| ID |
Date |
Author |
Type |
Category |
Subject |
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79
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Wed Nov 7 14:01:31 2007 |
waldman | Omnistructure | OMC | Frequency 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.... |
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78
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Wed Nov 7 13:54:44 2007 |
rob | Configuration | IOO | Mode 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.
|
What | Then | Now
| |
pole frequency | 3.789kHz | 3.765kHz
| |
loss per optic | 99ppm | 91ppm
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finesse | 1460 | 1470
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trans | 86.7% | 87.7%
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| Attachment 1: mctf.pdf
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77
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Wed Nov 7 10:55:21 2007 |
ajw | Configuration | Computers | backup 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.) |
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76
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Wed Nov 7 09:38:01 2007 |
steve | Update | VAC | rga scan |
| pd65-m-d2 at cc1 6e-6 torr |
| Attachment 1: pd65d2.jpg
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75
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Wed Nov 7 02:14:08 2007 |
Andrey | Bureaucracy | IOO | More 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
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| Attachment 2: image-attempt_2.png
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| Attachment 3: image-attempt_3.png
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| Attachment 4: image-attempt_4.png
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| Attachment 5: image-attempt_5.png
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| Attachment 6: Fit-1st_attempt.jpg
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| Attachment 7: Fit-5th_attempt.jpg
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| Attachment 8: 7_Nov_1941-parad-na-krasnoy-ploschadi.jpg
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| Attachment 9: parad1984-moskva.jpg
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74
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Wed Nov 7 00:51:33 2007 |
andrey, rob, tobin | Configuration | IOO | MC ringdowns |
| We completed several ringdown measurements this afternoon; Andrey is currently processing the data. |
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73
|
Tue Nov 6 23:45:38 2007 |
tobin | Configuration | Computers | tektronix 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. |
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72
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Tue Nov 6 18:18:15 2007 |
tobin | Configuration | Computers | I 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". |
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71
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Tue Nov 6 16:48:54 2007 |
tobin | Configuration | Computers | scopes on the net |
I configured our two 100 MHz Tektronix 3014B scopes with IP addresses: 131.215.113.24 (scope0) and 113.215.113.25 (scope1). Let the scripting commence!
There appears to be a Matlab Instrument Control Toolbox driver for this scope. |
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70
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Tue Nov 6 15:37:34 2007 |
rob | Configuration | SUS | rampdown 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. |
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69
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Tue Nov 6 15:36:03 2007 |
rob | Update | LSC | XARM 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. |
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68
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Tue Nov 6 14:51:03 2007 |
tobin, rob | Update | IOO | Mode 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
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Tue Nov 6 10:42:01 2007 |
rob | Configuration | IOO | mode 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. |
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66
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Tue Nov 6 09:45:22 2007 |
steve | Summary | SUS | vent 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
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65
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Tue Nov 6 09:14:37 2007 |
steve | Summary | VAC | pump 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
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64
|
Mon Nov 5 22:24:38 2007 |
Andrey, Steve | Omnistructure | VAC | Pumping 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. |
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63
|
Mon Nov 5 14:44:39 2007 |
waldman | Update | OMC | PZT 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
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| Attachment 2: 071105_LSCtoVmonDC_sweep4-0.png
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| Attachment 3: 07110_DithertoVmonAC_sweep2.pdf
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| Attachment 4: 071105_LSCtoVmonDC_sweep4.pdf
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62
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Mon Nov 5 07:29:35 2007 |
rana | Update | IOO | Friday'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. |
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61
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Sun Nov 4 23:55:24 2007 |
rana | Update | IOO | Friday'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
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Sun Nov 4 23:22:50 2007 |
waldman | Update | OMC | OMC 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.
