ELOG 40m

ETMY and PRM have EQ related problems

The attached trend shows that ETMY and PRM both had large steps in their sensors
around the time of the EQ and didn't return afterwards. The calibration of the
OSEM sensors is ~0.5 mm/V. The PRM sensors respond when we give it huge biases
but there is very little change in the ETMY. Almost certainly true that the
optics have shifted in their wire slings and that we will have to vent to
examine and repair at least ETMY.

Jenne is looking at the spectra of the other suspensions to see if there is
other more subtle issues.

Attachment 1: Untitled.png

756

Tue Jul 29 14:38:02 2008

rob

ETMY and PRM have EQ related problems

Quote:

Some additional notes/update:

ETMY, PRM, & MC2 had OSEM signals at a rail (indicating stuck optics). Driving the optics with full scale DAC output freed ETMY and MC2, so while these may have shifted in their slings it may be possible to avoid a repair vent. PRM is still stuck. One OSEM appears to respond with full range to large drives, but the other three face OSEMS remain disturbingly near the rail (HIGH, which is what would happen if a magnet fell off).

757

Tue Jul 29 18:15:36 2008

I used the SUS DRIFT MON screen to return the MC suspensions to near their pre-quake values. This required fairly large steps in the angle biases. Once I returned to the printed values on the DRIFT screen (from 3/08), I could see HOM flashes in the MC. It was then pretty easy to get back to a good alignment and get the MC locked.

758

Tue Jul 29 19:41:38 2008

FSS loop transfer functions

PSL

Last night I measured a bunch of transfer functions on the FSS loop.
All the loop gains were measured with the common gain = 30db and the fast gain = 18dB.

(1) The first attachment is the overall open loop transfer function of the FSS loop. I put a signal from the Test IN2 and observed signals from IN1 and IN2.
The UGF is about 180kHz.
By increasing the RF amplitude going to the EOM (i.e. increasing the sideband power), I can further increase the gain of the servo.
However, it made the PC drive immediately crazy. Probably it was some oscillation.

(2) Then I locked the ref. cav. with only the PZT actuator. I did so by simply unplugging the cable going to the PC.
Surprisingly, the cavity locked with the *same* gain setting as before. The second attachment shows the open loop transfer function measured in this configuration. It seems wrong, I mean, it should be unstable. But the cavity locked. A mystery.

(3) The third plot is the measured TF from the Test IN1 of the FSS board to the fast out (output to the PZT).

(4) By dividing the TF measured in (2) with the TF of (3), I got the response of the PZT times the cavity response. This is shown in the attachment 4.

(5) We can guess the open loop TF of the PC path by subtracting the TF in (2) from (1). It is shown in the attachment 5.

(6) The filter shape of the PC path is measured by injecting signal from the Test IN1 of the FSS board and observing it at the PC output. Since it is a high voltage output, I reduced the common gain to -8.5dB during the measurement. The attachment 6 is the measured filter shape. The gain is corrected to show what it should look like when the common gain = 30dB.

(7) By dividing (5) with (6), I plotted the response of the PC times the cavity response in the attachment 7. Since the 1/f cavity pole and the response of the PC, which is proportional to f, should cancel out, we expect a flat response above the cavity pole frequency (38kHz). You could say it is a sort of flat, if you have obscured eyes.

The measurement of the PZT open loop TF is very suspicious. According to this, the PC path has a very large gain even at very low frequencies (there is no cross over above 1kHz). This cannot be true. Maybe the cavity's optical gain was low when it was locked with only the PZT. I will re-measure it.
The plot (4) is also strange becaues it does not show the low pass feature expected from the cavity pole.

Attachment 1: OverallOPLTF.eps

Attachment 2: OpltfPZTOnly.eps

Attachment 3: PZTFilter.eps

Attachment 4: PZTxCavityPole.eps

Attachment 5: OpltfPCOnly.eps

Attachment 6: PCFilter.eps

Attachment 7: PCxCavityPole.eps

759

Tue Jul 29 19:53:19 2008

PRM photos from the south window

Steve and Koji

We took some photos of PRM from the south window.
You can see one of the side magnets, a wire stand-off, and the wire itself from the round hole.
So, the wire looks OK.

For the coils, we could see only one coil. The magnet is apparently too high.

Attachment 1: PRM_from_South_Window1.jpg

Attachment 2: PRM_from_South_Window2.jpg

760

Tue Jul 29 21:04:55 2008

OSEM's Power Spectrum

From 16:30 this afternoon

Attachment 1: ITMY2.JPEG

Attachment 2: ITMY.JPEG

Attachment 3: ITMX2.JPEG

Attachment 4: ITMX.JPEG

Attachment 5: ETMY2.JPEG

Attachment 6: ETMY.JPEG

Attachment 7: ETMX2.JPEG

Attachment 8: ETMX.JPEG

761

Tue Jul 29 23:04:34 2008

FSS loop transfer functions

PSL

Quote:

The measurement of the PZT open loop TF is very suspicious. According to this, the PC path has a very large gain even at very low frequencies (there is no cross over above 1kHz). This cannot be true. Maybe the cavity's optical gain was low when it was locked with only the PZT. I will re-measure it.

I measured it again and found that the loop was oscillating at 13.5kHz. I think this oscillation prevented the ref. cavity from building up the power and consequently lowered the optical gain making it marginally stable. So the PZT path open loop TF posted in the previous entry is wrong.

I was able to stop the oscillation by lowering the gain down to CG=-7.6dB and FG=-8.78dB.
The first attachment shows the measured open loop transfer function.
Since the gain setting is different from when the over all open loop TF was measured, I scaled the gain (attachment 2).
However, this plot seems to have too much gain. Scaling it down by 20dB makes it overlap with the over all open loop TF.
Maybe the gain reading on the EPICS screen is wrong. I will measure the actual gain tomorrow.

Attachment 1: OpltfPZTOnlyRaw.eps

Attachment 2: OpltfPZTOnly.eps

762

Wed Jul 30 00:42:04 2008

Trends and file formats

I propose that we do not use .eps format but .pdf instead. For images like the plots Sharon
has below we should use only .png and for pictures like what Steve posted, use JPG or PNG.

