I have resurrected the MC WFS on Friday night.
I have uncommented the WFS part of the MC autolocker.
The WFS total gain was empirically set to 0.1 such that the loops have no instability.
The loops somewhat worked through the weekend although they seemed to have the drift of the operating points
in accordance with the WFS spot.
According to c1scy.mdl, OL signals should be connected to adc_0_24 to adc_0_27 but they were connected to adc_0_16 to adc_0_19 which are assigned to QPD signals.
Actually cable connections were messed up. One ribbon cable was connected from QPD driver and ADC ports assigned for OL, and another ribbon cable was connected from the board combining the signals of oplev and QPD to ADC port assigned for QPD.
Now ETMY oplev is working well and aligned to center.
I found that the ADC channels for IP_ANG had been assigned to a wrong machine.
IP_ANG is supposed to be acquired at c1auxey (east end), but actually it had been at c1auxex (south end).
This is the reason why we couldn't see any signals from IP_ANG.
So I fixed it by editing the db files (i.e. ETMXaux.db and ETMYaux.db). Now it seems working fine.
This mistake obviously came from the X-Y name swapping business. Something else might be still wrong.
It turns out there are no reasonable signal from the segment 1 on the IP_ANG QPD.
For right now I can still use it as a funny QPD, but I absolutely need somebody to check and fix it in a daytime.
Rana and I found that the QPD for the optical lever at X end are showing small signals.
At this moment each of the segments exhibits approximately 200 counts when the oplev beam is centered.
These small numbers may be due to the coating of ETMX, but we are not sure.
Probably we have to increase the gain of the QPD depending on situations.
So a set of the tomorrow's daytime task is:
1. check the trend data of the QPD outputs to see how much signals were there in the past.
2. check the whitening filters to make sure if it's on or off.
3. If it's necessary, increase the gain of the QPD to have reasonable readouts.
I am going to ask somebody to do this task.
I tried aligning the IR beam axis for the X arm to have good beam centering on ITMX and ETMX.
As a first attempt, I started translating the beam upward by steering PZT1 and PZT2, since the pitch was quite off from the center on ITMX.
As a result I could decrease the pitch off-centering down to about 0.5 mm on ITMY, but on the other hand TRX decreased a lot (by a factor of 4).
I am worrying if something in the central part of IFO might be clipping the beam.
When I was touching PZT1 and PZT2, I payed attention on IP_ANG so that I don't lose a beam spot on IP_ANG.
As long as the beam is on the IP_ANG QPD, the angle of the beam should not be so much different.
Each time after I touched the PZTs, I realigned ITMX and ETMX to maximize the transmitted light.
In this way I proceeded the alignment by changing the PZT offsets little by little while keeping the X arm locked always.
At the beginning, all the PZT offsets were zero. And at the end of this work they became:
C1:LSC-PZT1_Y = 1.880
C1:LSC-PZT2_Y = -1.699
But during this alignment work TRX gradually decreased eventually down to 0.25, which had been 1 at the beginning (TRX is calibrated by dividing it by its maximum power).
Along with this TRX reduction, I found that the optical gain also decreased by a factor of about 5.
This fact has been confirmed by intentionally increasing the filter gain such that the servo oscillates at the UGF.
The amounts of the X arm's beam off-centering have been measured by the A2L technique.
PIT = -1.61 mm
YAW = -0.918 mm
PIT = -3.76 mm
YAW = -2.24 mm
[Valery, kiwamu, Jenne, Suresh]
I first interchanged the two QPD's on the Y end table to see if the problem QPD related. Exchanging the units did not make any difference. The problem therefore had to be in the cables or the circuit boards in 1X4
We traced the signals pertaining to the IP_ANG QPD ( "Initial Pointing Beam") using Jay's wiring diagram (pages 2 and 5 of 7). We noted that while the signals were available on all Segments till the Monitors (Lemo) on 1X4-2-2A card, two of the lines did not reach the output of the cross connect 1X4-B8. We checked card to make sure that the signals were indeed reaching the back plane of the 1X4-2 chassis using a D990612 extension board. The card was found to be okay. We therefore suspected that the cable (CAB_1X4_?) going from the card to the cross connect 1X4-B8 was faulty. Indeed visual inspection showed that the crimping of the connector was poor and weight of the cable had put further strain on the crimping.
