Sheila, Jeff, Thomas
We changed the H1:SUS-$(OPTIC)_ODC_CHANNEL_BITMASK from 1 to 0 for all the LOCK States for the following optics:
I have tarred up and compressed the h0 and h1 burt snapshots for Sep and Oct 2014, gaining us a whole 2% of disk space in /ligo.
Entry by Kyle.
Dewpoint of blow-down air measured -20C
Jim, Sebastien
We did a high resolution measurement on HAM3-ISI (bandwidth of 1mHz), with and without the sensor correction. At this point, we can say that:
- the feautre appears only when the sensor correction is ON
- it appears on all DOFs except RZ
- it's a very high Q 0.66Hz feature. This last point convinces us that it must be an electronic issue somehow.
I attached the plots and committed the DTT sessions of those measurements in the svn:
/ligo/svncommon/SeiSVN/seismic/HAM-ISI/H1/HAM3/Misc/HAM3_debug
/ligo/svncommon/SeiSVN/seismic/HAM-ISI/H1/HAM3/Misc/HAM3_debug-with_SC
We also checked that this feature was not due to a beating between the HEPI IPSs. We turned the position loops of HEPI HAM3 off. We even powered off the pier electronic boxes we no change: the peak is still here when the sensor correction is ON.
The investigation continues...
The door is going back on at BSC9 after having the door off for ~45 minutes.
This morning, the VE crew (Kyle, Gerardo, Bubba) held the BSC9 door open a few feet for me while I popped into the chamber and:
- Inspected the ETMx optic HR face with green flashlight - looked just as "dirty" as ~2weeks ago (lots of speckle), no obvious giant particles apparent.
- Inspected the test mass EQ stops. I found that the barrel ones were on the tighter side of the ~0.5-1mm gap setting, compared to the ERM ones which looked a tad on the looser side of the "spec". Face stops all looked good still. No stops were touching (we didn't expect to find any touching since the vent lifted the QUAD back up).
- Carefully unlocked the barrel stop nuts and adjusted the stops to be ~0.75-1.25mm for the top 4 stops and 1.25-1.75mm for the bottom 4 stops. Note, the way I gauged this was via the usual technique of "by eye". I tried to do the tap-optic-and-count-turns-of screw method on a few of them to confirm that my by-eye technique seemed calibrated. (On a 1/4-20 EQ stop screw 1.27mm of gap setting is acheived with 1 full turn of the screw, so I did 1 and a quarterish turn to get to ~1.5mm). It is impossible to use a tool on one of the top barrel stop screws (the top left), so I had to attempt to turn it a smidge with 1 finger. Carefully relocked the nuts.
- Inspected the optic HR again - still looked the same.
- Attempted to N2 dI blow (~10psi) to discharge/remove particulate - not alot of movement observed in ~1min.
- Removed tools, took a few pictures, exited chamber.
- Took quick V and P TFs - both looked healthy as expected. (ISI had to be redamped for this since I tripped it.)
- Door went on, pumpdown began, as per alogs.
Particle counts from the hand-held particla counter were 30 or under in all sized particles sampled before and after the door removal. I sampled at the door interface near the central bottom of the door opening.
The temperature at ENDX has been set to 68F. Hopefully we can keep it there. This is now the same as ENDY.
The plot shows 2 days of trend.
Evan, Alexa, Thomas
We repeated the Y arm loss measurement that we did yesterday in alog 15919. We followed the same steps and found: green TR buildup was 1.018, IR TR buildup was 11.2(0.5), Poff = 1303(5), and Pon = 1251(5). This gives a loss of 155(19)ppm, which is still suffeciently low, and within uncertainity of yesterday's measurement. This confirms that we are aligned to a good spot, and there is no need to adjust the green QPD offsets.
Just for reference: when we run the ditherAlign TMSY script the maximum normalized PD1, PD4 values are 1.38(0.05), 1.09(0.05) respectively.
Attached is a script which gives the algorithm for computing the loss. The uncertainties package is required.
Bubba is tied up with pulling a BSC door so I am posting a few photos for him.
Progress report on the DCS work:
Refrigeration piping continues, sheet metal work inside is almost done, and electrical work is well underway.
Covering for a sick operator in the morning and then Patrick will continue to help cover the rest of day.
