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ID Date Author Type Categorydown Subject
  10247   Mon Jul 21 13:58:33 2014 ericqUpdateIOOMC autolocker acting up

The autolocker claimed it was running and blinking, but not doing anything (i.e. lock bit was not updating and no switches or sliders being touched)

After stopping and starting it a number of times, it began working again, through no real changes of my own. I'm a little mystified as to what the problem was... keep an eye out.

  10251   Tue Jul 22 08:36:08 2014 EvanUpdateIOOMC servo TFs


[Rana, Evan]

This morning we took several TFs of the MC servo board using the HP4395A.

The 4395 source was teed, with one output of the tee going to 4395 R and the other output going to the board's IN1. We then took TFs of (4395 A) / (4395 R), where 4395 A was one of the following four points on the servo board:

  • OUT2
  • A TEST1
  • B TEST1

For each of these points, we took a TF at two gain settings: IN1 and VCO gains both at 0 dB, and then IN1 and VCO gains both at 20 dB.

Before doing these measurements, we calibrated out the cable delay. Additionally, SERVO was always loaded with 50 Ω—either from the 4395 or from a terminator.

The attached png shows the servo board settings when these TFs were taken with the 0 dB gain settings. The settings for the 20 dB measurements are identical, except for the higher IN1 and VCO gains.

Using the modified schematic (40m:10250), I've made a plot of the TFs I expect for GIN1 = GVCO = 0 dB, taking into account our 50 Ω loading of the board.

Evidently I'm somehow missing a factor of 2 in the gain of the overall TF, but the shapes of the expected vs. measured magnitudes agree quite well.

At 1 MHz, I expect we should have accumulated about 80 degrees of phase going through the servo board. In reality, we appear to have lost more like 105 degrees.

Attachment 1: MCtfExpectations.pdf
  10303   Thu Jul 31 09:14:14 2014 ericqUpdateIOOMC stability

 Last night, I poked around to try and see if I could reproduce the sketchy MC behavior by exciting MC2 in a way that may be similar to what we do when using it as a CARM actuator. 

The short of it is that at frequencies under 1k, the MC lock didn't mind MC2 position excitations up to 8000 counts. However around 4-5k, a 1000 count excitation would induce a good deal of low frequency (2-5Hz) activity in the MC trans power, causing it to fluctuate by thousands of counts before unlocking. If I turned the excitation off before the unlock, it would eventually settle back down, but not immediately. 

I was able to reproduce this a handful of times before it decided to stop locking altogether, perhaps because of its random mood swings, or perhaps because this kind of disturbance is related to the mood swings...

  10310   Thu Jul 31 19:37:59 2014 KojiUpdateIOOSuccessful modification of the FSS

Quick note:

Migration of the 10Hz pole from the output stage of the FSS to the pomona box was successful.
This also allowed me to insert my offsetting/summing point circuit.

Trial 1:

- Remove C63 (1uF cap) of the FSS

- Short 500 Ohm in the pomona box

This removed 10Hz pole in FSS and 32 Hz zero in the pomona box.
In total we obtain the gain and range of 3.2 for the fast PZT path.

3x10^2 to 3x10^3 times more filtering of the HV amp noise between 10kHz and 100kHz.

The current maximum gains of the FSS is

Overall +19dB (prev. +13dB)
Fast     +30dB (prev +21.5dB)

Trial 2:

- Insert a summing amplifier between the FSS box and the HV amp.

- This amplifier attenuate the input by a factor of 2, and add 5V. i.e. +/-10V input => 0~10V output.

- This just worked fine.

Trial 3:

- Now the fast gain is nominally +30dB.

- In order to provide more room to play with the fast-PC cross over, I moved the pole freq from 2.9Hz to 9.9Hz
  This was done by replacing a 5kOhm in the pomona box by a 1.5kOhm.

Trial 4:

- I just noticed that the output impedance of the FSS (15.8kOhm) and the input impedance of the summing amp (10k Ohm)
  interfere and gives additional 1/2.58 attenuation in addition to the attenuation in the summing amplifier.
  This yields the output range of the HV amp between 45-105V, instead of 0-150V. This is not nice.

- The output impedance of the FSS box (R46 15.8kOhm) was replaced with 100Ohm.

- Now the PMC unlocks very frequently. This might have come from the PMC locking issue or too much gain of the IMC

Trial 5 (final):

- I suspected that the PMC unlock is caused by too much actuation at the high freq. So I decided to revert the  pomona box change

  10314   Thu Jul 31 23:43:00 2014 KojiUpdateIOOModulation frequency adjustment

The main IFO modulation frequency was adjusted to match with the FSR of the IMC.

The new frequency is 11.066128 MHz. This corresponds to the IMC round-trip length of 27.0910 m

This has been done by looking at the peak at 25.845MHz (5* fmod - 29.5MHz) in the MC REFL PD mon.

  10316   Fri Aug 1 01:29:55 2014 KojiUpdateIOOPMC issue

- PMC suddenly refused to lock.

- Investigated what's wrong

- Finally, I touched RF Output Adjust (C1:PSL-PMC_RFADJ). Then it started locking.

- C1:PSL-PMC_RFADJ was set to 2.0 by rana when we looked at the PMC LO issue.
  Now PMC does not lock with this value. I set it to 6.0 so that the lock is robust.

