Betsy, Jeff, Ed, Sheila, Kiwamu, JimW, probably others

Because we wanted to reduce the opportunities for chaos tomorrow, we worked on making sure SDF's were clean at the end stations. This involved a lot of asking questions, head-scratching and saying "yeah, it's probably fine".  There are still a number of red tables for the corner station, such as windy blends on the CS BSC's and a bunch of LSC and ASC diffs, but the plan currently only includes restarting end station models.

Rediscovering why we fixed the large ion pump voltages at 7000V in the past -> Changed IP1-6 to 7000V fixed voltage

I have been working on putting together a power dudget for Hanford IFO. I have calulcated the power on the beamsplitter using abolute power on vaious photodiodes, and put this into a shot noise curve model.  I have compared this to shot curve is measured using DCPD null readout.The shot noise curve is taken from the GWinc model.  The parameter file I am using is attached.  These files are available in /ligo/home/eleanor.king/PowerBudget. 

I calculated the power on the beamsplitter using the TR QPDS  (TR_X/Y_QPD_A/B) to determine the power in the arms,  and using the POP sensors(POP_A_QPD, POP_B_QPD POP_A_LF).  The resuts are summarized in the table below.  There is a matlab script with my actual calculations in /ligo/home/eleanor.king/PowerBudget/PowerOnBS.  The recycling gain for the TR is larger than that measured with the POP_PDs.  If calibrate the POP_A PDs to a single shot, same result. I am assuming the TR QPDs are correct.  The resylsing gain calculated by the absolute powers on these PDs agrees with the recycling gain calculated by the relative power change before and after locking using both TR and POP photodiodes.

I have taken an average value of all of the TR QPDs, which is 41(+/-15%).  I have also included lines showing +/- 1 standard deviation in the plot of the shot noise curve.  The photodecetctor quantum effieciency is 85%, and the losses in the arms are 120ppm, measured alog 16579.  Next I plan get a better understanding of the mode matching numbers used for generating the shot noise curve.  (Mode matching into arms and mode matching into SRC, which is currently assume dto be perfect.)

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Additional Comments:

Propagation of arm power to recycling gain:

Assume losses in arms 0f 120ppm, alog 16579.

Recycling gain from power on the beamsplitter:

Pinput=IMC_input_power*0.88*Tprm.  (It is power on the beamsplitter that I am calculateing from the photodiodes and putting into the GWINC noise model.  But I find it easier to convert from this to recycling gain, and think in terms of recycling gain.

Some comments on the current photodiode calibrations:

POP LSC Photodiodes were calibrated by Kiwamu in alog 13905, based on the transimpedence of this photdiode.  [cnts/W] = 0.76 [A/W] x 200 [Ohm] x 2¹⁶ / 40 [cnts/V]

TR_QPDs and  POP_QPD calibrated using Dan's calibration alog 15432.  Note the whitening gain changes on these during full lock, so it is important to keep track of the multiple dewhitining filter banks.

The disk drive in control room computer opsws6 has died.  The computer was removed and will be taken in for service, a substitute has been installed in it's place.  The name of the substitute is lveaws2, so don't be surprised when you log in if it has a different name.  The opsws6 computer will be reinstalled when it has been repaired.

(Not Dan)

An accidental INDENTING change in the ISC_LOCK guardian affected a "return True" statement. Result:

- CARM_ON_TR returned true without actually ramping H1:LSC-REFL_SERVO_IN2GAIN to -32dB.
- This resulted in random lock losses later on in the lock sequence.
- This resulted in 6h of head scratching of the assembled commissioning team.

There is a long an ongoing discussion about the python indentation convention. No need to state which side the author of this log is on.

We've been stably locked with a recycling gain of 38 at 23.3 Watts for almost 2 hours (I intentionally broke the lock).   There were some of the slow (20 second) oscillations that cause some of our locklosses durring ER7.  