I changed the 64-pin connector on the 1X3-2-2A side of the cable.
When I connected everything back together the problems persisted. Namely the lines P1-1A (Segment 1 high) and P1-2C (Segment 2 Low) were floating They were not reaching points 2T and 3T respectively on the output of the cross connect.
I therefore replaced 1X4-B8 with a similar unit which I found in one of the shelves along the East (Y) arm.
I then checked with the StripTool to make sure that all the quadrants are showing similar response to a flashlight on the QPD. All Segments are working fine now. Currently the IR Initial Pointing beam reaches the QPD but is not centered on it.
I did not attempt to center it since the beam appeared to be clipped and may anyway require repositioning.
JD: We need to meditate on where this beam could be getting clipped. Suresh and I checked that it's not on the viewport on the beam's way out of the ETMY chamber by seeing that the beam is far away from the edges of the viewport, and also far away from the edges of the black beamtube between the viewport and the table. Suresh mentioned that the clipping nature of the IP_ANG beam sometimes goes away. I don't know if this is the same clipping that Kiwamu might be seeing with the main beam, or if this is separate clipping just with the IP beam, after it's been picked off. I suspect it's the same as what Kiwamu is seeing....maybe when we move PZT1, we clip on one of the MMT mirrors or PZT2?? If this is true, it's a total pain since we might have to vent if we can't steer around it.
[Jenne and Kiwamu]
This time we aligned the vertical angle (not the translation) of the IR beam so that the transmitted light from BS shoots the center of ETMY.
The idea is to use ETMY as a beam pointing reference instead using IP_ANG, assuming the translation is not so bad.
As a result it looks like we are wining. A quick A2L test on ITMX_PITCH showed a small off-centering at sub-milimeter level.
We are concluding that the initial beam after PZT2 had been pointing downward somehow.
Before doing this whole job, we checked the spot shape on IP_POS to see if the beam is clipped or not. It was a round shape, which means no clipping around MMT.
But on the other hand, the spot on IP_ANG had been clipped more than half of its bottom as Suresh reported on his elog (see here).
I found that this clipping is able to be fixed by moving the beam angle upward. I guess the clipping happened at one of the steering mirror in the ETMY chamber.
According to these information, we imagined that the beam was somehow pointing downward after PZT2.
So we started aligning the beam by touching only PZT2 for vertical direction. Then we found a beam spot on ETMY's suspension frame, and brought it to the center.
Then we aligned BS and X arm for this new beam axis. The it resulted a small off-centering on pitch.
Once the MC fully gets back, we will examine the TRX degradation with this configuration.
I made several scripts to handle the mcass configuration and sensing measurements:
- The scripts and data are in the scripts/ASS directory
- The mcassUp script restores the settings for the digital lockins: oscillator gains, phases, and filters. The MC mirrors are modulated in pitch at 10, 11, 12 Hz and in yaw at 10.5, 11.5, and 12.5 Hz. The attached plot shows the comb of modulation frequencies in the MCL spectrum.
- The mcassOn and mcassOff scripts turn on and off the dither lines by ramping up and down the SUS-MC1_ASCPIT etc gains
- The senseMCdecenter script measures the response of the MCL demodulated signals to the decentering of the beam on the optics by imbalancing the coil gains by 10% which corresponds to the shift of the optic rotation point relative to the beam by 2.65 mm (75mm diameter optic) and allows calibration of the demodulated signals in mm of decentering. The order of the steps was MC1,2,3 pitch and MC1,2,3 yaw. The output of the script can be redirected to the file and analyzed in matlab. The attached plot shows the results. The plot was made using the sensemcass.m script in the same directory.
- The senseMCmirror script measures the response of the MCL demodulated signals to the mirror offsets (SUS-MC1_ASCPIT etc filter banks). The result is shown below (the sensemcass.m script makes this plot as well). There is some coupling between pitch and yaw drives so the MC coils can use some balancing - currently all gains are unity.
- The senseMCdofs scripts measures the response to the DOF excitation but I have not got to it yet.
