I was looking into why we don't have any light on the PSL pointing QPDs, and it turns out that it has been this way since ~June 29th 2012. I need to look back in the elog to see what was going on on the PSL table that day, but I suspect it has something to do with Yuta and I, working on the beat setup, since this is all very near that area.
Attached is a plot of the loss of signal on the QPDs.
We lost IP POS on the same day as we lost the PSL pointing. See 2nd attachment. The _S_Calc is the sum, and it almost looks like the light got near the edge of the diode and just kept falling off until it was gone. The sum started getting lower on May 16th, and then was gone on June 29th.
So far I've gone back as far as Jan 2012, but I still haven't found any data where we *did* have light on IP ANG. Sad.
UPDATE, UPDATE (like P.P.S.): June 29th was the day of the vent...see elog 6895.
There was one NOT MARKED SOS with two broken magnets on its face. This is labeled ???
While I'm not sure what specific optic this is, I think it's an older optic. (a) All of the new optics we got from Ramin were enscribed with their #. (b) This optic appears to have a short arrow scribe line (about the length of the guiderod), and then no scribe line (that I could see through the glass dish) on the other side. The new optics all have a long arrow scribe line, ~1/2 the full width of the optic, and have clear scribe lines on the opposite side.
As part of trying to figure out what is going on with the ASS, I wanted to figure out what filters are installed on which lockins.
Each "DoF"(1-6) has a zpk(0.1,0.0001,1)gain(1000), which is a lowpass with 60dB of gain at DC, and unity gain at high frequencies.
For the lockins, since there are so many, I made a spreadsheet to keep track of them (attached).
So, what's the point? The point is, I think that all of the LOCKIN_I filter modules should be the same, with a single low pass filter. The Q filter banks don't matter, since we don't use those signals, and the signals are grounded inside the model. The phase of each lockin was / should be tuned such that all of the interesting signal goes to I, and nothing goes to Q. The SIG filter modules seem okay, in that they're all the same, except for their band pass frequency. I just need to check to see what frequency the ASS scripts are trying to actuate at, to make sure we're bandpassing the correct things.
We are trying to figure out what the story is with the ASS, and in order to make it more human parse-able, we cleaned up the c1ass.mdl.
So far, we have made no changes to how the signals are routed. The local oscillators from each lockin still get summed, and go directly to the individual optics, and the demodulated signals from each lockin go through the sensing matrix, the DoF filters, then the control output matrix, and then on to the individual optics. So far, so good.
Much of the cleanup work involved making a big library part, which is then called once for PIT and once for YAW in the ass top level, rather than have 2 code-copies, which give Jamie conniptions. Inside the library part GoTo and From tags were used, rather than having all the lines cross over one another in a big spaghetti mess.
One of the big actual changes to the ass was some name changes. Rather than having mysterious "ASS-LOCKIN(1-30)", they are now named something like "ASS-PIT_LOCKIN_ETMY_TRY", indicating that this is in the pitch set, actuating on ETMY, and looking at TRY for the demodulated signal. The "DOF" channels are similar to what they were, although we would like to change them in the future.....more on this potential change later. Previously they were "ASS-DOF(1-10)", but now they are "ASS-PIT_DOF(1-5)" and "ASS-YAW_DOF(1-5)". This channel naming, while it makes things make more sense, and is easier to understand, means that all of the ASS scripts need to be fixed. However, they all needed updating / upgrading anyway, so this isn't the end of the world.
This channel name fixing also included updating names of IPC (shmem/dolphin/rfm things) blocks, which required matching changes in the SUS, RFM and LSC models. All 4 models (ASS, SUS, RFM, LSC) were recompiled and installed. They all seem fine, except there appears to be a dolphin naming mismatch between OAF and SUS that showed up when the SUS was recompiled, which presumably it hadn't been in a while. We need to figure this out, but maybe not tonight. Den, if you have time, it would be cool if you could take a look at the OAF and SUS models to make sure the names match when sending signals back and forth.
We also had a long chat about the deeper meaning of the ASS.
What should we be actuating on, and what should we be sensing? A potential thought is to rename our DOF channels to actual DoF names: input axis translation, input axis angle, cavity axis translation, cavity axis angle. Then actuate the dither lines on a cavity degree of freedom, sense the influence on TRX, TRY and an LSC PD (as is currently done), then actuate on the cavity degree of freedom.
Right now, it looks like the actuation is for individual optics, the sensing is the influence on TRX, TRY and an LSC PD, then actuate on a cavity degree of freedom. So the only change with the new idea is that we actuate in the DoF basis, not the optics basis. So the Lockin local oscillators would go through the control output matrix. This makes more sense in my head, but Jamie and I wanted to involve more people in the conversation before we commit.
The next question would be: how do we populate the control output matricies? Valera (or someone) put something in there, but I couldn't find anything on the elog about how those values were measured/calculated/came-to-be. Any ideas? If we want to dither and then push on isolated degrees of freedom, we need to know how much moving of which optics affects each DoF. Is this something we should do using only geometry, and our knowledge of optic placements and relative distances, or is this measurable?
