I put in a new version of the modelled plot. I figured out a different way to keep things generic so the same script can be used for other sites, but writes the names in the same format as the measured matrix, so the correct order is preserved.
The REFL11 measurement is consistent with the one in elog 8648 (data taken a few days earlier), within the error bars. My goal for tonight is to hopefully get the POP path back in order, so that I can lock the PRMI again, and can measure again if I want.
The error bars for each sensor are only taken once (with no drive, so it's the noise in the "dark" sensor). I take 6 "dark" measurements for each sensor, and get the stdev. Then I use that and propagate it through for each measured sensing matrix element. So, the PRCL and MICH error bars for REFL11 were created from the same standard deviation, and propagated in the same way, but the values plugged into the partial derivative of the function were different for PRCL and MICH.
(wikipedia - propagation of uncertainties)
Also, to answer an emailed question via the elog, the "0 degree" axis of the plots is the 0 demod phase axis, which corresponds to the I output of the demod boards (the I input to the RFPDs, before the phase rotation). The "I" axis that I've drawn is the current demodulation phase that we have, which corresponds to the I_ERR output of the RFPDs after the phase rotation, which is the PD_I signal that goes into the LSC input matrix. I draw this to help us see if our current demod phase is well tuned or not.
Yes, the MICH and PRCL signals are not at all orthogonal in the REFL33 sensor. I think this is because our modulation frequency was chosen to be good in the case of the full DRFPMI IFO, not the corner IFO cavities. As I calculated in elog 8538, the ideal frequency for the PRMI is 18kHz larger than our current modulation frequency.
For the plots below, note that 11.066134 MHz is our current actual modulation frequency, and 11.0843 MHz is my calculated ideal modulation freq.
Model, using our current modulation frequency, and the designed PRCL cavity length (same as elog earlier today):
Model, using the "ideal" PRMI modulation freq, and the PRCL cavity length used in elog 8538, where I calculated that number (a few cm different than the design PRCL length):
You can see that if we could use a better frequency, we would get much, much better signal separation. Since our modulation frequency choice is related to our vacuum envelope constraints (we can't make the arms of a length that will have the sidebands exactly antiresonant when the arms are locked on the carrier), I hope that this will not be a significant issue in aLIGO.
I have placed the lenses and the PDs in their new positions on the POP path. As Koji had pointed out to me in reply to elog 8663, what really matters to get the beam size I want on the QPD is the distance between the lenses, and not so much the absolute position of the lenses (since the Rayleigh range of the POP beam coming out of the vacuum is so long), so I left the 2" lens in place, and made the distance between the Y1 and the QPD's lens 35 cm.
I didn't move the camera very much, mostly just enough to get the beam centered on the TV. I need to check where this is in terms of the beam shape, to see where I should move it to, so that I'm getting useful beam motion information by looking at the camera.
The steering mirror for the POP110 PD is still between the camera and the steering mirror for the QPD, there's just much less space between those 3 elements than there was previously. I put the POP110 PD's lens and the PD itself in such a way that the PD is at the focus.
The PD which used to be the ASC razor blade PD has been put back in the cabinet. The cable that was plugged into it was being used for POPDC. I will need to switch things back so that POPDC is once again coming from the POP110 PD. Also, I need to bring over the power supply for the QPD, and lay some cables between the supply/readout box and the IOO chassis (where Jamie has freed up some channels for me).
Also, while I was on the POX table, I was reminded that we need to deal with the ITMX oplev situation, which Gautam detailed in elog 8684. I will ask Steve to take care of it when he's back from vacation.
... I need to ... lay some cables between the supply/readout box and the IOO chassis (where Jamie has freed up some channels for me).
I have made 3 dongles that go from 2-pin lemo to BNC so that I can connect the 3 QPD signals (X, Y, Sum) to the IOO ADC (Pentek Generic board in 1Y2, which also has the MC channels).
The interface board with the 2-pin lemo connectors doesn't have anything in the DCC for the document number (D020432), so I asked BAbbott, and he said: "After a bit of searching, I found that on psage 2 of D020006-A-pdf ( https://dcc.ligo.org/LIGO-D020006-x0 ), Pin 1 of each LEMO connector is the + leg, and pin 2 is the - leg. This means that you should connect the center conductor of the BNC (if you don't have any 2-wire twisted-pair cables around) should be connected to pin 1 of the LEMO, and the outer conductor should be connected to Pin 2. According to http://il.rsdelivers.com/product/lemo/epg0b302hln/2-way-size-0b-pcb-mount-socket-10a/1305621.aspx Pin one is the top one on the right-angled LEMO." According to page 50 of the lemo data sheet, pin1 is the one with the mark next to it, when you are looking at the solderable end.
I have made some plots of the sensing matrix (PRCL / MICH amplitude ratio, and relative angle) versus Schnupp asymmetry for all the configurations that involve the power recycling cavity. I am still meditating on what they mean for us, in terms of whether or not we should be changing our Schnupp asymmetry.
The Schnupp asymmetry scan starts at 1mm, rather than 0. Also, recall that our current Schnupp asymmetry is 3.9cm.
Power not on to the POP QPD yet though. Also, still need to reconnect POPDC.
The plots, with a log y axis
I have done a quick update of the IFO_ALIGN screen's save and restore scripts, so that we can now also save, restore, and view the saved values for the input tip tilts.
In the past, there was an "if" statement to check if the optic was a PZT, and if so, define the alignment channels accordingly (since all the SOS suspensions have the same format for the name, and the PZTs were the odd ones out). I have removed the mention of PZTs, and replaced the if statement with an "if TTs" statement, and put in the correct channel names (C1:IOO-TT#_PIT_OFFSET, and the same for YAW).
Also, I caught a bug in the code, which explains some confusing behavior that I had seen in the past. When deciding if the restore script should take small steps or just do a big step, it looked at the difference between the saved value and the current value of the slider. It was *not* looking at the absolute value of the difference. So, if you had misaligned a slider by hand, and it was in the opposite direction of what the misalign script does, the restore script wouldn't realize that the optic needed to be restored in small steps. I have now fixed this bug for both pit and yaw cases of the restore script.
I am proposing a model name change. Currently, we have an "ASS" model, but we do not have an "ASC" model.