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| Attachment 1: 071103DitherShape.png
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| Attachment 2: 071103DitherZoom.png
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| Attachment 3: 071103LSCShape.png
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| Attachment 4: 071103DitherShape.pdf
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| Attachment 5: 071103DitherZoom.pdf
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| Attachment 6: 071103LSCShape.pdf
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| Attachment 7: 071103LoopShape.pdf
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59
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Sat Nov 3 16:20:43 2007 |
waldman | Summary | OMC | A 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
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| Attachment 2: 071103_DitherLock_sweep.pdf
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| Attachment 3: 071103_HiResPZTDither_sweep.png
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| Attachment 4: 071103_HiResPZTDither_sweep.pdf
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| Attachment 5: 071103_HiResPZTDither_sweep2.png
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| Attachment 6: 071103_HiResPZTDither_sweep2.pdf
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58
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Fri Nov 2 12:18:47 2007 |
waldman | Summary | OMC | Locked 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
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| Attachment 2: 071102_OMC_LockedDCPD.pdf
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57
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Fri Nov 2 08:59:30 2007 |
steve | Bureaucracy | SAFETY | the laser is ON |
| The psl laser is back on ! |
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56
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Thu Nov 1 20:03:00 2007 |
Andrey Rodionov | Summary | Photos | Procedure "Drop and Drag" in pictures |
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| Attachment 1: DSC_0072.JPG
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| Attachment 2: DSC_0083.JPG
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| Attachment 3: DSC_0099.JPG
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| Attachment 4: DSC_0100.JPG
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55
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Thu Nov 1 19:58:07 2007 |
Andrey Rodionov | Bureaucracy | Photos | Steve and Tobin's picture |
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| Attachment 1: DSC_0023.JPG
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54
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Thu Nov 1 19:55:59 2007 |
Andrey Rodionov | Bureaucracy | Photos | Andrey, Tobin, Robert - photo |
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| Attachment 1: DSC_0092.JPG
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53
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Thu Nov 1 19:55:03 2007 |
Andrey Rodionov | Bureaucracy | Photos | Andrey's photo |
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| Attachment 1: DSC_0055.JPG
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52
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Thu Nov 1 19:54:22 2007 |
Andrey Rodionov | Bureaucracy | Photos | Rana's photo |
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| Attachment 1: DSC_0120.JPG
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51
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Thu Nov 1 19:53:34 2007 |
Andrey Rodionov | Bureaucracy | Photos | Robert's photo |
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| Attachment 1: DSC_0068.JPG
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50
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Thu Nov 1 19:53:02 2007 |
Andrey Rodionov | Bureaucracy | Photos | Tobin's picture |
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| Attachment 1: DSC_0053.JPG
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48
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Thu Nov 1 16:51:33 2007 |
d40 | AoG | General | D40 |
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
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47
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Thu Nov 1 16:42:48 2007 |
Andrey Rodionov | Summary | Environment | End of Daylight Saving Time this weekend |
Useful information for everyone, as a friendly reminder:
According to the web-page
http://www.energy.ca.gov/daylightsaving.html,
this coming weekend there will be the end of Daylight Saving Time.
Clocks will be adjusted backward one hour. |
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46
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Thu Nov 1 16:34:47 2007 |
Andrey Rodionov | Summary | Computers | Limitation 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. |
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45
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Thu Nov 1 11:45:30 2007 |
tobin | Configuration | IOO | Mode 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. |
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44
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Thu Nov 1 09:17:27 2007 |
steve | Routine | VAC | vent 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
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43
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Thu Nov 1 01:28:04 2007 |
waldman | Other | OMC | First 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
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| Attachment 2: 071101_PZT_firstLoopSweep.gif
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| Attachment 3: 071101_OMC_FirstLock_spectra.pdf
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| Attachment 4: 071101_OMC_FirstLock_spectra.gif
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42
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Wed Oct 31 23:55:17 2007 |
