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ID Date Authordown Type Category Subject
  2378   Thu Dec 10 08:50:33 2009 AlbertoUpdateComputersFronte-ends down

Quote:

I found all the front-ends, except for C1SUSVME1 and C0DCU1 down this morning. DAQAWG shows up green on the C0DAQ_DETAIL screen but it is on a "bad" satus.

I'll go for a big boot fest.

Since I wanted to single out the faulting system when these situations occur, I tried to reboot the computers one by one.

1) I reset the RFM Network by pushing the reset button on the bypass switch on the 1Y7 rack. Then I tried to bring C1SOSVME up by power-cycling and restarting it as in the procedure in the wiki. I repeated a second time but it didn't work. At some point of the restarting process I get the error message "No response from EPICS".
2) I also tried rebooting only C1DCUEPICS but it didn't work: I kept having the same response when restarting C1SOSVME
3) I tried to reboot C0DAQCTRL and C1DCU1 by power cycling their crate; power-cycled and restarted C1SOSVME. Nada. Same response from C1SOSVME.
4) I restarted the framebuilder;  power-cycled and restarted C1SOSVME. Nothing. Same response from C1SOSVME.
5) I restarted the framebuilder, then rebooted C0DAQCTRL and C1DCU, then power-cycled and restarted C1SOSVME. Niente. Same response from C1SOSVME.
 
Then I did the so called "Nuclear Option", the only solution that so far has proven to work in these circumstances. I executed the steps in the order they are listed, waiting for each step to be completed before passing to the next one.
0) Switch off: the frame builder, the C0DAQCTRL and C1DCU crate, C1DCUEPICS
1) turn on the frame builder
2) reset of the RFM Network switch on 1Y7 (although, it's not sure whether this step is really necessary; but it's costless)
3) turn on C1DCUEPICS
4) turn on the C0DAQCTRL and C1DCU crate
5) power-cycle and restart the single front-ends
6) burt-restore all the snapshots
 
When I tried to restart C1SOSVME by power-cycling it I still got the same response: "No response from EPICS". But I then reset C1SUSVME1 and C1SUSVME2 I was able to restart C1SOSVME.
 
It turned out that while I was checking the efficacy of the steps of the Grand Reboot to single out the crucial one, I was getting fooled by C1SOSVME's status. C1SOSVME was stuck, hanging on C1SUSVME1 and C1SUSVME2.
 
So the Nuclear option is still unproven as the only working procedure. It might be not necessary.
 
Maybe restating BOTH RFM switches, the one in 1Y7 and the one in 1Y6, would be sufficient. Or maybe just power-cycling the C0DAQCTRL and C1DCU1 is sufficient. This has to be confirmed next time we incur on the same problem.
  2384   Thu Dec 10 13:10:25 2009 AlbertoConfigurationLSC166 LO Disconnected

I temporarily disconnected the Heliax cable that brings the 166MHz LO to the LSC rack.

I'm doing a couple of measurement and I'll put it back in as soon as I'm done.

  2389   Thu Dec 10 17:05:21 2009 AlbertoConfigurationLSC166 MHz LO SMA-to-Heliax connection repaired

I replaced the SMA end connector for the 166 MHZ Local Oscillator signal that goes to the back of the flange in the 1Y2 rack. The connector had got damaged after it twisted when I was tigheting the N connector of the Heliax cable on the front panel.

  2393   Thu Dec 10 18:31:44 2009 AlbertoConfigurationLSC166 LO Disconnected

Quote:

I temporarily disconnected the Heliax cable that brings the 166MHz LO to the LSC rack.

I'm doing a couple of measurement and I'll put it back in as soon as I'm done.

 These are the losses I measured on a RG-174 cable for the two frequencies that we're planning to use in the Upgrade:

@11MHz Loss=0.22dBm/meter

@55MHz Loss=0.41dBm/meter

(The cable was 2.07m long. The input signal was +10dBm and the output voltages at the oscilloscope where: Vpk-pk(11MHz)=1.90V, Vpk-pk(11MHz)=1.82V )

  2396   Fri Dec 11 11:42:26 2009 AlbertoConfigurationLSC166 LO Disconnected

Quote:

They must not be dBm, must be dB

Quote:

Quote:

I temporarily disconnected the Heliax cable that brings the 166MHz LO to the LSC rack.

