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ID Date Author Type Category Subjectup
  1007   Mon Sep 29 15:09:36 2008 steveUpdatePSLalmost 4 yrs plot of power & temps
The water chiller is normally running 1.5 C warmer than the laser head temp.
When control room temp is stable and PEM-count_temp is stable we can expect the head temp to be stable 20.0 C

PSL-126MOPA_HTEMP is running warmer in the last ~40 days

The ifo arm thermostate temp settings were raised by 2 F on 8-11-08
Attachment 1: 3.5y.jpg
  2048   Mon Oct 5 02:51:08 2009 robUpdateLockingalmost there

Working well tonight: the handoff of CARM to RF (REFL2I), successful reduction of CARM offset to zero, and transition control of MCL path to the OUT1 from the common mode board.  All that's left in lock acquisition is to try and get the common mode bandwidth up and the boost on.

  11177   Fri Mar 27 04:36:46 2015 denUpdateLSCals->pdh transition, prcl on 1f, alignment

Tonight I have modified transition steps from als to pdh signals. I have added 1:20 filters to CARM_A and DARM_A filter banks to make them unconditionally stable. These filters made locking more robust -- duty cycle is was ~70% tonight. I have also modified slow/ao crossover to avoid ringing up of lines above 1kHz.

Once AO is engaged with high bandwidth, REFL55 signal looks good and I transition PRCL from 165I to 55I. Optical gain compared to PRMI reduced from 55I/165I = -330 down to 55I/165I = 30 in full lock.

I worked on alignment of ETMs. Looking on the cameras I could improve arm power up to 160 and ifo visibility was 80%. POP22 fluctuated by ~50% and every few minutes we loose lock because POP22 almost touches zero.

  11179   Fri Mar 27 14:47:57 2015 KojiUpdateLSCals->pdh transition, prcl on 1f, alignment

Jenne and I interviewd Den this afternoon to make the things clear

- His "duty cycle" is not about the lengths of the lock stretch. He saids, the transition success probability is improved.

- For this improvement, the CARM transition procedure was modified to include turning on 1:20 (Z1P20) filter in CARM_A (i.e. ALS) once CARM_B (i.e. RF) dominates the loop in all frequency.

- I think this transition can be summarized like the attachment. At STEP4, the integration of the ALS is reduced. This actually does not change the stability of the servo as the servo stability is determined by the stability of the CARM_B loop. But this does further allow CARM_B to supress the noise. Or in other word, we can remove the noise coming from the CARM_A loop.

- The POP22 issue: Jenne has the trigger signal that is immune to this issue by adding some amount of POPDC for the trigger.
We can avoid the trigger issue by this technique. But if the issue is due to the true optical gain fluctuation, this may mean that the 11MHz optical gain is changing too much. This might be helped by PRC angular feedforward or RF 22MHz QPD at POP.

Attachment 1: CARM_transition.pdf
  193   Mon Dec 17 11:47:13 2007 albertoUpdateElectronicsan alternative design for the RFAM monitor's filter at 33Mhz
Since the Butterworth turned out o be rather wide-band, I tried an other configuration for the 33 MHz filter. Attached are the simulated transfer function and the measured. As one can see, the measured peak is much broader than expected.
Attachment 1: RFSim99-33MHz.png
Attachment 2: RF99-SimmButterworthPrototype.png
Attachment 3: RFSim99-33MHz-TFplot.png
  6828   Mon Jun 18 02:31:43 2012 yutaSummaryGreen Lockinganalysis of mode scan data

I analyzed mode scan data from last week.
Mode matching ratio for Y arm is 86.7 +/- 0.3 %. Assuming we can get rid of TEM01/10 by alignment, this can be improved up to ~ 90%.

Peak search, peak fitting and finnesse calculation:
  I made a python script for doing this. It currently lives in /users/yuta/scripts/modescanresults/analyzemodescan.py.
  What it does is as follows

  1. Read mode scan data(coarse5FSRscan.csv, fine1FSRscan.csv). Each column in the data file should be

[time] [some thing like C1:ALS-BEAT(Y|X)_(COARSE|FINE)_(I|Q)_IN1] [C1:LSC-POY11_I_ERR] [C1:LSC-TRY_OUT]

Each separated by comma. Currently, this script uses only TRY, but it reads all anyway

  2. Find peak in TRY data. For the peak search, it splits data in 1 sec and find local maximum. If the local maximum is higher than given threshold, it recognize it as a peak. If two peaks are very close, it uses higher one. This sometimes fails, because mode scan data we have is not so nice.

