As part of checking the common mode board before we get too carried away with using it, I looked at the time series of the AO servo output when I turned on various boosts, or changed gain values. As it turns out, basically anything that I did caused glitches. Oooops.
I plugged a function generator to the IN1 port of the CM board, with a freq of 400Hz, and a voltage of 10mVpp (which is the smallest value that it would allow). I plugged the BNC version of the servo output into a 300MHz 'scope.
First I looked at "boost" and "super boost", and then I looked at various steps of the AO gain slider. For all of the button presses that gave me glitches, I saved .png's of the 'scope screen (on a floppy, so I'll have to fetch the data tomorrow...).
Both enabling, and disabling the "Boost" button gave me glitches.
For "Super Boost", I saw glitches for all of the steps, 0->1, 1->2, 2->3.
For the AO path, I only started at 0dB, and only captured screenshots of glitches when I increased the gain, since presumably that's when we'll care the most during acquisition. I found that going down in gain caused glitches at every step! For increasing the gain, steps from an odd number of dBs to an even number consistently caused glitches. Steps from an even number to an odd number occasionally caused glitches, but they weren't very common. For the steps that did cause glitches, some were worse than others (7dB to 8dB, 15 dB to 16 dB, and 23 dB to 24 dB seemed the worst.)
After my work, I put all of the cables back, so that we should be ready to utilize the CM board for locking this evening.
For posterity, here are the notes that I took while I was working - I'll make them more coherent when I fold them in with my images tomorrow. The "first .png, next, etc." are because the 'scope numbers them in order as a default.
1st png = boost enable, then disable
2nd png = super boost, start at 0, then 1, then 2, then 3
3rd png = AO gain from 1 to 0
4th is AO gain from 0 to 1 (happens less often than 1->0, which is every time I get a glitch)
Next is AO gain 1->2, got 2 glitches!
3->2 glitch often, 2->3 much less often
next is 2->3
next png is 3->4, 2 glitches with weird dip
next png is 5->6
6->7 is rare
next png is 7->8, which is nasty!!
8->9 is rare
10->11 is rare
png 11-> 12, 3 glitches
png 13->14, 2 glitches
png 15->16, kind of nasty
png 17->18, 2 glitches
png 19->20, 3 glitches
png 21->22, 2 glitches
png 23->24, kind of nasty
png 25->26, 2 glitches
png 27->28, 3 glitches, at least
png 29->30, 2 glitches
Somehow, the images got put into a whole new entry, even though I thought I was editing this one. Anyhow, please see elog 9938.
Green light power decreased from 3 mW to 1 mW at the ETMX-ISCT shutter. More later.
Note: I thought I was editing elog 9935, but somehow this became a whole new entry. Either way, all the info is in here.
The screenshot of the Boost enable / disable I'll have to re-take. Apparently I instead caught a screenshot of the list of files on the floppy...ooops.
This is a shot of enabling the Super Boosts. At the beginning, it's at "0", so no superboosts (also, regular boost was off). Then, I switch to "1", and the trace gets a little fuzzy. Then I switch to "2", and it gets very fuzzy. Then I switch to "3", and a lot of the fuzz goes away. There's a glitch at each transition.
The following screenshots are all of various steps of the AO gain slider. For all of these, both the "boost" and "super boosts" were off. Each screenshot is a single gain step, even if there are several glitches captured.
First, 0dB to 1dB:
Next, 1dB to 2dB:
2dB to 3dB:
3dB to 4dB:
While increasing the gain, I didn't find any more steps from an even to an odd number where I got a glitch. They would glitch when I undid that step (decreased the gain), but over ~5 trials for each increase, I didn't ever catch a glitch. The odd to even steps still had glitches while increasing the gain though.
5dB to 6dB:
7dB to 8dB:
9dB to 10dB:
11dB to 12dB:
13dB to 14dB:
15dB to 16dB:
17dB to 18dB:
19dB to 20dB:
21dB to 22dB:
23dB to 24dB:
25dB to 26dB:
27dB to 28dB:
29dB to 30dB:
It is actually very tricky to measure the green power at the output of the doubling crystal as the IR often leaks into the measurement.
I checked the green beam powers on the X/Y/PSL tables.
CONCLUSION: There is no green beam which exceeds 5mW anywhere in the 40m lab.
Note: The temperature of the doubling crystal at the X end was optimized to have maximum green power. It was 36.3degC and is now 36.7degC.
When the angles of the wave plates are optimized, we have 539mW input to the doubling crystal.
With the Xtal temperature of 36.7degC, where the green power is maximized, the power right after
the harmonic separator (H.S.) was 9.6mW.
Xtal temp 36.7degC ~~~
Xtal temp 36.7degC
If we believe these 4.69mW and 4.54mW are purely from the green, we have 4.8mW right after the H.S.
