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ID Date Authorup Type Category Subject
  6187   Thu Jan 12 03:05:02 2012 kiwamuUpdateLSCOSA installed in AS

[John / Valera / Kiwamu]

 We installed a new weapon, an optical spectrum analyzer in the AS port.

Like we used to do in the old days, two BNC cables were newly laid down and they bring the output of the OSA to the control room to monitor the spectrum with an oscilloscope.

 

(Some notes)

The photo diode of the OSA was replaced by a Thorlab PDA100A to amplify the signals.

The carrier peak is at about 6.9 V and the f1 and f2 sidebands peaks are at about 40 mV when the beam is in straight shot (everything is misaligned except ITMY and BS).

According to a rough calculation, those numbers correspond to a modulation depth of about 0.16 or so.

The depth agree with what Mirko measured before (#5519)

 

  6202   Tue Jan 17 01:02:07 2012 kiwamuUpdateLSCglitch hunting in REFL RFPDs : strange

A very strange thing is going on.

The REFL11 and REFL55 demod signals show high frequency noise depending on how big signals go to the POS actuator of PRM.

This noise shows up even when the beam is single-bounced back from PRM ( the rest of the suspensions are misaligned) and it's very repeatable.

Any idea ?? Am I crazy ?? Is PRM making some fringes with some other optics ??

 

 

(background)

 The most annoying thing in the central part locking is glitches showing up in the LSC error signals (#6183).
The symptom is that when the motion in PRCL at 3 Hz becomes louder, somehow we get glitches in both the MICH and PRCL error signals.
In the frequency domain, those glitches are mostly contribute to a frequency band of about 30 - 100 Hz.
Last Thursday Koji and I locked the half PRM (PRMI with either ITMX or ITMY misaligned) to see if we still have the glitches in this simpler configuration.
Indeed there were the same kind of glitches --a loud 3 Hz motion triggers the glitches.
It was shown particularly in the REFL11 signal but not so much in the REFL33 while AS55 didn't show any glitches.
 
 
(Still glitches even in the single bounce beam)
   We were suspecting some kind of coupling from a beam jitter, so that the 3 Hz motion somehow brings the beam spot to a bad place somewhere in the REFL paths.
I misaligned all the suspensions except for PRM such that the beam directly bounces back from PRM and go to the REFL port.
Indeed there still were glitches in the REFL11 and REFL55 demod signals. It showed up once per 30 sec or so and pushes up the noise floor around 30 - 100 Hz.
There might be a little bit of glitches also in the REFL33, but the ADC noise floor and the expected glitch noise level were comparable and hence it was difficult to see the glitches in REFL33.
 

(Glitch is related to the PRM POS actuation)

 In the single-bounce configuration I started shaking the PIT and YAW motions of PRM at 3 Hz using the realtime LOCKIN oscillator to see if I can reproduce the glitches.
However no significant glitches were found in this test.
Then I started shaking the POS instead of the angular DOFs, and found that it causes the glitches.
At this point it didn't look like a glitch any more, it became more like a stationary noise.
 
 The attached screen shot is the noise spectrum of the REFL11_I.
The red curve is the one taken when I injected the 3 Hz excitation in POS by the LOCKIN oscillator.
The excitation is at 3 Hz with an amplitude of 1000 counts.
As a comparison I plotted the same spectrum when no excitation was injected and it is plotted in pink.
 

 PRMsingle_bounce.png

It seems there is a cut off frequency at 100 Hz.
This frequency depends on the amplitude of the excitation -- increasing the amplitude brings the cut off frequency higher.
This noise spectrum didn't change with and without the oplevs and local damping.
 

(Possible scenario)

A possible reason that I can think of right now is : PRM is interfering with some other optics for some reason.
But if it's true, why I didn't see any fringes in the AS demod signals in the half PRM configuration ?
 

Quote from #6183

 We tried to figure out what is causing spikes in the REFL33 signal, which is used to lock PRCL.

No useful information was obtained tonight and it is still under investigation.

  6203   Tue Jan 17 02:27:49 2012 kiwamuUpdateLSCfringe tests : all the suspensions are innocent

I did a quick test to check a hypothesis that PRM is interfering with some other optics in the single bounce configuration.

I shook all the suspensions (except the MC mirrors) at 3 Hz in POS, PIT and YAW with an amplitude of 1000 counts.

No effects were found in the REFL demod signals.

So it is NOT a fringe effect caused by the other suspended mirrors.

Quote from #6202

The REFL11 and REFL55 demod signals show high frequency noise depending on how big signals go to the POS actuator of PRM.

Is PRM making some fringes with some other optics ??   

 

  6204   Tue Jan 17 02:44:59 2012 kiwamuUpdateCDSawg not working

AWG is not working. This needs to be fixed.

I could set the channel and the parameters in the AWGGUI screen, but it never inject signals to the realtime system.

  6205   Tue Jan 17 03:10:27 2012 kiwamuConfigurationIOOrotated lambda/2 plate

I have slightly rotated the lambda/2 plate, which is used for attenuating the REFL beam's power on the AS table

because the plate had been at an unusual angle for investigation of the glitches since last Thursday.

It means the laser power going to the coating thermal noise setup has also changed. Just keep it in mind.

Quote from #6198

So today we set up the Jenny RC temperature setup to lock the LWE NPRO to the RC and then set up the beat note with the IFO REFL beam on the AS table. By using the 2 laser beat, we are avoiding the VCO phase noise issue which used to limit the PSL frequency noise at ~0.01 Hz/rHz. To do this we have reworked some of the optics on the PSL and AS tables, but I think its been done without disturbing the beams for the regular locking. Beat note has been found, but the NPRO has still not been locked to the RC - next we setup the lockin amp, dither the PZT, and then use the New Focus lock box to lock it to the RC.

