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ID Date Author Type Category Subject
5544   Mon Sep 26 14:21:07 2011 kiwamuUpdateSUSITMX ULSEN shows jumps

 Quote from #5534 As a suspension test I am leaving all of the suspensions restored and damped with OSEMS but without oplevs

According to the spectra, all of the suspensions had been damped with the OSEMs. The peaks around 1Hz are reasonably suppressed.

However the spectra from ITMX showed a noise floor at very high level. This is because of strange jumps in the signal of the UL shadow sensor.

I will check some analog circuits for the UL sensor.

Here is the spectra of the ITMX shadow sensors taken during the damping test (#5534)- -

The UL sensor shows a unacceptable amount of noise.

Additionally I checked the time series of the ITMX shadow sensors and found ONLY the UL sensor frequently showed strange jumps in data.

Here is an example of the time series showing a jump ONLY in the UL sensor.

It is possible that the jumps are coming from some circuits, since the rest of the sensors (including the oplevs) don't detect the same jump.

5546   Mon Sep 26 15:54:46 2011 kiwamuUpdateSUSITMX ULSEN shows jumps

Currently the damping of the ITMX suspension is intentionally disabled for the noise investigation.

 Quote from #5544 However the spectra from ITMX showed a noise floor at very high level. This is because of strange jumps in the signal of the UL shadow sensor. I will check some analog circuits for the UL sensor.

5547   Mon Sep 26 16:42:08 2011 kiwamuUpdateSUSITMX ULSEN : fixed

The issue on the ITMX UL sensor has been fixed. It was because of a loose connection in the sensor signal path.

After the fix, the sensor responses completely changed and the suspension became unable to be damped with the new matrix.

At the moment the ITMX suspension is damped by the default input matrix.

we should do the free swinging test once again.

(details)

The loose connection was found on the rear side of the 1X5 rack.

There is an adapter card on the rear side, where the driver and sensor signals are combined into a single cable.

I pushed the sensor cable (bottom right in the picture) and the noise disappeared.

Note that I changed the labels on the adapter cards from the old X/Y convention to the new one.

After fixing the loose cable the ITMX suspension became unable to be damped.

So I put the input matrix back to the default and it immediately started damping happily. It means our new matrix is not valid any more.

Here is the latest noise spectra of the ITMX sensors damped with the default input matrix.

As usual all of them are limited by the ADC noise above 20 Hz. (ADC noise is plotted in purple curve)

During the work I also pushed not only ITMX ones but also the cable for the rest of the optics in the adapter cards.

Then PRM became unable to be damped, so it implies the PRM suspension also used to be the same situation.

The input matrix of PRM has been also back to the default.

 Quote from #5546 Currently the damping of the ITMX suspension is intentionally disabled for the noise investigation.

5553   Tue Sep 27 04:13:22 2011 kiwamuUpdateLSCtonight's locking activity

The lock of PRMI wasn't so robust although it could stay locked for more than 10 minutes.

There have been 2-3Hz spikes in everywhere. It needs to be investigated.

(to do)

+ Diagnosis on the suspensions.

+ Check the beam centering on the RFPDs.

+ Check the f2a filters on PRM and BS.

+ Health check of the suspensions by locking some cavities and measuring the noise spectra for comparison.

+ Trying to use another signal port other than AS55.

(Spikes)

The attached picture below is an example of the REFLDC and POXDC signals in time series.

This was when PRCL and MICH were locked by REFL33_I and AS55_Q respectively.

Note that when PRMI is unlocked, REFLDC goes to ~ 5000 counts and POXDC goes within ADC noise of ~ 1 counts.

According to the POP camera it looked like something was oscillating in the YAW direction which coincided with the spikes.

I tried finding any suspicious angular motions in the ITMs, BS and PRM olevs, but none of them showed the 2-3 Hz feature.

5561   Wed Sep 28 02:42:04 2011 kiwamuUpdateCDSsome DAQ channel lost in c1sus : fb, c1sus and c1pem restarted

Somehow some DAQ channels for C1SUS have disappeared from the DAQ channel list.

Indeed there are only a few DAQ channels listed in the C1SUS.ini file.

I ran the activateDQ.py and restarted daqd.

Everything looks okay.  C1SUS and C1PEM were restarted because they became frozen.

5574   Thu Sep 29 03:43:20 2011 kiwamuUpdateASCwrong channel assignment on IPPOS

The channels for IPPOS had been assigned in a wrong way.

Because of this, C1:ASC-IP_POS_X_Calc corresponds to the actual vertical motion and C1:ASC-IP_POS_Y_Calc is for the horizontal motion.

We should fix the database file to get the correct vertical/horizontal corrdinate.

5578   Fri Sep 30 01:18:39 2011 kiwamuUpdateASCC1ASS : status update

Now the C1ASS servos are working fine.

However at the end of the scripts sometimes it changes the DC force (e.g. C1:SUS-ITMX_PIT_COMM and so on) by a wrong amount.

So for this bug, it misaligns the suspensions a lot. I will take a look at the script tomorrow.

 Quote from #5543 However then I found the ASS_Xarm servo was not healthy.

5579   Fri Sep 30 02:56:56 2011 kiwamuUpdateCDSC1IOO.ini and C1LSC.ini files reverted

[Suresh/Kiwamu]

We found that the C1LSC.ini and C1IOO.ini file had been refreshed and there were a few recorded channels in the files.

So we manually recovered C1LSC.ini file using the daqconfig GUI screen.

For the C1IOO.ini file we simply replaced it by the archived one which had been saved in 22nd of September.

Then we restarted daqd.

5580   Fri Sep 30 03:14:18 2011 kiwamuUpdateCDSsuspension became crazy : c1sus rebooted

 Quote from #5579 Then we restarted daqd.

[Suresh / Kiwamu]

The c1lsc and c1sus machine were rebooted.

- - (CDS troubles)

After we restarted daqd and pressed some DAQ RELOAD buttons the c1lsc machine crashed.

The machine didn't respond to ssh, so the machine was physically rebooted by pressing the reset button.

Then we found all the realtime processes on the c1sus machine became frozen, so we restarted them by sshing and typing the start scripts.

