Evan, Rob

During a low noise lock last week we took some spectra to look for test mass mode frequencies. The test mass drumhead modes are clearly visible in the cross-power spectrum of the IOP channels of the DCPDs. The frequencies are at 8158.07, 8160.41, 8160.92, and 8162.68 Hz. These differ from the (modeled) values in the table in entry 20513 by ~0.5%.  We haven't yet worked out which frequency corresponds to which test mass.

The xml filename is in the screenshot.  

This is a small idea of measuring SRC gouy phase, following the recent ASC discussion (25999). 

The basic idea is that the propagation phase of an upper sideband HOM and a lower one moves in opposite direction, whereas the gouy phase goes in the same way. This will naturally lead to an unbalanced pair of sideband HOMs, whose ratio will be a function of gouy phase. By inverting this function, we can have a measure of gouy phase based on the ratio of sb. HOMs (which is independent of any absolute calibration).

We thus built a numerical simulation of DRMI only, with BS intentially misaligned. We computed the ratio of |E_usb|/|E_lsb| at the AS port as a function of SRC gouy phase, assuming a good prior knowledge of PRC gouy phase, cavity length, etc. The result was attched. It seemed that the |E_{+9M_10}| / |E_{-9M_10}| could be a good probe of gouy phase. 

We might want to do an OMC scan when the IFO was available, with DRMI locked. We could intentionally misalign BS (or the two ITMs) which would pump some +-9MHz 10 modes into the SRC cavity. With some clever stablization (e.g. using AS 18 as an error signal?), we could deduce the ratio of |E_{+9M_10}| / |E_{-9M_10}| from the OMC scan result. Comparing it with simulation, we could find out srcl gouy phase.

P.S. From the simulation we saw that the +-45M HOMs were pretty well balanced. However, this did not contradict with the observation of 25999, because the error signal for DC is <+45_10| +45_00> + <-45_10| -45_00>, and the error signal for 90 is <+45_10| -45_00> + <-45_10 | +45_00>.  Thus for the 90 MHz and DC seeing a different error signal, we only need the +/- 45 MHz 10 modes to have different phases relative to the +/- 45 MHz 00 modes. 

I've created a new filter for the RH substrate lens in TCS SIM. I'm testing it in H1:TCS-SIM_ETMY_SUB_DEFOCUS_RH. The filter bank is called "realRH". 

The poles and zeros are derived from a fit of a series of exponentials to HWS data for the measured RH spherical power at LLO. 

The (normalized) behaviour of the HWS measurement can be reproduced with the following sum:

defocus = -1 + sum(a_i * exp(-t/tau_i) )

Each exponential acts as a low-pass filter with a pole frequency of 1/(2*pi*tau), so the transfer function is the sum of each of these LPFs weighted by the coefficients a_i. Math then can convert that into a ZPK filter with 4 zeros and 5 poles and the desired response should ensue. That's what I'm testing at the moment: see H1:TCS-SIM_ETMY_SUB_DEFOCUS_RH_OUTPUT from 1141778267.

I think I've put the wrong sign in the filter bank ...

I moved the seismometer to a new hole, 20 m +Y of the EY station. I did this because I made an estimate that suggested that the wind was causing ground tilt through Bernoulli forces at the level of the tilt signal we were seeing from the buried seismometer (as judged by comparing Z, which is insensitive to tilt, to X and Y). I thought that these forces would be lower if the seismometer was up-wind of the building instead of beside the building where there was building induced turbulence. This 20m +Y location seems better than the 20m location +X of the building, and is generally a factor of 2 or more below the building seismometer in the tilt band below 0.1 Hz. All plots are a comparison of the buried seismometer to the SEI GND seismometer in the building. The red traces are the inside seismometer. The first plot is for an average of 14 MPH, the second for an average of 23 MPH. We havent had higher winds yet since I buried the seismometer. I believe that Jim is trying out the new blend filters on this buried seismometer.

Averaging Mass Centering channels for 10 [sec] ...

All STSs prrof masses that within healthy range (< 2.0 [V]). Great!

Details:
STS A DOF X/U = -0.054 [V]
STS A DOF Y/V = 0.494 [V]
STS A DOF Z/W = -0.385 [V]
STS B DOF X/U = 0.875 [V]
STS B DOF Y/V = 0.593 [V]
STS B DOF Z/W = 0.539 [V]
STS C DOF X/U = -0.198 [V]
STS C DOF Y/V = -0.642 [V]
STS C DOF Z/W = -0.98 [V]
STS EX DOF X/U = 0.5 [V]
STS EX DOF Y/V = -1.072 [V]
STS EX DOF Z/W = 0.4 [V]
STS EY DOF X/U = 0.521 [V]
STS EY DOF Y/V = 0.689 [V]
STS EY DOF Z/W = -0.26 [V]

Assessment complete.
 