  6206   Tue Jan 17 13:47:40 2012 kiwamuUpdateLSCdirty steering mirror in the REFL path

 Last night I found that there were many dust particles on the second steering mirror in the REFL path on the AS table.

Looking at it through an IR viewer, I saw the REFL beam hitting one of the biggest dust particles on that mirror.

This dust particle maybe causing the glitches or maybe not.

Anyway because it's always better to have clean mirrors, I will wipe the steering mirror in this evening and check the presence of the glitches again.

Quote from #6202

The REFL11 and REFL55 demod signals show high frequency noise depending on how big signals go to the POS actuator of PRM.

Is PRM making some fringes with some other optics ??
 

  6207   Tue Jan 17 16:09:20 2012 kiwamuUpdateCDSawg not working on the c1sus machine

Actually awg works fine without any problems when the excitation channels belong to the c1lsc machine.

It seems that the awg doesn't inject signals on the channels of the c1sus machine, for example C1:SUS-BS_LSC_EXC and so on.

Quote from #6204

AWG is not working. This needs to be fixed.

  6209   Wed Jan 18 12:36:26 2012 kiwamuUpdateLSCwiped a steering mirror on the REFL path

I wiped both surfaces of the REFL second steering mirror.

However no improvements. The glitches still remain.

 

(Pic.1 before wiping, Pic.2 after wiping)

DSC_3861_small.jpgDSC_3863_small.jpg

Quote from #6206

 Last night I found that there were many dust particles on the second steering mirror in the REFL path on the AS table.

  6211   Wed Jan 18 14:28:36 2012 kiwamuUpdateLSCestimation of optical length between PRM and scattering object

Assuming that PRM is interfering with some other optics, I have estimated the optical distance between PRM and an object that interferes with PRM.

The optical distance is estimated to be 9.5 +/- 0.5 m.

If we believe this number the object is most likely outside of the vacuum chambers.

 

 (The measurement)

  In order to estimate the optical length between PRM and a scattering body, I swept the frequency of the main laser by actuating on the MC length.
With the sweep, the laser frequency go across some fringes and basically it allows us to estimate the FSR of a very low finesse cavity formed by PRM and the scattering body.
Therefore we get the the optical distance based on the resultant FSR.
 
  The measurement goes as follows:
  1.  Preparation : calibration of the MC2 actuator as a frequency actuator (for more details, see the next section)
  2.  Set the interferometer to the single-bounce configuration such that the beam directly is reflected back from PRM
  3.  Take spectra of REFL11_I without driving any optics. This spectra tells us how quiet the noise normally is.
  4.  Drive MC2_POS at 10 Hz with an amplitude of 10000 counts so that we can see the high frequency up conversion noise
    • The frequency was chosen such that the excitation is out of the local damping bands
    • The amplitude was chosen to be as big as possible until the MC unlocked
    • With this drive, the laser frequency should change by 20 MHz peak-peak at 10 Hz.
  5.  Record the noisy spectrum when the MC2_POS was driven.
  6.  Drive PRM instead of MC2 at 10 Hz.
    • Adjust the amplitude of the excitation such that the cut-off frequency of the up conversion noise matches with that of the MC2 driven case.
    • The amplitude was found to be 1700 - 2000 counts, this uncertainty is currently limiting the precision of the optical distance estimation.
    • With this amount of the drive, PRM moves by 0.8 um peak-peak at 10Hz.
  7. Estimate the optical length based on the amount of the drives for PRM and MC2.
    • Estimate the FSR using the following relation df/FSR = dx/ (lambda/2). => FSR = 17 MHz
    • Since FSR = c/ (2L),  L = c/(2 FSR) = 9.5 m or so
scattering.png

 

 

(Calibration of the MC2 actuator)

 To do the measurement described above, the MC2 actuator must be calibrated in terms of a frequency actuator.
I did the same old technique (#4721): lock a cavity, adjust the UGF as low as possible, and shake an actuator of interest.
This time I used the half-PRM (PRM + ITMY) for this measurement.
The actuator responses are calibrated from that of displacement to frequency by using df/f = dx/L and assumed that L = 6.760 (#4585).
Also the PRM actuator was measured such that we can use this as a reference since we already know the response in displacement (#5637).
 The attached plot below is the actual responses that I measured yesterday. The y-axis is calibrated to Hz/counts.
 

 

calibration.png

 

Quote from #6202

Is PRM making some fringes with some other optics ??

  6212   Wed Jan 18 16:31:10 2012 kiwamuUpdateLSCestimation of optical length between PRM and scattering object

I searched for a scattering body in the REFL path.

According to the result the REFL path on the AS table is innocent.

 

The idea of the search method is given as follows:

  •   Put a 1/10 ND attenuator at the origin of the REFL path on the AS table.
  •   Of course this reduces the signal level by the same factor of 10 in the REFL11_I demod signal.
  •   If the scattering body is in the REFL path the up conversion noise will be smaller by a factor of 100 because the scattered light go across the attenuator twice.

