[Den, Annalisa, Manasa]
The Alberto laser was moved from the PSL table. The height of the heat sink rendered a beam height of only 3 inches. I did not want to deal with changing beam height at the table. So, we went ahead and used the old heat sink. I used the beam scan to make measurements of the beam width to match my mode-matching calculations and found some mismatch with the measurements done earlier. So I will measure the beam width again before alignment.
I will also have to change the layout because of the supporting posts that have come up with the new box. Annalisa is doing a COMSOL model to check what the thickness of these supporting posts should be so that the box stays stiff.
The MC seemed to be losing lock recently quite a bit. I noticed that the PC Drive RMS signal was red.
This means that the high frequency drive to the Pockels cell was too high by a factor of 2-3 and sometimes saturating and breaking the lock.
I fiddled with the gains on the FSS screen until this value went down. It looks like there is some kind of high Q oscillation; it takes a couple minutes for the PC Drive RMS to settle to its new position after changing the gains.
The attached trend plot show the last 2 hours. The mean is now back to ~1 V and seems OK. We should really examine the FSS or MC error point spectra with the RF analyzer while exploring this gain space.
Enclosure cover #1 transmission measured in 1064 nm, 156 mW, P polarization and beam size ~ 1 mm
As condition: fully assembled, protective layer removed, tinted- adhesive activated on yellow acrylic on top of each other.
T = 1.2 % in 20 minutes exposure test. This agrees with the test measurement of 6-18-2012
There is a reflected 2-3 cm circular glare that is barely visible on sensor card. It is well below 1 mW level
As we are installing the NPRO with ~350 mW of power we have to address what additional shield should be installed.
The June 2012 test with 1W power burned through of the 3 layer IR coated films in 3-4 hours.
We 'll use Aluminum shields in the high power path till we come up with better solution.
Note: The TRY PD isn't installed and normalized properly yet, so the IFO OVERVIEW screen indicates lock for the Yarm constantly, which is not true. Hopefully in the next day or so the screen will be back to telling the truth.
Also, the LSC Locking was left ENABLED (presumably over the weekend). This is not so good. It can kick optics around, so we should all take a look when we walk through the control room, and if no one is locking, please disable the LSC master switch.
The PMC locked manually. MC grabbed lock instantaniously
with the script, as it was down.
1) We still need to drill and install the thumbscrew latches which secure the lids to the table. We cannot use the tables as an acoustic enclosure with loose lids.
2) For the camera issue, the idea is to put the longpass filters on the front of the cameras: then they are only sensitive to light with wavelength > 800 nm.
3) Whenever any interferometer work is happening the light switches must be in the positions which have been marked on them (and which most everyone ignores foolishly). We have never been insensitive to the room lights; the black table enclosures just give us a false sense of security. Room lights impact the interferometer noise.
I started populating the end table; the TRY path to start with. I found that I need to redo the cables/electronics layout around the table as we have only one cable feedthrough hole with the new box right now. I need another hand with this and will have Annalisa help me tomorrow.
P.S. I misaligned PRM and restored ETMY to get TRY flashes. I tweaked ETMY to see strong TEM00 flashes.
Old slider positions on medm screen in case we need to restore them:
TT1 TT2 ITMY ETMY
P -1.3586 0.8443 0.9114 -3.7693
Y 0.3049 1.1507 -0.2823 -0.2761
Enclosure is at the east end. It has it's bottom o-ring in place. It will be ready for optics tomorrow around 5pm
I have to shim out the enclosure, finish leveling the table and cut surgical tubing O-ring for the top.
Glued surgical latex tubing with super glue into O-ring shape. The existing in place tubing K-100, OD 0.125" (actual size 0.140"), wall 0.031", ID 0.062".
I have just found out that tolerances on tubing OD are + - 0.026" by the manufacturer. I'm getting larger tubing for better fit.
The table is ready for optics.
Things left to do:
1, finalize o-ring size 2, finish cable feedthrough 3, finalize window connection 4, IR-Thermashield strips for bridge sides
While I did think that the plastic boxes were cool; I am not happy with the new enclosure on several aspects as I am setting up the TRY PDs/camera.
1. I strongly feel the o-rings should be glued/fixed to the plastic box atleast at some points. Even if we replace the current thin one with a thicker tubing, it takes forever to get the o-ring into the groove when it slips out. Also if it slips from the groove, it falls through the optical path and there are chances of burning the tubing when the NPRO is ON.