Jamie re-redid the ASS model a few hours ago.
I have just compiled it, and restarted c1ass. (The model from last night is currently called c1ass3.mdl) I had to delete and re-put inthe goto and from tags for the LSC signal coming in from the shmem. For some reason, it kept claiming that the inputs using the from tags were not connected, even when I redid the connections. Finally deleting and dragging in new goto and from tags made the model happy enough to compile. Whatever. I'm going to let Jamie do the svn-ing, since he's the one who made the changes. Before I had figured out that it was the tags, I was concerned that the shmem was unhappy, so there was no signal connecting to the input of the goto tag, and that was somehow bad....anyhow, I recompiled the LSC model to re-create the shmem sender, but that had no effect, since that wasn't the problem.
The change from last night is that now the library parts are by DoF. There is only one matrix in each library part, before the servo filters. Now we can DC-actuate on a single mode (ETM or ITM, pitch or yaw), and see how it affects all 4 sensors (the demodulated signals from the lockins). We need to measure the sensing matrix to go from the several sensors to the servo input.
I wanted to try out the ASS tonight, but I wanted some kinds of screens thrown together so I would know what I was doing. Turns out screens take longer than I thought. Am I surprised? Not really.
They're probably at the ~85% mark now, but I should be able to try out the ASS tomorrow I think.
As we do not have legs for Trillium, I was advised to use shims to adjust the levels. However, they produce extra resonance at ~30 Hz + harmonics. Coherence is lost at these frequencies.
Brian Lantz / Dan Clark are looking around their lab to see if they forgot to ship the feet with the T-240. They had taken the feet off to put it in a pod.
I was trying to load some filters into the ASS so that I can try it out, but for some reason the filter banks aren't working - clicking the on/off buttons doesn't do anything, filters (which exist in the .txt file generated by foton) don't load.
I've emailed cds-announce to see if anyone has any ideas.
The PRM was pointing totally the wrong way, so there was no light on the oplev PD. I restored the PRM, turned the gains back to (0.15, -0.3) as per Yuta's elog 6952, and it seems just fine to me.
I want to check the data from last night / the weekend to see when the mispointing happened, but dataviewer can't connect to the fb, since Jamie is still working his magic. I'm pretty sure I restored all of the optics after Eric finished playing with MICH Friday night, but it's possible that I forgot one, I suppose. If it wasn't me, then I'm curious when it happened.
When the network / fb went bad this afternoon, I had been working on the ASS model, shortening the names of the filter banks to fix the problem from elog 7092. I wanted to finish working on that, so the ASS model is now rebuilt with slightly shorter names in the filterbanks (which fixes the problem of the filter banks not working).
I mentioned this to Jamie the other day, but here's the error that you get when the GoTo/From tags aren't working:
>>rtcds make c1ass
### building c1ass...
Parsing the model c1ass...
IPC 9 8 is C1:LSC-ASS_LSC
IPC 9 8 is ISHME
IPC 10 9 is C1:RFM-LSC_TRX
IPC 10 9 is IPCIE
IPC 11 10 is C1:RFM-LSC_TRY
IPC 11 10 is IPCIE
INPUT XARM_LSC_in is NOT connected
INPUT YARM_LSC_in is NOT connected
***ERROR: Found total of ** 2 ** INPUT parts not connected
make: *** [c1ass] Error 255
make: *** [c1ass] Error 1
I don't know why these tags weren't working, but there was a GoTo tag on the output of the LSC shmem block, and then Froms on each of the XARM_LSC_in and YARM_LSC_in. The other day I played around with a bunch of different things (grounding inputs, terminating outputs, whatever), but finally replacing the tags with identical ones freshly taken from CDS_PARTS made it happy.
I wrote new setup, on and off scripts for the arm ass. They take the arm as an argument, so it's the same script for both arms. Scripts are in ...../scripts/ASS/ , and have been checked in to the 40m svn.
So far the on script doesn't really do anything, since I haven't chosen values for the CLKGAINs of the lockins. The old values were 30 for lockins 12, 14, 27, 29 and 250 for lockins 7, 9, 22, 24. Unfortunately, I have no memory of which lockin means what in the old numbered system. I'll have to look that up somehow. Or, just dither the optics using some value and look at the spectrum to see the resulting SNR and just pick something that gives me reasonable SNR.
I modified the ASS model slightly:
* Added an overall gain to the ASS_DOF2 library part, between the matrix and the servo inputs so we can do soft startups. Self - remember that the main ASS screen needs to be modified to reflect this!
* Rearranged the order that the demodulated signals go into the matrix. I hadn't paid attention, and the old ordering had the transmission (TRX/TRY) demod signals interleaved with the LSC demod signals. I've changed it to be all the TR signals, then all the LSC signals. I think this makes more sense, since we will use these inputs separately, so now they're on different halves of the matrix.