  3. Fit each peak with Lorentzian function,

TRY = a*b/(4*(t-c)^2+b^2) + d  (a>0, b>0)

  where a/b is a peak height, b is a linewidth (FWHM), c is a peak position in time, and d is a offset.
  I don't like this, but currently, a/b+c is fixed to the maximum value of TRY data used for fitting. This is because sometimes TRY data is so bad and I couldn't get the peak height correctly. Each points of TRY data doesn't have same error because cavity length is fluctuating and relation between cavity length and TRY is not linear. I think I should use some weighting for the fit, but currently, I just use least squares.

  4. Find TEM00 and calculate FSR in "seconds". I just used "seconds" assuming we did a linear sweep. This script recognize TEM00 from the given threshold.

  5. Calculate finesse using FSR and linewidth of the closest TEM00.

  Below are the result plots from this analysis. Calculated finesse looks quite high (~1000). I think this is from non-linearity in the sweep and error in "measured" line width.

Higher order modes and RF sidebands:

  Assuming the curvature of ITMY/ETMY are flat/57.5 m, Y arm length is 38.6 m(FSR 3.9 MHz), positions of HOMs and RF sidebands(11/55 MHz) in frequency domain should look like the plot below.
  The script for calculating this currently lives in /users/yuta/scripts/modescanresults/HOMRFSB.py, inspired by Yoichi's script for KAGRA

Mode-matching ratio:
  By comparing mode scan data and HOM/RF SB positions in a sophisticated way, you can tell which peak is which.

  From COARSE 5FSR measurement, peak heights are

TEM00 0.884, 0.896, 0.917, 0.905, 0.911
TEM01 0.040, 0.037, 0.051, 0.054, 0.062
TEM02 0.083, 0.078, 0.079, 0.071, 0.078
TEM03 0.018, 0.015, 0.013, 0.015, 0.014

  So the mode-matching ratio is

MMR = 86.2 %, 87.3 %, 86.5 %, 86.6 %, 85.5 %

  From FINE 1FSR measurement, peak heights and mode matching ratio is

TEM00 0.921
TEM01 0.031
TEM02 0.078
TEM03 0.014

MMR = 88.2 %

  Assuming each measurement had same error, mode-matching ratio from these 6 values is

MMR = 86.7 +/- 0.3 %  (error in 1 sigma)

  This can be improved by ~5% by alignment because we still see ~5% of TEM01/10. Study in systematic errors on going.

  5790   Wed Nov 2 21:15:06 2011 KatrinUpdateCDSand again c1scy.mdl compiled

I changed an ADC channel for GCY_ERR and thus recompiled the c1scy model.

  8442   Thu Apr 11 03:38:40 2013 DenUpdateLockingangular motion

Spectra of BS, PRM, ITMX, ITMY are attached with oplevs ON and OFF (in units of urad). Loops reduce RMS from ~2urad to ~0.3urad but phase margin should be increased. REF traces show loop OFF. <-- really?

Note how PRM pitch and yaw spectra are different in the frequency range 0.5 - 7 Hz; yaw is factor of 50 larger then pitch at 2 Hz.

Attachment 1: oplevs.pdf
oplevs.pdf oplevs.pdf oplevs.pdf oplevs.pdf
  9653   Wed Feb 19 08:07:01 2014 steveUpdatesafetyannual laser safety glasses check


 All 40m laser safety glasses are cleaned and measured this morning.  Bring your own safety glasses if you have to enter the 40m IFO room.


Glasses were washed in 1% Liquinox water solution and  their transmission measured at  165 mW,  2 mm OD beam of 1064 nm

Attachment 1: AA2014checked.jpg
Attachment 2: 2014check.jpg
  2814   Tue Apr 20 09:15:15 2010 steveSummarySAFETYannual safety audit
Attachment 1: safa.PDF
  14088   Thu Jul 19 13:35:30 2018 SteveSummaryVACannuloses pumped

Roughing down the annuloses required closing V1 for 13 minutes

IFO is 2.2e-5 Torr

Attachment 1: AnsPumped.png
  13459   Thu Nov 30 10:38:39 2017 SteveUpdateVACannuloses are not pumped

Annuloses are not pumped for 30 days, since TP2 failed.  IFO pressure 7e-6 Torr it,  Rga 2.6e-6 Torr

Valve configuration: Vacuum Normal as TP3 is the forepump of Maglev, annuloses are not puped at 1.1 Torr

TP3 50K rpm,  0.15A  24C, foreline pressure 16.1 mTorr



The TP3 foreline pressure was 4.8 Torr, 50K rpm 0.54A and 31C........Maglev rotation normal 560 Hz.......    IFO pressure 7.2e- 6 Torrit was not effected

V1 closed ......replaced drypump.........V1 opened

IFO 6.9e-6 Torrit at 19:55, TP3fl 18 mT,  50Krpm 0.15A 24C

VM1 is still closed



Attachment 1: AnnulosesNotPumped.png
  2717   Sat Mar 27 16:23:10 2010 KojiUpdateSUSanother SRM sidemagnet glued

Kiwamu and Koji

Last night we have released PRM from the gluing fixture. All of the six magnets are successfully released from the fixture.