2. With the transparent tables, the cameras are sensitive to the room lights. I had to switch off the room lights/use ND filters to see a nice beam at the TRY camera.
3. The lids are heavy...might be a good way to train....but removing and putting them back will definitely increase the pain in getting the green aligned to the arms atleast until we have the PZTs set up.
1, finalize o-ring size 2, finish cable feedthrough 3, finalize window connection 4, IR-Thermashield strips for bridge sides 5, replace bridge support post with solid one
I'm having Steve order the following:
If you want him to add anything to the order let him know ASAP.
Graph Limits: The limits on graphs have been problematic. They often reflect too large of a range of values, usually because of dropouts in data collection. Thus, they do not provide useful information because the important information is washed out by the large limits on the graph. For example, the graph below shows data over an unnecessarily large range, because of the dropout in the 300-1000Hz pressure values.
The limits on the graphs can be modified using the config file found in /40m-summary/share/c1_summary_page.ini. At the entry for the appropriate graph, change the amplitude-lim=y1,y2 line by setting y1 to the desired lower limit and y2 to the desired upper limit. For example, I changed the amplitude limits on the above graph to amplitude-lim=.001,1, and achieved the following graph.
The limits could be tightened further to improve clarity - this is easily done by modifying the config file. I modified the config file for all the 2D plots to improve the bounds. However, on some plots, I wasn't sure what bounds were appropriate or what range of values we were interested in, so I will have to ask someone to find out.
Next: I now want to fix all the funny little problems with the site, such as scroll bars appearing where they should not appear, and graphs only plotting until 6PM. In order to do this most effectively, I need to restructure the code and factor it into several files. Otherwise, the code will not only be much harder to edit, but will become more and more confusing as I add on to it, compounding the problems that we currently have (i.e. that this code isn't very well documented and nobody knows how it works). We need lots of specific documentation on what exactly is happening before too many changes are made. Take the config files, for example. Someone put a lot of work into them, but we need a README specifying which options are supported for which types of graphs, etc. So we are slowed down because I have to figure out what is going on before I make small changes.
To fix this, I will divide the code into three main sectors. The division of labor will be:
- Sector 1: Figure out what the user wants (i.e. read config files, create a ConfigParser, etc...)
- Sector 2: Process the data and generate the plots based on what the user wants
- Sector 3: Generate the HTML
Beautiful double peaks. I don't see the triple zero-crossings. Is this because you adjusted the phase correctly (as predicted)?
Don't you want to have a positive number for POP22? Should we set the demod phase in the configuration script for the positive POP22, shouldn't we?
The attached plot shows that also the behaviour of the REFL11 and 55 signals is qualitatively equal to the simulation outcome.
I had a look at the POP110 signal, with the PRMI flashing.
1) The LSCoffset script does not zero any more POP22_I_ERR offset. I did it by hand
2) The gain of POP22 is changed a lot, as well as the sign: now sidebands are resonant when POP22_I is negative
3) POP110 seems to deliver good signals. The plot attached shows that when we cross the sideband resonance, there is a clear splitting of the peak. If we rely on the simulations I posted in entry 8401, the full width at half height of the POP_22 peak is of the order of 5 nm. Using this as a calibration, we find a splitting of the order of 7 nm, which is not far from the simulated one (5 nm)
There are some tips for how to appy nail polish on YouTube from MKNails and MissJenFABULOUS. Their tips on how to prepare the site for a strong bonding strength are probably helpful for our gold/nickel coated tools. For chrome tools we may need to abrade the surface with a stone or fine sandpaper for it to take the layer better. IF the YouTube videos don't do it for you, then I suggest contacting Tom Evans at LLO to find out what kind of nail polish he uses.
For the 110 MHz demod boards, we would ideally have a plugin bandpass filter. If you have some specs in mind, you can email mini-circuits or pulsar microwave about making a custom part; its not too expensive usually.
For the meantime, you should remove the onboard one and replace with a combination of low/high pass filters from Mini-Circuits. If you put a SLP-150 and a SHP-100 in series, the insertion loss should be less than 1 dB.
I think the ERA amps are OK for now, but they die with time, so they just need to be tested and replaced if necessary.