Here are notes from the morning thus far
H1LSC has RED DAQ bit
Rich, Jim, Seb, Fabrice
We can only see this noise line when the sensor correction is ON, so we have been chaising it in the the sensor correction channels, but could not find anything.
We are back to noise hunting in the ISI channels.
- The first plot attached shows ASDs with sensor correction ON (2 nights ago). The amplitude of the peak is 2.5e-8 m/Hz^0.5
- The second plot shows ASDs with sensor correction OFF (last night). The amplitude is 8e-9 m/Hz^0.5. No visible noise line...
We are getting the ISI local sensors data on HAM2 and HAM3 with the sensor correction OFF, to perform signal subtraction, and see if the noise line could be burried in the seismic signal (and somehow amplified by the sensor correction?)
I did the subtraction between HAM2 and HAM3 ISI channels. I have attached the cartesian results for Z, which was the most interesting. The first plot attached is with sensor correction ON. The second plot attached is with sensor correction OFF. The residual with sensor correction OFF shows nothing at 0.66 Hz.
It might worth to have another look at the coherence between the output of the FIR filters of HAM2 and HAM3 (someone one site will have to do it, I can't access those remotely, thanks)
Evan, Alexa, Sheila
We went through the DRMI initial alignment today. We were able to run PRM_ALIGN fine. When we ran SRM_ALIGN we noticed that we were not feeding back to SR2 eventhough the asc wfs were designed to do so. This was something in guardian that was not properly updated. We fixed this problem, and also adjusted the guardian offloading script to clear history of the M1 locking filters since some of these now have integrators.
DRMI locked on 3f @ 12/06/2015 16:09:55 PST. We were able to engage all the ASC wfs loops except INP1, PRC1 which feedback to PRM. At this point we took transfer functions of each loop. We found that the PRCL UGF was low, and we had to increase the PRCL gain from 11 to 22. The MICH loop was comparable to previous measurement. Meanwhile the SRCL loop seemed to lose phase on the low frequency side of the phase bubble and be a bit flatter near the UGF. Comparing the times of the two SRCL transfer functions on conlog, it appears that the switch status for the SRCL filters has been changed. More invesitgation is required. We also noticed that the BS roll mode at 25 Hz had been rung up based on the DRMI spectrum, but not enough to disturb our lock.
After about 15 min we lost lock (most likely from an excitation). We could recover the lock; however, it only stayed locked when engaging the PR3 ASC wfs feedback this time; all other loops had to be turned off. DRMI was not staying locked for long periods of time, making it hard to take measurements. We took a BS oplev spectra and saw a peak at 19.6 Hz. The oplev damping has a large notch at 19.48 Hz. According to the SUS model awiki page it doesn't seem to correspond to a particular mode ... We are not totally sure if this is what is keeping us from locking.
Jim, Sebastien
We've been investigating a little more on the HAM3-ISI issue. Quick sum up: we see a 0.6Hz sharp peak on all DOFs when the Z sensor correction is on (see logs here and here).
First we checked the electronics. We swapped the STS input cables of the AA chassis between HAM2 and HAM3. This didn't do it, and the issue stayed on HAM3. This exclude the whole STS electronics chain except the AA chassis and ADC.
But, back in the December, the sensor correction was implement with a different seismometer (which means different AA chassis and different ADC), and the peak was already here. Thus we can say with confidence that it's not an electronics issue.
From there, couple of observations:
- The unity gain frequency of the nominal blend filter is 0.6Hz.
- When we switch from the nominal blend filter to a 750mHz blend, we don't see the peak anymore.
Given that, the nominal configuration of HAM3 is the same that the other ISIs, and the problem appears only on HAM3...
Also, by looking at the local transfer functions of HAM3, we see a lost of coherence around 0.6Hz (see files attached). Rubbing might explain the whole story... A soon as we have access to the platform, we'll do a driven transfer function in this bandwitdh and double check that hypothesis. In the meantime, we keep investigating on the blend configuration.
WIth Rick's help, we have created a composite image of ETMy before, after, and before-minus-after using Matlab. Due to saturation of the camera's photodetector in the 'after' photo (we believe due to higher power in the arm), the particles we removed during cleaning appear magenta. Tomorrow, I hope to do the same with the IR photos.