However after that, the vertex suspensions became undamped, even though we did the burt restore correctly.

This symptom was exactly the same as Jenne reported (#5571).

We tried the same technique as Jenne did ; hardware reboot of the c1sus machine. Then everything became okay.

The burt restore was done for c1lsc, c1asc, c1sus and c1mcs.

- - (ITMX trouble)

During the trial of damping recovery, the ITMX mirror seemed stacked to an OSEM. The UL readout became zero and the rest of them became full range.

Eventually introducing a small offset in C1:SUS-ITMX_YAW_COMM released the mirror. The amount of the offset we introduced was about +1.

5582   Fri Sep 30 05:35:42 2011 kiwamuUpdateLSClength fluctuations in MICH and PRCL

The MICH and PRCL motions have been measured in some different configurations.

According to the measurements :

+ PRCL is always noisier than MICH.

+ MICH motion becomes noisier when the configuration is Power-Recycled Michelson (PRMI).

The next actions are :

+ check the ASPD

+ check the demodulation phases

+ try different RFPDs to lock MICH

(Motivation)
The lock of PRMI have been unstable for some reason.
One thing we wanted to check was the length fluctuations in MICH and PRCL.

(Measurement)
Four kinds of configuration were applied.
(1) Power-recycled ITMX (PR-ITMX) locked with REFL33_I, acting on PRM.
(2) Power-recycled ITMY (PR-ITMY) locked with REFL33_I, acting on PRM.
(3) Michelson locked with AS55_Q, acting on BS.
(4) Power-recycled Michelson locked with REFL33_I and AS55_Q, acting on PRM and BS.

In each configuration the spectrum of the length control signal was measured.
With the measured spectra the length motions were estimated by simply multiplying the actuator transfer function.
Therefore the resultant spectra are valid below the UGFs which were at about 200 Hz.
The BS and PRM actuator responses had been well-measured at AC (50 - 1000 Hz)
For the low frequency responses they were assumed to have the resonances at 1 Hz with Q of 5.

(Results)
The below plot shows the length noise spectra of four different configurations.
There are two things which we can easily notice from the plot.
+ PRCL (including the usual PRCL and PR-ITMs) is always noisier than MICH.
+ MICH became noisier when the power recycling was applied.
In addition to them, the MICH noise spectrum tended to have higher 3 Hz bump as the alignment gets improved.
In fact everytime when we tried to perfectly align PRMI it eventually unlocked.
I am suspecting that something funny (or stupid) is going on with the MICH control rather than the PRCL control.

(Notes)
BS actuator = 2.190150e-08 / f2
PRM actuator = 2.022459e-08 /  f2
5583   Fri Sep 30 06:25:20 2011 kiwamuUpdateLSCCalbiration of BS, ITMs and PRM actuators
The AC responses of the BS, ITMs and PRM actuators have been calibrated.

(Background)
To perform some interferometric works such as #5582, the actuator responses must be measured.

(Results)
BS = 2.190e-08 / f2     [m/counts]
ITMX  = 4.913e-09 / f2   [m/counts]
ITMY  = 4.832e-09 / f2   [m/counts]
PRM   = 2.022e-08 / f2  [m/counts]

(Measurement)
The same technique as I reported some times ago (#4721) were used for measuring the BS and ITMs actuators.
In order to measure the PRM actuator, power-recycled ITMY (PR-ITMY) was locked and the same measurement was applied.
The sensor response of PR-ITMY was calibrated by exciting the ITMY actuator since the response of the ITMY had been already measured.
5586   Fri Sep 30 16:17:10 2011 kiwamuUpdateGreen Lockingthings to be done for the Yarm green lock

Thank you for the summary.

I think now you are getting into a phase where you should start doing some quantitative and careful checks.

1. Calculate how much light will be reflected from the cavity if the alignment is perfect.

2. Investigate where those kHz oscillations are coming from.

3. Estimate how much the 1.1 kHz corner frequency in LPF will reduce the phase margin around 10 kHz.

4. Calculate the estimated amplitude of the PDH signal.

5. Compute how big the gain of the PDH box should be.

 Quote from #5585 This is a kind of summary of what I have worked on this week.  DC level of green PD when light resonates 75%                     --> Not sure if this alignment is good enough The PDH error signal was covered with oscillations of 3.3 kHz, 7.1 kHz and 35 kHz. Designed and build a new LPF: second order, cut of frequency of 1.1 kHz (this is just the design value, haven't measured that so far) Signal-to-noise ratio (SNR) could be improved to values between 7.8 and 11.1 (old SNR was 5 to 7)

5588   Fri Sep 30 17:40:03 2011 kiwamuUpdateIOOAM / PM ratio

[Mirko / Kiwamu]

We have reviewed the AM issue and confirmed the ratio of AM vs. PM had been about 6 x103.

The ratio sounds reasonably big, but in reality we still have some amount of offsets in the LSC demod signals.

Next week, Mirko will estimate the effect from a mismatch in the MC absolute length and the modulation frequency.

(Details)

Please correct us if something is wrong in the calculations.

According to the measurement done by Keiko (#5502):

DC = 5.2 V

AM @ 11 and 55 MHz = - 56 dBm = 0.35 mV (in 50 Ohm system)

Therefore the intensity modulation is 0.35 mV / 5.2 V = 6.7 x 10-5

Since the AM index is half of the intensity modulation index, our AM index is now about 3.4 x 10-5

According to Mirko's OSA measurement, the PM index have been about 0.2.

As a result,  PM/AM = 6 x 103

 Quote from #5502 Measured values; * DC power = 5.2V which is assumed to be 0.74mW according to the PDA255 manual. *AM_f1 and AM_f2 power = -55.9 dBm = 2.5 * 10^(-9) W.

5589   Fri Sep 30 18:06:24 2011 kiwamuSummaryIOOPZTs straing guage

5593   Sat Oct 1 22:53:49 2011 kiwamuSummaryGeneralRecovery from the power shutdown : lockable

Found the Marconi for the 11 MHz source had been reset to its default.

=> reset the parameters. f = 11.065910 MHz (see #5530) amp = 13 dBm.

Interferometer became lockable. I checked the X/Y arm lock, and MICH lock, they all are fine.