- Right before I lost PMC locking, I had some difficulty in locking IMC. Of course,  the robustness of the PMC is related to the robustness of the IMC.
  We definitely need to investigate this. (RF powers, open loop TF, etc)

  10317   Fri Aug 1 01:57:24 2014 KojiSummaryIOOMC auto locker

To make MC auto locker running correctly, mcdown and mcup were revised

I tried it by unlocking MC several times. It seems OK. Let's see how it works.

Nominal gains for locking (to be taken care by mcdown)

was 16 and is 19 now.

was 9 and is 9 now too.

was missing and now +13

was +23.5 and is now +20.0

Nominal gains for operation ( to be taken care by mcup.

was 19 and is 19 now too.

was 25 and now uses ezcastep (ezcastep C1:IOO-MC_VCO_GAIN=9 +1,16 -s 0.1)


ezcawrite C1:PSL-FSS_MGAIN `ezcaread -n C1:PSL-STAT_FSS_NOM_C_GAIN`
ezcawrite C1:PSL-FSS_FASTGAIN `ezcaread -n C1:PSL-STAT_FSS_NOM_F_GAIN`



  10319   Fri Aug 1 08:55:34 2014 KojiSummaryIOOMC auto locker

It seems that the MC auto locker and the FSSSlow PID servo survived a night.

PC Drive is still angry occasionally. We want to know what this is.

Attachment 1: MC.png
  10320   Fri Aug 1 10:40:48 2014 KojiSummaryIOOMC servo summing amp

The summing amp is prepared to allow up to use bipolar full range of the FSS box output

This means that the FSS fast PZT output is now nominally 0V and can range +/-10V.

- FSS Box has the output range of +/-10V

- Thorlabs HV amp MDT694 accepts 0V ~ +10V

- This circuit add an offset of +5V while the main signal is attenuated by a factor of 2. The offset voltage is produced from the voltage reference IC AD586.

- In addition, a summing node and voltage monitors before and after the summing node are provided. They are useful to test the crossover frequency of the fast/PC loops.

- The output noise level at 10kHz was ~60 nV/rtHz. The transfer function of the circuit was measured and flat up to 100kHz. The phase delay is negligible at 10kHz and less than 3deg at 100kHz

- Although the schematic was drawn in Altium, the board is a universal 1U eurocard and all wires were hand soldered.

Attachment 1: Fast_PZT_IF.PDF
  10321   Fri Aug 1 11:11:12 2014 KojiUpdateIOOCurrent IMC servo configuration

The comparison between the new and old MC servo (FSS part) was attached.

- The new servo has the same DC range as before.
  Even though there is 1/2 gain in the chain now, the previous range of the FSS box was 0 to 10V.
  Now it is +/-10V. So we did not lose the range.

- The new servo has x3.2 larger range above 100Hz.

- x1.6 enhancement of the FSS Box output noise above 10Hz.

- The noise of the HV amp (and the summing amp) is x300 and x2600 more filtered at 10kHz and 100kHz respectively.

Attachment 1: diagram.pdf
  10322   Fri Aug 1 12:49:06 2014 KojiSummaryIOOMC servo analysis

Reasoning to choose the current parameters:

FSS Common: 18dB
FSS Fast: 20dB

Attachment 1:
Openloop transfer function of the IMC loop with the nominal gain setting. The UGF is 176kHz and the phase margin is 48 deg.
This is about 3 time more bandwidth than the previous setting. (Good)

It is visible that the TF has sharp roll off around 1MHz. I wonder if this comes from the demodboard LPF and/or the PMC cav pole.
In fact, according to Manasa, the PMC has the ringdown of 164.6ns which corresponds to the cavity pole of 967kHz. So this must
be there in the OLTF.

From the plot, the order of the low pass is about 5. Subtracting the slope by the cavity pole, the order is four. If I look at the TF of the minicircuits
LPFs (this entry), the phase delay of the filter at 1/10 of the cut off freq is ~30deg. And the order of the filters are maybe 6th elliptic?
So it's not yet clear if the LPF is causing a significant phase delay at 180kHz.

More significantly, the gain margin at ~1MHz is way too small. This is causing a big servo bump at that frequency as seen in Attachment 2.

In total, my recommendation is to move the LPF freq up by x2 or x3, and give a mild LPF above 500kHz.
This requires some modeling as well as try and error.

Attachment 2:

This figure is to explain how the common FSS gain was set. By increasing the gain, the UGF is increased and we can enjoy more supression (from red to purple).
The more gain, however, the more servo bump we observe above the UGF. The gain was chosen so that the total PC feedback does not exceed 3V.

Attachment 3/4:

This figure explains how the fast FSS gain (namely crossover frequency between fast and PC) was set. When the fast is low (red) the phase margin between two loops
are plenty and therefore the openloop TF is smooth. But the PC's frequency domain is large and has to work more (in rms). As the fast gain is increased, the actuation
by the PC is offloaded to the fast PZT (that's good). But eventually the phase margin is not enough and the dip start to show up (purple). This dip cause worse closed loop TF,
as seen in Attachment 4, or even an instability of the loop eventually. So the fast gain was set somewhere in between (green).