We put SRM on the fixuture and glued a side magnet which we had failed at the last gluing.

We let it cure in the Al house. This should be the last magnet gluing until ETMs are delivered.

[Current status]

ITMX (ITMU03): all of magnets/guiderod/standoffs glued, mirror baked; balance to be confirmed
ITMY (ITMU04): all of magnets/guiderod/standoffs glued, balance confirmed, mirror baked
SRM  (SRMU03): magnets/guiderod/standoff glued; a side magnet gluing in process, balance to be confirmed, last stand off to be glued, mirror to be baked
PRM  (SRMU04): magnets/guiderod/standoff glued; balance to be confirmed, last stand off to be glued, mirror to be baked

TT:            magnets/guiderod/standoff glued; balance to be confirmed, last stand off to be glued, mirror to be baked

  5058   Thu Jul 28 21:52:40 2011 ranaUpdateComputersanother attempt to use pianosa
  1. Pianosa doesn't cache the SVN pwds so you need to re-enter at each SVN up or commit. This is different from the rest of our workstations. We need to determine what behavior we want.
  2. Tried to use the netGPIB scripts:

pianosa:gpib 0> ./readSR785.csh rb2
netgpibdata.py: Command not found.

  5053   Thu Jul 28 16:00:28 2011 kiwamuUpdateComputer Scripts / Programsanother offset script : offset2

A new offset-zeroing script has been developed and it is ready to run.


 The motivation is to replace the old zeroing script called offset by a better one because this old script somehow failed to revert the gain settings on a given filter bank.

The new script, named offset2, does the same job, but uses tdsavg instead of using ezcaservo. So it doesn't screw up the gain settings.

Additionally the structure of the script is much simpler than the old offset script, and fewer ezca-functions.

I will modify some scripts which use the old offset script so that all the offset-zeroing is done by offset2.



Useful scripts are listed on the 40m wiki


  14990   Wed Oct 23 18:40:58 2019 gautamUpdateCDSanother round of vertex FE reboots

I wanted to restart the c1oaf model. As usual, the first time the model was restarted, it came back online with a 0x2bad error. This isn't even listed in the diagnostics manual as one of the recognized error states (unless there is a typo and they mean 0x2bad when they say 0xbad). The fix that has worked for me is to stop and start the model again, but of course, there is some chance of taking all the vertex FEs down in the process. No permutation of mxstream and daqd process restarts have cleared this error. We need some CDS/RCG support to look into this issue and fix it, it is not reasonable to go through reboots of all the vertex FEs every time we want to make a model change.

  6136   Mon Dec 19 01:54:35 2011 kiwamuUpdateSUSanother trial of hystersis test

Another hysteresis test has begun at 1:50 PT, Dec/19.

It will finish after 3 or 4 hours. During the measurement the PSL mechanical shutter will be kept closed.

Time record                       
   Start:  Dec/19 1:50 PST
   End :  Dec/19  5:30 PST
  212   Sat Dec 22 15:32:11 2007 tobinAoGEnvironmentants
Ants are everywhere: on the PSL table, on the circuit board I'm soldering...

I believe I have discovered their energy source.
Attachment 1: DSC_0361.JPG
  12318   Thu Jul 21 08:24:20 2016 SteveUpdatePEMants alart

The heat drives the ants to the lab!  Make sure the light doors are tight on the chambers.


Attachment 1: ants_Alart.jpg
  13397   Mon Oct 23 09:17:41 2017 SteveUpdatePEMants alart

Do not leave organic trash or food boxes in the 40m to attrack ants !


Attachment 1: ants.jpg
Attachment 2: ants2.jpg
  7468   Wed Oct 3 15:37:04 2012 SteveUpdatePEMants on the PSL table

We observed one or two ants climbing over PMC optics without booties and safety glasses.

The floor was mopped with strong Bayer Home Pest Control solution in the Vertex area.

Do not work inside the 40m lab if you are sensitive to chemicals!


Attachment 1: IMG_1690.JPG
  7470   Wed Oct 3 16:26:58 2012 ManasaUpdatePEMants on the PSL table

I spotted around 4 within 30 minutes working at the PSL table even after the deathly spray. They seem to be running down from the cables on the oscilloscope rack to the table and the optics.