5594   Sun Oct 2 02:21:27 2011 kiwamuUpdateSUSfree swinging test once more

The following optics were kicked: MC1 MC2 MC3 ETMX ETMY ITMX ITMY PRM SRM BS Sun Oct  2 02:13:40 PDT 2011 1001582036

They will automatically get back after 5 hours.

5595   Sun Oct 2 02:33:32 2011 kiwamuUpdateLSCsomething funny with AS55

Just a quick report.

The AS55 signal contains more noise than the REFL signals.

Why ? Is this the reason of the instability in PRMI ?

I locked the Power-Precycled ITMY with REFL33.

As shown in the plot above, I compared the in-loop signal (REFL33) and out-of-loop signals (REFL11 and AS55).

All the signals are calibrated into the displacements of the PR-ITMY cavity by injecting a calibration peak at 283 Hz through the actuator of PRM.

AS55 (blue curve) showed a structure around 3 Hz and higher flat noise below 1 Hz.

 Quote from #5582 I am suspecting that something funny (or stupid) is going on with the MICH control rather than the PRCL control.

5597   Sun Oct 2 18:33:36 2011 kiwamuUpdateSUSinversion of the input matrix on ETMX, ITMX and PRM

The input matrices of ETMX, ITMX and PRM have been newly inverted.

Those were the ones having some troubles (see #5444, #5547).

After a coarse adjustment of the damping Q factors, they look damping happily.

 optic spectra inverted matrix BADNESS ETMX pit     yaw     pos     side    butt UL    0.848   0.108   1.578   0.431   1.025  UR    0.182  -1.892   1.841  -0.128  -1.172  LR   -1.818  -1.948   0.422  -0.122   0.939  LL   -1.152   0.052   0.159   0.438  -0.864  SD    1.756  -3.794  -0.787   1.000  -0.132 5.37028 ITMX pit     yaw     pos     side    butt UL    0.510   0.584   1.228   0.458   0.203  UR    0.783  -1.350   0.348  -0.050   0.555  LR   -1.217   0.065   0.772   0.264   0.312  LL   -1.490   2.000   1.652   0.772  -2.930  SD   -0.635   0.853  -1.799   1.000  -1.597 7.5125 PRM pit     yaw     pos     side    butt UL    0.695   1.422   1.774  -0.333   0.954  UR    1.291  -0.578   0.674  -0.068  -0.939  LR   -0.709  -1.022   0.226   0.014   0.867  LL   -1.305   0.978   1.326  -0.251  -1.240  SD    0.392  -0.437  -0.500   1.000   0.420 5.09674

(some notes)

Before running the peakFit scripts, I woke up the nds2 sever process on Mafalda because it hasn't been recovered from the power outage.

To start the nds2 process I followed the instruction by Jamie (#5094).

Then I started requesting the data of the last night's free swinging test (#5594)

However the NDS2_GetData command failed everytime when data with long duration were requested.

It maybe because some of the data are missing in sometimes, but I haven't seriously checked the data stored in fb.

So for the reason, I had to use a short duration of 1200 sec (default is 3600 sec). That's why spectra look noisier than usual.

5598   Mon Oct 3 04:43:03 2011 kiwamuUpdateLSCsideband-resonance PRMI locked

My goal of today was to lock PRMI without using AS55 and it is 50% successful.

The sideband-resonance PRMI (SB-PRMI) was locked with REFL33_I and REFL55_Q for the PRCL and MICH control respectively.

The carrier-resonance PRMI wasn't able to be locked without AS55.

(it looked no clean MICH signals at the REFL ports.)

(Motivation)

The motivation of not to use AS55 came from the suspicion that AS55 was injecting some noise into MICH (#5595).

So I wanted to try another RFPD to see if it helps the stability or not.

(locking activity)

The lock of SB-PRMI was quite stable so that it stayed locked more than 30 minutes (it ended because I turned off the servos.)

Then I briefly tried DRMI while PRCL and MICH kept locked by the same control loops, namely REFL33_I and REFL55_Q.

The lock of MICH and PRCL looked reasonably robust against the SRCL fringes, but wasn't able to find a good signal for SRCL.

I think I am going to try locking DRMI tomorrow.

- - settings

Demod phase for REFL55 = -45.3 deg

Demod phase for REFL33 = -14.5 deg

Whitening gain for REFL55 = 4 (12 dB)

Whitening gain for REFL33 = 10 (30 dB)

MICH gain = 100

PRCL gain = 8

(misc.)

+ I removed an iris on the ITMY table because it was in the way of POY. See the picture below.

+ I found that burtrestore for the ETMX DC coil forces were not functional.

=> currently ETMX's "restore" and "mislalign" buttons on the C1IFO_ALIGN screen are not working.

=> According to the error messages, something seemed wrong on c1auxex, which is a slow machine controlling the DC force.

5605   Mon Oct 3 17:57:12 2011 kiwamuUpdateASCIPPOS fixed

The input matrix of IPPOS were fixed so that the horizaontal motion correctly shows up in X and the vertial is Y.

(what I did)

+ The data base file, QPD.db, were edited.

QPD.db is a part of the c1isxaux slow machine and it determines the input matrix for deriving the X/Y signals from each quadrant element.

+ The previous input matrix was :

X = (SEG1 + SEG4) - (SEG2 + SEG3)

Y = (SEG1 + SEG2) - (SEG3 + SEG4)

+ The new matrix which I set is :

X = (SEG1 + SEG2) - (SEG3 + SEG4)

Y = (SEG1 + SEG4) - (SEG2 + SEG3)

The new matrix is a just swap of the previous X and Y.

+ Then c1isxaux was rebooted by :

telnet  c1iscaux

reboot

+ The I did the burt restore it to this morning.

 Quote from #5574 The channels for IPPOS had been assigned in a wrong way.

5607   Mon Oct 3 20:47:51 2011 kiwamuUpdateCDSc1lsc and c1sus didn't run

[Mirko / Jenne / Kiwamu]

Just a quick update. All the realtime processes on the c1lsc and c1sus machine didn't run at all.

Somehow the c1xxxfe.ko kernel module, where xxx is x04, x02, lsc, ass, sus, mcs, pem and rfm failed to be insmod.

