40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log, Page 176 of 339  Not logged in ELOG logo
ID Date Author Type Category Subjectup
  7906   Wed Jan 16 18:52:49 2013 JenneUpdateLockingPRM - Flat mirror cavity plan

Game plan:

* Put 2" G&H mirror into BS chamber, in front of BS.

* Align it, lock cavity using an existing REFL PD.

* Align POP setup so I can use POP camera to take image of transmitted cavity mode, and actually take that image.

* Take image of face of PR2.

* Measure finesse of cavity using POP, or a Thorlabs PD at POP (looking at transmission through PR2) by scanning PRM, and infer cavity gain....compare with values in elog 7905.

* If time / inclination allow, take beam scan measurements of the REFL port.

I will not be able to do as was done in elog 6421 to look at the beam size at POP for non-resonating beams.  I expect ~0.1uW of light at POP in the non-resonant case:  100mW * 5.5% * 20ppm = 0.11microwatts.


  9634   Thu Feb 13 19:36:36 2014 KojiSummaryLSCPRM 2nd/4th violin filter added

Jenne and I noticed high pitch sound from our acoustic interferometer noise diagnostic system.
The frequency of this narrow band noise was 1256Hz, which is enough close to twice of the PRM violin mode freq.
After putting notch filter at 1256+/-25Hz at the violin filters, the noise is gone. Just in case I copied the same filters to all of the test masses.

Later, I found that the 4th violin modes are excited. Additional notch filters were added to "vio3" filter bank to mitigate the oscillation.

  9619   Mon Feb 10 18:59:25 2014 JenneUpdateASCPRM ASC better, but not great yet

I have turned off the 3.2Hz res gains in the PRC ASC loops, since those seem to make the loops unstable. 

Right now the pitch gain is -0.001, with FM1,3,9 on.  Yaw gain is -0.004, with FM1,3,9 on. 

Pitch gain can't increase by factor of 2 without oscillating. 

I tried to take transfer functions, but I think the ASC situation is really confusing, since I have OSEM damping, oplev damping, and this POP QPD damping on the PRM.  It's hard to get coherence without knocking the PRC out of lock, and it keeps looking like my gain is 0dB, with a phase of 0 degrees, from ~1 Hz to ~10 Hz.  Outside that range I haven't gotten any coherence.  Moral of the story is, I'm kind of puzzled. 

Anyhow, as it is right now, the ASC helps a bit, but not a whole lot.  I increased the trigger ON value, so that it shouldn't kick the PRM so much.  I wish that I had implemented a delay in the trigger, but I'm not in the mood to mess with the simulink diagrams right now.

  9620   Mon Feb 10 19:56:10 2014 ranaUpdateASCPRM ASC better, but not great yet

Ignoring the OSEM damping loops, the oplev servo loops make it so that the POP ASC loops do not see a simple pendulum plant, but instead see the closed loop response. Since the filter in the OL bank is proportional to f, this means that the open loop gain (OLG):


Which means that the CLG that the ASC sees is going to dip below unity in the band where the OL is on. For example, if the OL loop has a UGF of 5 Hz, it also has a lower UGF of ~0.15 Hz, which means that the ASC needs to know about this modified plant in this band.

For i/eLIGO, we dealt with this in this way: anti-OL in iLIGO

  9769   Mon Mar 31 23:57:22 2014 KojiSummaryASCPRM ASC characterization / design

A series of measurements / calculations for the PRM ASC characterization and servo design

1) Actuator characterization

The actuator responses of the PRM in pitch and yaw were measured (attachment figure 1). I believed the calibration of the oplev QPD to be
1 count/urad. The oplev servo loops were turned off at the FM inputs, and the filter banks were turned off so that the response has the open
loop transfer function except for the servo filter.

The measured transfer functions were fitted with LISO. The LISO results (c.f. the source codes) were shown in the figure. The responses also
include the 60Hz comb filter present in the input filters. The responses are well approximated by the single pendulum with f0 of 0.6-0.8 and q of 3.5 and 6.3.

From this measurement, the actuator responses of the PRM at DC are estimated to be 2.2 urad/cnt and 1.8 urad/cnt in pitch and yaw, respectively.

2) Sensor response of the POP QPD

As we already know how the actuators respond, the QPD optical gain can be characterized by measuring the actuator response of the QPD
(attachment figure 2). The QPD signals are such noisy that the response above 1Hz can't be measured with sufficient coherence. Below 1Hz,
the response is well represented by the actuator response measured with the oplev. From this measurement, the optical gains of the QPD
with respect to the PRM motion are 650 cnt/urad and 350 cnt/urad.

3) Open loop transfer function of the current ASC servo

By combining the above information with the servo setting of the servo filters, the open loop transfer functions of the PRM QPD ASC loops
were estimated (attachment figure 3). Actually the expected suppression of the fluctuation is poor. The yaw loop seems to have
too low gain, but in fact increasing gain is not so beneficial as there is no reasonable phase margin at higher frequency.

With the estimated openloop transfer functions and the measured free-running angular fluctuation, the suppressed angular spectra can be
estimated (attachment figure 4). This tells us that the suppression of the angular noise at around 3Hz is not sufficient in both pitch and yaw.
As there is no mechanical resonance in the actuator response at the frequency, intentional placement of poles and zeros in the servo filter is necessary.

4) Newly designed ASC filter

Here is the new design of the QPD ASC servo (attachment figure 5). The target upper UGF is 10Hz with the phase margin of 50 to 60deg.
The servo is AC coupled so that we still can tweak the alignment of the mirror.

As this servo is conditionally stable, at first we should close the loops with stable filter and then some boosts should be turned on.
Estimated suppressed fluctuation is shown in the attachment figure 6. We can see that the fluctuation was made well white between 0.5Hz to 10Hz.

The filter design is shown as follows:

FM1: zero at 0Hz, pole at 2000Hz, gain at 2000Hz = 2000

FM3: (boost)
zero: f: 0.5Hz q: 1  /  4.5Hz, q: 1 / f: 1Hz, q: 3
pole: f: 2Hz q: 3  / f: 2.7Hz, q: 2  / f: 1Hz, q: 15

FM9: (HF Roll-off)
pole: f: 40Hz q: 1.7
Servo gain: -0.028

FM1: zero at 0Hz, pole at 2000Hz, gain at 2000Hz = 2000

FM3: (boost)
zero: f: 0.7Hz q: 2  /  3Hz, q: 7 / f: 2Hz, q: 6
pole: f: 1.02Hz q: 10  / f: 4.5Hz, q: 0.8  / f: 1.5Hz, q: 10

FM9: (HF Roll-off)
pole: f: 40Hz q: 1.7
Servo gain: -0.0132


Attachment 1: PRM_OPLEV.pdf
Attachment 2: PRM_QPD.pdf
Attachment 3: OLTF_design.pdf
Attachment 4: QPD_spe.pdf
Attachment 5: OLTF_design2.pdf
Attachment 6: QPD_spe2.pdf
Attachment 7: 140328.zip
  16384   Wed Oct 6 15:04:36 2021 HangUpdateSUSPRM L2P TF measurement & Fisher matrix analysis

[Paco, Hang]

Yesterday afternoon Paco and I measured the PRM L2P transfer function. We drove C1:SUS-PRM_LSC_EXC with a white noise in the 0-10 Hz band (effectively a white, longitudinal force applied to the suspension) and read out the pitch response in C1:SUS-PRM_OL_PIT_OUT. The local damping was left on during the measurement. Each FFT segment in our measurement is 32 sec and we used 8 non-overlapping segments for each measurement. The empirically determined results are also compared with the Fisher matrix estimation (similar to elog:16373).