 

 The attached plot below is the spectra of REFL11 with the 1/10 attenuator at the origin of the REFL path when the beam is single-bounced from PRM.
In the measurement PRM_POS was driven at 10 Hz with an amplitude of 1700 all the time. This is exactly the same situation as that explained in the previous elog entry (#6211).
You can see that the up conversion noise level also decreased by the same factor of 10, which suggests there are no scattering object in the REFL path.
Note that the data with the attenuator in place is intentionally scaled by multiplying a factor of 10 for comparison.
ND1atten.png
 

Quote from #6211

Assuming that PRM is interfering with some other optics, I have estimated the optical distance between PRM and an object that interferes with PRM.

The optical distance is estimated to be 9.5 +/- 0.5 m.

If we believe this number the object is most likely outside of the vacuum chambers.

 

  6213   Thu Jan 19 23:34:52 2012 kiwamuUpdateIOOPMC realignment and HEPA

I realigned the incident beam to PMC at 23:30. The transmitted light went up from 0.78 to 0.83.

Also I decreased the HEPA level down to 20 % for the night time locking.

  6214   Fri Jan 20 15:59:02 2012 kiwamuUpdateGreen LockingY arm ALS noige budget

One of my goals in this week is : measurement of the current best ALS noise budget.

Last night I took a new noise spectra of the Y arm ALS, which is shown in the attached figure below.

The displacement of the arm cavity observed from the IR PDH is at 66 pm in rms. In the measurement the arm length was stabilized with the ALS technique.

 

Yarm_ALS_2012Jan19.png

 

  6215   Fri Jan 20 16:24:50 2012 kiwamuUpdateGreen LockingY arm ALS : time series

Here is a new time series plot showing how stably ALS can control the arm length.

In the middle of the plot the cavity length was held at the resonance point for ~ 2 min. and then it passed through the resonance point to show the full shape of the PDH signal.

Apparently the PDH signal is now quieter than before (#6133)

time_series.png

Quote from #6214

One of my goals in this week is : measurement of the current best ALS noise budget.

 

  6218   Mon Jan 23 23:12:00 2012 kiwamuUpdateIOOPMC realignment

I have realigned the beam pointing to PMC. The transmitted light increased from 0.74 to 0.83.

The misalignment was mainly in pitch.

  6220   Tue Jan 24 18:11:13 2012 kiwamuUpdateGreen LockingY arm ALS noise budget

I did some more stuff for the Y arm ALS and updated the noise budget:

After the works, the rms displacement improved a little bit, so it is now at 24 pm in rms.

Though, it turned out that the MFD's ADC is now limiting the noise in a frequency band of 200 mHz - 5 Hz.

So tonight I will increase the gain of the whitening filter to push down the ADC noise more.

 

Yarm_ALS_2012Jan19.png

 

(What I did)

 + added the DAC noise and comparator noise based on measurements.

 + redesigned the servo filter shape to suppress the seismic noise below 10 Hz.

 The attached plot below shows the newly designed open loop transfer function together with the old one for a comparison.

UGF is at 120 Hz and the phase margin is about 27 deg.

  newservo.png

  • FM7 = resonant gain (17)
  • FM6 = resonant gain (3)
  • FM5 = zero(1) * pole(500)
  • FM4 = pole(1) * zero(40.) * 40.
  • FM3 = pole(1) * zero(40.) * 40.
  • FM2 = pole(0.001)*zero(1)*1000.
  6221   Wed Jan 25 02:59:46 2012 kiwamuUpdateGreen LockingY arm ALS noise budget

Surprisingly increasing the gain of the whitening filter didn't improve the noise curve.

It suggests that the ADC noise is not the limiting factor below 10 Hz.

Quote from #6220

Though, it turned out that the MFD's ADC is now limiting the noise in a frequency band of 200 mHz - 5 Hz.

So tonight I will increase the gain of the whitening filter to push down the ADC noise more.

 

  6224   Thu Jan 26 05:40:10 2012 kiwamuUpdateLSCglitch in the analog demodulated signals

Indeed the glitches show up in the analog demodulated signals. So it is not an issue of the digital processing.

With an oscilloscope I looked at the I/Q monitor outputs of the LSC demodulators, including REFL11, REFL33, REFL55, POY11, AS55 while keep locking the carrier-resonant PRMI.

I saw some glitches in REFL11, REFL55 and AS55. But I didn't see any obvious glitches in REFL33 and PO11 because the SNR of those signals weren't good enough.

 


(some example glitches)

The attached plot below is an example shot of the actual signals when the carrier resonant PRMI was locked.

The first upper row is the spectrogram of REFL11_I, REFL55_I, REFL33_I and AS55_Q in linear-linear scale.

The second row shows the actual time series of those data in unit of counts.

The bottom row is for some DC signals, including REFLDC, ASDC and POYDC.

 

glitch.png

You can see that there are so many glitches in the actual time series of the demod signals (actually I picked up the worst time chunk).

It seems that  most of the glitches in REFL11, REFL33 and AS55  coincide.

The typical time scale of the glitches was about 20 msec or so.

Note that the PRMI was locked by REFL33 and AS55 as usual.

  6225   Thu Jan 26 06:09:52 2012 kiwamuUpdateGreen Lockingnoisy AS55

During the Y arm ALS I found that the noise of the AS55 demod signal was worse than that of POY11 in terms of the Y arm displacement.

There is a bump from 500 mHz to 100 Hz in the AS55 signal while POY11 didn't show such a structure in the spectrum.

 

The plot below is the noise spectra of the Y arm ALS. The arm length was stabilized by using the green beat-note fedback to ETMY.

In this measurement, POY11 and AS55 were served as out-of-loop sensors, and they were supposed to show the same noise spectra.

In the plot It is obvious that the AS55 curve is louder than the POY curve.

