40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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ID Date Author Type Category Subject
  82   Thu Nov 8 00:55:44 2007 pkpUpdateOMCSuspension tests
[Sam , Pinkesh]

We tried to measure the transfer functions of the 6 degrees of freedom in the OMS SUS. To our chagrin, we found that it was very hard to get the OSEMs to center and get a mean value of around 6000 counts. Somehow the left and top OSEMs were coupled and we tried to see if any of the OSEMs/suspension parts were touching each other. But there is still a significant coupling between the various OSEMs. In theory, the only OSEMS that are supposed to couple are [SIDE] , [LEFT, RIGHT] , [TOP1, TOP2 , TOP3] , since the motion along these 3 sets is orthogonal to the other sets. Thus an excitation along any one OSEM in a set should only couple with another OSEM in the same same set and not with the others. The graphs below were obtained by driving all the OSEMS one by one at 7 Hz and at 500 counts ( I still have to figure out how much that is in units of length). These graphs show that there is some sort of contact somewhere. I cant locate any physical contact at this point, although TOP2 is suspicious and we moved it a bit, but it seems to be hanging free now. This can also be caused by the stiff wire with the peek on it. This wire is very stiff and it can transmit motion from one degree of freedom to another quite easily. I also have a graph showing the transfer function of the longitudnal degree of freedom. I decided to do this first because it was simple and I had to only deal with SIDE, which seems to be decoupled from the other DOFs. This graph is similar to one Norna has for the longitudnal DOF transfer function, with the addition of a peak around 1.8 Hz. This I reckon could very be due to the wire, although it is hard to claim for certain. I am going to stop the measurement at this time and start a fresh high resolution spectrum and leave it running over night.

There is an extra peak in the high res spectrum that is disturbing.
Attachment 1: shakeleft.pdf
Attachment 2: shakeright.pdf
Attachment 3: shakeside.pdf
Attachment 4: shaketop1.pdf
Attachment 5: shaketop2.pdf
Attachment 6: shaketop3.pdf
Attachment 7: LongTransfer.pdf
LongTransfer.pdf LongTransfer.pdf LongTransfer.pdf
Attachment 8: Shakeleft7Nov2007_2.pdf
Attachment 9: Shakeleft7Nov2007_2.png
  81   Wed Nov 7 16:07:03 2007 steveUpdatePSLPSL & IOO trend
1.5 days of happy psl-ioo with litle bumps in C1:PSL-126MOPA_HTEMP
Attachment 1: psl1.5dtrend.jpg
  80   Wed Nov 7 14:05:59 2007 tobinConfigurationIOOMC ringdown
Modeling the mode cleaner as a simple cavity with all losses lumped together, we expect the cavity power to be
attenuated by a factor (1-L) after each interval (2l/c)=1/fsr. Therefore we can get the cavity loss L
(including power lost through transmission) from the ringdown time constant tau as:

L = 1 - exp[ - 1/(tau * fsr) ]

From this we have to subtract the 2000 ppm transmission for each of MC1 and MC3, and divide by three to spread
the losses across the three optics.

I get 168 39 ppm loss per optic based on a very simple exponential fit to the tails (t>0) of four of Andrey's data files.

By comparison, I get 154 37 ppm from Rana's data files from before the vent.
  79   Wed Nov 7 14:01:31 2007 waldmanOmnistructureOMCFrequency and Intensity noise
One of the biggest problems I had using the PZT to lock was excessive noise. I did a little noise hunting and found that the problem was the cable running from the rack to the laser fast input. As a reminder, the laser has a 4 MHz / volt fast input. We require about 300 MHz to go one FSR, so there is a Thorlabs HV box between at the NPRO fast input which takes 0-10 V -> 0-150 V. The 150 V HV range is worth about 600 MHz of NPRO frequency.

OLD SETUP: Single side of DAC differential (10 Vpp) -> 9V in series with 10 kOhm -> 10 kOhm input impedance of Thorlabs HV -> NPRO

We used the single side of the DAC differential because we didn't have a differential receiver. This turned out to be a bad idea because the cable picks up every 60 Hz harmonic known to man kind.

NEW SETUP: Digital conditioning -> DAC differential (digitally limited to 0 - 1 V) -> SR560 in A-B mode gain 10 (0 - 10 V output)-> Thorlabs HV -> NPRO.