This corresponds to the conversion efficiency of 1.6%/W (cf. theretical number 2%/W)
By disabling the heating of the crystal, we can reduce the green light by factor of 60. But still the reading right after the H.S. was 5.3mW
Xtal temp 29.2degC ~~~
Xtal temp 29.2degC
Naively taking the difference, the green beam right after the H.S. is 4.4mW.
In either cases, the green power right after the oven is slightly less than 5mW.
When the angles of the wave plates are optimized, we have 287mW input to the doubling crystal.
With the Xtal temperature of 36.0degC, where the green power is maximized, the power right after
the harmonic separator (H.S.) was 0.86mW.
Xtal temp 36.0degC ~~~
Xtal temp 36.0degC
When the temperature was shifted to 39.2degC, the reading after the H.S. was 70uW. Therefore the contamination by the IR is small
in this setup and we can believe the above reading in 70uW accuracy. This 0.86mW corresponds to the conversion efficiency of 1.2%/W.
The incident IR is 80mW. We have 170uW after the H.S., which corresponds to the conversion efficiency of 2.6%/W. Maybe there is some IR contamination?
From the vacuum chamber total 1mW of green is derivered when both arms are locked and aligned.
Thus the total green power at the PSL table is less than 5mW.
I ran the ASS/ADS for the arms because the X-arm was way out. There was also some problem with its locking due to bad ramps in FM2. I copied over the filters from YARM and then adjusted some of the ramps and thresh trigs in the filter file until the transients in POX got smaller. Basically, you should not really be ramping on Integrators. Secondly, we should do some testing when adjusting the filter parameters.
I hooked up the 4395 to the MC servo board OUT2 so that we can monitor the error point when the PCDRIVE goes nuts.
Sanwiched wall as shown: 1" clear acrylic, 2 layers of 0.004" thick "window tint", 1 layer of 0.007" thermashield and 0.125" yellow acrylic
Visibility: 70 %, Transmission of 1064 nm 2-3 % at 0-50 degrees incident, power density ~ 0.7 W/mm2
Max power 100 mW
More details about this east end " acrylic + " enclosure ( optical table cover ) can be found elog entry 6210, 7194 and 7106
Window tinted layer transmission plot is below.
We have a film which may meet your requirements and the values are shown below:
Wavelength (nm) Transmission Reflectance(front) Reflectance (back)
1060 .0772 .604 .759
1070 .0723 .615 .772
These values are taken from the LBNL Optics 6 program and if you have access to that program, the NFRC ID for the film is 202. If you do not have access to the program, I have a captured the graph which may be of some help. I apologize for the appearance of the graph but someone at LBNL decided it would look better with a dark gray background – the yellow is the transmission curve, the blue is the reflectance (front) and the green is the reflectance (back).
The film is referred to as “Hilite 70” and has a 72% visible light transmission. These results were obtained with the film mounted on 1/8” clear glass.
Saint-Gobain Performance Plastics
Please consider your environmental responsibility before printing this email.
[Jenne, Rana, EricQ]
We tried a few times to engage the AO path while holding CARM on sqrtTrans and DARM on ALS, but failed every time. Since we cannot stably hold lock at arm powers of 1, even though we were able to do so early last week, we think that we have a problem (obviously). One noticeable thing is that while held with ALS, the Xarm transmission fluctuates almost full power.
As we were seeing late last week, the Xarm IR transmission while held with ALS was fluctuating wildly, whether we were locked on individual arms or on CARM/DARM.
Tonight we took some out of loop spectra, with different HEPA settings, to see how that affected things. It looks like HEPA at the nominal ~20% is okay, but anything higher than that starts to affect the Xarm beatnote sensing, while it mostly leaves the Yarm beatnote sensing okay. Perhaps this is something that isn't tightened enough in the Xarm path, or something on a skinny floppy mount that needs to be more secure.
I am still a little confused though, why we don't see large power fluctuations in *both* arms while using ALS to control CARM/DARM. Why are we not seeing this Xarm noise being fed back into the Yarm, through either the ETM via DARM, or common stuff via CARM actuating on MC2.
Note that the change at high frequency is because I switched from using non-DQ channels to DQ channels, so that's not anything to pay attention to. The noise reduction we see is below about 20Hz.
Rana pointed out that our POPDC level was very small. We don't have screens for them, but the DC PDs have the same analog whitening as the RF PD signals do. I changed C1:LSC-POPDC_WhiteGain.VAL from 0 to 11. Now our POPDC while locked on sidebands is about 8,000 counts.
We also swapped the cables between the SR785 and the CM board around. Now channel 2 of the 785 goes to TP2A, channel 1 goes to TP2B, and the source goes to EXCB. This is so that we can break the AO loop with the disable switch just after the slow/fast split, and look at the transfer function before we close the loop.
Late last night we were getting some problems with DAQD again. Turned out to be /frames getting full again.