  7567   Wed Oct 17 09:01:37 2012 SteveUpdatePEMants on the PSL table


We observed one or two ants climbing over PMC optics without booties and safety glasses.

The floor was mopped with strong Bayer Home Pest Control solution in the Vertex area.

Do not work inside the 40m lab if you are sensitive to chemicals!


 The floor is mopped again with strong PEST CONTROL SOLUTION in water in the Vertex area.

Do not plane to work in the IFO-room till noon if you are sensitive to chemicals!

  10141   Mon Jul 7 16:39:26 2014 SteveUpdatePEMants on the PSL table



We observed one or two ants climbing over PMC optics without booties and safety glasses.

The floor was mopped with strong Bayer Home Pest Control solution in the Vertex area.

Do not work inside the 40m lab if you are sensitive to chemicals!


 The floor is mopped again with strong PEST CONTROL SOLUTION in water in the Vertex area.

Do not plane to work in the IFO-room till noon if you are sensitive to chemicals!

 Ants are back on the PSL table. We'll be mopping the floor with pest control solution tomorrow morning.

  1290   Wed Feb 11 00:50:24 2009 carynUpdateGeneralants?

So, near 2 of the trashcans in the control room and underneath a desk there are hundrends of ants. Is this normal?

  8144   Sat Feb 23 14:04:07 2013 KojiUpdateComputersapache retarted (Re: linux1 dead, then undead)

apache has been restarted.
How to: search "apache" on the 40m wiki


I had to reboot nodus to get it recovered


  4781   Thu Jun 2 16:31:41 2011 JamieUpdateCDSaquired SUS channel name suffixes changed from _DAQ to _DQ

CDS changed the suffix for all aquired channel names from _DAQ to _DQ.  When we rebuilt the sus models, described in the previous log, the channel names were changed and consequently the channel files were completely rewritten.

To fix the issue, the latest archived channel file was copied back into the chans directory, and the suffixes were changed, as so:

cd /opt/rtcds/caltech/c1/chans
cp archive/C1SUS_110602_155403.ini  C1SUS.ini
sed -i 's/DAQ/DQ/g' C1SUS.ini

We then restarted the models and the framebuilder.

  7996   Mon Feb 4 22:46:03 2013 JamieSummaryGeneralarbcav for SRC with curved TTs

I ran Zach's arbcav on our SRC with curved TTs and the situation looks much worse than the PRC.

I used the following parameters

SRM: RoC = 142 m, T = 10%
ITM: RoC = 83.1e3 m, T = 1.4%
SRC length: 5.37 m

In this case, with TT RoC of -600, the combined cavity g-factor = 0.9986, and astigmatism from SR3 makes the cavity patently not stable.  You have to go up to an RoC of -710 before the cavity is just over the edge.



  8005   Tue Feb 5 19:16:22 2013 JamieSummaryGeneralarbcav of PRC with +600 RoC PR2/3

This is just a simple rerun of arbcav from #7995 but with the PR2/3 RoCs set to 600, instead of -600.  Overall g-factor = 0.922, and the modes are well separated:

mode_density_PRC_3.pdf mode_density_PRC_2.pdf 

This doesn't take into account the effect of traveling through the substrates (still working on it).  It assumes the PR2/3 have been moved such that the cavity fold lengths remain the same.

This is something that we need to keep in mind: we will need to adjust the position of the PR2/3 to keep the fold lengths the same.

  8040   Fri Feb 8 18:23:32 2013 JamieSummaryGeneralarbcav of half PRC with flipped PR2

Arbcav with half PRC (flat temporary mirror in front of BS), PR2 RoC = 600m, PR3 RoC = -600m:


NOTE: this does NOT include the affect of the PR2 substrate in the cavity.  Arbcav does not handle that.  It would have to be modified to accept arbitrary ABCD matrices.

NOTE: I added to the mode plot the frequency separation of the first HOMs from the carrier (\omega_{10/01}), in units of carrier FSR.

  8041   Fri Feb 8 19:29:44 2013 yutaSummaryGeneralarbcav of half PRC with flipped PR2

We need expected finesse and g-factor to compare with mode-scan measurement. Can you give us the g-factor of the half-PRC and what losses did you assumed to calculate the finesse?

Also, flipped PR2 should have RoC of - R_HR * n_sub (minus measured RoC of HR surface multiplied by the substrate refractive index) because of the flipping.
According to Jenne dictionary, HR curvature measured from HR side is;

PRM: -122.1 m
PR2: -706 m
PR3: - 700 m
TM in front of BS: -581 m

Please use these values to calculate expected g-factor so that we don't get confused.


