The new ITMX was aligned by changing the DC biases.
The resultant DC biases are reasonably small.
C1:SUS-ITMX_PIT_COMM = -0.2909
C1:SUS-ITMX_YAW_COMM = -0.0617
The alignment was done by trying to resonate the green light in the X arm cavity.
The spot position of the green light on the ITMX mirror looked good. This was confirmed by inserting a sensor card.
I did the OSEM mid-range adjustment and the rotation adjustment but at the end the OSEM DC voltage has changed due to the DC bias operation.
The OSEM rotation was approximately optimized so that all the face shadow sensors are sensitive to the POS motion but the SIDE shadow sensor is insensitive to the POS motion.
It needs a free swinging diagnosis.
It stacked again . We should take a closer look at it.
The ITMY mirror was released. The OSEM readouts became healthy.
The reflected RF power going back to the RF generation box will be :
Power at 11MHz = 2 dBm
Power at 29.5 MHz = 3 dBm
Power at 55 MHz = 9dBm
Assuming the input power at 11 and 55 MHz are at 27 dBm (40m wiki page). And 15 dBm for 29.5 MHz.
Since there is an RF combiner in between the generation box and the resonant box, it reduces the reflections by an additional factor of 10 dB (#4517)
In the estimation above, the reduction due to the RF combiner was taken into account.
Besides the reflection issue, the circuit meets a rough requirement of 200 mrad at 11 and 55 MHz.
For the 29.5 MHz modulation, the depth will be reduced approximately by a factor of 2, which I don't think it's a significant issue.
So the modulation depths should be okay.
Assuming the performance of the resonant circuit remains the same (#2586), the modulation depths will be :
Mod. depth at 11 MHz = 280 mrad
Mod. depth at 29.5 MHz = 4 mrad (This is about half of the current modulation depth)
Mod. depth at 55 MHz = 250 mrad
What are the reflected RF powers for those frequencies?
Is the 29.5MHz more problem than the 55MHz, considering the required modulation depth?
Tue Sep 6 17:48:02 PDT 2011
Here are the results of the arm loss measurements, which I have done before the vent.
I ran the existing matlab script, called 'armLoss.m', to estimate the loss. The script resides in /scripts/LSC.
Round trip loss = 154.668624 +/- 11.343204 ppm
The figure above is a time series of the measurement.
In the lower plot the power in the ASDC_PD are plotted. The green dotted-curve is the power when the Y arm is unlocked.
The blue dotted-curve is the one when the Y arm is locked.
In the upper plot the estimated loss from each combination of locked/unlocked power are plotted.
Round trip loss = ????? 50 ppm ?????
The obtained time series looked wired because difference in the ASDC power when the arm was locked/unlocked were small.
This small difference results in such a small loss.
To see what was going on I will look at the trend data.
I did the measurement of the arm loss on both X and Y arm by running the armLoss script.
The results will be posted later.
The measurement itself wasn't good.
I looked at the full 2 kHz data which was taken during the time when I was running the arm loss script on the X arm.
The plot below shows the raw data. The X arm was locked and unlocked sequentially several times.
The ASDC power didn't show a significant difference between the state where it is locked and unlocked.
I am not sure why, but It could be because of a misalginment or some kind of mode-mismatching, which can decrease the coupling efficiency of light going into the cavity.
The raw data were analyzed.
I split the ASDC data into two data, (1) low power state, when the cavity is locked (2) high power state, when the cavity is unlocked.
Then each state was averaged to estimate the averaged ASDC power in each case.
The number I obtained are :
ASDC when X arm was locked = 54.77755 cnts
ASDC when X arm was unlocked = 55.45830 cnts
Those numbers correspond to a round trip loss of 78.780778 ppm, which sounds too small for me.
To see what was going on I will look at the trend data.
I stopped puming at 9:30 PM and the pressure in P1 is at 450 mtorr.
I followed exactly he procedure that Steve noted on his elog entry.
Here is a plot of the histroy of our pumping today.
1, close V3
2, close RV1 with torque wheel
3, turn off PR1 & 3
4, disconnect metal hose between RV1 and PR3
I will start the Maglev tomorrow morning.
[Suresh / Kiwamu]
The attenuator was removed and now the MC is happily locked with the full power of 1.2 W.
(what we did)
+ replaced the perfect reflector, which was before the MCREFL_PD, by a 10% beam splitter like it used to be.
