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ID Date Author Typeup Category Subject
  6366   Tue Mar 6 22:23:04 2012 KojiUpdateLSC22/110MHz path for POP

 

 As par Kiwamu's request, RF filters for POP22 and POP110 were installed. They are not really nice. We need to replace it with more fancy electronics.
More to come later.

 

  6367   Tue Mar 6 23:14:38 2012 ranaUpdateSUSOptical Lever had bad filters

 We found that that bounce (16.1 Hz) and roll (23.5 Hz) modes on the ITMX were much higher than on the ITMY. After some checking, it seems that the bandstop filters for the

SUSPOS, SUSPIT, SUSYAW, and SUSSIDE loops are set to the correct frequencies. However, the OLPIT and OLYAW had not been set correctly. I have copied the SUS filters into the OL filterbanks and reloaded all the filter banks. Attached are the comparison of old, bad, OL with the SUS ones.

The same cockamamie situation was there for the BS & ITMY as well. Although we still don't have the roll mode frequencies listed in the mechanical resonances wiki, I have guessed that the ITMY roll frequency is the same as the ITMX, since they have nearly the same bounce frequency. OL filters for the BS & ITMY are now at the right frequency (probably). Keiko is on top of fixing things for the other optics.

I think this whole notching adventure was in Leo's hands several months ago, but WE forgot to point him at the OLs in addition to the SUS. I blame Kiwamu 50% for not supervising him and Koji by 45% for not supervising Kiwamu. The other 5% goes to someone else. You know who you are.

  6368   Tue Mar 6 23:37:31 2012 keikoUpdateSUSMICH noise budget - SUS check

Here are the OSEM spectrum of MICH suspensions (BS, IX, IY). Bounce and Roll modes are shown on 16 and 23 Hz. The filters for them has been checked.

Mar6sus1.pdf

Mar6sus2.pdf

Mar6sus3.pdf

keiko, kiwamu, Rana

  6369   Wed Mar 7 04:08:48 2012 kiwamuUpdateSUSBS SIDE gain was too low

The BS SIDE damping gain seemed too low. The gain had been 5 while the rest of the suspensions had gains of 90-500.

I increased the gain and set it to be 80.

 

I did the "Q of 5" test by kicking the BS SIDE motion to find the right gain value.

However there was a big cross coupling, which was most likely a coupling from the SIDE actuator to the POS motion.

Due to the cross coupling, the Q of 5 test didn't really show a nice ring down time series. I just put a gain of 80 to let the Q value sort of 5.

I think we should diagonalize the out matrices for all the suspensions at some point.

  6370   Wed Mar 7 11:20:23 2012 steveUpdateSUSoplev qpd offsets zeroed

All oplev qpd quadrons were zeroed by offset  in blocked dark condition.

  6371   Wed Mar 7 11:44:29 2012 JenneUpdateGreen LockingXgreen beatnote cable made, laid

The Xgreen PD now has a cable going over to the beatbox. Once beatbox characterization is done I can re-find the beat, and we can do some stuff with the beatbox.

  6372   Wed Mar 7 13:30:17 2012 JimUpdatePEMadded TPs and JIMS channels to PEM front-end model

[Jim Ryan]

The PEM model has been modified now to include a block called 'JIMS' for the JIMS(Joint Information Management System) channel processing. Additionally I added test points inside the BLRMS blocks that are there. These test points are connected to the output of the sqrt function for each band. I needed this for debugging purposes and it was something Jenny had requested.

The outputs are taken out of the RMS block and muxed, then demuxed just outside the JIMS block. I was unable to get the model to work properly with the muxed channel traveling up or down levels for this. Inside the JIMS block the information goes into blocks for the corresponding seismometer channel.

For each seismometer channel the five bands are processed by comparing to a threshold value to give a boolean with 1 being good (BLRMS below threshold) and 0 being bad (BLRMS above threshold). The boolean streams are then split into a persistent stream and a non-persistent stream. The persistent stream is processed by a new library block that I created (called persist) which holds the value at 0 for a number of time steps equal to an EPICS variable setting from the time the boolean first drops to zero. The persist allows excursions shorter than the timestep of a downsampled timeseries to be seen reliably.

The EPICS variables for the thresholds are of the form (in order of increasing frequency):

C1:PEM-JIMS_GUR1X_THRES1

C1:PEM-JIMS_GUR1X_THRES2

etc.

The EPICS variables for the persist step size are of the form:

C1:PEM-JIMS_GUR1X_PERSIST

C1:PEM-JIMS_GUR1Y_PERSIST

etc.

I have set all of the persist values to 2048 (1 sec.) for now. The threshold values are currently 200,140,300,485,340 for the GUR1X bands and 170,105,185,440,430 for the GUR1Y bands.

The values were set using ezcawrite. There is no MEDM screen for this yet.

PEM model was restarted at approx. 11:30 Mar. 7 2012 PST.

 

  6374   Wed Mar 7 15:56:36 2012 KojiUpdateLSC22/110MHz path for POP

The RF separator installed comprises of the Minicircuits filters cascaded as in the figure below.
This has one input and 4 output ports for 11, 22, 30-60, and 110MHz signal.
As seen in this entry #6167, we have 22 and 110MHz signals together with 11, 44, 66MHz signals.
They may be demodulated via a harmonic characteristic of the mixers. (Remeber mixers are not multipliers.)

RFseparator.png

 Of course the big concern is the impedance matching for those signals as usual.
The 2nd attachment shows measured impedance of the circuits with all of the ports terminated.
From the complex impedance, we can calculate the reflection coefficient. The 44 and 110MHz
components look correctly matched while the others seems largely reflected.
This certainly is not a nice situation, as the reflection can make the amplifier next to the PD unhappy
(although the reflected power is tiny in our case).