Arbcav with half PRC (flat temporary mirror in front of BS), PR2 RoC = 600m, PR3 RoC = -600m:

  7995   Mon Feb 4 19:48:32 2013 JamieSummaryGeneralarbcav recalc of PRC with correct ITM transmission

I noticed that Koji used a high reflector for the ITMs for his full PRC arbcav calculation. I just redo it here with the correct ITM transmission and RoC for completeness.

In this case the finesse is 95, instead of 121.



  9465   Fri Dec 13 13:28:07 2013 DenUpdateLSCarm calibration template

I have calibrated ETMX and ETMY actuators and added a template armSpectra.xml into /users/Templates directory.

Template shows control and error signals of both arms. Procedure is standard: calibrate control to meters and match error based on UGF measurement. XARM UGF: 200 Hz, YARM UGF 210 Hz.

Noise level at high frequencies (>100 Hz) for YARM is 3*10-15 and is factor of 3 better then for XARM. Servo gains are in the same ratio. I think there is less light on POX than on POY RF PD because I checked phase rotation and analog gain. I assume transimpedances are the same.

Attachment 1: armsCal.pdf
  1247   Thu Jan 22 23:36:50 2009 peteHowTooplevsarm cavity oplev calibration
calibrated the y-arm oplevs. the procedure is contained in a matlab script. the whereabouts of this script will be revealed in a future log entry.

ITMYpit 140 microrad/ct
ITMYyaw 98 microrad/ct
ETMYpit 400 microrad/ct
ETMYyaw 440 microrad/ct (previous measurement gave 420 microrad/ct)


1) Start with a single arm aligned and locked. Dither the mirror tilt in a DOF. Measure arm cavity power and oplev error signal. See the first attached plot.

2) Fit the plot to a gaussian and determine mu and sigma.

3) For a spherical ETM optic, the power in the cavity P(a), as a function of translational beam axis displacement a=R*sin(theta), is proportional to exp[-a^2/(2*x^2)] where x is the waist size (D. Anderson APPLIED OPTICS, Vol. 23, No. 17, 1984). The power as a function of mirror tilt in cts, P(tilt) is proportional to exp[-(tilt-mu)^2 /(2*sigma^2)]. So if R is the mirror radius then theta = arcsin(a/R) = arcsin[(1/R)*(tilt-mu)*x/sigma)].

4) Fit theta versus mirror tilt to get the calibration. See the second attached plot.

5) For a flat ITM optic, mirror tilt causes an angular displacement of the beam. The math for this case is given in Anderson.
Attachment 1: ETMYpitpower.png
Attachment 2: ETMYpitcal.png
  1249   Fri Jan 23 12:48:12 2009 KakeruUpdateoplevsarm cavity oplev calibration
I calibrated optlevs of x and y arm cavity, indipendently from Peter's work.

ITMX pit: 77 microrad/ct
ITMX yaw: 73 microrad/ct
ETMX pit: 280 microrad/ct
ETMX yaw: 263 microrad/ct

ITMY pit: 120 microrad/ct
ITMY yaw: 93 microrad/ct
ETMY pit: 280 microrad/ct
ETMY yaw: 270 microrad/ct

This result is similar to Royal's one (within 30% difference except for ETMX pit), but different from Peter's in ETMY.

The attached figure is the data and fitted curve of ITMX pit.
I took this data for 8s, with 4 Hz excitation.
Attachment 1: ITMX_pitch.png
  1259   Thu Jan 29 17:24:41 2009 KakeruUpdateoplevsarm cavity oplev calibration
I calibrated optlevs again. My previous work has a lot of mistakes, so ignore it.

ITMX pit: 195 microrad/ct
ITMX yaw: 185 microrad/ct
ETMX pit: 303 microrad/ct
ETMX yaw: 296 microrad/ct

ITMY pit: 192 microrad/ct
ITMY yaw: 141 microrad/ct
ETMY pit: 294 microrad/ct
ETMY yaw: 301 microrad/ct

(For ITMY, the data is low quality)

My calcuration and Peter's(based on Royal's report) is different in two point.
i) Royal uses some geometrical factor to calibrate ITM.
ii) Royal fits data to exp(-a^2/(2*w0^2)), and I fit data to exp(-a^2/w0^2).

When I calculate with modification of these differences, my result became almost same value of Peter's one.
Now we are discussing which equation is correct.

But we must do some laser works before it...
  1403   Sat Mar 14 22:53:12 2009 KakeruUpdateoplevsarm cavity oplev calibration
I finished a calibration of optical levers.

To calibrate oplevs, I locked appropriate cavity and tilted a mirror.
A cavity with tilted mirror decrease its arm power. So I can know how much the tilt is.
For calibration of ITMX and ETMX, I locked X arm and measured TRX.
For ETMX, ETMY and BS, I locked Y arm and measured TRY
For PRM, I locked PRC and measured SPOB
For SRM, I locked SRC and measured REFL166

I used, for example, C1:SUS-ITMX_OPLEV_PERROR as an oplev signal.