PDF is a standard and light weight. PNG is very good for plots/lines and is lossless. JPG does
a good job with regular camera pictures because we don't really care about the compression
loss on those.

Here's a trend of the UL sensors for all the optics - conversion is 32768 cts / mm. You can see
that the quake was just before 19:00 UTC (noon our time). The events an hour after are when
Rob, Jenne, and I start exciting the optics to shake them loose - wanging the pit/yaw sliders
around is not violent enough and so I injected a 130000 count sine wave at 0.5 Hz so as to
create a high force square wave. This seems to have worked for ETMY but no such luck yet with
the others.

Attachment 1: Untitled.png

765

Wed Jul 30 12:36:19 2008

Weekly update

This week included many computer's issues. I tested Alex's new C code (the one that saves the FIR coefficients and restores them when you start running the code again). Seems there is an improvement in the adaptation time, but not a significant one (more details on the coming report). I had to recompile simulink and the FB whenever I wanted to find a solution for taking the record of those coefficients. This is so I could simulate the adaptive filter with a regular IIR filter and compare the two.
After Rob tried to help and it seems to be an impossible to a huge hassle mission, we thought of a different method to do this. I re-compiled the old simulink file and restored the .ini file and all should be back in place. Instead of finding the FIR coefficients, I am going to use one noise source in the adaptive filter, stop the adaptation (by setting mu and tau to 0), and put excitation instead of the noise signal. The transfer function I will get between the exc. and MC1_IN1 is the filter I am looking for.

Also seems that whenever I get the MC unstable, and the adaptive code stops itself, it doesn't come back. Setting the reset flag to a different number (anything other than 0) and pressing the reset button will get it working again, but the CPU will always flip and the ASS computer needed a restart. Still haven't found a problem in the C code, but that's the plan. Moreover, I want to change Alex's code, so that instead of starting from zero like in Matt's code, or starting from the old coefficients like in Alex's, it is going to calculate a Wiener Filter as the first set of coefficients. This will hopefully reduce the adaptation time.

I have also been working on my progress report, and stood in line for the MC... Still standing...

766

Wed Jul 30 13:08:44 2008

Max Jones

Computer Scripts / Programs

Weekly Summary

This week I've been working on the noise budget script. The goal is to add Siesmic, Darm, Mich, Prc and magnetometer noise. I believe I've added Seismic noise in a reasonable and 40m specific manner (please see the attached graph). The seismic noise in the noise budget at 100 Hz was 10 times higher than that predicted by Rana in elog #718. This could be due to the fact that graph is taken from data today when the device is unlocked and construction workers are busy next door. I am currently trying to fix the getDarm.m file to add the DARM source to the noise budget. I have run into several problems, the most pressing of which was that the C1:LSC-DARM_ERR channel is zero except with the interferometer is being locked. According to Rob, we only save data for approximately a day (we save trends for much longer but this is insufficient for the noise budget script) and sometimes we are not locked the night before. Rob showed me how I may introduce an artificial noise in the DARM_ERR signal but I'm having trouble making the script output a graphic. I'm still unsure how to make the getDarm function 40m specific.

Today I will start working on my second progress report and abstract.

Attachment 1: C1_NoiseBudgetPlot.pdf

771

Wed Jul 30 15:28:08 2008

By using a combination of the SUS-DRIFT mon screen and the optical levers (which turned out pretty well) I steered the BS, ITMY, and ETMY back to their previous positions, and was able to lock the Y arm. The "Restore Y Arm" script on the IFO_CONFIGURE screen works. I couldn't test the alignment script, as a dump truck/construction vehicle showed up and started unlocking the MC.

772

Wed Jul 30 16:35:56 2008

Graphs of the PMC scan data that I got earlier today.

PMCLongScanWide.tiff shows the transmission intensity and PZT voltage plotted against time for a longer scan of the PMC (~120 seconds for one sweep).

PMCLongScanPeak.tiff is the same scan zoomed in on the primary peak. This scan was done with the laser power at around 1/3 its original value. However, scans done at around 1/6 the original value have peaks that are just as messy.

PMCShortScanWide.tiff shows the intensity and voltage for a more rapid scan (~30 second for one sweep). The black lines show how the peak positions are at very different PZT voltages (a difference of ~10 volts in both cases).

PMCShortScanPeak.tiff is zoomed in on the primary peak. The peak is much cleaner than for the long scan (less time for the laser's heat to expand the mirror?), though it is likely still too messy to reliably fit to a lorentzian.

Attachment 1: PMCLongScanPeak.tiff

Attachment 2: PMCLongScanWide.tiff

Attachment 3: PMCShortScanPeak.tiff

Attachment 4: PMCShortScanWide.tiff

774

Thu Jul 31 10:24:32 2008

Last night I used the Y-arm for the abs length measurement. The Yarm was aligned by the script.
I left the ifo with the Yarm locked as it is the only meaningful configuration so far.

775

Thu Jul 31 10:27:17 2008

Quote:

Graphs of the PMC scan data that I got earlier today.

On the UNIX computers, one can use 'convert' to change these to PNG. A DC offset should be added to the transmitted
light so that the scan can be plotted with a log y-scale. And, of course, Acrobat can be used to make it into a
single PDF file.

The PMC scan always has this distortion and so the input power has to be decreased to a few mW to reduce the
thermal expansion effect; the expansion coefficient for SiO2 is ~5 x 10^-7 / K and we're worried about nm level
expansions.

776

Thu Jul 31 11:19:30 2008

Abs. Len. Meas. ~ Resonance search trial

Last night, I tried to find the resonance of Yarm by sweeping the frequency of the injection beam.

A strong beat was present at LT_NPRO=48.7856[C_deg], the power coupling of the injection beam was estimated to be 35%. 
(Vmax_beat = 1.060[V], Vmin_beat = 0.460[V], Vno_inject = 0.664[V])

The Yarm was locked and the alignment script was executed. The PLL between the PSL beam and the injection beam was 
somehow locked.