The ASS is currently using ~17 of 60 available microseconds per cycle. So, we have some cpu overhead available to put more stuff on that cpu. Like, say, ASC stuff.
So, my proposal is that we change the ASS model name to "ASC", and put all of the ASS-y things in a top_names block, so we retain the current channel names. The IOO top_names block that is in the current ASS model (which is there to send signals to the LSC DAC for the input tip tilts, even though the names need to be IOO) should obviously stay on the top level, so that things in there retain their names.
Then, I can make a new top_names sub-block for ASC-like things, such as the new POP QPD.
Inside the ASC block (in the ASC model), I'm currently thinking something simple will do..... QPD inputs, going to a matrix, which outputs to the filter banks in the "length" degree of freedom basis (PRCL, SRCL, etc), then another matrix, going to the ASC suspension paths.
So, for example, the POP QPD pitch would go to the PRCL_PIT filter bank, and then on to the PRM_ASCPIT path in the SUS screen.
Or, in another example case, IPPOS yaw would go to an input pointing filter bank, then on to TT1's yaw slider.
EDIT: After a few minutes of thinking, I think I also want triggering, and perhaps filter bank triggering, in the ASC model. One of the reasons Koji has been pushing for the new automation system is that when the PRC fell out of lock, the ASC path would kick the PRM until Koji ran a down script. Triggering will fix this issue, and it's the kind of thing that needs to happen quickly, so may not really be appropriate for the Guardian anyway.
Following Jamie's table in elog 8654, I have connected up the channels 0, 1 and 2 from ADC0 on the IOO computer to rfm send blocks, which send the signals over to the rfm model, and then I use dolphin send blocks to get over to the ass model on the lsc machine.
I'm using the 1st 3 channels on the Pentek Generic interface board, which is why I'm using channels 0,1,2.
I compiled all 3 models (ioo, rfm, ass), and restarted them. I also restarted the daqd on the fb, since I put in a temporary set of filter banks in the ass model, to use as sinks for the signal (since I haven't done anything else to the ASS model yet).
All 3 models were checked in to the svn.
I have implemented a proto-ASC in the ASS model.
In an ASC block within the ASS model, I take in the POP QPD yaw, pit, and sum signals. I ground the sum, since I don't have normalization yet (also, the QPD that we're using normalizes in the readout box already). The pit and yaw signals each go through a filter bank, and then leave the sub-block so I can send the signals over to the SUS model, to push on PRM ASCPIT and ASCYAW.
In doing this, I have removed the temporary PRM ASCYAW connection that Koji had made from the secret 11'th row of the LSC output matrix (see Koji's elog 8562 for details from when he implemented this stuff).
LSC, SUS and ASS were recompiled, and restarted. I also restarted the daqd on the fb.
I put the POPDC cable back to the DC output of the bias tee that is the first thing at the LSC rack that the POP110 PD sees. So, now we should be back to the old nominal PRCL locking, with the addition of the new QPD.
I'm going to give it a whirl.....
Something has happened that all of the C1:LSC-dof_NORM_SQRT_ENABLEs are disabled, but normally some are enabled and others are not.
In the hopes that miraculously this change happened after Jamie restarted the conlog this afternoon, I checked the conlog. These channels, however, were not recorded.
Using the instructions on the conlog wiki page, I added the _MON channels to the conlog list. The one snag I hit was that the medm screen referred to in the wiki isn't usable if you open it by hand using the medm gui, since it needs to know what IFO you're at to fill in the macro expansion variables. To remedy this, I changed the "FE STATUS" button on the sitemap to "CDS", and added the conlog screen to the list of options.
Now I see that the conlog at least knows about these channels, for future reference.
This is a mid-evening update, so I don't forget all the stuff I've already done.
Aligned PRMI, no nice flashes on POP110. Aligned and locked PRM-ITMY half-cavity on the carrier, and used that POP beam to center the beam on the POP110 PD. I also turned on the new QPD and centered the beam on it.
Notes about QPD setup: The "zero/cal" switch is OFF, so none of the small knobs on the front (basically, everything but the gain knob) should be bypassed. The gain knob is set to position 3. This is the highest gain that I can have without the "too much light" saturation light blinking on the front panel. (During this time, POP110I is flashing around 200 counts).
I made a super hacky ASC screen, which is accessible from the ASC button on the sitemap. While there is a pitch path in the model, I only put in the yaw elements (except for the QPD readouts) in the screen, since that's what I'll be using for now.
I added filter banks to the front side of the ASC subblock in the ASS model, so that I have a place to monitor the QPD signals on the screen and with striptool.
Using the settings that Koji recorded in elog 8521 in the "Locking with SQRT(POP110I)" section (and no ASC engaged so far), I can lock the PRMI for ~10 or 20 seconds, at 150 or 200 counts on POP110I. So, I'm doing well so far, and next up is to copy the ASC filters Koji made in elog 8562, and try the new ASC.
I didn't have any success with the ASC tonight. I copied over the filters that Koji had used in elog 8562, and put them in the new ASC filter banks (and turned them off in the SUS-PRM_ASCYAW bank). I also moved all the old scripts that were in .../scripts/ASC to an OLD subdirectory (the most recent edit is from 2009 sometime). I then copied over the up and down scripts that Koji had written for his ASC test into the ..../scripts/ASC directory, and modified them to work with my new channels.
I then tried locking, and wasn't very successful. Actually, my best lock, ~4 minutes, including tweaking up the PRM alignment, was when the ASC path was off (even though I thought it was on). After discovering my mistake, I tried locking for another hour or so, but haven't really gotten anywhere. The lock stretches I'm getting are rarely long enough for me to get to the terminal and run my up script, and the maybe ~6 or 7 times I've been able to run it, I haven't converged toward finding a good gain value for the PRC yaw loop. At some point, I redid the MICH alignment since it had drifted away a bit, but that didn't really help.
I think that one of the next things I might try is carrier-locking the PRMI, to find okay loop gain settings for the ASC path. Since the QPD output is already normalized (I'd have to custom-make some electronics to make it non-normalized), I think the gain should be the same for both carrier and sideband lock cases.
Once I finally get a good, stable, PRMI sideband lock, I think I need to take the following measurements:
* CTRL and ERR spectra for MICH and PRCL
* TFs for MICH and PRCL loops
* Sensing matrix, including AS55, REFL11, REFL33, REFL55, POX and POY.