The calibration factors for each mirror is below. The attachment is figures of my fitting.
I used modified equation for ITM calibration from my last calibration, so the value become small around 30%.

ITMX Pitch: 142   microrad/counts
ITMX Yaw:   145   microrad/counts
ITMY Pitch: 257   microrad/counts
ITMY Yaw:   206   microrad/counts

ETMX Pitch: 318   microrad/counts
ETMX Yaw:   291   microrad/counts
ETMY Pitch: 309   microrad/counts
ETMY Yaw:   299   microrad/counts

BS Pitch:    70.9 microrad/counts
BS Yaw:      96.3 microrad/counts

PRM Pitch:   78.5 microrad/counts
PRM Yaw:     79.9 microrad/counts

SRM Pitch:  191   microrad/counts
SRM Yaw:    146   microrad/counts

It looks strange that ITMY, BS and SRM has different value. I think this is a fitting problem.
These data have some asymmetry and cause these 20%-30% difference.
Actually, PRM Yaw has a little asymmetry but the value doesn't differ from Pitch.
This means that this calibration factor potentially has below 30% error.
(These data are the most fine data. I think we must adjust Y arm yaw alignment. The beam spot of ETMY looks too low!)
For SRM, I couldn't get fine data because it was very sensitive to tilt and easily lose its lock.
When I tuned cavity enough, The data become almost flat, so I used detuned cavity.

It is also strange that ITMX and ITMY is different. I guess that this is caused by the difference of the QPD input. The sum of QPD is around 10000 for ITMX and around 4500 for ITMY.
The difference between BS or PRM and SRM is same, I guess. The sum of QPD input for BS and SRM is around 1500, but for SRM, it is around 10000.

I will write more detailed document and upload it with my calibration code.
Attachment 1: oplev.pdf
oplev.pdf oplev.pdf oplev.pdf
  1413   Fri Mar 20 15:37:58 2009 KakeruUpdateoplevsarm cavity oplev calibration

I calibrated several oplevs with OSEM signal as a confirmation of my fitting method the method is:

1) I tilted mirrors and get signals from oplevs (C1:SUS-XXXX_OPLEV_PERROR) and OSEM (C1:SUS-XXXX_SUS{PIT/YAW}_IN1).
2) I compared amplitudes of two signals and calculated conversion factors.
3) I calibrated factors above to microrad/counts with
i) The calibration factor of OSEM (2 V/mm)
ii) The calibration factor from count to V of OSEM; 1/16384 V/counts
iii) The shape of whitening filter of OSEM: 30, 100:3 (these values is taken from http://www.ldas-sw.ligo.caltech.edu/ilog/pub/ilog.cgi?group=40m&task=view&date_to_view=04/07/2005&anchor_to_scroll_to=2005:04:07:20:28:36-rana).
iv) The size of mirrors; 125mm for large optics and 75.5mm for small optics.

This calibration has some uncirtainties.

1) The calibration factor of OSEM looks very rough.
2) Output matrixes looks not to be normalized. It looks vary from 0.5 to 1.5 .
3) I don't know where OSEMs are put on mirrors accurately.

So, this calibration is very rough and may have uncertnty of a few factors, I could confirm my fitting calibration in orders.

From this calibration, I got calibration factors listed below.

ITMY Pit: 76 microrad/counts (257 microrad/counts with fitting method)
ITMY Yaw: 58 microrad/counts (206 microrad/counts)
BS Pit : 27 microrad/counts (70.9 microrad/counts)
PRM Yaw : 22 microrad/counts (79.9 microrad/counts)

For the other mirrors, OSEM outputs matrixes are not optimized and I couldn't get fine signals (I think this is not good!).

Each value is smaller than the value calibrated with fitting method in factor 3-4. There looks to be some systematic error, so there must be some difference in parameters used in OSEM calibration.
  1434   Thu Mar 26 09:08:18 2009 KakeruUpdateoplevsarm cavity oplev calibration
I uploaded a document about my oplev calibration.

At same place I put my matlab codes for calibration.
  9789   Tue Apr 8 19:10:39 2014 ranaUpdateLSCarm length measurements

 Since we don't have an arm length precision measurement (i.e. better than centimeters), why not just do as Koji suggests and use the ALS to get the frequency spacing between a few red FSR and then we have the measurement solid ?

  9790   Tue Apr 8 23:04:14 2014 manasaUpdateLSCarm length measurements


 Since we don't have an arm length precision measurement (i.e. better than centimeters), why not just do as Koji suggests and use the ALS to get the frequency spacing between a few red FSR and then we have the measurement solid ?