When I first came in I had some trouble with locklosses durring ENGAGE_ASC.  One problem was just a typo, the other one seems to be when the gain is increased for the SRC2 loop.  I think this caused the increase in POP90 we were seeing last night, which went away.  This morning it kept increasing until the lockl dropped. I moved the transmon QPD offsets back to the pre-vent offsets, powered up to 18 Watts, turned off the ITM loops and adjusted the ITMY alingments slightly to get a decent recycling gain.    The green alignment in the arm was OK here, and the camera positions not off by more than 4 counts so I did not update the references. 

The offsets where we are stable with recycling gain of 38 and 23.3 Watts are:  

Before ER7 we noticed that we have a better signal for damping the ETMX roll mode in AS 45Q yaw than in pitch. Durring the vent we added a matrix to the ASC model to allow switching.  On Friday Nic found that the old settings for damping ETMX roll (using AS45Q PIT) were not working, so he found some settings that worked using DARM err alog 19561.  

Today I needed to damp ETMX roll again, so I tried using AS45 Yaw, this worked well, with a phase of -90 degrees relative to the settings we had for pitch (so we use bp 13.9, -60degrees, -30 degrees, -100dB and a gain of 60).  I also attempted to damp ITMX and ETMY using AS 45 Yaw (which has better SNR for these as well).    

While these settings seemed to work for each individual optic, when I turned all three on and left them on simultaneously for several minutes, they rang up all the modes.  

Reminder, the nominal settings for bounce and roll damping (with AS pit) can be found in alog18614.  

We've tracked down a few settings which became wrong durring our down time.  

BS OpLev yaw limit was set to 0, so we were not using yaw damping while trying to acquired DRMI (it has been working OK).

ITMY violin mode damping for mode6 had the wrong filters engaged.  This rang up the mode, meaning that we had to reduce the whitening gain for the DCPDs.  Now that the right filters are engaged the mode is coming down.  I went through and made sure that the handfull of violin mode damping settings that were not monitored are.  We use guardian to set the gains for these filterbanks, but not to choose the switch status.  

Sheila, Evan, Stefan,
With information for Sheila on Sun morning

We tried to operate the ASC system at full power (24W), using two different sets of QPD offsets (I'll call them pre-vent and post-vent, see burt files below).

With the pre-vent offsets we
 - The ASC system was stable at full input power
 - We had a recycling gain of about 36. (Based on transmitted power.)
 - These QPD offsets are not compatible with the current initial alignment (i.e. the Guardian will drop lock during ENGAGE_ASC - however a slow 2-min offset ramp from post-vent to pre-vent, with 20dB lower gains on the ITM loops worked)

With the post-vent offsets we
 - Get a recycling gain of 40. (Based on transmitted power.)
 - These QPD offsets are compatible with the current initial alignment. The ENGAGE_ASC step works fine.
 - Assuming the higher recycling gain is real (and not due to a difference in QPD clipping), we'd like to keep those QPD offsets because of the higher recycling gain.
 - However we get a 0.41Hz oscillation which starts at about 20W or 21W.


About this 0.41Hz oscillation:
 - It shows up in arm build-up's as 0.41Hz modulation (i.e. 1-f).
 - It is CSOFT PITCH, i.e. all 4 test mass optical levers show it exactly in phase.
 - The arm powers are exactly out-of-phase with the optical level pitch signals, i.e. when all optics point downward (highest OL value), the arm power is at a minimum. (see plot)
 - 

To deal with this mode, we switched the ITM ASC loops for PITCH to the common/differential basis (i.e. DSOFT is now DITM, and CSOFT is now CITM). At the time of this elog we were still designing a filter to stabilize the oscillation.