Yarm_ALS_2012Jan25.png

  6229   Thu Jan 26 19:28:02 2012 kiwamuUpdateIOOPMC low transmission

After I recovered the lock of PMC, I found that the PMC transmission was quite low. It was about 0.26 in the EPICS display.

I zeroed the PSL temperature feedback value which had been -2.3 and then the PMC transmission went back to a normal value of 0.83.

I believe it was because the PSL was running with two different oscillation modes due to the big temperature offset.

  6230   Fri Jan 27 05:21:43 2012 kiwamuUpdateGreen Lockingfine alignment of the Y end green setup

I did a fine alignment on the Y end green setup. The green light became able to be locked again.

Quote from #6227

 The alignment is finished after the realization that the 3rd steering mirror had to be adjusted too.

  6231   Fri Jan 27 06:07:47 2012 kiwamuUpdateLSCglitch hunting

I went through various IFO configurations to see if there are glitches or not.

Here is a summary table of the glitch investigation tonight. Some of the cells in the table are still not yet checked and they are just left blank.

IFO configuration  Yarm
Xarm
MICH
Half PRMI
low finesse PRMI
PRMI (carrier)
PRMI (sideband)
DRMI
AS55 NO NO NO   up conversion noise glitch glitch glitch
REFL11 NO NO NO   up conversion noise
glitch glitch glitch
REFL33 NO NO NO   - glitch glitch glitch
REFL55 NO NO NO   up conversion noise
glitch glitch glitch
REFL165 NO NO NO   - glitch glitch glitch
POX11 - NO NO     glitch glitch glitch
POY11 NO - NO     glitch glitch glitch
POP55 - -            
                 

 

        Low finesse PRMI      

The low finesse PRMI configuration is a power-recycled MIchelson with an intentional offset in MICH to let some of the cavity power go through MICH to the dark port.

To lock this configuration I used ASDC plus an offset for MICH and REFL33 for PRCL.

The MICH offset was chosen so that the ASDC power becomes the half of the maximum.

In this configuration NO glitches ( a high speed signal with an amplitude of more than 4 or 5 sigma) were found when it was locked.

Is it because I didn't use AS55 ?? or because the finesse is low ??

Also, as we have already known, the up conversion noise (#6212) showed up -- the level of the high frequency noise are sensitive to the 3 Hz motion.

  6235   Fri Jan 27 17:16:05 2012 kiwamuUpdateLSChypothetical glitch scenario

Here is a hypothetical scenario which could make the glitches in the LSC error signals. It can be considered as a 4 step phenomenon.

        (1) up conversion noise due to a large motion at 3 Hz

   => (2) rms level exceeds the line width (a.k.a. linear range) in some LSC sensors

   => (3) unlocks some of the DOFs  in a moment

   => (4) glitches due to the short unlock.

- - plan  - -

 In order to check this hypothesis the low finesse PRMI must serve as a good test configuration.

What I will do is to gradually decrease the offset in MICH such that the finesse of PRMI becomes higher.

And at each different finesse I will check the spectra, glitch rate, and etc.

Quote from #6231

        Low finesse PRMI      

In this configuration NO glitches ( a high speed signal with an amplitude of more than 4 or 5 sigma) were found when it was locked.

Is it because I didn't use AS55 ?? or because the finesse is low ??

Also, as we have already known, the up conversion noise (#6212) showed up -- the level of the high frequency noise are sensitive to the 3 Hz motion.

  6238   Mon Jan 30 23:10:02 2012 kiwamuUpdateSUSdrift mon script needs to be fixed

[Rana / Kiwamu]

We tried to set some parameters for the suspension drift monitor but the old matlab script, which automatically sets the values, didn't run because it uses the old mDV protocol.

The attached link below is a description about the script.

https://wiki-40m.ligo.caltech.edu/Computers_and_Scripts/All_Scripts#Drift

It needs to be fixed or upgraded by pynds.

  6240   Tue Jan 31 14:58:30 2012 kiwamuUpdateIOOlaser shuts down

[Steve/ Kiwamu]

 We found that the laser had completely shut off for ~ 4 hours even with all the PSL doors closed.

We are guessing it is related to the interlock system and Steve is working on it to fix it.

Quote from #6239

 The 2W Innilight shutdown shut when I opened side door for safety scan. This was not a repeatable by opening -closing side doors later on. Turned laser on, locked PMC and MC locked instantly. The MC was not locked this moring and it seemed that the MC2 spot was still some high order mode

like yesterday. MC lock was lost when the janitor bumped something around the MC.

 

  6266   Fri Feb 10 02:35:29 2012 kiwamuUpdateIOOcrazy ground motion

I gave up tonight's locking activity because the MC can't stay locked.

It seems that somehow the seismic noise became louder from about 1:00 AM.

I walked around the outside of the 40-m building to see what's going on, but no one was jumping or partying.

I am leaving the MC autolocker disabled so that the laser won't be driven crazy and the WFS won't kick the MC suspensions.

 

The attachment is a 3-hour trend of the seismometer outputs and the MC trans.

MCunlock.png

  6274   Fri Feb 10 23:19:09 2012 kiwamuUpdateIOOcross talk causing fake seimometer signals

[ Koji / Kiwamu ]

The frequent unlock of the MC are most likely unrelated to ground motion.

Although the reason why MC became unstable is still unclear.

 

 

There are two facts which suggest that the ground motion and the MC unlock are unrelated :

(1) It turned out that the seismometer signals (C1:PEM-SEIS-STS_AAA ) have a big cross talk with the MC locking signals.

    For example, when we intentionally unlocked the MC, the seismometer simultaneously showed a step-shaped signals, which looked quite similar to what we have observed.