This has almost no 60 Hz noise and works much, much better. Moral of the story, ALWAYS USE DIFFERENTIAL SIGNALS DIFFERENTIALLY !

Note that I may be saturating the SR560 with 10 V output, Its spec'd for 10 Vpp output with 1 VDC max input. I don't know whether or not it can push 10 V out....
  78   Wed Nov 7 13:54:44 2007 robConfigurationIOOMode Cleaner transfer function
I performed the same procedure described here, and re-measured the transfer function of the mode cleaner to see the effect of the drag-wiping. The results are attached in a pdf. We don't seem to have done any damage, but the improvements are barely measurable.

pole frequency3.789kHz3.765kHz
loss per optic99ppm91ppm
Attachment 1: mctf.pdf
  77   Wed Nov 7 10:55:21 2007 ajwConfigurationComputersbackup script restarted
Following the reboot of computers on 10/31/07, the backup script required restart (which unfortunately "can't" be automated because a password needs to be typed in). I restarted, following the instructions in /cvs/cds/caltech/scripts/backup/000README.txt and verified that it more-or-less worked last night (the rsync sometimes times out; it gets through after a couple of days of trying.)
  76   Wed Nov 7 09:38:01 2007 steveUpdateVACrga scan
pd65-m-d2 at cc1 6e-6 torr
Attachment 1: pd65d2.jpg
  75   Wed Nov 7 02:14:08 2007 AndreyBureaucracyIOOMore information about MC2 ringdown
As Tobin wrote two hours ago, we (Andrey, Tobin, Robert) made a series of ringdown measurements for MC2
in the spirit of the measurement described by Rana -> see
entry from Mon Oct 29 23:47:29 2007, rana, Other, IOO, MC Ringdowns.

I attach here some pictures that we saw on the screen of the scope, but I need to admit that I am not experienced enough to present a nice fit to these data, although I attach fits that I am able to do today.

I definitely learned a lot of new Matlab functions from Tobin - thanks to him!, but I need to learn two more things:

Firstly, I do not know how to delete "flat" region (regions before the ringdown starts) in Matlab ->
I needed to delete the entries for times before the ringdown ("negative times") by hand in the text-file, which is extremely non-elegant method;

Secondly, I tried to approximate the ringdown curve by a function ydata=a*exp(b*xdata) but I am not exactly sure if this equation of the fitting curve is a good fit or if a better equation can be used.

It seems, in this situation it is better for me to ask more experienced "comrades" on November 7th.

P.S. It seems I really like the type of message "Bureaucracy" - I put it for every message. As Alain noted, maybe that is because some things are very bureacratized in the former USSR / Russia. By the way, when I was young, November 7th was one of two most important holidays in the USSR - I liked that holiday because I really liked military parades on the red square. I attach a couple of pictures. November 7 is the anniversary of the Revolution of 1917.
Attachment 1: image-attempt_1.png
Attachment 2: image-attempt_2.png
Attachment 3: image-attempt_3.png
Attachment 4: image-attempt_4.png
Attachment 5: image-attempt_5.png
Attachment 6: Fit-1st_attempt.jpg
Attachment 7: Fit-5th_attempt.jpg
Attachment 8: 7_Nov_1941-parad-na-krasnoy-ploschadi.jpg
Attachment 9: parad1984-moskva.jpg
  74   Wed Nov 7 00:51:33 2007 andrey, rob, tobinConfigurationIOOMC ringdowns
We completed several ringdown measurements this afternoon; Andrey is currently processing the data.
  73   Tue Nov 6 23:45:38 2007 tobinConfigurationComputerstektronix scripts!
I cooked up a little script to fetch the data from the networked Tektronix scope. Example usage:

linux2:scripts>tektronix/tek-dump scope0 ch1 foo.csv

"scope0" is the hostname of the scope, "ch1" is the channel you want to dump, and "foo.csv" is the file you want to dump it to. The script is written in Python since Python's libhttp gave me less trouble than Perl's HTTP::Lite.
  72   Tue Nov 6 18:18:15 2007 tobinConfigurationComputersI broke (and fixed) conlogger
It turns out that not only restart_conlogger, but also conlogger itself checks to see that it is running on the right machine. I had changed the restart_conlogger script to run on op340, but it would actually silently fail (because we cleverly redirect conlogger's output to /dev/null). Anyway, it's fixed now: I edited the conlogger source code where the hostname is hardcoded (blech!) and recompiled.