I'm doing a couple of measurement and I'll put it back in as soon as I'm done.

 These are the losses I measured on a RG-174 cable for the two frequencies that we're planning to use in the Upgrade:

@11MHz Loss=0.22dBm/meter

@55MHz Loss=0.41dBm/meter

(The cable was 2.07m long. The input signal was +10dBm and the output voltages at the oscilloscope where: Vpk-pk(11MHz)=1.90V, Vpk-pk(11MHz)=1.82V )

 

I apologize for the lack of correctness on the units in yesterday's elog entry, but I wasn't very sharp last night.

I repeated the measurement today, this time also making sure that I had a 50ohm input impedance set in the scope. These the results for the losses.

RG-174 Cable 0.053 dB/m @ 11MHz  0.155 dB/m @ 55 MHz

 I also measured the losses in the Heliax cable going from the 166 MHz LO to the LSC rack:

166MHz LO Heliax 0.378 dB @ 11MHz  1.084 dB @ 55 MHz

 

  2397   Fri Dec 11 13:18:17 2009 AlbertoConfigurationVACpumpdown has started

Quote:

Oplev positions before and after drag wiped arm TMs as of yesterday. Slow-mode pumpdown has started with 3/4 turn opened  RV1 valve at 8am today.

 I'm leaving the lab now for less than 2 hours. I should be back in time for when the pumping is finished so that I can measure the finesse again.

  2402   Fri Dec 11 19:51:13 2009 AlbertoConfigurationLSC166 LO Disconnected

Quote:

 

 Seems like very strange cable loss numbers. The Heliax is lossier than the RG-174? I wonder how these compare with the specs in the cable catalog?

In my last entry there was a typo for the measurement of the Heliax at 55 MHz. I corrected it. It was 1.084 dB instead of 1.084 dB/m.
For the Heliax I don't have the measurement of the loss per meter since I don't know the cable actual length.
 
Except for that, I checked the values I found on the Internet.
My measurements for the RG-174 seem comparable to the loss specified in the catalog (here): 6.6dB in 100ft @ 55 MHz, that is 0.22 dB/m, that compare with 0.155 dB/m that I measured.

I did the measurement on a 4.33 meter long cable with SMA connectors at the ends.

  2413   Mon Dec 14 14:16:14 2009 AlbertoUpdateTreasureLOCKSTARS

Quote:

Good job guys. What I did was saying "I don't know", "Maybe", and "Ants...".

Now you can proceed to measurements for the visibility and the cavity pole! 

Quote:

[Jenne, Kiwamu, Koji]

We got the IFO back up and running!  After all of our aligning, we even managed to get both arms locked simultaneously.  

 I'm going to do it right now.

  2415   Mon Dec 14 19:33:04 2009 AlbertoUpdateGeneralArm Cavity Poles measured again after cleaning the optics last week

Last week we vented and we cleaned the main optics of the arm cavities.

I measured the frequency of the cavity poles for both the arm cavities to see how they changed (see previous elog entry 2226). These the results:

fp_X = 1616 +/- 14 Hz

fp_Y = 1590 +/- 4 Hz

The error is the statistical error that I got with the Matlab NonLinearLeastSquare fitting function.
 
I calculated the cavity pole frequencies by measuring the transfer function between a photodiode located at the end of the arms (either X or Y) and another photodiode placed after the mode cleaner. Both diodes where Thorlabs PDA255.
(Last time, I had measured that the pair of diode had a flat calibration).
 
With the SR785 I measured the transfer function by exciting the OMC_ISS_EXC input cable.
For both arms I set to 1V the excitation amplitude. I repeated the measurements for different excitation amplitudes without observing any changes.
I then fitted the data with the NonLinearLeastSquare function of matlab. The script I wrote to do that is attached to this entry in a compressed file.
The files also contains the PDF with the output plots and the data from both set of measurements performed before and after the cleaning.
The data is commented in a file called measurements.log.
 
