Brute Force coherence report is available here for last night lock:

https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_1115716006/

Some highlights, which I find very interesting:

• What's going on with CARM, why is there coherence of basically 1 below 20 Hz? (fig. 1)
• There is coherence at the same peaks, and a bit at all frequencies with AS_A_DC_SUM: is it intensity noise? (fig. 2) This seems to be confirmed by the coherence with IM4_TRANS and ISS signals (fig. 6)
• SRCL is still a good channel to have coherence below 80 Hz. (fig. 3)
• AS_A_RF_45_Q_PIT has large coherence below 20-30 Hz, maybe we are limited by angular noise? Do we need a better balacing or centering of the ETMs? (fig. 4)
• At 17 Hz there is a small bump/line that is coherent with HPI-HAM1_BLND_L4C_HP_IN1 (fig. 5)
• Coherence with the PSL periscope is much smaller than in the past (fig. 7). However, there is still some significant coherence with IMC WFS at 200-400 Hz (fig. 8), so we're probably still suffering of some contamination due to beam jitter

Not much is happening at higher frequency, at least for broad band coherence. However there are a lot of single frequency bins with significant coherence, and I can't list all of them here (I'm too lazy). So look into the table at your favorite line frequency, you might be rewarded with some coherence.

For historical reasons, the isolation loops that are installed on the BSC's were all quite different. I've been working on a consistent set of controllers for the ISI's and I've installed them on ETMX, ETMY and ITMX. I need to look in more detail at the BS, but ITMY needs to be redone, the filters in foton don't look anything like the ones Matlab says are installed, they look like Vincent's filters from several years ago.  The ones I've done for ITMX are the cleanest plots, so I'm posting the comparison plots, Old_ITMX_controllers and New_ITMX_controllers pdfs. The goal was to get the unboosted isolation loops as similar as possible, use the same boosts every where and hopefully get all o the chambers to similar performance. Generally this resulted in loops with 30-45 hz UGF, 17-20 degrees of phase margin and gain peaking of 4-5. I was aiming for as close to a gain of 10 at 10hz as I could get and gains of 1000 at 1 hz.

I spent a bit of time this morning clearing out remaining SDF diffs in SUS, LSC, and ASC.  This involved the usual alog hunt followed by some clarifications from commissioners.  Things still showing diffs at the moment and why:

- We need to capture a new snap file for the OMC due to yesterday's model change which will clear out it's large SDF diff list. 

- The ASCIMC still has one diff due to a 10e-17 size change in one value.  I think this feature is due for an upgrade at some point, so until then, this 1 diff will be lingering.

- Same with ISCEX - there are 2 diffs with very small diffs which won't go away with the accept button.  Will linger until update.

- We need some assistance with clearing the PSL diffs from team PSL.

- I've not paid much attention to the bottom monitors, namely ODC and CAL.

With a lock stretch of over 7.5 hrs at ~23.2W & a range of ~57Mpc, here is a picture of last night's lock stretch.  Just before 9am, H1 lost lock (no obvious reason, as we continued operating in an Undisturbed state),  the Intent Bit was taken to Commissioning, and Ellie started SRCL work. 

• SEI:  MICH Freeze measurement if allowed.  Only have one STS in LVEA. 
• SUS:  Nothing
• Facilities:  Hanging CR pics, cleaning outside window
• Vac:  Nothing
• PSL:  Nothing
• Outreach:  10-12:30 group of visitors
• CDS/Elec:  Rolling stuff in to H1 Room
• Visitors:  RichA, Steve V, Bob T, Peter F

Sheila, Evan, Stefan


- Reduced the whitening gain on both AS 36 ASC diodes. The new value is 24dB. We increase the input matrix values from 1 to 2 to compensate (for MICH and SRC1, i.e. the SRM loop).
- We tried to phase the AS_A_36 quadrants by wiggling SRM in yaw and pitch, maximizing the I signal. Not sure how meaningful that was though, because the actual signal we ended up using was Q.
- We switched the the sensor for SRC1_YAW (SRM) to 0.3*AS_A_36_Q + 0.3*AS_B_36I. This signal clearly reacted to our mysterious SRC cavity drifts, and had zero offset at the good locking point.
- We increased the power to 23W. This is the maximum power currently available. With this new SRM yaw sensor the 23W was very stable.
- The DARM offset was 14pm (or 1e-5 cts).
- This gave us a recycling gain of 38.
- Measured the open loop gain and verified the calibration.
- This configuration was stable for 1h.
- We took SRCL noise injections at: 8:46:15UTC and 8:59:40UTC (SRCL cut-off filter off and on)
- We took MICH noise injections at: 8:52:15UTC and 8:55:40UTC (SRCL cut-off filter on and off)
- Pushed the intent bit at 9:06:30 UTC.

- The inspiral range seems quite remarkably flat at 57 Mpc. A stron indication that we are now purley electronics noise limited at low frequencies.

To do tomorrow:
- Explore DARM offset: the new OMC code is ready to install, and will allow on-the-fly OMC offset tuning.
- Add the new ASC INMATRIX to Guardian.
- Add the new DARM offset to Guardian.
- Generate noise budget.

Tonight Dan went through some of the old violin mode damping settings, we have had all violin mode damping disabled for the past several weeks in the guardian since we improved the recycling gain.  Dan found that the old settings work for 6 of the modes, ITMY mode 3,5 and 6, ETMY mode 5, and ITMX mode 3 and 6. For ITMY mode 4 we need a sign flip in the gain.  All of the ones that Dan checked I put back into the gaurdian, some of which now have lower gain than before.  I also added ETMY roll mode damping back in the guardian.  

the remaining roll modes are at 13.89 and 13.98 Hz, but we don't know which is from ETMX and which is from ITMX

Elli, Nutsinee

The return SLED beam is now centered on the ITMX HWS. The QPD1 sum reads 1.71 (mean) and the QPD2 sum reads 1.32 (mean). Green light was resonates in both arms during the time of the measurement.

The current position of the HWSX lower periscope mirror is X: -286 Y: -927 and the current position of the HWSX upper periscope mirror is X: 300 Y: -300.

The Hartmann plate is off at the moment.

The move of the piezo mirror from the top of the periscope to the table top (Link) left large features in DARM at least in part because a resonance of the mirror mount that replaced the piezo mirror mount, overlapped with a higher frequency periscope peak, just as the lower frequency resonance of the piezo mounting had overlapped with a periscope peak at lower frequencies. Figure 1 shows, in red, periscope spectra before tuning, and, in blue, after tuning. The idea was to move the optic resonances, indicated by the high DARM coherence in red at 340 and 390 Hz, into the red valley centered at about 310 Hz by adding weight.  The blue trace shows that the peaks were moved to 310 and 340 and the coherence with DARM was reduced.

Figure 2 is an “after” photo showing the weight that was clamped to the mirror mount to make this change. In addition, figure 2 shows the safety cover, which covers the vertical path of the beam, that is responsible for the peak just below 300 Hz. Unlike the rest of the periscope, this safety cover is not damped and definitely needs to be - the safety cover resonance is showing up in DARM.

I also added a little weight to the top of the periscope to reduce coherence with DARM at 190 Hz by splitting overlapping resonances. This also helped.

I think that the next step is to minimize jitter coupling from the PSL table to DARM, possibly by injecting a peak using the PSL piezo and modifying alignment to minimize the height of this peak in the IM4 pitch and yaw signals and eventually by minimizing the injected peak height in DARM.