+ removed the attenuator (combination of HWP and PBS).
+ realigned the beam path on the AP table, including the MCREFL path and WFS path.
+ made the aperture of the MC2F camera narrower in order to avoid a saturation.
+ aligned the MC suspensions so that it resonates with the TEM00 mode.
+ put a ND filter on the AS camera
C1:IOO-MC_RFPD_DCMON = 0.98 (locked)
C1:IOO-MC_TRANS_SUM = 17500 (locekd)
(next things to do)
+ measurement of the spot positions on each MC mirror.
+ centering of the beam spot by steering the input mirrors on the PSL table
Last night I noticed that PZT1 didn't work properly
I am not sure what is going on. Today I will try localizing the cause of the problem.
As far as I remember it was perfectly working at the time just after we readjusted the OSEMs on MC1 and MC3 (Aug 23th)
The symptoms are :
+ No response to both pitch and yaw control from EPICS (i.e. C1:LSC-PZT1_X and C1:LSC-PZT1_Y)
+ When a big value (-3 or so) from EPICS was applied, the PZT1 mirror suddenly jumped.
However it turned out it just corresponded to a state where OOR (Out Of Range) LED lights up.
I did some brief checks :
+ checked the voltage going into the HV amplifiers' "MOD" input. Those are the voltage coming out from DACs and controlled from EPICS.
--> looked healthy. They went from -10 to 10 V as expected (although the HV amp takes up to only +/-5V).
+ swapped the ''MOD" input cables such that C1:LSC-PZT1 controls the PZT2 HV and vice versa.
--> The PZT2 mirror was still controlable, but the PZT1 mirror still didn't move. So the DAC and EPICS are innocent.
+ swapped the D-dub cables, which are directly going into the feedthroughs, such that the PZT1 HV drives the PZT2 mirrors and vice versa.
--> the PZT2 mirror became unable to be controlled. For the PZT1 mirror, only PITCH worked smoothly.
Something happened about 8 years ago.
Old iLog entry by AJW (2003/Sep/8)
Old iLog entry by AJW (2003/Sep/9)
The OSEM pictures taken in Sep/6 have been uploaded to Picasa.
The spot positions on the MC mirrors were measured in the vacuum condition.
The obtained spot positions are quite bad and roughly at 2-3 mm level. We have to realign the beam axis and the MC mirrors.
Aug 23 2011 (in air)
The spot positions on the MC mirrors were readjusted.
All the amount of the off-center became smaller than 2 mm, which meet requirements of the beam clearance on the Faraday.
In order to improve the MC1-YAW and MC3-YAW spot positions, the angle of the incident beam has to be shifted by approximately 1/100 rad.
However it turned out to be very difficult to introduce such amount of angle only with the steering mirrors on the PSL table since we have to keep the same translation while changing the angle.
The interferometer was coarsely aligned.
Now spatially overwrapped DRMI and FP arm fringes are visible on the AS camera although the incident beam alignment was done only with PZT2.
All the DC biases were saved so that we can go back to this condition any time.
/***** some health checks *******/
[FINE] IPPOS : it looks okay but the spot on the QPD is a little bit too low by a few mm.
[NOT GOOD] IPANG : maybe hitting a post or something because the spot is vertically split into two. The spot is too low.
[FINE] POX/POY/POP : they all are coming out. POP is visible with an IR viewer.
[FINE] REFL : no clipping but the beam looks a little bit too low relative to the CCD camera.
[FINE] AS : no clipping and the spot position on the AS camera looks fine.
[FINE] Green beams : both X and Y beams are successfully landing onto the PST table without no clipping.
[FINE] Suspensions : all of them are reasonably quiet without the oplevs, which is good.
All the optcs were excited
Sat Sep 10 02:14:11 PDT 2011
A comment :
Since the LSC RFPD have a long cable of more than 6 m, which rotates a 33 MHz signal by more than 360 deg, so the delay has always existed in everywhere.
The circuit you measured is a part of the delay existing in the LSC system, but of course it's not a problem as you said.
In principle a delay changes only the demodulation phase. That's how we treat them.
RA: Actually, the issue is not the delay, but instead the dispersion. Is there a problem if we have too much dispersion from the RF filter?
[Mirko / Kiwamu]
The resonant box has been installed together with a 3 dB attenuator.
The demodulation phase of the MC lock was readjusted and the MC is now happily locked.
