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ID Date Author Typeup Category Subject
  1530   Tue Apr 28 17:51:13 2009 robHowToLockingsetting the RF CARM demod phase


To set the demod phase for RF CARM, sensed at REFL2 (REFL 166I), it suffices to set the demod phase for REFL2 to be the optimal phase for controlling SRCL in a no-arm state.


For POX33, the ideal phase for single arm locking does not yield a zero-offset CARM signal.  So the offset needs to be manipulated digitally. 

Attachment 1: XARM_phases_POX.pdf
XARM_phases_POX.pdf XARM_phases_POX.pdf XARM_phases_POX.pdf XARM_phases_POX.pdf
Attachment 2: CARM_phases_POX.pdf
CARM_phases_POX.pdf CARM_phases_POX.pdf CARM_phases_POX.pdf CARM_phases_POX.pdf
  1532   Wed Apr 29 10:20:14 2009 steveHowToVACcryo pump interlock rule is waved


I tested the cryopump interlock today. It is touchy. I do not have full confidence in it.

I'm proposing that VC1 gate valve should be kept closed while nobody is working in the 40m lab.

How to open gate valve:

1, confirm temp of 12K on the gauge at the  bottom of the cryopump

2, if medm screen cryo reads OFF( meaning warm) hit reset will result reading ON (meaning cold 12K )

3, open VC1 gate valve if P1 is not higher than 20 mTorr


VC1 was closed at 18:25,

IFO condition: not pumped,

expected leak plus  out gassing should be less than 5 mTorr/day

The RGA is in bg-mode, annuloses are closed off

 The Cryo pump is running reliably since April 22 hence there is no need to close VC1 repeatedly.

The photo switch interlock was put back onto the H2 vapor pressure gauge and it is working.

  1550   Wed May 6 02:39:20 2009 YoichiHowToLockingHow to go to DC readout
I wrote a script called DC_readout, which you can find in /cvs/cds/caltech/scripts/DRFPMI/bang/nospring/.

Currently, the locking script succeeds 1/3 of the time. The freaky parts are the MC_F hand off and REFL_DC hand off.
MC_F hand off succeeds 70% of the time. REFL_DC goes well about a half of the time. Combined, the success rate is about 1/3.
We need some work on those hand offs.
Once you pass those freaky parts, the cm_step script usually goes smoothly and you will reach the full RF lock with the boost and the super boost1 engaged on the CM board.

To go to DC readout from there, run the DC_readout script.
First, this script will put some offset to the DARM loop so that some carrier light will leak to the AS port.
You are prompted to lock the OMC. Move the OMC length offset slider to find the carrier resonance and lock the OMC.
You have to make sure that it is carrier, not the 166MHz sideband. Usually the carrier light pulsates around 10Hz or so whereas the 166MHz SB is stable.
Once you locked the OMC to the carrier, hit enter on the terminal running the DC_readout script.
The script will do the rest of the hand off.
Once the script has finished, you may want to check darm_offset_dc in the C1LSC_LA_SET screen. This value sets the DC offset (a.k.a. the homodyne phase).
You may want to change it to what you want.
  1589   Fri May 15 14:05:14 2009 DmassHowToComputersHow To: Crash the Elog

The Elog started crashing last night. It turns out I was the culprit, and whenever I tried to upload a certain 500kb .png picture, it would die. It has happened both when choosing "upload" of a picture, and when choosing "submit" after successfully uploading a picture. Both culprits were ~500kb .png files.

  1657   Fri Jun 5 16:45:28 2009 rob, peteHowToComputerstdsavg failure in cm_step script



the command

tdsavg 5 C1:LSC-PD4_DC_IN1

was causing grievous woe in the cm_step script.  It turned out to fail intermittently at the command line, as did other LSC channels.  (But non-LSC channels seem to be OK.)  So we power cycled c1lsc (we couldn't ssh).

Then we noticed that computers were out of sync again (several timing fields said 16383 in the C0DAQ_RFMNETWORK screen).  We restarted c1iscey, c1iscex, c1lsc, c1susvme1, and c1susvme2.  The timing fields went back to 0.  But the tdsavg command still  intermittently said "ERROR: LDAQ - SendRequest - bad NDS status: 13".