In our case more eminent problem is that the amplitude of the 22MHz signal can vary depending on the cable length by
factor of 10 in amplitude. (c.f. VSWR on the 2nd attachment.)

The transmission to each port was measured. The separation of the signals looks good. But the attenuation of the
targetted signals (i.e. insertion losses) are qulitatively consistent with the impedance. Again these losses are depend
on the cable length.

 

 

  6375   Wed Mar 7 16:32:09 2012 keikoUpdateLSCOSA

 I swap an OSA at PSL and OSA at REFL. It was because the PSL-OSA had a better resolution, so we place this better one at REFL. The ND filter (ND3) which was on the way to REFL OSA was replaced by two BSs, because it was producing dirty multiple spots after transmitting.

  6376   Wed Mar 7 17:39:40 2012 keikoUpdateLSCMICH noise budget on 5 Mar

 This is the calibrated MICH noise budget on Mar 5. There was a sharp peak at 1Hz and a blob on 3 Hz. The demod phase was adjusted for AS55Q.

Mar5-MICHbudget.png

 

  6378   Wed Mar 7 19:10:06 2012 kiwamuUpdateLSCREFL OSA : how the signal look like

Just a quick report on the REFL OSA.

The attached plot below shows the raw signal from the REFL OSA which Keiko installed in this afternoon.

When the data was taken the beam on the REFL OSA was a direct reflection from PRM with the rest of the suspended mirrors misaligned.

One of the upper and lower 11 MHz sidebands is resolved (it is shown at 0.12 sec in the plot) while the other one is still covered by the carrier tail.

The 55 MHz upper and lower sidebands are well resolved (they are at 0.06 and 0.2 sec in the plot).

One of the oscilloscopes monitoring the OSA signals in the control room has a USB interface so that we can record the data into a USB flash memory and plot it like this.

OSArefl.png

Quote from #6375

 I swap an OSA at PSL and OSA at REFL. It was because the PSL-OSA had a better resolution, so we place this better one at REFL. The ND filter (ND3) which was on the way to REFL OSA was replaced by two BSs, because it was producing dirty multiple spots after transmitting.

 

  6379   Wed Mar 7 20:06:23 2012 KojiUpdateLSCREFL OSA : how the signal look like

I'm puzzled why the 11MHz peak can be such high considering 1.7~2 times smaller the modulation depth.

  6380   Wed Mar 7 20:53:13 2012 keikoUpdateLSCMICH noise budget on 5 Mar

 

 Mar6-MICHbudget.png

This is the MICH noise budget on 6th March. 1Hz peak got a bit better as the BS sus control gain was increased.

 

  6381   Wed Mar 7 21:13:30 2012 ranaUpdateDAQNDS2

 I noticed that NDS2 was not running on mafalda as it should be. Instead, there were a couple of zombie MEDMs using up 99% of the CPU. I killed the zombies and have run the 'build channel list' script. When it finished, I tried to restart the nds server, but got the following error in the log file. Email has been dispatched to JZ.

mafalda:logs>less nds2-mafalda-201203072111.log

Configuring from file: nds2.conf
Allow list: ALL
terminate called after throwing an instance of 'std::runtime_error'
  what():  Insufficient arguments
  6382   Wed Mar 7 22:04:05 2012 kiwamuUpdateLSCREFL OSA : how the signal look like

I was also wondering about the same thing, comparing with what Mirko obtained before with the same OSA ( #5519).

Quote from #6379

I'm puzzled why the 11MHz peak can be such high considering 1.7~2 times smaller the modulation depth.

 

  6384   Wed Mar 7 23:29:28 2012 keikoUpdateLSCREFL OSA observation

 kiwamu, keiko

 

 

REFLOSA.png

We measure the REFL OSA spectrum when (1) direct reflection from the PRM (2) CR lock at PRC (3) SB lock at PRC. When CR lock, both SBs are reflected from the PRC and when SB lock (ref line), some SB is sucked by PRM and looked lower than the other two lines.

 

  6385   Thu Mar 8 00:57:48 2012 keikoUpdateLSCMICH noise budget on Mar 5, Mar 6, and old

Here is the recent two noise budgets of MICH, with the old measurement by Jenne. The most latest Mar 6 data is quite close to the old data, even better around 20-30 Hz. Probably some scattering source was improved?

Mar7MICHbudgettotal.png

  6386   Thu Mar 8 04:13:12 2012 kiwamuUpdateLSCupdate on the locking activity

[Keiko / Kiwamu]

 Some updates on the locking activity:

  • Started summarizing the data of the Michelson lock in a wiki page:
  • Gradually moving on to the PRMI lock
    • The lock stays for reasonably a long time (~20 min or more)
    • POP22/110 demod signals seemed just ADC noise.
    • A first noise budget is in process
      • The glitches make the noise level worse above 40 Hz or so in both the MICH and PRCL budgets.
    • Sensing matrix will be measured tomorrow
    • The data will be also summarized in a wiki page
  6388   Thu Mar 8 23:37:03 2012 kiwamuUpdateIOOdither Y arm dither script

I disabled the feedback to the PZT1 PITCH in the Y arm dithering scripts so that it won't push the beam away from the good point.

Currently one has to do a manual alignment only for the PZT PITCH but the rest of DOFs are still able to be automatically aligned with the script.

Quote from #6357

 The polarity for controlling the PZT1 PITCH seems to have flipped for some reason.

  6390   Fri Mar 9 10:44:57 2012 steveUpdateRF SystemOSA

Optical spectrum analyzers like the Attachment made by Coherent , Meles Griot- CVI and Spectral Product are all discontinued.