The timing indicators on the c1lsc and c1sus machine are saying NO SYNC.

- According to log files (target/c1lsc/logs/log.txt)

insmod: error inserting '/opt/rtcds/caltech/c1/target/c1lsc/bin/c1lscfe.ko': -1 Unknown symbol in module

- dmesg on c1lsc (c1sus also dumps the same error message):

[   45.831507] DXH Adapter 0 : sci_map_segment - Failed to map segment - error=0x40000d01
[   45.833006] c1x04: DIS segment mapping status 1073745153

DXH dapter is a part of the Dolphine connections.

When a realtime codes is waking up, the code checks the Dolphin connections.

The checking procedure is defined by dolphin.c (/src/fe/doplhin.c).

According to a printk sentence in dolphin.c the second error message listed above will return status "0" if everything is fine.

The first error above is an error vector from a special dolphin's function called sci_map_segment, which is called in dolphin.c.

So something failed in this sci_map_segment function and is preventing the realtime code from waking up.

Note that sci_map_segment is defined in genif.h and genif.c which reside in /opt/srcdis/src/IRM_DSX/drv/src.

5609   Mon Oct 3 23:52:49 2011 kiwamuUpdateCDSsome more tests for the Dolphin

[Koji / Kiwamu]

We did several tests to figure out what could be a source of the computer issue.

The Dolphin switch box looks suspicious, but not 100% sure.

(what we did)

+ Removed the pciRfm sentence from the c1x04 model to disable the Dolphin connection in the software.

+ Found no difference in the Makefile, which is supposed to comment out the Dolphin connection sentences.

==> So we had to edit the Makefile by ourselves

+ Did a hand-comilpe by editing the Makefile and running a make command.

+ Restarted the c1x04 process and it ran wihtout problems.

==> the Dolphin connection was somehow preventing the c1x04 process from runnning.

+  Unplugged the Dolphin cables on the back side of the Dolphin box and re-plug them to other ports.

==> didn't improve the issue.

+ During those tests, c1lsc frequently became frozen. We disabled the automatic-start of c1lsc, c1ass, c1oaf by editting rtsystab.

==> after the test we reverted it.

+ We reverted all the things to the previous configuration.

5618   Tue Oct 4 19:31:17 2011 kiwamuUpdateSUSPRM and BS oplev laser died

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

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

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

5621   Wed Oct 5 14:18:09 2011 kiwamuUpdateCDSsome DAQ channel lost in c1sus : fb, c1sus and c1pem restarted

I found again the ini files had been refreshed.

I ran the activateDQ.py script (link to the script wiki page) and restarted the daqd process on fb.

The activateDQ.py script should be included into the recompile or rebuild scripts so that we don't have to run the script everytime by hands.

I am going to add this topic on the CDS todo list (wiki page).

 Quote from #5561 Somehow some DAQ channels for C1SUS have disappeared from the DAQ channel list.

5624   Thu Oct 6 05:18:20 2011 kiwamuUpdateLSCNoise in AS55 was from clipping : fixed

It turned out the noise in AS55 was due to a clipping.  After fixing the clipping the noise successfully went down.

I was going to briefly check the clipping and go ahead locking DRMI, but for some reason I couldn't stop myself from working on this issue.

Here is a plot of the noise spectra taken before and after fixing the clipping.

The configuration of this measurement is exactly the same as that I did before (#5595)

(what I did)

+ Locked power-recycled ITMY so that the AS beam is bright enough to work with.

+ Shook BS at 1 Hz in the YAW direction

+ Looked around the AP table with an IR viewer and searched for a clipping moving at 1Hz.

+ Found the first lens in the AS beam path has clipped the beam at the upper side. A tiny portion of the beam was clipped.

+ Corrected the beam height to 4 inch by steering the very first mirror.

+ Raised the height of the lens because it was about 3.5 inch or so.

+ Found the lens had a scratch (~1 mm size ) at 1 cm blow the center on the surface.

=> I tried finding a spare 2 inch lens with a long focul length, but I couldn't find it,

So I left the lens as it is, but we should buy some 2 inch lenses just in case like this.

+ Replaced the 1 inch beam splitter by 2-inch 99% BS so that most of the light goes into the RFPD and a little bit goes into the camera.

 Quote from #5595 The AS55 signal contains more noise than the REFL signals.

5627   Fri Oct 7 04:42:24 2011 kiwamuUpdateLSCDRMI locked and some plans

DRMI has been locked using the same RFPD selection as the old days (i.e. AS55_I, AS55_Q and REFL_I).(#4760)

But remember : this is just a beginning of several measurements and tests to characterize the central part.

Here is a list of the measurements and actions :

- 3f locking related

+ Listing up the necessary RFPDs and their installations.

+ Calibration of the SRM actuator  => this is necessary to convert the sensing matrix into unit of [counts/m] or [W/m].

+ Measurement of the sensing matrix => check the performance of 3f signals. Also diagonalization of the LSC sensing matrix

+ Diagonalization of the output matrix.

+ Noise characterization of 3f PDs => confirm the noise are low enough to keep the lock of the central part

- Power-recycling gain issue related (#5541)

+ Estimation of the mode matching efficiency => maybe we can use power-recycled ITMs to estimate it (?)

+ Implementation of auto alignment servos and scripts for MICH, PRCL and SRCL. => integrate it to the existing ASS model

+ Search for a possible loss factor

5633   Fri Oct 7 22:31:53 2011 kiwamuUpdateSUSnoisy ULSEN on ETMY

Yesterday Koji was claiming that the rms monitor of ULSEN on ETMY didn't well go down.

Indeed something bad is happening on ULSEN of ETMY.

I guess it could be a loose connection.

(The unit of Y axis in the plot is not true. Don't believe it !)

5636   Fri Oct 7 23:23:05 2011 kiwamuUpdateSUSSRM oplev was oscillating

The SRM oplevs were found to be oscillating because of a small phase margin.

I reduced the gains to the half of them. The peak which Steve found today maybe due to this oscillation.

 Quote from #5630 The SRM bounce peak 18.33 Hz. Suresh helped me to retune filter through Foton, but we failed to remove it.

