Working on ACB in West Bay.

She's heading there now. 

Alexa and I are going to the ISC racks near the PSL.  Also, I went to the X end for a few minutes.

Because in this after noon I happened to be around the ISC rack with an RF source in hand, I measured and adjusted the IQ balance of the 3f demodulator which had been refurnished recently. I did the same process as was done a month ago (see alog 9100).

Here are the new settings for it:

• H1:LSC-REFLAIR_B_RF27_PHASE_D  91.305
• H1:LSC-REFLAIR_B_RF135_PHASE_D 84.5045
• H1:LSC-REFLAIR_B_RF135_I_GAIN  0.99275
• H1:LSC-REFLAIR_B_RF135_Q_GAIN  1.00724

Note that I didn't change the gains for the RF27 I and Q paths because the gain difference was smaller than 1%.

Stefan, Yuta, Kiwamu,

We could lock the sideband-resonant PRMI for more than 8 minutes tonight. The angular fluctuation seemed better because of the L2P(Y) decoupling filters.

The locking is becoming reliable. We still need to investigate what causes the lock loss events.

Here are what we did:

• We changed the demodulation phase of POPAIR_B_RF by 180 deg such that it goes up when the sidebands are resonant.
  • H1:LSC-POPAIR_B_RF18_PHASE_R =  -100
• We decreased the whitening gains on REFLAIR_RF9 and RF45 to 0 dB to compensate the recent power increment.
• We reset the threshold for triggering. See the attached screenshot for the detail.
• We flipped the sign on the BS oplev gain because we had a sign flip in the coil gains recently (see alog 9415).
• We also flipped the sign of the output matrix for BS for the same reason.
  • H1:LSC-OUTPUT_MTRX_7_2    = 0.05
• The MICH servo gain was increased from 30 to 150
• The PRCL gain was also increased from -2 to -6. Plus FM9, +6dB, was engaged. FM3 is newly added as a triggered filter to give some more gains.
• REFLAIR_RF45_Q had a non-negligible RFAM. We had to add -200 counts in the MICH input to have a nice zero crossing. Note that the Q signal showed 1000 counts pp when it is unlocked..
• The PRCL UGF was measured to be about 35-ish Hz. See the attached.
• We didn't get a resonable-looking MICH OLTF for some reason. We may need PRM for the MICH actuator for better decoupling.

Tonight I found the ISI BS and ISI ITMY tripped.

When trying to put them pack to their previous operational mode (state 1 of ITMY, state 2 for BS), they repeatedly tripped. We decided to work without the two ISIs tonight.

Kiwamu, Stefan,

We did the PRM M3 pitch L2P decoupling tonight. We followed that same strategy as for the PR2 (alog 9584):
 - We paid the  most attention to the highest peaks in the L2P transfer function.
 - We fitted L2P and P2P independently to get good initial values for a fit of the ratio.
 - We had a harder time with the L2P (compared to the PR2) - in particular I couldn't get the phase at 1Hz right.
 - The result is only 

Plot 1:  transfer functions:
 - blue:   measured L2P TF
 - green:  measured P2P TF
 - red:    L2P/P2P (from measured data)
 - black:  fit (note that we paid more attention to the frequencies between 0.5Hz and 1Hz, because they matter most (see L2P)
 - Purple: fitted filter times measured P2P.

Plot 2: decoupling at 0.75Hz about a factor of 6 better.
Plot 3: decoupling at 0.95Hz about a factor of 4 better.

[Jeff, Paul]

I had a look through the calibrated length and frequency paths for the IMC (IMC-X and IMC-F respectively) to check that the calibration is still in order. A description of all the filters in the IMC-X and IMC-F paths can be found in Giacomo's entry 5945.

In fact, some things were amiss in the IMC_X path:

IMC-X_M1 path:

Filters that were engaged: to_m

Filters that are now engaged: dc_cal, wresg1, wresg2, to_m

MC2 M1 feedback is not currently engaged, so this may not matter right now. However, I've engaged the filters that calibrate the IMC-X_M1 signal to M3 motion. wresg1 and wresg2 model the suspension TF from M1 actuation to M3 actuation with the resg damping filters engaged (as they are currently). If and when M1 stage feedback is applied, the corresponding IMC-X channel should be calibrated now.

IMC-X_M2 path:

Filters that were engaged: dc_cal, white, sus_d1, sus_d2, to_m

Filters that are now engaged: dc_cal, wresg, to_m

The sus_d1 and sus_d2 filters are used to model the suspension TF without the resg filter in the M1 L damping path turned on. Because we are now using the resg damping I have switched the sus_d1 and sus_d2 filters off and engaged the wresg filter, which is used to model the suspension TF with the resg filter in the M1 L damping path. The white filter is a filter which was implemented in L1 in an attempt to avoid digitization noise above 50Hz (since the signal is so small there). I don't think we want to have this filter engaged, since it has to be accounted for later in data analysis, and I think we can ignore IMC_X so far above the L to F crossover. I've therefore disengaged this filter. This isn't the first time this one has come back to haunt us: see e.g 5311 or 5452.

