Keita, Elli
Continuing with Evan's and my attempts to lock the auxiliary laser or IOT2 to the PSL with a frequency offset in order to continue the PRC measurements started by Paul Fulda...
Today Keita and I got the auxiliary laser locked for periods of ~20s. Then PLL servo control signal would reach its maximum of 5V and the lock would drop. The beat note between the aux laser and the PSL was continually drifting in one direction- this may have been due to temperature instability on the table (the fan was off to start with and then I turned it on for a while when adjusting the Aux laser temperature.) I am watching
The PLL is controlled by an SR560 servo controller with 10Hz low-pass filter cutoff and 500 gain. A 7dBPm signal is demodulated with the beat signal between the PSL and the auxiliary laser for the error signal.
09:03 Vern to end X 09:07 Jim W. and Sebastian to LVEA to turn off HAM3 HEPI pier pods 09:14 Hugh craning in LVEA 09:26 Jim W. and I turned off sensor correction at end Y 09:31 Corey and Grant to the squeezer bay 09:37 Jeff B. and Andres to LVEA west bay to move 3IFO parts 09:43 Travis to end X 09:57 Hugh craning in LVEA 10:00 Jodi out of LVEA, reports clean room between HAM2/3 is on 10:03 Doors back on end X 10:39 Mitchel parking crane in LVEA 10:52 Hugh and Mitchel out of LVEA 10:57 Rick to end Y to work on photon calibrator 11:11 Sheila and Evan turned off clean room at HAM1 11:12 Manny done 11:19 Pepsi truck through gate 11:35 Jeff B. and Andres out of LVEA 11:48 Doug measuring distances for optical lever light pipes near HAM3/4 11:55 Kyle and Gerardo back from end X (started pumping) 12:52 Betsy putting parts in the cleaning bay 13:02 Filiberto to end X to look at cabling 13:04 Corey to squeezer bay 13:28 Aaron to end Y, PCAL cabling 13:51 Aaron done 14:40 Elli working on IOT2 Cyrus and I ran fsck on h1conlog3 Dave tested compilation of frontend models against RCG 2.9 In chamber work was completed at end X
Attached is a trend of the average LVEA temperature showing the daily ~0.2 deg C temp swing. The plot is for the month of August 2014 when we were finishing installation of the vertex. When we are vented and adjusting the EQ stops of a suspension we may see a ~0.06mm change in the gap of the EQ stops around the barrels of the PUM and Test Masses in the QUAD daily. (0.2degC change x ~0.3mm/1degC temp change = 0.06mm)
This is pretty negligible. Phew. However, this temp change pitches the suspension, so now I'll try to find out by how much. To be continued...
I performed a "make World" compile of all front end models. The following failed compilation:
All the failures are due to filtermodule-with-control parts with disconnected inputs (unused inputs must be grounded for RCG2.9). The compiler fails at the first error, more parts may need grounding.
ISI-HAM
part not grounded: HAMn_L4CINF_V1
file: isi/common/models/isihammaster.mdl
lho | r8122 not modified |
repo | r8876 14oct2014 Stuart |
llo | modified r8876 03nov2014 |
ISI-BSC
part not grounded: OPTICNAME_ST1_L4CINF_H1
file: isi/common/models/isi2stagemaster.mdl
lho | r8417 not modifed |
repo | r8875 14oct2014 Stuart |
llo | modified r8875 03nov2014 |
LSC
part not grounded: PSL_POWER_SCALE
file: lsc/common/models/lscpsl.mdl
lho | r8741 not modifed |
repo | r9038 03nov2014 Joe B |
llo | modified r9038 03nov2014 |
SUS
part not gounded: <RC>_M3_LOCK_L
file: sus/common/models/RC_MASTER.mdl
This file is unique to LHO, L1 still uses the MC_MASTER.mdl
J. Kissel, D. Barker I've grounded and committed the M3_LOCK banks RC_MASTER.mdl as requested, and committed the new version to userapps repo. Dave confirms that these now compile with RCG 2.9 as expected.