On another note, Andrey fixed the "su" command on op440m. It turns out that the GNU version, in /usr/local/bin, doesn't work, and was masking the (working) sun version in /bin. Andrey renamed the offending version as "su.backup".
  71   Tue Nov 6 16:48:54 2007 tobinConfigurationComputersscopes on the net
I configured our two 100 MHz Tektronix 3014B scopes with IP addresses: (scope0) and (scope1). Let the scripting commence!

There appears to be a Matlab Instrument Control Toolbox driver for this scope.
  70   Tue Nov 6 15:37:34 2007 robConfigurationSUSrampdown script
/cvs/cds/caltech/scripts/SUS/rampdown.pl is now in the crontab for op340m, running every half-hour at 15&45. It checks the suspension watchdog trip levels, and reduces them by 20 if they are above 150.
  69   Tue Nov 6 15:36:03 2007 robUpdateLSCXARM locked
Easily, after resetting the PSL Uniblitz shutters. There's no entry from David or Andrey about the recovery from last week's power outage, in which they could have indicated where the procedure was lacking/obscure. Tsk, tsk.
  68   Tue Nov 6 14:51:03 2007 tobin, robUpdateIOOMode cleaner length
Using the Ward-Fricke variant* of the Sigg-Frolov method, we found the length of the mode cleaner to be 27.0934020183 meters, a difference of -2.7mm from Andrey, Keita, and Rana's measurement on August 30th.

The updated RF frequencies are:
3  fsr =  33 195 439 Hz
12 fsr = 132 781 756 Hz
15 fsr = 165 977 195 Hz
18 fsr = 199 172 634 Hz
* We did the usual scheme of connecting a 20mVpp, 2 kHz sinusoid into MC AO. Instead of scanning the RF frequency by turning the dial on the 166 MHz signal generator ("marconi"), we connected a DAC channel into its external modulation port (set to 5000 Hz/volt FM deviation). We then scanned the RF frequency from the control room, minimizing the height of the 2 kHz line in LSC-PD11. In principle one could write a little dither servo to lock onto the 15fsr, but in practice simply cursoring the slider bar around while watching a dtt display worked just fine.
  67   Tue Nov 6 10:42:01 2007 robConfigurationIOOmode cleaner locked
Increased the power exiting the PSL by turning the half-wave plate after the MOPA, opened the PSL shutter, and aligned the mode cleaner to the input beam. It wasn't that hard to find the beam with the aperture open all the way on the MC2 camera. The transmitted power is now 2.9 arbitrary units, while the input power is 1.2 arbitrary units. Not sure yet if that's an increase or decrease in efficiency, since no one posted numbers before the vent. Also turned on the input-steering PZTs and saw a REFL beam on the camera.
  66   Tue Nov 6 09:45:22 2007 steveSummarySUSvent sus trend
The mc optics dragwippings were done by locking optics by eq stops and rotating-moving
cages so access were good. This technic worked well with mc1 & mc2
MC3 osems were reoriented only.
Attachment 1: ventsustrend.jpg
  65   Tue Nov 6 09:14:37 2007 steveSummaryVACpump down 65
8 hr plot,
precondition: 5 days at atm,
vent objective: drag wiping mc1, mc2 & mc3 accomplished,
hardware changes: IOO access connector, mc2 chamber door south & west
were removed and reinstalled
pump down mode: slow to avoid steering up dust
One roughing pump was used with closed down valve position in the first 4 hrs

Andrey was very helpful
Attachment 1: pd65.jpg
  64   Mon Nov 5 22:24:38 2007 Andrey, SteveOmnistructureVACPumping down goes smoothly

We (Steve and Andrey) started pumping down at 3.25PM today. At 9 PM we turned off the rotary pump, and turned on turbomolecular pumps.

By 10.10PM we reached the pressure 1 milliTorr, and the current status is "Vacuum Normal". We leave the turbopumps on for the night, and as it is pretty late for Steve, we are going home.