Previously, medmrun didn't accept arguments to pass along to the script it was going to run. Jamie has graciously taken a moment from fixing the computer disaster to help me update the medmrun script.
Now the ASS scripts are call-able from the screen.
Jan and Manasa are going to elog about their work later, but it involved putting a BS/window/some kind of pick off in front of the MC Trans QPD, so the total light on the MC Trans QPD is now ~16000 rather than ~26000 counts. I changed the threshold in the MC autolocker to 5000, so now the MC Trans PD must see at least 5000 counts before the autolocker will engage the boosts, WFS, etc. Actually, this threshold I believe should have been some several thousand value, but when I went in there, it was set to 500 counts, for low power MC mode during a vent. It had never gotten put back after the vent to some higher, nominal value.
I turned on the ASS, without closing the loops, to try to measure the sensing matrix.
The Yarm was locked (Eric did a nice job earlier - he'll ELOG ABOUT IT before he goes home!), and I used an LO CLKGAIN of 300 on all of the TRY Lockins. Then I put on and took away a 10% offset in pitch, but it's almost impossible to see the difference.
The attached is a truly awful screenshot, but you can kind of see what's going on. The big steps are me increasing the LO gain, but around "0" on the x-axis I changed the pitch offset from 10% away to nominal. Since there are such big oscillations, the change is basically non-existent. Grrrr. I'll look at it again tomorrow, since I have an exiting bike ride home ahead of me....
From the log, I couldn't understand what has been done.
The procedure we should perform is
Then you can start measuring the sensing matrix. At which part did the attempt fail?
Cavity started out aligned pretty well, but not 100%. Transmission was ~0.8 . Perhaps this was part of the problem.
I realize now that you mention it, it was totally amateur hour of me to only look at the lockin outputs on StripTool (plus POY and TRY on Dataviewer), and not look at TRY on DTT...or any spectra at all. Not so intelligent. I could see some fluctuation of TRY on Dataviewer that corresponded to me turning on the oscillators, as well as the spot wiggling on the camera view of ETMYT a teeny bit.
When applying a 10% misalignment to ETMY Pit (by adding 0.1 to the Pit components of the output matrix, as is done in the MC spot position calibration), I could see that there was a small jump in the StripTool trace, but it was much smaller than the ambient fluctuations of the output.
I just looked back and realized that I must have forgotten to add my screenshot, but it's saved on a desktop on Rossa. It would be better if I had attached the data, but from that you see that the average of the lockin output signal didn't change very much in the last several minutes of the measurement, but the fluctuations (no misalignment offsets) are pretty big, maybe ~10% or 15% the size of the signal. Then when I added the misalignment to one mirror (ETMY PIT), there is a very small jump in the lockin signal, but it is much, much smaller than the size of the ambient fluctuations. Perhaps a long average would result in a "real" value, but by looking by eye, I can't see a discernible difference in the average value of the lockin outputs.
My plan is to do as you say, dithering all 4 optics, and misaligning a single optic's single DoF (Pit or Yaw), and seeing how that misalignment affected each of the sensors (the lockin outputs). Then put that DoF back to nominal, and misalign a different DoF, rinse and repeat.
Okay, so this is a little stream-of-consciousness-y, and you're going to think I'm really dumb, but I just realized that I haven't set the phase of the lockin demodulators yet. So I think I need to dither the optics, and go through each of the sensors, and adjust the phase until the peak in TRY in DTT is maximized for the I phase, and minimized for the Q phase (since we use the I-output). Bah. Bad Jenne.
Once you've got C1:LSC-TRY_OUT as large as possible, you've locked the cavity.
Both the transfer function and the coherence look good above roughly 30 Hz, but do not look correct at low frequencies. There's also a roll-off in the measured transfer function around 200 Hz, while in the model the magnitude of the transfer function drops only after the corner frequency of the cavity, around several kHz. I have attached a plot of the roughly analogous transfer function from the DARM control loop model (the gains are very large due to the large arm cavity gain and the ADC conversion factor of 2^16/(20 V) ). The measured and the modeled transfer functions are slightly different in that the model does not include the individual mirrors, while the excitation was imposed on ITMY for the measurement.
The next steps are to figure out what's happening in DTT with the transfer function and coherence at low frequencies, and to understand the differences between the model and the measurement.
The cavity is actually "locked" as soon as the feedback loop is successfully closed. One easy-to-spot symptom of this is that, as you mentioned elsewhere in your post, TRY is a ~constant non-zero, rather than spikey (or just zero). Once you've maximized TRY, you've got the cavity locked, and the alignment optimized.
We didn't get to this part of "The Talk" about the birds, the bees, and the DTTs, but we'll probably need to look into increasing the amplitude of the excitation by a little bit at low frequency. DTT has this capability, if you know where to look for it.
It would be great to see the model and your measurement overlayed on the same plot - they're easier to compare that way. You can export the data from DTT to a text file pretty easily, then import it into Matlab and plot away. Can you check and maybe repost your measured plots? I think they might have gotten attached as text files rather than images. At least I can't open them.