Attachment 1: MC_OLTF.pdf
Attachment 2: MC_Error_Common.pdf
Attachment 3: MC_Crossover.pdf
Attachment 4: MC_CLTF_Fast.pdf
  10340   Wed Aug 6 17:29:36 2014 JenneUpdateIOOFSS offset changed

The MC has been unstable and unhappy for the last several hours.  When I looked, I saw that the FSS_FAST monitor has been hovering around 1 V, when it is supposed to be closer to 5ish. 

I changed the C1:PSL-FSS_INOFFSET from -0.08 to -0.8537, and will see if the MC sticks around for longer this time around.

  10341   Wed Aug 6 21:22:09 2014 KojiUpdateIOOFSS offset changed

The fast feedback should be around zero now!

  10343   Thu Aug 7 11:57:59 2014 KojiSummaryIOOMC servo analysis

LISO Fit for the IMC open loop TF. The data and liso source for the fitting were attached in the ZIP file.

I noticed now that the open loop TF I measured has too less phase delay.
I used the closed loop TF to estimate the openloop TF.

Looking at this comparison, I'm afraid that the superboost was not on during the measurement.
I need a new measurement to design MC loop modification to give the AO path for broader bandwidth.

Attachment 1: MC_OLTF_Fit.pdf
Attachment 2: IMC_OLTF.zip
Attachment 3: MC_OLTF_estimated.pdf
  10344   Thu Aug 7 12:25:14 2014 JenneUpdateIOOFSS offset changed


The fast feedback should be around zero now!

 Dang it, I completely forgot.  Well, anyhow, it pulled itself back down to less than 1V, and the MC stayed happy for several hours.  I'm not totally sure what changing the offset did, but the MC seems happy for right now.  I should take a quick look at the error point to make sure that I didn't mess up your tuning.

  10351   Fri Aug 8 12:39:19 2014 ericqSummaryIOOMC servo analysis

I have measured the current boosted MC CLG below 100kHz with an SR785. Swept sine only could get me down to 10kHz, but I was able to get down to 5kHz with a noise-injection measurement. 


I am attaching the SR785 outputs, which are in dB and Degrees. Additionally I pruned the areas of bad coherence out of these, and merged them to provide data files for the CLG and OLG in Real,Imaginary format.

Attachment 1: mcLoopAug8.zip
  10354   Fri Aug 8 15:57:29 2014 ericqSummaryIOOMC servo analysis

 I did some further measurements, to try and see what corresponds to what. In the end I performed four measurements:

  1. Closed loop gain measurement on SR785: Source to MC exc, T'd to channel one. Test 2 to channel two.
  2. Open loop gain measurement on SR785: Source to MCexc, Test 2 to channel one, Test 1 to channel two.
  3. Closed loop gain measurement on AG4395: RF Source to MC exc, T'd to R input. Test 2 to A input.
  4. Open loop gain measurement on AG4395: RF Source to MC exc, Test 2 to R input. Test 1 to A input.

I then converted OLGs to CLG and vice-versa with CLG = 1/(1-OLG)

Here are two plots showing the measured and inferred loop TFs for both closed and open. 


The best agreement seems to be between the directly measured OLGs. Maybe I did something weird with the CLG measurements, or input impedances are distorting things ... 

All data is attached, along with code used to generate the plots. 

Attachment 3: mcLoopAug8.zip
  10356   Fri Aug 8 18:08:12 2014 KojiSummaryIOOMC servo analysis

The closed gain I meant is the AO path: Use IN2 to excite the MC loop and measure IN1 using MON2(?).
In order to obtain the open loop gain from this meausrement, the gain mismatching needs to be compensated, though.

This measurement is to correctly predict the AO path response from the open loop transfer function.

Anyway, the openloop gain seems nicely measured. I'll try to predict AO path response from this.

  10359   Sat Aug 9 14:35:28 2014 KojiSummaryIOOMC servo analysis

Eric's OLTF turned out consistent with the AO path TF that has been measured by me on Jul 31 (entry 10322).

Attachment 1:
Updated empirical fit of the open loop TF by LISO.
In this fit, I gave some of the poles/zeros associated with the boost manually set so that I can use them for the servo design.
LISO itself can make better fitting if all of the variables are moved.

Atatchment 2:
The OLTF data and LISO source for the fitting.

Attachment 3:
Comparison of the AO path TFs. The red one was measured directly on Jul 31. The TF is normalized at the low frequency.
The blue was estimated from the OLTF model given above. They are well consistent now.

Attachment 4:
Now some servo design was tried. In the new design (blue), zeros of the super boost frequency was moved from 20kHz to 30kHz
with the hope of having flatter AO response. The improvement is very little while costing costing above 100kHz. Note that the vertical
axis is intentionally in a linear scale. In fact, the AO response is much improved compared to the one before the MC UGF was increased
(shown in magenta). We have a flatter response both in magnitude and phase.
Therefore I think there is no need to tweak the boost frequency for the AO path.
I'd rather recommend to inspect the high frequency LPFs to earn more gain margin at 1MHz as
explained in entry 10322.

Attachment 5:
This figure shows the comparison of the TFs for the current and new design trial, just in case someone is interested in to see.