IMC-X_M3 path:

Filters that were engaged: dc_cal, white, sus_d, to_m

Filters that are now engaged: dc_cal, wresg, to_m

Same story as for the M2 path.

I took a snapshot of all IMC-X filter banks.

IMC-F path:

Filters that were engaged: cts2V, InvGenFilt, VCO, FtoL

Filters that are now engaged: cts2V, InvGenFilt, VCO, FtoL

The only filter that changed since Giacomo's entry 5945 is the FtoL filter being engaged now instead of the tokHz filter. This means that the IMC_F signal is now calibrated in meters, presumably for ease of comparison with IMC_X. I checked the VCO gain filter: it is still the 536,604 Hz/V value, agreeing with Kiwamu's number from entry 5556 after accounting for the double pass of the AOM.

Arnaud, Sebastien

We've kept investigatiing on the 0.5Hz resonance issue that we've been having on ISI-ITMX (see first alog here). Reminder: we see a  peak at 0.5Hz on all the sensors of the ISI when it is controlled.

After more tests, we realized that this peak appears on all the sensors only when the T240s are in the blend (see plot attached).

Plus, by looking at the T240-X signal, you can clearly see this peak at 0.5Hz. It is even more obvious when the noise floor is reduced (ISI controlled).

Thus the issue seems to come from the T240s. We'll continue the investigation tomorrow and find which T240 is bad and how to fix it.

Jeff, Stefan

We did the PR2 M3 pitch L2P decoupling today.

Plot 1:  transfer functions:
 - blue:   measured L2P TF
 - green:  measured P2P TF
 - red:    L2P/P2P (from measured data)
 - black:  fit (note that we paid more attention to the frequencies below 1Hz, because they matter almost 2 orders of magnitude more (see L2P)
 - Purple: fitted filter times measured P2P.


Plot 2: 3e5cts drive to H1:SUS-PR2_M3_LOCK_L_EXC, first at 0.75Hz, then at 0.95Hz. At both frequecies we get about 1 order of magnitude suppression.

Still no resolutions to the problems with HAM4 ISI transfer functions. I took more DTT tf's today, and they all look a little better than the Matlab tf's. The attached plot shows the 3 vertical pods. The 3 thinner lines are the Matlab tf's (which, though not shown, have been repeated 3 times, all 3 times look pretty similar) and the 3 thicker lines (red, green and blue) are the same sensors with a DTT whitenoise tf.

T. Sadecki, B. Weaver

The now final (?) monolithic ETMy Quad has had both chains fully suspended.  Electronics were hooked up and troubleshot for all stages.  OLVs were taken for all stages and MEDM screens updated.  We are satisfied with the current alignment enough that we are ready for the first IAS rough alignment look tomorrow.  We have some rather gross yaw work to do on the main chain, but would like a preliminary look at the overall position on the table so we can take care of any gross, whole structure moves before continuing with finer alignments. 

(Sheila, Alexa)

We made a few measurements at EX under the following configuration:

PLL Servo Board

• Input 1 pol: NEG
• Input 1 gain: 0dB
• Comm Comp: ON
• Generic Filter: ON
• Fast Option: ON
• Fast gain: -8dB
• Boost 1: OFF
• rest off

PDH Servo Board

• Input 1 pol: POS
• Input  1 gain: -1dB (this was adjusted due to the new modulation depth change...we inserted a 12dB attenuator...see alog 9466. The optical gain must be adjusted accordingly)
• Boost 1: ON
• Comm Comp: ON
• rest off

1. PDH open loop transfer function (EX_PDH_OpenLoopTF_mag/phase.TXT)
2. To calculate the arm cavity length we zoomed in around the FSR resonance (~37MHz) and took the open loop TF (EX_PDH_OpenLoopTF_mag/phase_zoom.TXT). We found FSR ~ 37.752 kHz, which gives a crude estimate of L~3970.6m for the arm cavity length.
3. PDH error signal power spectrum (EX_PDH_Noise.TXT, EX_PDH_Noise_High.TXT, EX_PDH_Noise_Low.TXT). When plotting the power spectrum at full span we noticed a lot of variation in the measurement (we tried to collect the high and low spectrum in this variation). This variation is due to an unstable cavity lock which causes a variation in the optical gain.
4. PDH shot noise (EX_PDH_ShotNoise.TXT)

Sheila, Daniel, Stefan

I tuned up the beat note alignment this morning. 

With the arm locked we have 88uW total on the COMM_A_LF detector, 42uW from the arm and 47uW from the SHG.  This gives us a beatnote of 28mV pp, with the PFD RF power readback saying -35dBm. 

The Comm PLL locks for a few seconds and runs out of range (due to fluctuations at the microseism frequency).  One solution would be to feedback to the ETM  from the green laser at the microseim frequency ( right now we only have very low frequency feedback to HEPI), this would probably be nice in the end, because the PLL would lock nicely and we need to figure out out how to do this for HIFOXY anyway.  Another solution would be to engage COMM with the PLL partially locking, which does still give a useable error signal, which would be quicker to implement.