I tried to scan the freq offset (f_PLL) at around 3.88MHz first, then at around 15.52MHz. They are supporsed to be the 
first and fourth FSR of the Yarm cavity. The Yarm transmitted power (DC) was observed to find the resonance of the 
injection beam. It would have been better to use the RF power, but so far I didnot have the RF PD prepared at the end 
transmission. I just used the DC power.

I think I saw the increase of the transmitted power by 10%, at f_PLL = 15.517 +/- 0.003 [MHz]. This corresponds to the 
arm cavity length of 38.640 +/- 0.007 [m]. The previous measurement was not so bad!

Y-arm length
e-log             length [m]
-----------------------
556(2008-Jun-24)  38.70    +/- 0.08    Cavity swinging measurement
556(2008-Jun-24)  38.67    +/- 0.03    tape & photo
This              38.640   +/- 0.007

However, I had difficulties to have more precise measurement mainly because of two reasons:
o The PLL servo is too naive, and the freqency stability of the inj beam is not enough.
  The injected beam should have the linewidth (=freq stability) narrower than the cavity linewidth.

o The PLL servo may experience change of the transfer function at around the resonance. The PLL works the other 
frequencies. However, close to the resonance, it starts to be unstable.

So the next stuffs we should do is 
o Build the PLL just using the incident beams to the ifo, not by the reflected beams.
o Build sophisticated servo to have better frequency stability.
o RF PD at the transmission.

Left the lab with Yarm locked, flipper down, shutter for the NPRO closed.

782

Sat Aug 2 12:53:43 2008

Abs. Len. Meas. ~ New PLL at the PSL table

Report of the work last night:
The new heterodyne interferometer on the PSL table was built.
The length of the Yarm cavity was measured with better precision.

-------------
Yarm is locked. The injection beam was aligned. The beat was there at around LT=48.9 [C_deg] of the NPRO.

The new PLL setup on the PSL table has been built. The two beams from the MC incident beam and the injection beam are
mode-matched with lenses. I measured the Rayleigh ranges of the beams by a sensor card and my eyes, and then placed
appropriate lenses so that they can have 5~6 [m] Rayleigh range. They looks a bit too thick but just ok for an inch
optics. The new PLL setup shows ~70% intensity modulation which is enormous. The servo is still SR560-based so far.

Now the PLL has no singular frequency within its range. I could sweep the 4th FSR of the cavity with 500Hz interval. I
was still observing at the transmitted DC.

At each freqency from 15.51MHz to 15.52MHz, a timeseries data of the Yarm transmitted was recorded at sampling of 32Hz for 10
seconds. The figure shows the averaged values of the transmitted DC with errors. An increase of the transmitted power by
3-4% was found. If we consider the resonance is at f_PLL = 15.515 +/- 0.0005 [MHz], this indicates the
arm cavity length of 38.6455 +/- 0.0012 [m].

Y-arm length
e-log    length [m]
-----------------------------
556      38.70   +/- 0.08   Cavity swinging measurement
556      38.67   +/- 0.03   tape & photo
776      38.640  +/- 0.007  Beam injection, poor PLL, Transmitted DC
this     38.6455 +/- 0.0012 Beam injection, independent PLL, Transmitted DC
-----------------------------

NEXT STEPS:
o RF detection at the transmitted
o Better PLL: PLL stability (in-loop / out-of-loop)
o Measurement for the 1st~3rd FSR
o Reproducibility of the measurement
o Higher order mode search
o Check the acuuracy and presicion of the Marconi

Attachment 1: yarm_dc.png

785

Sat Aug 2 18:37:41 2008

The attached PDF file is from the .xml files that I found from 7/30. Looks like someone
took some free swinging data and even made nice plots but didn't elog it. Raspberry for you.
The data files are saved in Templates/FreeSwinging/{ETMX,ETMY,etc.}/2008_07_30.xml

The top left plot on the multi-page file all have the same scale so you can see what's happened.
The peaks should all be as measured by Busby in Sep '06
but instead they are as you see here.

Attachment 1: free_080730.pdf

787

Mon Aug 4 00:37:58 2008

Abs. Len. Meas. ~ RF PD at the Y end / Manual frequency scan

Work log on August 2nd

o Just remind you:
The idea of the absolute length measurement was to detect an RF beat between the injection beam and the PSL beam by resonating both of the beams to the cavity at the same time, but on different londitudinal modes. From the frequency separation between the two beams, we get the FSR of the cavity. In order to have an injection beam with stable frequency separation, a heterodne interferometer was built at the PSL table, and the PLL servo is used to control and stabilize the frequency of the inj. beam.

----------

o An RF PD (Tholab PDA255) and a steering mirror were placed at the Yarm END. Fortunately, I found that an unused BS was already in the optical path. There was a beam block which dump the reflection of the BS and some stray lights of the OPLEV. I moved the beam block to make the BS reflection available, as well as to block the OPLEV stray light still (Photo1). In order to have the RF signal from the PD, a long BNC cable was laid along the Yarm. I did't know any better idea than this. Don't blame me.

o To have an intuitive interpretation of the beat frequency, the injection beam was set to be at higher frequency than the PSL beam. How did I confirm this? When the crystal temp (LT) of the NPRO was tuned to be higher, the beat frequency got lower.

o Frequency of the PLL was manually swept at around 15.51MHz where the 4th FSR was expected to be found. I could see strong RF peak at that frequency! When I tuned the PLL frequency, the peak height changes dramatically! Too cool!

o The amplitude of the RF peak was measured by an RF spectrum analyzer. I did all of this scan by my hands and eyes. The center frequency of the 4th FSR was 15.5149MHz. From the eye I would say the error is +/-150Hz. It is OK so far although I am not sure statistically this is correct or not. This corresponds to the length of 38.64575 +/- 0.00037 [m].

o All of the past measurements are fairly consistent.

