Displaying reports 77921-77940 of 83528.Go to page Start 3893 3894 3895 3896 3897 3898 3899 3900 3901 End
Reports until 16:29, Wednesday 13 March 2013
H1 General
hernan.daveloza@LIGO.ORG - posted 16:29, Wednesday 13 March 2013 (5783)
Operator summary

- 12:00 water sampling

- no safety meeting

- Patrick turn on DUST EX monitor

- PSL ENV alarms were on, and still on, for several days

- EY laser hazard

- Rick gave T.K. Machine's crew a tour
    13:30 LSB
    15:00 - 15:20 LVEA
    15:25 roof

- Dave and me with Ski consent, changed the MAX value of the channels
    H0:FMC-MX_AH_COOLTEMP_1_DEGF
    H0:FMC-MX_AH_COOLTEMP_2_DEGF
from 75F to 80F

- 16:30 LVEA transition to laser hazard

LHO VE
kyle.ryan@LIGO.ORG - posted 16:25, Wednesday 13 March 2013 (5782)
BSC5 dome leak
Today I vented X-end -> An Apollo crew (Mark L., Chris, Scott) removed BSC5's dome and found an insect on the underside of the outer O-ring at the exact point that I had marked as the leak location -> They lifted up this portion of the outer O-ring +/- 1' in either direction, removed the offending insect and wiped down the O-ring with an alcohol wipe -> During an overall visual inspection they also noticed a cut "sliver" of O-ring at a non-leaking location but this cut was not on the portion of the O-ring that comes in contact with the sealing surface and they left it be -> I pumped down the annulus volume following the dome's re-installation and helium leak tested only the area addressed -> No response (1 x 10-8 torr*l/sec baseline) -> This is encouraging but inconclusive as new leaks may have resulted from the dome's removal/installation -> I'll know more tomorrow.
H1 SUS
jeffrey.kissel@LIGO.ORG - posted 16:14, Wednesday 13 March 2013 (5781)
(salt grain) H1TMSY Damping Loops Commissioned Better (salt grain)
J. Kissel

With the TMS in it's current rubbing state, it's difficult to properly model any damping loop design based on the measured transfer functions -- and as you know, we don't yet have a dynamical model that we trust to design on instead. But, I did so anyways, and discovered that the loops really just needed their gains adjusted. Some degrees of freedom had no open loop gain above unity, others had way way way to much open loop gain, and were just down-right unstable.

Here're the changes to the damping loops:
(1) Included a "from_um" or "from_urad," which takes out the "to_um" calibration of the sensors, so we can stick with the otherwise-normalized filter design. These are in FM5, like every other type of the suspension (which is usually poorly named "norm").
(2) Turned the ELF10 elliptic filter back on, as was the original design intent. 
(3) Changed the gains from [L,T,V,R,P,Y] = [-20.0; -7.0; -10.0; -20.0; -5.0; -5.0] to [-20.0; -10.0; -20.0; -0.05; -0.5; -0.1]. (These new gains are also now roughly consistent with the ratios between DC magnitude (i.e. the stiffness) what's seen in the transfer functions).

I attach the modeled open loop gain and suppression for each degree of freedom with the new gains I've installed. Note, I intentionally removed the phase subplot because the data is so noisy / incoherent, I couldn't trust anything regarding phase margins, and flew by the seat of the modeled closed loop gain and suppression magnitude to help me determine where the stability regions lie.

If you're interested in using the scripts to make these plots in the future, they live in
${SusSVN}/sus/trunk/TMTS/Common/FilterDesign/
design_damping_L_TMTS_20130313.m
design_damping_P_TMTS_20130313.m
design_damping_R_TMTS_20130313.m
design_damping_T_TMTS_20130313.m
design_damping_V_TMTS_20130313.m
design_damping_Y_TMTS_20130313.m
Non-image files attached to this report
H1 SUS
jeffrey.kissel@LIGO.ORG - posted 12:51, Wednesday 13 March 2013 - last comment - 13:16, Wednesday 13 March 2013(5778)
H1SUSTMSY -- Still Rubbing
J. Kissel, (for K. Kawabe, K. Izumi, and T. Sadecki)

Team TMS + Travis ventured down to the y-end this morning in hopes to discover some obvious source of rubbing, which I'd reported a few days ago (see LHO aLOG 5768). Unfortunately, they didn't find anything. They did adjust the alignment/centering on a few of the BOSEMs (they didn't say which), because only because they looked suspicious. I've taken a new set of transfer functions, and I see little to no change. The best "improvement" is that the three Transverse modes look more like the model -- but the model still comes with many grains of big'ol kosher salt, and the high-frequency noise (for this DOF) looks much worse. I'll continue to push forward on a "new" damping loop design (more likely I'll just model the damping with the measured TFs, asses where things are going unstable, and move around some poles or zeros if need be), in parallel with further investigations of rubbing.