waldman | Other | OMC | QPD 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
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| Attachment 2: QPD_SignalSpectrum.gif
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41
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Wed Oct 31 19:26:08 2007 |
Andrey Rodionov | Routine | General | Photographs of "Mode-Cleaner Entrance" |
Here are the pictures of "inside the chamber". |
| Attachment 1: MC-Pictures-1.pdf
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| Attachment 2: MC-Pictures-2.pdf
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| Attachment 3: MC-Pictures-3.pdf
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| Attachment 4: MC-Pictures-4.pdf
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| Attachment 5: MC-Pictures-5.pdf
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| Attachment 6: MC-Pictures-6.pdf
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| Attachment 7: MC-Pictures-7.pdf
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| Attachment 8: MC-Pictures-8.pdf
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| Attachment 9: MC-Pictures-9.pdf
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40
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Wed Oct 31 15:22:59 2007 |
rob | Configuration | IOO | Mode 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
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Wed Oct 31 15:02:59 2007 |
tobin | Routine | IOO | Mode 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
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| Attachment 2: trends.pdf
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| Attachment 3: mcmodetrack.zip
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Wed Oct 31 10:31:23 2007 |
Andrey Rodionov | Routine | VAC | Venting is in progress |
We (Steve, David, Andrey) started venting the vacuum system at 9.50AM Wednesday morning. |
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Wed Oct 31 09:45:28 2007 |
waldman | Other | OMC | Resolution 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 |
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Wed Oct 31 08:38:35 2007 |
rana | Problem Fixed | IOO | MC 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. |
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Wed Oct 31 08:34:35 2007 |
rana | Other | IOO | loss 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. |
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Wed Oct 31 08:33:54 2007 |
rana | Problem Fixed | SUS | Vent 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. |
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Tue Oct 30 20:15:24 2007 |
tobin | Other | Environment | earthquake |
Rana, Tobin
Largish (M5.6) earthquake in San Francisco sent our optics swinging. |
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Tue Oct 30 19:32:13 2007 |
tobin | Problem Fixed | Computers | conlogger 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. |
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Tue Oct 30 16:55:40 2007 |
tobin | Routine | | Drag-wiping perfected |
Steve, Tobin
Steve procured an assortment of syringes from the bio storeroom and we practiced drag-wiping the SOS in the flow bench. Using a 50 microliter Hamilton syringe to deliver 16 microliters of methanol seems perfect for drag-wiping the small optics. Drag-wiping in the downward direction seems to work very well, since we can squirt the optic directly in the center, and the (half) piece of kodak lens tissue fits easily between the bottom two earthquake stops. |
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Tue Oct 30 13:58:07 2007 |
ajw | Configuration | IOO | MC Ringdowns |
Here's a quick fit-by-eye to the latter part of the data from tek00000.xls.
The prediction (blue) is eqn 41 of
http://www.ligo.caltech.edu/docs/P/P000017-A.pdf
T1 = T2 = 0.002. Loss1 = Loss2 = 150 ppm.
MC3 assumed perfectly reflecting.
Velocity = 320 um/s (assumed constant), 2 usec into the ringdown.
OK, there's one little fudge factor in the prediction:
I multiplied D by 2. |
| Attachment 1: CavityRingdown.png
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| Attachment 2: CavityRingdown.m
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% CavityRingdown.m
% Eqn 41 of
% "Doppler-induced dynamics of fields in Fabry–Perot
% cavities with suspended mirrors", Malik Rakhmanov (2000).
% http://www.ligo.caltech.edu/docs/P/P000017-A.pdf
clear all
% read in ringdown timeseries:
at = importdata('tek00000.csv');
... 121 more lines ...
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Tue Oct 30 00:47:29 2007 |
rana | Other | IOO | MC Ringdowns |
I did a bunch of MC ringdown measurements using the PD that Rob set up. The idea is to put a fast PD (PDA255)
looking at the transmission through MC2 after focusing by a fast lens. The input to the MC is turned off fast
by flipping the sign of the FSS (Andri Gretarsson's technique).
With the laptop sitting on the MC can, its easy to repeat many ringdowns fast:
- Turn off the MC autolocker. Relock the MC with only the acquisition settings; no boosts
and no RGs. This makes it re-acquire fast. Turn the MC-WFS gain down to 0.001 so that
it keeps it slowly aligned but does not drift off when you lose lock.
- Use low-ish gain on the FSS. 10 dB lower than nominal is fine.
- Setup the o'scope (100 MHz BW or greater) to do single shot trigger on the MC2 trans.
- Flip FSS sign.
- Quickly flip sign back and waggle common gain to get FSS to stop oscillating. MC
should relock in seconds.
Clearly one can scriptify this all just by hooking up the scope to the ethernet port.
Attached are a bunch of PNG of the ringdowns as well as a tarball with the actual data. A sugar
napoleon to whomever can explain the 7 us period of the wiggle before the vent! |
| Attachment 1: tek00000.png
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| Attachment 2: tek00001.png
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| Attachment 3: tek00004.png
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| Attachment 4: MC2ringdown.tar.gz
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