A heavy duty plastic box is the likeliest candidate for the optical table toolbox. It measures 5 9/16 in. x 11 5/8 in. x 4 5/8 in. and fits all the tools comfortably. ( http://www.mcmaster.com/#plastic-bin-boxes/=m4yh4m , under Heavy Duty Plastic Bin Boxes)
The list of tools has been updated to include a pen and a wire cutter as well as everything previously stated.
In addition, Steve has recommended that boxes should be secured to the walls or surfaces near the optical tables as opposed to the optical tables themselves, as to keep the tables from wobbling when tools are being exchanged.
A diagram of tentative box placements will go out soon.
No, the small boxes must be attached to the optical tables. They won't be heavy enough to change the table tilt.
Also, all tools must be color coded according to the optical table using the 3M Vinyl table color code:
So the new tentative plan on the boxes is to bolt them (magnetic strips were proposed but overruled on the grounds that they're not strong enough to withstand being knocked down by accidents).
The boxes are going to be a mix of the Thorlabs Benchtop Organizer (http://www.thorlabs.com/thorProduct.cfm?partNumber=BT17) and the original box. The box will have a region covered in mesh, so tools can be placed and held there. The box will also have a spacer at the bottom, with another mesh right above it, lined up. However, this double-mesh will only cover half of the box. The other half of the box will be compartmentalized to hold things such as screws, connectors, etc. I will talk to Steve about building the boxes.
Also, using nail-polish to coat the Allen wrenches is not going to work. Nail polish does not stick easily enough. The tentative new plan is oil paint, but this is to be reviewed.
Finally, the diagram with the placement of the boxes relative to the optical tables has been put on paper, but needs to be computerized so it's easier to read. This will be done as soon as possible.
This SCPQ-150+, which is surface mount, might also work in place of the PSCQ-2-120, which is through-mount. Would need to be reconciled with the board layout.
Breadboards may not be suitable for a reliable work. Why don't you switch to any protoboard and real soldering?
I have re-implemented POP110. The cable coming from the AS110 diode is disconnected, labeled, and sitting in the cable tray next to the LSC rack.
Now the POP diode path is:
Thorlabs 10CF ----many meters of heliax cable-----> Bias Tee ------> RF amplifier ------> Splitter ------> Bandpass 21.7MHz --------> POP22 demod board
POP DC High pass 100MHz
POP110 demod board
I started to look into putting together a 110 MHz demod board to be used as POP110 (see #8399).
We have five spare old-skool EuroCard demod boards (LIGO-D990511). From what I gather (see #4538, #4708) there are two modifications we do to these boards to make them ready for prime time:
#4538 also describes some other modifications but I'm not sure if those were actually implemented or not:
What we'll need for a 110 demod:
I'll scrounge or order.
The voltage regulator on the QPD breadboard seems to be having problems... yesterday Eric helped me debug my circuit and discovered that the +12V regulator was overheating, so we replaced it. Today, I found that the -12V regulator was also doing the same thing, so I replaced it. However, it's still overheating. We checked all of the setup for the power regulators yesterday, so I'm not sure what's wrong.
I've also noticed that not all the connections on the breadboard that I've been using seem to work - I may search for a new breadboard in this case. Need to check I'm not doing something stupid with that.
I investigated the situation of the two Sorensen supplies in the LSC rack (1Y2). They are there solely to supply power to the LSC LO RF distribution box. One is +18 V and the other is +28 V. All we need to do is make a new longer cable with the appropriate plug on one end (see below), long enough to go from the bottom of the 1Y3 rack to the top of 1Y2, and we could move them over quickly. Some sort of non-standard circular socket connector is used on the distribution box:
It could probably use thicker conduction wire as well.
If someone else makes the cable I'll move everything over.
Here is a summary of a simulation of the error signal behavior in the PRMI configuration. The main parameters are:
L_PRC = 6.7538 m
Schnup = 0.0342 m
fmod1 = 11.065399e6 Hz
fmod2 = 5 * fmod1
These two plots shows the response of the POP22 and POP110 signals (in almost arbitrary units) to a PRCL sweep around the resonance. The splitting of the 55 sideband peaks is well visible in the second plot. It is due to the fact that the 55MHz sidebands are not perfectly matched to the PRC length
The same thing when sweeping MICH. The peaks are wider and it is not possible to see the splitting.
These are the error signals (REFL11_I/Q and REFL_55_I/Q) as a function of the PRCL (left) and MICH (right) sweep. Here the demodulation phases are not properly tuned. This is just to show that when the phase is wrong, you can get multiple zero crossings (in this case only in the Q signals, but in general also in I) close to resonance.