P.S. Steve was very displeased with the standard selection of "Type" of messages, he would like to extend that list.
  63   Mon Nov 5 14:44:39 2007 waldmanUpdateOMCPZT response functions and De-whitening
The PZT has two control paths: a DC coupled path with gain of 20, range of 0 to 300 V, and a pair of 1:10 whitening filters, and an AC path capacitively coupled to the PZT via a 0.1 uF cap through a 2nd order, 2 kHz high pass filter. There are two monitors for the PZT, a DC monitor which sniffs the DC directly with a gain of 0.02 and one which sniffs the dither input with a gain of 10.

There are two plots included below. The first measures the transfer function of the AC monitor / AC drive. It shows the expected 2 kHz 2d order filter and an AC gain of 100 dB, which seems a bit high but may be because of a filter I am forgetting. The high frequency rolloff is the AA and AI filters kicking in which are 3rd order butters at 10 kHz.

The second plot is the DC path. The two traces show the transfer function of DC monitor / DC drive with and with an Anti-dewhitening filter engaged in the DC drive. I fit the antidewhite using a least squares routine in matlab constrained to match 2 poles, 2 zeros, and a delay to the measured complex filter response. The resulting filter is (1.21, 0.72) : (12.61, 8.67) and the delay was f_pi = 912 Hz. The delay is a bit lower than expected for the f_pi = 3 kHz delay of the AA, AI, decimate combination, but not totally unreasonable. Without the delay, the filter is (1.3, 0.7) : (8.2, 13.2) - basically the same - so I use the results of the fit with delay. As you can see, the response of the combined digital AntiDW, analog DW path is flat to +/- 0.3 dB and +/- 3 degrees of phase.

Note the -44 dB of DC mon / DC drive is because the DC mon is calibrated in PZT Volts so the TF is PZT Volts / DAC cts. To calculate this value: there are (20 DAC V / 65536 DAC cts)* ( 20 PZT V / 1 DAC V) = -44.2 dB. Perfect!

I measured the high frequency response of the loop DC monitor / DC drive to be flat.
Attachment 1: 07110_DithertoVmonAC_sweep2-0.png
Attachment 2: 071105_LSCtoVmonDC_sweep4-0.png
Attachment 3: 07110_DithertoVmonAC_sweep2.pdf
07110_DithertoVmonAC_sweep2.pdf 07110_DithertoVmonAC_sweep2.pdf
Attachment 4: 071105_LSCtoVmonDC_sweep4.pdf
071105_LSCtoVmonDC_sweep4.pdf 071105_LSCtoVmonDC_sweep4.pdf
  62   Mon Nov 5 07:29:35 2007 ranaUpdateIOOFriday's In-Vac work
Liyuan recently did some of his pencil beam scatterometer measurements measuring not the
BRDF but instead the total integrated power radiated from each surface point
of some of the spare small optics (e.g. MMT, MC1, etc.).

The results are here on the iLIGO Wiki.

So some of our loss might just be part of the coating.
  61   Sun Nov 4 23:55:24 2007 ranaUpdateIOOFriday's In-Vac work
On Friday morning when closing up we noticed that we could not get the MC to flash any modes.
We tracked this down to a misalignment of MC3. Rob went in and noticed that the stops were
still touching. Even after backing those off the beam from MC3 was hitting the east edge of
the MC tube within 12" of MC3.

This implied a misalignment of MC of ~5 mrad which is quite
large. At the end our best guess is that either I didn't put the indicator blocks in the
right place or that the MC3 tower was not slid all the way back into place. Since there
is such a strong stickiness between the table and the base of the tower its easy to
imagine the tower was misplaced.

So we looked at the beam on MC2 and twisted the MC3 tower. This got the beam back onto the
MC2 cage and required ~1/3 if the MC3 bias range to get the beam onto the center. We used
a good technique of finding that accurately: put an IR card in front of MC2 and then look
in from the south viewport of the MC2 chamber to eyeball the spot relative to the OSEMs.

Hitting MC2 in the middle instantly got us multiple round trips of the beam so we decided
to close up. First thing Monday we will put on the MC1/MC3 access connector and then
pump down.