In the end I disabled again the test switch on the ISS MEDM screen.
I disconnected the excitation cable from the OMC_ISS_EXC input cable.
I removed the photodiode that measured the Mode Cleaner transmission from the PSL clearing the way for the beam to get back to its path to the RFAM photodiode.
  2418   Tue Dec 15 05:29:31 2009 AlbertoUpdateGeneralArm Cavity Poles measured again after cleaning the optics last week

 

 The Y arm cavity pole moved down by 130 Hz, whereas the X arm moved by only 34 Hz. I wonder if that is because Kiwamu spent much more time on cleaning ITMY than on any other optic.

  2420   Tue Dec 15 21:39:34 2009 AlbertoUpdateABSLbrief summary of this afternoon's measurements
I took measurements of the open loop gain of the AbsL PLL with the old Universal PDH Box.
I Also measured the filter shape of both the new and the old PDH box.
I'm going to plot the results in a nice form tomorrow morning.
For who's interested, the PLL UGF was at 10KHz.
 
I can't lock the PLL with the new PDH box. Measuring its filter's shape, as suggested by Koji, I found out that it differs from the old one. That despite the fact that the two boxes should share the same circuit schematic. O,r at least, that is what it looks like from the schematics in the DCC.
I need to understand whether that is intentional and, if that was the case, what kind of use  Rich Abbott designed it for.
 
Tomorrow I'm going to post in the elog the filter's transfer functions too.
 
Before leaving the lab I closed the auxiliary laser's mechanical shutter.
  2421   Wed Dec 16 11:21:20 2009 AlbertoUpdateABSLUniversal PDH Box Servo Filters
Yesterday I measured the shape of the servo filter of both the old and the new Universal PDH boxes.
Here they are compared.

NewandOlfFilterTF.png

The way the filter's transfer function has been measured is by a swept sine between the "SERVO INPUT" and the "PIEZO DRIVE OUTPUT" connection on the box front panel. The spectrum analyzer used for the measurement is the SR785 and the source amplitude is set at 0.1V.

The two transfer functions are clearly different. In particular the old one looks like a simple integrator, whereas the new one already includes some sort of boost.

That probably explains why the new one is unable to lock the PLL. Indeed what the PLL needs, at least to acquire lock, is an 1/f filter.

I thought the two boxes were almost identical, at least in the filter shapes. Also the two schematics available in the DCC coincide.

  2422   Wed Dec 16 11:46:25 2009 AlbertoUpdateABSLAbsl PLL Open Loop Gain

Yesterday I measured the Open Loop Gain of the PLL in the absolute length experiment. The servo I used was that of the old Universal PDH box.

The OLG looks like this:

OldBoxOLTF.png

The UGF is at 10 KHz.

  2427   Thu Dec 17 09:30:08 2009 AlbertoHowToComputersNodus sluggish

The elog has been quite slow for the last two days. The cause is nodus, that has been slowing down the access to it.

I looked at the list of the running processes on nodus by typing the command prstat, which is the equivalent for Solaris of the Linux "top". I didn't see any particular process that might be absorbing too many resources.

I remember Rana fixing the same problem in the past but couldn't find his elog entry about that. Maybe we should just restart nodus, unless someone has some other suggestion.

  2428   Thu Dec 17 17:13:50 2009 AlbertoOmnistructureEnvironmentSTACIS stuff
One of the electronics benches is currently occupied by the STACIS equipment.
We need that table If no one is working on the STACIS anymore, it should be removed from there.
  2429   Thu Dec 17 19:03:14 2009 AlbertoHowToComputersNodus sluggish

Quote:

The elog has been quite slow for the last two days. The cause is nodus, that has been slowing down the access to it.

I looked at the list of the running processes on nodus by typing the command prstat, which is the equivalent for Solaris of the Linux "top". I didn't see any particular process that might be absorbing too many resources.

I remember Rana fixing the same problem in the past but couldn't find his elog entry about that. Maybe we should just restart nodus, unless someone has some other suggestion.

 Problem solved. Nodus and the elog are running fine. It's just that the elog takes some time to make a preview of complex pdf attachments, like those in Kiwamu's entry 2405.