Attachment 1: MC_OLTF_Fit.pdf
Attachment 2: liso.zip
Attachment 3: MC_CLTF_Fit.pdf
Attachment 4: MC_CLTF_new.pdf
Attachment 5: MC_OLTF_new.pdf
  10363   Mon Aug 11 21:03:48 2014 ericq, ranaSummaryIOOMC demod measurement

We measured the TF of the MC Demod board today.

We set the Marconi to +3dBm and drove the PD IN port of the demod board, starting at 29.5 MHz. Then we looked at the beat signal amplitude in the output of the demod board. So this is a transfer function but with mag only. Plots from Q below.

Rana took the demod board out and took pictures of it. Inside, the post mixer low pass is a SCLF-5 from mini-circuits. This has a lot of cutoff down low. Since the purpose of this filter is only to cutoff the 2f-1f and the 3f-2f products, we need to have a lot of attenuation at 29.5 MHz. One day, we may want to re-instate that notch for the (3*f1- f_MC) beat frequency, but for now we want stability.

So, I recommend that we (Steve) get 3 each of the SCLF-10 and SCLF-10.7 from Mini-Circuits Tuesday morning. Maybe we can put them into a spare board?

Also, we should probably remove the 140kHz:70kHz lead filter which is in the MC servo board. Its out of date. I think it would be fine for us to get a 7-15 kHz UGF for the CM servo and the MC can basically do that already. Mainly we want to fix the high frequency shape to get more stability.

After the measurements and photos, we had to reset the MCWFS offsets to get the WFS to not break the lock. Seems very sensitive to offsets. Hopefully Andres will give us a new Gouy phase telescope.

  10364   Mon Aug 11 22:07:31 2014 KojiSummaryIOOMC demod measurement

SCLF-5!? It's surprising as the cut off of the OLTF is just above 1Hz. cf this entry

This means that not the demod board but MC or FSS boards seem to have large attenuation above 1MHz.

In this situation, does SCLF-10/10.7 really help us?

  10365   Mon Aug 11 23:32:54 2014 ericqSummaryIOOMC demod measurement

Here's the magnitude plot of the board TF. As mentioned above, this was done with Marconi+Scope, so we were not able to get the phase of this transfer function. 


Oddly enough, the bump that I saw is not included in Minicircuit's data on the SCLF-5.

Attachment 2: demodLP.txt
# F(Hz) RMS(mV)
1035 38.6
2031 38.47
4031 38.47
8032 38.38
16030 38.10
32030 38.10
64030 38.16
128000 38.10
256000 38.22
... 12 more lines ...
  10370   Tue Aug 12 18:20:13 2014 ericqUpdateIOOFSS box TFs

I made some measurements of the FSS box today, to have TFs for a loop model, but also to see what the difference between the different inputs was. 

As a reminder, the FSS box takes the error signal from the MC servo, does some filtering, and sends out two outputs: one to the laser PZT via KojiBox and Thorlabs HV amplifier, and one to be summed with the PMC modulation signal to the PC. Rana found the schematic at D040105

The MC error signal currently enters via a port called "IN1", but there is also a "Test 1 in," which experiences different filtering. I measured the TFs from each of these inputs to both the FAST and PC outputs. There is also an IN2, that is added after the offset point, but was not able to make a good measurement, for reasons unknown. From these TFs, I inferred the difference between the PC and FAST path, as well as the difference between IN1 and Test 1 in.

Specifically, I plugged the cable that is usually connected to the MC servo output, labelled "TO FSS BOX", into the RF out of the AG4395. I then took a BNC cable from the FAST out, or PC out, and fed it into a mini circuits DC block (BLK-89-S+), and then into input A, after checking on a scope that the signal was roughly zeroed and not too huge. Unbeknownst to me at the time, the PC drive output can be pretty big, and could potentially fry the analyzer's input. Fortunately, I think I avoided this fate. 


A ~1.3 MHz bump can be seen here, which would conspire with the bump in the demod board I measured yesterday, to steal even more phase around 1MHz. Maybe we can modify the FSS box to help our gain peaking situation out. 

The data is attached.

RXA: Shazam!

Attachment 3: FSSdata.zip
  10380   Wed Aug 13 23:08:17 2014 ranaUpdateIOOFSS box TFs

As EQ pointed out recently, we're injecting into the FSS error point just after an RF pi filter, but before the VGA. We wondered what the weird filter impedance was doing to our signal if we inject after it. I used LISO to model this FSS common section and attach the plots.

The first plot shows the TF between the Test 1 input and the AD602 VGA input. This is NOT the input that we are actually using.

The second plot shows the TF between the IN1 port (which we are actually using) and the VGA input.

Neither of them shows the 1 MHz bump that we see in the measurements, so I suspect that the board has been modified...the hunt continues. We've got to pop the top of the TTFSS and take photos and measure from IN1 to VGA input.

** FSScomm.fil is now in the LISO SVN. The following command line will run it with two different cases and cat the PDF files into one. If you use an auto-refresh PDF viewer like Okular or Mac Preview, its a nicer display than the usual GNUplot window:

./mfil FSScomm.fil; sleep 1; pdftk FSScomm_run*.pdf cat output FSScomm.pdf

Attachment 1: FSScomm.pdf
FSScomm.pdf FSScomm.pdf
  10391   Thu Aug 14 19:23:25 2014 ranaHowToIOOHow do I set the FSS offset to make the PZT voltage start at the right place?