Its possible that the MC length has changed by ~1-2 mm. So we should remeasure the length
and see if we need to reset frequencies and rephase stuff.
  60   Sun Nov 4 23:22:50 2007 waldmanUpdateOMCOMC PZT and driver response functions
I wrote a big long elog and then my browser hung up, so you get a less detailed entry. I used Pinkesh's calibration of the PZT (0.9 V/nm) to calibrate the PDH error signal, then took the following data on the PZT and PZT driver response functions.:

  • FIgure 1: PZT dither path. Most of the features in this plot are understood: There is a 2kHz high pass filter in the PZT drive which is otherwise flat. The resonance features above 5 kHz are believed to be the tombstones. I don't understand the extra motion from 1-2 kHz.
  • Figure 2: PZT dither path zoom in. Since I want to dither the PZT to get an error signal, it helps to know where to dither. The ADC Anti-aliasing filter is a 3rd order butterworth at 10 kHz, so I looked for nice flat places below 10 KHz and settled on 8 kHz as relatively harmless.
  • Figure 3: PZT LSC path. This path has got a 1^2:10^2 de-whitening stage in the hardware which hasn't been digitally compensated for. You can see its effect between 10 and 40 Hz. The LSC path also has a 160 Hz low path which is visible causing a 1/f between 200 and 500 Hz. I have no idea what the 1 kHz resonant feature is, though I am inclined to point to the PDH loop since that is pretty close to the UGF and there is much gain peaking at that frequency.
Attachment 1: 071103DitherShape.png
Attachment 2: 071103DitherZoom.png
Attachment 3: 071103LSCShape.png
Attachment 4: 071103DitherShape.pdf
Attachment 5: 071103DitherZoom.pdf
Attachment 6: 071103LSCShape.pdf
Attachment 7: 071103LoopShape.pdf
  59   Sat Nov 3 16:20:43 2007 waldmanSummaryOMCA good day's work

I followed up yesterday's test of the PZT with a whole mess of characterizations of the PZT control and finished the day by locking the OMC with a PZT dither lock and a 600 Hz loop. I haven't analyzed any of the data yet, so its not calibrated in physical units and etc. etc. etc. Since a lot of the sweeps below are of a "drive the PZT, look at the PDH signal" nature, a proper analysis will require taking out the loop and calibrating the signals, which alas, I haven't done. Nonetheless, I include all the plots because they are pretty. The files included below are:

  • DitherLock_sweep: Sweep of the IN2/IN1 for the dither lock error point showing 600 Hz UGF
  • HiResPZTDither_sweep: Sweep of the PZT dither input compared to the PDH error signal. I restarted the front end before the sweep was finished accounting for the blip.
  • HiResPZTDither_sweep2: Finish of the PZT dither sweep

More will be posted later.
Attachment 1: 071103_DitherLock_sweep.png
Attachment 2: 071103_DitherLock_sweep.pdf
Attachment 3: 071103_HiResPZTDither_sweep.png
Attachment 4: 071103_HiResPZTDither_sweep.pdf
Attachment 5: 071103_HiResPZTDither_sweep2.png
Attachment 6: 071103_HiResPZTDither_sweep2.pdf
  58   Fri Nov 2 12:18:47 2007 waldmanSummaryOMCLocked OMC with DCPD
[Rich, Sam]

We locked the OMC and look at the signal on the DCPD. Plots included.
Attachment 1: 071102_OMC_LockedDCPD.gif
Attachment 2: 071102_OMC_LockedDCPD.pdf
  57   Fri Nov 2 08:59:30 2007 steveBureaucracySAFETYthe laser is ON
The psl laser is back on !
  56   Thu Nov 1 20:03:00 2007 Andrey RodionovSummaryPhotosProcedure "Drop and Drag" in pictures
Attachment 1: DSC_0072.JPG
Attachment 2: DSC_0083.JPG
Attachment 3: DSC_0099.JPG
Attachment 4: DSC_0100.JPG
  55   Thu Nov 1 19:58:07 2007 Andrey RodionovBureaucracyPhotosSteve and Tobin's picture
Attachment 1: DSC_0023.JPG
  54   Thu Nov 1 19:55:59 2007 Andrey RodionovBureaucracyPhotosAndrey, Tobin, Robert - photo
Attachment 1: DSC_0092.JPG
  53   Thu Nov 1 19:55:03 2007 Andrey RodionovBureaucracyPhotosAndrey's photo
Attachment 1: DSC_0055.JPG
  52   Thu Nov 1 19:54:22 2007 Andrey RodionovBureaucracyPhotosRana's photo
Attachment 1: DSC_0120.JPG
  51   Thu Nov 1 19:53:34 2007 Andrey RodionovBureaucracyPhotosRobert's photo
Attachment 1: DSC_0068.JPG
  50   Thu Nov 1 19:53:02 2007 Andrey RodionovBureaucracyPhotosTobin's picture
Attachment 1: DSC_0053.JPG
  48   Thu Nov 1 16:51:33 2007 d40AoGGeneralD40
If you vant see D40 againn, you leave one plate goulash by N2 tank in morning.

