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ID Date Authordown Type Category Subject
  2436   Mon Dec 21 01:14:08 2009 ranaSummaryElectronicsNoise measurement of the Rai Weiss FET preamp box

 I shorted the input to the box and then put its output into the SR560 (low noise, G = 100, AC). I put the output of the SR560 into the SR785.

*** BTW, the 2nd channel of the SR785 is kind of broken. Its too noisy by a factor of 100. Needs to go back for repair once we get started in the vac.

The attached PNG shows its input-referred noise with the short.

The picture shows the inside of the box before I did anything. The TO-5 package metal can is the meaty super dual-FET that gives this thing all of its low noise power.


In the spectra on the right are two traces. The BLUE one is the noise of the box as I found it. The BLACK one is the noise after I replaced R1, R6, R7, & R10 with metal film resistors.

The offset at the output of the box with either an open or shorted input is +265 mV.

I think we probably should also replace R2, R3, & R1, but we don't have any metal film resistors lower than 100 Ohms in the kit...but hopefully Steve will read this elog and do the right thing.

Attachment 1: IMG_0242.JPG
  2441   Mon Dec 21 19:24:29 2009 ranaUpdateASSOAF Model update and build instructions

I fit the MC1 -> MCL TF using vectfit4.m (from mDV). The wrapper file is mDV/extra/C1/ fitMC12MCL.m.

Plotted here are the data (RED), the fit (BLUE), and the residual x10 (GREEN).

For the magnitude plot, residual is defined as ------   res = 1 - fit / data

For the phase plot the residual is defined as -------    res =  phase(data)-phase(fit)

You can see that the agreement is very good. The phase match is better than 5 deg everywhere below 10 Hz.

This TF is so smooth that we could have probably done without using this, but its good to excercise the method anyway.

Attachment 1: mc12mcl.png
  2449   Wed Dec 23 17:33:14 2009 ranaUpdateASSOAF Feedaround ON and doing something good

The Rai box ran out of batteries a couple of days ago and so the data is no good. I've put the Ranger back on the SR560 for now (but with the damping resistor removed, so the gain is 2x more than before).

  2454   Sun Dec 27 23:44:59 2009 ranaUpdateElectronicsMCT QPD investigation


I found that MCT QPD has dependence of the total output on the position of the spot. Since the QPD needs the supply and bias voltages from the sum/diff amp, I could not separate the problems of the QPD iteself and the sum/diff amplifier by the investigation on Tuesday. On Wednesday, I investigated a generic quad photodiode interface module D990692.

 This is indeed sad. But, we can perhaps bypass all of this by just using the individual segment outputs. According to the circuit diagram and the c1iool0 .db file, we should be able to just do the math on the segments and ignore the VERT/HOR/SUM signals completely. In that case, we can just use high impedance for the sum/diff buffers as Koji says and not suffer from the calibration errors at all I think.

  2471   Sun Jan 3 08:23:39 2010 ranaConfigurationCDSautoburt.pl 'fixed' for post 2009 years

Tobin & Keith pointed out in the LLO ilog that there was a code bug in the autoburt.pl script for autoburts.

I edited the autoburt.pl script so that it will work from now until 2099 (by which time we may no longer be using this version of perl):

nodus:autoburt>diff autoburt.pl~ autoburt.pl
<     $thisyear = "200".$timestamp[5];
>     $thisyear = "20".$timestamp[5];

The autoburt has not been working ever since 11PM on New Year's eve.

I ran it by hand and it seems to run fine. I noticed along the way that it was running on op340m (our old Sun Blade 150 machine). The autoburt.pl was pointing at /cvs/cds/bin/perl

which is Perl v5.0. I changed it to use '/usr/bin/env' and now points at '/usr/bin/perl' which is perl 5.8. It runs fine with the new perl:

op340m:scripts>time perl /cvs/cds/scripts/autoburt.pl >> /cvs/cds/caltech/logs/autoburtlog.log
5.37u 6.29s 2:13.41 8.7%

Also ran correctly, via cron, at 9AM.

  2472   Mon Jan 4 09:52:40 2010 ranaConfigurationCamerasITMX camera and PSL channels

I fixed up the ITMX camera like we did for ITMY recently (removed T's and added strain relief - the lens was already OK).

I also updated the .SCAN field for the RMTEMP and RCTEMP channels to 0.1 second. This had been done via probe but was wiped out after reboot previously, because I forgot to update the psl.db file.

  2478   Tue Jan 5 11:00:04 2010 ranaOmnistructureEnvironmentAdded new wall cable-racks


we hung two new WALL cable racks. One is on the pillar next to the Sp table, the other is next to the PSL computer rack.

 awesome - I have ordered 5 blue racks so that we can hang power cables. The fat BLUE ones are for fat cables and the orange ones for the coax cables.

  2518   Sun Jan 17 05:22:42 2010 ranaConfigurationComputersELOG script change

With Dave Barker's help, I changed the elog startup script. Instead of running as a Daemon with the -D option,

it now runs in the background with the unix "&". I think that the stdout and stderr are now redirected to a log file called elog.log.