    I guess there could be some kind of electrical cross talk happening between some MC locking signals and the seismometer channels.

    So we should not trust the signals from the STS seismometers. This needs a further investigation.

(2) We looked at the OSEM and oplev signals of some other suspended optics, and didn't find any corresponding fluctuations.

    The suspensions we checked are ETMX, ETMY, ITMX and MC1.

     None of them showed an obvious sign of the active ground motions in the past 24 hours or so.

Quote from #6266

It seems that somehow the seismic noise became louder from about 1:00 AM.

  6281   Wed Feb 15 05:29:22 2012 kiwamuUpdateLSCsensing matrix of PRMI

I have measured the sensing matrix of PRMI.

It seems that the MICH signal in the 3f ports (REFL33 and REFL165) were quite tiny, and because of that it is very tough to use them for the actual MICH control.

The data is coming soon.

  6283   Wed Feb 15 17:15:33 2012 kiwamuUpdateLSCsensing matrix of PRMI

I think I have told a lie in the last meeting -- the measured sensing matrix doesn't look similar to what Optickle predicts.

Smells like something is very wrong.

 

Measured sensing matrix

The measured matrix are shown in the diagram below.
The lengths of arrows corresponds to the signal strength in unit of V/m. The radial axis in in log scale.
The angle of arrows corresponds to their best demodulation phases.
sensingMAT.png

        Some obvious things:

  •  REFL11 : The separation angle between MICH and PRCL is narrow and it is far from the ideal 90 degree. This doesn't agree with the simulation.
  •  REFL33:  The MICH and PRCL signals are almost degenerated in their demodulation phase.
  •  REFL55 :  It shows non-90 degree separation. This doesn't agree with the simulation.
  •  REFL165 : The separation is close to 90 degree, but the signals are small. And I am not sure if the MICH signal is real or just noise.
  •  AS55 : Somehow it shows a nice 90 degree separation, but this result doesn't agree with the simulation.

 


Expected sensing matrix from a simulation

For a comparison here is a result from an Optickle simulation.
This time the radial unit is W/m instead of V/m, but they are qualitatively the same unit.
The radial axis is in log, so when it says 2, it means 10^2 [W/m].
PRMI_Optickle.png
 
 Simulation setup:
l_PRC  = 6.760 (see #4064)
l_asy  = 0.0364  (see #4821)
loss per optic = 50 ppm
 

Measurement

  •  Locked PRMI with the carrier anti-resonating in PRCL.
  •  Adjusted the control gains for both the MICH and PRCL control to have UGFs at ~ 100 Hz.
  •  Put a 30 dB notch filter  in each control servo at 283.1 Hz where an excitation signal will be.
  •  Excited PRCL and MICH at different time via the realtime lockng in the LSC front end. The amplitude is 1000 counts and the frequency is at 238.1 Hz.
    • For the MICH excitation, I have coherently and differentially excited ITMs
  •  Used DTT to take a transfer function (transfer coefficients at 283.1 Hz) from the lockin oscillator to each LSC demodulated signal.
    • Including AS55I/Q, REFL11I/Q, REFL33I/Q, REFL55I/Q and REFL165I/Q.
  •  Calibrated the obtained transfer functions from unit of counts/counts to V/m using the actuator response (#5637)

Quote from #6281
I have measured the sensing matrix of PRMI.
It seems that the MICH signal in the 3f ports (REFL33 and REFL165) were quite tiny, and because of that it is very tough to use them for the actual MICH control.
The data is coming soon.

  6284   Thu Feb 16 03:47:16 2012 kiwamuUpdateLSCglitch table

I updated the table which I posted some time ago (#6231). The latest table is shown below.

It seems that the glitches show up only when multiple DOFs are locked.

Interesting thing is that when the low finesse PRMI is locked with a big MICH offset (corresponding to a very low finesse) it doesn't show the glitches.

Qualitatively speaking, the glitch rate becomes higher as the finesse increases.

I will try SRMI tomorrow as this is the last one which I haven't checked the presence of the glitches.

 

 

 Yarm

(POY11 -->

ETMY)

Xarm

(POX11 --> ETMX)

MICH

(AS55-->BS)

or

(AS55 --> ITMs)

Half PRMI

(REFL11 --> PRM)

or

(REFL33 --> PRM)

low finesse PRMI

(ASDC --> ITMs)

(REFL33 --> PRM)

PRMI (carrier)

(AS55 --> ITMs)

(REFL33 --> PRM)

PRMI (sideband)

(AS55 --> ITMs)

(REFL33 --> PRM)

DRMI
AS55 NO NO NO NO glitch (depends on finesse)
glitch glitch glitch
REFL11 NO NO NO NO glitch (depends on finesse)
glitch glitch glitch
REFL33 NO NO NO NO - glitch glitch glitch
REFL55 NO NO NO NO glitch(depends on finesse) glitch glitch glitch
REFL165 NO NO NO - - - - -
POX11 - NO NO NO  - glitch glitch glitch
POY11 NO - NO NO  - glitch glitch glitch
POP55 - - - -  -  - - -
                 

 

 

  6285   Thu Feb 16 04:02:16 2012 kiwamuUpdateLSCinsane REFL165 DC output

I found that the DC monitor of the REFL165 was showing 9 V regardless of how much laser power goes to the diode.

I am worried about whether the RF output is also broken.

It needs to be checked and I will leave this to Suresh as one of his morning tasks.