The 40m have Coherent models C240 analyzer with controller C251 Their Finesse measured in 2004: sn205408  F302,  sn205409  F396,

Jenne borrowed Jan's Meles Griot model 13SAE006, Peter King has the same model. FSR 300 MHZ, finnees 200 minimum

  6393   Fri Mar 9 13:34:13 2012 keikoUpdateLSCupdate on the locking activity

We tried to measure the sensing matrix for MICH and PRCL last night. They look too much mixed as we expect... the matrix may be posted later. We suspect the IX and IY of the MICH excitation is not balanced very well, although Kiwamu adjusted that about two weeks ago, and it is mixing the dof. We'll try to balance it again, ans see the matrix. 

Keiko, Kiwamu

 

Quote:

[Keiko / Kiwamu]

 Some updates on the locking activity:

  • Started summarizing the data of the Michelson lock in a wiki page:
  • Gradually moving on to the PRMI lock
    • The lock stays for reasonably a long time (~20 min or more)
    • POP22/110 demod signals seemed just ADC noise.
    • A first noise budget is in process
      • The glitches make the noise level worse above 40 Hz or so in both the MICH and PRCL budgets.
    • Sensing matrix will be measured tomorrow
    • The data will be also summarized in a wiki page

 

  6395   Fri Mar 9 16:00:46 2012 steveUpdateGreen Lockinglaser emergency shut down switch replaced at the south end

Over-sized local laser emergency switch was held by large C clamp at the south end. This was replaced by a smaller one and it is mounted with magnets.

The Innolight laser was turned off, while the interlock was wired.

  6397   Fri Mar 9 20:44:24 2012 Jim LoughUpdateCDSDAQ restart with new ini file

DAQ reload/restart was performed at about 1315 PST today. The previous ini file was backed up as c1pem20120309.ini in the /chans/daq/working_backups/ directory.

I set the following to record:

The two JIMS channels at 2048:
[C1:PEM-JIMS_CH1_DQ] Persistent version of JIMS channel. When bit drops to zero indicating something bad (BLRMS threshold exceeded) happens the bit stays at zero  for >= the value of the persist EPICS variable.
[C1:PEM-JIMS_CH2_DQ] Non-persistent version of JIMS channel.

And all of the BLRMS channels at 256:
Names are of the form:
[C1:PEM-RMS_ACC1_F0p1_0p3_DQ]
[C1:PEM-RMS_ACC1_F0p3_1_DQ]

On monday I intend to look at the weekend seismic data to establish thresholds on the JIMS channels.

256 was the lowest rate possible according to the RCG manual. The JIMS channels are recorded at 2048 because I couldn't figure out how to disable the decimation filter. I will look into this further.

  6398   Sat Mar 10 02:00:03 2012 keikoUpdateLSCupdate on the locking activity

ITMX and ITMY balance for the MICH excitation (lockin) is adjusted again. Now it's ITMx = -0.992, ITMy = 1 for MICH (lockin output matrix values).

RA: what were the old values? Does this change make any difference for the signal mixing noticed before?

  6400   Mon Mar 12 01:04:18 2012 keikoUpdateLSCRAM simulation update, RAM LSC matrix

 I calculated the DRMI RAM LSC matrix with RAM and the operation point offsets.

  • configuration: C1 DRMI
  • RAM is added by an Mach-Zehnder ifo placed before the PRM
  • demodulation phases are optimised for each DoF
  • the operation points offset from the PDH signals are calculated and added to the optical configuration as mirror position offsets
  • Then the matrix is calculated with the offsets and the RAM
  • The set of the scrips are found as RAMmatrix.m, normMAT.m, newGetMAT.m,  on CVS/ifomodeling/40m/fullIFO_Optickle. They are a bit messy scripts at this moment.

Results:

(1) No RAM LSC matrix

  PRCL MICH SRCL
REFL11I 1 -0.001806 -0.000147
AS 55Q 0.000818 1 0.000474
AS 55 I 1.064561 902.292816 1

(2) With 1% RAM mod index of PM (normalised by (1) )

  PRCL MICH SRCL
REFL11I 1.000618 -0.001837 -0.000163
AS 55Q 0.000919 1.000521 0.000495
AS 55 I 1.169741 924.675187 1.018479
 

(3) With 5% RAM mod index of PM (normalised by (1) )

  PRCL MICH SRCL
REFL11I 0.999986 -0.001812 -0.000150
AS 55Q 0.000838 1.000028 0.000479
AS 55 I 1.084598 906.83668 1.003759
 

  6401   Mon Mar 12 18:57:58 2012 keikoUpdateLSCRAM simulation update, RAM LSC matrix

Quote:

 I calculated the DRMI RAM LSC matrix with RAM and the operation point offsets.

  • configuration: C1 DRMI
  • RAM is added by an Mach-Zehnder ifo placed before the PRM
  • demodulation phases are optimised for each DoF
  • the operation points offset from the PDH signals are calculated and added to the optical configuration as mirror position offsets
  • Then the matrix is calculated with the offsets and the RAM
  • The set of the scrips are found as RAMmatrix.m, normMAT.m, newGetMAT.m,  on CVS/ifomodeling/40m/fullIFO_Optickle. They are a bit messy scripts at this moment.

Results:

(1) No RAM LSC matrix

  PRCL MICH SRCL
REFL11I 1 -0.001806 -0.000147
AS 55Q 0.000818 1 0.000474
AS 55 I 1.064561 902.292816 1

(2) With 1% RAM mod index of PM (normalised by (1) )

  PRCL MICH SRCL
REFL11I 1.000618 -0.001837 -0.000163
AS 55Q 0.000919 1.000521 0.000495
AS 55 I 1.169741 924.675187 1.018479
 

(3) With 5% RAM mod index of PM (normalised by (1) )

  PRCL MICH SRCL
REFL11I 0.999986 -0.001812 -0.000150
AS 55Q 0.000838 1.000028 0.000479
AS 55 I 1.084598 906.83668 1.003759
 

Adding some more results with more realistic RAM level assumption.