 When the IMC locks, we want the FAST OUT of the TTFSS box to be close to zero volts. We also want the control signal from the MC Servo board to be close to 0 V. How to set this up?

With the IMC locked, we just servo the FSS input offset to minimize the MC board output :

ezcaservo -r C1:IOO-MC_FAST_MON -g 0.1 -t 10 C1:PSL-FSS_INOFFSET

I would have used "CDSUTILS", but that seems to have some sort of ridiculous bug where we can't have prefixes on channel names, even on the command line. 

  10392   Thu Aug 14 19:33:00 2014 JenneConfigurationIOOMoved MC2 spot

Last night, and again just now, I used the ./MC2_spot_[direction] scripts to center the MC2 spot on the trans QPD.  The MCWFS handled overall alignment to correct for the fact that the ratios in the script aren't perfect.  When I was finished, I ran the MC WFS relief script from the WFS screen.  Last night, and again today, things had drifted until the yaw spot was more than 0.5 counts off.

  10406   Mon Aug 18 09:42:50 2014 KojiSummaryIOOMCREFL PD charcterization

Riju did the measurement of the MCREFL PD.
I found data files in her directory on the control machine.

I was not sure how much was the transimpedance of the DC out.
I assumed the default number from the circuit diagram which was 66.7Ohm.
This may cause the error in absolute caribration of the transimpedance but the shape does not change.

The RF preamp is gain-peeking at 250MHz.

Here is further characterization of the PD response.
As you can see in the second attachment, the 3dB cut off of the resonance is about 2.3MHz.

The game plan file in dropbox was also modified.

Attachment 1: MCREFLPD_transimpedance.pdf
Attachment 2: MCREFLPD_transimpedance_zoom.pdf
  10424   Fri Aug 22 15:11:55 2014 andres, nicolasSummaryIOOMC WFS activity

1. Before doing anything, we centered the IOO QPDs.
2. With the WFS enabled, we offloaded the control signals onto the bias sliders. Then we saved the slider values. The MC LSC diode had a DC value of ~0.5
3. Turned down power with half wave plate before PMC.  Power injected to vacuum ~ 100mW.
4. We did a beam scan of MC REFL, it looks smaller than what Andres predicted based on the MC eigenmode by 10-20%.
5. We made many changes on the table, pictures to be added by Andres.
6. We didn't have the 80% reflector we wanted to increase the WFS power, so it's still a 98%.
6. Beams were aligned on MC REFL PL, camera, beam dumps, WFSs.
7. Clean up
8. PSL power increased to 1.2W, MC locked right away.
9 We didn't change the IOO WFS output matrix, but we changed some signs and gains to make everything stable. MC autolocker brings it back from cold just fine.
10. All time bombs that we've left will be E.Q.'s to clean up. Sorry.\
11. Yay

  10425   Fri Aug 22 15:58:02 2014 SteveSummaryIOOMC WFS activity



Attachment 1: GoyphaseSet.png
  10561   Thu Oct 2 20:54:45 2014 KojiUpdateIOOIMC WFS measurements

[Eric Koji]

We made sensing matrix measurements for the IMC WFS and the MC2 QPD.

The data is under further analysis but here is some record of the current state to show
IMC Trans RIN and the ASC error signals with/without IMC ASC loops

The measureents were done automatically running DTT. This can be done by


The analysis is in preparation so that it provides us a diagnostic report in a PDF file.

Attachment 1: IMC_RIN_141002.pdf
Attachment 2: IMC_WFS_141002.pdf
  10564   Fri Oct 3 13:03:05 2014 ericqUpdateIOOIMC WFS measurements

Yesterday, Koji and I measured the transfer function of pitch and yaw excitations of each MC mirror, directly to each quadrant of each WFS QPD. 

When I last touched the WFS settings, I only used MC2 excitations to set the individual quadrant demodulation phases, but Koji pointed out that this could be incomplete, since motion of the curved MC2 mirror is qualitatively different than motion of the flat 1&3. 

We set up a DTT file with twenty TFs (the excitation to I & Q of each WFS quadrant, and the MC2 trans quadrants), and then used some perl find and replace magic to create an xml file for each excitation. These are the files called by the measurement script Koji wrote. 

I then wrote a MATLAB script that uses the magical new dttData function Koji and Nic have created, to extract the TF data at the excitation frequency, and build up the sensing elements. I broke the measurements down by detector and excitation coordinate (pitch or yaw).

The amplitudes of the sensing elements in the following plots are normalized to the single largest response of any of the QPD's quadrants to an excitation in the given coordinate, the angles are unchanged. From this, we should be able to read off the proper digital demodulation angles for each segment, confirm the signs of their combinations for pitch and yaw, and construct the sensing matrix elements of the properly rotated signals. 



The axes of each quadrant look consistent across mirrors, which is good, as it nails down the proper demod angle. 

The xml files and matlab script used to generate these plots is attached. (It requires the dttData functions however, which are in the svn (and the dttData functions require a MATLAB newer than 2012b))

Attachment 5: analyzeWfs.zip
  10565   Sun Oct 5 10:09:49 2014 ranaUpdateIOOIMC WFS measurements

It seems clever, but I wonder why use DTT and command line perl, instead of using the FE lockins or just demod the offline data or all of the other sensing matrix scripts made for the LSC (at 40m) or ASC (at LLO) ?