- The next step is to invert the sensing matrix and try to center the beams on the mirrors by feeding back to optics. Note that the MC1/MC3 pitch differential and yaw common dofs are expected to have much smaller response than the other two dofs due to geometry of this tree mirror cavity. We should try to build this into the inversion.
The alignment of the interferometer goes basically step by step.
Tuesday will be an alignment day.
0. MC beam centering (it's done)
1. F2P to balance the coils on every optics including BS, PRM, SRM, ITMs and ETMs (Kiwamu).
2. A2L and then change the DC bias of ITMY and ETMY to get a perfect eigen axis (VF/Jamie).
3. align input PZT mirrors (PZT1 and 2) to maximize the Y arm transmission (VF/Jamie).
4. do the same things for X arm but using BS instead of the PZTs.
5. Alignment of the central part.
6. Make a script to automatically get those things done.
[Jamie / Valera / Kiwamu]
The incident beam pointing was improved a lot by using C1ASS realtime code.
Some more details will be posted later. The below is the list of the highlights today.
- The Y arm cavity was aligned to have good beam centering on the mirrors.
- The input PZTs were also aligned to the aligned Y arm by hand.
- Automation of the Y arm alignment using C1ASS_LOCKIN got partially functional with two loops closed. C1ASS correctly servos the centering on ETMY
- The amount of the off-centering on ITMY and ETMY look roughly within 1 mm.
- As a result the intracavity power got bigger by a factor of about 3.5
I closed all 8 dither loops for the Y arm initial alignment: 2x2 centering servo (this worked before) and 2x2 input beam servo for both pitch and yaw.
So far it looks pretty good - the error points go to zero and the arm power goes up to 1.
The offloading to the alignment biases and the PZTs is not yet automated.
Today the PMC, MC, and Y arm were very cooperative and a pleasure to work with.
The attached plots show the location of the ~29.5 MHz pole and the 59 MHz notch for each quadrant of the WFS1 Sensor head.
As may be seen from the above table, these frequencies will need to be adjusted in some cases.
From the plots we can see that, when there is no attenuation set on the attenuator AT65-0263 (ref D990249-A), the MAX4107 oscillations are seen in Q2,Q3,Q4 quadrants at around 200 MHz.
Rana suggested, from his previous encounter with this circuit, that the solution is to remove the second MAX4106 and the attenuator on the RF line to avoid this oscillation.
A look at the circuit board shows that some of the inductors have not been mounted. That explains the presence of only one notch though the schematic shows two.
Last night I aligned the incident beam axis and the Yarm by touching the PZT mirrors and the suspensions.
I didn't estimate how good they were aligned, but I guess the Y arm is now ready for the Y green light.
Next : Y green alignment and the MC spots measurement / alignment.
++ Motivation ++
Prior to the coming vent we want to have the Y arm, incident beam axis and Y green light aligned so that we can align some necessary optics in the chamber.
Also alignment of the incident beam will allow us to re-position the incident beam alignment monitor (i.e. IPPOS and IPANG).
Our plan was to first align the Y arm using the ASS system and then align the Y green light to the Y arm.
++ what I failed ++
First I was trying to measure the spot positions on the MC mirrors to make me sure the beam axis has/hasn't changed.
Also I was going to align the MC suspensions to have nice spot position on each suspension using the MCASS system
because this will help us checking the beam clearance in the Faraday and perhaps re-positioning of the Faraday during the coming vent.
But essentially I failed and eventually gave up because MCASS didn't work. It seems that MCASS needs some modifications in the scripts.
Then, to make me feel better I moved on to the Y arm and beam axis alignment.
++ what I did ++
I tried using C1ASS to align the incident beam and suspensions on the Y arm, but it didn't work.
However the drive signals from ASS and its demodulated signals looked fine. Only the feedback did not work correctly.
Every time I enabled the feedback paths, the arm just lost the lock. Something is wrong in the feedback paths.
Then I started to align the cavity by my hands while looking at the demodulated signal from each LOCKIN module.
I aligned the things until each demodulated signal fluctuates around zero.
At the end the beam spots on the ETMY and ITMY camera looked well-aligned and the transmitted light became larger by a factor of 2ish.
The servos of C1ASS for the Y arm and the beam axis alignments were fixed.
Now we can correctly run the Y arm ASS from the C1IFO_CONFIGURE window as usual.