I deleted a bunch of old frame files by hand around 3AM to be able to keep locking quickly and then also ran the wiper script (target/fb/wiper.pl).
controls@pianosa|fb> df -h; date
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 440G 9.7G 408G 3% /
none 7.9G 288K 7.9G 1% /dev
none 7.9G 464K 7.9G 1% /dev/shm
none 7.9G 144K 7.9G 1% /var/run
none 7.9G 0 7.9G 0% /var/lock
none 7.9G 0 7.9G 0% /lib/init/rw
none 440G 9.7G 408G 3% /var/lib/ureadahead/debugfs
linux1:/home/cds 1.8T 1.4T 325G 82% /cvs/cds
linux1:/ligo 71G 18G 50G 27% /ligo
1.8T 1.4T 325G 82% /opt/rtcds
fb:/frames 13T 12T 559G 96% /frames
1.8T 1.4T 325G 82% /users
Tue May 13 17:35:00 PDT 2014
Looking through the directories by hand it seems that the issue may be due to our FB MXstream instabilities. The wiper looks at the disk usage and tries to delete just enough files to keep us below 95% full for the next 24 hours. If, however, some of the channels are not being written because some front ends are not writing their DAQ channels to frames, then it will misestimate the disk size. In particular, if its currently writing small frames and then we restart the mxstream and the per frame file size goes back up to 80 MB, it can make the disk full.
For now, I have modified the wiper.pl script to try to stay below 93%. As you can see by the above output of 'df', it is already above 96% and it still has files to write until the next run of wiper.pl 7 hours from now at. at 6 AM.
IF we assume that its writing a 75MB file every 16 seconds, then it would write 405 GB of frames every day. There is 559 GB free right now so we are OK for now. With 405 GB of usage per day, we have a lookback of ~12TB/405GB ~ 29 days (ignoring the trend files).
Tonight was mostly cleaning up some scripts, including the re-writing the restore and align scripts for the optics.
The new script is in the same folder as the old one (/opt/rtcds/caltech/c1/medm/MISC/ifoalign/NewAlignSoft.py), but is not yet called from the align screen. However, I'm using it in the carm up and down scripts, and it works nicely for the PRM. I need to check that the offset value is okay for all the other optics (i.e. are they getting misaligned enough?), but then I'll have the new script called from the screen. The new script, per Rana's suggestion, does not touch the bias sliders. Rather, it puts an offset in the pitch filter banks in the coil driver output matrix-of-filter-banks. Then the misalign routine turns the offset on, and the restore routine turns the offset off. This way we have a nice ramp time, but don't have to do the weird calculation of number of steps to take as is done in the current script. Also, the "save" functionality will be obsolete, since we're never touching the bias sliders except for actual alignment needs.
I'm not sure what changed, other than the HEPA being on lower, but the Xarm ALS was much better behaved tonight. I was able to hang out around arm powers of ~1 for as long as I wanted.
I didn't try to hand over to digital REFLDC, but I was trying a few times to engage the AO path. With the CM board set to Plus, I hear hooting when MC IN2 is about 4dB. With the CM board set to Minus, I didn't hear hooting, but I lost lock when I went from 13dB to 14dB.
Also, I put the cables for the SR785 back to the "A" set of test points and excitation, so that I could take a closed loop transfer function. However, I don't know where the latest working scripts to make a remote measurement are, so maybe we can take some loop measurements tomorrow.
The carm_cm_up script is good (for tonight) up to the prompt "Press enter to indicate that it is okay to turn on MC2 LSC FM8". There are "read"s every step of the way, so it goes nice and slow, but it'll do everything for you except any last tweaks of the PRM alignment after the PRMI is locked.
It's starting to get a little crowded, but I modified the IFO_ALIGN screen to have new buttons to show the aligned / misaligned state of each optic. Koji made a good point, and I left the old restore script functional so that if the slider is moved significantly, we can always go back gently to the burt restored value. I have removed the old misalign function though, since we shouldn't ever be using that again.
I have redone the SPSR785 (spectrum measurement) and TFSR785 (TF measurement) commands in scripts/general/netgpibdata. This was mostly motivated by my frustration with typing out either a ton of command line arguments, or rooting around in the script itself; I'd rather just have a static file where I define the measurement, and can keep track of easier.
They currently take one argument: a parameter file where all the measurement details are specified. (i.e. IP address, frequencies, etc.) There are a few template files in the same directory that they use as default. (Such as TFSR785template.yml)
If you call the functions with the option '--template', it will copy a template file into your working directory for you to modify as you wish. "SPSR785 -h" gives you some information as well (currently minimal, but I'll be adding more)
In the parameter file, you can also ask for the data to be plotted (and saved as pdf) when the measurement is finished. In SPSR785, and soon TFSR785, you can specify a directory where the script will look for reference traces to plot along with the results, presuming they were taken with the same measurement parameters and have the same filename stem.