Fig. 1 shows one example of the measured L2P transfer function. The gray traces are measurement data and shaded region the corresponding uncertainty. The olive trace is the best fit model. 

Note that for a single-stage suspension, the ideal L2P TF should have two zeros at DC and two pairs of complex poles for the length and pitch resonances, respectively. We found the two resonances at around 1 Hz from the fitting as expected. However, the zeros were not at DC as the ideal, theoretical model suggested. Instead, we found a pair of right-half plane zeros in order to explain the measurement results. If we cast such a pair of right-half plane zeros into (f, Q) pair, it means a negative value of Q. This means the system does not have the minimum phase delay and suggests some dirty cross-coupling exists, which might not be surprising. 

Fig. 2 compares the distribution of the fitting results for 4 different measurements (4 red crosses) and the analytical error estimation obtained using the Fisher matrix (the gray contours; the inner one is the 1-sigma region and the outer one the 3-sigma region). The Fisher matrix appears to underestimate the scattering from this experiment, yet it does capture the correlation between different parameters (the frequencies and quality factors of the two resonances).

One caveat though is that the fitting routine is not especially robust. We used the vectfit routine w/ human intervening to get some initial guesses of the model. We then used a standard scipy least-sq routine to find the maximal likelihood estimator of the restricted model (with fixed number of zeros and poles; here 2 complex zeros and 4 complex poles). The initial guess for the scipy routine was obtained from the vectfit model.  

Fig. 3 shows how we may shape our excitation PSD to maximize the Fisher information while keeping the RMS force applied to the PRM suspension fixed. In this case the result is very intuitive. We simply concentrate our drive around the resonance at ~ 1 Hz, focusing on locations where we initially have good SNR. So at least code is not suggesting something crazy... 

Fig. 4 then shows how the new uncertainty (3-sigma contours) should change as we optimize our excitation. Basically one iteration (from gray to olive) is sufficient here. 

We will find a time very recently to repeat the measurement with the optimized injection spectrum.

Attachment 1: prm_l2p_tf_meas.pdf
Attachment 2: prm_l2p_fisher_vs_data.pdf
Attachment 3: prm_l2p_Pxx_evol.pdf
Attachment 4: prm_l2p_fisher_evol.pdf
  12476   Wed Sep 7 17:23:26 2016 gautamUpdateSUSPRM LR fixed for now

[johannes, gautam]

  • We took the heavy door off in the morning with Steve's help
  • The problem was quickly identified as the Al foil on the back of the PRM OSEMs (placed to mitigate scattered light making it into the OSEM that was making locking difficult) shorting out the pins on the rear of the OSEM
  • We decided against using a black glass beam stop behind the PRM - rather, we decided to go for Al foil hats that were
    1. More "domed" - so the back plane of the OSEM isn't in direct contact with the Al foil, though the hats themselves are secure and shouldn't simply fly off during pump down etc
    2. Have a piece of kapton (courtesy Koji from the OMC lab) in the dome so that even if the foil hats move around slightly, there should be no danger of accidentally shorting out any pins
  • Without removing the PRM OSEMs, we were only able to image UR and UL unambiguously showing that they have no filters. Not a single of the 5 spare 'short' OSEMs have filters. We have to open the ITMY chamber to reposition the OSEMs in the near future, which is when we will inspect SRM for filters.
  • Attachment #1 shows a picture of these foil hats - the ones actually put on are shaped slightly differently, but the idea is the same
  • Attachment #2 shows the PRM with its new OSEM hats (we also used a piece of clean copper wire to tie the OSEM cables to the tower on the bottom left of the cage as viewed from the BS-PRM chamber door)
  • After closing up the BS-PRM chamber, I locked the IMC to see if the input pointing had gone way off because of our work on the table and the reputation of the tip-tilts hysteresis - I can see weak flashes in the Y arm but not enough to lock - so I will tweak the alignment a little
  • Once I can recover the Y arm alignment, we can move on to peeling first contact and putting the X arm optics in.

Edit 7.30pm: I have managed to recover Y-arm in air locking, and the transmission is up at ~0.6 again which is what we were seeing prior to touching anything on the BS-PRM table, so it looks like the tip-tilt has not gone badly astray... I have also restored the Satellite boxes so that both PRM and SRM have their designated boxes

Attachment 1: IMG_3208.JPG
Attachment 2: IMG_3211.JPG
  12546   Tue Oct 11 00:43:50 2016 ericqUpdateSUSPRM LR problematic again

Tonight, and during last week's locking, we noticed something intermittently kicking the PRM. I've determined that PRM's LR OSEM is problematic again. The signal is coming in and out, which kicks the OSEM damping loops. I've had the watchdog tripped for a little bit, and here's the last ten minutes of the free swinging OSEM signal:

Here's the hour trend of the PRM OSEMS over the last 7 days a plot of just LR since the fix on the 9th of September.

It looks like it started misbehaving again on the evening of the 5th, which was right when we were trying to lock... Did we somehow jostle the suspension hard enough to knock the foil cap back into a bad spot?

  12549   Tue Oct 11 10:15:04 2016 SteveUpdateSUSPRM LR problematic again

It started here


Attachment 1: PRMalfoiled.png
  12551   Tue Oct 11 13:30:49 2016 gautamUpdateSUSPRM LR problematic again

Perhaps the problem is electrical? The attached plot shows a downward trend for the LR sensor output over the past 20 days that is not visible in any of the other 4 sensor signals. The Al foil was shorting the electrical contacts for nearly 2 months, so perhaps some part of the driver circuit needs to be replaced? If so a Satellite Box swap should tell us more, I will switch the PRM and SRM satellite boxes. It could also be a dying LED on the OSEM itself I suppose. If we are accessing the chamber, we should come up with a more robust insulating cap solution for the OSEMs rather than this hacky Al foil + kapton arrangement.