If the phases are tuned in order to maximize the slope of the I signals with respect to PRCL, one gets these "optimized phase" responses. It is that the phase does not correspond to the one that makes the PRCL peak to peak signal small in Q. The Q signals are indeed flat around resonance for a PRCL motion, but they deviate quite a lot from zero when moving more far from resonance. Moreover, both the REFL_55 error signals (I for PRCL and Q for MICH) are crossing again zero at two additional positions, but those are quite far from the resonance point.
These plots just show the PRCL and MICH error signals together with the POP22 and POP110 signals, to give an idea of the level of triggering that might be needed to be inside the linear range. It seems that if we trigger on POP22 when using the REFL55 signal we loose a bit of linear range, but not that much.
If you reached this point it means you're really interested in this topic, or maybe you have nothing better to do... However, this plot shows the effect of linearization of the error signal, obtained dividing them by the proper POP22/110 signal. The linear range is increased, but unfortunately for the 55 signals, the additional zero crossing I was mentioning before creates two sharp features. Those are however quite outside the triggering region, so they should not be harmful.
I modified /opt/rtcds/caltech/c1/chans/daq/C0EDCU.ini to include the C1:LSC-DegreeOfFreedom_TRIG_MON channels. These are the same channel that cause the LSC screen trigger indicators to light up.
I vaguely followed Koji's directions in elog 5991, although I didn't add new grecords, since these channels are already included in the .db file as a result of EpicsOut blocks in the simulink model. So really, I only did Step 2. I still need to restart the framebuilder, but locking (attempt at locking) is happening.
The idea here is that we should be able to search through this channel, and when we get a trigger, we can go back and plot useful signals (PDs, error signals, cotrol signals,....), and try to figure out why we're losing lock.
Rana tells me that this is similar to an old LockAcq script that would run DTT and get data.
EDIT: I restarted the daqd on the fb, and I now see the channel in dataviewer, but I can only get live data, no past data, even though it says that it is (16,float). Here's what Dataviewer is telling me:
Connecting to NDS Server fb (TCP port 8088)
LONG: DataRead = -1
No data found
T0=13-03-29-08-59-43; Length=432010 (s)
No data output.
Connecting to NDS Server fb (TCP port 8088)
LONG: DataRead = -1
No data found
T0=13-03-29-08-59-43; Length=432010 (s)
No data output.
I seem to be able to retrieve these channels ok from the past:
controls@pianosa:/opt/rtcds/caltech/c1/scripts 0$ tconvert 1049050000
Apr 03 2013 18:46:24 UTC
controls@pianosa:/opt/rtcds/caltech/c1/scripts 0$ ./general/getdata -s 1049050000 -d 10 --noplot C1:LSC-PRCL_TRIG_MON
Connecting to server fb:8088 ...
nds_logging_init: Entrynds_logging_init: Exit
Hit any key to exit:
Maybe DTT just needed to be reloaded/restarted?
[Rana, Gabriele, Jenne]
We have now locked the PRMI using REFL55 I&Q for more than one minute!!!!!
This isn't really the most useful plot as is, but it was created using:
/opt/rtcds/caltech/c1/scripts/general/getdata C1:LSC-POP22_I_ERR_DQ C1:LSC-REFL55_I_ERR_DQ C1:LSC-REFL55_Q_ERR_DQ C1:LSC-MICH_IN1_DQ C1:LSC-MICH_OUT_DQ C1:LSC-PRCL_IN1_DQ C1:LSC-PRCL_OUT_DQ -d 80 -s 1049013520 -c
This is just one of several long lock stretches. If I can get the TRIG_MON channels to be saved, we can automatically (versus my by-hand search) find lock stretches and make this kind of plot. Although we want them saved in some raw format so we can zoom in on selected axes, I think. This might require some python-fu from Jamie, or learning of python-fu for Jenne.
The secret sauce:
* The big key was changing REFL55's phase. It was -4 when we looked at the I&Q signals, and minimized the PRCL information in the Q-phase. We were able to get short lock stretches with this. During these stretches, Rana changed the REFL55 phase until the lock sounded (audibly) quieter. The final phase we settled on was +26. As we changed the phase, the lock stretches got longer and longer.