5637   Sat Oct 8 00:44:42 2011 kiwamuUpdateLSCcalibration of SRM actuator

The AC response of the SRM actuator has been calibrated.

(Summary of the calibration results)
BS = 2.190e-08 / f2     [m/counts]
ITMX  = 4.913e-09 / f2   [m/counts]
ITMY  = 4.832e-09 / f2   [m/counts]
PRM   = 2.022e-08 / f2  [m/counts]
SRM   = 2.477e-08 / f2  [m/counts]    ( NEW ! )

(Measurement)
The same technique as I reported some times ago (#4721) were used.
The Signal-Recycled ITMY was locked for measuring the actuator response.
Since the ITMY actuator had been already calibrated, first the sensor was calibrated into [counts/m] by exciting the ITMY actuator and then calibrated the SRM actuator with swept sine measurement.

- - notes to myself
SRCL GAIN = 2.2
Sensor = REFL11_I
Demod. phase = 40 deg
Resonant condition = Carrier resonant
Gain in WF = 0 dB

 Quote from #5583 The AC responses of the BS, ITMs and PRM actuators have been calibrated.

5638   Sat Oct 8 04:41:07 2011 kiwamuUpdateLSClength fluctuations in SRCL

For a comparison, the length fluctuation of Signal-Recycled ITMX (SRX) and ITMY (SRY) have been measured.

Roughly speaking the length motion of SRX and SRY are as loud as that of PRCL.

Some details about the measurement and data analysis can be found in the past elog entry (#5582).

In the process of converting the raw spectra to the calibrated displacements the SRM actuator was assumed to have a resonance at 1Hz with Q = 5.

(Notes on SRX/Y locking)

Sensor = REFL11_I
Actuator = SRM
Demod. phase = 40 deg
SRCL_GAIN = 20
UGF = 100 - 200 Hz
Resonant condition = Carrier resonance
Whitening gain = 0 dB
ASDC = 360 counts

 Quote from #5582 The MICH and PRCL motions have been measured in some different configurations.       + PRCL is always noisier than MICH.

5639   Sun Oct 9 17:13:46 2011 kiwamuUpdateLSCFirst attempt to estimate mode matching efficiency using interferometer

The efficiency of the mode matching (MM) to PRC (Power-Recycling Cavity) has been estimated by using the interferometer.

The estimated MM efficiency is about 74 % when losses in the cavity are assumed to be zero.

(Motivation)

There had been an issue that the recycling gain didn't go to the designed high value of about 42  (#5541).
One of the possibilities is a low efficiency in the MM to PRC (also see #5541).
Although the MM efficiency had been measured using a beam scan ( see a summary on the wiki) a long time ago, it haven't been verified.
Therefore the MM has to be reviewed by using the real interferometer.

(Measurement)

The concept of this measurement is observe the amount of the reflected light from a power-recycled cavity and estimate the MM efficiency based on the measured reflectivities.
Since using the real PRC (consisting of BS, ITMs and PRM) could be a too complicated system for this measurement,
simpler cavities, namely Power-Recycled ITMX and ITMY (PRX and PRY), were used to examine the MM efficiency.
The measurement goes in the following order :
(1) Measurement of the amount of the single-bounce reflection from PRM with BS and ITMs misaligned.
(2) Lock PRX or PRY to carrier resonance.
(3) Alignment of PRX/Y to maximize the intracavity power. This time ASDC was used as a monitor of the intracavity power.
(4) Measurement of the amount of the reflected light when the cavity is in resonance. The value in REFLDC was averaged in 100 sec.
=> done by tdsavg 100 C1:LSC-REFLDC_OUT
The same measurement was performed for both PRX and PRY.

- locking parameters -
Sensor = REFL11_I
Whitening gain = 10 (30 dB)
PRCL_GAIN = 2
UGF ~ 200 Hz

(Analysis)

In order to estimate the relation between the MM efficiency vs. the reflected light, two models are considered:
(1) simple model => no loss and no sidebands
(2) sideband-included model => no loss but sidebands are taken into the account of the reflection.

(1) In the simple model the reflectivity Prefl / Pin is expressed by
[Reflectivity]  = Prefl / Pin = Z * Rcav +  (1- Z) * Rprm

where Z is MM efficiency and Rprm is the reflectivity of PRM
and Rcav is the reflectivity of PRX/Y when it's resonance and it is defined by
Rcav = | rprm - ritm t2BS|2 / |1 -rprm ritm t2BS |2

Tprm = 5.75% and Titm = 1.4 % are assumed in all the calculations.
In the first equation the first term represents the mode matched light and hence it couples with the cavity through Rcav.
The second term is the non-mode-matched light and because they are not interacting with the cavity they will be simply reflected by PRM through Rprm.

(2) In reality two phase-modulated light (11 MHz and 55 MHz) will behave differently from the carrier.
For example when the carrier is in resonance the sidebands will be anti-resonance against the cavity.
So that the amount of REFLDC will be slightly bigger because of the reflection of the sidebands.

Prefl = Z * Rcav * Pc + Z * Ranti * Ps +  (1- Z) * Rprm * (Pc + Ps)

where Pc and Ps are the power in the carrier light and the sidebands respectively.
And Ranti is the reflectivity of the anti-resonance PRX/Y, which can be obtained by replacing the minus sign by the plus sign in the equation of Rcav shown above.
It is assumed that the sum of the carrier power and sidebands power is the incident power Pin = Pc + Ps.
The power in the carrier and the sidebands were estimated based on the OSA measurement (#5519), so that
Pc / Pin = |J0(0.14)|2 * |J0(0.17)|2 =  0.976
Ps / Pin = 2 * |J1(0.14)|2 + 2 * |J1(0.17)|2 =  0.024

(Results)

Here are the measured values in REFLDC

-- Measurement 1 : PRX
Single bounce from PRM = 4802.27 counts
==> the incident power = 5095.25 counts
Reflected light from PRX = 4433.88 counts
==> Reflectivity = 0.8702

-- Measurement 2 : PRY
Single bounce from PRM = 4833.05 counts
==> the incident power = 5127.05 counts
Reflected light from PRX = 4444.48 counts
==> Reflectivity = 0.86672

On average the reflectivity of power-recycled ITM cavity was 0.868 with a standard deviation of  0.001744.
Actually the standard deviation estimated here is not fair because the measurement was done by only twice,
but my intention was that I wanted to see how the error can affect the estimation of the MM efficiency.
Here is a plot comparing the model curves and the measured values with 5 sigma error box (5 times of measured standard deviation).