========================================================================================
Pre-vent QPD offsets (in /ligo/home/evan.hall/Public/Burt/ItmQPDsPre.snap burt file):
H1:ASC-X_TR_A_PIT_OFFSET 1 -2.900000000000000e-02
H1:ASC-X_TR_B_PIT_OFFSET 1 -1.580000000000000e-01
H1:ASC-X_TR_A_YAW_OFFSET 1 -7.000000000000000e-03
H1:ASC-X_TR_B_YAW_OFFSET 1 1.050000000000000e-01
H1:ASC-Y_TR_A_PIT_OFFSET 1 1.010000000000000e-01
H1:ASC-Y_TR_B_PIT_OFFSET 1 -5.600000000000000e-02
H1:ASC-Y_TR_A_YAW_OFFSET 1 -1.270000000000000e-01
H1:ASC-Y_TR_B_YAW_OFFSET 1 5.500000000000000e-02

Post-vent QPD offsets (in /ligo/home/evan.hall/Public/Burt/ItmQPDsPost.snap burt file):
H1:ASC-X_TR_A_PIT_OFFSET 1 -4.800000000000000e-02
H1:ASC-X_TR_B_PIT_OFFSET 1 -1.480000000000000e-01
H1:ASC-X_TR_A_YAW_OFFSET 1 -4.000000000000000e-03
H1:ASC-X_TR_B_YAW_OFFSET 1 7.800000000000000e-02
H1:ASC-Y_TR_A_PIT_OFFSET 1 -1.180000000000000e-01
H1:ASC-Y_TR_B_PIT_OFFSET 1 -3.690000000000000e-01
H1:ASC-Y_TR_A_YAW_OFFSET 1 -2.420000000000000e-01
H1:ASC-Y_TR_B_YAW_OFFSET 1 -3.180000000000000e-01

Sheila, Evan

Bat control is among the most challenging of control problems. In this case, some patience and a cardboard box were all that was needed to solve the problem.

Evan, Stefan

When we came in the winds were relatively high, so we decided to take another loock at the AS_A_36 phasing. We did so in DRMI.

- To take out the effect of WFS centering and the otherASC loops, we lowered the total ASC gain by a factor 10, and increased the WFS centering gain from 1 to 200 (raising the centering gain by a factor of 20).
- We then drove the SRM at 0.3Hz in PIT and YAW.
- Interestingly PIT and YAW totaly disagree on the phase, by about 125deg...
- Attached are screen shots for the old phases (picture 1), phased for PIT (picture 2), and phased for YAW (picture 3)
- Additionally, while all 4 quadrants show a reasonable signal for PIT, the YAW signal is weak in quadrant 1 and not present in quadrant 2
- We decided to make a pragmatic choice:
  - For PIT AS_B_36_I is already a fine signal - only for YAW it doesn't work
  - Thus we decided to phase AS_A_36_I for YAW...
  - ... and only use quadrants 3 and 4 (the lower two quadrants).
  - Quadrants 3 & 4 also have a similar strength signal (with opposite sign) and similar RF offset (with the same sign)
  - So: this new YAW signal AS_A_36_I should be fine now.

YAW Input matrix for I and Q now is:
H1:ASC-AS_A_RF36_I_MTRX_2_1    0
H1:ASC-AS_A_RF36_I_MTRX_2_2    0
H1:ASC-AS_A_RF36_I_MTRX_2_3    -2
H1:ASC-AS_A_RF36_I_MTRX_2_4    2

With this new YAW sensor we updated the ASC sensing matrix (pictures 3 and 4).

This sensor seemed to do a good job at 17W and at 24W. However at 24W we still saw a 0.4Hz instability - see next alog.

We've noticed two more examples of epics channels freezing for a few seconds.  Yesterday (July 9 16:25:09 UTC) and tonight (0:22:49 UTC July 11)

Earlier today, I wrote a couple out of loop feedforward filters to the BS ISI foton file using Foton. When I hit the load coefficients button (while the ISI was isolated, the ff paths were off, so it shouldn't have done anything), the ISI tripped, hard. It rang up the T240's pretty bad and I couldn't isolate the ISI for several minutes after. Worried I had inadvertantly written some other filter I ran a diff on the most recent archived file and the file created yesterday when Jeff restarted the models. This showed a whole bunch of filter coefficient differences, which shouldn't have been there (as reported by a diff of the two archive files, I don't know exactly what changed, see attached). Talking to Jim, Dave and Jeff, it sounds like the glitch was probably caused by my having used Quack recently (June 22nd) to load some blend filters. Jeff's model restart (and even a prior model restart on June 30) simply inherited that quack-written file. Today was the first time the BS's foton file was opened and saved in Foton. Quack can apparently load coefficients with higher precision than Foton will accept, so when you open and save a "too high" precision filter with Foton, it rounds the coefficients off. Sudden change in precision of SOS coefficients in the blend filters = bad for isolation loops = bad trip.