The PRM and SRM Satellite boxes have been switched for the time being. I had to adjust some of the damping loop gains for both PRM and SRM and also the PRM input matrix to achieve stable damping as the PRM Satellite box has a Side sensor which reads out 0-10V as opposed to the 0-2V that is usually the case. Furthermore, the output of the LR sensor going into the input matrix has been turned off.


  12552   Wed Oct 12 13:34:28 2016 gautamUpdateSUSPRM LR problematic again

Looks like what were PRM problems are now seen in the SRM channels, while PRM itself seems well behaved. This supports the hypothesis that the satellite box is problematic, rather than any in-vacuum shenanigans.

Eric noted in this elog that when this problem was first noticed, switching Satellite boxes didn't seem to fix the problem. I think that the original problem was that the Al foil shorted the contacts on the back of the OSEM. Presumably, running the current driver with (close to) 0 load over 2 months damaged that part of the Satellite box circuitry, which lead to the subsequent observations of glitchy behaviour after the pumpdown. Which begs the question - what is the quick fix? Do we try swapping out the LM6321 in the LR LED current driver stage? 

GV Edit Nov 2 2016: According to Rana, the load of the high speed current buffer LM6321 is 20 ohms (13 from the coil, and 7 from the wires between the Sat. Box and the coil). So, while the Al foil was shorting the coil, the buffer would still have seen at least 7 ohms of load resistance, not quite a short circuit. Moreover, the schematic suggests that that the kind of overvoltage protection scheme suggested in page 6 on the LM6321 datasheet has been employed. So it is becoming harder to believe that the problem lies with the output buffer. In any case, we have procured 20 of these discontinued ICs for debugging should we need them, and Steve is looking to buy some more. Ben Abbot will come by later in the afternoon to try and help us debug.

  10269   Thu Jul 24 13:01:39 2014 ericqUpdateSUSPRM OPLEV!

 Here's a fun fact: since the great computer failure of June2014, the PRM Oplev gains have been ZERO.



I've restored the gains to their old values, and measured the loop TFs.






  5203   Fri Aug 12 03:52:51 2011 kiwamuUpdateSUSPRM OSEM adjustment

[Suresh / Kiwamu]

 We tried adjusting the OSEMs on PRM, but we didn't complete it due to a malfunction on the coils.

The UL and LL coils are not working correctly, the forces are weak.

Tomorrow we will look into the satellite box, which is one of the suspects.


 During the adjustment we found that the POS excitation force was unequal in each sensor.

At the beginning we thought it's because of the difference of the sensitivity in each OSEM due to the bad OSEM orientations.

However it turned out that it comes from the actual force imbalance on each coil.

We checked the force of each coil by putting an offset (-2000 cnts) in each output digital filter and looked at the OSEM signals in time series.

The UL and LL coils are too weak and the responses are almost buried in the noise of the OSEMs in time series.

We briefly checked some analog electronics and found the DAC, AI board and deWhitening board were healthy.

We were able to see the right amount of voltage from the monitor pin on the front panel of the coil driver.

So something downstream are suspicious, including the satellite box, feedthrough and coils.

- - -

Although the coil issue, it could be worth trying to check the input matrix.

  5219   Sat Aug 13 01:54:18 2011 kiwamuUpdateSUSPRM OSEM adjustment part II

Adjustment of the PRM OSEMs are done. The coils turned out to be healthy.

The malfunction was fixed. It was because the UL OSEM was too deeply inserted and barely touching the AR surface of the mirror.


(OSEM adjustment)

 + Excited POS at 6.5 Hz with an amplitude of 3000 cnts by the LOCKIN oscillator.

 + Looked at the signal of each sensor in frequency domain.

 + Maximized the excitation peak for each of the four face OSEMs by rotating them.

 + Minimized the excitation peak in the SIDE signal by rotating it.

 + Adjusted the OSEM translational position so that they are in the midpoint of the OSEM range.


(POS sensitivity check)

From the view point of the matrix inversion, one thing we want to have is the equally sensitive face sensors and insensitive SIDE OSEM to the POS motion.

To check the success level of today's PRM adjusment, I ran swept sine measurements to take the transfer function from POS to each sensor.

The plots below are the results.  The first figure is the one measured before the adjustment and the second plot is the one after the adjustment.

As shown in the plot, before the adjustment the sensitivity of OSEMs were very different and the SIDE OSEM is quite sensitive to the POS motion.

So PRM used be in an extremely bad situation.

After the adjustment, the plot became much better.

The four face sensors have almost the same sensitivity (within factor of 3) and the SIDE is quite insensitive to the POS motion.

before.png after.png

Quote from #5203

 We tried adjusting the OSEMs on PRM, but we didn't complete it due to a malfunction on the coils.

The UL and LL coils are not working correctly, the forces are weak.

  9627   Wed Feb 12 14:05:16 2014 ericqUpdateSUSPRM Oplev Checked Out


Steve fixed the PRM oplev pointing. I turned on the loops and measured the OLG, then set the pitch and yaw gains such that the upper UGF was ~8Hz (motivated by Jenne's loop design in ELOG 9401)

  • Pitch gain: +7
  • Yaw Gain: -5

I then measured the oplev spectra of the optics as they were aligned for PRMI. (OSEMs on, oplevs on, LSC off, and ASC off)

Next, Jenne and I need to fix the ASC loop such that it properly accounts for the oplev loop. 



  9617   Mon Feb 10 16:20:28 2014 JenneUpdateGeneralPRM QPD recentered

In an effort to stop the PRC from wiggling around so much, I recentered the POP QPD after maximizing the POPDC power when locked on carrier.  The beam was basically off the QPD in yaw, and at half-range in pitch.

  12481   Sat Sep 10 14:26:01 2016 ranaUpdateGeneralPRM SRM alignment

For the PRM, I aligned it until the arm flashes were maximized and the REFL camera showed a centered spot with dips happening during the arm pops. AS port was more messy since the Michelson alignment wasn't perfect, but the spots were both near the center of the cam and the SRM alignment maximized the wangy fringiness of the image as well as the angry cat meow sounds that the full IFO makes as heard through the DAFI (listening to POX).

On Monday, Osamu should be back and can help with doors and then alignment recovery and locking.

Attachment 1: Osamu.JPG
  12482   Mon Sep 12 17:15:22 2016 JohannesUpdateGeneralPRM SRM alignment

[Gautam, Steve, Johannes]

We put on the remaining heavy doors on the chambers (ITMY, ITMX,ETMX, in this order) this morning. On the ITMY and ETMX tables we placed old OpLev steering mirrors that are clean and baked as witness plates such that may one day provide some insight into dust accumulation on optics.