Y-arm length
e-log              length [m]           Measurement Conditions
----------------------------------------------------------------------------------------
 556(2008-Jun-24)  38.67    +/- 0.03    Cavity swinging measurement
 776(2008-Jul-31)  38.640   +/- 0.007   Beam injection, poor PLL, Transmitted DC
 782(2008-Aug-02)  38.6455  +/- 0.0012  Beam injection, independent PLL, Transmitted DC
this(2008-Aug-04)  38.64575 +/- 0.00037 Beam injection, independent PLL, Transmitted RF
----------------------------------------------------------------------------------------

Attachment 1: YEND_LAYOUT.png

Attachment 2: 4th_FSR1.png

Attachment 3: 4th_FSR2.png

789

Mon Aug 4 05:23:57 2008

Abs. Len. Meas. ~ Measurement for Y-arm completed

Finally, I have completed the abs length and g-factor measurements for Y-arm.
>>>GO FOR THE VENT<<<

I will report the results later.

Some notes on the status:
o Y-arm was aligned at the end of the experiment by the script. The values were saved.

o At the AP table, the injection beam and the flipper were left aligned so that the inj. beam can be used as a reference of the SRM and the ITMs. But the shutter of the NPRO was closed.

o The experiment setup was mostly left at the side of the AP table. I tried not to disturb the walk as much as possible.

o The long cable from the Y-end was wound and placed at the Y-end. The knife-edge was left on the Y-end bench. It is not disturbing any beam.

793

Mon Aug 4 21:48:24 2008

Abs. Len. Meas. ~ Scan for TEM00/01/10

Work log on August 3rd - Part2

o I tried to measure the frequency of the FSRs using TEM00 resonances. Also search of TEM01/TEM10 resonances were tried.

-----------
Measurement for TEM00

o The frequency of the injection beam was scanned from 2MHz to 20MHz using the LabVIEW panel with GPIB. The 1st figure attached below is the result of the scan. Equispaced peaks were found as expected. The interval of the peaks are about 3.89MHz. Each peaks were measured with freq intervals of down to 50Hz. I will analyze the center frequency of the peaks precisely later in order to have a final result.

Measurements for TEM01/TEM10

o The beam injection technique is thought to be useful for measureing the frequency of the higher-order resonances. In order to measure the higher-order resonances the modifications of the experimental setup were applied as below.

1) For TEM10 (the beam like "OO" shape), a razor blade which blocked the horizontal half of the transmitted beam was placed. We needed to disturb half of the beam because the beat between the PSL TEM00 and the injection TEM01 cancels if the PD receives all of the light.

2) The injection beam is slightly misaligned in the horizontal direction in order to enhance the coupling of the injection beam to the cavity TEM01 mode.

3) For TEM01 (the beam like "8" shape), a razor blade cutting the vertical half and the misalignment of the inj beam in the vertical direction are applied.

o The frequency of the injection beam was scaned from 1st FSR of TEM00 in the upward direction. The alignment of the arm cavity was left untouched during the measurement. As shown in the 2nd figure attached below, the resonances were found about 1.19MHz away from the TEM00, but they are separated by about 19kHz(!). This could be split of the degenerated modes which corresponds to the difference of the mirror curvature in two directions! This difference is something like 56 m and 57 m. Can you believe this?

(To be continued to the next entry)

Attachment 1: TEM00.png

Attachment 2: TEM01.png

Attachment 3: knife_edge.png

794

Mon Aug 4 22:31:10 2008

Abs. Len. Meas. ~ Simple Test for TEM01/10 split

Work log on August 3rd - Part3

Question:
o The TEM01 and TEM10 of the Yarm were found to split with 19kHz separation. Is this true?
o In which direction the eigenmodes are?

Thought:
o The separation of 19kHz is a kind of too big because the cavity bandwidth is several kHz.
o This means that "TEM01 and TEM10 can not resonate at the same time (by the PSL beam)".

Test:
o Imagine we are just using the PSL beam and playing with an arm cavity.
o Tilt the end mirror in pitch. Resonate the TEM01 mode (8-shaped).
o Then tilt the end mirror in yaw.
o a) If the resonances are degenerated within the bandwidth of the laser, it rotates freely.
o b) If the resonances splits, the tilt in yaw does not change the shape. Then suddenly jumps to TEM10 (by an accident).

Result:
o The shape does not change. Just jumps to the other mode. (The case above b.)
o The eigenmode looked like quite horizontal and vertical.

Conclusion: the mode really splits.

Attachment 1: TEM01_10.png

795

Tue Aug 5 00:05:57 2008

Abs. Len. Meas. ~ IFR2023A calibration

Work log on August 4th

o IFR2023A (Marconi) was calibrated by the SR620 frequency counter which is locked to the GPS signal.
o The frequency of the IFR2023A was scanned from 1MHz to 20MHz with 1MHz interval. The readout of the frequency counter was recorded.
o The linear fit was taken.

f_freq_count = K0 + K1 * f_IFR [Hz]
K0 = 0.00        +/- 0.02
K1 = 0.999999470 +/- 0.000000001

o So, the IFR seems to have -0.5ppm systematic error.

797

Tue Aug 5 10:23:00 2008

steve

earthquake and venting effects

atm 1, EQ
atm 2, vent 7 days later: venting kicks optic into place to be free,
PRM: LR magnet gets pushed in and it is stocked, side in free

Attachment 1: eq4h.jpg

Attachment 2: vent4hr.jpg

799

Tue Aug 5 12:52:28 2008

ITMX, SRM OSEM spectra

Free swinging spectra of ITMX and SRM.
ITMX seems to be ok after yesterday's work, though the OSEM DC values are still a bit off from the normal value of 0.9.
(ITMX OSEM values: UL=1.12, UR=1.38, LR=0.66, LL=0.41, SIDE=0.66)
SRM is still clearly wrong.

Attachment 1: ITMX-2008_08_05-morning.pdf

Attachment 2: SRM-2008_08_05-morning.pdf

801

Wed Aug 6 11:10:34 2008

Abs. Len. Meas. ~ analysis of the TEM00 scan

Analysis of the data on August 3th ~ Part 1

From the measurement of the 5 FSRs, the FSR frequency for the Yarm cavity was estimated as
f_FSR = 3878678 Hz +/- 30 Hz
and the Yarm length is
L_yarm = 38.6462 m +/- 0.0003 m
This is the precision of 8ppm. In my opinion, this is a satisfactory result for our purpose.