Note: Mark made some improvements to the model this morning -- mostly related to making sure the coordinate system is as expected by the model (it's a whole confusing mess between the SolidWorks XYZ, the Dynamical Model's XYZ, and the Euler Control Basis -- especially since the top mass is the same as a QUAD top mass but rotated 90 [deg] with respect to Dynamical Model expects. Not to mention left-handed vs. right-handed TMTSs). We *think* we've got them correct at the moment, but the only way we can be sure is by opening up SolidWorks and checking (where Mark and I only have the eDrawings).
Non-image files attached to this report
Comments related to this report
kiwamu.izumi@LIGO.ORG - 13:16, Wednesday 13 March 2013 (5779)

Thanks, Jeff. The BOSEMs that Travis adjusted were : two top OSEMs and side OSEM.

LHO VE
john.worden@LIGO.ORG - posted 10:50, Wednesday 13 March 2013 - last comment - 08:09, Saturday 16 March 2013(5777)
Beam Tube Insulation photos

I walked about 300 meters of Y1 this week and took some photos of the beam tube insulation.

Between ports 2 and 3 (a distance of 250m) I counted 35 holes in the insulation. Virtually all of these holes were at taped joints between insulation wraps. These joints occur every 4 feet.

So of 800 taped joints I saw 35 which were violated by rodents. There may have been a few more on the backside of the tube. The photos in this report show some of the holes, some of the "good" taped joints, and some views of the uninsulated bellows regions.

Images attached to this report
Comments related to this report
john.worden@LIGO.ORG - 08:09, Saturday 16 March 2013 (5828)

Thursday I looked into X1 and X2 (but not Y2) specifically to see if the bellows are insulated. It looks like they are so Y1 may be unique in this regard. However, the insulation is pretty ragged and will need to be scrapped.

H1 SUS
arnaud.pele@LIGO.ORG - posted 10:04, Wednesday 13 March 2013 (5776)
PR2 power spectra check after alignment

PR2 (installed in HAM3 chamber) power spectra have been taken after yesterday's gross alignment.

The figures attached show a comparison for PR2 damped and undamped between :

-LLO Phase 3a  (Mai 2012) purge-air off, ham3 door closed

-LHO Phase 3a (October 2012) ham3 doors open and covers on

-LHO Phase 3a (March 2012) ham3 doors open covers off with M2 and M3 OSEM out

Looking at M1 DOFs of the undamped spectra, the resonnances are consistent with LLO and LHO previous measurements.

An other spectra will be taken after the fine alignment.

Non-image files attached to this report
LHO VE
john.worden@LIGO.ORG - posted 09:21, Wednesday 13 March 2013 (5775)
Y1 Accumulation - Leak in GV6 annulus.

After performing another accumulation on Y1 with CP1 isolated from the tube we think we have found our leak. It looks like the annulus of the gate seal has a leak into the system.

This was highlighted when we reopened GV6 after the accumulation.

So in summary the outgassing from Y1 appears to be in line with the 3 other modules, the CP1 outgassing rate is reasonable and we have a leak to follow up on.

SUMMARY:

LHO Module      Total Outgassing     Outgas rate/unit area          Hydrogen              Date         Outdoor Temps      Post Bake(1998) H2 at 23C             at 0C

                                 torr- l/sec                    torr-l/s/cm^2                     torr-l/s/cm^2                              high/low  C              torr-l/s/cm^2

Y1*                            5 e-7                              6.8 e-15                         1.7 e-14                   Mar 12       16/4                             6.3 e-14                                     9.0 e-15

Y2                             2.4 e-7                          3.3 e-15                          8.25 e-15                Mar 6          5/1.1                             4.7 e-14                                    6.8 e-15

X1                             5.4 e-7                          7.3 e-15                          1.83 e-14                Mar 7          12.2/3.3                        5.2 e-14                                    7.4 e-15

X2                             3.4 e-7                          4.6 e-15                          1.2 e-14                   Mar 8          12.2/1.1                        4.6 e-14                                   6.6 e-15

 

Volume of each module ~ 2.35 e6 liters

Area of each module  ~ 7.35 e7 cm^2   (excludes baffles and port hardware)

Gauge factor for cold cathode and H2 = 2.5

Note that each module accumulation includes the 80k pumps at either end - a significant surface area of untreated SS with H2 outgassing of perhaps 100x that of the beam tube steel(per unit area).