The sign of some control gains had been flipped for some reasons, so I changed them to the correct signs.
Next : Health-check for the X arm ASS, the loss measurements.
Since we will measure (and hopefully adjust) the spot positions on the MC suspensions prior to the vent, MCASS is necessary for it.
Here is the MCASS status so far:
+ Valera worked on MCASS on the last February, and basically no progress after he left.
+ The MCASS model had been completed in C1IOO.mdl.
+ He made some useful scripts, including mcassup, mcassOn/Off, senseMCdecenter, senseMCmirrro and senseMCdofs.
Summary of those scripts can be found in his entry #4355.
+ We haven't closed the MCASS loops.
+ The control filters are still blank.
+ We haven't put any elements on the input and output matrices.
+ Some parameters for the dithering oscillators and demodulation systems were properly set.
So we can get the demodulated signals by simply running mcassUp and mcassOn. (This essentially corresponds to the A2L measurement.)
+ The PIT motions are driven at 10, 11 and 12 Hz for MC1, 2 and 3 respectively. For YAW, the frequencies were chosen to be 11.5, 12.5 and 13.5 Hz.
+ Some medm windows were prepared but not as refined as that of ASS.
+ Valera performed a measurement of the spot positions by using MCASS. The results are summarized in #4660.
+ We made an estimation about the beam clearance on the Faraday based on the measured spot positions (#4674)
So, it seems we should be able to at least measure the spot positions soon by using his scripts.
The X arm ASS was also fixed. So both X and Y arm ASS are now back to normal.
Now we can align the arms any time from the buttons on the C1IFO_CONFIGURE window.
The reason why the servo didn't work was that the sign of some control gains had been flipped.
This was exactly the same situation as that in the Y arm ASS (#5067).
SUS-ETMY_QPD is not responding. It is reading zero in dataviewer and 4,400 counts on QPD MEDM screen.......must be wrong cable connected
IP-POS is sick. Last time alive 7-19-2011
IP-ANG beam is clipping on pick-up mirror at ETMY chamber. This will have to be fixed at the vent. The qpd itself is responding to light.
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.
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.
+ Modification of C1ASS (Kiwamu)
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)
The channels for IPPOS had been assigned in a wrong way.
Because of this, C1:ASC-IP_POS_X_Calc corresponds to the actual vertical motion and C1:ASC-IP_POS_Y_Calc is for the horizontal motion.
We should fix the database file to get the correct vertical/horizontal corrdinate.
Now the C1ASS servos are working fine.
However at the end of the scripts sometimes it changes the DC force (e.g. C1:SUS-ITMX_PIT_COMM and so on) by a wrong amount.
So for this bug, it misaligns the suspensions a lot. I will take a look at the script tomorrow.
The input matrix of IPPOS were fixed so that the horizaontal motion correctly shows up in X and the vertial is Y.
(what I did)
+ The data base file, QPD.db, were edited.
QPD.db is a part of the c1isxaux slow machine and it determines the input matrix for deriving the X/Y signals from each quadrant element.
+ The previous input matrix was :
X = (SEG1 + SEG4) - (SEG2 + SEG3)
Y = (SEG1 + SEG2) - (SEG3 + SEG4)
+ The new matrix which I set is :
X = (SEG1 + SEG2) - (SEG3 + SEG4)
Y = (SEG1 + SEG4) - (SEG2 + SEG3)
The new matrix is a just swap of the previous X and Y.
+ Then c1isxaux was rebooted by :
+ The I did the burt restore it to this morning.
Did somebody delete all the scripts in /opt/rtcds/caltech/c1/scripts/ASS ?
I have moved all the MC_ASS scripts to a directory called MC under ASS
In any case, the daily backup of the scripts are found in /cvs/cds/caltech/scripts_archive.
I have moved all the MC_ASS scripts to a directory called MC under ASS
Initial pointing or IP-ANG is a pointing monitor of the MC. This beam is launched after the second pzt steering mirror.
IP-ANG is missing the pick up mirror by a few inches at ETMYchamber
1000 days plot show last appearance in Feb 2010
Looks good. Any way that you can tell in an unambiguous way, where the beam is, is very good. Ideally we want to have1-2 mm accuracy.
