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ID Date Authorup Type Category Subject
  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.

noise.png

(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]
 
actuators.png
 
(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

beforeOutage110930.png

  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 ?

outofloop.png

 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 ETMX.png       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 ITMX.png     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 PRM.png       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.

ITMYtable.png

 

  + 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)

oplevs.png

  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)

outofloop.png

(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.

ETMY_OSEMs.png

(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.

 actuators.png
(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.

length_noise.png

(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).

mm_reflection.png

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).
BSactuator.png

(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]

bode_BSactuator.png

 

(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.

Screen_shot_2011-10-14_at_4.24.01.png

 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.

Attachment 1: f2pSRM.png
f2pSRM.png
  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.

Attachment 1: SRMoplevKWMtune.png
SRMoplevKWMtune.png
  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  SRM.png       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

Untitled.png

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)

MechShutter.png

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.

  5744   Wed Oct 26 23:03:03 2011 kiwamuUpdateLSCRF distribution box : two more 55MHz available

The RF distribution box has been modified so that it generates two more 55 MHz LO signals.

After the modification I put the box back in place.

Then I checked the MICH and YARM locking quickly as a working test of the distribution box and it is working fine so far.

I will update the diagram of the RF distribution box (#4342) tomorrow.

 

(Motivation)

  Since we newly installed POP55 (#5743) an LO signal was needed for the demodulation.

However the RF distribution box didn't have any extra LO outputs.

Therefore we had to make a modification on the RF distribution box so that we can have a 55MHz LO signal for POP55.

Eventually I made two more 55MHz outputs including one spare.

 

(Modification)

The box actually had two extra output SMAs which had been just feed-thru connectors on the front panel without any signals going through.

In the box the modules consist of two categories; the 11MHz system and 55MHz system. I modified only a part of the 55MHz system.

The modification was done in this way:

  * split two branches of 55MHz into four branches by installing two new power splitters (ZMSC-2-1).

  * made and installed some SMA cables whose length were adjusted to be nicely fit in the box.

  * readjustment of the RF levels to 0-2 dBm at the outputs by replacing some attenuators.

  * checked the signals if all of them were happily coming out or not.

Also I found that the POX11 and POY11 demod boards were connected to the whitening filters in a wrong way.

The I and Q signals were in a wrong order. So I corrected them so that the upper inputs in the whitening filter is always the I signal.

 

(RF levels on 55MHz LO outputs)

Since the demod board requires a certain level of the RF signal as as LO, the LO signals have to be 0-2 dBm.

Here are the RF level in each 55MHz output after the adjustment of the level.

     AS55 =  0.76 dBm

     REFL55 = 0.76 dBm

     POP55 = 0.79 dBm

     spare = 0.83 dBm

Those numbers were measured by an oscilloscope and the oscilloscope was configured to measure the rms with the input impedance matched to 50Ohm.

In the measurement I used the actual input seed 55MHz signal from the RF generation box to drive the distribution box.

  5746   Thu Oct 27 16:09:37 2011 kiwamuUpdateLSCRF distribution box : two more 55MHz available

The diagram of the RF distribution box has been updated according to the modification ( #5744).

Both pdf and graffle files are available on the 40m svn : https://nodus.ligo.caltech.edu:30889/svn/trunk/suresh/40m_RF_upgrade/

Here shows the latest version of the diagram.

RF_Distribution_Box.png

Quote from #5744

I will update the diagram of the RF distribution box (#4342) tomorrow.

  5747   Thu Oct 27 18:00:38 2011 kiwamuSummaryLSCOffsets in LSC signals due to the RFAMs : Optickle simulation

The amount of offsets in the LSC signals due to the RFAMs have been estimated by an Optickle simulation.

The next step is to think about what kind of effects we get from the RFAMs and estimate how much they will degrade the performance.

(Motivation)

  We have been having relatively big RFAM sidebands (#5616), which generally introduce unwanted offsets in any of the LSC demodulated signals.
The motivation was that we wanted to estimate how much offsets we've been having due to the RFAMs.
The extreme goal is to answer the question : 'How big RFAMs do we allow for operation of the interferometer?'.
Depending on the answer we may need to actively control the RFAMs as already planed (#5686).
Since the response of the interferometer is too complicated for analytic works, so a numerical simulation is used.
 

(Results : Offsets in LSC error signals)

PRCL_200.png

 

MICH_200.png

 SRCL_200.png

  Figure: Offsets in unit of meter in all the LSC demodulated signals.  Y-axis is the amount of the offsets and the X-axis represents each signal port.
In each signal port, the signals are classified by color.
(1) Offsets in the PRCL signal. (2) Offsets in the MICH signal. (3) Offsets in the SRCL signal.
 
 
Roughly the signals showed offsets at a 0.1 nm level.
The numerical error was found to be about 10-10 nm by running the same simulation without the AM sidebands.
Here is a summary of the amount of the offsets:
 
    offsets [nm] (1f signal port)  offsets [nm] (3f signal port)  biggest offsets [nm] (signal port)
PRCL       0.3 (REFL11)       0.2 (REFL33)     1 (REFL55)
MICH      0.00009 (AS55)       0.8 (REFL33)     7 (POP11)
SRCL      0.1 (REFL55)       0.1 (REFL165)     40 (POX11)
In the SRCL simulation  REFL11I, REFL11Q, POP11I, POP11Q and POX11I didn't show any zero crossing points within 100 nm range around the resonance.
It is because that the SRCL doesn't do anything for the 11MHz sidebands. So it is the right behavior.
However POX11 was somewhat sensitive to the SRCL motion and showed a funny signal with a big offset.
 