Y1 result is estimated from the sum of two accumulations(tube + CP1) performed on Mar 12.

NOTE: If you subtract the outgassing due to CP1 or CP2 from the Y1 and X1 results you will get numbers much closer to the Y2 and X2 modules. The measured outgassing from CP1 is 2.3 e-7 tl/s.

Images attached to this report
H1 ISC
keita.kawabe@LIGO.ORG - posted 22:31, Tuesday 12 March 2013 - last comment - 14:15, Friday 15 March 2013(5774)
50-50 IR beam splitter is a good AR for green (Corey, Keita)

Seems like the problem we had when using a green beam reflected off of a 50-50 IR beam splitter was because of the fact that 50-50 surface for 1064nm works as a very good AR for 532nm.

The BS in question is this: https://dcc.ligo.org/LIGO-E1000671-v1

Corey used a fiber coupled green laser as the source, placed a PBS cube for 532nm to ensure that the P-pol light is transmitted, and used a HWP for 532nm to change the polarization.

There are two beams in reflection, one from 50-50 IR BS surface and one from the back surface. There is one beam spot in transmission, because the 50-50 IR BS surface is very small. Anyway:

  P-pol S-pol
50-50 IR surface reflection 0.92% 0.044%
AR surface reflection 6.3% 20.7%
Transmission 92% 79%

On TMS ISC table (and in the arms) the green light has S-polarization, and according to Corey's measurement we're totally screwed.

Now that we know about this, we could either align the red QPD path assuming that there is an invisible beam next to a visible beam at a known distance, or we could place a HWP on the ALS table and inject a wrong polarized beam to see if we get anything.

Corey will write a one-page document and add it to E1000671.

Comments related to this report
corey.gray@LIGO.ORG - 14:15, Friday 15 March 2013 (5819)

Note added to E1000671v1 is here.

LHO General
patrick.thomas@LIGO.ORG - posted 21:11, Tuesday 12 March 2013 (5773)
plots of dust counts
Attached are plots of dust counts > .3 microns and > .5 microns in particles per cubic foot requested from March 12 00:00 UTC to March 13 00:00 UTC. Also attached are plots of the modes to show when they were running/acquiring data.

Data was taken from h1nds1.
T0=13-03-12-00-00-00; Length=86400 (s)
4020 seconds worth of data was unavailable on this server
1440.0 minutes of trend displayed
Non-image files attached to this report
LHO General
patrick.thomas@LIGO.ORG - posted 20:57, Tuesday 12 March 2013 (5759)
Ops Summary
Richard to end Y to look at seismometer
John to mid Y to close GV 10
Rebuild of h1susmc2 against unmodified 2.6.2 RCG code, restarted
LN2 CP7 fill
restarts of corner station PEM, DAQ restart
alignment work in HAM3
restart of mid X PEM, end Y PEM
Richard re-zeroed STS2 seismometer, removed tilt-meter from PEM at end Y
h1slow-cds gateway restarted
H1 IOO
chris.mueller@LIGO.ORG - posted 20:21, Tuesday 12 March 2013 - last comment - 20:34, Tuesday 12 March 2013(5771)
Input Optics Work
[Rodica M., Deepak K., Chris M.]

Today we resolved the issue with IM3 which turned out to be an earthquake stop rubbing.  It isn't clear how this became an issue after pumping down, perhaps it slipped in over time.  See the attached transfer functions for an idea of the badness and subsequent goodness.  

After we were allowed to turn on the laser we double checked the centering on the IMC mirrors which seems very good to us.  We added an iris at MC2 to double check the 'by eye' centering which was done at the end of last week, and the beam looked very good.  We also installed the MC2 scraper baffle.  

Tomorrow we will check the alignment of the components downstream of the IMC.  Afterwards we will align the MC refl beam onto the trans beam path and use it to align the auxiliary paths and measure mirror transmissivities.
Non-image files attached to this report
Comments related to this report
deepakmanoj.nandakumar@LIGO.ORG - 20:34, Tuesday 12 March 2013 (5772)

The Dog clamps installed on the MC2 Scraper Baffle are 

  • D1100640-V2 Type 03 - S.N. 009.
  • D1100640-V2 Type 03 - S.N. 010.
  • D1100640-V2 Type 03 - S.N. 011.
  • D1100640-V2 Type 03 - S.N. 012.
H1 SUS
arnaud.pele@LIGO.ORG - posted 17:14, Tuesday 12 March 2013 (5770)
OMC cart2eul and eul2cart matrices

Jeff K., Arnaud P.