With the heavy doors on we confirmed that we were still able to lock both IFO arms and used the dither scripts to optimize the alignment. Following that we centered all OpLevs and aligned the X and Y green beams.

ITMY table witness plate
ETMX table witness plate


  8533   Tue May 7 03:14:06 2013 JenneUpdateSUSPRM SUS_LSC violin (FM5) set to correct frequency

While looking over Koji's shoulder earlier, I noticed the big peak in the PRM yaw spectrum (and I was starting to get annoyed by the hum....the fibox is so useful in motivating tasks that otherwise get looked over!) 

I used DTT's peak find feature (cursor tab, enable both cursors, select Peak X/Y as your 'statistic', set the 2 cursors to be on either side of the desired peak) to find the frequency of the PRM's violin mode.  It is 627.75 Hz. I adjusted FM5 of the C1:SUS-PRM_LSC filter bank (the "violin" filter) to be centered around this frequency, with the start and stop freqs +\- 4Hz.  I plotted the filter linearly in frequency to ensure that my target freq was not too close to either side of the bandstop.  After loading and engaging the new filter, the hum slowly started to go away. 

Note, for posterity:  The bandstop used to be centered around ~645 Hz or so.  I assume this is a copy-and-paste situation, where we hadn't gone through to check the exact frequency for each optic.

  9048   Wed Aug 21 23:50:40 2013 KojiUpdateSUSPRM SUS_LSC violin (FM5) set to correct frequency

[Jenne Koji]

It seems that the PRM violin mode freqs shifted from 625-ish to 640Hz.
The peaks rang up because of the servo.

Once the notch freq was shifted to 640Hz, the violin mode started to decay.

ellip("BandStop",4,1,90,636,644) gain(1.12202)

  12602   Mon Nov 7 16:05:55 2016 gautamUpdateSUSPRM Sat. Box. Debugging

Short summary of my Sat. Box. debugging activities over the last few days. Recall that the SRM Sat. Box has been plugged into the PRM suspension for a while now, while the SRM has just been hanging out with no electrical connections to its OSEMs.

As Steve mentioned, I had plugged in Ben's extremely useful tester box (I have added these to the 40m Electronics document sub-tree on the DCC) into the PRM Sat. Box and connected it to the CDS system over the weekend for observation. The problematic channel is LR.  Judging by Steve's 2 day summary plots, LR looks fine. There is some unexplained behavior in the UR channel - but this is different from the glitchy behaviour we have seen in the LR channel in the past. Moreover, subsequent debugging activities did not suggest anything obviously wrong with this channel. So no changes were made to UR. I then pulled out the PRM sat.box for further diagnostics, and also, for comparison, the SRM sat. box which has been hooked up to the PRM suspension as we know this has been working without any issues. 

Tracing out the voltages through the LED current driver circuit for the individual channels, and comparing the performance between PRM and SRM sat. boxes, I narrowed the problem down to a fault in either the LT1125CSW Quad Op-Amp IC or the LM6321M current driver IC in the LR channel. Specifically, I suspected the output of U3A (see Attachment #1) to be saturated, while all the other channels were fine. Looking at the spectrum at various points in the circuit with an SR785, I could not find significant difference between channels, or indeed, between the PRM/SRM boxes (up to 100kHz). So I decided to swap out both these ICs. Just replacing the OpAmp IC did not have any effect on the performance. But after swapping out the current buffer as well, the outputs of U3A and U11 matched those of the other channels. It is not clear to me what the mode of failure was, or if the problem is really fixed. I also checked to make sure that it was indeed the ICs that had failed, and not the various resistors/capacitors in the signal path. I have plugged in the PRM sat. box + tester box setup back into our CDS data acquisition for observation over a couple of days, but hopefully this does the job... I will update further details over the coming days.

I have restored control to PRM suspensions via the working SRM sat. box. The PRM Sat. Box and tester box are sitting near the BS/PRM chamber in the same configuration as Steve posted in his earlier elog for further diagnostics...

GV Edit 2230 hrs 7Nov2016: The signs from the last 6 hours has been good - see the attached minute trend plot. Usually, the glitches tend to show up in this sort of time frame. I am not quite ready to call the problem solved just yet, but I have restored the connections to the SRM suspension (the PRM and SRM Sat. Boxes are still switched). I've also briefly checked the SRM alignment, and am able to lock the DRMI, but the lock doesn't hold for more than a few seconds. I am leaving further investigations for tomorrow, let's see how the Sat. Box does overnight.

Attachment 1: D961289-B2.pdf
Attachment 2: PRMSatBoxtest.png
  12606   Tue Nov 8 11:54:38 2016 gautamUpdateSUSPRM Sat. Box. looks to be fixed

Looks like the PRM Sat. Box is now okay, no evidence of the kind of glitchy behaviour we are used to seeing in any of the 5 channels.

GV Edit 2230 hrs 7Nov2016: The signs from the last 6 hours has been good - see the attached minute trend plot. Usually, the glitches tend to show up in this sort of time frame. I am not quite ready to call the problem solved just yet, but I have restored the connections to the SRM suspension (the PRM and SRM Sat. Boxes are still switched). I've also briefly checked the SRM alignment, and am able to lock the DRMI, but the lock doesn't hold for more than a few seconds. I am leaving further investigations for tomorrow, let's see how the Sat. Box does overnight.


  3913   Sat Nov 13 16:57:21 2010 valeraConfigurationElectronicsPRM Side OSEM transimpedance change

Now that we have increased the range of the AA to +/- 10 V I have increased the PRM side OSEM transimpedance from 29 kV/A to 161 kV/A by changing the R64 in the satellite box. The first attached plot shows the ADC input spectrum before and after the change with analog whitening turned off. The PD voltage readback went up from 0.75 to 4.2 V. The second attached plot shows the sensor, ADC, and projected shot noise with analog whitening turned on and compensated digitally. The ADC calibration is 20 V/ 32768 cts. The PRM damping loops are currently disabled.

I checked for oscillation by looking at the monitor point at the whitening board. There was no obvious oscillation on a scope - the signal was 20 mV p-p on 1 us scale which was very similar to the LL channel.

Attachment 1: PRM-SD-ADC.pdf
Attachment 2: PRM-SD-Current.pdf
  9614   Sat Feb 8 15:14:18 2014 ericqUpdateLSCPRM Sideband Splitting


Today, I kicked the PRM to see the sideband splitting in POP110. 

First, we can qualitatively see we moved in the right direction! (See ELOG 9490)


I fit the middle three peaks to a sum of two Lorentzian profiles ( I couldn't get Airy peaks to work... but maybe this is ok since I'm just going to use the location parameter?), and looked at the sideband splitting as a fraction of the FSR, in the same way as in Gabriele's ELOG linked above.