We needed more modulation depth on each modulation frequency and so for the reason we installed the resonant box to amplify the signal levels.
Since the resonant box isn't impedance matched well, the box creates some amount of the RF reflections (#5339).
In order to reduce somewhat of the RF reflection we decided to put a 3 dB attenuator in between the generation box and the resonant box.
+ attached the resonant box directly to the EOM input with a short SMA connector.
+ put stacked black plates underneath the resonant box to support the wight of the box and to relief the strain on the cable between the EOM and the box.
+ put a 3 dB attenuator just after the RF power combiner to reduce RF reflections.
+ readjusted the demodulation phase of the MC lock.
(Adjustment of MC demodulation phase)
The demodulation phase was readjusted by adding more cable length in the local oscillator line.
After some iterations an additional cable length of about 30 cm was inserted to maximize the Q-phase signal.
So for the MC lock we are using the Q signal, which is the same as it had been before.
Before the installation of the resonant box, the amplitude of the MC PDH signal was measured in the demodulation board's monitor pins.
The amplitude was about 500 mV in peak-peak (see the attached pictures of the I-Q projection in an oscilloscope). Then after the installation the amplitude decreased to 400 mV in peak-peak.
Therefore the amplitude of the PDH signal decreased by 20 %, which is not as bad as I expected since the previous measurement indicated 40 % reduction (#2586).
(Preparation of Y arm locking)
(A) The f2a filters were newly designed and applied to ETMY (see the attachment)
(B) Once the Y arm is aligned such that the TEM00 mode flashes, the transmitted light is visible on the ETMYT CCD camera.
(C) With the newly installed resonant EOM circuit the PDH signal from AS55 looks healthy.
(A) To design the f2a filters there is a handy python script called "F2A_LOCKIN.py" in /scripts/SUS.
The script measures the coil imbalance at high frequency and low frequency using a LOCKIN module and then gives us the information about the imbalance.
The script hasn't yet been completed, so it doesn't return the intuitive answers but returns something non-intuitive. I will modify it.
(B) To see the transmitted light from the Y arm I was going to align the CCD camera on the Y end table.
However I found that once the green light is blocked, the transmitted light can be visible on the camera without any re-alignment.
Therefore I haven't rearranged anything on the Y end table, but I just blocked the green light.
Perhaps we still need to align the photo diodes for the transmitted light.
(C) While Suresh was working on MC, I looked at the signal from AS55 with all the optics misaligned except for ITMY, ETMY and BS.
The signal from the Y arm looked very PDH signal, and the demodulation phase seemed to be about 45 deg to maximize the I signal.
I tried locking it by feeding the signal back to ETMY but failed due to a too much POS to angle coupling in the ETMY actuators.
I was momentarily able to capture a higher order mode with a negative gain in LSC-YARM_GAIN, but it was quite difficult to keep it locked.
This was because once I increased the gain to make it stable, the angle instability became more significant and lost the lock immediately.
This was the reason why I had to do the f2a filter redesign. Tomorrow we can try locking the Y arm.
The Y arm has been locked with AS55.
A next thing is to check the spot positions on the ETMY and ITMY mirrors so that we can evaluate the recent beam pointing.
- - - parameter settings - - -
C1:LSC-YARM_GAIN = -0.03
AS55 demod phase = 0.2
WF gains = 21 dB
C1:LSC-TRY_OUT = 0.57 (maximized by steering PZT2)
The spot positions on ITMY and ETMY were measured using the LOCKIN modules in C1ASS when the Y arm stayed locked.
The beam was successfully aligned such that it hits the center of the ETMY mirror.
However on the other hand the angle of the beam is pitching and it's going upward as the beam propagates to ETMY.
/***** RESULTS ******/
Here is a summary of the measurement :
Also a cartoon is shown below.
The scale is not quite true, but at least it gives you a 3D information of how the beam is pointing down to the Y arm.
/***** MEASUREMENT *****/
In order to measure the spot positions the standard technique, namely A2L, was used.
Since the C1ASS model was made for doing the A2L measurements on each arm cavity, the LOCKIN modules in C1ASS were used.
First the Y arm was locked with AS55 (#5398), and then the C1ASS was activated by calling some scripts from C1ASS_QPDs.adl.
In order to calibrate the signals from LOCKINs, an intentional coil imbalance was introduce.
This is the same calibration technique as Valera explained before (#4355) for measurement of the MC spot positions.