We can 'tail -f' this file to see what its up to and debug any future crashing.

  2524   Tue Jan 19 00:10:44 2010 ranaUpdateElectronicstriple resonant circuit for EOM

Very cool.         

  2547   Tue Jan 26 03:28:56 2010 ranaUpdateABSL166 MHz sideband turned off


 You can turn the 166 off if you want. MZ is unhappy after its turned off, but that's just the thermal transient from removing the RF heat. After a several minutes, the heat goes away and the MZ can be relocked.

One of these days we should evaluate the beam distortion we get in EOMs because of the RF heat induced dn/dT. Beam steering, beam size, etc.

  2549   Tue Jan 26 20:18:32 2010 ranaConfigurationALARMop540m: alarms and BLRMS and StripTool restored

I turned the StripTool and ALARMS and BLRMS back on on op540m. Looks like it has been rebooted 5 days ago and no one turned these back on. Also, there was a bunch of junk strewn around its keyboard which I restrained myself from throwing in the trash.

The BLRMS trends should be active now.

  2569   Thu Feb 4 00:59:52 2010 ranaUpdateelogelog restarted

 I restarted the ELOG on NODUS just now. Our attempt to set up error logging worked - it turns out ELOG was choking on the .ps file attachment.

So for the near future: NO MORE .PS files! Use PDF - move into the 20th century at least.

matlab can directly make either PNG or PDF files for you, you can also use various other conversion tools on the web.

Of course, it would be nice if nodus could handle .ps, but its a Solaris machine and I don't feel like debugging this. Eventually, we'll give him away and make the new nodus a Linux box, but that day is not today.

  2593   Thu Feb 11 19:20:44 2010 ranaUpdateComputersStatus of the IP change over

After Joe left:

  1. Turned on op440m and returned him his keyboard and mouse.
  2. Damped MC2.
  3. Opened PSL shutter - locked PMC, FSS,
  4. Started StripTool displays on op540m.
  5. op340m doesn't respond to ping from anyone.
  6. started FSS  SLOW and RCPID scripts on op540 - need to kill and restart on op430m.
  7. ASS wouldn't come up - it doesn't know who linux1 is.
  8. MC autolocker wouldn't run on op540m because of a perl module issue, started it on op440m - it needs to be killed and restarted on op430m.
  9. probably mafalda, linux2, and op430m need some attention - they are all in the same rack.

As of 7:18 PM, the MC is locked and the PSL seems normal + all suspensions are damped and the ELOG is back up as well as the SVN.

  2620   Sun Feb 21 17:44:35 2010 ranaUpdateGeneralPrep for Power Supply Stop
  • Turned on the RAID attached to linux1 (its our /cvs/cds disk)
  • Turned on linux1 (it needed a keyboard and monitor in order to be happy - no fsck required)
  • Turned on nodus (and started ELOG) + all the control room machines
  • Turned on B/W monitors
  • Untaped fridge

  • Found several things OFF which were not listed in the Wiki...
  • Turned ON the 2 big isolation transformers (next to Steve's desk and under the printer). These supply all of the CDS racks inside.
  • ~75% of the power strips were OFF in the CDS racks ?? I turned on as many as I could find (except the OMC).
  • Switched on and keyed on all of the FE and SLOW crates in no particular order. Some of the fans sound bad, but otherwise OK.
  • Turned on all of the Sorensens that are labeled.
  • Turned ON the linear supplies close to the LSC rack.
  • ON the Marconis - set them according to the labels on them (probably out-dated).
  • After restoring power to the PSL enclosure (via the Isolation Transformer under the printer) turned the Variac ON and HEPA on full speed.
  • Plugged in the PSs for the video quads. Restored the Video MUX settings - looks like we forgot to save the correct settings for this guy...


1) Turned on the chiller, then the MOPA, then the RC's Heater power supply.
2) Shutter is open, laser is lasing, PMC is locked.
3) RC temperature is slowly rising. Will probably be thermalized by tomorrow.

Sun Feb 21 20:04:17 2010
Framebuilder is not mounting its RAID frames - in fact, it doesn't mount anything because the mountall command is failing on the RAID with the frames. The Jetstor RAID is also not responding to ping. Looks like the JetStor RAID which has all of our frames is still on the old 131 network, Joe.
  2621   Mon Feb 22 07:25:58 2010 ranaUpdateGeneralPrep for Power Supply Stop

Autoburts have not been working since the network changeover last Thursday.

Last snapshot was around noon on Feb 11...  

It turns out this happened when the IP address got switched from 131.... to 192.... Here's the horrible little piece of perl code which was failing:

$command = "/usr/sbin/ifconfig -a > $temp";

   open(TEMP,$temp) || die "Cannot open file $temp\n";
   $site = "undefined";
   # this is a horrible way to determine site location                                                   
   while ($line = <TEMP>) {
     if ($line =~ /10\.1\./) {
       $site = "lho";
     } elsif ($line =~ /10\.100\./) {
       $site = "llo";
     } elsif ($line =~ /192\.168\./) {
       $site = "40m";
   if ($site eq "undefined") {
     die "Cannot Determine Which LIGO Observatory this is\n";

I've now put in the correct numbers for the 40m...and its now working as before. I also re-remembered how the autoburt works:

1) op340m has a line in its crontab to run /cvs/cds/caltech/burt/autoburt/burt.cron (I've changed this to now run at 7 minutes after the hour instead of at the start of the hour).