  6286   Thu Feb 16 04:29:30 2012 kiwamuUpdateLSCupconversion noise from BS motion

Sometimes ago I reported that there have been a kind of upconversion noise when PRM was excited (#6211).

This time I found another one, which showed up when BS was excited.

Assuming this is related to some kind of scattering process and also assuming this is from the same scattering body as that for the PRM driven case,

we may be able to localize and perhaps identify the scattering body.

 

 

(Measurement Condition)

All the suspended optics are intentionally misaligned except for ITMY so that the laser directly goes through to the dark port without any interference.
Then BS_POS is excited at 3 Hz with amplitude of 1000 counts by an oscillator in the realtime lockin system.
 I also excited PITCH and YAW of BS and found that driving the angular motions didn't produce any upconversion noise.
 I didn't excite ITMY to do the same test because I was too lazy.

(Noise spectrum)

The plot below shows the upconversion noise observed at AS55 and REFL11.
The reference curves were obtained when no excitation were applied on BS_POS.
It is obvious that the AS55 signal shows a typical upconversion behavior.
 
Untitled.png

 

  6291   Thu Feb 16 23:12:55 2012 kiwamuUpdateIOOMC unlocking frequently

The MC became crazy again.

It seems that there were corresponding steps in the OSEM signals. Look at the one-day trend posted below.

MCsteps.png

  6292   Fri Feb 17 01:02:22 2012 kiwamuUpdateIOOMC is back to normal

[Koji / Kiwamu]

 The MC is now back to normal. The beam pointing to the interferometer is good.

There were two different issues :

  • A mechanical mount was in the MC WFS path.
  • There were some loose connections in the SUS rack

 

Slid have we the position of the mechanical mount. Nicely the WFS beam go through now.

And also I pushed all the connectors associated with the MC SUS OSEMs in the SUS rack.

After pushing the connectors, the MC1 OSEM readouts dramatically changed, which actually more confused us.

As shown in the 3 hours trend below, the OSEM readouts have changed a lot (shown in the middle of the plot with arrows). Some bumps after the steps correspond to our alignment efforts.

MCconnections.png

Quote from #6291

The MC became crazy again.

 

  6293   Fri Feb 17 04:45:48 2012 kiwamuUpdateLSCsensing matrix of PRMI

I locked the PRMI with the AS55I and Q combination.

It seems the glitche rate decreased,

but I am not 100 % sure because the rest of the demod signals (i.e. REFL11 and etc) were showing relatively big signals (noise ?), which may cover the glitches.

Also the optical gain of PRCL at AS55I doesn't agree with my expectation based on the obtained sensing matrix (#6283).

It looks too low and lower than the measured sensing matrix by a factor of 50 or so.

I will continue working on this configuration tomorrow and then move on to the SRMI locking as a part of the glitch hunting activity.

Quote from #6287

So why don't you use AS55I and Q for the control of PRMI???

  6295   Sat Feb 18 16:58:59 2012 kiwamuUpdateIOOMC suspension realigned

[ Den / Kiwamu]

 We have realigned the MC suspensions so that the WFS servos are smoothly engaged.

Now it seems working fine. The beam pointing to the interferometer also looks okay.

The WFSs control kept failing to engage the servos because of large misalignments in the MC suspensions.

When the TEM00 was locked, the transmitted light was only about 1200 counts and the reflected light was about 2.8 counts.

We tweaked MC1, MC2 and MC3.

Quote from #6294

When I came to the 40m this afternoon, the MC was unlocked. Here is the trend of MC_F for last 2 hours

  6298   Tue Feb 21 04:30:02 2012 kiwamuUpdateLSCY arm + PRMI

I tried the "Yarm + PRMI" configuration to see what happens.
The Y arm was locked at a resonance and held with the ALS technique.
On the other hand, the X arm was freely swinging.

I briefly tried severl demod signals to calm down the central part, but didn't succeed.
Now I feel I really want to have the X arm locked with the ALS technique too.
Give me the beat-box !

The attached screen shot shows the transmitted light of both arms as a function of time.
TRY is always above 1, since it was kept at a resonance.
Sometimes TRY went to 50 or so.

Untitled.png

  6300   Tue Feb 21 16:10:29 2012 kiwamuUpdateIOOdegradation in input PZT1

PZT1, the one with Koji's custom mid-HV driver (#5447), is getting degraded.

The movable range in the pitch direction became narrower than what it used to be (maybe a factor of 3 estimated by looking at the beam spots).

I think we should raise the priority level of the active TTs for the next vent.

 

I have been having a feeling that the PZT1 response is getting smaller since the end of the last year, but now I am confident

because I could see the difference between the movable ranges of Yaw and Pitch, and they used to have approximately the same amount of the movable ranges.

Right now this is not a serious issue as the beam pointing determined by the MC alignment is so good that the Pitch range doesn't rail.

I won't be surprised if it becomes completely immovable in 3 month.

  6301   Tue Feb 21 18:39:11 2012 kiwamuUpdateGreen LockingNew BBPDs installed

Two new BBPDs have been installed on the PSL table.

The first one was installed by Koji a few days ago, and I stalled the second one today.

They will serve as beat-note detectors for the green locking.

Next step : I have to lay down a long SMA cable which goes from the BBPD to the IOO rack.

  6303   Wed Feb 22 01:53:57 2012 kiwamuUpdateLSCupdate on glitch table

I tried SRMI. The glitch rate wasn't as high as that of PRMI but it happened once per 10 sec or so.