The channel C1:LSC-SRM_OUT16 seems to work with tdsavg every time.

Let us know if you know how to fix this. 


 Did you try restarting the framebuilder?


What you type is in bold:

op440m> telnet fb40m 8087

daqd> shutdown


Restarting the framebuilder didn't work, but the problem now appears to be fixed.

Upon reflection, we also decided to try killing all open DTT and Dataviewer windows.  This also involved liberal use of ps -ef to seek out and destroy all diag's, dc3's, framer4's, etc.


That may have worked, but it happened simultaneously to killing the tpman process on fb40m, so we can't be sure which is the actual solution.


To restart the testpoint manager:

what you type is in bold:

rosalba> ssh fb40m

fb40m~> pkill tpman

The tpman is actually immortal, like Voldemort or the Kurgan or the Cylons in the new BG.  Truly slaying it requires special magic, so the pkill tpman command has the effect of restarting it.


In the future, we should make it a matter of policy to close DTTs and Dataviewers when we're done using them, and killing any unattended ones that we encounter.


  1701   Thu Jun 25 10:28:58 2009 steveHowToVACCryopump is regenerated
The Cryopump's VC1 valve to IFO was closed yesterday.
The compressor  Helium pressure was 235 PSI. The cold head temp on H2 vapor pressure gauge was reading ~14 Kelvin,
The compressor and piston driver were turned off to let cold head warm up to room temp.
The flow path from Cryo to TP3 were checked to insure that only VC2 and V5 would be open for pumping.
VC2 valve was opened to TP3 through V5
Now as the Cryo was warming up while TP3 drag turbo pump was pumping away the accumulated ice, that was melting and vaporizing.
This is shown on one day the plot below.
To check outgassing rate of the Cryo pump after one day of pumping V5 was closed for 20 minutes.
The accumulation was 1.3 mTorr in 20 min
This means the Cryo is clean, it is ready to be started up in the future.
VC2 was closed to seal this condition.
The flow path between VC2, VM3, V7, V6 , VA6 and manual needle valve  would be pumped for one day through V5 to TP3 to clean up 
Attachment 1: Creg.jpg
  1799   Mon Jul 27 19:55:19 2009 KojiHowToIOOLens selection: plano-convex? or bi-convex?

Q. When should we use plano-convex lenses, and when should we use bi-convex?

As I had the same question from Jenne and Dmass in a month,
I just like to introduce a good summary about it.
Lens selection guide (Newport)

At a first order, they have the same function.
Abberation (= non-ideal behavior of the lens) is the matter.

  1898   Thu Aug 13 11:20:43 2009 janoschHowToPEMthree-channel self-noise estimation

There are two new Matlab files on the svn in /mDV/extra/C1. 'mycsd.m' is to calculate the cross-spectral density between two channels, 'csd_40T_40T_SS1.m' calls this function with the available seismic channels and derives a self-noise spectrum for the vertical axis using all three seismometers. The method requires that there are no correlations between two instruments only which is a bad idealization for certain frequencies if you have seismometers of totally different types.

'mycsd.m' uses the high-gain, low-resolution Nuttall window (built-in Matlab function 'nuttallwin.m'). High-gain windows are used for broad-band spectra like seismic spectra, but it should be exchanged by another window if you plan to look at small-bandwidth features like peaks.

Since the three-channel analysis does not require knowledge of response functions, it could be used to evaluate the performance of the adaptive filter. For example, if three channels responding to the same signal are available, then the ratio of any two csds corresponds to one of the relative transfer functions. You can then compare this function with the result produced by the adaptive filter.