  2459   Mon Dec 28 15:19:19 2009 AlbertoUpdateComputersBurtrestored to Dec 26 at 20:00

Since it wasn't sure whether all the front-ends had been restored after the bootfest, I burtrestored everything to Dec 26 at 20:00.

Always keep in mind that to burtrestore c1dcuepics, the snapshot file has to be modified by hand by moving the last quote up to the line before the last.

  2460   Mon Dec 28 15:34:14 2009 AlbertoUpdateABSLWorking on the AP table

I opened the auxiliary laser's shutter.

I'm currently working on the AP table.

  2461   Mon Dec 28 18:35:27 2009 AlbertoUpdateABSLWorking on the AP table

Quote:

I opened the auxiliary laser's shutter.

I'm currently working on the AP table.

 I finished working on the table.

I closed the AUX NPRO's shutter.

  2467   Wed Dec 30 10:58:48 2009 AlbertoUpdateGeneralAll watchdogs tripped this morning

This morning I found all the watchdogs had tripped during the night.

I restored them all.

I can't damp ITMX. I noticed that its driving matrix is all 1s and -1s as the the right values had been lost in some previous burtrestoring.

  2476   Tue Jan 5 09:18:38 2010 AlbertoOmnistructureElectronicsUniversal PDH Box Stored in the RF Cabinet

FYI: I stored the Universal PDH boxes in the RF cabiner in the Y arm.

  2479   Tue Jan 5 13:23:45 2010 AlbertoOmnistructureEnvironmentturning page

In the lab there are lots of old posters with outdated autocad drawings, or printouts with schematics of old electronics hanging on the walls.

Can we get rid of those and start giving the lab a fresh and modern look?

  2485   Fri Jan 8 10:03:04 2010 AlbertoOmnistructureLSCSPOB shutter was closed

This morning I found that there was no light on the SPOB PD. I went looking at the photodetector and I found that the shutter in front of it was closed.

I switched the shutter driver from n.c. to n.o. which had the effect of opening it.

I guess we inadvertently closed the shutter with Rana when last week we were tinkering with the ITMY  camera.

  2491   Sat Jan 9 09:47:03 2010 AlbertoUpdateLSCProblems trying to lock the arms

This morning I've been having problems in trying to lock the X arm.

The X arm's filter FM6 in the LSC screen starts blinking as it was halfloaded. Then the transmitted power drops from 1 to ~0.5 and eventually the arm loses lock.
To me it looked like a computer related issue. So I decide to reboot C1ISCEX by powercycling it.

That doesn't seem to have solved the problem. The X arm can get locked but TRX slowly moves between 0.2 and 1.

  2492   Sat Jan 9 11:07:30 2010 AlbertoUpdateLSCProblems trying to lock the arms

Quote:

This morning I've been having problems in trying to lock the X arm.

The X arm's filter FM6 in the LSC screen starts blinking as it was halfloaded. Then the transmitted power drops from 1 to ~0.5 and eventually the arm loses lock.
To me it looked like a computer related issue. So I decide to reboot C1ISCEX by powercycling it.

That doesn't seem to have solved the problem. The X arm can get locked but TRX slowly moves between 0.2 and 1.

The X arm is now locked with TRX stable at ~1.

I think earlier on today I was having problems with running the alignment scripts from op540. Now I'm controlling the IFO from Rosalba and I can easily and stably lock all degrees of freedom.

I needed the X arm to be locked to align the auxiliary beam of the AbsL experiment to the IFO. To further stabilize TRX I increased the loop gain from 1 to 1.5.

Now the auxiliary beam is well aligned to the IFO and the beat is going through the PRC. I'm finally ready to scan the recycling cavity.

I also changed the gain of the PRC loop from -0.1 to -0.5.

  2493   Sat Jan 9 15:02:01 2010 AlbertoUpdateABSLPRC scanning
I scanned the PRC in the frequency range of 30-60 MHz, untill the PLL lost lock. But everything is working fine.
The PRC remained lock for all time, with SPOB at ~1000.
I'm leaving the lab now, planning to come back tomorrow.
I turned the flipping mirrors down and closed the mechanical shutter of the auxiliary NPRO.
  2496   Sun Jan 10 16:05:51 2010 AlbertoOmnistructureEnvironmentLab Thermostats Temperature Lowered by 1 deg F

Rana noticed that recently the temperature inside the lab has been a little bit too high. That might be causing some 'unease' to the computers with the result of making them crash more often.

