNIFICATION  7.5

Alos, I had a quick look at the change in the spherical power measured by the ITMY HWS after the IFO lost lock this morning.

1. The measured change in defocus was, very roughly, 0.8 micro-diopters. (over about 40 minutes taken from immediately after 1141749205)
2. Around 95% of the lens forms/decays in this time. 
3. The magnification was set to 17.5 instead of 7.5, so we need to multiply the spherical power by (17.5/7.5)^2 = 5.44x
4. The steady-state, double-passed, lens measured by the HWS is then 8E-7/0.95*5.44 = 4.6E-6 diopters
5. The single-pass, steady-state, lens is then 2.3E-6 diopters
6. The single-pass, steady-state, lens gain (diopters per Watt absorbed) is 4.87E-4 D/W for self absorption
7. Therefore I calculate about 4.7mW absorbed power in ITMY
8. The arm power was around 11.9kW during this time
9. Hence, the absorption is (very roughly) 4E-7

This is a very rough calculation - and assumes that the HWS-Y beam is correctly aligned (we need to combine our evidence to really confirm this).

Nevertheless, I've set the ITMY absorption to 4E-7 in the simulation.

aidan.brooks@opsws4:~$ caput H1:TCS-SIM_ITMY_SURF_ABSORPTION 4E-7

Old : H1:TCS-SIM_ITMY_SURF_ABSORPTION 4e-09

New : H1:TCS-SIM_ITMY_SURF_ABSORPTION 4e-07

For comparison, ITMX absorption estimated to be 5.7E-7.