I've tested both on Pianosa, and they seem to work as expected.
Comments, criticism, and requests are very welcome.
(P.S. all the random measurement files and plots that were in netgpibdata are now in netgpibdata/junk. I feel like this isn't really a good place to be keeping data. Old versions of the scripts I changed are in netgpibdata/oldScripts)
Script seems to be working now:
nodus:~>df -h | grep frames
fb:/frames 13T 12T 931G 93% /frames
I tried many times this evening to engage the AO path, with limited success.
Q's new scripts worked really well, and so I have some transfer functions! To take these measurements, in ...../scripts/general/netgpib, I am running ./TFSR785 TFSR785_CARMloop_May2014.yml, where the file name is the name of my parameter file. The data, and the saved pdfs, are in /users/jenne/PRFPMI/CARM_loop_measurements/2014May14/ . For these measurements, the SR785 is hooked up to the "A" set of excitation and test points on the CM board.
All of these traces were taken while the IFO was PRFPMI, with PRCL and MICH on REFL33, DARM on ALS diff, and CARM on InvSqrtTrans. carm_cm_up.sh is up to date, through the echo "REFL_I should now be zero" (~line 111 in the script). All you need to do is set the beatnotes, and then run the script. Follow instructions in the prompt (such as "press enter to confirm PRMI is locked").
Here are my notes for the various times:
23:01:44 - MC IN2 = 0dB, CARM gain = 5.0
23:13:45 - MC IN2 = 10dB, CARM gain = 5
23:26:10 - MC IN2 = 6dB, CARM gain = 10 (after Q suggested increasing overall gain, rather than just AO path)
00:13:07 - MC IN2 = 6dB?, CARM = 6ish? don't remember exactly.
00:45:00ish, Realigned IFO using IR with arms.
01:03:17 - MC In2 = 0dB, CARM gain = 5
01:07:42 - MC IN2 = 8dB, CARM gain = 6.295 (AO went up to 6dB, then +1dB steps to both simultaneously using ezcastep C1:LSC-CARM_GAIN 1dB C1:IOO-MC_AO_GAIN 1)
ezcastep C1:LSC-CARM_GAIN 1dB C1:IOO-MC_AO_GAIN 1
01:08:57 - MC IN2 = 10dB, CARM gain = 7.92447
01:10:08 - MC IN2 = 12dB, CARM gain = 9.97631
lockloss when trying to add 1 more dB to both.
01:41:36 - MC IN2 = 12dB, CARM gain = 9.97
lockloss when just MC IN2 up by 1dB, left CARM gain alone.
The 60Hz noise in TRY is back. Since I thought I remembered someone suggesting that it was leakage light from the exit sign, Koji went in and wrapped the end table in foil, however the lines are still present.
In addition to a transparent legend, we need the corresponding CM crossover measurements from DTT to compare with the Q-Mist-Loop model results. The xover tells us when the AO gain is high enough so that they can be ramped up together.
Also, I wonder how much power fluctuation we get from the large ALS DIFF noise and if that demands we get the TR signals normalized by POPDC.
Our only seismometer is at the east end now.
Atm1, Ditch Day morning puzzle. The gardener came after the freshman did leave and cut the grass with the lawn mower.
Atm2, Yesterday afternoon the Aztecs containers moved out.
It's taken a lot of trial and error, but I've found a path through MATLAB loops that seems like it may be stable at all points.
CAVEAT: This doesn't give any indication as to why we weren't able to turn up the AO gain more last night, as far as I can tell, so it's not all good news.
However, it's still ok to at least have a plan that works in simulation...
Based on the location of the optical resonance peak in the CARM plant, we estimate our CARM offset to be 200pm. I haven't simulated TFs there exactly, but do have 100pm and 300pm TFs. This procedure works in MATLAB starting at either, though 100pm is a little nicer than 300. MATLAB data and code is attached in a zip.
The steps below correspond to the attached figures: Bode plots and step response of the Loop at each step.
0. [Not Plotted] DCTrans sensing, MCL actuation on CARM. FMs1,2,3,5,8; UGF = 120. (DARM not considered at all)
#4 Seems like the most sticky part. While both sides of this look stable as far as I can tell. I feel that flipping from the red phase curve to the teal might not actually be ok, since they are on either side of the bad phase of 0 degrees. It isn't immediately evident to me how to easily model the transitions between steps, rather than just the stability of of each step in the steady state.
Tonight I noticed that the drop in PMC transmission was ~1V, more than the usual of ~0.5V from the daily drift.
While re-aligning on the table, I noticed that the misalignment was not from either of the steering mirrors; i.e. I has to walk them both to get the alignment back. This implies that the misalignment is generated far upstream. Maybe the the laser itself is moving. We need some updates from Steve's laser misalignment tracker.
I'd like to replace the paper target with IOO -QPD_POS so we can log it.