Koji pointed out that I was being silly, and rather than actually misaligning the optics (by, say, changing their IFO Align sliders) I was changing the location of the actuation node by changing the coil output gains. Now I see nice signals at the I_OUT of each of the demodulators (so far I've only looked at the YARM).
I've measured and inverted the matrix by taking the nominal values of the demodulator outputs when the optics are all by-hand optimally aligned, then one-by-one misaligning an optic's angle (pitch or yaw), and looking at the demod outputs that result. Repeat with each misalignment DoF for each of the 4 rows of the matrix. Then I set the pit/yaw coupling elements of the matrix to zero. Then invert the matrix, put it in, and see what happens. So far, the yaw DoFs converged to zero, but the pitch ones didn't. I'll play with it more and think some more tomorrow.
Simplant for ETMX was left on, so I didn't have control of ETMX. Not cool. The IFO should be left in it's 'regular' state (all optics restored to saved alignments, no simplant, LSC/ALS/ASS loops off) if you're not actively working on it.
What this did point out, however, is that we need a big ol' indicator on the IFO_ALIGN / LSC / Watchdog / Overview screens to indicate that simplant is on for a particular optic, or whatever simplant might be controlling that takes away 'regular' control. I probably would have continued being frustrated and confused for a lot longer if Eric didn't mention that simplant could have been left on. Thanks Eric!
Symptoms, which perhaps would have eventually pointed me to simplant, were that there was some weird moving beam on the AS camera that was flashing fabry-perot fringes, and the POX signal looked like junk. After some looking around, I noticed that ETMX, while it claimed to have all the damping loops on, and the oplev on, was swinging a lot (rms levels of 4 - 7, rather than the usual < 2 ). I said something out loud, and Eric suggested looking at Simplant. After putting Simplant back to Reality, things are back to normal.
I'm trying to lock / align the Xarm, and POX 11 I looks funny sometimes.
I attach 2 screenshots so you can see what I mean. I'm leaving them uncropped so that you can see the only thing that has changed is the LSC enable / disable button.
PRM, SRM, ITMY, ETMY all misaligned. BS, ITMX, ETMX aligned so that most of the time I can't lock better than 04, bad in yaw, but very occasionally I'll get lucky and catch a 00. When the LSC enable switch is ON (2nd attachment), the POX signal (green trace in dataviewer in both attachments) looks almost square-ish, and definitely funny. It doesn't seem to correspond directly to flashing in the cavity (red trace in dataviewer in both attachments). However when I disable the LSC, POX goes back to looking normal - 1st attachment. Right around -5 seconds in the 1st attachment, I disabled the LSC.
I don't really know what this means.
When signals are transmitted between the models running at different rates, no AI or AA filters are automatically applied. We need to fix our models.
This is known, but we just haven't fully groked it yet. We need to look closely at every place we have IPCs between models running at different rates. The sender has no information about receivers, so it can't reasonably do anything to pre-filter the signal on it's own.
So for transmission from:
*sigh* This is one of those things that I meant to take care of months ago, but haven't yet. I agree that it needs doing. It's been on my whiteboard to-do list for a long time now. Bad Jenne for not taking care of it.
I'm proposing larger optical tables at the ends to avoid the existing overcrowding. This would allow the initial pointing and optical level beams to set up correctly.
The existing table is 4 x 2 would be replaced by 4' x 3' We would lose only ~3" space toward exist door.
I'm working on the new ACRYLIC TABLE COVER for each end that will cost around $4k ea. The new cover should fit the larger table.
Let me know what you think.
I'm not sure I see the motivation. The tables are a little tight, but not that much. If the issue is the incidence angle of the IP and OPLEV beams, then can't we solve that just by moving the table closer to the viewport?
The overcrowding alone doesn't seem bad enough to justify replacing the tables.
Steve pointed out to me (this is not in his original elog, although you can see it in the photo if you look closely), that we can't really move the table legs any closer to the chamber. We have maybe 3" of clearance between the table leg and the blue support tube that supports the bottom of the stack. Therefore, we can't just
So Steve's proposal is to leave the legs exactly where they are, and just put a larger table on those legs. This leaves 9" unsupported on the chamber side, and 3" unsupported on the far side. The tables are 4" thick.
Steve also mentions that we will lose 1.5" on all 4 sides of the table, with the new acrylic boxes, so we'll be down to 1'9" unless we get the larger table, in which case we'd have 2'9", and 3'9" on the long direction.
I would like to see a sketch of the end tables, so we can see if 1'9" x 3'9" is enough. Manasa is working on a new end table layout in parallel to the ringdown stuff. If we're actually concerned about the input angle of the oplevs, then to fix that we need to either get the bigger table and hang it off the edge of the legs, or perhaps as Dmass suggested, get a "doggy cone collar", and give ourselves a larger opening angle of access to the viewport, from the current table location.