Today I lowered the temperature of the three thermostats that we have inside the lab by one degree:
Y arm thermostat: from 71 to 70 F
X arm thermostat: from 70 to 69 F
Aisle thermostat: from 72 to 71 F.

For the next hours I'll be paying attention to the temperature inside the lab to make sure that it doesn't go out of control and that the environment gets too cold.

  2500   Mon Jan 11 09:18:44 2010 AlbertoUpdateGeneralMeasurement running

I'm working on the AbsL experiment. A measurement which involved the PRC locked is running at the moment.

Please make sure of not interfering with the interferometer until it is done. Thank you.

  2501   Mon Jan 11 10:01:06 2010 AlbertoOmnistructureEnvironmentLab Thermostats Temperature Lowered by 1 deg F

Quote:

Rana noticed that recently the temperature inside the lab has been a little bit too high. That might be causing some 'unease' to the computers with the result of making them crash more often.

Today I lowered the temperature of the three thermostats that we have inside the lab by one degree:
Y arm thermostat: from 71 to 70 F
X arm thermostat: from 70 to 69 F
Aisle thermostat: from 72 to 71 F.

For the next hours I'll be paying attention to the temperature inside the lab to make sure that it doesn't go out of control and that the environment gets too cold.

 Today the lab is perceptibly cooler.

The temperature around the corner is 73 F.

  2502   Mon Jan 11 11:06:53 2010 AlbertoUpdateABSLMeasurement running

Quote:

I'm working on the AbsL experiment. A measurement which involved the PRC locked is running at the moment.

Please make sure of not interfering with the interferometer until it is done. Thank you.

 I'm done for the moement.

I realized that I need to take into account somehow the DC power from the photodiode. By now the measurement of the transmitted beat's power is affected by the total power circulating inside of the PRC and thus it depends on the cavity alignment.

I closed the laser shutter and turned down the flipping mirrors.

I'm planning to restart measuring by 2.30pm today. Till then the interferometer is available.

  2504   Mon Jan 11 16:59:14 2010 AlbertoUpdateABSLInterferometer Busy

I'm currently running a measurement on the PRC.

Please don't interfere with the IFO until it is done. Talk with Alberto if you've been intending to work inside the lab.

Thank you.

  2505   Mon Jan 11 19:36:13 2010 AlbertoUpdateABSLMeasurement running

Leaving for dinner. Back in ~1hr.

I left a measurement running. Please don't interfere with it till I'm back. Thanks.

  2508   Tue Jan 12 09:37:05 2010 AlbertoUpdateABSLIFO available

I finished measuring the AbsL for this morning. The IFO is again available.

Please don't mess up with the interferometer though. I'll be back in a couple of ours

  2512   Wed Jan 13 12:01:06 2010 AlbertoUpdateComputersc1dcuepics, c1lsc rebooted this morning
Since last night the alignemtn scripts couldn't work.
c1lsc wasn't working properly because attempts to lock the X arm would try to control ETMY and attempts of locking the Y arm, wouldn't actuate any optics.
Also, another sign of a malfunctioning c1lsc was that one of the LSC filter modules, FM6, couldn't get loaded properly. It looked like only half loaded on the LSC MEDM screen.
On the other hand, plotting the trend of the last month, c1lsc's CPU didn't look more loaded that usual.
 
Rebooting and restarting C1lsc wasn't enough and I also had to reboot c1dcuepics a couple of times beforse getting things back to work.
  2513   Wed Jan 13 12:03:00 2010 AlbertoUpdateABSLMeasurement now running. Please be careful

At the moment I'm running a measurement on the PRC and I'm planning to leave it going for the time we'll be at the 40m meeting.

Please be careful in the lab. Thank you.

  2519   Sun Jan 17 19:18:55 2010 AlbertoUpdateComputersBoot fest to restart the computer and c1iscey not responding.

Thi afternoon I found that the RFM network in trouble. The frontends sync counters had railed to 16384 counts and some of the computers were not responding. I went for a bootfest, but before I rebooted c1dcu epics. I did it twice. Eventually it worked and I could get the frontends back to green.