Filled up the CART2EUL and EUL2CART matrices for OMC. 

CART2EUL=

                    0.8572                     0.515                   -0.1402                         0                    -0.538                    0.8954
                    -0.515                    0.8572                    0.0094                         0                   -0.8954                    -0.538
                         0                         0                         0                         1                     0.125                    0.0642
                         0                         0                         0                         0                    0.8572                     0.515
                         0                         0                         0                         0                    -0.515                    0.8572
                         0                         0                         1                         0                         0                         0

EUL2CART=

                    0.8572                    -0.515                         0                   -0.5379                   -0.8954                     0.125
                     0.515                    0.8572                         0                    0.8954                   -0.5379                    0.0641
                         0                         0                         0                         0                         0                         1
                         0                         0                         1                   -0.1402                    0.0093                         0
                         0                         0                         0                    0.8572                    -0.515                         0
                         0                         0                         0                     0.515                    0.8572                         0

The values are saved in the /opt/rtcds/userapps/release/isc/common/projections folder under ISI2SUS_projection_file.mat.

In order to get those matrices we updated the script SEI2SUScoordinates.m with relative coordinates between OMC and the center of the ISI table (from the attached bgchbiai.png and HAM6[...].pdf for x, y, yaw and the solidwork screenshot for z from dcc document D0900295).

x=-64.197mm

y=125.01mm

z=637.08mm

yaw=31 degrees

A new snapshot with safe values has been commited on the svn as well as the ISI2SUSprojection_file.mat file.

Images attached to this report
Non-image files attached to this report
LHO VE
kyle.ryan@LIGO.ORG - posted 16:45, Tuesday 12 March 2013 (5769)
GV10, GV6 stroked
John -> Hard-closed GV10 
Kyle -> Soft-closed GV6 
Kyle -> Opened GV10 
Kyle -> Opened GV6 

Y1 accumulation study -> looks like gas load is GV6 gate annulus air leak -> John will post data soon
H1 SUS
jeffrey.kissel@LIGO.ORG - posted 16:23, Tuesday 12 March 2013 (5768)
H1 SUS TMSY Top 2 Top Transfer Functions -- SUS Style
J. Kissel, (S. Steplewski)

After putting in the effort of "cleaning up" the infrastructure for H1SUSTMSY (see LHO aLOG 5754), I've taken M1 to M1 (Top2Top) transfer functions, in hopes that Double Model (including a parameter file built by Szymon and myself) we put together would match the measurement as beautifully as the rest of the SUS and their models. 

Attached are the results; no such luck. (Queue sad trombone).

Szymon took a data set before the makeover (shown in orange), with the damping loops closed, so the data definitely won't match up with any model (especially the rotational degrees of freedom), but I plot it anyway to see if we can pull out any useful information comparing it the current data. The current data (in black) was taken last night, after the makeover, with damping loops open.

Since all three show totally different things, it's difficult to know which to trust. However, I'm 90% confident that the current data shows there's rubbing present in the suspension. My reasoning is as follows:
- Driving as hard as I can without saturating, but still see very noisy, poorly coherent data up to 1 Hz, if not higher
- Resonant modes of independent degrees of freedom are seen in each others TF; e.g. ~3.5 Hz Y mode visible in R, T, and L, or 
- Vertical and Yaw modes -- typically very mechanically stable (read: hard to screw up) show noisey/muted resonances peaks

This rubbing might be the source of Keita's complaints that the damping was unstable to increasing the gain. I'd really like to resolve the rubbing issues before I go any further on redesigning the damping loops -- because they may just not need it.

LHO aLOG 1825 is the best thing I can find regarding previous "accepted" transfer functions, and regardless of that the resolution is low, and the measurement frequency band is less, I think it's still pretty clear that those former transfer functions are much cleaner than what I've measured.

I've spoken with Kiwamu, and they'll begin the time-honored SUS tradition of finding sources of rubbing.

In the mean time, we'll continue to refine the model, such that they converge.