(Simulation setup)

I applied the current PM/AM ratio according to the measurement (#5616, #5519)
The modulation indices used in the simulation are :
    + PM index in 11MHz = 0.17
    + PM index in 55MHz = 0.14
    + AM index in 11MHz = 0.17 / 200 = 8.5x10-4
    + AM index in 55MHz = 0.14 / 200 = 7.0x10-4
Note that the phases of the AM and PM sidebands are the same.

For clarity, I also note the definition of PM/AM ratio as well as how the first order upper sideband looks like.

ratio.png

upper.png
 

The optical parameters are all at ideal length although we may want to check the results with more realistic parameters:
    + No arm cavities
    + PRCL length = 6.75380
    + SRCL length = 5.39915
    + Schnupp asymmetry = 3.42 cm
    + loss in each optic = 50 ppm
    + PRCL = resonant for 11 and 55MHz
    + MICH = dark fringe
    + SRCL = resonant for 55 MHz
The matlab script will be uploaded to the cvs server.

Quote from #5686
  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.

  5749   Fri Oct 28 01:13:17 2011 kiwamuUpdateSUSITMX oplev : iris fully opened

I found that the sum of the ITMX oplev signals had gone down to zero yesterday.

I checked the ITMX table and found two iris on the He-Ne laser path were blocking the beam on their apertures.

I guess this is because we were working around there for installation of POP/POX and may have touched some of the oplev optics.

Then I fully opened the apertures of those two iris and the sum went back to nominal of 600 counts.

  5752   Fri Oct 28 03:42:50 2011 kiwamuUpdateLSCITMX table needs to be refined

(POX)

The POX beam had been 80% clipped at a black glass beam dump of the POX11 RFPD.

I steered the first mirror in the POX path to fix the clipping. Then the beam was realigned onto the RFPD.

However the beam is still very close to the black glass, because the incident angle to the second mirror is not 45 deg .

We need to refine the arrangement of the POX11 optics a bit more so that the beam will never be clipped at the black glass.

 

(POP)

 The POP optics also need to be rearranged to accommodate one more RFPD.

Additionally Rana, Suresh and I discussed the possible solutions of POP22/110 and decided to install a usual PD (PDA10A or similar) instead of a custom-made.

So a plan for the POP detectors will be something like this:

        + design an optical layout.

        + buy a 2 inch lens whose focul length is long enough (#5743)

        + rearrange the optics and install POP22/110

        + lay down a long SMA cable which sends the RF signal from POP22/110 to the LSC rack.

        + install a power splitter just before the demod board so that the signal is split into the 22MHz demoad board and 110MHz demod board.

           => make sure we have a right splitter for it.

        + install a band pass filter after the power splitter in each path.

           => A 22MHz band pass filter is already in hand. Do we have 110MHz band pass filter somewhere in the lab ?

The picture here shows the latest configuration on the ITMX table.

ITMXtable.png

Quote from #5743

RF photo diodes POP55 and POX11 are installed. The beams are aligned to the photo diodes. 

  5753   Fri Oct 28 04:57:00 2011 kiwamuUpdateLSCPOX11 demod board broken
The POX11 demodulation board is broken. It needs to be fixed in the daytime tomorrow.
It only outputs the Q signal and nothing is coming out from the I output.


(Some stuff checked)
 [OK] ADCs
 [OK] Whitening filters looked fine. Their gains were controllable from EPICS.
 [OK] Connection between the POX11 RFPD and demodulator box
 [OK] The Q signal showed the PDH signal of the X arm with an amplitude of about 200 counts, which almost is the same as that of POY11.
 [NOT GOOD] The I signal from the demod board
 [OK] Outputs cables, which send the I and Q signals from the demod board to WFs are fine.
         
(Test on the POX11 demod board)
 As usual, a test signal whose frequency is shifted by a little bit from that of LO was injected to the RF input of the board to see if the circuit is working.
The I signal didn't show up and there were no signals even in the monitor LEMO output.
Something is wrong in the I signal demodulation path on the circuit board.

Here is an actual time series of the I and Q signals in dataviewer. The I signal outputs just junk while the Q showed a nice sine curve.
Screen_shot_2011-10-28_at_2.26.02.png

  5754   Fri Oct 28 05:17:13 2011 kiwamuUpdateLSClocking activity : PZT1 is still railing

Status update on the LSC activity:

 To see how good/bad the beam pointing is, I locked the Y arm with POY11.
Then I ran the ASS servo to automatically correct the alignment of the ITMY and ETMY suspensions and also the beam pointing.
The result is that the PZT1_X is still railing to the negative side.
Due to it the transmitted light from the Y arm is about 0.6 or so which is supposed to be 1 if the beam pointing is perfect.
The EPICS value of PZT1_X is at the minimum of -10 and the ASS servo tried to push it more negative side.
 
 Tomorrow night I will intentionally introduce offsets in the MC suspensions to avoid the railing.
The goal will be a scan of the incident beam while measuring the recycling gain.
ELOG V3.1.3-