  1906   Fri Aug 14 15:32:50 2009 YoichiHowToComputersnodus boot procedure
The restart procedures for the various processes running on nodus are explained here:


Please go through those steps when you reboot nodus, or notice it rebooted then elog it.
I did these this time.
  1910   Sat Aug 15 10:36:02 2009 AlanHowToComputersnodus boot procedure

The restart procedures for the various processes running on nodus are explained here:


Please go through those steps when you reboot nodus, or notice it rebooted then elog it.
I did these this time.

fb40m was also rebooted. I restarted the ssh-agent for backup of minute-trend and /cvs/cds.
  1931   Thu Aug 20 09:16:32 2009 steveHowToPhotosControl Room Workstation desks lowered to human height


There were no injuries...Now we need to get some new chairs.

 The control room desk tops heights on the east side were lowered by 127 mm


Attachment 1: P1040788.png
Attachment 2: P1040782.png
Attachment 3: P1040786.png
Attachment 4: P1040789.png
Attachment 5: P1040785.png
  1937   Mon Aug 24 16:48:57 2009 steveHowToVACnew UPS installed


As Rob noted last Friday, the UPS which powers the Vacuum rack failed. When we were trying to move the plugs around to debug it, it made a sizzling sound and a pop. Bad smells came out of it.

Ben came over this week and measured the quiescent power consumption. The low power draw level was 11.9 A and during the reboot its 12.2 A. He measured this by ??? (Rob inserts method here).

So what we want is a 120 V * 12.2 A  ~ 1.4 kVA UPS with ~30-50% margin. We look for this on the APC-UPS site:

On Monday, we will order the SUA2200 from APC. It should last for ~25 minutes during an outage. Its $1300. The next step down is $200 cheaper and gives 10 minutes less uptime.

The new APC Smart -UPS 2200VA is now running at  the vacuum rack. There are 2 load monitoring leds on out of 5

Maglev, dry pumps and roughing pumps are not using UPS.

The switch over went smoothly with Yoichi's help.

First we closed all vacuum valves and stopped the two small turbos.

Than turned power off to instruments in the vac-rack and VME: c1vac1 & c1vac2

Maglev was left running.

Now we moved the AC plugs from the wall receptacles over to the back of the UPS and powered them up.

Varian turbos were restarted and vacuum valves were restored in order to reach  vacuum normal condition.

See 40m Vacuum System States and Sequences Manual of 10-24-2001


Linux 3 desk top computer is out of order at the pump spool. We should replace it.

The vacuum control screen can be pulled up on a lap top: /cvs/cds/caltech/medm/c0/ve/VacControl_BAK.adj


  1998   Thu Sep 24 19:35:20 2009 ranaHowToPhotos40m Google account

I've created a 40m Google account. Please post all the 40m related photos to this site. If you don't already have it, download Picasa to make this easier.

40m Installation Photos">

the password is in the usual password place.

  2062   Wed Oct 7 06:26:09 2009 ranaHowToIOOMC_L calibration + some DTT lore

I drove MC2 in POS and used the resulting response in MC_F to calibrate the IOO-MC_L channel.

Yoichi did an excellent job of calibrating MC_F last year. I have used his calibration of MC_F (220 Hz/count @ DC) to get the MC_L calibration at DC as well as at high frequencies. The hardware dewhitening was OFF for all these measurements.


1. For the DC measurement I excited C1:SUS-MC2_MCL_EXC at 0.0731 Hz. At these frequencies, the MC_L path has much more gain than the MC_F path. So this excitation at the error point makes the length path to drive itself to cancel the digital excitation. Since the overall MC servo gain is huge, this causes the MC_F path to compensate the residual MC_L motion. One can simply take the ratio of MC_L/MC_F to get the calibration of MC_L in Hz.

2. For the AC measurement, I engaged FM9 of the MC2_MCL filter bank. This guy is an elliptic LP with a notch at 660.38 Hz. I then drove MC2_LSC at 660.38 Hz with a sine wave of 500 counts amplitude. The notch makes the gain of the MC_L feedback zero at that frequency. So MC_F has to do all the work. We can simply measure the ratio of MC2_LSC/MC_F to get the AC calibration of MC2_MCL_OUT (aka IOO-MC_L) and MC2_LSC_OUT (aka LSC-MC_L).