2) burt.cron runs /cvs/cds/scripts/autoburt.pl (it was using a perl from 1999 to run this - I've now changed it to use the perl 5.8 from 2002 which was already in the path).

3) autoburt.pl looks through every directory in 'target' and tries to do a burt of its .req file.

Oh, and it looks like Joe has fixed the bug where only op440m could ssh into op340m by editing the host.allow or host.deny file (+1 point for Joe).

But he forgot to elog it (-1 point for Joe).®

  2634   Tue Feb 23 16:42:02 2010 ranaConfigurationComputer Scripts / ProgramsSVN restarted on NODUS

I ran the start Apache script as described by Yoichi in the WIki. SVN back up.

  2645   Sun Feb 28 16:45:05 2010 ranaSummaryGeneralPower ON Recovery
  1. Turned ON the RAID above linux1.
  2. Hooked up a monitor and keyboard and then turned ON linux1.
  3. After linux1 booted, turned ON nodus - then restarted apache and elog on it using the wiki instructions.
  4. Turned on all of the control room workstatiions, tuned Pandora to Johnny Cash, started the auto package updater on Rosalba (517 packages).
  5. Started the startStrip script on op540m.
  6. turned on RAID for frames - wait for it to say 'SATA', then turn on daqctrl and then fb40m and then daqawg and then dcuepics
  7. turned on all the crates for FEs, Sorensens, Kepcos for LSC, op340m, mafalda was already on
  8. fb40m again doesn't mount the RAID again!
  9. I turned on fb40m2 and that fixes the problem. The fb40m /etc/vfstab points to, not the JetStor IP address.
  10. I plugged in the Video Switch - its power cord was disconnected.
  11. FEs still timing out saying 'no response from EPICS', but Alberto is now here.

Sun Feb 28 18:23:09 2010

Hi. This is Alberto. Its Sun Feb 28 19:23:09 2010

  1. Turned on c1dcuepics, c0daqctrl and c0daqawg. c0daqawg had a "bad"status on the daqdetail medm screen. The FEs still don't come up.
  2. Rebooted c1dcuepics and power cycled c0daqctrl and c0daqawg. The problem is still there.
  3. Turned on c1omc. Problem solved.
  4. Rebooted c1dcuepics and power cycled c0daqctrl and c0daqawg. c0daqawg now good. The FE are coming up.
  5. Plugged in the laser for ETMY's oplev
  6. Turned on the laser of ETMX's oplev from its key.

 Monday, March 1, 9:00 2010 Steve turns on PSL-REF cavity ion pump HV at 1Y1

  2646   Sun Feb 28 23:47:52 2010 ranaUpdateComputersrosalba

Since Rosalba wanted to update ~500 packages, I let it do it. This, of course, stopped the X server from running. I downloaded and installed the newest Nvidia driver and its mostly OK.

The main problem with the auto-update on our workstations is that we've updated some packages by hand; i.e. not using the standard CentOS yum. So that means that the auto-update doesn't work right. From now on, if you want to install a fancier package than what CentOS distributes, you should commit to handle the system maintenance for these workstations for the future. Its not that we can't have new programs, we just have to pay the price.


At 23:45 PST, I also started a slow triangle wave on the AOM drive amplitude. This is to see if there's a response in the FSS-FAST which might imply a coupling from intensity noise to frequency noise via absorbed power and the dn/dT effect in the coatings.

Its a 93 second period triangle modulating the RC power from 100% down to 50%.

  2649   Mon Mar 1 22:38:12 2010 ranaUpdateComputersRC sensitivity to RIN

The overnight triangle wave I ran on the AOM drive turns out to have produced no signal in the FAST feedback to the PZT.

The input power to the cavity was ~10 mW (I'm totally guessing). The peak-peak amplitude of the triangle wave was 50% of the total power.

The spectral density of the fast signal at the fundamental frequency (~7.9 mHz) is ~0.08 V/rHz. The FAST calibration is ~5 MHz/V. So, since we

see no signal, we can place an upper limit on the amount of frequency shift = (5 MHz/V) * (0.08 V/rHz) * sqrt(0.0001 Hz) = 4 kHz.

Roughly this means that the RIN -> Hz coefficient must be less than 4 kHz / 5 mW or ~ 1 Hz/uW.

For comparison, the paper on reference cavities by the Hansch group lists a coefficient of ~50 Hz/uW. However, they have a finesse of 400000

while we only have a finesse of 8000-10000. So our null result means that our RC mirrors' absorption is perhaps less than theirs. Another possibility

is that their coating design has a higher thermo-optic coefficient. This is possible, since they probably have much lower transmission mirrors. It would be

interesting to know how the DC thermo-optic coefficient scales with transmission for the standard HR coating designs.