I went down to the Xend table to look at it to understand Steve's proposal, and I noticed that the doubling crystal's heater's cable is mushed between the table's edge and the black table cover wall. This made me sad, so I disabled the heater, turned it off, then unplugged the cable from the back of the controller. I tried to re-route the cable through the hole in the black table cover wall, but going that way the cable is ~1 foot too short. So I put it back the way it was, but used a totally hacky solution to prevent the cable from being mushed. I put a dog clamp right at the edge of the table so it is pushing on the table cover wall a little bit, to give the cable space to get out. This is very mickey mouse, and kind of lame. But we either need to make a cable extension, or somehow get the heater controller to sit much, much higher under the table.
I plugged the heater controller back in, and turned it back on to the same setpoint that it was at (I think 37.5C). It's probably warm by now, but when I turned it back on, the heater's actual temp was 33C.
I'm ~30% of the way through implementing LSC whitening filter triggers. I think that everything I have done should be compile-able, but please don't compile c1lsc tonight. I haven't tested it, and some channel names have changed, so I need to fix the LSC screen when I'm not falling asleep.
Also, Rana pointed out that we may not want the whitening to trigger on immediately upon acquiring lock - if there are other modes ringing down in the cavity, or some weird transients, we don't want to amplify those signals. We want to wait a second or so for them to die down, then turn on analog whitening. Jamie - do you know how long the "unit delay" delays things in the RCG? Do those do what I naively think they do? I'll ask you in the morning.
Koji just found the emergency exit door unlocked again. NOT GOOD.
We have determined that if you use the emergency door to enter the lab, it leaves the door unlocked, unless you go back outside and deliberately lock it. This means that someone has been using the emergency exit as a regular entrance.
It's fine to leave by that door, but you should make a habit of entering through the regular door. Using the back door as an entrance is a special case situation, when they have the main door blocked.
After Rana and Yoichi tweaked the arm locking filters, we have had some pretty awesome lock stretches. 5-day minute trend.
The videocapture.py script is now in ...../scripts/general/ , along with the videoswitch.
Also, there's a button gui on the VIDEO medm screen to capture different camera views.
Rana points out that we haven't had fast channels for PMC (trans, refl, pzt), input laser things, more FSS things since the upgrade. Bad.
I (for the first time personally) locked the FPMI. I have data for the POX11I, POY11I, AS55Q error signals for each arm and the Michelson (JenneLockingDTT/FPMI_error_signals.xml), but I haven't calibrated the data yet - Self: do this! FPMI with arms locked using IR has been happily locked for a long time now - this is good.
From elogs / my old MICH calibration script, I have the plant calibrations of:
POY: 1.4e12 cts/m
POX: 3.8e12 cts/m
AS55: 9.4e9 cts/m
MICH has FM 5 on, Xarm has FM4-10 all on, Yarm has FM3-10 all on.
Post note: FM 3 - the integrator - for Xarm wasn't triggered. It turns on just fine, so I've got it triggered just like Yarm.
Also, just remembered - I turned off the XARM TRX power normalization, since it was causing crazy numbers in the xarm servo. The XARM locked pretty easily after that.
The green beam for the Xarm is flashing a pretty nice 00 mode, but isn't catching lock.
The green beam for the Yarm isn't flashing at all that I can tell from just the camera views. I don't have energy to start this sometimes monumental task tonight, so I leave it for Future Jenne to work on.
I installed pyepics version 3 (http://cars9.uchicago.edu/software/python/pyepics3/overview.html) in ..../scripts/pylibs . I also added an "epics.conf" file to /etc/ld.so.conf.d/ , which points to the place in /ligo/apps/epics/base/lib/linux-x86_64/ where the DLLs live. All .conf files in /etc/ld.so.conf.d/ get included in the path, so python should always automatically be able to use epics now, after you "import epics" in a script.
This is supposed to give us direct channel access to all epics channels, rather than using Yuta's wrapper scripts for ezca stuff. I was going to write a tdsavg equivalent using camonitor, since it's unclear whether tds tools are being supported anymore.
However, I'm not getting it to connect to the server that serves epics, so I can't get the values of any channels. All of the info in the link above assumes that you automatically get a connection, and I'm out of ideas right now of things to try. Does anyone else have any ideas?
POY was looking funny, and the YARM wasn't locking. It looked like POY wasn't seeing any light at all. I went to check, and it looks like a beam dump got accidentally placed in the POY path during oplev adjustments this morning. POY is back, locking continues.