 

 

 Yarm

(POY11 -->

ETMY)

Xarm

(POX11 --> ETMX)

MICH

(AS55-->BS)

or

(AS55 --> ITMs)

Half PRMI

(REFL11 --> PRM)

or

(REFL33 --> PRM)

low finesse PRMI

(ASDC --> ITMs)

(REFL33 --> PRM)

PRMI (carrier)

(AS55 --> ITMs)

(REFL33 --> PRM)

PRMI (sideband)

(AS55 --> ITMs)

(REFL33 --> PRM)

SRMI(NEW)

(AS55-->ITMs)

(REFL11I --> SRM)

DRMI
AS55 NO NO NO NO glitch (depends on finesse)
glitch glitch glitch glitch
REFL11 NO NO NO NO glitch (depends on finesse)
glitch glitch glitch glitch
REFL33 NO NO NO NO - glitch glitch glitch glitch
REFL55 NO NO NO NO glitch(depends on finesse) glitch glitch glitch glitch
REFL165 NO NO NO - - - - - -
POX11 - NO NO NO  - glitch glitch - glitch
POY11 NO - NO NO  - glitch glitch - glitch
POP55 - - - -  -  - -   -
                   

 

Quote from #6284

I updated the table which I posted some time ago (#6231). The latest table is shown below.

It seems that the glitches show up only when multiple DOFs are locked.

 

  6304   Wed Feb 22 13:28:22 2012 kiwamuUpdateLSCY arm + central part locking

Last night I tried the "Y arm + central part" locking again. Three different configuration were investigated :

  •  Y arm + DRMI
  •  Y arm + PRMI
  •  Y arm + MICH

In all the configurations I displaced the Y arm by 20 nm from the resonance.

As for the DRMI and PRMI configurations I wasn't able to acquire the locks.

As for the MICH configuration, the MICH could be locked with AS55. But after bringing the Y arm to the resonance point the lock of MICH was destroyed.

  6306   Wed Feb 22 19:45:33 2012 kiwamuUpdateLSChow much length offset do we need ?

I did a quick calculation to see if the offset of the arm length which I tried last night was reasonable or not.

The conclusion is that the 20 nm offset that i tried could be a bit too close to a resonance of the 55 MHz sidebands.

A reasonable offset can be more like 10 nm or so where the phases of all the laser fields don't get extra phases of more than ~ 5 deg.


 

The attached plot shows where the resonances are for each sideband as a function of the displacement from the carrier's resonance.

armresonance.png

The red solid line represent the carrier, the other solid lines are for the upper sidebands and the dashed lines are for the lower sidebands.

The top plot shows the cavity power and the bottom plot shows how much phase shift the fields get by being reflected by the arm cavity.

Apparently the closest resonances to the the main carrier one are that of the 55 MHz sidebands, and they are at +/- 22 nm.

So if we displace the arm length by 22 nm, either of the 55 MHz sidebands will enter in the arm cavity and screw up the sensing matrix for the 55 MHz family.

Quote from #6304

In all the configurations I displaced the Y arm by 20 nm from the resonance.

  6310   Fri Feb 24 03:58:13 2012 kiwamuUpdateLSCY arm + PRMI part II

I tried the Yarm + PRMI configuration again.

The PRMI part was locked, but it didn't stay locked during the Y arm was brought to the resonance point.

I will post the time series data later.

 

(locking of the PRMI part)

Tonight I was able lock the PRMI when the arm was off from the resonance by 10 nm (#6306).

This time I used REFL11Q to lock the MICH instead of the usual AS55Q because the MICH didn't stay locked with AS55Q for some reason.

The PRCL was held by REFL33I as usual.

Also I disabled the power normalization for the error signals because it could do something bad during the Y arm is borough to the resonance.

In order to reduce the number of the glitches, PRM was slightly misaligned because I knew that the lower finesse gives fewer glitches.

  6311   Fri Feb 24 04:12:44 2012 kiwamuUpdateSUSfreeswing test
The following optics were kicked:
MC1 MC2 MC3 ETMX ETMY ITMX ITMY PRM SRM BS
Fri Feb 24 04:11:15 PST 2012
1014120690
 
Steve (or anyone), can you restore the watchdogs when you come to the lab in the morning ?

Quote from #6305

Kiwamu (or whoever is here last tonight): please run the free-swing/kick script (/opt/rtcds/caltech/c1/scripts/SUS/freeswing) before you leave, and I'll check the matrices and update the suspensions tomorrow morning.

  6313   Fri Feb 24 15:01:31 2012 kiwamuUpdateLSCY arm + PRMI part II

The figure below shows the time series of the Y arm + PRMI trail.

time_series.png

(Top plot )

  Normalized TRY (intracavity power). It is normalized such that it shows 1 when the arm is locked with the recycling mirrors misaligned.

(Middle plot)

ASDC and REFLDC in arbitrary unit.

(Bottom plot)

The amount of the arm length detuning observed at the fine frequency discriminator.

 

(Sequence)

At t = 20 sec, the amount of detuning was adjusted so that the cavity power goes to the maximum. At this point the PRM was misaligned.

At t = 30 sec, the cavity length started being slowly detuned to 10 nm. As it is being detuned the intracavity power goes down to almost zero.

At t = 45 sec, the alignment of PRM was restored. Because of that, the REFLDC and ASDC diodes started receiving a large amount of light.

At t = 85 sec, the PRCL and MICH were locked. The REFLDC signal became a high value as the carrier light is mostly reflected. The ASDC goes to a low value as the MICH is kept in the dark condition.

At t = 100 sec, the length started being slowly back to the resonance while the PRMI lock was maintained.