MCF/MCL @ 0.0731 Hz = 569.4. So the MC_L calibration at DC is 220 x 569.4 = 125 kHz/count or 6.02 nm/count.

From this we would expect the AC calibration to be (6 nm/count)*(660.38/f_pend)^2 = 13.0 x10^-15 m/count.

The AC measurement gave 1445 counts_peak** of MC_F for the 500 counts (peak) excitation in MC2_LSC. From Yoichi's entry we get that the high frequency calibration of MC_F should be 0.089 Hz/count. So the MC_L calibration at 660 Hz is 0.089*1445/500 = 0.25 Hz / count or 12.3 x 10^-15 m/count. So the AC/DC ratio is close to 1.

Splitting the difference, the new official MC_L calibration is 5.87 nm/counts @ DC with a complex pole pair at 0.972 Hz.


** note:  To convert from the peak height observed in DTT with a 50% Overlap Hanning window you must use the following intuitive formula:  counts_peak = (counts / rHz) * sqrt(2 * BW). In this case, BW is the number that DTT reports as BW on the screen, NOT the BW that you asked for on the measurement tab.

*** note: when measuring peak heights in a DTT FFT, make sure to unclick the box for 'Bin' under the config tab. Bin suppresses peaks in a plot with a lot of points and is ON by default.

**** note: I have updated the MCF reference in the Templates directory with the Yoichi calibration - spectrum attached. This is probably the most accurate MCF spectrum we have ever put in the elog in the history of the 40m. The implication is that the VCO phase noise is ~5 mHz/rHz. Not bad.

***** note: with the OAF off, I drove a 1.55 Hz sine wave into MC1 and measured the ratio of MC1_MCL_OUT/IOO-MC_L. This gives the DC calibration of MC1_MCL_OUT = 7.98 nm/count.

Attachment 1: mcl-cal.png
Attachment 2: a.png
  2091   Wed Oct 14 15:48:26 2009 MottHowToGeneralPhase Noise measurement

I have gotten the hang of the procedure for measuring phase noise on the AOMs. 

Koji suggested I right up a short guide (wiki page?) on how to do this. 

I will finish up here, then go measure the AOMs at the other lab (may have to be tomorrow, after laser safety), and then write up the instructions.

  2115   Mon Oct 19 11:00:52 2009 steveHowToSAFETY40m safety training

Kiwamu, Alex and Zach are practicing mandatory IR-safety scan at the 40m-PSL

40m specific safety indoctrination were completed.

Attachment 1: safety_10_2009.JPG
  2164   Fri Oct 30 09:24:45 2009 steveHowToMOPAhow to squeeze more out of little


Here is the plots for the powers. MC TRANS is still rising.

What I noticed was that C1:PSL-FSS_PCDRIVE nolonger hit the yellow alert.
The mean reduced from 0.4 to 0.3. This is good, at least for now.

 Koji did a nice job increasing light power with some joggling.

Attachment 1: 44to34.jpg
  2242   Wed Nov 11 18:43:57 2009 rana, kojiHowToPhotosIlluminated Paintbrush Technique


1/4" exposure, standard room lights                                                                              3" exposure, slowly moving LED bar light from ~60 cm distance

Because of the light behind, the focus was attracted by the far objects...
Evenso the magnet ball looks better in the right picture.

The technique is as follows:
Use longer exposure time, move the LED bar illumination through the area like painting the light everywhere.
It is supposed to provide a picture with more uniform light and the diminished shadow.


  2403   Sat Dec 12 07:36:56 2009 ranaHowToElectronicsHow to Measure the Length of a Cable: Interferometry

Need to measure the length of the cable, but too lazy to use a measuring tape?

Then you too can become an expert cable length measurer by just using an RF signal generator and a scope:

  1. Disconnect or short (not 50 Ohm term) the far side of the cable.
  2. Put a T on the near side of the cable.
  3. Drive the input of the T with your signal source.
  4. Look at the output of the T with the scope while sweeping the signal source's frequency knob.