Forgot to attach a picture of the ITMY's face camera when it was locked.
The horizontal position of the spot looks good, but the vertical position is apparently too low, which agrees with the A2L result.
Although we did some of the Input Matrix diagonalization, we have not yet actually used this knowledge. As a result all of the optics are shaking all over the place.
The f2a filters were newly designed and installed on BS and PRM.
So the lock of PRMI will be more stable .
Once the SRM oplev project settles down, I will adjust the f2a filters on SRM too.
New f2a filters were installed on SRM.
The lock of DRMI should be more stable than last night.
The bad medm screens have been fixed. There are no blank fields and all the links are correct.
I've found that a few of the screens still have Whited-Out fields due to naming changes (OL SUM and ALS-> TM OFFSET). I attach a screen shot of it.
The OL screens have the wrong SUM names and the IFO ALIGN screen is pointing to the wrong SUS screens.
With the new input matrix, it looks like YAW and SIDE are not quite decoupled on ETMX.
It needs one more kick and free swinging test.
- - - details
To see what exactly is going on, I changed the input matrix from the default to the new one, which Jenne computed (#5421) on ETMX.
I started putting the elements of the input matrix from POS through SIDE, one by one.
It seemed that POS and PIT worked fine. However the YAW signal looks containing a lot of the SIDE signal.
Similar to YAW, SIDE also interact with the YAW motion and somehow rings up both YAW and SIDE signals as Jenne reported ( #5438).
So right now the YAW and SIDE rows are partially reburted to the default elements in order to avoid ringing up.
but ETMX and BS were not good at all. ETMX was ringing up when I turned on the damping.
Excited all the optics. They will be automatically back after 5 hours.
Sat Sep 17 02:02:07 PDT 2011
The f2a filters were installed on ITMs and ETMX.
Now all of the suspensions has the f2a filters.
[Anamaria / Kiwamu]
The incident beam pointing was improved by using PZT1 and PZT2.
With some triggers the lock of PRMI became smoother.
For the DRMI lock, the MICH and SRCL signals on AS55 are not quite decoupled, so we should find cleaner signals for them.
+ locked the Y arm
+ aligned incident beam by using PZT1(#5450) and PZT2. The spot positions on ITMY and ETMY are now well-centered.
+ tried activating C1ASS but failed. It needs some gain changes due to the new PZT1 response.
+ locked the X arm
+ aligned the TRX PD (Thorlab signal PD) and set the trigger.
+ C1ASS also doesn't work for the X arm
+ realigned the PRM and BS oplevs. the PRM oplev was clipped at a steering mirror on the optical bench
+ locked PRMI and aligned the PRM mirror such that the optical gain was maximized
+ optimized the demod phase of AS55 and REFL11
+ checked the UGF of the MICH and PRCL lock. The UGF of MICH is about 100Hz with gain of -20, and the UGF of PRCL was 85 Hz with gain of 0.1
+ adjusted the output matrix such that the MICH control doesn't couple into the PRCL control.
+ set the triggers for the MICH and PRCL control to make the lock acquisition smoother.
+ tried locking DRMI and it was sort of locked. However the SRCL signal showed up a lot in AS55_Q, where the MICH signal is extracted.
Actually the clipping of POP wasn't in the chamber but it was on the first lens on the optical bench.
So I repositioned the lens to avoid the clipping and now there are no clipping on POP.
We found that POP beam is clipped by the steering mirrors inside the tank.
GOAL1: Stable lock of DRMI
GOAL2: Measurement of the LSC input matrix in the DRMI configuration
/- - Daytime works - - /
+ Measurement of the arm lengths (Jenne / Kiwamu / volunteers)
+ Optimization of the oplev control loops (Paul)
+ Inversion and installation of the SUS input matrices (Jenne)
+ Tuning of the SUS damping gains (Steve)
+ Measurement of the modulation depths (Mirko)
+ Preparation of the green broadband PD (Katrin)
+ Fixing the Y arm green lock servo (Katrin / Kiwamu)
+ Installation of RFPDs (Anamaria)
+ Minimization of the AM sidebands (Anamaria / Keiko)
+ Preparation of a script for measuring the LSC input matrix (Keiko)
+ MC WFS (Suresh)
+ Online adaptive filtering (Mirko / Jenne)
+ Modification of C1ASS (Kiwamu)
+ Fixing IPPOS (volunteers)
+ Auto alignment of PRCL and SRCL (volunteers)
+ Loss measurement of the arm cavities (volunteers)
+ Fixing the ETMX SIDE slow monitor (volunteers)
/- - Nighttime works - - /
+ Locking of DRMI
+ Characterization of DRMI and complete the wiki page
IPPOS is back. A cable had been disconnected at the 1Y2 rack. So I put it back to place.