(4) With 0.1% RAM mod index of PM (normalized by (1) )

  PRCL MICH SRCL
REFL11I 0.99999 -0.001807 -0.000148
AS 55Q 0.000822 1.000002 0.000475
AS 55 I 1.068342 906.968167 1.00559
 

(5) With 0.5% RAM mod index of  PM (normalized by (1) )

  PRCL MICH SRCL
REFL11I  0.999978  -0.001810    -0.000149 
AS 55Q 0.000830  1.000010  0.000476 
AS 55 I 1.075926 904.321433  1.001677
 

  6402   Mon Mar 12 22:14:56 2012 SureshUpdateRF SystemCalibration of Demod Board Efficiency.

I have completed the calibration of the demod board efficiencies.  Here is the schematic of the set-up.

 Calibration_Schematic.png

The data is given below and the data-file is attached in several different formats.

 Demod_calib.png

 

  6403   Tue Mar 13 07:04:55 2012 kiwamuUpdateLSCevolution of the sensing matrix in PRMI as a function of time

The punch line is -- the sensing matrix still looks strange in the PRMI configuration.

 

I have been measuring the sensing matrix of the PRMI configuration because it didn't make sense (#6283).

One strange thing I have noticed before was that all the I-phase signals showed a weird behavior -- they fluctuate too much in time series.

Tonight I measured the sensing matrix again but this time I recorded them as a function of time using the realtime LOCKINs in the LSC front end.

The attached plots are the responses (optical gains) of PRCL and MICH in watts / meter at various sensors in time series.

I will explain some more details about how I measured and calibrated the data in another elog entry.

 

PRCL.png

 MICH.png

 

  6404   Tue Mar 13 13:28:31 2012 Ryan FisherUpdateCDSDAQ restart with new ini file
Extra note: This was the ini file that was edited:
/cvs/cds/rtcds/caltech/c1/chans/daq/C1PEM.ini
  6405   Tue Mar 13 16:40:06 2012 kiwamuUpdateLSCevolution of the sensing matrix in PRMI as a function of time: details

Here I describe the measurement of the sensing matrix.

 

Motivations

  There were two reasons why I have been measuring the sensing matrix :

  1.  I wanted to know how much each element in the sensing matrix drifted as a function of time because the sensing matrix didn't agree with what Optickle predicted (#6283).
  2.  I needed to estimate the MICH responses in the 3f demodulated signals, so that I can decide which 3f signal I should use for holding MICH.

 I will report #2 later because it needs another careful noise estimation.

 

Measurement

 In order to measure the sensing matrix, the basic steps are something like this:

  1. Excite one of the DOF at a certain frequency, where a notch filter is applied in the LSC servos so that the servos won't suppress the excitation signal.
  2. Demodulate the LSC signals (e.g. C1:LSC-REFL11_I_ERR and etc.,) by the realtime LOCKINs (#6152) at the same frequency.
  3. Calibrate the obtained LOCKIN outputs to watts/meter.
In the actual measurement I choose the frequency of the excitation signal to be at 283.1 Hz,
at which any of the LSC servos don't have gains of more than 1 and there were no particular structures in the spectra.
For the amplitude of the excitation, I usually choose it to be 1000 - 2000 counts.
Because all the actuators have response functions of approximately 10-9 / f^2 meter/counts  (#5637), the actual displacement in the excited DOF should be about 10 pm level.
Therefore the excited displacements must be always in the linear ranges and also the amplitude in counts is reasonably smaller than the DAC range.
 

LOCKIN detection

The attached cartoon below shows how the LOCKIN system works for the MICH response measurement.
In the case of the PRCL response measurement, the setup is the same except that only PRM is shaken.
Here is some notes about the LOCKIN detection.
  • The LOCKIN oscillator excites ITMs differentially
    • In order to purely excites the MICH DOF, the actuation coefficients were precisely adjusted (#6398).
    • Currently ITMY has a gain of 1, and ITMX has a gain of -0.992 for the pure MICH excitation. Those numbers were put in the output matrix of the LOCKIN oscillator.
  • The demodulation phase of the LOCKIN system was adjusted to be -22 deg at the digital phase rotator.
    • This number maximizes the in-phase signals while the quadrature-phase signals give almost zero.
    • This number was adjusted when the simple MICH configuration was applied.
  • In the demodulations, the LO signals have amplitude of 100 counts to just make the demodulated signals readable numbers.

 

lockins_MICH.png

 

Calibration of the LOCKINs

  The calibration of the LOCKIN detectors is easy because all the processes takes place in the digital land, where we know all the parameters.
In this phase the goal is to calibrate the signals into counts / meter.
To calibrate the LOCKIN output signals, the following equation is used :
 
 [The obtained LOCKIN output in counts ] = H x ADOF x CLO x CEXC x 1/2  ,
 
 where H is the response of a sensor (e.g. AS55_I, AS55_Q and so on) against a particular DOF in unit of counts / m and this the quantity which we want to measure here,
ADOF is the actuator efficiency of the DOF at the excitation frequency in unit of m/counts,
CLO is the amplitude of the local oscillator signal for demodulating the sensor signals in unit of counts,
CEXC is the amplitude of the excitation signal in unit of counts,
the last 1/2 term comes from the fact there is a low pass filter in each demodulation path. 
Therefore once we measure the response of a sensor, dividing the obtained LOCKIN output by ADOF x CLO x CEXC x 1/2 gives the calibrated response in unit of counts/meter.
  ADOF are well known as they have been measured several times (#5637).
For the MICH actuator I assumed that AMICH = 2 x (ITMY response) since they are balanced through the actuation coefficients.
Note that a confirmation of this calibration has been done
when the configuration is in the simple Michelson, where we can easily estimate the response of a sensor by letting the MICH freely swing.
 