While meditating on other things, I have noticed / found the following today:
YARM ASS works okay. Yesterday I measured the sensing matrix for the ASS for both arms (although I forgot to copy one of the matrix elements to my text file for Xarm - needs remeasuring). I put the Yarm matrix in (after appropriate inversion, only non-zero pitch-to-pitch, yaw-to-yaw elements). I turned on the Yarm ASS, and the yaw converged pretty quickly (couple of minutes), with gains of -1 in the servos, overall gain of anywhere between 0.005 and 0.010. The pitch took much longer, and I had to 'pause' several times by turning off the overall gain for the yarm ass when the MC lost lock (which has happened several times tonight - unknown cause). Eventually, the pitch settled out, and quit changing, but the lockin outputs weren't zero, even though the error signal for the servos were almost zero (gains for the pitch servos were -0.5, overall gain ~0.005 was better than 0.01 - higher gain caused oscillations in the lockin outputs). I think this means that I need to remeasure the yarm pitch ass matrix. It's still much, much faster to just turn on the dithers, watch the striptool of the lockin outputs, and align the cavity by hand.
I think the ETMX Trans camera view is clipped a little bit. I went down there, and it doesn't seem to be on the last optic before the camera, and moving the spot on the camera doesn't change the shape of the image, so I don't think it's on the camera. We should look into this, since it's either clipping on the BS that separates some camera beam from the TRX beam, or TRX is getting a clipped beam too. If the clipping is any earlier in the Trans path, the Trans QPD could also have some clipping. This requires investigation. The xarm trigger needs to be reset/disabled so we don't lose lock every time we block the TRX beam (as was happening to me).
XARM really doesn't like to relock unless the POX whitening is turned off. Good flashes, doesn't really catch (10+ min waiting (while working on Yarm stuff) ). After turning off the whitening, it catches almost immediately. Even though it's on the to-do list to rethink the tuning of our whitening, we should probably implement the whitening triggering now anyway. It'll make things easier.
The double integrator that Rana implemented in the X and Y arm servo filters last week take 8 seconds to turn off (due to Foton settings), so even though they are triggered to turn off immediately upon lockloss, they sit around and integrate for 8 seconds, so have huge signals. If the cavity flashes and the locking trigger engages during that 8 seconds, we send a huge kick to the ETMs. I'm modeling the response of the filters to an impulse and noise, particularly in the case of ramping on the double integrators. The problem is that a flat filter has 0deg phase, but the double integrator has 180deg phase at low frequencies, so there's some weird sign flipping that can happen as we ramp - this is part of what I'm modeling.
MC is losing lock unusually often tonight. Everything on the servo board screen looks normal (which is good since that's all set by the autolocker). I just disabled the test exc in, but that's been left enabled for a while now, and it hasn't (I think?) been a problem since there shouldn't be anything connected to the board there. PMC transmission is a little low, 0.816, and FSS is starting to get near -1 on the slow actuator adjust, but we've seen locking of the PMC problems around -1.5 or -2 of the FSS, and the adjust value was at -0.8 earlier tonight and we still had MC locking problems. I have had the seismic channels open on Dataviewer for the last several hours, and I'm not seeing any spikes in any of the Guralp channels which correspond to the times that the MC loses lock. BLRMS don't seem particularly high, so MC lockloss cause is still a mystery for today.
The ETMX monitor selector on the VIDEO screen seems not to be switching the actual camera that's shown on the monitor. Using the script command itself works, so my screen is wrong.
Last week, Rana changed the integrators in the arm LSC servo filters to be double integrators with complex poles.
Yesterday, I found that using the "timeout" feature of Foton (at filter ON/OFF request, waits for zero crossing, or T seconds, whichever comes first) is useful for turning on the integrators, but bad for turning them off. When we're locked, the error signal is oscillating around zero, so there is often a zero crossing. When we lose lock, we want to turn off the filter immediately. But, as soon as lock is lost, the input signal gets large, and doesn't often cross zero, so the filter waits 8 seconds until actually turning off. If the arm flashes any time during that 8 sec, we send a big kick to the optics.
An alternative option could be ramping the filter on. However, since the double integrator has -180deg phase at low frequencies (until the poles at ~5Hz), the transition between no filter (0deg phase) and integrator on could be problematic. I simulated this, and find that for the very beginning of the ramping process, we would have a problem.
The filter is defined as: NoFilter * (1 - R) + Integrator * (R), so for R=0, the integrator is off, and for R=1, the integrator is fully on. R can be any value [0,1].
The first figure is the time series (1 second, 16kHz), ramp goes from 0->1 or 1->0 in 1 second:
The second figure is bode plots for selected values of R:
As R gets smaller and smaller, the notch goes to lower frequency, and becomes higher Q. So perhaps ramping is not a good answer here.
What if we go for single or triple integrator, to get rid of the (+1) + (-1) problem?
It seems as though there is something funny going on around ~1.5 Hz, starting a little over an hour ago.
We see it in the BLRMS channels, the raw seismometer time series, as well as in various suspensions and LSC control signals. It's also pretty easy to see on the camera views of all the spots (MC, arms, transmissions....AS is a little harder to tell since it's flashing, but it's there too).
The plots I'm attaching are only for ~10min after the jump happened, but there has been no change in the BLRMS since it started. Usually, we'd see an earthquake in all the channels, and even big ones ring down after a little while. This is concentrated at a pretty narrow frequency (some of Den's plots for later have this peak), and it's not ringing down, so it's not clear what is going on.