Y-arm length
e-log    length [m]
-----------------------------
 556(2008-Jun-24)  38.70    +/- 0.08    Cavity swinging measurement
 556(2008-Jun-24)  38.67    +/- 0.03    Tape & photo
 776(2008-Jul-31)  38.640   +/- 0.007   Beam injection, poor PLL, Transmitted DC
 782(2008-Aug-02)  38.6455  +/- 0.0012  Beam injection, independent PLL, Transmitted DC
 787(2008-Aug-04)  38.64575 +/- 0.00037 Beam injection, independent PLL, Transmitted RF
this(2008-Aug-04)  38.6462  +/- 0.0003  Beam injection, independent PLL, Transmitted RF, five FSRs, freq calibrated
-----------------------------

----------------
o According to the entry 795, all of the scan frequency was calibrated.
o The five peaks of the scanned data for TEM00 were fitted. Each peak was fitted by the following formula:

V(f) = A / Sqrt(1 - ((f-f0)/fc)^2)

Variable
f: scan frequency

Parameters
A: peak amplitude
f0: center frequency
fc: half bandwidth of the peak for -3dB

o The results are shown in the attached figure 1. They look very similar each other but they are different plot! The fittings were extremely good. The center frequencies estimated were as follows:

FSR1:  3879251.9 Hz +/-  8.8 Hz
FSR2:  7757968.1 Hz +/- 10.8 Hz
FSR3: 11636612.9 Hz +/- 10.2 Hz
FSR4: 15515308.1 Hz +/-  8.7 Hz
FSR5: 19393968.7 Hz +/-  8.4 Hz

o The FSR frequencies were fitted by a line. The fitting and the residuals are shown in the attached figure 2.
The fitting results were

f_FSR(n) = 586.4 + 3878678 * n

This means that:
o FSR frequency was 3878678 [Hz].
o The lock of the carrier had detuning of 586 [Hz].

The detuning of the carrier from the resonance can be explained by the alignment drift. In deed, at the end of the measurement, decrease of the transmitted power by -15% was found. Then, the frequency of the 1st FSR was measured before and after the alignment adjustment. This changed the frequency of the FSR1 by 350Hz. This change could not be explained by the cavity length change as this is too big (~3.5mm).

Actually, the spacing of the cavity length is more stable. The residual is rather scattered with in 20-30Hz. So, I took the error of 30Hz as the whole precision of the frequency measurement that includes the fluctuation of the alignment, the cavity length itself, and so on. This yields the FSR and the cavity length of
f_FSR = 3878678 Hz +/- 30 Hz
L_yarm = 38.6462 m +/- 0.0003 m .

Attachment 1: TEM00fit.png

Attachment 2: TEM00FSRfit.png

802

Wed Aug 6 11:43:52 2008

Abs. Len. Meas. ~ analysis of the TEM01 scan

Analysis of the data on August 3th ~ Part 2

o I already have reported that the resonant freq of TEM10 and TEM01 split.

o Again, note that TEM10/01 were arranged almost in the horizontal/vertical by the observation of the video.

o The peaks of TEM10 and TEM01 were fitted with the same method as of TEM00.

o The peak freqs were:
f_TEM10: 5087040 Hz +/- 20 Hz
f_TEM01: 5068322 Hz +/- 15 Hz
The split is 18.7kHz.

o The additional parameter from the previous entry:
f_TEM00: 3879252 Hz +/- 9 Hz
L_yarm: 38.6462 m +/- 0.0003 m

o Radius of curvature
Rx = L /(1-Cos^2(Pi (f_TEM10 - f_TEM00) / (c/L/2) ))
Ry = L /(1-Cos^2(Pi (f_TEM01 - f_TEM00) / (c/L/2) ))

from these formula we get the value
Rx = 56.1620 +/- 0.0013 [m]
Ry = 57.3395 +/- 0.0011 [m]

Attachment 1: TEM01fit.png

803

Wed Aug 6 13:15:57 2008

SRM ETMX freeswing spectra

After yesterday's work on the SRM, I took free swinging spectra of SRM.
The eigen modes look ok. But there are many other peaks which were not present in vacuum.
Some of those peaks may be resonances of the air inside the chambers and the pipes.
However, the peaks around 0.2Hz are too low frequency for those air compression modes.
I took the ETMX spectra at roughly the same time. I chose ETMX because we have not touched it after the vent.
ETMX also shows some extra peaks but the frequencies are different.

Attachment 1: SRM-ETMX-freeswing.pdf

805

Wed Aug 6 19:01:15 2008

Alberto

ITMX and SRM OSEM post-earthquake diagnostic

Koji, Yoichi, Alberto

Today we reset the OSEMs on ITMX and SRM in order to be centered when the mirrors are aligned to the IFO beam. Since the PRM is still out of order, we used the beam from NPRO laser of the absolute length measurement experiment as it is injected through the AS port.
That�s how we did it:

1) We aligned the SRM so that the reflected beam from the NPRO was at the camera after at the AS port.

2) We traded off the alignment of SRM in order for the reflected beam at the camera to have a nice shape, avoiding any clipping from the optics, and for the optical lever to be not too far from zero. The final alignment for SRM, as read on the sliders on the MDM screen, is: Pitch=1.1650, Yaw=1.4674.

3) We aligned ITMX checking out by an IR card that the incoming and the reflected main beam in between ITMX and the BS matched. The alignment of the two beams was improved checking the matching after the SRM. The final alignment for ITMX, as read on the sliders on the MDM screen, is: Pitch=-1.2937, Yaw=-0.9890.