Calibration of the responses to watts/meter

  With the calibration process described above, we obtain the sensor responses in unit of counts/m.
 Then we need to do another calibration to make them into unit of W/m.
If we think about how the RFPD signal flows, we get the following gain chain.
 
[raw response in counts/m ] = Hopt x CADC x Ldemod x GWF x Ztrans x RPD
 
Hopt  is the optical gain at a sensor which we want to calibrate. It is in unit of W/m.
CADC  is the conversion factor of the ADCs and the value is CADC = 1638.4 counts/m because their resolution is 16 bit and the range is +/-20 V.
Ldemod is the conversion efficiency of the demodulation boards in unit of V/V. I used the values which Suresh measured yesterday (#6402).
GWF is the gain of the whitening filter in unit of V/V,
Ztrans is the transimpedance gain of an RFPD in unit of V/A and I used the values summarized in (the wiki),
and RPD is the responsivity of the photo diodes and I assumed RPD = 0.75 A/W for all the RFPDs.
 
Therefore the calibration can be done by dividing the raw response value by the entire gain chain of CADC x Ldemod x GWF x Ztrans x RPD.
 

Settings and parameters

  •  LSC RF demodulation phases
    •  AS55 = 17.05 deg (minimizing the PRCL sensitivity in the Q-phase)
    •  REFL11 = -41.05 deg (maximizing the PRCL sensitivity in the I-phase)
    • REFL33 = -25.85 deg (maximizing the PRCL sensitivity in the I-phase)
    • REFL55 = 4 deg (maximizing the PRCL sensitivity in the I-phase)
    • REFL165 = 39 deg (random number)
  •  Whitening filters
    • AS55 = 30 dB
    • REFL11 = 0 dB
    • REFL33 = 42 dB
    • REFL55 = 30 dB
    • REFL165 = 45 dB
  • MICH servo
    • AS55_Q for the sensor
    • G = -5 in the digital gain
    • FM2, FM3, FM5 and FM9 actiavted
    • UGF ~ 100 Hz
    • Feedback to ITMs differentially
  • PRCL servo
    • REFL33_I for the sensor
    • G = 1 in the digital gain
    • FM2, FM3, FM4, FM5 and FM9 activated
    • UGF ~ 100 Hz
    • Feedback to PRM

Quote from #6403

Tonight I measured the sensing matrix again but this time I recorded them as a function of time using the realtime LOCKINs in the LSC front end.

I will explain some more details about how I measured and calibrated the data in another elog entry.

  6406   Tue Mar 13 16:56:19 2012 kiwamuUpdateLSCevolution of the sensing matrix in PRMI as a function of time

Next steps:

  • Compare the obtained sensing matrix with an Optickle model. Particularly I am interested in the absolute strengths in watts/meter
  • Noise estimation of the REFL33_Q as a MICH sensor to see if this sensor is usable for holding MICH.

Quote from #6403

Tonight I measured the sensing matrix again but this time I recorded them as a function of time using the realtime LOCKINs in the LSC front end.

The attached plots are the responses (optical gains) of PRCL and MICH in watts / meter at various sensors in time series.

  6407   Tue Mar 13 19:14:40 2012 kiwamuUpdateLSCNoise estimatino in the REFL33Q as a MICH sensor

A feasibility study of the REFL33Q as a MICH sensor was coarsely performed from the point view of the noise performance.

The answer is that :

  the REFL33Q can be BARELY used as a MICH sensor in the PRMI configuration, but the noise level will be at only sub-nano meter level.

  Tonight I will try to use the REFL33Q to control the MICH DOF to see what happens.

 

(Background)

  I neeeeeeeed a 3f signal which is sensitive enough to hold the Michelson in the PRMI configuration so that I can test the single arm + PRMI configuration.
Based on the data I got in the sensing matrix measurement (#6403) I wanted to see how noises in the REFL33Q look like.
 

(Noise analysis)

  I did a coarse noise analysis for the REFL33Q signal as shown in the attached plot below while making some assumptions as follows.

  •  Optical gain for MICH = 0.8  W/m (#6403)
    • In the plot below, I plotted a unsuppressed MICH motion which had been measured the other day with a different sensor. This is for a comparison.
  •  Shot noise due to DC light on the REFL33 photo diode
    •  With a power of 5.0 mW (#6355)
    • Assume that the responsivity is 0.75 A/W, this DC light creates the shot noise in the photo current at a level of 35 pA/sqrtHz.
    • Then I estimated the contribution of this shot noise in terms of the MICH displacement by calibrating the number with the optical gain and responsivity.
    • It is estimated to be at 60 pm/sqrtHz
  • Dark current
    • I assumed that the dark current is 0.52 mA. (see the wiki)
    • In the same manner as that for the shot noise, the dark current is estimated to be at 20 pm/sqrtHz in terms of the displacement
  • Whitening filter input referred noise
    • I assumed that it is flat with a level of 54 nV/sqrtHz based on a rough measurement by looking at the spectrum of the LSC input signals.
    • The contribution was estimated by applying some gain corrections from the conversion efficiency of the demod board, transimpedance gain, responsivity and the optical gain.
    • This noise is currently the limiting factor over a frequency range from DC to 1 kHz.
  • ADC noise
    • I did the same thing as that for the whitening filter noise.
    • I assumed the noise level is at 6 uV/sqrtHz and it is flat (I know this not true particularly at mHz region the noise becomes bigger by some factors)
    • Then I applied the transfer function of the whitening filter to roll off the noise above 15 Hz.