The qpd was removed from the east end table and threaded adaptor ring epoxied on it's shell.
This tube will cut down the amount of emergency exit light getting into the qpd.
Den and I spent some time with the interferometer last night with hopes of bringing in the AO path, but were stymied by the (re)occurrence of the anomalously high low frequency motion of the Xarm, as seen by fluctuations of TRX from .9 to .2 while "held" on resonance.
Jenne reported that they weren't seeing it earlier in the evening, and then it started again when I showed up. Holding the arms on IR, we could see a fair amount of excess low frequency noise in the BEATX_FINE_PHASE_OUT_HZ channel, as compared to BEATY, bringing its RMS to 5 times that of the Y arm. From the shape of the excess noise (broad slope from DC to tens of Hz), Rana suspected air currents and/or scattering effects being the culprit.
Den poked around a bit on the PSL table, which didn't really change much. He then went down to the X end table to inspect the table, and while he was there, I noticed the noise go down to being in line with the Yarm. I joined him at the end, and we found the beat phase noise in the frequency region of concern to be hugely sensitive to tapping on the enclosure, air current, etc. There is also a ton of green light everywhere, and multiple spots of green light around the green refl PD.
At that point however, the quiescent noise was acceptable (TRX fluctuations of <.2), so we went back to the control room to try to lock. Unfortunately, after a few attempts, the noise was back. At this point, we went home. The layout of the end table likely needs some attention to try and minimize our susceptibility to excess scatter effects.
Turn off the AC and flow bench please.
Electronic components should be ISOLATED as they are installed on the optical tables.
This is essential to avoid ground loops, 60 Hz and harmonic peaks in the spectrum. We have just got some made.
Please only use it for this reason. Earlier black delrin base plates were used up in not needed places.
The anodized Aluminum base plates with magenets certainly will conduct.
Yend seismometer isolation kit (elog 8461) hosts Guralp seismometer. I made a cable for inside connection, assembled the kit and relocated the instrument from its previous position at the yend inside the kit.
Seismometer is connected to the readout box and running.
We noticed that PRMI RIN is high when the cavity is locked on RELF33 I&Q signals. We compared the level of power fluctuations when PRMI was locked using REFL11, REFL55 and REFL 33. Attached plot "prmi_rin" shows the spectra.
Then we excited PRM and measured length to RIN coupling when PRMI was locked on REFL33 I&Q. DC offset of PRCL is only 3%. But MICH offset seems to be ~nm. When we gave offset of -15 cnts to the servo, power fluctuations improved by a factor of few.
Then we looked at DRMI. It seems that SRC macroscopic length is off but we still could lock it stably. To account for macroscopic length detuning we had to rotate REFL55 phase from 25 degrees to 50 degrees. Power at AS port increased by factor of ~2 compared to PRMI configuration. SPOP18 is decreased only by 30%. Attached plot "drmi_power" shows POP18, POP90, POPDC and ASDC in PRMI and DRMI configurations.
Plot "src_ol" shows srcl OL transfer function. UGF is 70 Hz. We have also centered SRM OL and copied the servo filters from PRM, gains are set to keep UGF at ~0.1 Hz and 7 Hz
This is a more detailed procedure:
1. Phase: REFL11: 19 degree, REFL55: 50 degrees (25 degrees for PRMI configuration)
2. Input matrix:
3. Servo parameters:
PRCL: gain = -0.02, FM4,5 + trigger FM2,3,6,9
MICH: gain = 0.8, FM4,5 + trigger FM2
SRCL: gain = 0.25, FM4,5 + trigger FM2,3
signal is SPOP22 , levels 40:25
The daytime crew had noticed that there were some ETMX angular shifts happening without any control or intention.
I reseated and strain relieved the bias cable coming into the backplane of the coil driver and now it seems OK.
In the 4-hour-long second trend plot below, the era before 2300 is before reseating. Afterwards, we make a couple adjustments, but so far there has been no un-asked for alignment shifts.
AdS has been run on both arms and offsets saved. Its locked on green/red and the beat frequencies are low and the amplitudes high.
Sun May 18 23:53:37 2014: still OK...I declare it fixed.
Xend internal cabling and external connector is ready. We are waiting for seismometer from Gyro lab. We still need to fix the pot with clamps after we put the instrument in.
We also need a long cable from Xend to the guralp readout box.
We have looked at a few things that do and don't affect the out of loop noise of the ALS X beat, and found that cavity alignment and beatnote RF frequency had the strongest effects.
Possible causes of noise:
1. Air currents from A/C or flowbench. No effect.
* When table lid is on, turning on and off the flow bench air did not qualitatively change the out of loop beatnote time series signal.
2. Scattered light from other beams hitting green PDH PD. No effect.
* There are a few spots of green light that are hitting the case of the PDH photodiode, but when I put an iris in place to block those spots, there was no change in the beatnote spectra. This makes sense to me since none of those spots were close to hitting the diode itself.