The T is kind of acting like a beamsplitter in an asymmetric length Michelson in this case. Just as we can use the RF phase shift between the arms to measure the Schnupp asymmetry, we can also use a T to measure the cable length. The speed of light in the cable is documented in the cable catalog, but in most cases its just 66% of the speed of light in the vacuum.

  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.

  2429   Thu Dec 17 19:03:14 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.

 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.

  2540   Thu Jan 21 17:23:30 2010 josephb,alex,kojiHowToComputersRCG code fixes

In order to see the Contec DO-32L-PE Digital output PCIe card with the new controls, we had to add the CDO32 part to the CDS_PARTS.mdl file in control /cds/advLigo/src/epics/simLink/ directory on megatron, as well as create the actual model mdl file (based on cdsDio.mdl) in the control/cds/advLigo/src/epics/simLink/lib directory. 

The CDO32.pm file (in /home/controls/cds/advLigo/src/epics/util/lib) has existed for some time, it was just missing the associated pieces in simlink.  However, Alex also checked out a newer version Dio.pm in the process.  As we are not using this part at this time, it should be fine.

The code now compiles and sees the digital output card.

You need a special care on this block as it turned out that the code does not compiled if the "constant" block is connected to the input. You must use appropriate block such as bitwise operator, as shown below.

Attachment 1: CDO32.png
  2559   Tue Feb 2 13:14:09 2010 KojiHowToIOOAnatomy of New Focus Resonant EOM

Joe let me use the resonant EOM for GigE phase camera for a while.
Then, I immediately started to open it :)

it uses the MiniCIrcuits T5-1T transformer and a TOKO RCL variable inductor.

The photos are on the Picasa 40m album.


  2598   Fri Feb 12 14:19:28 2010 rana, steveHowToloreInternational Fax

Steve showed me how to send an international fax today:

  1. Load paper.
  2. Dial:   011 - (country code) - number
  3. Press START (either the black or color option)
  4. wait for the screaming fax noise
  5. Done


  2729   Mon Mar 29 15:26:47 2010 MottHowToComputersNew script for controlling the AG4395A

I just put a script in the /cvs/cds/caltech/scripts/general/netgpibdata/ directory to control the network analyzer called AG4395A_Run.py .   A section has been added to the wiki with the other GPIB script sections (http://lhocds.ligo-wa.caltech.edu:8000/40m/netgpib_package#AG4395A_Run.py)

  2734   Tue Mar 30 11:16:05 2010 josephbHowToComputersezca update information (CDS SVN)

I'd like to try installing an updated multi-threaded ezca extension later this week, allowing for 64-bit builds of GDS ezca tools, provided by Keith Thorne.  The code can be found in the LDAS CVS under gds, as well as in CDS subversion repository, located at 


Its under gds/epics/ in that repository.  The directions are fairly simple:

1) to install ezca with mult-threading in an existing EPICS installation
-copy ezca_2010mt.tar.gz (EPICS_DIR)/extensions/src
-cd (EPICS_DIR)/extensions/src
-tar -C -xzf ezca_2010mt
-modify (EPICS_DIR)/extensions/Makefile to point 'ezca' at 'ezca_2010mt'
-cd ezca_2010mt
-set EPICS_HOST_ARCH appropriately



  2738   Wed Mar 31 03:45:49 2010 MottHowToComputersNew script for controlling the AG4395A


I took data for the 2 NPRO PLL using the script I wrote for the AG4395, but it is very noisy above about 1 MHz.  I assume this is something to do with the script (since I am fairly confident we don't have 600 dB response in the PZT), so I will go in tomorrow to more carefully understand what is going on, I may need to include a bit more latency in the script to allow the NA to settle a bit more.  I am attaching the spectrum just to show the incredibly high noise level, 

Attachment 1: noisy_spec.png
  2778   Wed Apr 7 09:00:01 2010 steveHowToPEMprepare to open chamber

In order to minimize the diffusion of more dust particles into the vented IFO vacuum envelope

BEFORE opening chamber:

-Have a  known plan,

-Heavy 1" thick door requires 3 persons- of  one experienced and one certified crane operator and steel tow safety shoes

-Block IFO beams, be ware of experimental set up of other hazards: 1064,  visible or new-special installation

- Look at the particle counter, do not open above 6,000 particles of 0.5 micron. Construction activities are winding down. See  plot of 35 days since we  vented.