---->> Are there any others?
This is nice - how about figuring out how to plot the measurement and model on the same plot? I guess we need to figure out how to go from counts to Watts.
I haven't done a units conversion for the measured vs. modelled plot, but at least we can compare the separation between the different degree of freedom signals. Figuring out why the REFL11 measurement and models are so different is still high on my to-do list. But at least the measurements that were taken last month are consistent with one another. EDIT: The separation angles match up pretty well between the 2 sets of measurements, but the overall rotation isn't really consistent. I do not believe that the phase rotation values that we're using online changed between the measurements, so the I&Q lines should be the same for both seets of measurements....however, I did not write down the phase rotation values at the time of the first measurement, so there's a chance that they were different. Also, something that I need to monitor is the coherence of my measurement, to make sure I'm really driving and measuring something.
2 measurements, with overall rotation arbitrarily rotated to make MICH lines match up:
Same 2 measurements, without the arbitrary overall rotation:
Measurement vs. Model, with the *modelled* phase arbitrarily rotated:
I am working on making the Proto-ASC less "proto". I have put IPC senders in the LSC model to send the cavity trigger signals over to the ASS model, for ASC use. I'm partially done working on the ASC end of things to implement triggering.
LSC should be compile-able right now, ASS is definitely not. But, I expect that no one should need to compile either before I get back in a few hours. If you do - call me and we'll figure out a plan.
I have finished my work on the LSC and ASS models for now. The triggering is all implemented, and should be ready to go. There are no screens yet.
I have *not* compiled either the LSC or the ASS, since Rana and Manasa still have the IFO.
With Rana's help/supervision/suggestions, I have closed the loop on the PRMI ASC servo with the new QPD. I think I've had it locked for ~30+ minutes now. It was locked for ~45 minutes, but then the MC momentarily lost lock. I immediately recovered the PRMI+ASC (after small PRM yaw tweaking, since the ASC isn't triggered yet, so the MC lockloss caused a big yaw step function to go to the PRM, which displayed a bit of hysteresis.).
My biggest problem was that I didn't really understand Koji's servo filter choices, so I wasn't using the right ones / doing good things. In particular, I need to compensate for the oplev servo filters. The oplev servo shape is something like ^, so the 1/(1+G) shape is something like =v= (ignoring the lower horizontal lines there). For tonight, we just turned off the PRM oplevs, but clearly this isn't a permanent solution. (Although, after Rana went in and roughly centered the PRM oplev, we noticed that turning the oplev on and off doesn't make a huge difference for the PRM....we should investigate why not. Also, we turned off the FM2 3.2Hz resonant gains in the PRM oplevs, since the Q of those filters is too high, much higher than our actual stacks).
Rana and I also locked the PRM-ITMY half cavity, and used that beam to realign the beam onto the POP QPD, POP110 PD, and the camera.
The POP QPD pitch and yaw signals with the half cavity have some noise, that looks like 60Hz crap. Since this goes away (rather, is much less noticeable) with the regular sideband-locked PRMI, we suspect this is a problem with perhaps the normalization, with the sum very low, and having some noise on it.
Once we had our ASC filters set up (not the 10Hz boost yet though, I think), if I increased the gain from -0.02 to -0.03, we start to get some gain peaking. With a gain of -0.04, the peak is very noticeable around 250Hz. We aren't sure where this is coming from, since it shouldn't be coming from the ASC loop. The UGF of that loop is much lower (I measured it, to check, and the UGF is ~5Hz). Anyhow, this is still a mystery, although the gain of -0.02 holds the cavity pretty well.
I measured the power spectra of the POP QPD pit, yaw, sum, as well as POPDC and POP110I, with the ASC loop on and off (dashed lines are with the loop on. You can see that the yaw motion as seen on the QPD was reduced by almost 2 orders of magnitude below 1Hz. It also looks like we can win some more by turning on the equivalent pitch ASC servo (this is also something we see when looking at the dataviewer traces).
I also tried to measure the PRMI sensing matrix, but I get some weird results, even after I double the drive actuation. I need to be checking whether or not my drive is actually coherent with the error signals that I'm seeing, because right now I'm not sure that I believe things. I'm going to leave that on the to-do list for tomorrow night though.
* Engage POP QPD -> pitch loop, copying yaw loop.
* enable ASC triggering
* model PRMI sensing matrix and error signals, bringing one arm into resonance
* Lock the PRMI, and bring the Xarm into IR resonance using the ALS system.
Here are some numbers and plots from the night:
Right now, I'm locking the LSC with:
MICH LSC with AS55Q, FMs 4 and 5 on, FM 3 is triggered, gain = -40.0, normalized by sqrt(POP110I)*0.1
PRCL LSC with REFL33I, FMs 4 and 5 on, FM 9 is triggered, gain = +2.5, normalized by sqrt(POP110I)*10
(FM3 of MICH and FM9 of PRCL are the same, just in different spots).
The ASC (only POP yaw -> PRM yaw right now) has:
FMs 1,2,5,6 on (1 = integrator [0:0.1], 2 = 3.2 res gain, 5 = [1000,1000:1 and gain of 0.01], 6 = 10Hz boost). Gain = -0.020, Limit=5000.
Turn off the input, turn on the output and the gain, clear the histories (to clear out the integrator in FM1), then turn on the input.
PRM oplev is OFF. (need to put in a filter to compensate for it in the ASC servo, but for tonight, we just turned it off.)
We measured the spectra of the POP QPD signals with the ASC loop on and off:
I also measured the ASC loop (with the PRM oplev still off):
(sorry about the separate plots - I can't make DTT give me more than 2 plots on a page at a time right now, so I'm giving up, and just making 3 separate pages)
Weird sensing matrix, unsure if I'm really getting good coherence:
Not sure why it was so poorly aligned, since the misalignment "event" happened while we were all away at lunch, but I steered the MC optics until their SUSYAW and SUSPIT values were about the same as they were before they got misaligned. MC autolocker took over, and things are back to normal.
