Yuta, Stefan, Kiwamu

This morning, we newly started using the BS M1 longitudinal actuator to make the PRMI lock more solid. This works well.

BS M1 stage feedback:

Our next target is to get the PRC length measurement done. In order to do that, we needed the PRMI locked for a sufficiently long time (more than 20 min). This morning, we found that the PRMI dropping the lock every 5-10 minutes. After some investgations, we found that the lock loss was due to the BS M2 actuator hitting the DAC range. There was a large motion in the Michelson over a time scale of  20 sec. So we decided to use the top mass of the BS to help the M2 stage actuator at the low frequencies.

The attached is the current-emperically-optmized top stage feedback. It seems helping the middle stage a lot at the low frequencies, resulting in a long PRMI stretch. As of now, it stayed locked for more than 30 minutes and is still locked. This feedback is implented in the guardian so that it automatically engages it when the PRMI becomes locked. We didn't measure the crossover frequency, though it should be around 0.1-ish Hz.

Limitter in PRM M2 stage:

We put a new feature in our lock acquisition sequence in which a limiter in PRM M2 stage limits the feedback when the interferometer is in the acquire state. It seemed that the most shaky optic was PRM during the lock acquisitoin. The limitter reduces the kick in PRM and hope this increases the chance to grab the PRMI fringe. We will see how this goes.

Schmitt trigger in guardian:

We implemented a Schmitt trigger in the LSC guardian so that now the unlocked and locked thresholds are different.

J. Kissel, J. Warner

Jim had reported in the morning install meeting that H1 SUS ETMY had tripped at ~12:30a PT last night after a few bands of transfer functions. Turns out the reaction chain (R0) had tripped alone, because its damping loops were OFF. I've ensured the loops are installed, and turned them ON.

So as to not interfere with the purple *ahem* PRCL team, I've misaligned H1 SUS ETMX.

    Aligned   Misaligned [urad]
P     7.3         200
Y    82.9         400

While Stefan reported that ETMX HEPI 'seems to have moved' in 10570, I show that it has in fact not.  The trend of the positions attached show rock steady position for the last three days.  There were two periods of HEPI trip where it of course was not in position.  These times are 4 March ~1320--1400 and 6 March 1600-1740pst.  I checked the IPS to Cartesian matrix values and they are unchanged.

Yuta and I noticed that there was a funny glitch frequently (maybe once a minute or so) in the PRX signal as well as the IMC transmitted power. It turned out that this was due the ISS keeping trying to acquire the locked loop with no success. According to a 2 days trend (see the attached), the diffraction power dropped quite rapidly yesterday and eventually plunged into a so small value that the ISS can not lock itself any more. Because of that, the ISS had been down from 22 pm local yesterday.
I increased the offset in the error signal (H1:PSL-ISS_REFSIGNAL) from -1.85 to -1.75. This brought the diffraction power back to the nominal of 10%. Now it seems running fine without a difficulties in locking it.

For the blue team:

Before I started the PRMI commissioning I switched off the WFS. I disabled the signals at the input side i.e. ALS-X_WFS_DOF_1(2)_P(Y)_INPUT.

The green light was locked on the 00 mode, although, as Keita wrote in his entry (alog 10571), the spot on the ISCT1 CCD monitor seemed a bit too low and shifted toward the right hand side on the monitor compared with the black circle on the monitor.

Because I wanted to maintain the same arm alignment, I manually offloaded the feedback to the OPTICALIGN biases of both ETMX and ITMX. Then I misalgiend ETMX by the guardian.

ALS COMM was even more noisy tonight than last night, and now it is not stable at all. This could be because of the increased seismic noise, or some other reason. 

The X arm guardian is working (there is no WFS control yet), I am leaving the arm locked with WFS on and no slow feedback to the ETM. It also seems like the COMM guardian is also working, but I'll need to test it sometime when the ALS COMM loop itself is working.

I started some excitations for Keita, screenshot attached.

Seems like the green transmission is not on the same spot as last night, maybe the TMS moved.

We had some difficulty engaging the WFS because the whitening gains were all reset to 0dB and white/awhite were mismatched and Lock path for the ITM was off.

After these were fixed the WFS started working, today the transmission power doesn't go to 850 cts, it stays 750-800. 

I'm leaving WFS on for the night, and when Sheila is done she'll start the excitation for the ITM and ETM.

[Keita Jeff Arnaud]

Several measurements were taken on ETMX for top mass length to test mass pitch decoupling as well as for the pum tf inversion (cf Keita's aLog), and are summarized in the attached plot.

Page 1 and 2 : Top mass to test mass TF compared with the "fiber" model, length to pitch (p1), pitch to pitch (p2)
Page 3 and 4 : Pum to test mass TF compared with the "fiber" model, pitch to pitch (p3), yaw to yaw (p4)

Points with an uncertainty lower than 10% have been removed from the transfer functions.The data for the length to pitch (2nd page) is a combination of a swept sine measurement, and a white noise measurement.

Measurements slightly differs from the model, especially for the top mass pitch to test mass pitch (p2), thas has its first pitch mode shifted down. It would be interesting to plot those measurements against the correction that is beeing made to the current model.