I wanted to center beams on the XARM cavity mirrors using c1ass model. I've run XARM setup script and then turned dithering on. Cavity went out of lock because calculated offsets were incorrect.
I was using TRX only and calculated rotation phases for ITM and ETM pitch and yaw. For this I've added a low pass filter into Q-quadrature bank and made DC value at the output to be zero by adjusting the phase. I've put gains (+1 or -1) in the I quadrature such that output was positive.
Then I've set the sensing matrix to identity as I decided to deal with separate loops. Of coarse, they are mixed by the cavity, but at least in the control system they are distinguished. Old matrix summed error signals in one degree of freedom from both mirrors. This makes more sense but still not precise because coils are not ideally diagonalized.
Then I've adjusted gains for control loop for every degree of freedom. I've ended up with (0.1; 0.1; 0.1; -0.1). I did not use large gains as I wanted slow convergence because of the demodulation low-pass filter time response constant of 20 sec. Coupling (I quadrature) was reduced from (0.9, 0.3, 2.4, 1.2) to zeros (0-0.1) in ~5 minutes, TRX increased from 0.73 to 0.90.
There is one thing that I do not understand yet. I think controllers should minimize angle -> length coupling that is proportional to I-quadrature if phase is correct. But phase depends on alignment and when the feedback loops are on, phase drifts. I could see it during my measurement. But I did not find any script that smoothly tunes phase such that coupling is all in I-quadrature. I guess this is not hard to set a gradient descent algorithm that minimizes DC value of Q-quadrature. Or how this is usually done?
Gouy not Guoy:
pronounced Goo-eee, with the emphasis on the second syllable.
It's OK; even Siegman got it wrong---48 times.
RA: NO, stil not OK.
I modified our existing c1ass model to include alignment of input steering TT1 and TT2 for YARM and BS for XARM. Corresponding medm screens are also created.
ETM_PIT: frequency = 6 Hz, amplitude = 100 cnts
ETM_YAW: 8 Hz, 400 cnts
ITM_PIT: 11 Hz, 800 cnts
ITM_YAW: 14 Hz, 1200 cnts
These values were chosen by looking at cavity transmission and length signals - excitation peaks should be high enough but do not shake the optics too much.
LO for each degree of freedom is mixed with cavity length and transmission signals that are first bandpassed at LO frequency. After mixing low-pass filter is applied. Phase rotation is chosen to minimize Q component
8 * 8 matrix was measured by providing excitation at 0.03 Hz to optics and measuring the response in the demodulated signals. Excitation amplitude was different for each optics to create cavity transmission fluctuations of 25%
Though coherence was > 0.95 during the measurement for each element (except for TT -> Length signals), after inverting and putting it to control servo, loops started to fight each other. So I decided to try a simple diagonal matrix:
TT1_PIT -> ETM_PIT_TRANS, TT1_YAW -> ETM_YAW_TRANS, TT2_PIT -> ITM_PIT_TRANS, TT2_YAW -> ITM_YAW_TRANS,
ITM_PIT -> ETM_PIT_LENGTH, ITM_YAW -> ETM_YAW_LENGTH, ETM_PIT -> ITM_PIT_LENGTH, ETM_YAW -> ITM_YAW_LENGTH
And this matrix worked much better.
8 loops are running at the same time. UGF for input steering loops is 20 mHz, for cavity axis loops - 80 mHz. Slower loop is stronger at low frequencies so that cavity axis servo follows input steering alignment.
When I started experiment the cavity was misaligned, transmission was ~0.4. Servo was able to align the cavity in ~30 seconds. This time depends on mirrors misalignment as well as input optics and cavity axis misalignment relative to each other.
When servo converged I disturbed ETMY, ITMY, TT1 and TT2. Servo was able to compensate for this.
Excitation lines seen by transmission and length of the cavity are suppressed as shown on the attached as pdf figures.
Though the servo is able to align the cavity during my tests, this does not mean it will work perfectly any time. So please, if you lock, try to use the servo for alignment. If something goes wrong we'll fix it. This is better then to align IFO by hands every time.
I've put 4 scripts into ASS directory for YARM alignment. They should be called from !Scripts YARM button on c1ass main medm screen.
Scripts configure the servo to align the cavity and then save computed offsets. If everything goes right, no tuning of the servo is needed.