Although trying to burtrestore to snapshots taken at any time after last wednesday till today would make the RFM crash again. Weird.

Also, c1iscey seems in a coma and doesn't want to come back. Power cycling it didn't work. I don't know how to be more persuasive with it.

  2521   Mon Jan 18 18:34:01 2010 AlbertoUpdateABSLMeasurement in progress

I started a long measurement of the PRC's transmissivity. I'm leaving the lab and I'm going to be back at about 8 tonight. Please do not disturb the interferometer. it is important that the MC and the PRC stay locked all the time.

  2522   Mon Jan 18 20:58:40 2010 AlbertoUpdateABSLMeasurement in progress

Quote:

I started a long measurement of the PRC's transmissivity. I'm leaving the lab and I'm going to be back at about 8 tonight. Please do not disturb the interferometer. it is important that the MC and the PRC stay locked all the time.

 That measurement is finished. I'm now going to start another one that will take another hour or so. I'm leaving it running for the night. If you want to work on the IFO, it should be definitely done by 11pm.

  2531   Tue Jan 19 12:54:39 2010 AlbertoUpdateABSLMeasurement in progress

A measurement will be running for the next hour. Please be careful.

  2532   Tue Jan 19 16:21:18 2010 AlbertoUpdateABSLWatchdogs not working and then fixed

This afternoon the watchdogs stopped working: they didn't trip when the suspension positions crossed the threshold values.

I rebooted c1susaux (aka c1dscl1epics0 in the 1Y5 rack), which is the computer that runs the watchdog processes.

The reboot fixed the problem.

  2534   Wed Jan 20 20:11:56 2010 AlbertoUpdateABSLSome preliminary results from measuring PRC's transmissivity for an amplitude modulated beam
Here I'm posting a plot showing a set of measurements that I made in the past few days to determine the absolute length of the PRC cavity.
As in my other AbsL measurements, I inject an auxiliary laser beam into the cavity and look at the transmission. In the PRC case, the beam is injected through the dark port and I look at a pick-off of the REFL beam. The aux laser is phase locked to the PSL beam and I control the differential frequency between the two. The PSL and the aux beam interfere and beat at their differential frequency.
 
The attached plot shows the transmitted power as a function of the beat frequency.
 
Fitting the data with the model would let me determine the cavity length. 
By now I can estimate the length of the PRC at about 2.257m, but it's still a rather approximate value.
I can't provide accurate error bars yet. I need to optimize the measurements to get a more precise value.
 
I will go more through the details of the measurement technique and of the fitting function as soon as I have more definitive results.
 
The data points shown here were taken at different times and not always in optimal alignment condition of the PRC. 
To get a good fit of the data I should have fewer frequency segments, taken in a shorter period of time, and in which the power circulating inside of the cavity (ie SPOB) fluctuates as little as possible.
 
For what regards the time needed for a measurements, I already significantly sped up the measurements (i.e. optimizing the scanning and acquisition GPIB scripts, and fixing a couple of problems with the PDH box used in the PLL), and finally now I can scan several tens of MHz in few minutes.
About the frequency segments, so far they have been determined by two factors
1) Tthe frequency generator in the PLL: the Marconi works as a continuous wave generator only in limited ranges. Switching from one to another brakes the wave in a way that causes the PLL to lose lock.
2) Getting below 18 MHz a series of other beats appear on the PLL photodiode and make the PLL lose lock.
 
For the first problem, I'm thinking of using two Marconis and to mix their signals. I would keep one at 300MHz and I would scan the other from 300MHz to 500MHz. In fat, in that frequency range the Marconi has not discontinuity.
 
To try to avoid the other beats at low frequency, I'm not entirely sure about what to do yet. 
 
To be continued...
  2541   Fri Jan 22 02:54:06 2010 AlbertoUpdateABSLOvernight measurement

I'm leaving a measurement running overnight. It should be done in about one hour.

Tomorrow morning, If you need to use the interferometer, and you don't want to have the auxiliary beam going onto the dark port, you can turn down the flipping mirror and close the NPRO's mechanical shutter.