Attachment 1: Untitled.png
  2657   Thu Mar 4 22:07:21 2010 ranaUpdate40m Upgrading11MHz PD not yet designed

Use 10 Ohms for the resistance - I have never seen a diode with 25 Ohms.

p.s. PDFs can be joined together using the joinPDF command or a few command line options of 'gs'.

  2659   Fri Mar 5 18:04:56 2010 ranaUpdateSUSused OSEMs are magnetic

The OSEM LEDs and PDs from Honeywell have always had some ferromagnetic material in them. These are the same OSEMs we had since 2000.

You must be thinking of the really old 20th century plastic OSEMs.

  2660   Sun Mar 7 07:01:21 2010 ranaUpdateWienerFilteringGuralp Huddle Test software

We need to do a new huddle test of the Guralps for the Wiener filtering paper. The last test had miserable results.

I tried to use recent data to do this, but it looks like we forgot to turn the Guralp box back on after the power outage or that they're far off center.

So instead I got data from after the previous power outage recovery.

I tried to use our usual Wiener filter method to subtract Guralp1-Z from Guralp2-Z, but that didn't work so well. It was very sensitive to the pre-weighting.

Instead I used the new .m file that Dmass wrote for subtracting the phase noise from his doubling noise MZ. That worked very well. It does all of the subtraction in the frequency domain and so doesn't have to worry about making a stable or causal filter. As you can see, it beats our weighted Wiener filter at all frequencies.


The attached plot shows the Guralp spectra (red & green), the residual using time-domain Wiener filtering (black) and the Dmass f-domain code (yellow).

As soon as Jenne brings in her beer cooler, we're ready to redo the Huddle Test.


  2661   Sun Mar 7 23:05:39 2010 ranaUpdatePEMSeismic witnesses near MC1 tank moved


Since we're going to open the MC1 tank tomorrow, I've moved the MC1 accelerometers and the Guralp over to underneath MC2 for the vent.  I'll reconnect them later.

 I've put both Guralps next to the Ranger and connected them to the breakout box. The data is now good.

I found that the Ranger was not centered and so it was stuck (someone kicked it in the last 2 weeks apparently). I recentered the mass according to the procedure in the manual. Its now moving freely.

In order to do a better huddle test, I increased the gain of the Ranger's SR560 preamp to 100 from 10 and put it on the low noise setting. I also enabled a 2x lowpass at 3 kHz for no good reason.

I couldn't find what the actual value of the gain of the Guralp breakout box is, but I assume its 10. With this assumption the calibrations are this:

Guralp: 800 V/(m/s)  *  10  (V/V)   *  16384  cts/V   =>    7.63e-9  (m/s)/count           (0.03 - 40 Hz)

Ranger:  345 V/(m/s)  * 100 (V/V)  *  16384 cts/V   =>     1.77e-9  (m/s)/count          (above 1Hz)

To account for the fact that I am not damping the Ranger with an external damping resistor, I have changed the calibration poles and zeros: in DTT we now use 2 poles @ 0 Hz and a complex pair at 1 Hz:

G = 1.77e-9

Poles = 0, 0

Zeros = 0.15 0.9887

I think that the Guralp gain is too high by a factor of 2. To really do this right, we should attach a known voltage to the input pins of the Guralp breakout and then read off the amount of counts.

Attachment 1: seis.png
  2662   Mon Mar 8 18:15:27 2010 ranaUpdatePEMStyrofoam Cooler on the Seismos

I put Jenne's cooler over the seismometers. Kiwamu put the copper foil wrapped lead brick on top of the cooler to hold it down. I also put another (unwrapped) lead brick on top of the Guralp cables outside of the cooler. Frank gave me a knife with which I cut a little escape hole in the bottom of the cooler lip for the Guralp cables to sneak out of.

Attachment 1: SeismometersHuddled.jpg
  2666   Wed Mar 10 15:02:58 2010 ranaUpdatePEMStyrofoam Cooler on the Seismos

This is the spectra and coherence from a quiet time last night. I've lowered the Guralp cal by a factor of 2 to account for the fact that the gain in the breakout box is actually 20 and not 10 as I previously said.

The AD620 stage in the front part has a gain of 10 and then there's a single-to-differential stage in the output which gives us a gain of 2. The DTT cal in counts is now 3.8e-9 (m/s)/count.

The second plot shows the Guralp and Ranger signals at the ADC input (converted from counts to Volts for usefulness). The thick grey line is the expected noise of the Guralp breakout box

(mainly the AD620) propagated to the ADC (via multiplication by 2). It looks like the preamp board should not be a problem as long as we can reach the AD620 limit.

So the excess noise in the Guralp is not the fault of the preamp, but more likely the mounting and insulation of the seismometers.

Attachment 1: Seismic-Ref_100310.png
Attachment 2: Untitled.gif
  2671   Sat Mar 13 21:30:22 2010 ranaUpdatePEMStyrofoam Cooler on the Seismos



  2672   Sat Mar 13 22:16:03 2010 ranaUpdateWienerFilteringGuralp Huddle Test software

I used some recent better data to try for better Z subtraction.