* Rana did notice that the beam was not well centered on the PD, so he steered the beam onto the center of the diode. Also, the PD is now tilted a little bit so that the reflection from the diode doesn't go back into the beam path. Neither of these things had an effect that we noticed in the beatnote noise.
3. Oplev laser light getting to PDH PD. Not tested.
* We don't see any red light over by the PDH PD, so we did not try turning off the oplev's laser to see if that had an effect, but we suspect that it is not the cause of our noise.
4. Clipping of main IR / green beam on Xend table. Not tested.
* We should still go have a look at this, but we no longer think that this is the main cause of the elevated noise.
5. Scattered light all over Xend table. Not tested.
* We should still work on dumping extraneous beams on the table, but we do not think that this is the main cause of the elevated noise.
* Rana took some photos so that we can see how truely bad the situation is.
6. Amplitude modulation dip in NPRO. Not tested.
* It is probably still a good idea to check this, in case the dip in the amplitude modulation has changed over the year or two since it was last measured, but we also don't think that this is the main problem.
7. Check PDH servo. Not done.
* I think this is still on Q's long-term todo list, but we should give the PDH servos a once-over.
8. Arm cavity longitudinal motion. No effect.
* While the Xarm was locked with IR, we put a line at 1.7 Hz with 325 counts into the ITMX position. To keep lock, the ETM had to move as well. When we turned on this line (and increased its amplitude up to the final value of 325 cts), we did not see any qualitative change in the beatnote time series noise.
9. Arm cavity alignment. Significant DC effect.
* When the alignment of one of the arm cavity mirrors is changed, the DC value of the beatnote signal changes.
* ITMX moved in yaw, we see a 7kHz/15urad DC shift in the BEATX_FINE_PHASE_OUT_HZ time series.
* ETMX moved in yaw, we see an 8kHz/5.5urad DC shift in the time series. We aren't sure why this is about a factor of 3 times larger effect (same shift for smaller misalignment) than the ITM.
* We want to do a Yuta-style analysis to see what the angle to length coupling looks like, so that we can measure the angular motion of our cavity mirrors and put the expected noise into our ALS noise budget. Perhaps this will help us understand the low frequency difference between our in-loop beatnote error signal and our in-loop PDH error signals (red vs. maroon on the ALS noise budget posted above Pianosa).
* I've asked Manasa to take some transfer functions in the morning, so that we can start to have an idea of what is going on with this.
10. Beatnote RF frequency. Significant broadband effect.
* We have found that when the Xarm beatnote is at low RF frequencies, the noise is high, and when the beatnote is at high RF frequencies, the noise is low!
* Low RF freqs are below about 40 MHz, while high RF freqs are above about 90 MHz. This has not been tested for the Yarm. Also, these are for the case of "temp slider up, beatnote up". I have not checked if the same is true for the other side of the PSL frequency, although I don't have reason to believe that it would be.
* Maybe we are saturating some amplifiers? We need to check this out. One thought that Den mentioned was the harmonics, and that perhaps they are causing trouble in the electronics.
* Den is going to think about implementing a frequency divider so that we can directly digitize the beatnote signal.
* Here are spectra for different cases:
* And here is a spectrogram showing us going back and forth between the high and low noise states:
* A: First noticing that noise is good when RF frequency is high.
* B: Not locked on TEM00 mode, so extra noisy. Disregard.
* C: Bad noise time. Xbeat was 21 MHz (dark purple on DTT spectrum above), Ybeat was 118 MHz (sea green on DTT spectrum above).
* D: Good noise time. Xbeat was 89 MHz (light purple on DTT plot), Ybeat was still 118MHz (turquoise on DTT plot).
* E: Bad noise time. Xbeat was 37.5 MHz, Ybeat was still 118 MHz.
* F: Good noise time. Xbeat was 113 MHz, Ybeat was still 118 MHz.
Anodized aluminum dumps replaced by 6 razor beam dumps.
Two more razor beam dumps added this afternoon. The picture will updated tomorrow.
So, I really should have done this as soon as Manasa measured the arm lengths... I've updated my MIST model with the real arm lengths, but still am using assumed identical losses of 75ppm on each mirror. (I've tried measuring the arm losses for real, but got numbers in the hundreds of ppms, so I need to reexamine things...)
Here's a simulation of the fields in a perfectly locked PRC when CARM is swept (Normalized to input power = 1).
More importantly, here's the latest simulation of MICH vs. PRCL demodulation angle separation in the 3F signals. It seems that we may be getting burned by using REFL33 for the PRC lock. REFL165, on the other hand looks much more robust. We should try this out.
(Some of my previous simulations incorrectly implemented MICH excitations; I only moved the ITMS, not the ETMS along with them, so some other stuff slipped in... )
Here's the angles of MICH and PRCL from the my earlier plot by themselves; this shows that the individual demod angles in REFL165 aren't changing much either.