----------

As an aside -- you may recognize the format of the attached plots. This now means that there are functional aLIGO SUS standard analysis scripts that can process and compare data sets. Szymon had started writting them, and I've pushed them through to completion and full functionality. I've also begun building up the svn structure similar to other suspensions. As such, I describe everything:

The data was taken with DTT using the templates:
${SusSVN}/sus/trunk/TMTS/H1/TMSY/SAGM1/Data/
2013-03-11_0800_H1SUS-TMSY_M1_L_WhiteNoise.xml
2013-03-11_0800_H1SUS-TMSY_M1_P_WhiteNoise.xml
2013-03-11_0800_H1SUS-TMSY_M1_R_WhiteNoise.xml
2013-03-11_0800_H1SUS-TMSY_M1_T_WhiteNoise.xml
2013-03-11_0800_H1SUS-TMSY_M1_V_WhiteNoise.xml
2013-03-11_0800_H1SUS-TMSY_M1_Y_WhiteNoise.xml

exported in the format L_EXC to F1, F2, F3, LF, RT, SD, L, T, V, R, P, Y in the files
${SusSVN}/sus/trunk/TMTS/H1/TMSY/SAGM1/Data/
2013-03-11_0800_H1SUSTMSY_M1_L_WhiteNoise_tf.txt
2013-03-11_0800_H1SUSTMSY_M1_P_WhiteNoise_tf.txt
2013-03-11_0800_H1SUSTMSY_M1_R_WhiteNoise_tf.txt
2013-03-11_0800_H1SUSTMSY_M1_T_WhiteNoise_tf.txt
2013-03-11_0800_H1SUSTMSY_M1_V_WhiteNoise_tf.txt
2013-03-11_0800_H1SUSTMSY_M1_Y_WhiteNoise_tf.txt

then individually processed into
${SusSVN}/sus/trunk/TMTS/Common/MatlabTools/plotTMTS_dtttfs.m

which saves a .mat file in a standard format and place,
${SusSVN}sus/trunk/TMTS/H1/TMSY/SAGM1/Results/2013-03-11_0800_H1SUSTMSY_M1.mat
and produces the "individual measurement" plots attached, 2013-03-11_0800_H1SUSTMSY_M1_ALL_TFs.pdf

This file can then be picked up and compared with other measurements by
${SusSVN}/sus/trunk/TMTS/Common/MatlabTools/plotalltmts_tfs.m

which produces the "measurement collection" plots attached, alltmtss_2013-03-11_H1SUSTMSY_ALL_ZOOMED_TFs.pdf 

All of the above are committed to the SusSVN for your future use!
Non-image files attached to this report
H1 INS
jodi.fauver@LIGO.ORG - posted 14:23, Tuesday 12 March 2013 (5765)
X End status
Assembly of Buffer cleanroom completed and cleanroom moved into place.

Randy and I checked to see what preparations were needed to facilitate ETMX install and discussed a possible sequence of events. Below is a first attempt at a checklist.Please email me any additions/corrections and I will post this checklist periodically.

1. Find BSC5 dome leak (Apollo)-In progress
2. Install Work Platforms at BSC9/Walking Plates setting on Work Platforms? (Apollo/Jodi)
3. Move BSC cleanroom over BSC9 (Apollo)
4. Assemble and place E-module including upper garbing/staging cleanroom (Apollo/Jodi)
5. Determine test stand location (IAS/Michael L./Jodi)
6. Get BSC ISI and Quad into VEA (SEI/SUS/Apollo)
7. Assemble Test Stand cleanroom (Apollo)
8. Move Work Space cleanroom into VEA/Nest cleanrooms (Apollo)
9. Get engine hoist into VEA? (Apollo)
10. Assemble Test Stand (Apollo)
11. Level Test Stand (IAS?)
12. Gross clean Test Stand (Tech Cleaners)
13. Place lower level support cleanrooms-Test Stand, Work Space, Garbing/Staging (Apollo)
14. Clean all cleanrooms (Tech Cleaners)
15. Move ISI to Test Stand (SEI/Apollo)
16. Level, balance and test ISI (SEI)
17. Marry SUS to ISI (SUS/Apollo)
18. SUS check-out (SUS)
19. Remove dome and doors (Apollo)
20. Install cartridge (SEI/Apollo)
H1 INS
jodi.fauver@LIGO.ORG - posted 13:56, Tuesday 12 March 2013 (5764)
BSC5 Leak Hunt
Soft roof was installed in the morning. First and second cleanings were accomplished by early afternoon. 
LHO VE
john.worden@LIGO.ORG - posted 14:31, Monday 11 March 2013 - last comment - 15:58, Tuesday 12 March 2013(5742)
Beam Tube Module Accumulation Summary