Dmass helped me understand that sqrt(1-Coherence) is a good estimate of the theoretical best noise subtraction residual. This should be added to DTT. For reference the Jan statistic is the inverse of this.

This should get better once Steve centers the Guralps. 

Attachment 1: guralpznoise.png
  2686   Fri Mar 19 21:15:33 2010 ranaUpdatePEMGuralp2 centered again

This trend of the last 200 days shows that GUR2 has been bad forever...until now anyways.

Attachment 1: Untitled.png
  2687   Fri Mar 19 23:03:41 2010 ranaUpdatePEMGuralp2 centered again

I went and double-checked and aligned the styrofoam cooler at ~5:00 UTC. It was fine, but we really need a better huddling box. Where's that granite anyway?

Here's the new Huddle Test output. This time I show the X-axis since there's some coherence now below 0.1 Hz.

You'll also notice that the Wiener filter is now beating the FD subtraction. This happened when I increased the # of taps to 8000. Looks like the noise keeps getting lower as I increase the number of taps, but this is really a kind of cheat if you think about it carefully.

Attachment 1: huddlez.png
  2689   Sun Mar 21 19:25:29 2010 ranaUpdatePEMGuralp2 centered again

From this morning, now in calibrated units, and with the Güralp self noise spec from the Güralp manual.

Attachment 1: huddlez.png
  2692   Mon Mar 22 02:03:57 2010 ranaSummaryElectronicsUPDH Box #17: Ready

It took too long to get this box ready for action. I implemented all of the changes that I made on the previous one (#1437). In addition, since this one is to be used for phase locking, I also made it have a ~flat transfer function. With the Boost ON, the TF magnitude will go up like 1/f below ~1 kHz.

The main trouble that I had was with the -12V regulator. The output noise level was ~500 nV/rHz, but there was a large oscillation at its output at ~65 kHz. This was showing up in the output noise spectrum of U1 (the first op-amp after the mixer). Since the PSRR of the OP27 is only ~40 dB at such a high frequency, it is not strange to see the power supply noise showing up (the input referred noise of the OP27 is 3.5 nV/rHz, so any PS noise above ~350 nV/rHz becomes relavent).

I was able to tame this by putting a 10 uF tantalum cap on the output of the regulator. However, when I replaced the regulator with a LM7912 from the blue box, it showed an output noise that went up like 1/f below 50 kHz !! I replaced it a couple more times with no benefit. It seems that something on the board must now be damaged. I checked another of the UPDH boxes, and it has the same high frequency oscillation but not so much excess voltage noise. I found that removing the protection diode on the output of the regulator decreased the noise by a factor of ~2. I also tried replacing all of the 1 uF caps that are around the regulator. No luck.

Both of the +12 V regulators seem fine: normal noise levels of ~200 nV/rHz and no oscillations.

Its clear that the regulator is not functioning well and my only guess is that its a layout issue on the board or else there's a busted component somewhere that I can't find. In any case, it seems to be functioning now and can be used for the phase locking and PZT response measurements.

  2719   Sun Mar 28 20:00:17 2010 ranaUpdateCamerasGigE camera no work from screen

Not that this is an urgent concern, just a data point which shows that it doesn't just not work at the sites.

Attachment 1: Untitled.png
  2720   Sun Mar 28 20:05:33 2010 ranaSummaryPSLFSS Work from Sunday: AOM/VCO level set wrong

Just before working on the FSS today, I noticed that the VCO RF output level was set incorrectly.

This should ALWAYS be set so as to give the maximum power in the first order diffracted sideband. One should set this by maximizing the out of lock FSS RFPD DC level to max.

The value was at 2.8 on the VCOMODLEVEL slider. In the attached plot (taken with the FSS input disabled) you can see that this puts us in the regime where the output power to the FSS is first order sensitive to the amplitude noise on the electrical signal to the AOM. This is an untenable situation.

For adjusting the power level to the FSS, we must always use the lamba/2 plate between the AOM and the RC steering mirrors. This dumps power out to the side via a PBS just before the periscope.

Attachment 1: Untitled.png
  2721   Sun Mar 28 20:51:31 2010 ranaSummaryPSLFSS Work from Sunday: Cavity Suspension is Ridiculously Undamped!

What is the Transfer Function of the suspension of the reference cavity? What were the design requirements? What is the Q and how well does the eddy current damping work? What did Wolfowitz know about the WMD and when? Who cooked the RTV in there and why didn't we use Viton??

To get to the bottom of these questions, today I shook the cavity and measured the response. To read out the pitch and yaw modes separately, I aligned the input beam to be misaligned to the cavity. If the beam is mis-aligned in yaw, for example, the transmitted light power becomes first order sensitive to the yaw motion of the cavity.

In the attached image (10 minute second-trend), you can see the second trends for the transmitted and relfected power. The first ringdown comes from the pitch or vertical mode. The second (shorter) one comes from the yaw misalignment and the yaw shake.