 NB_REFL33.png

(Some thoughts)

  •   Obviously the limiting noises are that of ADC and the whitening filter.
    • These noise can be easily mitigated by installing an RF amplifier to amplify the RF signals from the REFL33Q RFPD.
    • Therefore this is not the real issue
  • The real issue is that the shot noise is already at a level of 60 pm/sqrtHz, and we can't suppress the MICH motion less than that.
    • In order to decrease it, one possibility is to increase the modulation depth. But it is already at the maximum.
    • If the REFL165 RFPD is healthy, it is supposed to give us a bigger MICH signal. But it didn't look healthy ... (#6403)
  6409   Wed Mar 14 03:34:44 2012 kiwamuUpdateSUSAdjustment of BS suspension output matrix : coupling from SIDE to POS

[Rana / Kiwamu]

 We put some elements in the BS output matrix to mitigate the actuator coupling from SIDE to POS.

As a result the degree of the coupling reduced by a factor of 2 or so.

Rana did the "Q of 5" test on the SIDE damping servo after putting the elements and set the gain to be 40.

 

The attached screen shot is the new elements that we put in the suspension output matrix.

Untitled.png

 

(How to)

  • Excite the SIDE motion by AWG at 3 Hz.
  • Monitor the POS signal in DTT
  • Try some numbers in the matrix elements until the peak at 3 Hz in the POS signal is minimized

Quote from #6369

The BS SIDE damping gain seemed too low. The gain had been 5 while the rest of the suspensions had gains of 90-500.

I increased the gain and set it to be 80.

 

I did the "Q of 5" test by kicking the BS SIDE motion to find the right gain value.

However there was a big cross coupling, which was most likely a coupling from the SIDE actuator to the POS motion.

Due to the cross coupling, the Q of 5 test didn't really show a nice ring down time series. I just put a gain of 80 to let the Q value sort of 5.

I think we should diagonalize the out matrices for all the suspensions at some point.

 

  6410   Wed Mar 14 04:03:37 2012 kiwamuUpdateIOOPZT1 and associate extra works

As the PZT1 has not been functional, I have been aligning the Y arm to the input beam instead of aligning the beam to the Y arm.

It turned out that this procedure leads to two extra works everytime after alignments of the Y arm:

  1. The Y green beam must be always aligned to the Y arm
    • The amount of the misalignment was found to be relatively big compared with how it used to be.
  2. The PSL beat note setup must be always realigned because the Y green path is determined by the orientation of the Y arm.
    • In the past I didn't often realign the beat note path, but currently it needs to be pay more attentions.

Sad ..

Quote from #6357

   The polarity for controlling the PZT1 PITCH seems to have flipped for some reason.

 

  6411   Wed Mar 14 04:19:51 2012 kiwamuUpdateLSCREFL33Q for MICH control : not good

 I tried the REFL33Q for controlling MICH in the PRMI configuration (#6407)

The result was --

 It was barely able to lock MICH in a short moment but didn't stay locked for more than 10 sec. Not good.

 

The attached screenshot below shows a moment when the PRMI was locked with REFL33I and REFL33Q for PRCL and MICH respectively.
Apparently the lock was destroyed after 10 sec or so and it was locked again.
Untitled.png

 

(Tricks)

 At the beginning I tried minimizing the PRCL signal in the Q phase by rotating the demodulation phase because the PRCL signal was always huge.
However it turned out that the rotation of the demodulation phase didn't completely eliminate the PRCL signal for some reason.
 
This could be some kind of imbalance in the electronics or somewhere between the I and Q signal paths.
So instead, I tried blending the I and Q signals by a linear combination through the LSC input matrix.
Then I was able to eliminate the PRCL signal.
I put a gain of -0.1 for the I signal and 1 for the Q signal to get the good blend when the demodulation phase was at -17.05 deg.
  6412   Wed Mar 14 05:26:39 2012 interferomter tack forceUpdateGeneraldaytime tasks

The following tasks need to be done in the daytime tomorrow.

  • Hook up the DC output of the Y green BBPD on the PSL table to an ADC channel (Jamie / Steve)
  • Install fancy suspension matrices on PRM and ITMX [#6365] (Jenne)
  • Check if the REFL165 RFPD is healthy or not (Suresh / Koji)
    • According to a simulation the REFL165 demod signal should show similar amount of the signal to that of REFL33.
    • But right now it is showing super tiny signals [#6403]
  6413   Wed Mar 14 10:06:26 2012 steveUpdateGreen Lockingdichroic mirror quotes

Dichroic mirror quotes are in the wiki.

ATF is pricy.

We got a good price from Laseroptik, but the wedges are 5 arcminutes. The fused silica grade is 0F, meaning the  homogeneity is 5 ppm instead of 1ppm.  I requested an other large wedge quote on the substrates.We may have to get substrates from somebody else and ship it to Germany

MLT quote is outrageously high

REO is not interested in this low volume job.

 

  6414   Wed Mar 14 13:16:50 2012 kiwamuUpdateLSCA correction on Noise estimatino in the REFL33Q

A correction on the previous elog about the REFL33Q noise:

 Rana pointed out that the whitening filter's input referred noise should not be such high (I have estimated it to be at 54 nV/sqrtHz).
In fact the measurement was done in a condition where no laser is on the photo diode by closing the mechanical shutter at the PSL table.
Therefore the noise I called "whitening filter input referred noise" includes the voltage noise from the RFPD and it could have such a noise level.
So the noise curve drawn in the plot should be called "whitening filter + RFPD electronics noise".

Quote from #6407

A feasibility study of the REFL33Q as a MICH sensor was coarsely performed from the point view of the noise performance.