4) After the alignment of SRM and ITMX these were the voltages at the OSEMs:

SRM
UL=0.957
UR=1.254
LR=0.768
LL=0.620
Side=0.958

ITMX
UL=1.144
UR=1.360
LR=0.591
LL=0.325
Side=-----

5) Finally we centered the OSEMs on both mirrors and we read these voltages:

SRM
UL=0.939
UR=0.994
LR=0.782
LL=0.938
Side=0.953

ITMX
UL=0.918
UR=0.891
LR=0.887
LL=0.875
Side=0.883

806

Wed Aug 6 22:19:07 2008

Koji, Yoichi

We realized that we did not pay attention to the BS alignment while working on the alignment of the ITMX today. Because we were injecting the ALM laser (absolute length measurement laser) from the AS port, the ITMX alignment depends on the BS alignment.
The BS optical lever was not centered and the sum was about 2000cnt, which is low compared, for example, to the SRM oplev.
So we were not sure if the BS was in a good alignment or not.
So we decided to move the BS to center the QPD.
In doing so, we also moved the ITMX so that we do not lose the ALM laser beam coming back to the AS port.
When the BS oplev was centered, the sum of the QPD was still about 2000. So it was not far off centered.
After the tweaking, we were able to see some interference between the light reflected by the ITMY and ITMX at the AS port (actually this is the bright port for the ALM laser). By tweaking the ITMY, we were able to see Michelson fringes at the AS port.
If we believe the ALM laser alignment is still good after the vent, the ITMX, ITMY, BS and SRM should be now in a good alignment condition.
The OSEM values for the ITMX, BS, SRM seem to be ok (0.9+/-0.2). The ITMY LL is a bit low (~ 0.45).

807

Thu Aug 7 10:07:13 2008

Free swinging OSEM spectra

Looks like there are more extra peaks in the SRM than other optics.
Maybe because it is closer to the door ?

Attachment 1: FreeSwingSpectra.pdf

808

Thu Aug 7 10:27:59 2008

Free swinging OSEM spectra

Sometimes we see extra peaks in the OSEM spectra coming from a beat between the regular eigenmodes.
This probably comes from the OSEM shadow sensor not being entirely linear - the nonlinearity is
greatly increased if the magnet is not perfectly centered in the LED beam. So the beats are
probably there at some level in all of them; usually below the noise.

810

Thu Aug 7 12:20:52 2008

PRM stand-offs and wire

We removed the side OSEM of the PRM so that we can see the stand-off on the farther side.

Attachment 1: Farther side stand-off from an angle before removing the OSEM
Attachment 2: Farther side stand-off through the empty OSEM hole.
Attachment 3: Near side stand-off

The wire is definitely in the near side stand-off groove.
Probably the wire is in the groove also on the farther side.

Attachment 1: IMG_1456.JPG

Attachment 2: IMG_1478.JPG

Attachment 3: IMG_1470.JPG

811

Thu Aug 7 17:32:23 2008

Jenne

Afternoon PRM activities

Rana, Jenne, Yoichi, Dmass

After Yoichi confirmed this morning that the wire was in both grooves, Rana attempted to lift the PRM a tiny bit, and twist it around (very gently of course) to see if we could make the wire slip back to its nominal position underneath the optic. On the first attempt, the wire ended up slipping the wrong way, causing slightly more tilt. On another attempt, the wire came out of the groove nearest the chamber door by about 0.5mm. We got the wire back in the groove by slightly lifting the optic, and pushing the wire back in. Then, on further attempts at making the wire slip back to its nominal position, the wire came out of the groove farthest from the chamber door. It is very difficult to get at that side of the PRM, because the table is crowded, and it is on the far side of the optical table from the chamber door. We decided to pull the PRM out of the chamber. Rana clamped the mirror into its cage using the earthquake stops and removed the OSEMS, and then we pulled the mirror out. We put it on a cart that was covered with foil and had a little foil house for the optic cage. We rolled the mirror+cage over to the flow bench at the end of the y-arm.

We saw that the wire is no longer even on the standoff (~3mm away from the groove) on the side that was farthest from the chamber door.

Since we have not confirmed that we have spare wire and spare magnets (and due to the time of day), we have decided to cover the cage with some foil, while it is sitting on the flow bench, and we'll fix the wire in the morning.

812

Fri Aug 8 09:54:10 2008

New code + gstreamer allows for easy saving and compression of images

Cameras

Quote:

Modified the CamSnap code to output the image data stream to standard out. This can then be piped into a gstreamer plugin and then be used

Didn't work; Prosilica has only 1 "l". Even so, sshing from op440m to mafalda, I got this:

mafalda:SnapCode>CamSnap -F 'Mono8' -c 44058 -E 5000 -X 0 -Y 0 -H 480 -W 752 -l 0 -m 300 | gst-launch-0.10 fdsrc fd=0 blocksize=360960 ! video/x-raw
-gray, height=480, width=752, bpp=8,depth=8,framerate=30/1 ! ffmpegcolorspace ! theoraenc ! oggmux ! filesink location="./testVideo.ogm"
Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...

** (gst-launch-0.10:27121): WARNING **: Size 60 is not a multiple of unit size 360960
Caught SIGSEGV accessing address 0x487c
ERROR: from element /pipeline0/ffmpegcsp0: subclass did not specify output size
Additional debug info:
gstbasetransform.c(1495): gst_base_transform_handle_buffer (): /pipeline0/ffmpegcsp0:
subclass did not specify output size
ERROR: pipeline doesn't want to preroll.
Setting pipeline to NULL ...
#0  0xffffe410 in __kernel_vsyscall ()
#1  0xb7deddae in __lll_mutex_lock_wait ()
#2  0xb7de9aac in _L_mutex_lock_51 () from /lib/tls/i686/cmov/libpthread.so.0
#3  0xb7de949d in pthread_mutex_lock ()
#4  0xb7e452e0 in g_static_rec_mutex_lock () from /usr/lib/libglib-2.0.so.0
#5  0xb7f1fa08 in ?? () from /usr/lib/libgstreamer-0.10.so.0
#6  0x080c1220 in ?? ()
#7  0x00000001 in ?? ()
#8  0x0809586c in ?? ()
#9  0x00000001 in ?? ()
#10 0x08095868 in ?? ()
#11 0xb7f7a2a8 in ?? () from /usr/lib/libgstreamer-0.10.so.0
#12 0xb7e8da80 in ?? () from /usr/lib/libglib-2.0.so.0
#13 0xb7f7a2a8 in ?? () from /usr/lib/libgstreamer-0.10.so.0
#14 0xb7f7a2a8 in ?? () from /usr/lib/libgstreamer-0.10.so.0
#15 0x00000000 in ?? ()
Spinning.  Please run 'gdb gst-launch 27121' to continue debugging, Ctrl-C to quit, or Ctrl-\ to dump core.
Caught interrupt --

814

Fri Aug 8 11:04:34 2008

MCL Wiener filter

I took some old data from Rana and converted the units of the Weiner filter to m/m so to make the effect of the seismometer and accelerometers more obvious.