At t = 150 sec, the lock of the PRCL and MICH were destroyed. With the arm fully resonance, I wasn't able to recover the PRMI lock with the same demod signals.

Quote from #6310

I tried the Yarm + PRMI configuration again.

The PRMI part was locked, but it didn't stay locked during the Y arm was brought to the resonance point.

I will post the time series data later.

 

  6317   Fri Feb 24 19:18:28 2012 kiwamuUpdateLSCY arm + PRMI : how they should look like

I calculated how the DC signals should look like in the Y arm PRMI configuration.

The expected signals are overlaid in the same plot as that of shown in #6313.

You can see there are disagreements between the observed and expected signals in the plot below at around the time when the arm is brought to the resonance.

 

(expected behaviors)

  •  TRY: At the end it should be at 1 (remember TRY is normarlized) and should not go more than that, since the power-recycling is in a weird situation and it is not fully recycling the power.
  •  ASDC: It should become brighter at the end because the arm cavity flips the sign of the reflected light and hence the dark port must be on a bright fringe.
  •  REFLDC: It will decrease a little bit because the arm cavity and MICH try to suck some amount of the power into the interferometer.

 

expected_time_series.png

Quote from #6313

The figure below shows the time series of the Y arm + PRMI trail.

  6319   Fri Feb 24 23:14:09 2012 kiwamuUpdateCDStdsavg went crazy

I found that the LSCoffset script didn't work today. The script is supposed to null the electrical offsets in all the LSC channels.

I went through the sentences in the script and eventually found that the tdsavg command returns 0 every time.

I thought this was related to the test points, so I ran the following commands to flush all the test point running and the issue was solved.

[term]> diag              
[diag]>open               
[diag]> diag  tp clear *  
 

EDIT, JCD 11June2012:  3rd line there should just be [diag]> tp clear *

  6320   Sat Feb 25 00:37:42 2012 kiwamuUpdateSUSoplev spectra during PRMI lock

Somehow the angular stability of the central part have not been so great.

Also the angular motions look fluctuating a lot and they seem to be related with the glitches.

I took the oplev spectra when the PRMI is locked and unlocked to see whether if something obviously crazy is going on or not.

They seem ok to me except that the PRM pitch shows an extra bump at around 2-3 Hz when the PRMI is locked. But I don't think it's prominent.

 


- The attached files show the oplev spectra. When the PRMI is locked the PRM and both ITMs are under the length control.

(red) pitch when PRMI is locked

(blue) yaw when PRMI is locked

(orange) pitch without any length controls

(cyan) pitch without any length controls

 

  6321   Sat Feb 25 14:27:26 2012 kiwamuUpdateLSCglitches in the RFPD outputs

Last night I took a closer look at the LSC analog signals to find which components are making the glitches.

I monitored the RFPD output signals and the demodulated signals at the same time with an oscilloscope when the PRMI was kept locked.

Indeed the RFPD outputs have some corresponding fast signals although I only looked at the RELL11 I and Q signals.

(REFL33 didn't have sufficiently a high SNR to see the glitches with the oscilloscope.)

I will check the rest of channels.

  6330   Tue Feb 28 12:00:54 2012 kiwamuUpdateLSCinstalled anti-whitening filters

I found that none of the filter banks in the LSC input signals have the precise anti-whitening filters.

I installed the precise filters on REFL11, REFL33, REFL55 and AS55 based on Jenne's measurement (#4955)

After installing them I briefly checked the REFL11 sensing matrix with the PRMI locked, but it didn't change so much from what I got (#6283).

But I felt that the PRMI became more robust after that ... I just felt so ...

 


(Background)

The lock of the PRMI doesn't look healthy, especially the sensing matrix doesn't make sense at all (#6283).
A very staring thing in the sensing matrix is that the REFL11 and REFL55 didn't show the 90 degree separation between MICH and PRCL.
So I suspected some electronics, particularly the demodulation boards.
 

(What I did)

I checked the anti-whitening filters shape to see if they are ok or not.
I found that they all had the default filters of two zeros at 150 Hz and two poles at 15 Hz. So they weren't quite tuned.
I thought this could be a problem when I measure the sensing matrix because I usually excite the length DOFs at a high frequency of 283.1 Hz
and the mismatches between the anti-whitening and whitening filters may lead to something funny at such a high frequency.
 
So I installed the precise filters on REFL11, REFL33, REFL55 and AS55.
After that I did a orthogonality test on each I-Q pair of the demod signals to correct the D-phases and the relative gain between I and Q.

 

(Next ?)

 Rana and I discussed the plan and decided to go back to a simple Michelson which should be easy enough to understand what is going on and should allow us a complete set of measurements.
Our big concern behind it is that we maybe locking the PRMI at a funny operation point.
In order to assess the issue I will do the following actions on the Michelson at first and then apply the same things on the PRMI later :
  • Check  the amount of of the sidebands using the OSA
  • Check the amount of the DC light
  • Check the sensing matrix to see if the absolute values in watt / meter make sense or not
    • This work needs calibrations on all the demodulated board (this is equivalent to measuring the conversion losses of the mixers in the demod boards).
  • Measure the contribution from the RAMs (it must be measurable by some means)
  6331   Tue Feb 28 15:48:32 2012 kiwamuUpdateLSCinstalled anti-whitening filters

I installed the rest of the precise anti-whitening filters. Now all of the LSC sensors have the right filters.

Quote from #6330

I found that none of the filter banks in the LSC input signals have the precise anti-whitening filters.

I installed the precise filters on REFL11, REFL33, REFL55 and AS55 based on Jenne's measurement (#4955)

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