Arm lengths measured using ALS. Both the arms were estimated to have the same length (to the order of a centimeter) 37.51 m

I used ALS error signal to lock the arms and scanned the arm to find 4 consecutive IR resonances. From the beat note frequencies measured using the spectrum analyser during IR resonance, the FSR, and hence the length of the arms were calculated.

The estimated lengths are not very precise down to a mm given the resolution of the spectrum analyser. We have brought out the rubidium clock to use as reference for the spectrum analyser to challenge the measurements.

  9804   Fri Apr 11 18:55:28 2014 manasaUpdateLSCarm length measurements

Arm lengths were measured using ALS

X arm length = 37.79 +/- 0.05 m

Y arm length = 37.81 +/- 0.01 m

Whats and whys

We want to measure the arm length with an accuracy of say a mm.

This would mean a measurement precision of 1e-3/40=25ppm. (1mm in 40m)

So the required measurement resolution on the spectrum analyser is 25ppm*4MHz=100Hz (assuming the cavity FSR is roughly 4MHz). 

Although the spectrum analyser does not limit the measurement precision, we are limited by the noise in ALS at 1000Hz rms. So we can use ALS only to measure arm length precise to the order of a few mm.

RXA: Not that we really need to right now, but even with an ALS noise of 1000 Hz, we can can do better just by averaging at each resonance point. And fitting a line as you have already done gets even better:



The Spectrum analyser was reference locked to the rubidium clock @10MHz for these measurements.

The FSRs of the arms

X arm = 3.9671e+06 +/- 4.8535e+03 Hz

Y arm = 3.9648e+06 +/- 1.1064e+03 Hz


1&2. Plots representing the arm scans showing the beat frequency for which IR resonates in the arm vs the ALS offset (position of the ETM).

3. Data and code (zip file)

P.S. We had trouble scanning the arms using ALS. This was because the slow servo was not enabled. Hence ALS was losing its PDH lock everytime we scanned past a couple of FSRs.

Attachment 1: Xarm.png
Attachment 2: Yarm.png
Attachment 3: 40mCavLength.zip
  14268   Fri Nov 2 16:42:31 2018 aaronUpdateComputer Scripts / Programsarm loss measuremenents

I'm continuing the arm loss measurements Yuki was making. I'm first familiarizing myself with the procedures for the measurement Johannes describes.

I'm not very familiar with the medm screens, so I'm just kind of poking around and checking with Gautam. I do the following:

  1. Turned Xarm ASS dither on, then off.
  2. Turned X and Y ALS on, then off shortly after
    1. Realizing I needed some guidance, I found this page on lock acquisition on the wiki
    2. Gautam showed me how to align/lock the IFO so I could take some notes, and we locked the Y arm, misaligned X.
  3. I put the PD back in the AS beam path to get the ASDC signal, and approximately centered the beam. This PD is on channel 1 of the scope, which is at
  4. I centered the beam onto the MC2 PD that Yuki had installed. This PD is on channel 2 of the scope.
    1. Both scope channels are set to 1V scale (I also had tried 500mV, and it didn't seem to make a difference) and 10s time axis spacing (maximum integration time, since we're looking for a DC effect. Is this what we want?)
    2. The impedance for both channels is 1MOhm.
  5. I ran the script to start the loss measurement on the Y arm.
    1. python2 armloss_dcrefl_asdcpd_scope.py 1 2 5 YARM
    2. I'm reading ~15 (au?) for the MC channel and ~5% of that out the AS, which seems to make sense to me and looked to be about what Yuki the ratios when I checked the log files. However, I'm a bit confused by the normalization, because the maximum output of the MC PD is 10V, and indeed the scope's display is reading under 10V.

I've left the script running.

  14270   Mon Nov 5 13:52:18 2018 aaronUpdateComputer Scripts / Programsarm loss measuremenents

After running this script Friday night, i noticed Saturday that the data hadn't saved. Scrolling up inthe terminal, I couldn't see where I'd run the script, so I thought I'd forgotten to run it as I was making last minute changes to the scope settings Friday before leaving.

Monday it turns out I hadn't forgotten to run the script, but the script itself was getting hung up as it waited for ASS to settle, due to the offset on the ETM PIT or YAW setpoints. The script was waiting until both pitch and yaw settled to below 0.7, but yaw was reading ~15; I think this is normal, and it looks like Yuki had solved this problem by waiting for the DEMOD-OFFSET to become small, rather than just the DEMOD signal to be small. Since this is a solved problem, I think I might be using an old script, but I'm pretty sure I'm running the one in Johannes' folder that Yuki is referencing for example here. The scripts in /yutaro_scripts/ have this DEMOD-OFFSET functionality commented out, and anyway those scripts seem to do the 2D loss maps rather than 1D loss measurements.