This gave: c / (4 * f55) * (dPhi / FSR) = 0.014 +- .001 

Since the PRC length with simultaneous resonance (to 1mm) is given by c / (4 * f11) = 6.773, this means our length is either 6.759m or 6.787m (+- .001). Given the measurement in ELOG 9588, I assume that we are on the short side of the simultaneous resonance. Thus

The sideband splitting observed from this kick indicates a PRC length of 6.759m +- 1mm

  5091   Tue Aug 2 11:02:52 2011 JenneUpdateSUSPRM Watchdog tripped

I found PRM watchdog tripped.  It's all better now.

  8563   Mon May 13 17:24:38 2013 JenneUpdateWienerFilteringPRM YAW Wiener filtering

I have done a quicky offline Wiener filter to check how much PRM yaw motion we can subtract using a seismometer in the corner station.  This work may be redundant since Koji got the POP beam shadow sensor feedback loop working on Friday night.

Anyhow, for now, I used the GUR2 channels, since GUR2 was underneath the ITMX chamber (at the north edge of the POX table).  Note that Zach is currently borrowing this seismometer for the week.

I used GUR2_X, GUR2_Y and GUR2_Z to subtract from the PRM_SUSYAW_IN1 channel (the filename of the figure says "GUR1", but that's not true - GUR1 is at the Yend).  All 4 of these channels had been saved at 2kHz, but I downsampled to 256 (I probably should downsample to something lower, like 64, but haven't yet).  There is no pre-filtering or pre-weighting of the data, and no lowpass filters applied at the end, so I haven't done anything to remove the injected noise at higher freqs, which we obviously need to do if we are going to implement this online.


If I compare this to Koji's work (elog 8562), at 3.2Hz, he gets a reduction of 2.5x, while this gets 10x.  At all other frequencies, Koji's work beats this, and Koji's method gets reduction from ~0.03Hz - 10Hz, while this is only getting reduction between 0.4Hz and 5Hz.  Also, this does not include actuator noise, so the actual online subtraction may not be quite as perfect as this figure.

  16343   Mon Sep 20 12:20:31 2021 PacoSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

[yehonathan, paco, anchal]

We attempted to find any symptoms for actuation problems in the PRMI configuration when actuated through BS and PRM.

Our logic was to check angular (PIT and YAW) actuation transfer function in the 30 to 200 Hz range by injecting appropriately (f^2) enveloped excitations in the SUS-ASC EXC points and reading back using the SUS_OL (oplev) channels.

From the controls, we first restored the PRMI Carrier to bring the PRM and BS to their nominal alignment, then disabled the LSC output (we don't need PRMI to be locked), and then turned off the damping from the oplev control loops to avoid supressing the excitations.

We used diaggui to measure the 4 transfer functions magnitudes PRM_PIT, PRM_YAW, BS_PIT, BS_YAW, as shown below in Attachments #1 through #4. We used the Oplev calibrations to plot the magnitude of the TFs in units of urad / counts, and verified the nominal 1/f^2 scaling for all of them. The coherence was made as close to 1 as possible by adjusting the amplitude to 1000 counts, and is also shown below. A dip at 120 Hz is probably due to line noise. We are also assuming that the oplev QPDs have a relatively flat response over the frequency range below.

Attachment 1: PRM_PIT_ACT_TF.pdf
Attachment 2: PRM_YAW_ACT_TF.pdf
Attachment 3: BS_PIT_ACT_TF.pdf
Attachment 4: BS_YAW_ACT_TF.pdf
  16345   Mon Sep 20 14:22:00 2021 ranaSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

I suggest plotting all the traces in the plot so we can see their differences. Also remove the 1/f^2 slope so that we can see small differences. Since the optlev servos all have low pass filters around 15-20 Hz, its not necessary to turn off the optlev servos for this measurement.

I think that based on the coherence and the number of averages, you should also be able to use Bendat and Piersol so estimate the uncertainy as a function of frequency. And we want to see the comparison coil-by-coil, not in the DoF basis.

4 sweeps for BS and 4 sweeps for PRM.

  16358   Thu Sep 23 15:29:11 2021 PacoSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

[Anchal, Paco]

We had a second go at this with an increased number of averages (from 10 to 100) and higher excitation amplitudes (from 1000 to 10000). We did this to try to reduce the relative uncertainty a-la-Bendat-and-Pearsol

\delta G / G = \frac{1}{\gamma \sqrt{n_{\rm avg}}}

where \gamma, n_{\rm avg} are the coherence and number of averages respectively. Before, this estimate had given us a ~30% relative uncertainty and now it has been improved to ~ 10%. The re-measured TFs are in Attachment #1. We did 4 sweeps for each optic (BS, PRM) and removed the 1/f^2 slope for clarity. We note a factor of ~ 4 difference in the magnitude of the coil to angle TFs from BS to PRM (the actuation strength in BS is smaller).

For future reference:

With complex G, we get complex error in G using the formula above. To get uncertainity in magnitude and phase from real-imaginary uncertainties, we do following (assuming the noise in real and imaginary parts of the measured transfer function are incoherent with each other):
G = \alpha + i\beta

\delta G = \delta\alpha + i\delta \beta

\delta |G| = \frac{1}{|G|}\sqrt{\alpha^2 \delta\alpha^2 + \beta^2 \delta \beta^2}

\delta(\angle G) = \frac{1}{|G|^2}\sqrt{\alpha^2 \delta\alpha^2 + \beta^2 \delta\beta^2} = \frac{\delta |G|}{|G|}

Attachment 1: BS_PRM_ANG_ACT_TF.pdf
  16371   Fri Oct 1 14:25:27 2021 yehonathanSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

{Paco, Yehonathan, Hang}

We measured the sensing PRMI sensing matrix. Attachment 1 shows the results, the magnitude of the response is not calibrated. The orthogonality between PRCL and MICH is still bad (see previous measurement for reference).

Hang suggested that since MICH actuation with BS and PRM is not trivial (0.5*BS - 0.34*PRM) and since PRCL is so sensitive to PRM movement there might be a leakage to PRCL when we are actuating on MICH. So there may be a room to tune the PRM coefficient in the MICH output matrix.

Attachment 2 shows the sensing matrix after we changed the MICH->PRM coefficient in the OSC output matrix to -0.1.

It seems like it made things a little bit better but not much and also there is a huge uncertainty in the MICH sensing.

Attachment 1: MICH_PRM_-0.34.png
Attachment 2: MICH_PRM_-0.1.png
  16374   Mon Oct 4 16:00:57 2021 YehonathanSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

{Yehonathan, Anchel}

In an attempt to fix the actuation of the PRMI DOFs we set to modify the output matrix of the BS and PRM such that the response of the coils will be similar to each other as much as possible.