Vit the good paprikash this time!!!
Attachment 1: PB010001.JPG
  47   Thu Nov 1 16:42:48 2007 Andrey RodionovSummaryEnvironmentEnd of Daylight Saving Time this weekend
Useful information for everyone, as a friendly reminder:

According to the web-page


this coming weekend there will be the end of Daylight Saving Time.

Clocks will be adjusted backward one hour.
  46   Thu Nov 1 16:34:47 2007 Andrey RodionovSummaryComputersLimitation on attachment size of E-LOG

I discovered yesterday when I was attaching photos that it is NOT possible to attach files whose size is 10Mb or more. Therefore, 10Mb or something very close to that value is the limit.
  45   Thu Nov 1 11:45:30 2007 tobinConfigurationIOOMode cleaner drag-wiping
Andrey, Bob, David, John Miller, Rana, Rob, Steve, Tobin

Yesterday we vented the vacuum enclosure and opened up the chamber containing MC1 & MC3 by removing the access connector between that chamber and the OMC chamber. Rana marked MC1's location with dogs and then slid the suspension horizontally to the table edge for easy drag-wiping access. The optic was thoroughly hosed-down with the dionizer, in part in an effort to remove dust from the cage and the top of the optic. Drag-wiping commenced with Rob squirting (using the 50 microliter syringe) and Tobin dragging (using half-sheets of Kodak lens tissue). We drag-wiped the optic many (~10) times, concentrating on the center but also chasing around various particles and a smudge on the periphery. There remains one tiny speck at about the 7:30 position, outside of the resonant spot area, that we could not dislodge with three wipes.

Today we drag-wiped MC3. First we slid MC1 back and then slid MC3 out to the edge of the table. We disconnected the OSEM cables in the process for accessibility, and MC1 is perched at an angle, resting on a dog. We did not blow MC3 with the deonizer, not wanting to blow particles from MC3 to the already-cleaned MC1. We drag-wiped MC3 only three times, all downward drags through the optic center, with Steve squirting and Tobin dragging. Some particles are still visible around the periphery, and there appears to be a small fiber lodged near the optic center on the reverse face.

Andrey and Steve have opened up MC2 in preparation for drag-wiping that optic after lunch.
  44   Thu Nov 1 09:17:27 2007 steveRoutineVACvent 64
Yesterday before vent I could not lock MC, therfore I could not measure the
transmitted power at MC2
The vent went well. We had lots of help.

We could not find the Nikon D40
PLEASE BORROW THINGS when taking them away
and bring them back promtly.

The laser was turned off for better visibility.

I see clean room frorks laying around here and there.
Please put them away so we do not carry excess particles into the chamber.
Attachment 1: vent64.jpg
  43   Thu Nov 1 01:28:04 2007 waldmanOtherOMCFirst digital lock of OMC
[Pinkesh, Sam]

We locked a fiber based NPRO to the suspended OMC tonight using the TPT digital control system. To control the laser frequency, we took the PZT AI output and ran it on a BNC cable down the hallway to the Thorlabs HV box. The Thorlabs is a singled ended unit so we connected the AI positive terminal only and grounded the BNC to the AI shield. We could get a -6 to 1.5 V throw in this method which fed into the 10 k resisotr + 9 V battery at the input of the HV box. The HV out ran to the NPRO PZT fast input.

We derived our error signal from a PDA255 in reflection with a 29.5 MHz PDH lock. The signal feeds into one of the unused Tip/Tilt AA channels and is passed to the PZT LSC drive through the TPT_PDH1 filter bank. In the PZT_LSC filter we put a single pole at 1 Hz which, together with the phase we mentioned the other night (180 degrees at 3 kHz) should allow a 1 kHz-ish loop. In practice, as shown below, we got a 650 Hz UGF with 45 degrees of phase margin and about 6 dB of gain margin.