Here is a whole pile of plots. Recall that the T-240 is plugged into the "STS_3" channels, and we don't have BLRMS for it, so you can look at the time series, but not any frequency specific stuff.
We took a look at the Xend green, and we weren't able to make it lock. We improved the alignment a little bit, and when we looked at the error signal, it looked nice and PDH-y, but for whatever reason, the cavity won't catch lock.
While aligning the green to the arm, Jamie noticed that the reflection from the intracavity power (not the prompt reflection) was not overlapping with the input beam or prompt reflection. This means that the cavity axis and the input green beam were not co-linear. I adjusted the BS and ITMX to get the IR transmitted beam (which had been near clipping on the top edge of the first (2 inch) optic it sees out of the vacuum) back near the input green beam spot on the combining beam splitter. Then we continued tweaking the green alignment until we saw nice TEM00 flashes in the cavity. The SNR of the error signal increased significantly after this work, since the cavity buildup was much higher. But alas, still no lock.
I tweaked the alignment of ITMX and ETMX a teeny bit to get the TEM00 flashes back (the work in the previous elog was pre-dinner, so it had been a few hours), then took a screenshot of the error signal and refl dc power on the photodiode for the green xend setup.
The error signal is certainly noisy, although I think when Jamie and I were looking at it earlier this evening, the SNR was a little better.
I need to look at the modulation depth, to see if it's correct, ... maybe lock the Xarm on IR and scan the green laser PZT to check the sideband heights.
I should also check to make sure that the PD is powered, and the gain is high enough (currently the PD gain is set to 20dB). Earlier today, when I set the gain to 30dB, Jamie said that it was saturating, so I put it back down to the 20dB where we found it.
Still no lock of the green though :(
Edit: realized I was bad and didn't label the traces on the plot: green is refl dc power, blue is demodulated error signal.
Friday / pre-vent:
[done] Align the MC mirrors for the incident beam so that the mirrors can be the alignment reference [Koji]
[in progress] Center spots on MC mirrors [Jenne]
Put beam attenuator optics (PBS + waveplate) on PSL table, realign input beam to MC mirror centers
[In progress] See if we can design a set of nuts and bolts to use at bottom of tiptilt optic ring, to do small adjustments of pitch alignment [Steve]
After doors open:
Use CCD (Watek, with AGC on) to take images of everything we can think of, to see current status of clipping
Check that we get through the Faraday without clipping
Move PZT1 and MMT mirrors to get good spot positions on PR3, PR2. Make sure we're clearing the Faraday's housing
Install dichroic optics, perhaps completely readjust pitch alignment of those tiptilts (we will measure the spares later, and call that good enough for our phase mapping).
Use some kind of oplev setup to check pitch alignment of PR2, PR3.
Tweak (if necessary) PR2 & PR3 pitch to go through center of PRM, BS, hit center of ITMY
Check that we're not clipping on the BS cage anywhere
Use CCD to take images with Sensoray of everything we can think of, to confirm we don't have clipping anywhere. Want to see the edges of the beam on the targets, which would mean that the beam is hitting the center of the optic. If necessary, we'll stay open an extra day to get good camera images everywhere, so we have a good record of what's going on inside.
Note: While having good arm alignment would be good, we're willing to sacrifice some arm alignment to have good DRMI alignment, since we're re-venting and installing the new active tiptilts in another month or so.
Things I'm leaving for Jamie-the-Vent-Czar to plan:
Order of door opening
Beam dump assembly and placement
I am getting closer with the MC spot centering. I had everything but MC1 really great, but then I tweaked MC1's pointing, and things all went to hell.
I have to go home to let Butter out, but I'll be back tomorrow, and I'll try to get back to where I was in the 2nd to last measurement in the plot below.
I recenterd the WFS after moving the input beam, so that the beam was hitting the WFS at all.
We need to re-look at this new MC autolocker stuff, and the new MCL filters.
MC2 is getting kicked up (sometimes the watchdog trips, sometimes it just comes close) pretty regularly. I'm not sure yet what is causing this, but we need to deal with it since it's pretty obnoxious.
We are being riddled with earthquakes. Brawley, CA (~150 miles from here) has had 9 earthquakes in the last hour, and they're getting bigger (the last 4 have been 4-point-somethings). I may try to come back later, but right now the MC won't stay locked for the ~5 minutes it takes to measure spot positions. Koji and Jamie said they were coming in today, so they can call me if they want help.
Steve, do not vent tomorrow morning! We are still not prepared, and will not finish the preparation tonight. Hopefully we can finish the prep tomorrow, and then vent Tues.
Things we need to do before the vent:
MC spots centered [Jenne, tonight]
Use PZT2, BS to hit ~center of ETMs.
Realign arms, measure spot positions.