In the meantime I blocked the beams and ran the script in DARK mode. The script is saving data in /armloss/data/run_20181105/, and runs with no exceptions thrown.

However, when I try to dither align the YARM, I get an error that "this is not a degree of freedom that has an ASS". I'm alsogetting some exceptions from MEDM about unavailable channels. It must have been something about donatella not initializing, because it's working on pianosa. I turned on YARM ADS from pianosa. Monitoring from dataviewer, I see that LSC-TRY_OUT has some spikes to 0.5, but it's mostly staying near 0. I tried returning to the previous frozen outputs, and also stepping around ETMY-[PIT/YAW] from the IFO_ALIGN screen, but didn't see much change in the behavior of LSC-TRY. I missed the other controls Gautam was using to lock before, and I've also made myself unclear on whether ASS is acting only on angular dof, or also on length.

I unblocked the beams after the DARK run was done.

  14274   Tue Nov 6 10:19:26 2018 aaronUpdateComputer Scripts / Programsarm loss measuremenents

I'm checking out the data this morning, running armloss_AS_calc.py using the parameters Yuki used here.

I made the following changes to scripts (measurement script and calculator script)

  • Included the 'hour' of the run in the armloss_dcrefl_* script. This way, we can run more than once a day without overwriting data.
  • Changed the calculator script to loop over all iterations of locked/misaligned states, and calculate the loss for adjacent measurements.
    • That is, the measurement script will make a measurement with the arm locked, then with it misaligned, and repeat that N times
    • The calculator now finds the loss for the nth iteration using *_n_locked and *_n_misaligned, and finds N separate loss measurements
    • The dark signal is also computed N times, though all of the dark measurements are made before running the arm scripts, so they could be all integrated together.
    • All of these are saved in the same directory that the data was grabbed from.

I repeated the 'dark' measurements, because I need 20 files to run the script and the measurements before had the window on the scope set larger than the integration time in the script, so it was padded with bad values that were influencing the calculation.

On running the script again, I'm getting negative values for the loss. I removed the beamstops from the PDs, and re-centered the beams on the PDs to repeat the YARM measurements.

  14280   Wed Nov 7 05:16:16 2018 yukiUpdateComputer Scripts / Programsarm loss measuremenents

Please check your data file and compare with those Johannes made last year. I think the power in your data file may have only three-disits and flactuate about 2%, which brings huge error. (see elog: 40m/14254)


On running the script again, I'm getting negative values for the loss. 

  5077   Sun Jul 31 22:35:35 2011 kiwamuUpdateLSCarm loss measurement : done

I did the measurement of the arm loss on both X and Y arm by running the armLoss script.

The results will be posted later.

Quote from #5074

I will measure the loss on the X and Y arm cavity tomorrow.


  5359   Wed Sep 7 16:21:35 2011 kiwamuUpdateLSCarm loss measurement : resluts

Here are the results of the arm loss measurements, which I have done before the vent.

I ran the existing matlab script, called 'armLoss.m', to estimate the loss. The script resides in /scripts/LSC.

(Y arm)

 Round trip loss =  154.668624 +/- 11.343204 ppm


The figure above is a time series of the measurement.

In the lower plot the power in the ASDC_PD are plotted. The green dotted-curve is the power when the Y arm is unlocked.

The blue dotted-curve is the one when the Y arm is locked.

In the upper plot the estimated loss from each combination of locked/unlocked power are plotted.


(X arm)

Round trip loss = ????? 50 ppm ?????

The obtained time series looked wired because difference in the ASDC power when the arm was locked/unlocked were small.

This small difference results in such a small loss.

To see what was going on I will look at the trend data.


Quote from #5077

I did the measurement of the arm loss on both X and Y arm by running the armLoss script.

The results will be posted later.


  1557   Thu May 7 18:12:12 2009 peteUpdateLockingarm power curve

I've plotted TRX, TRY, PD12I and PD11Q.  Arm powers after locking increase for a few tens of minutes, peak out, and then decrease before lock is lost.



Attachment 1: 2009_may_7_powers.jpg
  1558   Thu May 7 23:21:04 2009 peteUpdateLockingarm power curve


I've plotted TRX, TRY, PD12I and PD11Q.  Arm powers after locking increase for a few tens of minutes, peak out, and then decrease before lock is lost.



 I should have mentioned that the AS port camera image seems to get progressively uglier over the course of these locks.  Maybe we can use the JoeCam to make a movie of it. 

ELOG V3.1.3-