  10566   Sun Oct 5 23:43:08 2014 KojiUpdateIOOIMC WFS measurements

There are several non scientific reasons.

  10646   Tue Oct 28 14:07:28 2014 KojiUpdateIOOIMC WFS sensing matrix measurement

Last night the sensing matrix for IMC WFS&QPD were measured.

C1:IOO-MC(1, 2, 3)_(ASCPIT, ASCYAW)_EXC were excited at 5.01Hz with 100 count
The output of the WFS1/WFS2/QPD were measured. They all looked well responding
i.e. Pitch motion shows pitch error signals, Yaw motion shows yaw error signals.

The below is the transfer function from each suspension to the error signals

MC1P      MC2P     MC3P
-3.16e-4  1.14e-2  4.62e-3 -> WFS1P
 5.43e-3  8.22e-3 -2.79e-3 -> WFS2P
-4.03e-5 -3.98e-5 -3.94e-5 -> QPDP

MC1Y      MC2Y     MC3Y
-6.17e-4  6.03e-4  1.45e-4 -> WFS1Y
-2.43e-4  4.57e-3 -2.16e-3 -> WFS2Y
 7.08e-7  2.40e-6  1.32e-6 -> QPDY

Taking the inverse of these matrices, the scale was adjusted so that the dc response.

Attachment 1: 00.png
  10647   Tue Oct 28 15:27:25 2014 ericqUpdateIOOIMC WFS sensing matrix measurement

 I took some spectra of the error signals and MC2 Trans RIN with the loops off (blue) and on (red) during the current conditions of daytime seismic noise.



  10648   Tue Oct 28 20:47:08 2014 diegoUpdateIOOIMC WFS sensing matrix measurement

Today I started looking into the WFS problem and improvement, after being briefed by Koji and Nicholas. I started taking some measurements of open loop transfer functions for both PIT and YAW for WFS1, WFS2 and MC2_TRANS. For both WFS1 and 2 there is a peak in close proximity of the region with gain>1, and the phase margin is not very high. Tomorrow I will make measurements of the local damping open loop transfer functions, then we'll think how to improve the sensors' behaviour.

Attachment 1: 141028_MCWFS_WFS1_PIT_OL.pdf
Attachment 2: 141028_MCWFS_WFS1_YAW_OL.pdf
Attachment 3: 141028_MCWFS_WFS2_PIT_OL.pdf
Attachment 4: 141028_MCWFS_WFS2_YAW_OL.pdf
Attachment 5: 141028_MCWFS_MC2_TRANS_PIT_OL.pdf
Attachment 6: 141028_MCWFS_MC2_TRANS_YAW_OL.pdf
  10653   Thu Oct 30 02:12:59 2014 diegoUpdateIOOIMC WFS sensing matrix measurement


Today we took some measurements of transfer functions and power spectra of suspensions of the MC* mirrors (open loop), for all the DOFs (PIT, POS, SIDE, YAW); the purpose is to evaluate the Q factor of the resonances and then improve the local damping system.

Attachment 1: MC1_OL_PIT.pdf
Attachment 2: MC1_OL_POS.pdf
Attachment 3: MC1_OL_SIDE.pdf
Attachment 4: MC1_OL_YAW.pdf
Attachment 5: MC2_OL_PIT.pdf
Attachment 6: MC2_OL_POS.pdf
Attachment 7: MC2_OL_SIDE.pdf
Attachment 8: MC2_OL_YAW.pdf
Attachment 9: MC3_OL_PIT.pdf
Attachment 10: MC3_OL_POS.pdf
Attachment 11: MC3_OL_SIDE.pdf
Attachment 12: MC3_OL_YAW.pdf
  10681   Thu Nov 6 12:58:28 2014 KojiUpdateIOOWFS offset was reset

IMC WFS operating point seemed to get degraded.

- IMC WFS feedback was relieved.

- WFS servo was turned off.

- IMC alignment was tuned carefully

- /opt/rtcds/caltech/c1/scripts/MC/WFS/WFS_FilterBank_offsets was run

- WFS servo was turned on again 

  10704   Wed Nov 12 20:11:41 2014 KojiUpdateIOOMC WFS gain reduced again

MC WFS was oscillative at 1Hz. I've reduced the servo gain further (x1, x1, x10, x1, x1, and x10).

The MC mirrors were realigned, and the WFS offsets were reset.

  10706   Wed Nov 12 22:22:11 2014 KojiSummaryIOOEstimation of the angular jitter imposed by the TTs

[Koji, Rana, Jenne]

One coil of the TT produce 36nrad/rtHz at DC.

- C1:IOO-TT2_UL_EXC was excited with 5 count_pk at 0.04Hz.

- LSC_TRY exhibited the symmetric reduction of the transmission from 0.95 to 0.90.

1 - (theta/theta0)^2 /2 = 0.90 / 0.95

=> theta / theta0 = 0.32

- 40m beam waist radius is 3.1mm. This means the divergence angle is 1.1e-4 rad.