It is shown that the mode matching efficiency is 73.7 % when the sideband-included model is considered.
With the 5 sigma deviation it can go from 65% to 82% but it is still low and lower than the beam scan measurement ( see a summary on the wiki).

Anyways the estimated MM efficiency with the sidebands effect included and without loss effect is

MM efficiency = 73.7 +/- 1.7 % (1 sigma error)  or +/- 8.7 % (5 sigma error)

5643   Mon Oct 10 13:52:04 2011 kiwamuUpdateLSCRE: First attempt to estimate mode matching efficiency using interferometer

 Quote from #5640 "^2"s are missing in the second equation, but the calculation results seem correct. PRX and PRY have different mode matching because of the Michelson asymmetry. Are individually estimated mode matching indicates any sign of reasonable mode mismatch? (The difference can be very small because the asymmetry is not so big.)

- Thank you for the correction. The missing square operation has been added correctly on the last entry (#5639).

- As for the individual MM efficiency,
I was assuming that the MM solutions are the same for PRX, PRY and the real PRC, so I haven't carefully checked differences between those cavities.
However as you mentioned the difference in those cavities can be tiny due to the small 3 cm Schnupp asymmetry.
Anyway I will briefly check it to make me sure.
5648   Tue Oct 11 03:35:16 2011 kiwamuUpdateLSCBS actuator reponse at low frequency : measured

The response of the BS actuator in a low frequency regime has been measured.

After the measurement I did a coarse fit to see if the low frequency data agree with the high frequency response which I have measured two weeks ago (#5583)
So far it shows a good agreement with the high frequency data (see the plot below). Tomorrow I will do a serious fitting.
Once the calibration of BS is done, the low frequency responses of ITMs, PRM and SRM will be done by simply exciting BS and comparing them (maybe at a couple of frequency points around 0.1Hz).

(Measurement)

+ With free swinging MICH, the sensor (AS55_Q) was calibrated into counts/m.

=> The peak-peak counts was about 110 counts. So the sensor response is about 6.5x108 counts/m

+ Locked Michelson with AS55_Q and the signal was fedback to BS.

+ Set the UGF high enough so that the open loop gain below 10 Hz is greater than 1.

+ With DDT's swept sine measurement, C1:LSC-MICH_EXC was excited with a big amplitude of 40 counts.

+ Took a transfer function from C1:LSC-MICH_OUT to C1:LSC-MICH_EXC.

+ Calibrated the transfer function into m/counts by dividing it with the sensor response.

 Quote from #5641 One possible reason is that my actuator responses are not so accurate below 1Hz. I will measure the DC response of all the actuators and it will completely determine the shapes of the actuator responses except for the region around the resonance.

5652   Tue Oct 11 19:11:25 2011 kiwamuUpdateLSCRe: BS actuator reponse at low frequency : measured

I think the precision due to the loop gain uncertainty is something like 0.1% at 0.1 Hz. It's not the issue.

The real issue was the loud motion of MICH, which degrades the coherence of the measurement.

Also last night I tried the fringe hopping technique and gave it up for several reasons.

(uncertainty due to the loop gain)

When MICH is locked, the signal at C1:LSC-MICH_OUT can be expressed in frequency domain by

MICH_OUT = G / (1+G) * (1 / A) * X + G / (1+G) * (1 / H) * (1 / A) * S,                 [1]

where G is the open loop gain, A is the actuator response, H is the sensor transfer function (constant factor),
X is the natural (unsuppressed) motion of MICH and S is an excitation injected at C1:LSC-MICH_EXC.
When the natural motion of MICH X is smaller than the excited displacement S/H, dividing MICH_OUT by S gives

[Transfer function] = S / MICH_OUT
= (1+G) /G * H * A

At low frequency the open loop gain is always big, so that the transfer function can be approximated to

[Transfer function] ~ H *A

This approximation is valid with a precision of 1/G.
In my case yesterday, the open loop gain at 0.1Hz was about 103 or more than that, so the uncertainty due to the loop gain was 0.1% or even less.

(Effect from the MICH motion)

In the equation [1], it is shown that the MICH motion X shows up together with the excitation signal.
Actually this MICH motion term was not completely negligible and eventually this term disturbs the measurement resulting in a low coherence.
In order to get a high coherence in the measurement, X should be smaller than the excited displacement S/H,

X << S / H

This the reason why I had to inject a big excitation signal. Although the coherence around 1Hz turned out to be still low due to the loud natural motion in MICH.
The excitation was already close to 0.1 um level in terms of peak-to-peak displacement, and I wasn't able to increase it any more because the MICH signal would run into a nonlinear regime.
In the worst case I lost the lock due to a too much excitation.

(Fringe hopping technique)

Actually I tried and gave up this technique. That's why I did the in-loop measurement.
My feeling is that this technique is not suitable for the 40m.
What I tried was to flip the sign of the MICH control such that the fringe hops from the dark fringe to the neighbor bright fringe or vice versa.
Difference in the control signal (C1:LSC-MICH_OUT) was supposed to give us the amount of signal which drives the actuator by exactly quarter of the laser wave length.
However this technique turned out to be not good because
(1) BS actuator is too strong
=> expected difference in the control signal is quite small.
=> \lambda / 4 / A ~ 12 counts, where A is the actuator DC response of about 2.2e-8 [m/counts].
(2) MICH motion was too loud
=> I saw such a tiny 12 counts difference in the control signal, but once the hopping is done the control signal immediately fluctuated and it was really hard to precisely measure it.
=> It's simply because MICH was loud, and the actuator tried to suppress the motion and it resulted such an immediate signal fluctuation in the control signal

 Quote from #5649 This seems like an error prone method for DC responses due to the loop gain uncertainty. Better may be to use the fringe hopping method (c.f. Luca Matone) or the fringe counting method

5654   Wed Oct 12 00:35:42 2011 kiwamuUpdateLSCTRY path realigned

The TRY (TRansmitted light from Y arm ) path was a bit realigned because there had been a small clipping.