  • Whitening filter input referred noise
    • I assumed that it is flat with a level of 54 nV/sqrtHz based on a rough measurement by looking at the spectrum of the LSC input signals.
    • The contribution was estimated by applying some gain corrections from the conversion efficiency of the demod board, transimpedance gain, responsivity and the optical gain.
    • This noise is currently the limiting factor over a frequency range from DC to 1 kHz.

 

  6416   Wed Mar 14 14:09:01 2012 interferomter tack forceUpdateGeneraldaytime tasks

Quote:

The following tasks need to be done in the daytime tomorrow.

  • Hook up the DC output of the Y green BBPD on the PSL table to an ADC channel (Jamie / Steve)
  • Install fancy suspension matrices on PRM and ITMX [#6365] (Jenne)
  • Check if the REFL165 RFPD is healthy or not (Suresh / Koji)
    • According to a simulation the REFL165 demod signal should show similar amount of the signal to that of REFL33.
    • But right now it is showing super tiny signals [#6403]

 For ITMX, I used the values from the conlog:

2011/08/12,20:10:12 utc 'C1:SUS[-_]ITMX[-_]INMATRIX'
These are the latest values in the conlog that aren't the basic matricies.  Even though we did a round of diagonalization in Sept, and the 
matricies are saved in a .mat file, it doesn't look like we used the ITMX matrix from that time.

For PRM, I used the matricies that were saved in InputMatricies_16Sept2011.mat, in the peakFit folder, since I couldn't find anything in the Conlog other than the basic matricies.

 

UPDATE:  I didn't actually count the number of oscillations until the optics were damped, so I don't have an actual number for the Q, but I feel good about the damping, after having kicked POS of both ITMX and PRM and watching the sensors.

  6417   Wed Mar 14 16:33:20 2012 keikoUpdateLSCRAM simulation / RAM pollution plot

In the last post, I showed that SRCL element in the MICH sensor (AS55I-mich) is chaned 1% due to RAM.

Here I calculated how is this 1% residual in MICH sensor (AS55 I-mich) shown in MICH sensitivity. The senario is:

(1) we assume we are canceling SRCL in MICH by feed forward first (original matrix (2,3) element).

(2) SRCL in MICH (matrix(2,3) is changed 1% due to RAM, but you keep the same feed forward with the same feedforward gain

(3) You get 1% SRCL residual motion in MICH sensor. This motion depends on how SRCL is quiet/loud. The assumed level is

Pollution level = SRCL shot noise level in SRCL sensor  x  SRCL closed loop TF  x  1% residual .... the following plot.

 

 

AS sensor = AS55I-mich  --- SN level 2.4e-11 W/rtHz ------- MICH SN level 6e-17 m/rtHz

SRCL sensor = AS55 I-SRCL --- SN level 2e-11 W/rtHz ---  SRCL SN level 5e-14 m/rtHz

 

 

RAMexampleplot.png

 

 

Quote:

Adding some more results with more realistic RAM level assumption.

(4) With 0.1% RAM mod index of PM (normalized by (1) )

  PRCL MICH SRCL
REFL11I 0.99999 -0.001807 -0.000148
AS 55 Im 0.000822 1.000002 0.000475
AS 55 Is 1.068342 906.968167 1.00559
 

 

 

 

 

  6418   Wed Mar 14 16:39:02 2012 SureshUpdateGeneralREFL165 signal was not reaching demod board : Fixed

Quote:

The following tasks need to be done in the daytime tomorrow.

  • Hook up the DC output of the Y green BBPD on the PSL table to an ADC channel (Jamie / Steve)
  • Install fancy suspension matrices on PRM and ITMX [#6365] (Jenne)
  • Check if the REFL165 RFPD is healthy or not (Suresh / Koji)
    • According to a simulation the REFL165 demod signal should show similar amount of the signal to that of REFL33.
    • But right now it is showing super tiny signals [#6403]

 The REFL165 RF output was not reaching the Demod board.  The RF cable was disconnected.  I fixed that and then I put in a RF signal at 165MHz , 1.66 mVrms at the test input  (100Hz off set from the 165MHz LO) and saw that the 100 Hz demodulated signal was visible in the dataviewer. 

Test_CDS_Calibration.png

 

Will complete the Optical RF power -> CDS counts calibration tomorrow morning. 

  6419   Wed Mar 14 21:01:36 2012 keikoUpdateLSCevolution of the sensing matrix in PRMI as a function of time

This is the simulated signals to compare with the original post #6403

 

 

PRMI configuration, PRCL signal

[W/m] Simulation Measured
REFL11 575440

 

~10000

REFL33 4571 ~50
REFL55 288400 ~5000
REFL165 891 NA
AS55 71 70

 

PRMI configuration, MICH signal

[W/m] Simulation Measured
REFL11 2290

 

~600

REFL33 36 ~4
REFL55 5623 ~200
REFL165 17 NA
AS55 6456 ~200
 

Simulated DC REFL power is 9mW (before the attenuator). AS DC is 0.3mW.

They don't agree. I suspect the PR gain for the SBs are somehow different. It is about 40 (or a bit less) in the simulation for 11MHz.

 

 

 

 

  6420   Wed Mar 14 23:02:09 2012 KojiUpdateLSCLocking activity

Kiwamu and Koji

The target is to realize DRMI or PRMI + one arm with ALS.

The focus of the night is to achive stable lock of the PRMI (SB resonant) with 3f signals.
Particularly, REFL165 is back now, we are aiming to see if any of the 165 signals is useful.

We made a comparison between  REFL33Q/REFL165Q/AS55Q to find any good source of MICH.
However, none of them showed a reasonable shape of the spectra. They don't have reasonable coherence between them.