The cartoon below shows the current wiring diagram. I think this configuration is exactly the same as it it used to be.
The gain of whitening filters on AS55 was decreased from 21 dB to 0 dB for the Y arm locking.
- - (Background)- -
Since the modulation depths became bigger from the past (#5462), the PDH signal from Y arm was saturated in the path of AS55.
Due to the saturation the lock of the Y arm became quite difficult so I decreased the gain of of the whitening filter from 21 dB to 0 dB.
In this condition, a required gain in C1:LSC-YARM_GAIN is about -0.3, which is 10 times bigger from the default number.
For the MICH locking tonight, it may need to be back to a big gain.
Since the MC wasn't able to capture the 00 mode in this morning I aligned the incident beam going to MC.
As a result C1:IOO-RFPD_DCMON went down to 0.6. However the beam on IPPOS is almost falling off from the QPD.
The MC REFL camera is now available. The camera name is "MCR" and you can call it from the videoswitch script.
+ repositioned and aligned the MCR camera.
+ checked the MCR camera.
=> found the camera view shows a negative image (i.e. the beam spot is dark and the background is bright !!)
+ replaced the camera by a spare one.
+ modified the videoswitch script because the input channel 3 was wrongly assigned to MCR.
MCR was correctly assigned to the input channel 18.
[Jenne / Kiwamu]
Fb was sick. Dataviewer and Fourier Tools didn't work for a while.
After 10 minutes later they became healthy again. No idea what exactly was going on.
One thing we found was that : during the sickness of fb, it looks like daqd was restarting by hisself. Is this normal ??
Here is the bottom sentences of restart.log. Apparently daqd was rebooting although we didn't command to do so.
daqd_start Tue Sep 20 02:41:17 PDT 2011
daqd_start Tue Sep 20 13:18:12 PDT 2011
daqd_start Tue Sep 20 17:33:00 PDT 2011
Did you take the 180 deg shift into your account ?
Since your measurement was done when the loop was closed, there must be an additional 180 deg phase shift (in other words, minus sign).
In the end I just fitted the response magnitude. I was initially fitting the complex response function, but ran into problems which I think were cased by overall phase offsets between the data and test function. Can I canvass for opinion if fitting the magnitude is OK, or should I try again fitting the phase too?
Found some LSC scripts didn't run on pianosa. Particularly all the scripts on the C1:IFO_CONFIGURE screen don't run.
They need to be fixed.
The output matrix in the C1ASS servo were coarsely readjusted and the servos seemed working.
However it is difficult to say the servo is very good or so-so,
because the ETMY suspension moves a lot and hence the cavity eigen axis moves a lot too.
It turned out the oplev controls on ETMY were just bad.
It looks like the whitening filters have been OFF and because of that the resultant open-loop was not crossing the unity gain.
I will check the whitening filters.
(open-loop transfer function)
The blue dots are the measured data points and the green curve is the fit.
Apparently the open-loop doesn't go above the unity gain, so the oplev had been doing nothing.
If we try to increase the overall gain it will oscillate because of the phase delay of more than 180 deg around 3 Hz.
The red curve is the expected one with the whitening filters (WFs) properly engaged.
Note that WF are supposed to have two zeros at 1 Hz and two poles at 10 Hz.
The whitening filters for the ETMY oplevs are back.
The whitening board had been in the rack but the ADC was connected directly to the oplev interface board without going through the whitening board.
In fact the interface board and the whitening board had been already connected. So the ADC was making a shortcut.
I disconnected the ADC from the interface board and plugged it to the output of the whitening board.
Here is an example of the new open-loop transfer function with the whitening filters.
before the measurement I increased the control gain by an arbitrary number to obtain gain of more than 1 around 1 Hz.
As a suspension test I am leaving all of the suspensions restored and damped with OSEMS but without oplevs
[Koji / Kiwamu]
The c1scx and c1x01 realtime processes became frozen. We restarted them around 1:30 by sshing and running the kill/start scripts.