To achieve the up/down shake, I leaned onto the table and pumped it at its eigenfrequency. For the yaw shake, I put two fingers on the RC can's sweater and pushed with several pounds of force at the yaw eigenfrequency (2.6 Hz). For the vertical, I jumped up and down at half the vertical eigenfrequency (4 Hz).

I also made sure that the .SCAN field on these EPICS records were set to 9 so that there is no serious effect from a beating between the eigenfrequency and the EPICS sample rate.


f_vert   = 4 Hz

tau_vert = 90 seconds

Q_vert   = 1000            (yes, that number over there has 3 zeros)


f_hor    = 2.6 Hz

tau_hor  = 30 seconds

Q_hor    = 250


This is an absurd and probably makes us very sensitive to seismic noise - let's make sure to open up the can and put some real rubber in there to damp it. My guess is that these high Q modes

are just the modes of the last-stage steel spring / pendulum.

Attachment 1: Untitled.png
  2722   Sun Mar 28 23:17:46 2010 ranaSummaryPSLFSS Work from Sunday: noise spec

This is the error point spectrum - it is filled with huge multiples of ~75 kHz as Yoichi noticed a couple years ago.

I tried to use the netgpib.py package to read out the Agilent 4395, but the SVN had been corrupted by someone saving over the netgpib.py package. To get it to work on rosalba I reverted to the previous version, but whoever is busy hacking on netgpib.py needs to checkin the original package and work on some test code instead.

I also noticed that the default output format for the AG4395.py file is in units of Watts. This is kind of dumb - we need someone to develop this package a little as Yoichi did for the SRS785.

Attachment 1: in2.png
  2723   Sun Mar 28 23:47:47 2010 ranaSummaryPSLFSS Work from Sunday: Open Loop Gain

I measured the open loop gain of the FSS (as usual, I have multiplied the whole OLG by 10dB to account for the forward loop gain in the box). I used a source level of -20 dBm and made sure this was not saturating by changing the level.

Its clear that the BW is limited by the resonance at ~1.7 MHz. Does anyone know what that is?

Attachment 1: fssloop.png
Attachment 2: sweep2.png
  2724   Mon Mar 29 01:11:33 2010 ranaSummaryPSLFSS Work from Sunday: RF Out Spectrum

I measured the RF spectrum coming out the FSS RFPD to look for saturations - its close to the hairy edge. This is with the 8x power increase from my AOM drive increase. I will increase the FSS's modulation frequency which will lower the Q and gain of the PD to compensate somewhat. The lower Q will also gain us phase margin in the FSS loooop.


I put in a bi-directional 20 dB coupler (its only rated down to 30 MHz, but its only off by ~0.3 dB at 21 MHz) between the RFPD and the FSS box. I looked at the time series on the 300 MHz scope and measured the power spectrum.

The peak signal on the scope was 40 mV; that translates to 400 mV at the RFPD output. Depending on whether the series resistor in the box is 20 or 50 Ohms, it means the MAX4107 is close to saturating.

As you can see from the spectrum, its mostly likely to hit its slew rate limit (500 V/us) first. Actually its not going to hit the limit: but even getting within a factor of 10 is bad news in terms of distortion.

Besides the multiples of the modulation frequency, you can see that most of the RMS comes from the strange large peaks at 137.9 and 181.1 MHz. Anyone know what these are from?


On the middle plot above, I have enabled the 20 MHz BW limit so you can see how much the amplitude goes down when only the 21.5 MHz SB is included. You can also see from the leftmost plot that once in awhile there is some 400mV/10ns slewing. Its within a factor of 10 of the slew rate limit.

Attachment 1: rfout.png
  2733   Tue Mar 30 06:37:32 2010 ranaConfigurationPSLReference Cavity PD Noise Spectrum

Some more words about the RFAM: I noticed that there was an excess RFAM by unlocking the RC and just looking at the RF out with the 50 Ohm input of the scope. It was ~100 mVp-p! In the end our method to minimize the AM was not so sensible - we aligned the waveplate before the EOM so as to minimize the p-pol light transmitted by the PBS cube just ahead of the AOM. At first, this did not minimize the RFAM. But after I got angry at the bad plastic mounting of the EOM and re-aligned it, the AM seemed to be small with the polarization aligned to the cube. It was too small to measure on the scope and on the spectrum analyzer, the peak was hopping around by ~10-20 dB on a few second timescale. Further reduction would require some kind of active temperature stabilization of the EOM housing (maybe a good SURF project!).

For the EOM mount we (meaning Steve) should replace the lame 2-post system that's in there with one of the mounts of the type that is used in the Mach-Zucker EOMs. I think we have spare in the cabinet next to one of the arms.

After the RFAM monkeying, I aligned the beam to the RC using the standard, 2-mirror, beam-walking approach. You can see from the attached plot that the transmission went up by ~20% ! And the reflection went down by ~30%. I doubt that I have developed any new alignment technique beyond what Yoichi and I already did last time. Most likely there was some beam shape corruption in the EOM, or the RFAM was causing us to lock far off the fringe. Now the reflected beam from the reference cavity is a nice donut shape and we could even make it better by doing some mode matching! This finally solves the eternal mystery of the bad REFL beam (or at least sweeps it under the rug).