Nonetheless, we have tried to lock the IFO with those REFL signals. But any of them were useful to keep the PRMI (SB resonant).
The only kind of stable signal for MICH was AS55Q as we could keep the PRMI locked.

  6423   Fri Mar 16 06:17:56 2012 SureshUpdateElectronicsREFL165 calibration : measurements

 

These are the measurements for estimating the amplitude of the signal recorded in the CDS when a known amount of modulated light is incident on the photodiode. 

I mounted the PD characterisation setup onto a small breadboard which could then be placed close AP table.  I then placed position markers for REFL165 on the AP table before moving it onto my small breadboard.  The AM laser was driven by an RF function generator (Fluke 6061A) at a frequency of 165.98866 MHz, which is 102 Hz offset from the 165MHz LO.  The power level was set at -45dBm.  This power level was chosen since anything higher would have saturated the AntiAliasing  Whitening Filters.  The counts in the CDS were converted to voltage using the ADC resolution = 20V per 2^16 counts.

  

  RF source RF power to AM laser 1611 PD 1611 PD REFL165 REFL165 CDS CDS
  power set (dBm) Actual power out (dBm) DC (V) RF out (dBm) DC (mV) RF out (dBm) Amplitude (V)   102 Hz Amplitude (V) 102 Hz
                 
1  -45  -50.6  -2.5 -58.9  10  -37.4  0.171 0.172
2  -48  -53.5  -2.5 -62.1  10  -40.3  0.122  0.121
3  -51  -56.5  -2.5 -65.0  10  -43.1  0.085  0.085

    

 When the 166MHz power is decreased by a factor of 2 the amplitude of 102Hz wave recorded in CDS goes down by sqrt(2) as expected.   The RF AM power incident on the REFL165 was estimated to be 0.011mW(rms)  (case #1 in the above table)  using the DC power ratio and using the transimpedance of the 1611 BBPD to be 700 Ohms.  This produces a 171 mV amplitude wave at 102 Hz.  I then stepped down the power by factor of 2 and repeated the measurement. 

(These numbers however are not agreeing with the power incident on REFL165 if we assume its transimpedance to be 12500.  It will take a bit more effort to make all the numbers agree.  Will try again tomorrow)

Here is a picture of the small black breadboard on which I have put together the PD characterisation setup.  It would be great if we can retain this portable set up as it is, since we keep reusing it every couple of weeks.  It would be convenient if we can fiber couple the path to the PD under test with a 2m long fiber.  Then we will not have to remove the PD from the optical table while testing it.

IMG_0552.JPG

 

  6424   Fri Mar 16 10:37:52 2012 JenneUpdateElectronicsJenne Laser

Quote:

Here is a picture of the small black breadboard on which I have put together the PD characterisation setup.  It would be great if we can retain this portable set up as it is, since we keep reusing it every couple of weeks.  It would be convenient if we can fiber couple the path to the PD under test with a 2m long fiber.  Then we will not have to remove the PD from the optical table while testing it. 

 This is totally sweet Suresh!  I don't remember how much more fiber is coiled up under the plate that has the "Jenne Laser" label, but there's a reasonable amount.  It's not 2m, but maybe we can just extend the blue snakey thing some?

  6425   Fri Mar 16 16:01:53 2012 ranaUpdateElectronicsREFL165 calibration : measurements

 To characterize the RF V to counts we need to know the state of the whitening filter board. Was the filter on or off ? What was the value of the whitening gain slider?

  6426   Fri Mar 16 16:03:03 2012 kiwamuUpdateIOOMC alignment servo : put some offsets in the TRANS QPD signal

The MC alignment servo wasn't great in the last 1 hour or so as it kept disturbing the MC lock. It was found to be due to some offsets in the MC trans QPD signals.

I put some values to cancel the offsets and then the lock became stable.

This is a first aid. So we need to take a closer look at the QPD signals and also probably the spot position on the QPD.

 


The symptom was that every time the alignment servo was engaged, at the beginning the amount of the transmitted light went to 27000 counts, which is good.

However, then the amount of the transmitted light slowly decreased in a time scale of ~ 20 sec or so, ending up with destruction of the MC lock.

According to the time scale I suspected that the servos using the trans QPD signals were doing something bad because their control width had been designed to be slow and slower than the rest of the servo loops.

I switched off the servos, called C1:IOO-TRANS_PIT and C1:IOO-TRANS_YAW and found the MC stayed locked stably with 27000 counts of the transmitted light.

Leaving the trans QPD servos off, I zeroed the offsets and then switched them on. It worked.

 

The values below are the current offset that I put.

                C1:IOO-MC2_TRANS_PIT_OFFSET = -0.115203
                C1:IOO-MC2_TRANS_YAW_OFFSET = -0.0323576
 

  6427   Sun Mar 18 00:29:24 2012 DenUpdatePEMsts-2

I've turned off the power of the STS-2 readout box as it provides outputs with ~10 Volts DC offset! AA filter box works in the range -2 +2 Volts, so we do not have any useful information anyway. I'll adjust the mass positions in the seismometer.

  6428   Mon Mar 19 21:25:31 2012 SureshUpdateElectronicsREFL165 calibration : measurements

Quote:

 To characterize the RF V to counts we need to know the state of the whitening filter board. Was the filter on or off ? What was the value of the whitening gain slider?

 The filter was ON and the whiterning filter gain was 45dB

 

  6429   Tue Mar 20 09:59:01 2012 steveUpdateIOOLaser tripped off

Today is janitor day. It still does not explain why the 2W Innolight tripped off about an hour ago. All back to normal.

.......................................................I asked Keven later, he admitted hitting the emergency shut off next to the chemical storage cabinet.

ELOG V3.1.3-