The BLRMS are totally crazy today! I'm not sure what the story is, since it's been this way all day (so it's not an earthquake, because things eventually settle down after EQs). It doesn't seem like anything is up with the seismometer, since the regular raw seismic time series and spectrum don't look particularly different from normal. I'm not sure what's going on, but it's only in the mid-frequency BLRMS (30mHz to 1Hz).
Here are some 2 day plots:
All of us in the control room / desk area heard a sudden whoosh of air a few minutes ago. It kind of sounded like a pressure washer or something. We determined that the northmost nitrogen bottle outside the front door was letting out all its gas.
It's a gazillion degrees outside (okay, only 91F, according to a google of "Caltech Weather"), and those bottles are in direct sun all day.
We are leaving the bottle as-is, since it seems like its has finished, and nothing else is happening.
Last night before dinner, I copied over the ASC yaw servo filters to the ASC pitch filter bank. Using ASC gain of +0.001, I was getting the ~250Hz oscillations that Rana and I had seen with yaw.
Rana pointed out to me that my measured TF of the yaw loop doesn't look right up in the several hundred Hz region:
As you can see on the right side, which is all of the PRCL ASC yaw filter banks, multiplied by a simulated pendulum filter, the magnitude should just keep decreasing. However, on the measured plot on the left, you can see that I have a little gain hump. I'm not sure what this is from yet.
Rana had the epiphany that I didn't have any antiwhitening for my POP QPD. Ooops.
We looked at the schematic for the Pentek Generic board (pdf), and saw that it has a Zero @ 15Hz, and Poles @ 150Hz and 1500Hz, times 2 stages. We determined from the TF that I posted that probably both stages are engaged, so I made an antiwhitening filter consisting of the inverse (so, 2 poles at 15Hz, 2 zeros at 150Hz and 2 zeros at 1500Hz). [Rana points out that for this low frequency system we may not want to include the 1500Hz compensation, since it is probably just enhancing ADC noise]. The ASC system worked really well, really easily, after that.
Another note though, the AA stage of the Pentek Generic boards have 4 poles at 800Hz, which are not compensated.
Rana also added a 60Hz comb to the filter bank with the AntiWhitening, since the QPD has an unfortunately large amount of 60Hz noise. Also, the 60Hz lowpass in the ASC loop was engaged for both pitch and yaw.
Rana, Lisa and Manasa also found that the ASC system was *more* stable with the PRM oplev ON.
So, the ASC locking situation is:
PRM oplev loops on.
AS-POP_QPD_[PIT/YAW] filter banks with FM1, FM6 on.
ASC-PRCL_[PIT/YAW] filter banks with FM1, FM5, FM6 and FM9 on.
ASC-PRCL_YAW_GAIN = -0.040
ASC-PRCL_PIT_GAIN = +0.030
(No triggering yet).
The ASC Up and Down scripts (which are called from the buttons on the ASC screen) have all of these gain settings, although they assume for now that all the filters are already on.
Here's a screenshot of the power spectra showing the angular motion suppression. The PDF is attached so you can zoom in and see some details. The dashed lines are the "PRMI locked, ASC off" case, and the solid lines are the "PRMI locked, ASC on" case. You can see that according to the QPD, we do an excellent job suppressing both the pitch and yaw motion (although better for yaw), but there isn't a huge effect on POPDC or POP110I. While we could probably do better if we had a 2 QPD system with the QPDs at differet gouy phases, this seems to be good enough that we can keep the PRMI locked ~indefinitely.
I would like to compile the ASC model, so that I can implement triggering. For tonight, we did not have the ASC engaged during our PRMI+Xarm tests (see Manasa's elog), but I think it'll make things a little easier if we can get the ASC going automatically.
[Lisa, Rana, Jenne]
Lisa asked to see a model of the PRMI sensing matrix with REFL165 included, in the hopes that it wouldn't be as degenerate as REFL33.
The conclusion, immediately after looking at this, is that I should make sure the REFL beam is nicely aligned onto the REFL165 PD (Koji did some tests, swapping out the REFL165 resonant PD with a broadband PD, and I don't remember if he aligned beam back onto the REFL165 PD). Then, I need to measure the PRMI sensing matrix, including REFL165. Hopefully, it is similar to the model, and we can use it as our 3f diode for locking.
I have modeled the PRMI sensing matrix as I bring the Xarm into resonance. In optickle, I have the PRMI on sideband resonance, the ETMY is artificially set to have a transmission of 1, and the ETMX has it's nominal transmission of 15ppm. I start with the ETMX's microscopic position set to lambda/4 (antiresonant for IR in the arm), and take several steps until the ETMX's microscopic position is 0 (resonant for IR in the arm).
Modeled sensing matrix, units = W/m, Offset = 2.66e-07, phase in degrees
MICH Mag MICH Phase PRCL Mag PRCL Phase
AS55 3.348E+04 142.248 5.111E+03 70.571
POX11 3.968E+01 -66.492 1.215E+04 54.312
REFL11 3.231E+05 24.309 9.829E+07 144.311
REFL165 9.946E+03 -159.540 4.540E+05 -64.710
REFL33 1.963E+04 -168.530 1.573E+06 -2.744
REFL55 1.160E+06 -6.755 5.429E+07 86.895
Modeled sensing matrix, units = W/m, Offset = 0, phase in degrees
MICH Mag MICH Phase PRCL Mag PRCL Phase
AS55 1.647E+06 57.353 3.676E+06 -81.916
POX11 3.927E+02 -118.791 2.578E+04 -102.158
REFL11 7.035E+05 61.203 1.039E+08 167.149
REFL165 1.602E+04 -144.586 5.971E+05 -49.802
REFL33 2.157E+04 171.658 1.940E+06 -9.133
REFL55 1.822E+06 7.762 6.900E+07 101.906
For REFL55, the MICH magnitude increases by a factor of 1.6, while the PRCL magnitude increases by 1.3 . The MICH phase changes by 15 degrees, while the PRCL phase also changes by 15 degrees. Just eye-balling (rather than calculating), the other REFL PDs look to have similar-ish magnitude and phase changes. Certainly none of them are different by orders of magnitude.
Here is the Sensing Matrix movie (sorry for the iffy quality - my movies usually come out better than this):
This is the sensing matrix for the sideband locked on PRMI, bringing the Xarm into resonance from anti-resonance, in 20 equally-spaced steps. You can see the microscopic ETMX offset (units of meters) in the title of the figures.