Good work for the oplev noise simulations. Here are some comments/questions:
(A) The noise looks suppressed but the open-loop transfer function doesn't look so good, because it doesn't have sufficient phase margins at the UGFs (0.01 and 10 Hz).
I guess it is better to have a phase margin detector in your code so that the code automatically rejects a bad phase margin case.
Actually since the number of data points are finite, the rms detector in the simulation can not always find a sharp loop oscillation.
(B) The resultant poles and zeros seem canceling each other but the filter still has a structure. Is something wrong ?
Pole 1 frequency = 0.0497181 Hz
Pole 2 frequency = 2.01809 Hz
Zero 1 frequency = 0.0497181 Hz
Zero 2 frequency = 2.01809 Hz
The servo for aligning the Y arm is working fine with the coarse gain coefficients.
However then I found the ASS_Xarm servo was not healthy.
So the next step is to refine the X arm servo in C1ASS.
+ With the ETMY oplev the Y arm became quieter after we recovered the oplev whitening filter (#5523)
+ The Y arm alignment scripts can be run from the usual C1IFO_CONFIGURE screen.
It will servo the spot positions on ITMY and ETMY, and align the input beam pointing. It brings the Y arm power to about 1.
+ The X arm servo is doing something funny. It doesn't bring the arm power up to 1.
I thought the X arm didn't need any modifications because the X arm servo doesn't include PZT1 and PZT2.
So it maybe a simple bug (for example, some switches are disable and so on)
According to the spectra, all of the suspensions had been damped with the OSEMs. The peaks around 1Hz are reasonably suppressed.
However the spectra from ITMX showed a noise floor at very high level. This is because of strange jumps in the signal of the UL shadow sensor.
I will check some analog circuits for the UL sensor.
(ITMX shadow sensors)
Here is the spectra of the ITMX shadow sensors taken during the damping test (#5534)- -
The UL sensor shows a unacceptable amount of noise.
Additionally I checked the time series of the ITMX shadow sensors and found ONLY the UL sensor frequently showed strange jumps in data.
Here is an example of the time series showing a jump ONLY in the UL sensor.
It is possible that the jumps are coming from some circuits, since the rest of the sensors (including the oplevs) don't detect the same jump.
Currently the damping of the ITMX suspension is intentionally disabled for the noise investigation.
The issue on the ITMX UL sensor has been fixed. It was because of a loose connection in the sensor signal path.
After the fix, the sensor responses completely changed and the suspension became unable to be damped with the new matrix.
At the moment the ITMX suspension is damped by the default input matrix.
we should do the free swinging test once again.
The loose connection was found on the rear side of the 1X5 rack.
There is an adapter card on the rear side, where the driver and sensor signals are combined into a single cable.
I pushed the sensor cable (bottom right in the picture) and the noise disappeared.
Note that I changed the labels on the adapter cards from the old X/Y convention to the new one.
After fixing the loose cable the ITMX suspension became unable to be damped.
So I put the input matrix back to the default and it immediately started damping happily. It means our new matrix is not valid any more.
Here is the latest noise spectra of the ITMX sensors damped with the default input matrix.
As usual all of them are limited by the ADC noise above 20 Hz. (ADC noise is plotted in purple curve)
During the work I also pushed not only ITMX ones but also the cable for the rest of the optics in the adapter cards.
Then PRM became unable to be damped, so it implies the PRM suspension also used to be the same situation.
The input matrix of PRM has been also back to the default.
The lock of PRMI wasn't so robust although it could stay locked for more than 10 minutes.
There have been 2-3Hz spikes in everywhere. It needs to be investigated.
+ Diagnosis on the suspensions.
+ Check the beam centering on the RFPDs.
+ Check the f2a filters on PRM and BS.
+ Health check of the suspensions by locking some cavities and measuring the noise spectra for comparison.
+ Trying to use another signal port other than AS55.
The attached picture below is an example of the REFLDC and POXDC signals in time series.
This was when PRCL and MICH were locked by REFL33_I and AS55_Q respectively.
Note that when PRMI is unlocked, REFLDC goes to ~ 5000 counts and POXDC goes within ADC noise of ~ 1 counts.
According to the POP camera it looked like something was oscillating in the YAW direction which coincided with the spikes.
I tried finding any suspicious angular motions in the ITMs, BS and PRM olevs, but none of them showed the 2-3 Hz feature.