This clipping was introducing offsets on the error signals of the C1ASS servo.

(Story)

During I was running the C1ASS servo on the Y arm I found every time after the auto-alignment is done there still remained a slight offset in the beam pointing,

I looked at the CCD camera which looks at the transmitted light and then introduced an intentional misalignment in ETMY in order to find an obvious clipping.

Indeed there was a clipping in horizontal direction. I checked through the optics on the Y end optical bench.

On the second mirror (beam splitter) the beam was on a very edge. So I steered the first steering mirror to fix it,

In addition to that an iris which is placed between the first and second mirror was also clipping the beam,

So I fully opened the aperture of the iris.

5656   Wed Oct 12 17:53:01 2011 kiwamuUpdateLSCBS actuator response : fitting done and histroy of delays

An update on calibration of the BS actuator : A fitting has been done.

(Fitting)

I used LISO for fitting the complex transfer function.
Because the data points around 1 Hz didn't have big coherence a few data points, which had coherence of less than 0.9, were excluded.
Also the fitting of the Q-factor wasn't successful due to the lack of good data points around the resonance.So I left Q fixed to be 5 in the fitting.

(Fitting result)

G =  2.18060874008e-8 +/- 6.425e-10 (2.95%)
f0 =  1.0100491195 +/- 1.51e-2 (1.49%)  [Hz]
Q = 5 (fixed)
delay =  423.2753462089e-6 +/- 4.989e-6 (1.18%)  [sec]

(History of delay)
Because we have been observing several different amount of delays in different configurations, perhaps it is worth to summarize those numbers.
 description delay [usec] elog entry MICH lock (BS actuation) 423 this entry LSC feed forward path 127 #5218 MICH lock (BS actuation) 600 #4638 ALS on X arm (ETMX actuation) 330 #4196 RFM (from c1lsc to c1sus) 125 #4153 from ADC to DAC (all the front end machine) 38-110 #3961 from ADC to DAC (c1sus) 124 #3838 RFM (c1ioo and c1sus) 8-62 #3855

 Quote from #5648 Tomorrow I will do a serious fitting.

5659   Thu Oct 13 03:22:53 2011 kiwamuUpdateLSCmeasurement of sensing matrix : just began

- status update on LSC activity :

The measurement of the LSC sensing matrix has begun. But no useful results yet.

The measurement script (#4850) ran pretty well after I did some modifications to adopt the script to the latest LSC model.

However the SNR weren't so great particularly in REFL33 in the PRMI configuration.

So I will tune the amplitude of excitations and integration times tomorrow.

Currently the excitation is at 238.1 Hz, where no disturbing structures are found in the spectra.

5665   Fri Oct 14 04:35:45 2011 kiwamuUpdateLSClocking tonight

The lock of DRMI wasn't stable enough to measure the sensing matrix. Failed.

PRMI and SRMI were okay and in fact they could stay locked robustly for a long time.

I added a new option in the C1IFO_CONFIGURE screen so that one can choose Signal-Recycled Michelson in carrier resonant condition.

Additionally the orthogonalization of the I-Q signals on REFL55 should be done because it hasn't been done.

5667   Fri Oct 14 18:38:41 2011 kiwamuUpdateSUSC1:SUS-ETMX_SPDMon fixed

 Quote from #5666 Anyway, things are working now:

Good job ! Thank you so much

5670   Sat Oct 15 16:01:26 2011 kiwamuUpdateIOOabout LOCKIN module

 Quote from #5669 To make things faster, I think we can just make a LOCKIN which has 3 inputs: it would have one oscillator, but 6 mixers. Should be simple to make.

I think the idea of having multiple inputs in a LOCKIN module is also good for the LSC sensing matrix measurement.

Because right now I am measuring the responses of multiple sensors one by one while exciting a particular DOF by one oscillator.

Moreover in the LSC case the number of sensors, which we have to measure, is enormous (e.g. REFL11I/Q, REFL33I/Q, REFL55I/Q, ... POY11I/Q,...) and indeed it has been a long-time measurement.

5684   Tue Oct 18 04:04:27 2011 kiwamuUpdateLSCmeasurement of sensing matrix : touchy SRM

I made some attempts to measure the sensing matrix of the central part.

I could measure the matrix in the PRMI configuration but wasn't able to measure the matrix in the DRMI configuration.

=> I will report the result of the PRMI sensing matrix tomorrow.

The main reason why I couldn't lock DRMI was that the suspensions were touchy and especially the SRM suspension wasn't good.

Some impacts due to the feedback during the lock acquisition completely kicks SRM away.

The watchdogs' RMS monitor on SRM easily rang up to more than 10 counts once the acquisition started.This is quite bad.

Also the stability of the PRMI lock was strongly depending on the gains of the PRM oplevs.

I guess I have to revisit the vertex suspensions more carefully (i.e. f2a coupling, actuator output matrix, damping gains, input matrices, oplev filters)

otherwise any LSC works in the vertex will be totally in vain.

5686   Tue Oct 18 15:20:03 2011 kiwamuSummaryIOORFAM plan

[Suresh / Koji / Rana / Kiwamu]

Last night we had a discussion about what we do for the RFAM issue. Here is the plan.

(PLAN)

1. Build and install an RFAM monitor (a.k.a StochMon ) with a combination of a power splitter, band-pass-filters and Wenzel RMS detectors.

=> Some ordering has started (#5682). The Wenzel RMS detectors are already in hands.

2. Install a temperature sensor on the EOM. And if possible install it with a new EOM resonant box.

=> make a wheatstone bridge circuit, whose voltage is modulated with a local oscillator at 100 Hz or so.

3. Install a broadband RFPD to monitor the RFAMs and connect it to the StochMon network.

=> Koji's broadband PD or a commercial RFPD (e.g. Newfocus 1811 or similar)

4. Measure the response of the amount of the RFAM versus the temperature of the EO crystal.

=> to see whether if stabilizing the temperature stabilizes the RFAM or not.