To do so, we used the responses at a single frequency from the previous measurement to infer the output matrix coefficients that will equilize the OpLev responses (arbitrarily making the LL coil as a reference). This corrected the imbalance in BS almost completely while it didn't really work for PRM (see attachment 1).

The new output matrices are shown in attachment 2-3.

Attachment 1: BS_PRM_ANG_ACT_TF_20211004.pdf
BS_PRM_ANG_ACT_TF_20211004.pdf BS_PRM_ANG_ACT_TF_20211004.pdf BS_PRM_ANG_ACT_TF_20211004.pdf BS_PRM_ANG_ACT_TF_20211004.pdf
Attachment 2: BS_out_mat_20211004.txt
9.839999999999999858e-01 8.965770586285104482e-01 9.486710352885977526e-01 3.099999999999999978e-01
1.016000000000000014e+00 9.750242104232501594e-01 -9.291967546765563801e-01 3.099999999999999978e-01
9.839999999999999858e-01 -1.086765190351774768e+00 1.009798093279114628e+00 3.099999999999999978e-01
1.016000000000000014e+00 -1.031706735496689786e+00 -1.103142995587099939e+00 3.099999999999999978e-01
0.000000000000000000e+00 0.000000000000000000e+00 0.000000000000000000e+00 1.000000000000000000e+00
Attachment 3: PRM_out_mat_20211004.txt
1.000000000000000000e+00 1.033455230230304611e+00 9.844796282226820905e-01 0.000000000000000000e+00
1.000000000000000000e+00 9.342329554807877745e-01 -1.021296201828568506e+00 0.000000000000000000e+00
1.000000000000000000e+00 -1.009214777246558503e+00 9.965113815550634691e-01 0.000000000000000000e+00
1.000000000000000000e+00 -1.020129700278567197e+00 -9.973560027273553619e-01 0.000000000000000000e+00
0.000000000000000000e+00 0.000000000000000000e+00 0.000000000000000000e+00 1.000000000000000000e+00
  16375   Mon Oct 4 16:10:09 2021 ranaSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

not sure that this is necessary. If you look at teh previous entries Gautam made on this topic, it is clear that the BS/PRM PRMI matrix is snafu, whereas the ITM PRMI matrix is not.

Is it possible that the ~5% coil imbalance of the BS/PRM can explain the observed sensing matrix? If not, then there is no need to balance these coils.

  16383   Tue Oct 5 20:04:22 2021 PacoSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

[Paco, Rana]

We had a look at the BS actuation. Along the way we created a couple of issues that we fixed. A summary is below.

  1. First, we locked MICH. While doing this, we used the /users/Templates/ndscope/LSC/MICH.yml ndscope template to monitor some channels. I edited the yaml file to look at C1:LSC-ASDC_OUT_DQ instead of the REFL_DC. Rana pointed out that the C1:LSC-MICH_OUT_DQ (MICH control point) had a big range (~ 5000 counts rms) and this should not be like that.
  2. We tried to investigate the aforementioned thing by looking at the whitening / uwhitening filters but all the slow epics channels where "white" on the medm screen. Looking under CDS/slow channel monitors, we realized that both c1iscaux and c1auxey were weird, so we tried telnet to c1iscaux without success. Therefore, we followed the recommended wiki procedure of hard rebooting this machine. While inside the lab and looking for this machine, we touched things around the 'rfpd' rack and once we were back in the control room, we couldn't see any light on the AS port camera. But the whitening filter medm screens were back up.
  3. While rana ssh'd into c1auxey to investigate about its status, and burtrestored the c1iscaux channels, we looked at trends to figure out if anything had changed (for example TT1 or TT2) but this wasn't the case. We decided to go back inside to check the actual REFL beams and noticed it was grossly misaligned (clipping)... so we blamed it on the TTs and again, went around and moved some stuff around the 'rfpd' rack. We didn't really connect or disconnect anything, but once we were back in the control room, light was coming from the AS port again. This is a weird mystery and we should systematically try to repeat this and fix the actual issue.
  4. We restored the MICH, and returned to BS actuation problems. Here, we essentially devised a scheme to inject noise at 310.97 Hz and 313.74. The choice is twofold, first it lies outside the MICH loop UGF (~150 Hz), and second, it matches the sensing matrix OSC frequencies, so it's more appropriate for a comparison.
  5. We injected two lines using the BS SUS LOCKIN1 and LOCKIN2 oscilators so we can probe two coils at once, with the LSC loop closed, and read back using the C1:LSC-MICH_IN1_DQ channel. We excited with an amplitude of 1234.0 counts and 1254 counts respectively (to match the ~ 2 % difference in frequency) and noted that the magnitude response in UR was 10% larger than UL, LL, and LR which were close to each other at the 2% level.


After rana left, I did a second pass at the BS actuation. I took TF measurements at the oscilator frequencies noted above using diaggui, and summarize the results below:

TF UL (310.97 Hz) UR (313.74 Hz) LL (310.97 Hz) LR (313.74 Hz)
Magnitude (dB) 93.20 92.20 94.27 93.85
Phase (deg) -128.3 -127.9 -128.4 -127.5

This procedure should be done with PRM as well and using the PRCL instead of MICH.

  16385   Wed Oct 6 15:39:29 2021 AnchalSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

Note that your tests were done with the output matrix for BS and PRM in the compensated state as done in 40m/16374. The changes made there were supposed to clear out any coil actuation imbalance in the angular degrees of freedom.

  16393   Tue Oct 12 11:32:54 2021 YehonathanSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

Late submission (From Thursday 10/07):

I measured the PRMI sensing matrix to see if the BS and PRMI output matrices tweaking had any effect.

While doing so, I noticed I made a mistake in the analysis of the previous sensing matrix measurement. It seems that I have used the radar plot function with radians where degrees should have been used (the reason is that the azimuthal uncertainty looked crazy when I used degrees. I still don't know why this is the case with this measurement).

In any case, attachment 1 and 2 show the PRMI radar plots with the modified output matrices and and in the normal state, respectively.

It seems like the output matrix modification didn't do anything but REFL55 has good orthogonality. Problem gone??

Attachment 1: modified_output_matrices_radar_plots.png
Attachment 2: normal_output_matrices_radar_plots.png
  16394   Tue Oct 12 16:39:52 2021 ranaSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

should compare side by side with the ITM PRMI radar plots to see if there is a difference. How do your new plots compare with Gautam's plots of PRMI?

  16402   Thu Oct 14 13:40:49 2021 YehonathanSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

Here is a side by side comparison of the PRMI sensing matrix using PRM/BS actuation (attachment 1) and ITMs actuation (attachment 2). The situation looks similar in both cases. That is, good orthogonality on REFL55 and bad seperation in the rest of the RFPDs.


should compare side by side with the ITM PRMI radar plots to see if there is a difference. How do your new plots compare with Gautam's plots of PRMI?