=> 1.1e-4*0.32 = 3.6e-5 rad

=> 3.6e-5/5 = 7.2 urad/count (per coil)

- DAC noise 1/sqrt(12 fs), where fs is the sampling rate (fs = 16384)

=> 0.002 cnt/rtHz

- One coil causes 7.2u*0.002 = 14 nrad/rtHz (at DC)

- One suspension cause 29 nrad/rtHz (at DC)

Attachment 1: 03.png
  10722   Mon Nov 17 20:28:17 2014 ranaSummaryIOOMC servo summing amp

I modified the /cvs/cds/caltech/target/c1psl/psl.db file to adjust the records for the FSS-FAST signal (to make it go yellow / red at the correct voltages). This was needed to match 5V offset which Koji added to the output of the FSS board back in August.

I also manually adjusted the alarm levels with caput so that we don't have to reboot c1psl. Beware of potential tiimebomb / boot issues if I made a typo! psl.db update in the SVN (also, there were ~12 uncomitted changes in that directory....please be responsible and commit ALL changes you make in the scripts directory, even if its just a little thing and you are too cool for SVN)

  10723   Mon Nov 17 20:40:29 2014 rana, diegoUpdateIOOInvestigating the IMC WFS situation

We've known for years that the IMC WFS sensing chain is pointlessly bad, but until recently, we haven't thought it was worth it to fix.

There are problems in all parts of the chain:

  1. The WFS Photodetectors oscillate ~200 MHz when turned up to full gain. Diego and I confirmed this today by measuring the RF spectrum of the signals going into the WFS demod boards and seeing the oscillation change (not much) with RF gain. I recommend we switch the heads into the full gain mode (turn all of the attenuators OFF). At the moment we are operating with the 2dB and 8dB attenuators ON.
  2. The demod board has some bad gain allocation and noisy opamps.
  3. The whitening board has too much up/down of gain with noise injection along the way. And the range cannot fill up the ADC.
  10728   Thu Nov 20 22:43:15 2014 KojiUpdateIOOIMC WFS damping gain adjustment

From the measured OLTF, the dynamics of the damped suspension was inferred by calculating H_damped = H_pend / (1+OLTF).
Here H_pend is a pendulum transfer function. For simplicity, the DC gain of the unity is used. The resonant frequency of the mode
is estimated from the OLTF measurement. Because of inprecise resonant frequency for each mode, calculated damped pendulum
has glitches at the resonant frequency. In fact measurement of the OLTF at the resonant freq was not precise (of course). We can
just ignore this glitchiness (numerically I don't know how to do it particularly when the residual Q is high).

Here is my recommended values to have the residual Q of 3~5 for each mode.

MC1 SUS POS current  75   -> x3   = 225
MC1 SUS PIT current   7.5 -> x2   =  22.5
MC1 SUS YAW current  11   -> x2   =  22
MC1 SUS SD  current 300   -> x2   = 600

MC2 SUS POS current  75   -> x3   = 225
MC2 SUS PIT current  20   -> x0.5 =  10
MC2 SUS YAW current   8   -> x1.5 =  12
MC2 SUS SD  current 300   -> x2   = 600

MC3 SUS POS current  95   -> x3   = 300
MC3 SUS PIT current   9   -> x1.5 =  13.5
MC3 SUS YAW current   6   -> x1.5 =   9
MC3 SUS SD  current 250   -> x3   = 750

This is the current setting in the end.

MC1 SUS SD  450

MC2 SUS SD  450

MC3 SUS SD  500

Attachment 1: MC_OLTF_CLTF.pdf
  10826   Sun Dec 21 18:46:06 2014 diegoUpdateIOOMC Error Spectra

The error spectra I took so far are not that informative, I'm afraid. The first three posted here refer to Wed 17 in the afternoon, where things were quiet, the LSC control was off and the MC was reliably locked. The last two plots refer to Wed night, while Q and I were doing some locking work; in particular, these were taken just after one of the locklosses described in elog 10814. Sadly, they aren't much different from the "quiet" ones.

I can add some considerations though: Q and I saw some weird effects during that night, using a live reading of such spectra, which couldn't be saved though; such effects were quite fast both in appearance and disapperance, therefore difficult to save using the snapshot measurement, which is the only one that can save the data as of now; moreover, these effects were certainly seen during the locklosses, but sometimes also in normal circumstances. What we saw was a broad peak in the range 5e4-1e5 Hz with peak value ~1e-5 V/rtHz, just after the main peak shown in the attached spectra.

Attachment 1: SPAG4395_17-12-2014_170951.pdf
Attachment 2: SPAG4395_17-12-2014_172846.pdf
Attachment 3: SPAG4395_17-12-2014_175147.pdf
Attachment 4: SPAG4395_18-12-2014_003414.pdf
Attachment 5: SPAG4395_18-12-2014_003506.pdf
  10828   Mon Dec 22 15:11:08 2014 ranaUpdateIOOMC Error Spectra

che tristezza  

What we want is to have the high and low noise spectra on the same plot. The high noise one should be triggered by a high PC DRIVE signal.

  10829   Mon Dec 22 15:46:58 2014 KurosawaSummaryIOOSeven transfer functions

IMC OL TF has been measured from 10K to 10M

Attachment 1: MC_OLTF.pdf
  10832   Mon Dec 22 21:53:08 2014 rana, kojiUpdateIOOSeven transfer functions

Today we were looking at the MC TFs and pulled out the FSS box to measure it. We took photos and removed a capacitor with only one leg.

