I commented out the DC watchdog components in /opt/rtcds/userapps/release/cds/h1/alarmfiles/h1cds_iop_sus_watchdog_b123.alhConfig.

Getting alignment targets from end X and installing them on TMS at end Y.

Frame writer 1 daqd and nds1 daqd were restarted to read new daqdrc files to allow writing of raw minute files in the proper place, following moving of old files to a different file system.  

Jeff B. & Kate G.

A horizontal 4" witness plate (wafer) and horizontal 1" optic (S/N 1247) were placed near the center of the SEI table on Feb 5th. A vertical 1" optic (S/N 1245) was mounted on the HR side of SR2. A vertical wafer still needs to be set near SR2. 

Important notes: Witness samples were not placed immediately after the chamber was opened. Jeff did some cleaning before SR2 was installed and the wafers and optics were placed. Also, the 1" optics were removed from their PET G containers, put in PEEK holders, double bagged, and stuck in a bag with other tools before going in chamber. I didn't see obvious scratches in the First Contact, so hopefully the samples weren't damaged. 

Maybe Stefan turned these off, I didn't catch such in the alog.  I thought I left these in some Isolation state yesterday as Stefan wanted PRMI asap.

ITMY is damping with a Stage2 trip from GS13 limits.  The BS has no trip indicator but is damping only.

The HEPIs here are running normally.

Stefan and I found that the BS oplev was oscillating because of probably a loop instability. Disabling and enabling them at H1:SUS-BS_M2_OLDAMP_P(Y) made it stable again. It had been oscillating for more than 15 hours. The attached is the trend.

Stefan and I lowered the threshold value of the ref cav transmitted light because it was preventing FSS from a smooth recovery. It is now 0.4.

Stefan, Lisa, Kiwamu,

Our goal tonight was to lock PRMI with the 3f signals. However we didn't reach that point yet because of a (perhaps new) issue in the PRMI locking.

A good news is that the power build up was high because of the ring heater on ITMY which had been set at 4 W in total. POPAIR_B_RF18 went to 8000 counts.

40 Hz unidentified oscillation in PRMI signals:

After some tweak of alignment and gains, we managed to lock PRMI with the sidebands being resonant. However the PRMI lock was fragile for some reason. In particular, it lost the lock frequently when we changed the PRC gain. We took spectra of the signals and were surpprised by a huge peak in both PRC and MICH signals. This was causing a DAC saturation in the M2 stage of PRM which made the PRC loop unstable. This is something we didn't see before. We looked at some previous spectra from the last long stretch of 3rd of February (alog 9809) and confirmed that there was no such oscillation at that time. The attached shows spectrum of various signals from tonight. It is obvious that there is a broad and prominent oscillation at around 40 Hz in each signal. Note that when I took this data, I had a notch in PRM M2 stage to mitigate the saturation and that's why the PRM_M2 signal look a bit suppressed at around 30 Hz.

We tried to lower the UGF of PRCL, but the oscillation persisted. In fact the peak moves as we changes the UGF. For example, lowering the UGF also brings the peak frequency lower. We suspected a gain peaking and tried to move the UGF, but somehow the gain margin was so narrow that we could not move around so much. According to a quick swept sine measurement, the UGF was at around 40 Hz.. Another thing we suspected was a roll mode which is usually at around 40 Hz in the case of the small triple suspension. Since we failed to lower the UGF, we could not really try a notch technique to minimize unwanted excitation. We also looked at MC_F because we suspected the roll mode of MC2, but there was no visible oscillation at all. I also quickly tried the PRX locking to see if it still persists, but I didn't see any oscillation in PRX.

We are still unable to identify this oscillation.

Stefan, Lisa, Kiwamu,

The X arm is now quiter due to the oplev on ETMX and we are now becoming able to assess the noise performance.

Since Stefan got the oplev active loop running on ETMX and made the arm quitter, we wanted to measure the ALS infrared frequency noise by locking the PSL to the X arm using the green beatnote. The hand off process was very smooth tonight and we could try many times to bring the PSL frequency close to the arm resonance. Stefan engaged the additive offset path on top of the MCL feedback. We measured the UGF to be 3.6 kHz with a phase margin of about 64 deg.

It seems that the CARM noise is now suppressed to ~ a few 100 Hz which is unfortunately still greater than the arm linewidth of about 84 Hz. Because the fringe moved more than its linewidth, we could not confine it within the linear range. The below is a screenshot of the PDH signal in StripTool. You can see that the PDH signal, which in blue, goes back and forth around a resonance, resulting in a periodic funny shape. Also it looked like we need to have some more gain at low frequencies because we saw a low frequency excursion in the error signal.