Attachment 1: BSPRM_Actuation_Radar_plots.png
Attachment 2: ITM_Actuation_Radar_plots.png
  5618   Tue Oct 4 19:31:17 2011 kiwamuUpdateSUSPRM and BS oplev laser died

The He-Ne laser which has been used for the PRM and BS oplevs were found to be dead.

According to the trend data shown below, it became dead during the dolphin issue.

(During the dolphin issue the output from the oplev QPDs are digitally zero)


  5620   Wed Oct 5 11:33:25 2011 steveUpdateSUSPRM and BS oplev laser replaced


JDSU 1103P died after 4 years of service. It was replaced with new identical head of 2.9 mW output. The power supply was also changed.

The return spots of 0.04 mW  2.5 mm diameter on qpds are BS  3,700 counts and PRM 4,250 counts.


  11227   Mon Apr 20 16:42:48 2015 steveUpdateSUSPRM and BS oplev laser replaced

The laser below is dead. JDSU 1103P, SN P845655 lived for 3.5 years.



JDSU 1103P died after 4 years of service. It was replaced with new identical head of 2.9 mW output. The power supply was also changed.

The return spots of 0.04 mW  2.5 mm diameter on qpds are BS  3,700 counts and PRM 4,250 counts.


It was replaced by JDSU P/N 22037130,( It has a new name for 1103P Uniphase ) sn P919639 of mfg date 12-2014

Beam shape at 5 m nicely round. Output power 2.8 mW of 633 nm

BS spot size on qpd ~1 mm &  60 micro W

PRM spot size on qpd ~1 mm & 50 micro W

Attachment 1: newOplevLaser.png
  11246   Fri Apr 24 23:40:15 2015 ranaUpdateSUSPRM and BS oplev laser replaced

Recently, Steve replaced the HeNe which was sourcing the BS & PRM OL. After replacement, no one checked the beam sizes and we've been living with a mostly broken BS OL. The beam spot on the QPD was so tiny that we were seeing the 'beam is nearly the size of the segment gap' effect.

Today I removed 2 of the lenses which were in the beam path: one removed from the common PRM/BS path, and one removed from the PRM path. The beams on both the BS & PRM got bigger. The BS beam is bigger by a factor of 7. I've increased the loop gains by a factor of 6 and now the UGFs are ~6 Hz. The loop gains were much too high with the small beam spots that Steve had left there. I would prefer for the beams to be ~1.5-2x smaller than they are now, but its not terrible.

Many of the mounts on the table are low quality and not constructed stably. One of the PRM turning mirror mounts twisted all the way around when I tried to align it. This table needs some help this summer.

In the future: never try locking after an OL laser change. Always redo the telescope and alignment and check the servo shape before the OL job is done.

Also, I reduced the height of the RG3.3 in the OL loops from 30 to 18 dB. The BS OL loops were conditionally stable before and thats a no-no. It makes it oscillate if it saturates.

Attachment 1: BSOL.pdf
  3278   Fri Jul 23 15:54:38 2010 kiwamuUpdateSUSPRM and TT installed

[ Jenne, Koji and Kiwamu]

 We have installed the PRM and the tip-tilt (TT) in the BS chamber.

We have started the in-vac work which takes about a week.

Today's mission was dedicated to installing the PRM and two TTs, one for the PRC and the other for the SRC, on the BS table in the chamber.

The work has been smoothly performed and we succeeded in installation of the PRM and a TT for the PRC.

But unfortunately the other TT got broken during its transportation from Bob's clean room.


 (what we did)

 (1) opened the light door of the BS chamber.

 (2) moved the BS tower to the right position according to Koji's layout drawing.

    - Prior to this work we screwed down the earthquake stops so that the mirror is fixed to the tower. Also we disabled the watchdog.

    - When moving it we used an allen key as a lever with an screw as a fulcrum. This idea was suggested by Jenne and it really worked well.

     The reason why we used this technique is that if we slide the tower by hands the tower can't go smoothly and it may sometimes skips.

     After that we checked the postion from some reference screw holes by using a caliper and we made sure that it was on the right position.

 (3) removed all of the square-shaped mirrors.

    - After this removal the mirrors were wrapped by aluminum foils and put in a usual clear box.

 (4) removed some optics because they had made the chamber space crowded.

    - These were also wrapped by aluminum foils and put in the box. Later we will put them back to the BS table.

 (5) brought the PRM tower from the Bob's clean room  and put it on the BS table.

   - The position of the PRM were coarsely aligned since we still don't have any 1064 beam going through the PRM.

 (6) brought two TTs also from Bob's clean room and put one of the TTs on the table.  

   - The position of the installed TT was coarsely adjusted. 

   - After we brought them we removed the aluminum foils covering the TTs and we found the wire of a TT got broken.

     It may have been damaged during its transportation from Bob's room because it was fine before the transportation.

 (7) closed the door


(the next things to do)

  * Installation of the OSEMs to the PRM

  * Installation of the pick off mirror and its associated optics

  * Arrangement of  the pzt mirror


Attachment 1: DSC_2275.JPG
  3281   Fri Jul 23 18:55:25 2010 kiwamuUpdateSUSPRM and TT installed

I updated the last entry.

  8236   Tue Mar 5 23:37:11 2013 yutaUpdateSUSPRM angular motion spectra

I measured PRM angular motion spectra (in daytime today).
PRM angular motion is ~ 10 urad in RMS when undamped and ~1 urad in RMS when damped.
If PR2/PR3 angular motions are something like this, and their motion are not enhanced when PRC is locked, measured g-factor of PRC looks OK. But considering the error we have, maybe we are not OK yet. We need calculation.


  3746   Wed Oct 20 18:17:35 2010 Suresh, JenneUpdateSUSPRM assembly

We have positioned the guide rod and the wire-stand-off on the optic in the axial direction. 

We have selected six magnets whose magnetic strength is +/-5% of their mean strength (180 Gauss).  The measurement was made as follows:

1) each magnet was placed on its  end, on the top of a beaker held upside down. 

2) The Hall probe was placed directly under the magnet touching the glass from the other side (the inside of the beaker). 

This ensures that the relative position of the magnet and the probe remains fixed during a measurement.  And ensures that their separation is the same for each of the magnets tested. 

With this procedure the variation in the measured B field is less than +/- 10% in the sample of magnets tested.