I think Travis meant to say "before photo" rather than "after photo." We suspect that the purple color comes from the fact that in the "before" photo the large scatterers were saturating the image at this exposure, as indicated by the bright white fields in the image. In the "after" photo, we subtract a fair amount of the green light due to the diffuse background scatter which is perhaps brighter due to the higher circulating power resulting from the reduction in losses. Removing most of the green leaves the red and blue for the saturated scatterers, rendering them purple.
Rick is correct, 'after' should be 'before'. I also meant that the appearance of more green light scattering in the 'after' photo is likely due to more arm buildup. Apologies for any confusion induced.
(Doug C and Suresh D.)
This afternoon we replaced the glitchy diode laser (Sl. No. 193) in the BS optical lever with a repaired and thermally stabilised laser (Sl. No. 130-1) which was under observation in HAM3 oplev. The attached plots show the improved performance due to the repairs and stabilisation.
Things to note:
1) Broadband noise injection into pitch has disappeared after swapping the lasers
2) Constant glitching and consequent broadband injection of noise into yaw signals has disappeared after swapping.
3) The RIN has dropped by an order of magnitude at all frequencies
4) The spectrum is stable and does not oscillate between stable and unstable regimes as the temperature in the LVEA changes due to the airconditioners.
Please note that the laser is still approaching a stable operating condition and is under observation for a futher 24 hrs. However its performance over the past six hours is satisfactory.
Distinguishing glitch and operator initiated actions in PIT and YAW signals:
We can distinguish the glitch and operator actions by looking at their spectral signatures. A glitch would cause a rise in spectral amplitude right across the entire frequency range. This would then appear as a white line running vertically (across all frequencies) in the spectrogram. Where as an operator initiated action would have a subsequent suspension damping motion at low frequencies (only).
We can see examples of both in the PIT spectrogram. There are no glitches in the red trace (the spectrogram for that is in bottom panel). This was after about 7PM and folks had already started using the BS oplev for damping. So their initial alignment efforts show up as small steps with an associated low frequency spectral signature.
The blue trace has the classic glitch related signals showing up in pitch. They can be seen starting at 1.3 hrs and going on till 1.4 hrs. I dont think anyone was using the IFO at that time. Since the BS oplev is used for local damping continuously, it is likely that the gliches kicked the optic and caused the activity we see around that time.
The picture is more messy in the case of YAW as we can see from the blue trace and its associated spectrogram (middle panel). The yaw signal seems to be continuously affected by the glitching however the event we saw in pitch at 1.3 hrs can also be seen in yaw. Once again there is no operator related activity in the blue trace while the red trace shows some steps which have an associated low frequency spectral signature (bottom panel). I concluded that they were associated with the initial alignment activity which was going on at that time.
I looked at whether the improvement in the laser quality has resulted in an actual improvement in the BS local damping. There is a tangible improvement in YAW.
1) The Spectrogram of YAW motion shows that the injection of broadband noise into the optic motion in YAW due to glitching has disappeared after the swapping of lasers
2) the Coherence between the witness channel and Oplev channel in YAW shows that we can now extend the servo bandwidth to about 10Hz reliably.
3) The spectrum of yaw motion dropped by a factor of two in the range 1 to 20 Hz. This probably has nothing to do with the laser per se. Probably the pier motion decreased between the two data segments.
Performance check after a week of operation
To see if the laser is still operating safely within the glitch free region, I checked the 1s trend over the past two days. The laser power has a slow drift of about 1% in a day. This is probably a LVEA average temperature related effect. The long term spectrum shows a 1/f shape down to 10^-4 Hz.
And to see the broad band noise I looked at raw signal over the past four hours (256 samples/sec)
The 4hr stretch of raw data spans a period when the oplevs were not used for first 1.4 hour stretch and then were turned on. We can see the suspension resonances damp in the witness channels.
The spectrograms show that there is broad band noise in the optic motion, but it is not due to the laser glitching.
The top panel shows the laser spectrogram and it does not show any broadband noise.
Conclusion:
The laser is performing well, without glitches. All the action we see in the Pitch and Yaw is associated with either human intervention or lock loss events which have kicked the optic.
After looking at the oplev spectra with the OL damping loops on and off, I turned down the yaw gain from 650 ct/ct to 500 ct/ct to reduce the amount of extra noise injected between 1 and 10 Hz. The pitch gain is still 300 ct/ct.
In the attached plot, blue is the spectrum without damping, and red is the spectrum with the new damping gain.
Added the changes to the safe.snap files in userapps, by hand, for the respective optics above. Also committted to SVN.