-Have clean door stand for heavy door, covered with merostate at the right location and dry-clean screws for light covers,

-Prepare lint free wipers for o-rings,(no solvent on o-ring!) Kimwipes for outside of chamber and metal covers, methanol and powder free gloves

-Wipe with wet Kimwipe-tissue of methanol around the door, chamber of interest and o-ring cover ring

-Cut door covering merostate and tape it into position,..if in place...check  folded-merostate position, if dusty... replace it

-Is your cleanroom garment clean?.......if in doubt ....replace it

-Keep surrounding area free and clean

-Make sure that HEPAs are running: PSL-enclosure, two mobile units and south end flow banch

-Check the tools: are they really clean? wipe it with wet Kimwipe, do you see anything on the Kimwipe?


-You are responsible to close chamber ASAP with light door or doors as you finished for the day.

Merostate cover down is appropriate during daily brakes.

Attachment 1: 0.5micron.jpg
  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
  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
  2879   Tue May 4 18:40:27 2010 ranaHowToElectronicsMarconi phase noise measurement setup

To check the UGF, I increased the gain of the PLL by 10 and looked at how much the error point got suppressed. The green trace apparently has a UGF of ~50 Hz and so the BLUE nominal one has ~5 Hz.

The second attachment shows the noise now corrected for the loop gain. IF the two signal generators are equally noisy, then you can divide the purple spectrum by sqrt(2) to get the noise of a single source.

The .xml file is saved as /users/rana/dtt/MarconiPhaseNoise_100504.xml

Attachment 1: Untitled.png
Attachment 2: ifrnoise.png
  2906   Mon May 10 19:29:33 2010 AlbertoHowToElectronicsNew Focus 1811 PD calibrated against New Focus 1611 PD
I measured the output impedance of the New Focus 1611 PD (the 1GHz one) and it is 50 Ohm for both the DC and the AC output. It turns out that the transimpedance values listed on the datasheet are the following:
T1611_dc = 1e4 V/A (1MOhm referred)
T1611_ac = 700 V/A (50 Ohm)
The listed transimpedances for the 1811 PD (the 125 MHz PD) are the following:
T_dc = 1e3 V/A (??)
T1811_ac = 4e4 V/A (50 Ohm)
I measured the output impedances of the 1811 and they are: 50 Ohm for the AC output, ~10 Ohm for the DC output.
It's not clear which input impedance the DC transimpedance should be intended referred to.
So I measured the transimpedance of the 1811 using the 1611 as a (trusted) reference. It turns out that for the AC transimpedance to match the listed value, the DC transimpedance has to be the following:
T1811_dc = 1.7e3 V/A (1MOhm)
  2913   Tue May 11 18:58:49 2010 ranaHowToElectronicsMarconi phase noise measurement setup

Just a little while ago, at 2330 UTC on 5/11, I swapped the phase noise setup to use another Marconi - this time its the 3rd one from the top beating with the 4th one from the top (2nd from the bottom).

After a little while, I swapped over to beat the 33 w/ the 199. I now have all the measurements. For the measurement of the last pair, I inserted BALUN 1:1 transformers on the outputs of both signal generators'.

This last pair appears to be the quietest of the 3 and also has less lines. The lines are mainly at high frequency and are harmonics of 120 Hz. Probably from the Sorensen switching supplies in the adjacent rack.

I double checked that the 10 MHz sync cable was NOT plugged in to any of these during this and that the front panel menu was set to use the internal frequency standard. In the closed loop case, the beat frequency between the 33/199 pair changes by less than ~0.01 Hz over minutes (as measured by calibrating the control signal).