The Lower figure shows the error point spectrum with 3 settings. REF0 in blue shows lots of gain peaking at 1.5 kHz-ish, just where its expected - the gain was -40. The REF1 has gain of -20 and shows no gain peaking. The current trace in red shows some gain peaking cuz the alignment is better but it also has included a 1^2:20^2 boost which totally crushes the low frequency noise. We should do a better loop sweep after getting the alignment right so we can see how much boost it will really take.

Just for fun, we are leaving it locked overnight and recording the PZT_LSC data for posterity.
Attachment 1: 071101_PZT_firstLoopSweep.pdf
Attachment 2: 071101_PZT_firstLoopSweep.gif
Attachment 3: 071101_OMC_FirstLock_spectra.pdf
Attachment 4: 071101_OMC_FirstLock_spectra.gif
  42   Wed Oct 31 23:55:17 2007 waldmanOtherOMCQPD tests
The 4 QPDs for the OMC have been installed in the 056 at the test setup. All 4 QPDs work and have medm screens located under C2TPT. The breadboard mounted QPDs are not very well centered so their signal is somewhat crappy. But all 4 QPDs definitely see plenty of light. I include light and dark spectra below. QPDs 1-2 are table-mounted and QPD 2 is labeled with a bit of blue tape. QDPs 3-4 are mounted on the OMC. QPD3 is the near field detector and QPD4 is the far field. In other words, QPD3 is closest to the input coupler and QPD4 is farthest.

Included below are some spectra of the QPDs with and without light. For QPDs 1 & 2, the light source is just room lights, while 3&4 have the laser in the nominal OMC configuration with a few mWs as source. The noise at 100 Hz is about 100 microvolts / rtHz. If I recall correctly, the QPDs have 5 kOhm transimpedance (right Rich?) so this is 20 nanoamps / rtHz of current noise at the QPD.
Attachment 1: QPD_SignalSpectrum.pdf
Attachment 2: QPD_SignalSpectrum.gif
  41   Wed Oct 31 19:26:08 2007 Andrey RodionovRoutineGeneralPhotographs of "Mode-Cleaner Entrance"

Here are the pictures of "inside the chamber".
Attachment 1: MC-Pictures-1.pdf
MC-Pictures-1.pdf MC-Pictures-1.pdf MC-Pictures-1.pdf MC-Pictures-1.pdf
Attachment 2: MC-Pictures-2.pdf
MC-Pictures-2.pdf MC-Pictures-2.pdf MC-Pictures-2.pdf MC-Pictures-2.pdf
Attachment 3: MC-Pictures-3.pdf
MC-Pictures-3.pdf MC-Pictures-3.pdf MC-Pictures-3.pdf MC-Pictures-3.pdf
Attachment 4: MC-Pictures-4.pdf
MC-Pictures-4.pdf MC-Pictures-4.pdf MC-Pictures-4.pdf MC-Pictures-4.pdf
Attachment 5: MC-Pictures-5.pdf
MC-Pictures-5.pdf MC-Pictures-5.pdf MC-Pictures-5.pdf MC-Pictures-5.pdf
Attachment 6: MC-Pictures-6.pdf
MC-Pictures-6.pdf MC-Pictures-6.pdf MC-Pictures-6.pdf MC-Pictures-6.pdf
Attachment 7: MC-Pictures-7.pdf
MC-Pictures-7.pdf MC-Pictures-7.pdf MC-Pictures-7.pdf MC-Pictures-7.pdf
Attachment 8: MC-Pictures-8.pdf
MC-Pictures-8.pdf MC-Pictures-8.pdf MC-Pictures-8.pdf MC-Pictures-8.pdf
Attachment 9: MC-Pictures-9.pdf
MC-Pictures-9.pdf MC-Pictures-9.pdf
  40   Wed Oct 31 15:22:59 2007 robConfigurationIOOMode Cleaner transfer function
I measured the transfer function of the input mode cleaner using a PDA255 and the ISS. First I put the PD in front of the ISS out-of-loop monitor diode and used an SR785 to measure the swept sine transfer function from the Analog IN port of the ISS to the intensity at the PD. Then I moved the PD to detect the light leaking out from behind MC2, using ND filters to get the same DC voltage, and measured the same transfer function. Dividing these two transfer functions should take out the response of the ISS and the PD, and leave just the transfer function of the MC. A plot of the data, along with a single-pole fit, are attached.