The data is in counts, and so to convert to m this is what I did:

%%% MC_L calibration
v_per_counts = 5/32768;
v_per_v = 3;
amp_per_N = 1/0.064;

%%% Accelerometers calibration
v_per_counts_acc = 61.045e-6;
g_per_v = 9.8/100;

%%% Seismometer calibration
v_per_counts_seis = 61.045e-6;
m_per_s_per_s_per_volt = 9.8/100;
m_per_v_per_s = 1/345;

for jj=1:6
hfmatm(:,jj)=hfmat(:,jj).*(v_per_counts.*v_per_v.*amp_per_N.*f)./(v_per_counts_acc*g_per_v); %%% accelerometers' data
end
hfmatm(:,7)=hfmat(:,7).*(v_per_counts.*v_per_v.*amp_per_N)./(v_per_counts_seis*m_per_v_per_s); %%% Seismometer data

Attachment 1: m_per_m.png

816

Fri Aug 8 13:29:54 2008

No groove in the stand-off ... wait, it is not even a stand-off !

Yoichi, Steve, Seiji

We took magnified pictures of the stand-offs of the PRM.
Attm1: North side stand-off.
Attm2: South side stand-off.
Attm3: Zipped file of the full pictures.

We found no groove in the south side stand-off.
After some discussion, we concluded that it is actually a guide rod. You can see it from the size difference (the magnification is the same for the two pictures).
The stand off on the south side is missing (fell off, ran away, evaporated or whatever ...).
Also we noticed that the guide rod on the north side is missing.

We have to find a stand-off and place it on the south side.
Seiji suggested that it is better to put a guide rod next to the north side stand-off, otherwise the stand-off itself is too weak to hold the load.
He also said that the PRM was installed after he left, so it was not his fault.

Attachment 1: north-standoff-preview.jpg

Attachment 2: south-standoff-preview.jpg

Attachment 3: No-groove.zip

817

Fri Aug 8 15:10:35 2008

No groove in the stand-off ... wait, it is not even a stand-off !

I tried to find the missing stand-off and the guide rod in the BS chamber, but I couldn't.

818

Fri Aug 8 17:54:52 2008

Jenne

Standoffs and Guide Rods

After closer inspection of other small optics, it is clear that the guide rods should be above the standoffs on our small optics. Yoichi took a picture of the SRM that shows this clearly. This makes sense since the tension of the wire will make the standoff 'want' to go up during pre-epoxy adjustment, so the guide rod prevents the standoff from popping up and out.

Looking at the side of the PRM without the groove, it looks like there is lots of space between the guide rod and the alignment etch in the glass, so we can just place a standoff directly under the guide rod that is present.

A spare standoff is being shipped tomorrow morning, so we should have it by Monday for installation on the PRM.

Attachment 1: SRM_Standoff_and_guide.JPG

820

Mon Aug 11 00:58:31 2008

2 years of temperature trend

PEM

The PSL RMTEMP alarmed again because it says the room temperature is 19.5 C. Steve said in
an earlier log entry that this is a false alarm but he didn't say why he thought so...

I say that either the calibration of the RMTEMP channel has drifted, the setpoint of the HVAC
has shifted, or there's a drift in the RMTEMP channel. I don't know what electronics exactly
are used for this channel so not sure if its susceptible to so much drift.

However, since the Dust Monitor (count_temp) shows a similar temperature decline in the
last two years I am inclined to blame the HVAC system.

The attached plot shows 2 years of hour-mean trend.

Attachment 1: Untitled.png

821

Mon Aug 11 09:39:29 2008

2 years of temperature trend

PEM

Steve and I went around and inspected and then adjusted the thermostats and humidostats.

All the thermostats were set at 70F in 2005 by Steve. We adjusted the ones on the arms up to 72F
and set the one on the wall west of the framebuilder up to 74F (this area was consistently colder
than all the others and so we're over-correcting intentionally).

827

Tue Aug 12 12:05:36 2008

Computers

HP color printer is back

I restarted the HP printer server (a little box connected to the HP color laser) so that we can use the HP LaserJet 2550.
After this treatment, the printer spat out a bunch of pages from suspended jobs, many of these were black and white.
I think people should use the black-and-white printer for these kind of jobs, because the color printer is slow and troublesome.

829

Tue Aug 12 19:48:24 2008

Jenne

PRM standoff is in....mostly

IOO

Yoichi, Jenne

The missing PRM standoff is now partially installed. The standoff is in, and the wire is in the groove, but we have not finished adjusting its position to make the PRM stand up straight. It turns out to be pretty tricky to get the position of the standoff just right.

We have set up a HeNe laser as an oplev on the flow bench (which we checked was level) in the clean assembly room, and are using it to check the pitch of the mirror. We set a QPD at the height of the laser, and are looking at the single-reflected light. When the single-reflected light is at the same height as the center of the QPD, then the mirror is correctly aligned in pitch. (Actually, right now we're just trying to get the single-reflected light to hit the diode at all...one step at a time here).

We'll continue trying to align the PRM's standoff in the morning.

830

Tue Aug 12 21:38:19 2008

John

Accidental higher order mode resonances in the arms

LSC

Recently we had been having some trouble locking the full IFO in the spring configuration (SRC on +166).
It was thought that an accidental higher order mode resonance in the arms may have been causing problems.

I previously calculated the locations of the resonances using rough arm cavity parameters(Elog #690). Thanks to Koji
and Alberto I have been able to update this work with measured arm length and g factors for the y arm (Elog #801,#802).
I have also included the splitting of the modes caused by the astigmatic ETM. Code is attached.

I don't see any evidence of +166MHz resonances in the y arm.

In the attached plot different colours denote different frequencies +33, -33, +166, -166 & CR.
The numbers above each line are the mn of TEMmn.
Solid black line is the carrier resonance.