The data for the pum pitch to test mass pitch doesn't have any coherence below 0.6Hz, and those points have been deleted because of a low uncertainty, so it is currently hard to do a fit with the few points we have. I would like to try few more times tomorrow to do this TF again.

In the meanwhile, I will use Keita's happyVecfit function to do the top mass fitting, and calculate -L2P/P2P

Yuta, Kiwamu, Daniel, Sheila, Dave, Evan, Stefan

After we had the PRMI drive properly balanced (alog 10559), we fine-tuned the 3f-locking again:
- Added a 60Hz (triggered) notch in MICH to reduce the RMS drive to BS and PRM.
- AC-coupled the PR2 drive at 2Hz - it was saturating at DC.
- Reset the REFLAIR_B_RF27: two stages of whitening, 27dB of whitening gain, digital gain of 1.
- With that the 3f lock by itself was fairly stable - lock duration was limited only by user impatience.

Next we brought up the green arm - for some reason ETMX-HEPI seems to have moved - we had to re-align both TMS and ETMX suspensions.
- After manually tweaking the green arm alignment the COMM_handoff worked fine.
- We parked the about 12kHz avaiy from resonance and locked PRMI.

- PRMI locking im this configuration seemed more difficult. Attached is a plot of the control outputs once locked - we were again frequently saturating the BS and PRM. 

- Ignoring all that we switched to 3f-locking, and brought the red on resonance - it stayed locked....


....



... but we don't understand the red build-up. It's wasn't any higher than single shot.... something aint right quite yet, but I need a beer.


EDIT (after the beer): The build-up actually makes perfect sense: The reflectivity sign flip of the ITMX due to arm resonance means the Michelson is exactly anti-resonant, redirecting all the light to the dark port. effectively no light gets back to the PRM. Hence the incident power on ITMX is equal to the (PRM misaligned) single shot power.

We also had rockIFO playing the PRCL signal while we put the arm on resonance, and couldn’t hear any rumbling.

To do next: measure length sensing matrix in PRMI and in state 3 (which we should lock on red using the 1f-signal).

I've been updating the MEDM screens to be sure that all the BSC-ISIs currently used are consistent with eachothers.

Right now, BS, ITMX, ITMY & ETMX have:

- the Start, Tstart and Tcrappy blends installed respectively in blend banks 1, 2 and 3

- a working controller (lvl3 on ITMX & ITMY, lvl2 on BS & ETMX)

- tilt decoupling on ST1 for all them, except BS.

Putting on the controllers with Tcrappy blends on all DOFs for ST1 and ST2 provide a robust configuration with good performance on all these ISIs.

In other words, everything looks good into the seismic world!

There is of course some room for improvement. We're currently in an aggressive configuration, sensitive to varation of the input motion. Adding tilt decoupling on stage2 will help pushing the performance. I'll work on that as soon as I have access to a platform.

One more pair of WHAM4 HEPI Actuators attached--NE(corner 4.)  Sure and steady's the word.

The BIO chassis that controls the ISC Whitening was shifted over from H2 without having its IP addresses shifted over, so it couldn't communicate with the rest of the slow controls system. Since we like being able to use the slow controls to control things, I changed the IP addresses from the H2 10.80.xx.xx convention to the H1 10.40.xx.xx convention. 

J. Kissel

Following the same procedure outlined in LHO aLOGs 9453 and 9079, and similar to results from LHO aLOG 10493, with virtually the same demod parameters (only the amplitude was decreased from 1.25e5 to 1.2e5 [ct]) I balanced the coils on the UIM stage of H1 SUS ETMX. The final balanced gains in the L1_COILOUTF bank are
H1 SUS ETMX L1
Channel     Balanced COILOUTF Gain
 UL            -0.966
 LL            +1.004
 UR            +0.996
 LR            -1.034

The precision is still within +/- 0.5%; the ground motion while tuning the gains was not much better than yesterday, even though I tried several configurations of the ISI. See details of balanced vs. unbalanced signal SNR in comments below.

This balancing has reduced the L3 P and Y caused by a L1 pringle excitation at 4 [Hz] by
   DOF                  Reduction Factor @ 4.0 [Hz]
    P                          > 11.9      (peak below the noise, and totally incoherent)
    Y                          > 57.6      (peak below the noise, and totally incoherent)
The attachment shows the result from which these values were obtained, comparing the optical lever ASD at 4 [Hz] driven from L2 at the same amplitude for both balanced and unbalanced configurations.

Important note -- I found and was foiled by finding the L1_COILOUTF_UR gain sign set to
       Found   Expected
L1 UL    -        -
L1 LL    +        +
L1 UR    -        +
L1 LR    -        -
where expected comes from T1200015, and E1000617. Note these signs are exactly opposite from the PUM, because the UIM uses BOSEMs and the PUM uses AOSEMs, whose coils are wound in a different direction. Thus, the same magnet polarities are compensated by opposite signs.

I did a cursory check on the other three QUADs, and the same mistake is there too. This might just be a systematic, copy and paste error that we've propagated every where, and didn't notice until now because we haven't needed to use the UIM.