Since Q has found that REFL165 will be better for holding the PRMI while we reduce the CARM offset, I had a look at locking PRMI sideband locking with both 3f PDs.
I checked the REFL165 demod phase, and changed it from -142.5 deg to -138.5 deg. to minimize the Q signal while driving PRM length.
I found that keeping the MICH and PRCL loop gains the same, and using matrix elements +0.1 for both I and Q for REFL165, rather than +1 for both I and Q for REFL 33.
MICH gain is +0.8, PRCL gain is -0.02. FMs 4,5 on for both, FM 2 triggered for MICH, FMs 2,3,6 triggered for PRCL.
I then locked the PRMI on sideband with REFL 33 and then REFL 165, and measured the other one as an out of loop sensor of the motion. I find that REFL33 and 165 are both comparable, and so we shouldn't have any trouble using REFL165 for locking.
We spent some time tonight looking at locking the PRMI with REFL165 vs. REFL33, while reducing the CARM offset.
We were not able to lock the PRMI on REFL165 I&Q at small CARM offsets. When locking at larger CARM offsets (about 100 counts, which is about 100nm) and then re-adjusting the REFL165 demod phase as I reduced the CARM offset, I saw that I had to significantly rotate the phase. For PRMI only (no arms), the REFL165 demod phase was -138.5 deg. When the PRMI was locked with a -100 count CARM offset, the optimal demod phase was -123 deg. Then at -90 counts the phase was -113 deg. At -70 counts, the phase was -108 deg, at -50 counts it was -98 deg, and at -40 it was -93 deg. We want to go back and look at these more carefully, and in a more continuous way, by watching the sensing matrix calibration lines. It's unclear to me right now why we're seeing this, but it's possible that we're getting some kind of extra 55MHz resonances.
REFL DC looks like it should be good - same slope and gain as sqrtTR, extra 20 or 30 deg of phase margin, so we think that we should be able to transition over to it, and then try engaging the AO path. Tonight we had Den's new 1kHz lowpass engaged, and with this, everything looks nice and stable.
Game plan: Bring CARM in until transmissions are at about 10ish, then try keeping CARM on sqrtInvTrans for the DC part, and engage the AC AO part with REFL DC. We probably just need to try this for a while more to find just the right way to turn it on.
Need to think about demod phase rotation vs CARM offset as well as extra resonances, but this may take a while, and if we can just get the AO path engaged, that would be good.
There are 9 razor beam dumps at ETMY-ISCT
I found MC unlocked this morning. I looked at the 2 day trend of the MC suspensions and found MC2 suspensions have been misaligned.
I used Rana's ezcaservo trick to recover MC lock. This brought the MC_REFL down to 0.7 counts. I did the rest of the alignment by moving the MC2 suspension sliders only. MC_REFL is down to 0.45-0.5 counts and TRANS_SUM is at ~16300.
Also, I found the WFS servo was left turned OFF. I re-enabled them as well.
I fixed a bug in the SUS_SINGLE screen, where the total YAW output was incorrectly displayed (TO_COIL_3_1 instead of TO_COIL_1_3). I noticed this by seeing that the yaw bias slider had no effect on the number that claimed to be the yaw sum. The first time I did this, I accidently changed the screen size a bit which smushed things together, but that's fixed now.
I committed it to the svn, along with some uncommitted changed to the oplev servo screen.
Attached is the measurement of the transfer function from ITMX oplev error in yaw to the ALSX error signal.
The arm was locked to the IR using POX and the green beat frequency (between X arm trans in green and PSL green) in this case was 27MHz.
The transfer function looks mostly flat between 1Hz - 30Hz at 700-800 Hz/urad. The DC shift that Jenne measured from the time series is ~500 Hz/urad.
So far I have not been able to measure the TF below 1Hz without the arm losing its lock. Updates will follow.
Data xml file can be found in /users/manasa/data/140521/
Tektronix RECALL on TDS3000 or TDS300B oscilloscope BATTERIES TDS3BATB
This Lithium-Ion battery can be a fire hazard ! Remove battery pack and recycle it through Safety Office !
PMC has been unlocked for ~4hrs, not sure why. It's servo gain was down at -10dB...
Relocked with transmission of .76V, MC locks fine with WFS, transmission of 15.5k.
Below are the transfer functions measured between the angular (pit, yaw) motion of X arm mirrors and the ALSX error signal. The measurements were again made for 1Hz-30Hz.
The transfer functions are mostly flat.
ITMX P - 200-300 Hz/urad (beat freq = 45 MHz)
ITMX Y - 700-800 Hz/urad (beat freq = 27MHz)
ETMX P - 500-600 Hz/urad (beat freq = 56 MHz)
ETMX Y - 1000-2000 Hz/urad (beat freq = 62.5MHz)
Data xml files can be found in /users/manasa/data/140521/
I added two green glass absorbers. The oplev centering may need a touch up when it is well aligned.