5.  Measure the long-term behavior of the RFAM.

=> to estimate the worst amount of the RFAM and the time scale of its variation

6. Decide which physical quantity we will stabilize, the temperature or the amount of the RFAM.

7. Implement a digital servo to stabilize the RFAMs by feeding signals back to a heater

=> we need to install a heater on the EOM.

8. In parallel to those actions, figure out how much offsets each LSC error signal will have due to the current amount of the RFAMs.

=> Optickle simulations.

9. Set some criteria on the allowed amount of the RFAMs

=> With some given offsets in the LSC error signal, we investigate what kind of (bad) effects we will have.

5690   Wed Oct 19 04:23:58 2011 kiwamuUpdateSUSSRM free swinging test

The following optics were kicked:
SRM
Wed Oct 19 04:22:53 PDT 2011
1003058589

5691   Wed Oct 19 05:15:44 2011 kiwamuUpdateSUStaking care of SRM

I made some efforts to fix the situation of SRM but it is still bad.

The POS motion wasn't well damped. Something is wrong either (maybe both) sensing part or actuation part.

I am going to check the sensing matrix with the new free swinging spectra (#5690)

(Symptom)

When I was trying to lock SRMI I found that the fringes observed at the AS camera didn't show spatial higher order modes, which is good.

So I thought the SRM suspension became quiet, but it actually wasn't. Because the RMS monitor of the SRM OSEMs already went to about 30 counts.

At the same time the opelev error signals were well suppressed. It means some DOFs which were insensitive to the oplev were ringing up, namely POS and SIDE.

According to the LSC error signal and the ASDC signal, I believe that the POS was going wild (although I didn't check the OSEM spectra).

(Some efforts)

+ Readjusted the f2a filters (see the attachment).

+ Tried to eliminate a coupling between the POS and SIDE drives by tweaking the output matrix.

=> In order to eliminate the coupling from the POS drive to SIDE sensor, I had to put a comparable factor into an element.

So it might be possible that the POS sensor was showing the SIDE signal and vice versa.

In order to check it I left SRM free swinging (#5690).

 Quote from #5684 The main reason why I couldn't lock DRMI was that the suspensions were touchy and especially the SRM suspension wasn't good.

5694   Wed Oct 19 10:49:35 2011 kiwamuUpdateSUSSRM oscillation removed

Quote:

The SRM oplevs were found to be oscillating because of a small phase margin.

I reduced the gains to the half of them. The peak which Steve found today maybe due to this oscillation.

 Quote from #5630 The SRM bounce peak 18.33 Hz. Suresh helped me to retune filter through Foton, but we failed to remove it.

Kiwamu removed the 18.3 Hz ocsillation by turning down the oplev servo gain.

5698   Wed Oct 19 14:03:41 2011 kiwamuUpdateGeneralvent prep : dichroic mirrors

Status update on dichroic mirror:

I got the specification sheet of an aLIGO 2" dichroic mirror from Lisa.

https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=25232

This is the one from ATF. It has low loss, a high R for 1064 nm and high T for 532 nm. So it matches our needs.

Based on this sheet we may reset some of the parameters in the specification (e.g. incident angle and etc.,) and will get a quote from ATF.

We will buy 3 of them, including 1 spare. First I need to review the specification.

5699   Wed Oct 19 15:46:49 2011 kiwamuUpdateSUStaking care of SRM

 Quote from #5691 I am going to check the sensing matrix with the new free swinging spectra (#5690)

The SRM input matrix has been readjusted.

However still there is the unwanted coupling from the POS drive to SIDE signal and from the SIDE drive to POS signal.

 BADNESS SRM pit     yaw     pos     side    butt UL    0.871   0.975   1.115  -0.295   1.096   UR    1.015  -1.025   1.128  -0.140  -1.053   LR   -0.985  -0.984   0.885  -0.088   0.831   LL   -1.129   1.016   0.872  -0.243  -1.020   SD    0.084   0.061   3.534   1.000  -0.018 4.24965

5702   Wed Oct 19 16:53:38 2011 kiwamuUpdateCDSsome screens need labels

Some of the sub-suspension screens need labels to describe what those row and column are.

5704   Wed Oct 19 17:33:07 2011 kiwamuUpdateGreen LockingETMY mechanical shutter : fully functional

The mechanical shutter on the Y end is now fully functional.

It is newly named to 'C1AUX_GREEN_Y_Shutter' in the EPICS world.

It uses the same binary output channel which had been served for the POY shutter.

To change the EPICS name I edited a db file called ShutterInterLock.db, which resides in /cvs/cds/caltech/target/c1aux.

After editing the file I rebooted the c1aux machine, by telnet and the reboot command in order to make the change effective.

Also I added this new shutter on the ALS overview screen (see the attachment below)

 Quote from #5701 The ETMY  shutter can be remotely switched from medm screen POY of mechanical shutters. The new cable from ETMY controller goes to east vertex EV-ISCT where it is connected to POY shutter hook up BNC cable.

5709   Thu Oct 20 04:47:37 2011 kiwamuUpdateLSCclipping search round 1

[Koji / Kiwamu]

We tried finding a possible clipping in the vertex part.

We couldn't find an obvious location of a clipping but found that the recycling gain depended on the horizontal translation of the input beam.

We need more quantitative examination and should be able to find a sweet spot, where the recycling gain is maximized.

(what we did)

+ locked the carrier-resonant PRMI.

+ with IR viewers we looked at the inside of ITMX, ITMY and BS chambers to find an obvious clipping.

=> found two suspicious bright places and both were in the ITMY chamber.

(1) POY pick off mirror : looked like a small portion of a beam was horizontally clipped by the mirror mount but not 100% sure whether if it is the main beam or a stray beam.

(2) The top of an OSEM cable connectors tower : although this is in the way of the SRC path and nothing to do with PRC.

+ Made a hypothesis that the POY mirror is clipping the main beam.

+ To reject/prove the hypothesis we shifted the translation of the incident beam horizontally such that more beam hits on the suspicious mirror

+ Realigned and relocked PRMI.

=> Indeed the recycling gain went down from 6 to 0.8 or so. This number roughly corresponds to a loss of about 50%.

However the MICH fringe still showed a very nice contrast (i.e. the dark fringe was still very dark).

Therefore our conclusion is that the POY mirror is most likely innocent.

ELOG V3.1.3-