* We also tweaked up the POP22 phase. It was close from our previous efforts of looking at non-locked time series, but we perfected it by minimizing the signal in the Q-phase during lock stretches. We also found that it drifted (according to this method) by ~5 degrees over ~half an hour (I don't remember the exact time between our phase tunings).
* POP22's low pass filters (both options, ELP10 and ELP50) must be OFF for any lock to be acquired. Turning on either filter prevents locking.
* Normalization helped a lot. Without normalization we weren't really able to catch any locks, certainly not of any significant length. (0.004, using POP22I, for both MICH and PRCL).
** Normalization: use POP22I for both MICH and PRCL, value = 0.004
** Input matrix: MICH with REFL55Q, value = 0.01; PRCL with REFL55I, value = 0.01 (we used the small number in the matrix so our servo gains weren't too tiny).
** POP22 lowpass filters OFF
** Analog whitening OFF for REFL55, POP22.
** Analog gain for REFL55 I&Q = 27 dB
** Analog gain for POP22 I&Q = 15 dB
** Output matrix: MICH with -1 to ITMX, +1 to ITMY. PRCL with +1 to PRM.
** Servo gains: PRCL = 0.75; MICH anywhere between -3 and -20. Best in the -8 to -15 range.
** Vio2 filters in ITMX, ITMY, PRM (all actuated-on mirrors) were OFF. (Still need to lower the Q on these so they don't ring).
** PRCL and MICH triggering on POP22I. The trigger-off was always 20, but the trigger-on changed throughout the night from ~170 to ~50. I think 130 was a trigger value for at least some of the long-time locks.
** Low frequency seismic was small (i.e. no anomalous 0.1 Hz - 1 Hz noise) during successful lock times. (Not to say it must be low, but it was low when we were able to lock for long stretches).
Things we had looked at and thought about throughout the evening:
* Oplev calibration. See elog 8391 and 8393. Optimized BS and PRM to reduce yaw angular motion.
* Actuators all functioning as expected. We checked transfer functions of MICH_OUT/MICH_IN1 for locking with different optics, to ensure that at high frequency the response was 1/f^2. Also, we locked MICH with (a) both ITMs, (b) BS, (c) ITMX and (d) ITMY. We locked the PR-ITMY half-cav with (a) PRM and (b) ITMY. We locked the PR-ITMX half-cav with (a) PRM and (b) ITMX. Thus, we conclude that all of the PRMI-related optics are functioning as expected.
* Realigned REFL55 beam onto PD. It was clipping a bit, so the DC power wasn't steady (when ITMs were misaligned, PRM aligned). After alignment, the DC power as seen on a 'scope was much smoother.
* Turning off the limiters for the MICH and PRCL control signals allowed us to hear a high-pitched whine. From looking at the time series, it's predominantly in MICH_OUT. Rana speculates that perhaps the normalization is causing the UGF to wander temporarily to an unstable place. For a time there was a high-Q peak between 500 and 600Hz, but reducing the gain (of MICH?) eliminated that. Then we heard several times, irrespective of gain setting, the ~400Hz broad peak (I say broad because I was able to see it on DTT looking at the error and control signals, and it spanned +/-100Hz).
Things to investigate:
* Is there a good reason that we should switch to triggering on POP110, rather than the current POP22? From Gabriele, Jamie and my Finesee/Mist modelling last week, without the arms, the 11MHz and 55MHz resonate at different PRC lengths. If this difference is very small, then we are fine, but if the difference is large, it could be causing trouble - we're trying to catch the lock at the linear part of the 55MHz signal, but if that does not coincide with the linear part of the 11MHz signal, we're doing the wrong thing.
* For the POP normalization, should we be using the amplitude or the power ( POP22 or sqrt(POP22) )? Why? Look at this with a modelling sweep and/or analytically.
* Look at different noise sources, potentially sensing noise, coil actuator noise,..... We should check these out, and make sure we're not limited by anything obvious.
* Make a "restore" medm screen, rather than restore script. IFO Configure restore script can pull in values from the screen (EPICS values). One screen per configuration.
* Get TRIG_MON signals saved, write script to search for triggered lock times (between given gps times), then plot interesting signals for just before lock, during lock, and until just after a lockloss.
Connecting to NDS Server fb (TCP port 8088)
LONG: DataRead = -1
No data found
T0=13-03-29-08-59-43; Length=432010 (s)
No data output.
We could not find a power supply slot for the amplifiers on the LSC rack. We had to put a temporary power supply in contradiction to our 'no temporary power supply' policy.