I was surprised to see some of the 'jumps' in the sensing matrix that happen near the end, when the arm is almost in resonance. I'm in the process of making movies of the error signals as the Xarm is brought into resonance. I'll have to post those in the morning, since they're taking a long time to produce and save, however when I looked at a few, there is some weird stuff going on as we get close to resonance, even with the 3f signals.
The modeling phone call is in the morning, but if anyone who is not regularly on the call has thoughts, I'm all ears.
I am prepping to do the POP QPD calibration, and so have turned off the POP QPD, and put it onto a micrometer stage. My plan is to (after fixing the ASC servo filters to make the servo AC coupled, rather than DC coupled) lock the PRM-ITMY half cavity, and use that beam to calibrate the QPD. While this isn't as great as the full PRMI, the PRMI beam moves too much to be useful, unless the ASC servo is engaged.
While on the table, I noticed 2 things:
* In order to place the micrometer, I had to temporarily move the POP55 RFPD (which has not been used in quite a long time). I think it's just that the panel-mount SMA connector isn't tight to the panel inside, but the RF out SMA cable connector is very loose. I have moved the POP55 RFPD to the very very south end of the SP table, until someone has time to have a quick look. (I don't want to get too distracted from my current mission, since we haven't put beam onto that PD for at least a year).
* The ITMX oplev beam setup isn't so great. The last steering mirror before the beam is launched into the vacuum is close to clipping (in yaw... pitch is totally fine), and the steering mirror outside of vacuum to put the beam on the QPD is totally clipping. The beam is falling off the bottom of this last steering mirror. Assuming the beam height is okay on all of the input optics and the in-vac table, we need to lower the last steering mirror before the oplev QPD. My current hypothesis is that by switching which in-vac steering mirror we are using (see Gautam's elog 8758) the new setup has the beam pointing downward a bit. If the problem is one of the in-vac mirrors, we can't do anything about it until the vent, so for now we can just lower the out of vac mirror. We should put it back to normal height and fix the oplev setup when we're at atmosphere.
I was bad, and forgot to elog the most important part of my work yesterday - that I had rotated the POP QPD by 90 degrees, so that I could fit the micrometer onto the table. There is a sticker on the front of the QPD to indicate which direction is "X" and "Y" for the output of the readout box. Right now (and the way that I will mount the QPD to the table, after I redo the calibration today), X is PITCH, and Y is YAW. Koji and Nic swapped the cables to the ADC to make this all consistent.
Yesterday, I locked the PRM-ITMY half cavity, and tried to take calibration data. However, with no ASC servo engaged, the beam was still moving. Also, with only the half-cavity, I had very little light on the QPD, and since it has internal normalization, the outputs can get a little funny if there isn't enough light. I had checked, and even with the gain cranked up to maximum, the "light level too low" LED was illuminated. So, my calibration data from yesterday isn't really useful.
Today, hopefully after lunch, I will lock the PRMI with the new AC-coupled ASC servo, so that I can have the servo on, and the PRMI locked on the sideband, so that I have more light on the QPD.
After that, it seems that the final thing we need to do before we vent is hold an arm near, but off resonance, lock the PRMI, and then swing the arm in and out of resonance a bit.
Calibration data for the POP QPD has been taken, with the PRMI locked on sideband (with AS55Q and REFL33I, since it stayed locked longer with those 2). ASC was on, AC coupled.
We didn't get too far on either side of center of the QPD, since the ASC servo would go unstable, so we only explored the roughly linear region. Data / plots / analysis to follow.
[Annalisa, Jenne, Nic]
After having troubles with the Xarm earlier (maybe Manasa can write/say something about this? Something about perhaps seeing the phase tracker jump, and cause it to lose lock?), we moved on to the Y arm.
Annalisa locked the Yarm green, and closed the ALS loop. I believe that earlier today, she tuned the gain such that we don't start getting gain peaking at a few hundred Hz. We would like to get a script going, so that it's not so labor intensive to reclose the ALS loop after an MC lockloss....but that's a daytime task.
We then found the IR resonance, using only the Yarm ALS system. After Manasa's work yesterday, the Yarm was very stable while locked with the ALS. We took a power spectrum of POY11_I_ERR, which I have calibrated using the number in elog 6834 of 1.4e12 cts/m, or 7.14e-13 m/ct. See the figure below.
After that, we changed the offsetter2 offset such that the arm was off resonance, but not so far off that we crossed any significant resonances (in particular, we wanted to not go as far as the 55MHz resonance).
Then, I tried to lock the PRMI for a while, but the alignment wasn't very good. We knew that the Yarm was well aligned, since our IR resonance was > 0.98, but it had been a while since we had aligned the X arm. I tweaked the ITMX position to make the Michelson dark, and then tried acquiring PRMI lock. At first, I tried with REFL165 I and Q, but with the non-ideal alignment and the offset in the 165 diode (LSC offsets was not run this evening), I wasn't catching any locks. I then switched to AS55Q and REFL33I, but wasn't able to catch lock there either.
The MC lost lock, which made us lose the ALS loop, but the ALS had been locked for more than 30 minutes, at least. I tried locking the PRMI with the current alignment (after having misaligned ETMY), but was only able to get lock stretches of 1 second at maximum.
We are calling it a great success for the night, since we have confirmed that, at least for the Yarm, Manasa's beatbox work has improved things. Also, we have a pretty solid plan for trying the PRMI+arm tomorrow, even though it didn't work out tonight.
These are the data, one plot for when the vertical QPD position was changed, and one for when the horizontal (yaw) QPD position was changed.
The micrometer is in inches, so 1 unit is 0.1 inches, I believe.
Clearly, I need to redo the measurement and take more data in the linear region.
I tried to retake POP QPD calibration data again today. The MC was mostly fine, but whenever the PRMI unlocked, both ITM watchdogs would trip. I'm not sure what was causing this, but the ITM alignment wasn't perfect after this kind of event, so I felt like I was continuously locking and realigning the arms to get the alignment back. Then, after turning on the ASC and tweaking up the PRM alignment for maximum POP110I signal, I had to recenter the QPD, so none of my previously taken data was useful. Frustrating. Also, I had recentered the PRMI-relevant oplevs, but I had these weird locklosses even with nicely centered oplevs.