At the end, I also fixed the alignment of the RFPD. It should be set so the incident angle of the beam is ~20-40 deg, but it was instead set to be near normal incidence ?! Its also on flimsy plastic legs. Steve, can you please replace this with the new brass ones?

Attachment 1: rc.png
  2741   Wed Mar 31 12:30:31 2010 ranaUpdateGreen Lockingfrequency counter for green PLL

Its a good measurement - you should adjust the input range of the 620 using the front panel 'scale' buttons to see how the noise compares to Matt's circuit when the range is reduced to 1 MHz. In any case, we would use it in the 350 MHz range mode. What about the noise of the frequency discriminator from MITEQ?

  2750   Thu Apr 1 12:07:22 2010 ranaUpdateGeneralPZT response for the innolight

The Lightwave NPRO should be around 5 MHz/V. 

The Innolight PZT coefficient is ~1.1 MHz/V.

(both are from some Rick Savage LHO elog entries)

  2751   Thu Apr 1 15:21:12 2010 ranaUpdateGreen Lockingfrequency counter for green PLL


  2759   Sat Apr 3 11:35:47 2010 ranaConfigurationPSLReference Cavity PD Noise Spectrum

The units on this plot are completely bogus - we know that the thermal noise from the resonant part of the circuit is just V = sqrt(4*k*T*Z) ~ 3nV/rHz. Then the gain of the MAX4107 stage is 10. The output resistor is 50 Ohms, which forms a divide by 2 with the input impedance of the spectrum analyzer and so the bump in the dark noise should only be 15 nV/rHz and not microVolts.


[Rana, Alberto]

This evening we measured the noise spectrum of the reference cavity PD used in the FSS loop. From that we estimated the transimpedance and found that the PD is shot-noise limited. We also found a big AM oscillation in correspondence of the FSS modulation sideband which we later attenuated at least in part.

This plot shows the spectrum noise from the RF output of the photodetector.

  2764   Mon Apr 5 01:02:07 2010 ranaUpdatePEMGuralp interface box turned off

I was checking into the Guralp situation today. I put the rubber balls underneath the granite block (the Q is too high), but found unfortunately that Jenne's styrofoam box is too short to cover the Guralps on top of the granite. If the box was skinny enough to fit on the block or taller by ~6 inches, it would be perfect. We need some new Seismo boxes.


Here's the story of the Gur2 noise so far. We need to pull out and repair the breakout box.

1) At some point we noticed that the Guralp2 X channel was behaving badly.

2) Steve tried recentering with just a +12V supply - this didn't work. Jenne then centered it using the +/- 12V supply. This was OK.

3) Around noon on March 24, the channel 'goes bad' again.

4) On the afternoon of the 25th, most of the channels go to zero, but the GUR2X channel stays bad. There's NO ENTRY in the elog about this. This is UNACCEPTABLE. Apparently, the seismometers were disconnected without shutting off the power to the box. You MUST elog everything - otherwise, go home and sit on your hands.

5) On the evening of the 31st, Steve turns off the Guralp breakout box. From the trend, you can see that the signals all go to zero at that time.

6) From then until today, there is no noise in the GUR2X channel. From these tests we can guess that the problem is in the GUR2X channel of the breakout box, but not in the AA Chassis or the ADC, since those showed no excess noise with the box turned OFF. Its hard to be sure without elog entries, but I assume that 3/25-3/31 was a 'seismometer disconnected', but 'box on' state.

Attachment 1: Untitled.png
  2805   Mon Apr 19 05:54:50 2010 ranaConfigurationPSLRC Temperature Servo Turned OFF temporarily

In order to measure the transfer function of the RC cavity's foam, I've turned off the servo so that the room temperature noise can excite it.

The attached plot shows a step response test from 2 weeks ago. Servo is nominally still working fine.

Attachment 1: Untitled.png
  2806   Mon Apr 19 07:38:07 2010 ranaHowToElectronicsRepair and Calibration of SR560: s/n 59650

Frank noticed that this particular SR560 had an offset on the output which was unzeroable by the usual method of tuning the trim pot accessible through the front panel.

I tried to zero the offset using the trimpots inside, but it became clear that the offset was due to a damaged FET, so Steve ordered ~20 of the (now obsolete*) NPD5564.