We've seen this Foton vs. Quack Rounding problem before -- see e.g. https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=3553 -- and it's still biting us.

This sounds like a relatively easy thing to control for, I can think of two ways:

- getting Quack to check and do the rounding on it's own before writing to the Foton file.

- have the post-build script run a "foton -c" on all filter files before the model gets restarted.

Is there someone in the CDS group who can fix this? Maybe it has been? There are several versions of Quack running around, June was my first attempt with it, maybe I used the wrong one.

I used /ligo/svncommon/SeiSVN/seismic/Common/MatlabTools/autoquack.m

 https://svn.ligo.caltech.edu/svn/seismic/Common/MatlabTools/autoquack.m

Last Changed Author: brian.lantz@LIGO.ORG
Last Changed Rev: 7939
Last Changed Date: 2014-02-14 15:38:15 -0800 (Fri, 14 Feb 2014)
Text Last Updated: 2014-02-14 15:48:16 -0800 (Fri, 14 Feb 2014)

Evan, Kiwamu, Jenne, Stefan

- DRMI alignment is back to the old-good one: strategy: Used old slider values for everything but large optics. Tweaked SR3 (for instance) to get the beam spot centred on ASPD. Aligned PRX using PRM and PR2.
- DRMI ASC worked except PRC2 loop (didn't further investigate because we didn't care without the arms)
- Then we focused on MICH freeze:
  - We fine-tweaked the transfer function using a zpk([0.03],[0.054],1,"n")gain(0.555556) filter.
  - This made the gain roughly 1 below 0.1Hz. Plot 1 shows that - if measured coherently - we win up to a factor of 10 reduction at 0.01Hz. (Blue: no MICH freeze, red: MICH freeze)
  - In terms of RMS reduction (position) of the power spectrum, we gain a factor of 2, at the cost of significant noise injection at 8Hz. (Plot 2)

Interestingly, this RMS is now small enough that we spend most of the time in about 1/3 for the whole simple Michelson fringe. Unfortunately there is still slow drift, so parking at a "good" position isn't quite possible. But we are definitely in a regime where simple "fringe velocity" isn't a good parameter by itself. Fringe position must matter too. In our brief attempt to see locking performance changes we didn't notice anything significant though.

However, the next time we have high winds, we should definitely re-evaluate MICH freeze.

Calibration Team

Sign of h(t):

The gravitational wave strain h(t) is given by  h(t) = Delta L/L where Delta L  is is computed using

                         Delta L = ± (Lx - Ly)

The sign of Delta L can be determined using Pcal actuation on the test mass. Pcal only introduces a push force  so pcal readout signal (truly pcal excitation) is minimum when the testmass is away from the corner station (closer to pcal laser). From the first plot the phase between DARM/PCAL is ~ -180 degrees (DARM lags PCAL) which suggests that DARM signal from ETMX will be maximum when pcal is minimum (ETMX further away from corner station). Similarly, from second plot, since DARM and PCAL have a phase difference of ~-360 degrees (essentially 0 degrees), the  DARM signal from ETMY is minimum when the pcal is minimum. This shows that the sign convention for the Delta L is '+'

Time Delay between Pcal and DARM:

Also the slope of the curve gives the time delay between Pcal and DARM signal chain. The time delay is about 125±20 us. This time delay can be accounted for, within the uncertainity, from the difference in signal readout chain outlined in Figure 3 attached.

Refer to LLO alog #18406 for the detailed explanation behind this  conclusion.