I have given up for the daytime, and will come back to it if there's a spot in the evening when arm measurements aren't going on.
Here is the data from last week, and the data from today. The micrometer readings have been calibrated into mm, and I have fit a line to the linear-looking region. Obviously, for the Pitch calibration, I definitely need to take more data.
Those 'peaks' for the oscillations seem ridiculously broad. I think you should look again, really quickly, with smaller bandwidth at, say, the 2kHz oscillation, to make sure it looks reasonable.
I took POP QPD calibration data with a new method, on Rana's suggestion. I locked the PRMI, and engaged the ASC servo, and then used awggui (x8) to put dither lines on all of the PRMI-relevant optic's ASCPIT and ASCYAW excitation points. I then took the transfer function of the suspensions' oplev signals (which are already calibrated into microradians) to the POP_QPD signals (which are in counts). This way, we know what shaking of any optic does to the axis translation as seen by the POP QPD. We can also infer (from BS or PRM motion for PR3, and ITMX motion for PR2) what the folding mirrors do to the axis translation. Note that we'll have to do a bit of matrix math to go from, say, PRM tilt effect to PR3 tilt effect on the axis motion.
The data is saved in /users/jenne/PRCL/July152013_POP_TFs.xml . There is also a .txt file with the same name, in the same folder, listing the frequencies used by the awg.
I'll analyze and meditate tomorrow, when my brain is not so sleepy.
The proto-ASC now includes triggering. I have updated the hacky temp ASC screen to show the DoF triggering. I have to go, but when I get back, I'll also expose the filter module triggering. So, for now we may still need the up/down scripts, but at least the ASC will turn itself off if there is a lockloss.
Last night, I took sensing matrix data at various different offsets for the Yarm. The sensing matrices I measured were of the PRMI, while the Yarm was (a) Held off resonance, (b) Held at ~50% peak power, and (c) Held on resonance.
The dither lines were clear in the MICH and PRCL spectrum, so I think I'm driving hard enough, but something else seems funny, since clearly the REFL165 I and Q signals were not completely overlapping last night. If they were, we wouldn't have been able to lock the PRMI using REFL 165 I&Q.
Anyhow, here's the data that was taken. Data folder is ...../scipts/LSC/SensingMatrix/SensMatData/
Yarm off resonance, SensMat_PRMI_1000cts_580Hz_2013-07-18_012848.dat
Yarm at ~50% resonance, SensMat_PRMI_1000cts_580Hz_2013-07-18_013937.dat
Yarm on resonance, SensMat_PRMI_1000cts_580Hz_2013-07-18_013619.dat
The results of today's MC spot position measurements:
spot positions in mm (MC1,2,3 pit MC1,2,3 yaw):
[2.3244717046516197, -0.094366247149508087, 1.6060842142158149, -0.74616561350974353, -0.67461746482832874, -1.3301448018100492]
MC1 and MC3 both have spots that are a little high in pitch, but everything else looks okay.
I have just centered IPPOS, as well as PSL POS and PSL ANG (also called IOO POS and IOO ANG on the screens). Annalisa is working on placing mirrors to get the IPANG beam to its QPD, so that one will be centered later.
I have some data for how much motion of any PRMI-relevant optic affects the beam seen by the POP QPD.
For this, I am using the QPD calibration from the micrometer (elog 8851) to get me from counts to mm of motion. Note that the pitch calibration hasn't been redone (I tried locking the PRMI this afternoon, but ITMX kept drifting away from me**, so I didn't get any more data.) The pitch calibration is obviously very rough, since I only have 2 points defining my fit line.
Anyhow, if we assume that's close enough to get us started, I now have a calibrated QPD spectrum:
As detailed in elog 8854, I took single frequency transfer functions, to determine the effect at the QPD from shaking any single PRMI optic. These transfer functions gave me a conversion factor between the optics' oplev readings (in microradians) to the counts seen at the QPD. I used this number, as well as the QPD calibration from the micrometer data, to convert each optics' oplev spectra to motion that one would expect to see at the QPD.
I have not yet completely figured out how to make an estimate of the PR folding optics' affect on the POP QPD spot position, if I know their motion. The current plan is to do as Den did in elog 8451, and infer the PR2/3 motion from the ITMX/BS motion measured by the oplevs. My plan was to take the spectra of the oplev signals while the BS/ITMX are undamped, divide by the SOS pendulum transfer functions, then multiply by the TT transfer functions (which I finally wrote down in elog 8564). I'm planning on using the undamped data, since the oplev signals are still within the linear range of the oplev QPDs, and I won't have to take the SUS damping into account. Anyhow, after I do that, I'll have an idea of how much the tip tilts are moving, but not what that does to the cavity axis.
However, after looking at the plots below, it seems like the PRM is the main culprit causing the PRC axis motion, although the BS (and to a smaller extent the ITMs) are not innocent. Since the plots get very busy very quickly, I have many plots, each plot comparing one of the above QPD spectra (either pitch or yaw) with a single optics' oplev inferred motion.
EDIT: After talking with Koji, I realize that, since the ASC was engaged during the PRM oplev spectrum measurement, I cannot yet say whether the motion is due to PRM, or if it is from PR2 or PR3, and imprinted on the PRM via the ASC servo. The lump where the PRM-caused motion is greater than the QPD spectra is entirely in the region where the ASC is active. So, the QPD motion I expect without the ASC would be something like the green trace in the PRM comparison plots. The blue trace is then the closed loop measurement. Since the ITMs and BS are below the closed loop values, they aren't the ones causing the big lump. I should retake all of these spectra at a time when the PRMI is locked, but the ASC is not engaged. I'm not sure if I'll have a chance to do that tonight or not. If I can find some GPS times when the PRMI was locked, before we had ASC, I can get the oplev data.
I think part of the reason PRM is dominating is that it's damped motion is ~10x greater than any other optics', most noticeably the BS'. I'll write a quick separate elog about this. Also, note that the ~3Hz resonant gain had been turned off in the PRM oplev loop, but not in any other loops. This is why there isn't the sharp dip in the PRM's oplev motion. Also, since the PRM ASC was engaged for this measurement, and the ASC pushes on the PRM to minimize the QPD motion, it isn't totally crazy that the PRM's motion is greater than what we actually see at the QPD, if it is compensating for the motion of other optics.