I replaced this part and adjusted the offsets and balanced the CMRR of the differential inputs mostly according to the manual (p. 17). There are a few notes that should be added to the procedure:

  1. It can sometimes be that the gain proscribed by the manual is too high and saturates the output for large offsets. If that's the case, simply lower the gain, trim the offset, then return the gain to the specified value and trim again.
  2. The limit in trimming the offset is the stick slip resolution in the trim pot. This can potentially leave the whole preamp in an acoustically sensitive state. I tapped the pots with a screwdriver after tuning to make sure it was in more of a 'sticky' rather than 'slippy' region of the knob. A better design would allow for more filtering of the pot.
  3. In the CMRR tuning procedure it says to 'null sine wave output' but it should really say 'null the sine wave component at the drive frequency'. The best CMRR tuning uses a 1 kHz drive and leaves a residual 2 kHz signal due to the distortion imbalance (of the FETs I think).
  4. The CMRR tuning upsets the DC offset trim and vice versa. The best tuning is gotten by iterating slightly (go back and forth once or twice between the offset and CMRR tuning procedures).

It looks like its working fine now. Steve's ordering some IF3602 (low-noise, balanced FET pair from Interfet) to see if we can drop the SR560's input noise to the sub-nV level.

Noise measured with the input terminated with a BNC short (not 50 Ohms) G=100, DC coupled, low-noise mode:

Input referred noise (nV/rHz)
f e_n


1 44
10 8
100 5
1000 5
10000 4
  2829   Wed Apr 21 22:11:48 2010 ranaUpdatePSLInnolight 2W Vertical Beam Profile

Back in Gainesville in 1997, I learned how to do this using the chopper wheel. We had to make the assumption that the wheel's blade was moving horizontally during the time of the chop.

One advantage is that the repetitive slices reduces the random errors by a lot - you can trigger the scope and average. Another advantage is that you can download the average scope trace using USB, floppy, or ethernet instead of pencil and paper.

But, I never analyzed it in enough detail to see if there was some kind of nasty systematic error.

  2839   Sun Apr 25 02:56:07 2010 ranaUpdateLSCStarted dev of LSC FE

LSC Plant Model. That is all.

  2865   Sun May 2 15:38:12 2010 ranaSummarySUSCoil Actuator Balancing and Spot Position


Oh, but it gets even better: in order to trust the A2L script in this regard you have to know that the coil driver - coil - magnet gain is the same for each channel. Which you can't.

But we have these handy f2pRatio scripts that Vuk and Dan Busby worked on. They use the optical levers to balance the actuators at high frequency so that the A2L gives you a true spot readout.

But wait! We have 4 coils and the optical lever only gives us 2 signal readouts...

  2869   Mon May 3 01:16:50 2010 ranaHowToElectronicsMarconi phase noise measurement setup

 To try the 3-corner hat method on the Marconis, I started to set up the measurement into the DAQ system.

I have set the bottom 2 in the PSL rack to 11.1 MHz. I use a ZP-3MH level 13 mixer as the phase detector. The top one is the LO, it has an output of +13 dBm.

The bottom one is the test unit, it has an output of +6 dBm (should be close to the right level - the IP3 point is +9 dBm). The top one has external DC FM modulation enabled with a FM dev range of 10 Hz.

Mixer output goes through a 50 Ohm in-line termination and then a BLP-5 low pass filter (Steve, please order ~7 of the BLP-1.5 or BLP-1.9 low pass filter from Mini-Circuits) and then into

the DC coupled of a SR560. After some gain and filtering that feedback goes back to the FM input of the top-Marconi to close the PLL. I adjusted the gain to be as small as possible and still stay locked and not

saturate the ADC.

The input to the SR560 is Tee'd into another SR560 with AC coupled input, G = 1000, low-noise. Its output is going directly to the ADC channel - C1:IOO-MC_DRUM1.

I calibrated the channel by opening the loop and setting the AC coupled gain to 1. This lets the Marconis beat at several Hz. The peak-peak signal is equivalent to pi radians.


As usual, I was befuddled by the FM input. For some reason I always forget that since its a straight FM input, we don't need any filtering to get a plain 1/f loop. The attached plot shows how we get bad gain peaking if you forget this and use a 0.03 Hz pole in the SR560.

The grey trace is the ADC signal with everything hooked up, but the RF input set to zero (via setting Carrier = OFF in the bottom Marconi). It is the measurement noise.

The BLUE trace is very close to the true phase noise beat of the two Marconis with a calibration error of ~5%. I have not corrected for the loop gain: its right now around a 1 Hz UGF and 1/f. Next, I will measure the loop and compensate for it in the DTT calibration.

Then I'll measure the relative phase noise of 3 of the signal generators to get the individual noises.

Bottom line is that the sensitivity of this approach is good and we should do this rather that use spectrum analyzers since its easy to get very long averages and high res spectra. To get 5x better sensitivity, we can just use the Rai-FET box instead of a SR560 for the readout, but just have to contend with its batteries. Also should try using BALUNs on the RF and LO signals to get rid of the ground loops.

Attachment 1: pn.png
  2873   Mon May 3 17:49:41 2010 ranaConfigurationPSLRC Temperature Servo Turned OFF temporarily


In order to measure the transfer function of the RC cavity's foam, I've turned off the servo so that the room temperature noise can excite it.

The attached plot shows a step response test from 2 weeks ago. Servo is nominally still working fine.

 I've just now re-enabled the temperature control of the reference cavity can. Trend of the last 8 days is attached.

Attachment 1: rct.png
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