After 1 month, its hard to imagine that this could not have been fixed by putting in a proper fuse and fuse block. I will remove this tomorrow if I still find it this way in the bottom of the rack.
There are also 2 Sorensen switching supplies in the bottom of the LSC rack (with all of our sensitive demod boards). These should also be moved over to the old 'digital' LSC rack tomorrow for the post meeting lab cleanup.
Use fuse blocks with fuses with appropriate ampacity.
The beat note between the PSL laser and the "Alberto" NPRO laser has been measured. In particular, for each PSL temperature, more than one Aux laser frequency has been found.
The second of the three curves seems to be more stable than the other two, even if a "step" trend can be found in all of them (maybe due to the frequency change of the NPRO laser as a function of the crystal temperature continuous tuning, as mentioned in the previous elog). This is the reason why the points are not perfectly aligned, and the errors on the fit parameters are so big.
I changed the default shell on our control room iMac to bash. Since we're really, really using bash as the shell for LIGO, we might as well get used to it. As we do this for the workstations, some things will fail, but we can adopt Jamie's private .bashrc to get started and then fix it up later.
We have implemented 4Hz resonant gains for both PRM and BS yaw. The filter was already in place for PRM Yaw, so we just turned it on, but we also copied the filter over to BS Yaw. We also changed the 3.3Hz res gain and the ELP for the PRM servo to match the BS servo, since after implementing the 4Hz gain, PRM was still much noisier than BS. Now the 2 servos match, and PRM is a little quieter. We hope that tonight's locking might be a little more stable after this work.
We have put in a new EPICS input into the SUS library part, just before the OL_PIT and OL_YAW filter banks, so that the IN1 point is calibrated to microradians. I recompiled all SUS-related models. The OPTLEV_SERVO screen has been changed, so that you can see the calibration, and enter a value. The gains have been reduced by a factor reciprocal to the calibration, so the loop gain is the same.
ETMs, SRM and MCs all have "calibration" numbers of 1, so the numbers aren't really calibrated, they're just the same as always.
It looks like the PRM and the BS are moving significantly (factor of ~30) more than the ITMs at a few Hz! (Y-axis of plot is urad/rtHz)
EDIT JCD: We need to fix up the MEDM QPD indicators, and the OpLev red lights on the watchdog screen, so they match the new numbers. Also, Rana turned on the output limiters to 2000 for all oplev servos.
Very good - now you need to just put the cal factor into the filter banks so that the PERROR and YERROR signals are in microradians all the time.
EDIT JCD: In progress.
Optical lever calibrations:
ITMX pit calibration = -9.07 cts/mrad
ITMX yaw calibration = -12.33 cts/mrad
BS pit calibration = -22.86 cts/mrad
BS yaw calibration = -24.14 cts/mrad
Method: Similar to Manasa and Yuta's method last month. We mounted each oplev QPD on a micrometer translation stage, centered the beam using the steering mirror, then used tdsavg to get 10 second averages of the _INMON channel for various settings of the micrometer stage. For BS, we had to take out the PRM oplev to make room for the translation stage. All QPDs were remounted in their original positions, within less than 1mm. Measured the out-of-vac distances with the laser disto-meter, and the invac distances from the optic to the window from the CAD drawing.
Copying from other elog entries,
We calibrated oplev for ITMY. Calibration factor for C1:SUS-ITMY_OL(PIT|YAW)_IN1 are;
OLPIT: 6.29 +/- 0.11 counts/mrad
OLYAW: 5.74 +/- 0.09 counts/mrad
We calibrated oplev for PRM. Calibration factor for C1:SUS-PRM_OL(PIT|YAW)_IN1 are;
OLPIT: 15.6 +/- 0.3 counts/mrad
OLYAW: 17.8 +/- 0.3 counts/mrad
> The two REFL55 signals
Wow! It's a good news.
I think this is our first ever lock of PRMI with the REFL I/Q signals.
We kept having difficulty to obtain MICH from the REFL beam.
Next time could you make calibration of REFL55 MICH and AS55 MICH and compare the ratio with any simulation?
We locked the PRMI, this time really on the sidebands, using the two REFL55 signals.
Here are the parameters: triggering on POP22_I in at 140, out at 20. No normalization. MICH gain -0.15, PRCL gain 0.1
It seems that the lock is not very stable. It seems likely to come from some large angular motion of one of the mirrors. We'll need to calibrate the optical lever signals to understand which one is moving too much.