Call TRANS MON script to monitor YARM transmission, then "ON" script for aligning the cavity, then "SAVE OFFSETS" and "OFF" for turning the servo off.
SAVE OFFSET script writes DC offsets to C1:OPTIC_ANGLE_OFFSET channel, not to _COMM channel!
LIMITS are set to 500 for cavity axis degrees of freedom and to 0.5 for input steering. Usually servo outputs is ~30% if these numbers. But if something goes wrong, check this for saturation.
DC offsets of all 8 degrees of freedom are written one by one but the whole offset of put at the same time. This works fine so far, but we might change it to ezcastep in future.
After Den's work with the ASS model this week, all of the channel names were changed (this wasn't pointed out in his elog....grrr), so none of the A2L scripts worked.
They are now back, however there is still some problem with the plotting that I'm not sure I understand yet. So, the measurement works, but I don't think we're saving the results and we certainly aren't plotting them yet.
I wanted to check where the spots are on the mirrors, to make sure Den's stuff is doing what we think it's doing. All of the numbers were within ~1.5mm of center, although Rossa keeps crashing (twice this afternoon?!?), so I can't copy and paste the numbers into the elog.
A near-term goal is to copy over Den's work on the Yarm to the Xarm, so that both arms will auto-align. Also, I need to put the set of alignment scripts in a wrapper, and have that wrapper call-able from the IFO Configure screen.
Also, while thinking about the IFO Configure screen, the "save" scripts weren't working (on Rossa) today, even though I just made them work a week or so ago. Rossa, at least, was unhappy running csh, so I changed the "save" script over to bash.
Ah, AWESOME. Indefinite PRMI lock was finally achieved.
- Looked at the POP setup. Checked the spot on POP110 PD. Found some misalignment of the beam.
The beam spot was aligned to the PD with PRMI locked. The value of POP110I almost doubled by the alignment
and recovered previous value of 400. Therefore previous normalization values of MICH 0.01 / PRCL 100 were restored.
- Placed PDA36A (Si 3.6mmx3.6mm) on the POP path that Jenne prepared. The gain knob was set to 40dB.
Since the original spot had been too small, a lens with f=50mm was inserted in order to expand the beam.
Connected the PD output to the SMA feedthrough on the ITMX table enclosure.
I found the BNC cable labeled "PO DC" hanging. Connected this cable to the enclosure SMA.
- Went to the LSC rack. Found the corresponding PO DC cable. Stole the POPDC channel from POP110I Bias T to this PO DC cable.
- Razor blade setup: Machined a junk Al bracket in order to fix a razor blade on it. Attached the Al bracket to a sliding stage.
- Locked the PRMI with REFL33I&AS55Q. Cut the beam into half by the razor blade.
- Made a temporary PRM_ASC_YAW filter.
Zero: 0Hz Pole: 2kHz
Resonant Gain 3.2Hz Q:2 Height 30dB
Butterworth 2nd-order 60Hz
=> Expected UGF 0.1Hz&10Hz
- CDS: By the work described in this entry, the POPDC signal was connected to the "MC" bank of the LSC.
BTW, the 11th row of the LSC output matrix is connected to the PRM_ASC_YAW.
- The "MC" servo input (i.e. the POPDC signal) was normalized by POP110I (without SQRTing).
- Engaged the PRM ASC path. Gradually increased the gain of PRM_ASC_YAW. G=+100 seemed to be the best so far.
It was visible that the spot on the POP CCD was stablized in yaw.
- The lock lasted for ~40min. Took several measurements, alignment adjustment, etc.
- Tweaking the PRM ASC unlocked the PRMI.
- Locked again. Switched from REFL33I/AS55Q (x1/x1) combination to REFL55I/REFL55Q (x1/x0.3) combination.
This also kept the lock more than 20min.
I fiddled around with the QPD that I'll use to replace Koji's temporary razor blade yaw sensor for detecting POP beam angular motion, and checked that it is working.
Using the Jenne Laser, I put beam onto the 4 different quadrants of the QPD, and saw that the Sum channel remained constant.
* I had the room lights off, since the PD elements are silicon.
* Beam size on the QPD as seen on an IR card was ~1mm diameter.