Even though the PDH signal was pretty much out of the linear range, we calibrated REFLAIR_A_RF45 using Alexa's formula (see alog 7054) and tentatively made a noise spectrum which, of course, underestimated the actual noise due to a low optical gain. One thing we immediately noticed was that there is a 70 Hz broad peak which maybe a vibration of the periscope on ISCT1. It looks quite similar to what we had in HIFO-Y. We are not sure what this is at this point.

I finally got a script working to step the alignment offsets on the IMC mirrors and record the transmitted power drop with MC2trans and IM4trans QPDs. 

The idea behind this was to compare the quadratic function for power drop with misalignment with the theoretical function, giving us a means of accurately calibrating the alignment offsets.

The reason I'm interested in calibrating these offsets accurately is for beam jitter measurements using the coupling from jitter to RIN in transmission of a misaligned IMC [see e.g. LHO aLOG entry 8190]. The coupling factor is determined by the slope of the quadratic function, so we can't calibrate jitter measurements made in this way any better than we can calibrate the DC alignment offset.

The first attached plot shows the normalized transmitted power obtained for each individual mirror DOF, from both IM4trans QPD and MC2trans QPD, over "intended" alignment offset. Also included is a plot of the normalized transmitted power from a Finesse model of the IMC over "real" misalignment offset. From these plots we can see that in general the alignment offsets actually applied to the MC mirrors are larger than the intended alignment offsets. However, the measured data is not always symmetric (especially for IM4). This could be due to clipping at the QPDs. The centering on IM4trans is not as good as the centering on MC2trans, so I would be more confident in the numbers from MC2trans.

I fitted a quadratic function P=A(x-h)^2+k to each of the curves. The calibration is then done by scaling the alignment offsets applied to the actual suspensions by sqrt(Amodel/Adata). The second attached plot shows each DOF again, but this time with the x-axis scaled for the measured data to fit the model. I used the scaling factors calculated from MC2trans data since the centering on this QPD was better. For the most part I'd say the data matches the model well after this scaling.

These scaling factors are:

I would propose to include these scaling factors in the calibration of the MC mirror offsets.

The script can be run again at any time to check for any possible changes in e.g. the OSEM coil driver gains over time. It might be beneficial to take more data points at some point too, but the script takes 15mins or so to run as it is (mainly due to the time given for optics to settle between changes of offset). Another improvement would be to step MC1 and MC3 pitch over a larger range, since the transmitted power is actually fairly insensitive to these DOFs. Both these things can be edited in the top few lines of the script.

In case anyone is interested in running this script in future, it is located at opt/rtcds/userapps/release/ioo/h1/scripts/imc/pfulda/IMC_align_calibrate.py

Be sure to run the mcWFSrelieve script located in opt/rtcds/userapps/release/ioo/h1/scripts/imc/ first though!

I attach the analysis scripts here too, including the measured data, Finesse model and results, and other functions used.

Stefan, Lisa

Now that the mirrors move less and the arm cavity locks stably, we want to actually measure the frequency noise between the red and green.

When trying to do the green CARM hand off, we found that we didn't have a signal. 
We tracked it down to a bad alignment between the green beam from the SHG and the one from the arm.
We used Sheila's numbers  as reference: the beat note was supposed to be around 28 mV, it was just a few mV. We realigned the green arm beam on ISCT1, and we brought the beat note back to about 22 mV. 

Everyone


- ITMX motion has been largely reduced by the seismic teem, now the motion at 0.5 Hz is around 0.03 urad, A LOT less than before;

- The tuning of the ETMX is still in progress, but in the meantime Stefan implemented a 'dirty' optical lever feedback which reduced the ETMX PIT motion by about a factor of 5 at 0.5 Hz. With the OL feedback on, ETMX PIT @ 0.5 Hz is around 0.1 urad. There is some gain peaking around 1 Hz.

- In this state, the one arm is stably locked on green with 32 uW (calibration to be confirmed) in transmission (~840 counts in ALS-C-TRX_A_LF_OUT) power fluctuations are small, around 5%. We are not seeing the 01 coming into resonance, so we can make a measurement of the frequency noise red/green. (P.S.: Sheila says that ~800 counts is a good number, corresponding to a good cavity alignment.)