The Y arm green transmission had come down to 0.3 and the green steering mirrors on the Y end table required some minor alignment adjustments to bring back transmission to around 0.75 counts.
I just realized that I forgot to elog this, but yesterday afternoon I bypassed the amplifier in the BeatX path, and now the X beatnote is about -27dBm. Arms lock nicely with ALS.
And the out-of-loop level of the ALSX compared with the previous measurement is ...?
I came in and PMC transmission was at 0.5V, and ETMX was swinging around a lot, (LSC mode was on).
Turning off oplevs let ETMX calm down. I realigned the PMC to 0.82V.
MC wouldn't relock, it looked misaligned in pitch and yaw on MC camera.
I've touched the alignment, and gotten the reflection below 0.5, but it unlocks periodically, spot positions aren't great, and turning on WFS throws it out of alignment. ughhhhh
Rga scan at pump down 77, vacuum normal valve configuration, maglev rotation 560 Hz and day 111
Sorry, I had been in a hurry when I worked on this last week, and again when I wrote the elog, but I wanted to at least put in a note for any weekend workers.
The ALS beatnote setups need alignment on the PSL table. However, even at very low RF beat frequency, the X beatnote now at low frequencies matches our best measurement from last week. The "HEPA off" (teal and purple) measurements are from last week, and the red and blue are from this week. The X beatnote was 10MHz and the Y beatnote today was 31MHz.
Grr. I am very frustrated. After lunch I redid alignment for both X and Y green systems (Yarm both at the end and on the PSL table, Xarm just on the PSL table). After that realignment work, I cannot find a beatnote for the Xarm!!!
The Ybeat, after aligment, was up to -5.5 dBm when the beat was at 11 MHz. Last week it was something like -20 dBm, so alignment makes a big difference. After doing IR alignment I had noticed that the green transmitted through the Yarm didn't look very bright on the camera, and the power was around 0.2, so I went to the Yend and gently touched the green input steering mirrors, and got the Ygreen trans PD back to more than 0.9 with the PSL green shutter closed. Awesome. Then I touched up the Ygreen PSL alignment, and then saw that the beatnote was nice and large. Hooray. I measured the out of loop noise, and it was even better than the best we saw last week: (greenish was best last week for Yarm, teal blue is new Ygreen):
At this point, I still hadn't touched anything on the X path (except the PZT input steering mirrors, remotely from the control room). The beatnote was about the same size as it was on Friday, around -27dBm. I went onto the PSL table and did the same alignment procedure that I had just done for the Yarm: Remove the green trans PD and the accompanying lens so that I get far-field spots on the wall, and then steer the PSL green and the X green spots until they are nicely overlapped at both the camera (near-field) and on the wall. I looked at the DC output of the beat PD, and centered the beam on the diode. I put back the thorlabs DC transmission PD and the lens, and centered the beam on that. However, after this work, I cannot find a beatnote for the X arm! I still see the nice big Ygreen beatnote, and I have the PSL and Xend temperatures where they usually are ( abs(FSS Slow) < 0.1, and X end Slow around 10,090. ) I scanned -10,000 counts, and +5,000 counts from there, and still don't find a beatnote!
I went back inside, and I don't see an RF signal coming into the beatbox from the Xarm. It's not the cable's fault though, since I then hooked the RF output of the beat PD to a 'scope, and still didn't see any beatnote. The DC path of the PD is definitely seeing things, because when I switch the 'scope over to the DC output of the Xbeat PD, and I block/unblock the beam, I see the voltage step up and down as expected.
I have not pulled out the Xgreen broadband PD, but unless someone else has a good idea of what to check, that might be one of the next things to do.
Ideas of things I could try:
* Put the X broadband PD on the Y beatnote path to see if I see the same Y beatnote (use the port where the Y green trans PD is, since it has the coaligned beams, and a lens).
* Open the PD and see if anything on the RF path is fried.
* Move the Y PD over to the X path, to see if it sees the beatnote.
Also, while I was working on the PSL table, I heard noise that sounded like a bearing rolling around. I suspected the HEPAs, since the one on the north east corner of the table has a problem when it's turned up high (we've known about this for a long time), however turning off the HEPAs didn't affect the noise. The noise is strongest near the back of the PSL controller on the shelf above the table, and the PSL controller box is vibrating. So, I suspect that the fan on the PSL controller box is about to give out.
EDIT: To clarify, I mean the Innolight's controller.
The bearing is chirping in the back of the 2W Innolight laser controller. It is loud enough to hear it. I placed 4 soft rubber feet under the controller to avoid shaking other things on self.
The HEPA filter bearing becomes noisy at 50V
Keep it at 20V for low noise