** Re: PRMI locking this afternoon, it was almost as if ITMX were bi-stable. I aligned both arms, to set the ITM positions. Then, I would lock and tweak up the michelson to get the AS port nice and dark (usually touching ITMX today, since it seemed like the drifter....ITMX at this point was usually between -7 and -15 microradians in pitch from the center of the oplev QPD). When I then brought the PRM back into alignment, ITMX was starting to drift away. As soon as I hit the LSC Enable switch, and looked back over to the OpLev screen, ITMX was misaligned, usually around -65 urad in pitch. I did this circus probably 3 or so times before giving up. Koji said that he had seen this bi-stability before, but he didn't remember what fixed it. The drifting that Koji mentioned in elog 8801 seems to have been fixed by centering all the PRMI oplevs every day, but I had already done that, and was still seeing ITMX drift.
After Koji and I lowered the power into the PMC and saw that the MC locked nicely, I remeasured the spot positions (no alignment on the PSL table, or of the MC mirrors has been done. Also, WFS are off, since there isn't any power going to them).
spot positions in mm (MC1,2,3 pit MC1,2,3 yaw):
[1.1999406656184595, 0.63492727550953243, 1.0769104750021909, -1.0260011922577466, -1.059439987970527, -1.2717741991488549]
The spot positions seem to have actually gotten a bit better in pitch (although between 2 consecutive measurements there was ~0.5mm discrepancy), and no real change in yaw. This means that Rana was right all along (surprise!), and that decreasing the power before the PMC reduces alignment pain significantly.
After everyone's work today (good teamwork everybody!!), we are a GO for the vent.
Steve, please check the jam nuts, and begin the vent when you get in. Thanks.
We will open the BS and ITMY doors first thing tomorrow morning. I plan to try to be in around 9 am. The first order of business will be to flip the folding mirrors that are not currently flipped (SR2, SR3, PR3).
SR2 is flipped, and reinstalled. We did that before lunch, and we're about to go in and work on SR3 and PR3.
EDITS / Notes:
I set dog clamps to have a reference position of where the tip tilt was, then I removed SR3 from the chamber. Once out, I followed the same procedure I used for PR2 during the last vent - I removed the whole suspension (top mount, wires, optic) from the cage, and laid it down flat. Then I loosened the set screw which pushes on the teflon nudge, removed the mirror, inspected it, and put it back in, with the HR side facing the back side of the ring. Then I replaced the suspension system in the cage, and put the mirror back into the chamber.
When I loosened the teflon nudge at the top of the mirror holder ring, the optic seemed to fall down a tiny bit. I think this implies that the HR surface of the optic did not used to be parallel to the front face of the mirror holder ring. When I put the suspension back onto the cage, the pitch balancing was very bad. We checked the level of the table that I had the cage on, and it was miraculously pretty level, so I did the pitch balancing out of the chamber.
Also, during my quick inspection of the mirror (not thorough, just using room lights), I noticed a small fleck of lint near the edge of the optic on the HR surface. The HR surface is now on the outside of the SRC, but we should still blow at the optic with the ionized nitrogen to get it off.
I did not think to check the fine-tuning alignment of SR2....Koji did that after lunch (which I will elog about in a separate elog).
Yesterday afternoon, I went back into the BS chamber, and flipped both PR3 and SR3. Now all of the recycling cavity folding mirrors have been flipped.
For PR3, I followed the same procedure as SR2, setting a reference position, removing the optic, flipping it, etc. When I put it back in, I realized that since this has a 41 degree angle of incidence, the beam going to the BS had translated north by ~1cm. After some fiddling, Koji pointed out that the 2 degree wedge probably had a more significant effect than just the HR surface having moved back a small amount. Anyhow, we adjusted PR3 such that we were going through the BS aperture, as well as the ITMY aperture.
During the flip of PR3, Annalisa and I noticed that the arrow on the barrel of the LaserOptik mirrors also indicates the thickest part of the wedge. This is opposite of our SOS optics, where the arrow's position on the barrel indicates the thinnest part of the wedge. For both PR3 and SR3, I kept the arrow on the same side of the optic as it was originally.
I then flipped SR3, following again the same procedure. PR3 I had done a tiny bit of pitch rebalancing, although I think it was unneccessary, since it is within what we can do with the poking/hysterisis method. SR3 I did not do any pitch rebalancing. With PR3 aligned at least to the ITM, Koji and I aligned SR3 and SR2 so that the AS beam was hitting the center of all the SRC optics. We also adjusted the steering mirrors after the SRM to get the beam centered on PZT3, the last optic on the BS table, which launches the beam over to the OMC chamber. We scanned around a bit by turning the PZT's knobs, but we were unable to see the AS beam on the camera.
[Jenne, Manasa, Koji]
Earlier today, we locked and aligned both the X and Y arms.
I then went into the BS chamber, put on the BS' aperture, and put an aperture along the AS path. (We had Michelson fringes, so I centered the aperture around the fringes. I used one of the brass ruler things that we use to center the beam on ITMs and ETMs, on a riser. I put this aperture at the edge of the BS table, after the AS beam is launched toward the OMC chamber. The idea was to replace PR3 such that I could get the beam back through the BS aperture, and the brass ruler aperture, in hopes that we would see arm flashes, and not have to open the ITMY and ETMY heavy doors.)
I set references on the table so that I could put PR3 back in its original position, then removed PR3 from the chamber.
Steve set up a HeNe for me, that we pointed through the optic. The ghost beam was very high, indicating (as expected) that the wedge was not perfectly horizontal.
I took the suspension off of the cage and laid it down, as I have in the past.
I removed the optic from the suspension, to try to figure out which was the fat vs. skinny side. I noticed that there are very faint marks on the actual fat and skinny sides of the optic. (Mpral - for the LaserOptik mirrors, look for the faint lines that are the full width of the barrel, not the placement of the arrow which marks the HR side). I put the optic back in (HR side toward the back, fat side on the left (as you look at the face of the optic), which is consistent with the picture in the Optical Layout page of the Wiki, near the bottom.) the optic holder ring.