 

LHO Module      Total Outgassing     Outgas rate/unit area          Hydrogen              Date         Outdoor Temps      Post Bake(1998) H2 at 23C             at 0C

                                 torr- l/sec                    torr-l/s/cm^2                     torr-l/s/cm^2                              high/low  C              torr-l/s/cm^2

Y1                            1.3 e-6                          1.77 e-14                         4.4 e-14                   Mar 5         7.2/0                        6.3 e-14                                     9.0 e-15

Y2                             2.4 e-7                          3.3 e-15                          8.25 e-15                Mar 6          5/1.1                        4.7 e-14                                    6.8 e-15

X1                             5.4 e-7                          7.3 e-15                          1.83 e-14                Mar 7          12.2/3.3                        5.2 e-14                                    7.4 e-15

X2                             3.4 e-7                          4.6 e-15                          1.2 e-14                   Mar 8          12.2/1.1                        4.6 e-14                                   6.6 e-15

 

Volume of each module ~ 2.35 e6 liters

Area of each module  ~ 7.35 e7 cm^2   (excludes baffles and port hardware)

Gauge factor for cold cathode and H2 = 2.5

Note that each module accumulation includes the 80k pumps at either end - a significant surface area of untreated SS with H2 outgassing of perhaps 100x that of the beam tube steel(per unit area).

A quick estimate of the SS surface in the long pump is 285,000 cm^2.  If you assume 100 times the H2 outgassing this yields an equivalent 2.8 e7cm^2 or 1/3 of the beam tube. The internals of the pump are largely aluminum and likely do not contribute to the H2 outgassing.

Comments related to this report
rainer.weiss@LIGO.ORG - 20:26, Monday 11 March 2013 (5755)
Current temperatures are in F not C
john.worden@LIGO.ORG - 20:36, Monday 11 March 2013 (5756)

80K pump contribution added, fixed degrees C.

 

john.worden@LIGO.ORG - 15:58, Tuesday 12 March 2013 (5767)

Second accumulation on Y1 March 12 with 80K pump CP1 isolated:

We have two accumulations - one for the 80K pump and one for the Y1 module.

CP1 outgassing:

Estimated volume of CP1 including one gate valve interior = 22,800 liters

Estimated surface area of SS of CP1 plus valve = 285000 cm2

Pressure rise in 8700 seconds = 8.9 e-8 torr = 2.3 e-7 t-l/sec    x gauge factor of 2.5 = H2 outgassing of 2.1 e-12 tl/s/cm^

Y1 Module:

Outgas rate without CP1 is now 2.63e-7 e-7 t l/s or 1/5 of what it was before. On the other hand summing the two yields ~5 e-7 tl/s rather than the 1.3 e-6 obtained a few days ago.

Perhaps this is an indication of our measurement error. Arithmetic error?

Images attached to this comment
H1 IOO
rodica.martin@LIGO.ORG - posted 20:13, Friday 08 February 2013 - last comment - 15:47, Wednesday 13 March 2013(5439)
IMC length measurement

[Paul, Kiwamu, Keita, Dick, Rodica]

Today we measured the mode cleaner cavity length by modulating the EOM at 45 MHz and doing a sweep around this frequency. We measured the spectrum using an HP 43968 Spectrum Analyzer. The maximum source power was 19 dBm from a Mini-Circuits RF amplifyier with gain 19 dB. The bandwidth for the highest zoom on the peak was 300 Hz.

The frequency of the dip in the middle should correspond to the 5th FSR away from the carrier resonance. The calculated length is 9.09918 MHz +/-  100 Hz, only 291 Hz away from the design value of 9,099,471 Hz. This is equivalent to 1.05 mm difference from the design length.

We tried a full sweep over one FSR but we realized that the modulation away from resonance would be too small to give us any useful results, so we focused on the 45 MHz resonant peak. Attached is a plot of the data over a full FSR, that also shows a peak corresponding to the non-resonant polarization, and few other peaks possibly due to higer order modes.

Similar measurements at LLO are described in alog 4702.

Non-image files attached to this report
Comments related to this report
keita.kawabe@LIGO.ORG - 15:47, Wednesday 13 March 2013 (5780)

Just to add some redundant information, the measured FSR of 9.09918MHz +-100Hz corresponds to:

 half-roundtrip = 16.4736m+-0.2mm.

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