I measured the beat note between the "Alberto" NPRO laser and the PSL varying the PSL temperature and find the matching NPRO temperature that gave the beat.
I first switched off the FSS loop for the PSL, then I varied its temperature and switched on the loop back.
PSL temperature has been varied starting from 31.88 °C (its starting temperature) down to 23.88 by 1°C step, and then from 31.88 °C up to 36.92 °C, always with a 1°C step.
For each PSL temperature, the NPRO temperature was varied as well, in way to find the temperature to have a beat note between the two.
The trend of the NPRO laser temperature reminds the frequency change of the laser as a function of the crystal temperature continuous tuning.
I made measurements only for the first temperature of the NPRO laser which gave me the beat note. Tomorrow I'm going to find the beat note also for higher frequencies of the NPRO laser.
[Gabriele's work, I'm just spectating]
Annalisa is working on finding the PSL/AUX laser beatnote, so the PSL temp is changing, but Gabriele is still able to lock. Here are some videos:
I also took every allen key I can find so they can be sorted. They will be back in the appropriate drawer locations soon.
We discovered that the analog whitening filter of the REFL55_I board is not switching when we operate the button on the user interface. We checked with the Stanford analyzer that the transfer function always correspond to the whitening on.
This turned out to just be a loose connection of the ribbon cable from Contec board in the LSC IO chassis at the BIO break-out box. The DSUB connector at the break-out box was not strain relieved! I reseated the connector and strain relieved it and now everything is switching fine.
I wonder if we'll ever learn to strain relieve...
Because we would like to get started on testing mount vibrations as soon as possible, I've been trying to get one of the other QPDs we found to work with the summing/subtracting circuit on a breadboard. I've been using a power supply that I think Jamie built 15 years ago... which seems to be broken as of today, since I no longer read any signal from it with an oscilloscope.
I tried using a different power supply, but I still can't read any change in signal with the QPD for any of the quadrants when using a laser pointer to shine light on it. I'll be working with Eric on this later this week. In the meantime, I'll try and come up with a shopping list for the nicer QPD circuit that'll be a longer term side project.
I put a notch in FM10 for both MICH and PRCL at 628Hz, to try to prevent us from exciting the mode that Gabriele saw on Friday. Since those filter banks were all full, I have removed an ELP50 (ellip("LowPass",4,1,40,50)). I write it down here, so we can put it back if so desired.
On Friday we modified the POP22 set up: now the PD output goes to a bias tee. The DC output goes to the ADC board, while the RF output goes to an amplifier (Mini-circuits ZFL-1000LN+), to a band pass filter at 21.4 MHz and then to the ADC
Our first move has to be fixing the whitening switching for REFL55. That's the configuration we need to start and then move onto REFL165 to get to FPPRMI.
The digital one is actually switching. We decided to keep the digital de-whitening on to compensate for the analog one. Otherwise we get a very bad shape of the PDH signal. Sorry Rana...
I forgot to say that the analog gain of the REFL55 channels has been reduced to 9db
I finally managed to get long stretches of PRMI lock, up to many minutes. The lock is not yest very stable, it seems to me that we are limited by some yaw oscillation that I could not trace down. The oscillation is very well visible on POP.
Presently, PRCL is controlled with REFL55_I, while MICH is controlled with AS55_Q. This configuration is maybe not optimal from the point of view of phase noise couplings, but at least it works quite well. I believe that the limit on the length of locks is given by the angular oscillation. I attach to this entry few plots showing some of the lock stretches. The alignment is not optimal, as visible from a quite large TEM01 mode at the dark port.
Here are the parameters I used:
MICH gain -10 PRCL gain -0.1
Normalization of both error signal on POP22_I with factor 0.004
Triggering on POP22: in at 100, out at 20 for both MICH and PRCL.
POP55 demodulation phase -9
MICH and PRCL control signal limits at 2000 counts
There is a high frequency (628 Hz) oscillation going on when locked (very annoying on the speakers...), but reducing the gain made the lock less stable. I could go down to MICH=-1.5 and PRCL=-0.02, still being able to acquire the lock. But the oscillation was still there. I suspect that it is not due to the loops, but maybe some resonance of the suspension or payload (violin mode?). There is still some room for fine tuning...
Lock is acquired without problems and maintained for minutes.
Have a nice week-end!