Friday: ASC work and noise hunting

Saturday: LIGO discovery celebration

Next week:

• Grouting work on HEPI piers
• Manifold vent to install viewports for green camera
• Pump diagonal
• Cancelled: PSL high power work

Weeks 3/14 and 3/21: TCS optimization, ASC work and noise hunting

Week 4/4:

• PSL high power work
• HAM6 vent to install high QE DCPDs
• Install HAM6 GS13 and spring blade dampers

TITLE: 03/11 day Shift: 16:00-00:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: Cheryl
SHIFT SUMMARY:'
LOG:
17:00 Kiwamu has the IFO addressing OMC issues.
17:16 Jim and Robert to EX
17:50 Jim, Robert and Kyle back from EX
20:44 Fil to EX to check on/retrieve a cable
21:00 Fil leaving EX.
21:15 set IFO to sinle bounce mode for Sheila to troubleshoot OMC trouble
22:15 begin locking
00:02 Sheila called from LVEA to inform me that they'ere trying to get the OMC locked

Kyle, Chandra

Manually over-filled CP3 today, at 15:40 PST, in 5 min. 30 sec. 
Next fill is due Sunday, 3/13/2016.

To put Kyle's mind at rest, I ran a test on the cell phone texter system which simulated a CP8 alarm. To run the test I elevated the LOW alarm level from 80% to 99%. With CP8 at 92%, this raised a bogus alarm which we all received on our cell phones.

After an hour I concluded the test and put the LOW level back to 80%. While we are closely monitoring CP8, I have removed CP3 from this system as this is always in alarm. 

The crew has been able to clean 680 meters of Y-Arm beam tube including vacuuming and capping the support tubes in that same distance since Feb. 5th, some of which time was spent at LLO. The most recent stopping point is at HSW-1-041. 
Test results are posted here. 

As part of the VE control system upgrade at EX we had to redo the PI controller to maintain the level of the tank.  Though settings are not optimal they will certainly work with some small overshoot. Settings are Gain 6. Integral 360, Derivative 0.  ideally I would like to eliminate the overshoot but this system is so slow I want to let it run like this for a couple of days.  Will be good to see what happens Tuesday when the LN2 get delivered.

When we shook every chamber with external shakers, the BS chamber produced the most upconversion. The peaks produced by line injections have large side bands, suggestive of scattering (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=25132). Figure 1 shows photographs of things that might move in the light when the BS isolation shakes. These are pictures from the point of view of the beam spot on an ITM compensation plate or a beam spot on the BS itself. The ITM eliptical baffle is an obvious candidate. The baffle is mounted on stage 0 of the BS isolation. To test that it might be scattering, I shook stage 0 and stage 1 on Monday at two slightly different frequencies. The results in Figure 2 are consistent with scattering from something on stage 0, but not stage 1 or 2. I think we should B&K test the ITM elliptical baffles at LLO to get resonances for further testing of the hypothesis that we are seeing scattering from the ITM elliptical baffles.

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.

Jenne, Hang, Robert Ward, Stefan, Matt, Lisa

Today we spent some more time on ASC

1) We realized that ASB36 has the DC centering and SRM both orthogonal to the BS signal, so this is a better signal to be using for BS than 36A. We swithced to this, and also switched SRM to ASB36 I, since we saw that the error point was good for SRM in full lock when we have MICH controlled with ASB36 Q.  This loop is not insensitive to the centering (it is basically parallel), but we seem to be OK.  

2) 25999

3) We have the CHARD at high bandwidth in the guardian, although this is quite rough and we need to think about how to engage it more smoothly.  

4) We have measured several sensing matrices, Hang will post them.

5)We are able to engage the soft loops even when they all have ofsets of about 0.1, and they converge very slowly without bringing our buildups down, with all the rest of the ASC on.  We think this means that we don't (at least not any longer) have a problem with error points changing, but we might still have a problem with loops are cross coupled.  We have done this 3 times now. 

We are now having trouble with the OMC locking, it seems to be locking on the side of the fringe, even though the dither line is supressed.  We tried a bust restore (the computer was restarted today.) but that hasn't solved the problem.  We will come back to this tomorow. 

During O1 run we have monitored slow variations in the DARM actuation and sensing functions with several ~35 Hz and a ~350 Hz line at both observatories.

Systematics in the actuation function mostly affect systematic errors at frequencies below UGF, while systematics in the sensing mostly show up at higher frequencies.

Variation in the DARM sensing is parametrized with an overall sensing gain κ_C and a cavity pole frequency f_C. Most dramatic changes in both of these parameters appear in the beginning of locks, which could be a result of changing of cavity modes due to thermal heating of test masses and possibly some other effects.

Variation in the DARM actuation is parametrized with κ_TST and κ_PU. The κ_TST is a scalar gain factor of the ESD driver actuation which drives only the TST stage. We believe that it changes mostly due to charge accumulation on the surface of an ETM. The κ_PU is a scalar gain factor of the actuation functions of the upper stages PUM and UIM. The coil-drivers as used to for actuation of these stages. We do not believe that κ_PU should change over time, but monitoring it helps to make sure that we do not miss any slow variations that we did not account for.

Time-frequency plots of the known time-depedent systematics in the overall DARM response function calculated from κ_TST, κ_PU, κ_C and f_C in O1 run are attached.

Update: replaced figures (portrait -> landscape orientation) for convenience.