  3824   Fri Oct 29 14:16:26 2010 JenneUpdateSUSPRM baking

[Suresh, Jenne]

We took a look-see at the PRM after the gluing from last night.  The balance is still okay.  The reflected beam is a teeny bit below the laser aperture (center of the beam maybe ~2mm below, so ~1mRad low).  This is within our okay range, since the DC offset that the OSEMs will give will be even more, and the coils can definitely handle this kind of offset.

We took the optic out of the tower, and gave it to Bob and Daphen to bake over the weekend.

  15880   Mon Mar 8 17:09:29 2021 gautamUpdateSUSPRM coil actuators heavily imbalanced

I realized I hadn't checked the PRM actuator as thoroughly as I had the others. I used the Oplev as a sensor to check the coil balancing, and I noticed that while all 4 coils show up with the expected 1/f^2 profile at the Oplev error point, the actuator gains seem imbalanced by a factor of ~5. The phase isn't flat because of some filters in the Oplev electronics I guess. The Oplev loops were disabled for the measurement, and the excitations were small enough that the beam stayed reasonably well centered on the QPD throughout. This seems very large to me - the values in the coil output filter gains lead me to expect more like a ~10% mismatch in the actuation strenghts, and similar tests on other optics in the past, e.g. ETMY, have yielded much more balanced results. I'm collecting some free-swinging PRM data now as an additional check. I verified that all the coils seem actuatable at least, by applying a 500 ct step at the offset of the coil output FM, and saw that the optic moved (it was such a test that revealed that MC1 had a busted actuator some time ago). If the eigenmode spectra look as expected, I think we can rule out broken magnets, but I suppose the magnets could still be not well matched in strength?

Attachment 1: PRMact.pdf
  8093   Sat Feb 16 17:27:26 2013 yutaUpdateSUSPRM coil balanced

PRM coil gains and f2a filters are adjusted for PRMI work.
It seems like UR/LL coil gains were ~10 % larger than others, and f2a filters changed by few %.

What I did:
  1. Tried to lock PRMI but when I turn on PRCL lock, PRM reflection looked like it tends to go up and left in REFL camera (last night).

  2. So, I set up PRM oplev back, by steering PRM oplev mirrors on the BS table (last night).

  3. Turned PRM oplev sero on, f2a filters off, and ran

> /opt/rtcds/caltech/c1/scripts/SUS/F2P_LOCKIN.py -o PRM

  I had to fix F2P_LOCKIN.py because it assumed some OUTPUT buttons in LOCKIN1 filters to be ON.
  Also, I had to restore filters in LOCKIN1 (8.5 Hz bandpass filter etc.) because their names were changed. To do this, I copied filters needed from /opt/rtcds/caltech/c1/chans/filter_archive/c1sus/C1SUS_110916_162512.txt, renamed LOCKIN1_(I|Q|SIG) with LOCKIN1_DEMOD_(I|Q|SIG), and pasted to the current filter bank file. I checked that they look OK with foton after editing the file.

  This measurement takes about 30 minutes. I ran several times to check consistency. There was ~ 0.1 % standard deviation for the measurement results.

  4. By putting measured coupling coefficients and PRM pendulum frequency (f0=0.993 Hz) to /opt/rtcds/caltech/c1/scripts/SUS/F2Pcalc.py, I got new f2a filters.

  5. Overwrote f2a filters in C1:SUS-PRM_TO_COIL_(1-4)_1 FM1 with new ones, and turned  new f2a filters on.

  Below is the DC gain adjustment result from F2P_LOCKIN.py;

multiplier factors are :
UL = 1.141525
UR = 0.879997
LR = 1.117484
LL = 0.860995
Set C1:SUS-PRM_ULCOIL_GAIN to 1.04990177238
Set C1:SUS-PRM_URCOIL_GAIN to -0.983396190716
Set C1:SUS-PRM_LRCOIL_GAIN to 0.954304254663
Set C1:SUS-PRM_LLCOIL_GAIN to -0.971356852259

  So, UR/LL coil gains somehow got ~10 % larger than other two since last coil balancing.

  Measured coupling coefficients from F2P_LOCKIN.py were

- measured coupling coefficients are :
P2P(POS=>PIT) = 0.014993
P2Y(POS=>YAW) = 0.001363

  New f2a filters are plotted below. They look fairly different compared with previous ones.


We need better F2P_LOCKIN.py:
  Some one should make F2P_LOCKIN.py better. The main problem is the sudden gain change when starting diagonalization at low frequency. It sometimes trips off the watchdog.

Some elogs related:
  Kiwamu made f2a filters in Sep 2011: elog #5417
  Koji adjusting DC gains in Jan 2013: elog #7969

  8096   Sun Feb 17 19:27:19 2013 ranaUpdateSUSPRM coil balanced

 I will check out the AS55 situation tomorrow. Just put it on my desk.

MC Autolocker was disabled - I enabled it.

For the F2P.py, you should look at how we did this with the script written 8 years ago in csh. There we stored the initial values in a file (so they don't get blow away if someone does CTRL-C). Your python script should have a trap for SIGINT so that it dies gracefully by restoring the initial values. In order to have the smooth value adjustment, you must first set the TRAMP field for all the coil gains to 2 and then switch. Make sure that the lockin ignores the first few seconds of data after making this switch or else it will be hugely biased by this transient.

For the PRM OL use as a F2A reference, you also have to take into account that the OL beam is hitting the PRM surface at non-normal incidence. IF it is a large angle, there will be a systematic error in the setting of the F2Y values.

  8065   Tue Feb 12 00:14:00 2013 yutaUpdateLockingPRM coil balancing

We tried to lock half-PRC tonight, but we couldn't. Why?? I could lock yesterday.
It locks for ~ 1 sec, but it beam spot motion freaks out mainly in yaw.
I tried to balance PRM coils, but oplev beam was clipped by MMT1......

What I did:
  1. Found elog #5392 and found F2P_LOCKIN.py

  2. Modified F2P_LOCKIN.py because LOCKIN channel names are some how changed like this;


  3. Running

/opt/rtcds/caltech/c1/scripts/SUS/F2P_LOCKIN.py -o PRM

  should adjust (UL|UR|LR|LL)COIL_GAINs by putting some gain imbalance and shaking the mirror in different frequencies. It uses LOCKIN to OL(PIT|YAW).

  4. Since there was no PRM oplev beam coming out from the vacuum, I quickly looked into BS-PRM chamber. Oplev beam was clipped by MMT1. If I adjust PRM slider values to avoid clipping, the beam will be clipped by mirrors on oplev table. What happened to the PRM oplev?

  5. I also made bunch of /opt/rtcds/userapps/trunk/sus/c1/medm/templates/SUS_SINGLE_LOCKIN(1|2)_DEMOD_(I|Q|SIG).adl because there were missing screens.

 We need to restore the PRM oplev and balance the coils. See, also, elog #7679

ELOG V3.1.3-