The sensor correction is installed and ON on all the chambers, but with a nominal matching gain of 1.
I made a small script to calculate the correct matching gain for X, Y, Z. The script works only for the HAM-ISIs for now, but it will be pretty easy to adapt. What it does:
- Grab the ground seismometer and GS13 data in X, Y, Z.
- Calculate the ASDs and calibrate them in m/rt(Hz).
- Calculate the GS13 over Ground ratio.
- Take the mean of the ratio for a [0.1Hz 0.4Hz] bandwidth.
Before running this process, the ISI needs to be in High blend mode (750mHz) on all DOFs with sensor correction OFF.
I've done this exercise for HAM4-ISI. The numbers seem a little small (Gain for X: 0.8784, gain for Y: 0.8702, gain for Z: 0.8574) but brings some improvement (see plot attached).
This has been done during the day, we might want to do it overnight for better tuning.
I'll do the other chambers ASAP. The script that I made is for now commited in the HAM4 folder of the svn:
/ligo/svncommon/SeiSVN/seismic/HAM-ISI/H1/HAM4/Misc/gain_matching_calculation.m
After some feedback, I rearranged the script and commited it into:
/ligo/svncommon/SeiSVN/seismic/HAM-ISI/Common/Misc/HAM_gain_matching_calculation.m
What it does now:
HAM_gain_matching_calculation(IFO,Chamber,start_time,duration)
. Grab the ground seismometer and GS13 data in X, Y, Z from start_time to start_time+duration.
. Calculate and plot the calibrated TF between Ground and GS13
. Take the mean of the amplitude for a [0.1Hz and 0.4Hz] bandwidth
Remember. before running this process, the ISI needs to be in High blend mode (750mHz) on all DOFs with sensor correction OFF.
I put HAM4, 5, 6 in this configuration last night and calculated the new matching gains.
HAM4 | HAM5 | HAM6 | |
X | 0.8730 | 0.9280 | 0.96 |
Y | 0.8619 | 0.9161 | 0.9496 |
Z | 0.8487 | 0.9604 | 1.0189 |
I'll put this new numbers in the MEDM screens in a minute.
So far so good. Attached is a plot of the EndX station temp (degC), pressure (torr), and suspension vertical sags (um). We're only at ~20Torr and falling but the suspensions in this chamber look to be sagging by the expected amount. No sharp changes in the shift to indicate poor health. The temp change that John made yesterday seems to be stabilized. We'll run TFs on the ETMx after the buoyancy effect has stabilized (almost complete now as shown in the ~100um drift down on the sus V trends, but we'll wait a bit longer to be sure).
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:
Added the changes to the safe.snap files in userapps, by hand, for the respective optics above. Also committted to SVN.
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.
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)
(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.
Today the frequency drift of the auxiliary laser was much slower, I was able to lock it the the PSL and sweep it across 2MHz a few times before the SR560 output railed. I moved the 1611 photodiode back a few cm to where the beam is more tightly focused, increasing the beat note power from -42dBm to -33dBm.
I will switch from using the SR560 to the New Focus LB1005 servo controller. I also plan to add an amplifier with gain 25 output voltage +/- 125 V after the LB1005, to increase the voltage driving the PZTs.
10Hz single pole, combined with a integration of PLL, means that the OLG phase is already -135deg at 10Hz, so the UGF could not possibly be much more than 10Hz.
But it easily acquires lock and stays locked until the output rails. Anyway this is just the first setting that worked while I was changing things non-systematically. Students will improve it to perfection.
As for the 5V output rail of SR560, using something else to go 10V would only be a marginal improvement as the drift is big. The frequency shifted by at least 200MHz while I was watching and it was not slowing down.
According to Evan, offloading to temperature was attempted without much success in the past, but it seems to me that it is still the way to go.
In preparation of allowing a larger offset frequency, I gave Elli a ZFM-2 that is a level 7 mixer for 1MHz to 1GHz.
We should have a New Focus/Newport LB1005 in the lab which is a proper PI controller for laser locking. We also should have +/-120V PZT driver for the JDSU NPROs.