  2543   Fri Jan 22 14:40:49 2010 AlbertoUpdateABSLOvernight measurement

Quote:

I'm leaving a measurement running overnight. It should be done in about one hour.

Tomorrow morning, If you need to use the interferometer, and you don't want to have the auxiliary beam going onto the dark port, you can turn down the flipping mirror and close the NPRO's mechanical shutter.

 This is what I measured last night:

2010-01-21_PRCtransmissivityVsModel.png

 This is not a fit. It's just a comparison of the model with the data.

  2545   Mon Jan 25 16:30:37 2010 AlbertoUpdateABSL166 MHz sideband turned off

I turned off the modulation at 166MHZ becasue I don't need it if I'm only locking the PRC.

It was introducing extra amplitude modulations of the beam which interfered with the AbsL's PLL photodiode.

I'm going to turn it back on later on.

  2546   Mon Jan 25 16:46:33 2010 AlbertoUpdateABSL166 MHz sideband turned off

Quote:

I turned off the modulation at 166MHZ becasue I don't need it if I'm only locking the PRC.

It was introducing extra amplitude modulations of the beam which interfered with the AbsL's PLL photodiode.

I'm going to turn it back on later on.

 I turned back on the 166MHz modulation just a bit. I set the slider at 4.156.

When it was totally off the MZ seemd quite unhappy.

  2550   Wed Jan 27 11:02:30 2010 AlbertoUpdateABSLPRC Cavity Length
 I fitted the data from scanning the PRC by changing the beat frequency of the auxiliary laser beam with the PSL beam.
The data points that I've taken so far over the entire frequency range (0-300 MHz) are not continuous. For several reasons the PLL was unable to maintain lock for such a large range and I had to break it into smaller segments. The measurements to acquire them stretched over a too long period of time during which the status of the PRC changed.
 
Because of that, before I get a continuous set of data points (perhaps normalized by the circulating power inside of the cavity), I restricted the fit to a 55MHz range around 100MHz. I obtained the following numbers for the fit parameters:
Length PRC = 2.169 +/- 0.007 m
Schnupp Asymmetry: 0.471+/- 0.006 m
 
The fit is shown in the attached plot:
2010-01-21_PRCtransmissivityVsFit.png
When I fit over the entire set of data I get this:
 
2010-01-21_PRCtransmissivity_EntireFreqRange_VsFit.png
 
Length PRC = 2.224 +/- 0.005 m
Schnupp Asymmetry: 0.457+/- 0.005 m
 
The results are different. Evidently I have to improve the measurement. I'm working on it.
 
For posterity:
The function I used to fit the transmitted beat power vs. frequency is the following:
 
E_trans = - t_prm * r_itm * exp(1i*2*wb*l_prc/c) .* sin(wb*l_/c) ./ ( 1 + r_prm * r_itm * exp(1i*2*wb*l_prc/c) .* cos(wb*l_/c)
 
Where wb is the angular frequency of the beat, l_prc and l_ are the length of the PRC and the Schnupp asymmetry, respectively; r_itm, t_itm, r_prm, t_prm are reflectances and transmittances of PRM and ITM; c is the speed of light.
 
  2551   Thu Jan 28 09:14:51 2010 AlbertoConfigurationComputersc1iscey, c1iscex, c1lsc, c1asc rebooted

This morning the LSC scripts wheren't running properly. I had to reboot c1iscey, c1iscex, c1lsc, c1asc .

I burtrestored to Monday January 25 at 12:00. 

  2552   Thu Jan 28 09:17:32 2010 AlbertoUpdateLSC166 Modulation turned off

I temporarily turned off the 166 modulation.

  2553   Fri Jan 29 12:06:58 2010 AlbertoUpdateABSLMeasurement running today at lunch time

I just started a measuremtn that will be running for the next hour or so. Please be careful with the interferometer.

  2554   Fri Jan 29 13:14:49 2010 AlbertoUpdateABSLMeasurement running today at lunch time

Quote:

I just started a measuremtn that will be running for the next hour or so. Please be careful with the interferometer.

Done. IFO available

ELOG V3.1.3-