Still, we were unable to see the weird, flat TF from 0.1-1 MHz and the bump around 1 MHz. Its not in the FSS box or the IMC servo card. So we looked around for a rogue Pomona box and found one sneakily located between the IMC and FSS box, underneath some cables next to the Thorlabs HV driver for the NPRO.

It was meant to be a 14k:140k lead filter (with a high frequency gain of unity) to give us more phase margin (see elog 4366; its been there for 3.5 years).

From the comparison below, you can see what the effect of the filter was. Neither the red nor purple TFs are what we want, but at least we've tracked down where the bump comes from. Now we have to figure out why and what to do about it.

* all of the stuff above ~1-2 MHz seems to be some kind of pickup stuff.

** notice how the elog is able to make thumbnails of PDFs now that its not Solaris!

Attachment 1: MC_OLG.pdf
  10833   Tue Dec 23 01:55:35 2014 rana, kojiUpdateIOOSeven transfer functions

Some TFs of the TTFSS box

Attachment 1: MC_FSS_TF.pdf
  10841   Tue Dec 23 20:50:39 2014 rana, kojiUpdateIOOSeven transfer functions

Today we decided to continue to modify the TTFSS board.

The modified schematic can be found here: https://dcc.ligo.org/D1400426-v1 as part of the 40m electronics DCC Tree.

What we did

1) Modify input elliptic filter (L1, C3, C4, C5) to give zero and pole at 30 kHz and 300 kHz, respectively. L1 was replaced with a 1 kOhm resistor.  C3 was replaced with 5600 pF. C4 and C5 were removed. So the expected locations of the zero and pole were at 28.4 kHz and 256 kHz, respectively. This lead filter replaces the Pomona box, and does so without causing the terrible resonance around 1 MHz.

2) Removed the notch filters for the PC and fast path. This was done by removing L2, L3, and C52.

At this point we tested the MC locking and measured the transfer function. We successfully turned up the UGF to 170kHz and two super-boosts on.

3) Now a peak at 1.7MHz was visible and probably causing noise. We decided to revert L2 and adjusted C50 to tune the notch filter in the PC path to suppress this possible PC resonance. Again the TF was measured. We confirmed that the peak at 1.7MHz is at -7dB and not causing an oscillation. The suppression of the peak is limited by the Q of the notch. Since its in a weird feedback loop, we're not sure how to make it deeper at the moment.

4) The connection from the MC board output now goes in through the switchable Test1 input, rather than the fixed 'IN1'. The high frequency gain of this input is now ~4x higher than it was. I'm not sure that the AD829 in the MC board can drive such a small load (125 Ohms + the ~20 Ohms ON resistance of the MAX333A) very well, so perhaps we ought to up the output resistor to ~100-200 Ohms?

Also, we modified the MC Servo board: mainly changed the corner frequencies of the Super Boost stages and some random cleanup and photo taking. I lost the connecting cable from the CM to the AO input (unlabeled).

  1.  The first two Super Boost stages were changed from 20k:1k to 10k:500 to give us back some phase margin and keep the same low freq gain. I don't really know what the gain requirement is for this servo here at the 40m. The poles and zeros were chosen for iLIGO so as to have the frequency noise be 10x less than the SRD at 7 kHz.
  2. The third Super Boost (which we never used) was changed from 10k:500 to ~3k:150 (?) just in case we want a little more low freq gain.
  3. There was some purple vestigial wiring on the back side of the board with a flying resistor; I think this was a way to put a DC offset in to the output of the board, but its not needed anymore so I removed it.


Attachment 1: MC_OLTF.pdf
Attachment 2: MC_OLTF2.pdf
Attachment 3: matlab.zip
  10842   Wed Dec 24 08:25:05 2014 ranaConfigurationIOOnotes on MC locking

 I've updated the scripts for the MC auto locking. Due to some permissions issues or general SVN messiness, most of the scripts in there were not saved anywhere and so I've overwritten what we had before. 

After all of the electronics changes from Monday/Tuesday, the lock acquisition had to be changed a lot. The MC seems to catch on the HOM more often. So I lowered a bunch of the gains so that its less likely to hold the HOM locks.

A very nice feature of the Autolocker running on megatron is that the whole 'mcup' sequence now runs very fast and as soon as it catches the TEM00, it gets to the final state in less than 2 seconds.

I've also increased the amplitude of the MC2 tickle from 100 to 300 counts to move it through more fringes and to break the HOM locks more often. Using the 2009 MC2 Calibration of 6 nm/count, this is 1.8 microns-peak @ 0.03 Hz, which seems like a reasonable excitation.

Using this the MC has relocked several times, so its a good start. We'll have to work on tuning the settings to make things a little spicier as we move ahead.


That directory is still in a conflicted state and I leave it to Eric/Diego to figure out what's going on in there. Seems like more fallout from the nodus upgrade:

controls@chiara|MC > svn up

svn: REPORT of '/svn/!svn/vcc/default': Could not read chunk size: Secure connection truncated (https://nodus.ligo.caltech.edu:30889)

ELOG V3.1.3-