Attachment 1: HOMresonances.png

Attachment 2: HOMarms2.m

%Check for accidental resonances of HOM in the arms (maybe due to
%sidebands). At the moment there is only data for the y arm.

clear all
close all
clc


%Stuff one might change often
modeorder = 0:5;          % Look for TEMmn modes where m,n run over modeorder

... 157 more lines ...

832

Wed Aug 13 20:13:35 2008

PRM stand-off is glued

Steve, Janne, Rob, Bob, Koji, Yoichi

We finally managed to balance the PRM and the stand-off is now glued.

The whole procedure was something like this:

(1) Measure the levelness of the optical table. It was done by a bubble level claiming that
the sensitivity is 60 arcsec (roughly 0.3 mrad).
There was no noticeable tilt along the longitudinal direction of the table.

(2) We put a He-Ne laser on one end of the table. Mounted a QPD on a X-Y-Z stage. Put the QPD very
close to the laser and centered it by moving the QPD.
Then we moved the QPD far away from the laser and centered the beam spot in vertical direction
by changing the tilt of the laser mount.
We then moved the QPD close to the laser again and adjusted the height to center it. By repeating
the centering at two locations (near and far) several times, we aligned the laser beam parallel to
the table.

(3) The PRM suspension tower was put on the other end of the optical table, i.e. far from the laser.
The QPD was moved next to the laser to form an optical lever. The height of the QPD is preserved from
the previous step.

(4) A stand-off was picked by a pair of tweezers. By gently lifting the mirror by the bottom earthquake stops,
the tension of the wire was relieved. Then the stand off was slid in below the guide rod.

(5) Using the microscope, it was confirmed that the wire is in the grooves on both sides.

(6) Without damping, it was too much pain to balance the mirror. So we put spare OSEMs in the suspension and
pulled a long cable from the suspension rack to the clean room with a satellite amp.

(7) It turned out that the pinout of the cable is flipped because of the vacuum feed through. So we asked Ben for help.
He made conversion cables. We also found UR OSEM was not responding. Ben opened the satellite box, and we found an op-amp was burnt.
Probably it was because we connected OSEMs wrongly at first and the LED current driver was shorted. We switched the satellite box
from the PRM one to the BS one. Ben will fix the PRM box.
Bob cleaned up some D-Sub converters for the interface with the clean OSEM pigtails.

(8) While waiting for Ben, we also tried to short the OSEM coils for inductive damping. We saw no noticeable change in the Q.

(9) After the OSEMs were connected to the digital control system, Rob tweaked the damping gains a bit to make it work efficiently.

(10) I pushed the stand-off back and forth to make the reflected beam spot centered on the QPD. I used the PZT buzzer to gently move the stand-off.
For fine tune, just touching it is enough. I found it useful to touch it without clamping the mirror, because if it is clamped, we can easily push
it too hard. When the mirror is freely hanging, once the tip of the buzzer touches the stand-off, the mirror escapes immediately. If the mirror
swings wildly by your touch, you pushed it too hard.

(11) After about an hour of struggle, I was able to level the mirror. We used about 1.5m optical lever arm. A rough calibration tells us that the
beam spot is within 0.6mm of the center of the QPD. So the reflected light is deflected by 0.4mrad. That means the mirror
is rotated by 0.2mrad. The OSEMs should have about 30mrad of actuation range. So this should be fine.

(12) We mixed the Vac Seal epoxy and put it under vacuum for 15min to remove bubbles. Actually 15min was not enough for removing bubbles completely. But
stopped there because we did not want the epoxy to be too stiff.
I dipped a thin copper wire into the epoxy and applied it on the top of the stand-off. I found the epoxy is already not fluid enough, so Steve made
another Vac Seal mixture. This time we put it under vacuum for only 3 min.
I also applied the epoxy to the sides of the stand-off.
While working on this, I accidentally touched the side of the PRM. Now there is a drop of epoxy sitting there (upper left of the attached picture).
We decided not to wipe it out because we did not want to screw up the levelness.

(13) We put an incandescent light about 1m away from the suspension to gently warm up the epoxy but not too much. We will leave it overnight to cure the
epoxy.

Attachment 1: img1.jpg

834

Thu Aug 14 11:39:06 2008

steve

particle counter is out of order

PEM

The 40m ifo paricle counter sensor failed last night.

841

Fri Aug 15 16:45:43 2008

Converting from FIR to IIR

I have been looking into different techniques to convert from FIR to IIR. This is so we can see how effective the adaptive FIR filter is in comparison to an IIR one with fewer taps.
For now I tried 2 matlab functions: Prony and stmcb (which works on LMS method).
I used the FIR wiener code, MC1_X, (c1wino) and applied the FIR to IIR algorithm.
Seems like the stmcb one works a bit better, and that there isn't much effect for having 1000 and not 400 taps.

Will keep updating on more results I have, and hopefully have the MC in time to actually check this live.

Attachment 1: fir2iir50.png

Attachment 2: fir2iir400.png

Attachment 3: fir2iir1000.png

842

Fri Aug 15 17:38:41 2008

OSEM free swinging spectra before the pump down

I ran an overnight measurement of the free swinging OSEM spectra.
The attm1 shows the results. Everything look ok except for the ITMY UL OSEM.
The time series from that OSEM was very noisy and had many spikes.
We suspected the cable from the satellite box to the computer rack because we disconnected the cable
when we tested a spare cable which was used to connect the spare OSEMs to the PRM suspension in the clean room.
Janne remembered when she put the cable back, she trusted the latch on the connector and did not push it in too hard.
However, Rob suggested the latch does not work well. So she pushed the connector again. Then the signal from
the ITMY UL OSEM got back to normal.
The second attachment shows the ITMY spectra after the cable push.
We decided to pump down after confirming this.

There are still a lot of extra peaks especially in the suspensions in the BS chamber.
These may be inter modulations (by the non-linearities of the OSEMs) of the modes of the multiple
suspensions sitting on the same stack.

Attachment 1: 2008-8-15.pdf

Attachment 2: ITMY2.pdf

846

Mon Aug 18 11:50:29 2008