Make sure BS, ITMs are good - we want a good AS spot since we'll likely have to adjust some AS optics while we're inside
Insert attenuation optics, recover MC trans by rotating PBS cube to translate beam slightly
After shaking ITMX by the alignment bias in yaw, it came back.
As ETMX seems to be largely misaligned yaw (and did not come back with the alignment impact),
the condition of the magnets are not clear. Only the side OSEM is responding nicely.
It looks like we may lost 1 (or 3 ) magnets? Do not panic, it's not for sure
I tried to take some photos through the window of ETMX's chamber, to see if I could see any magnets. What we have learned is that Jenne is still not the world's best photographer. I was holding the camera at ~max zoom inside the beam tube between the table and the window, so that's my excuse for the photos being fuzzy. The only thing that I can really conclude is that the magnets look like they are still there, but Jamie thinks they may be stuck on the PDs/LEDs (now looking at the photos myself, I agree, especially with UL and LR).
It looks like the best thing to do at this point, since Koji already tried jerking ETMX around in yaw a little bit, is just wait and open the door, to see what's going on in there. I posted the photos on Picasa:
I propose that, if the magnets are broken, we pull the ETM out of the camber and fix it up in the cleanroom while we pump back down. This would restrict us from doing any Xarm work, but will force me to focus on DRMI, and we can put the ETM back when we vent to install the tip tilts.
The MC REFL path was checked. ==> Some clippings were fixed. MC WFS is working now.
- MC was aligned manually
- The steering mirror for the WFS and camera was clipping the beam. => FIxed
- The WFS spots were realigned.
- There was small clipping on the MC REFL RFPD. ==> Fixed
We have figured out that some of these measurements, those with the WFS off, were also not allowing the dither lines through, so no dither, so no actual measurement.
Jamie is fixing up the model so we can force the WFS to stay off, but allow the dither lines to go through. He'll elog things later.
Jamie and I have the MC spots centered. We did the normal move the input beam, realign jazz for a while, then when we got close, used the "move MC2 spot" scripts to get the MC2 spot back to ~center.
This was way easier when the measurements were real, and not just noise. Funny that.
The dark blue spot is the farthest from 0 in pitch, and it is 1.04mm. The cyan and yellow we've done a pretty good job of getting them equally far from zero. Since we aren't translating the beam, we can't get better than the point at which the cyan and yellow curves cross.
PMC transmission started going down this afternoon, around 3pm-ish. Right now it's 0.775, which is very, very low. The new MC locking stuff is engaged, so it's not the FSS slow servo's fault.
EDIT: I just realized that the limit of 0 counts output of the MC2 MCL filter bank was still engaged, from a time earlier this afternoon when I had switched back to the old servo, so there was no feedback going back to keep the slow drift of the laser in check. PMC trans isn't coming back instantly, so I'll check it again when I come in tomorrow.
We have now reduced the power being input to the MC from 1.25W to 10mW, and changed out the MC refl BS for a mirror.
The power was reduced via the PBS we introduced in Entry 7295.
While we were in there, we took a look at the AS beam, which was looking clipped on the monitor. Jenne felt that it appears that the clipping seems to be occurring inside the vacuum, possibly on the faraday. This will be investigated during the vent.
I stopped the regular MC autolocker and told the crontab to startup the low power Mc autolocker on op340m. Also, since we now have the new MC2 transmission setup, the power that gets to the 'regular' MC trans PD is lower, so I've lowered the lock threshold to 50 counts, from 100 counts.
We installed a Half Wave Plate -> Polarized Beam Splitter -> Half Wave Plate in the PSL beam line, immediately after the EOM, to be used for attenuating the beam when we vent, as in Entry 6892.
It was illuminating to discover that the optics labeled QWP0-1064-10-2 are indeed half wave plates, instead of quarter wave plates as QWP suggests.
The PBS transmits "P"/Horizontal polarization, but the beam coming from the EOM is "S"/Vertically polarized, and we want to keep that, since we do not want the beam attenuated quite yet.
So, we use the HWP to rotate the P from the EOM to S, so that the majority of the power passes through the PBS. The second HWP then rotates the transmitted S back into P, which continues to the mode cleaner. When we want to attenuate, we will simply rotate the first HWP to change the proportion of S polarized light that will pass straight through the PBS and towards the mode cleaner.
After setting the proper HWP angles, we aligned the PBS via minimizing the MC reflection.
Since we have not yet attenuated the power, we have not yet changed the BS for the MC reflection, since this would damage the PD. The beam splitter will be changed out for a 100% reflectivity mirror to increase the power to the PD when we do.
Before we did this, I centered PSL POS and ANG, which gives us a reference of where the PSL beam was good when the MC spots were ~centered. There had been a beam dump blocking them, possibly from the last time we put in the power attenuator optics. This beam dump was moved a little to be out of the way of the PSL QPDs, and the PBS placed closer to the lens after the EOM, so that the PBS reflected beam is dumped. However, we should not remove that razor dump when we remove the attenuation optics, since it is also dumping a stray IR beam from the PSL QPD pickoff windowd.