I put the suspension back on the cage, and saw that the HeNe's ghost beam was now nearly horizontal relative to the straight-through beam. Excellent. Also, the pitch balancing didn't seem to change noticably, which I determined was within "poking" distance of where we need it to be.
I put PR3 back onto the BS table, and adjusted it around until I got the beam through both the BS aperture, and the one on the AS path. As usual, this took quite a while, but as soon as I got through both of those apertures (really at the same place, not close to being through them, but as close as I could tell by eye - this is what took forever), Koji and Manasa saw flashes in the Yarm! Yay!
Since I had to move PR3 in angle a tiny bit, I reset the references, then dogged down PR3. We still had flashes, this time in both arms, so we closed up the light doors.
We have now locked and aligned both arms in IR after the adjustment of PR3, and see both arms' green at 01 or 02. We are about to start checking the green positioning on the periscopes. We will also need to check the AS path, as well as IPPOS and IPANG before we close up. We see REFL on the camera.
Separately - Manasa remembered that 2 clean things were dropped yesterday - a screw, and an allen key. Since they're both Clean, we're not too worried, although she thinks a long-armed person may be able to reach the allen key.
[Manasa, Koji, Jenne]
We went into the BS and IOO chambers, and aligned the green beams such that they came out of the vacuum chamber. The idea here was to get the beams at the same height, but slightly offset in yaw. This required moving the Periscope on BS table, PBS in front of that periscope, the Periscope on the IOO table, and 2 steering mirrors on the IOO table after the 2nd periscope. The tables were not releveled, although we have aligned the full interferometer to this situation, so we do not want to touch the tables. The MC spot positions are still consistent with those measured earlier this afternoon, before this work, so I'm not concerned.
We confirmed that both green beams are hitting a good place (centered in pitch, and just left and right of center in yaw) on the mirror in the OMC chamber, and are getting to the center of the first mirror on the PSL table. We then coarsely aligned the beams on the PSL table.
We then relocked and aligned the arms for IR, and checked that the AS beam is centered on the mirrors in the BS chamber, and that the beam is coming out, and to the AS table. I touched the last mirror before PZT3 a small amount in yaw, and then PZT3 in pitch and yaw, until we saw the beam recentered on the first mirror on the AS table. At that point, we were also back to the center of the AS camera (which is good, since Koji had aligned all of that the other day). So, the AS beam is good.
We checked IPPOS, and have centered the beam on all the mirrors, and aligned the beam onto the QPD.
We checked IPANG, by looking through the viewports at the mirrors in the ETMY chamber. We are now centered in yaw, but clipping a bit low. This is what we want, since we always end up drifting high during the pump-down.
We see a nice, unclipped REFL beam on the camera.
We see a beam a little high on the POP camera, but Koji looked on the table with a card, and saw the beam....we just need to do minor alignment on the out of vac mirrors.
We checked again that the green TEM00 beams from both arms come to the PSL table.
We are getting POX and POY out, since we are using them to lock and align the arms.
Manasa and Koji recovered one clean allen key from the bottom of the chambers, but one remains, as a sacrifice to the vacuum gods.
I believe that, with the exception of checking the oplevs and taking photos of PR3, and the green steering optics, we have finished all of our vent tasks. We should do a quickie alignment on Monday, check the oplevs, take some photos, and put on the heavy doors. Pumping can start either Monday afternoon or Tuesday morning.
[Koji, Manasa, Jenne]
The Y arm was locked in IR, and we saw flashing in the Xarm (Gautam had the Xarm for green work when we began). I checked IPANG, and the beam was beautifully unclipped, almost perfectly centered on the first out of vacuum mirror. I aligned the beam onto the QPD.
We then swapped out the MC Y1 that we use at low power, and replace the usual 10% BS, so that we wouldn't crispy-fry MC REFL. Manasa adjusted the half wave plate after the laser, to maximize the power going toward the PMC. We relocked the PMC, and see transmission of ~0.84, which is at the high side of what we usually get. The beam was aligned onto MC REFL and centered on the WFS, and the MC was locked at nominal power. Koji tweaked up the alignment of the MC, and ran the WFS offset script. I aligned beam onto POP QPD and POP110 coarsely (using a flashing PRC, not a locked PRM-ITMY cavity, so the alignment should be rechecked). The arms have both been locked and aligned in IR....the green beams need to be steered to match the current cavity axis.
The AS beam, as well as REFL and POP, are all coming out of the vacuum nicely unclipped.
Notes: When Koji was aligning the SRM to get the SRC cavity roughly aligned (the AS flashes all overlapping), we noticed that there is some major pitch-yaw coupling. Serious enough that we should be concerned that perhaps some connector is loose, or an actuator isn't working properly. This should be checked.
Moral of the story: Coarse alignment of all mirrors is complete after pump-down and we have IR locked and aligned to both arms at nominal power.
Still to do:
* Restore PRM, align beam onto the REFL PDs.
* Lock PRM-ITMY cavity, align beam onto POP PDs.
* Align AS beam onto AS55.
* Recenter all oplevs.
* Recenter IPPOS and IPPANG at nominal power.
* Start locking!!
I have furthered Koji's work, and moved the filter on/off state for all the filter banks also to the burt snapshot.
Turning on the ASS is now much faster than it was originally, with the ezcawrites in series.
We have looked a little more at the SRM situation. We aligned the SRM, and then aligned the oplev, so that we had a convenient monitor of the optic's motion.
When we use the _COMM channels, which are the usual ones on the IFO_ALIGN screen, the pitch slider makes pitch motion, but the yaw slider makes the oplev spot move ~45degrees from horizontal.
However, when we use the bias channels that are in the front end model, parallel to the ASC path, pitch moves pitch, and yaw moves pure yaw.
So, we conclude that the SRM coils are fine, and there is something funny going on with the slow part of the actuation.
Koji restarted the slow computer susaux, and burt restored it, but that did not fix the situation. We went inside and looked at all of the ribbon cable connections, and pushed them all in, but that also has not fixed things.
We have been looking at D010001-b, the coil driver board, and we think that's where the summing resistor network between the slow bias slider, and the coil outputs from the fast model exists. (It's not 100% clear, but we're confident that that's what is going on).
Tomorrow, we will pull the SRM's coil driver board, and see if any of the components in the slow slider path, before the summing point, look burned / broken / bad.