The fit is pretty good for a single pole at 3.79 kHz. There's a little wiggle around 9kHz due to ISS weirdness (as Tobin has not been giving it the attention it requires), but this shouldn't affect this result too much. Using the known MC length of 27.0955m, and assuming that MC1 and MC3 have a power transmissivity of 2000ppm and MC2 is perfectly reflecting, the total round trip loss should be about 300ppm. The fitted finesse is 1460.
Attachment 1: MCtf.pdf
  39   Wed Oct 31 15:02:59 2007 tobinRoutineIOOMode Cleaner Mode Tracking
I processed the heterodyned mode cleaner data yesterday, tracking the three 28 kHz modes corresponding to MC1, MC2, and MC3. Unfortuntately the effect of our MC power chopping is totally swamped by ambient temperature changes. Attached are two plots, one with the tracked mode frequencies, and the other containing dataviewer trends with the MC transmitted power and the room temperature. Additionally, the matlab scripts are attached in a zip file.
Attachment 1: mode-track.pdf
Attachment 2: trends.pdf
Attachment 3: mcmodetrack.zip
  38   Wed Oct 31 10:31:23 2007 Andrey RodionovRoutineVACVenting is in progress

We (Steve, David, Andrey) started venting the vacuum system at 9.50AM Wednesday morning.
  37   Wed Oct 31 09:45:28 2007 waldmanOtherOMCResolution to DAQland saga
[Jay, Sam]

We did a rough accounting for the linear delay this morning and it comes out more or less correct. The 10 kHz 3rd order butterworth AA/AI filter gives ~90 degrees of phase at 6 kHz, or 42 microseconds. Taken together, the two AA and AI filters are worth 80 microseconds. The 1.5 sample digital delay is worth 1.5/32768 = 45 microseconds. The remaining 160 - 125 = 35 microseconds is most likely taken up by the 64 kHz to 32 kHz decimation routine, assuming this isn't accounted for already in the 1.5 sample digital delay.

It remains to be seen whether this phase delay is good enough to lock the laser to the OMC cavity
  36   Wed Oct 31 08:38:35 2007 ranaProblem FixedIOOMC autolocker
The MC was having some trouble staying locked yesterday. I tracked this down to some steps in the last
half of the mcup script; not sure exactly which ones.

It was doing something that made the FAST of the PSL go to a rail too fast for the SLOW to fix.
So, I broke the script in half so that the autolocker only runs the first part. We'll need to
fix this before any CM locking can occur.

We also need someone to take a look at the FSS Autolocker; its ill.
  35   Wed Oct 31 08:34:35 2007 ranaOtherIOOloss measurements
In the end, we were unable to get a good scatter measurement just because we ran out of steam. The idea was to get a frame
grab image of MC2 but that involves getting an unsaturated image.

In the end we settle for the ringdowns, Rob's (so far unlogged) cavity pole measurement, and the MC transmission numbers. They
all point to ~100-150 ppm scatter loss per mirror. We'll see what happens after wiping.
  34   Wed Oct 31 08:33:54 2007 ranaProblem FixedSUSVent measurements
There was a power outage during the day yesterday; whoever was around should post something here about the
exact times. Andrey and David and Tobin got the computers back up - there were some hiccups which you can
read about in David's forthcoming elog entry.

We restarted a few of the locking scripts on op340m: FSSSlowServo, MCautolocker. Along with the updates
to the cold restart procedures we have to put an entry in there for op340m and a list of what scripts
to restart.

David tuned up the FSS Slow PID parameters a little; he and Andrey will log some entry about the proper
PID recipe very soon. We tested the new settings and the step response looks good.

We got the MC locking with no fuss. The 5.6 EQ in San Francisco tripped all of the watchdogs and I upped
the trip levels to keep them OK. We should hound Rob relentlessly to put the watchdog rampdown.pl into
the crontab for op340m.
  33   Tue Oct 30 20:15:24 2007 tobinOtherEnvironmentearthquake
Rana, Tobin

Largish (M5.6) earthquake in San Francisco sent our optics swinging.
  32   Tue Oct 30 19:32:13 2007 tobinProblem FixedComputersconlogger restarted
I noticed that the conlogger wasn't running. It looks like it hasn't been running since October 11th. I modified the restart_conlogger script to insist that it run on op340m instead of op440m, and then ran it on op340m.
ELOG V3.1.3-