* With the beam on the QPD, I chose gain setting "G2" on the amplifier, since that was the only setting where neither the "current too high" nor the "current too low" LEDs were illuminated. I didn't measure the power going to the PD, but the Jenne Laser puts out 1.2mW, and there's a 50/50 BS, so I was getting about 600uW.
* I turned off the "zero/cal" switch on the back of the box, since I don't know how to set the zero. Since the X and Y channels are normalized by the Sum, you can't just block all light going to the PD and set the zero. There isn't a big change in the output levels with the zero/cal switch off, so I think it should be fine. (Previously, I set all 4 knobs - "zero" and "cal" for each X and Y - to approximately the center of their ranges. Once you hit the end of the range, you can keep turning the knob, but something inside makes a clicking sound ~once per revolution, and the signal level stops changing (for the zero knobs). Much like centering a beam on a PD, I found each edge of the range for each knob, and set the knobs in the centers by counting the number of turns. Anyhow, since I set the knobs to ~halfway, I think that explains why there isn't really a change whether the "zero/cal" switch is on or off.
* Using the steering mirror sending the beam to the QPD, I moved the beam around, and watched where I was going with an IR viewer. I see that as I move from quad-to-quad, the X and Y channels respond as I expect. If I only move the beam in X, I only see X response on a 'scope, and vice versa.
I can't do a real calibration until I get the QPD installed in place, so I can use the actual beam, but for now it looks like the QPD is responding nicely. Since Annalisa and Manasa are using the Arms for the evening, I'll work on putting the QPD on the POX table tomorrow.
I have mounted 2 2" G&H high reflective mirrors, to be used in the new POP path. Manasa and Annalisa are doing green things on their respective arms, so I will hopefully be able to install the new POP path after dinner tonight.
Here are photos of the current POP path, and my proposed POP layout. In the proposed layout, the optical components whose labels are shaded are the ones which will change.
I have placed the G&H mirrors and the Y1 as pictured in my proposed layout in elog 8649. The distance between the 2" lens and the PDs has increased, so the focus point is all wrong. I have measured the distances between optics on the table, and will pick new lenses and finish the POP layout later today or tomorrow.
For now, here are the powers measured using the Ophir power meter:
PRM-ITMY lock, POPDC was ~190 counts
5.29 uW after Y1 weird angle. Can't see beam before then to measure
5.27 uW before BS50
3.5 uW before razor PD
3.00 uW before 110PD
4.94 uW before y1 (after G&H's)
4.92 uW after y1
2.66 uW before razor PD
1.61 uW before 110PD
I have a lens solution for the new POP QPD, plotted below. To get the beam size, I started with the waist at the ITM, so the out of vacuum table starts around 6 meters on this plot. Also, "PD" is the QPD, but the position marked on the plot is the maximum distance from the 2nd lens. In reality, I will place it a few cm after the lens. Once I've got that laid out, I'll move the 110PD (and its lens) and the camera around so that they are in good spots relative to the beam size.
Here is a photo of the way I left the table last Thursday. The notations in orange indicate what I need to do to make the actual table match my lens solution.
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 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.
Or we just stuff any angle control things in to Angular Stabilization System without changing the model name.
The process name itself is not a big deal.
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.....
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.
- Locked PRMI with REFL165 I/Q
- Aligned the POP beam on the QPD. We found that the vertical motion of the beam appeared in the yaw signal, and horizontal motion in the pitch signal.
This was fixed by swapping the cables to the ADC. Later it turned out that this was caused by the calibration setup for the QPD.
We requested Jenne to fix the QPD on the table with the current orientation.
- Re-implemented the AC-coupled ASC servo. The filters were just copied from the previous PRM ASC servo (in the SUS ASC filter).
The same filter was installed to the pitch and yaw filter modules for now. The gains were adjusted to have some stable lock stretches.
The power spectra of C1:ASC-PRCL_YAW_IN1 and C1:ASC-PRCL_PIT_IN1 were attached.
The reference curves are the ones with the servo on. The other two are the free-running stability of the QPD output.
- Modified the up and down scripts for the PRM ASC for the new setup.
It first turns on the inputs of the filters and then turn on FM2/3.
It assumes that the outputs are engaged all time.
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.