Attachment 1: Untitled.png
  2914   Wed May 12 02:21:56 2010 ranaHowToElectronicsMarconi phase noise measurement setup

Finally got the 3-cornered-hat measurement of the IFRs done. The result is attached.

s12, s23, & s31, are the beat signals between the 3 signal generators.

s1, s2, & s3 are the phase noise of the individual generators made by the following matlab calculation:

%% Do the hat
s1 = sqrt((s12.^2  + s31.^2 - s23.^2) / 2);
s2 = sqrt((s12.^2  + s23.^2 - s31.^2) / 2);
s3 = sqrt((s31.^2  + s23.^2 - s12.^2) / 2);

As you can see, there is now an estimate of the individual noises. We can do better by doing some fitting of the residuals.

The real test will be to replace the noise one here with the good Wenzel oscillator and see how well we can estimate its noise. If the 11 MHz crystals don't show up, I can just try this with the 21.5 MHz one for the PSL.

Attachment 1: pn.png
  2951   Wed May 19 14:36:46 2010 AidanHowToPhase CameraPhase Camera algorithm and stuff

 I had a think about the algorithm we might use for the phase camera measurement. MATLAB has an fft function that will allow us to extract the data that we need with a single command.

We record a series of images from a camera and put them into a 3D array or movie, image_arr, where the array parameters are [x-position, y-position, time], i.e. a 2D slice is a single frame from the camera. Then we can do an FFT on that object with the syntax, f3D = fft(image_arr, [ ], 3), which only does the FFT on the temporal components. The resulting object is a 3D array where each 2D slice is an 2D array of amplitude and phase information across the image for a single temporal frequency of the movie.

So if we recorded a movie for 1s where the sample rate is 58Hz, then the 1st frame of f3D is just a DC image of the movie, the 2nd frame are the complex 1Hz components of the movie, etc all the way up to 29Hz. 

Suppose then that we have a image, part of which is being modulated, e.g. a chopper wheel rotating at 20 or 24Hz, or a laser beam profile which contains a 1kHz beat between a sideband and a reference beam. All we have to do is sample at at least twice that modulation frequency, run the command in MATLAB, and then we immediately get an image which contains the phase and magnitude information that we're interested in (in the appropriate 2D slice o the FFT).

As an example, I recorded 58 frames of data from a camera, sampling at 58Hz, which was looking at a spinning chopper wheel. There was a white sheet of paper behind the wheel which was illuminated from behind by a flashlight. The outer ring was chopping at 24Hz and the inner ring was chopping at 20Hz. I stuck all the images into the 3D array in MATLAB, did the transformation and picked out the DC, 20Hz and 24Hz signals. The results are shown in the attached PDFs which are:

  1. phase_camera_DC_comp.pdf - a single image from the camera and the DC component (zoomed in) of the FFT
  2. phase_camera_F1_comp.pdf - the magnitude and phase information of the 20Hz component of the FFT
  3. phase_camera_F2_comp.pdf - the magnitude and phase information of the 24Hz component of the FFT (this PDF contains a typo that says 25Hz).
  4. load_raw_data.m - the MATLAB routine that loads the saved data from the camera and does the FFT

You can, and I have, run the MATLAB engine from C directly. This will allow you to transfer the data from the camera to MATLAB directly in memory, rather than via the disk, but it does need proper memory allocation to avoid segmentation faults - that was too frustrating for me in the short term. In this case, the 58 frames were recorded to a file as a contiguous block of data which I then loaded into MATLAB, so it was slower than it might've otherwise been. Also the computer I was running this on was a bit of a clunker so it took a bit of time to do the FFT.

The data rate from the camera was 58fps x (1024 x 1024) pixels per frame x 2 bytes per pixel = 116MB per second. If we were to use this technique in a LIGO phase camera, where we want to measure a modulation which is around 1kHz, then we'd need a sample rate of at least 2kHz, so we're looking at at least a 30x reduction in the resolution. This is okay though - the original phase camera had only ~4000 spatial samples. So we could use, for instance, the Dalsa Falcon VGA300 HG which can give 2000 frames per second when the region of interest is limited to 64 pixels high.

Attachment 1: phase_camera_DC_comp.pdf
Attachment 2: phase_camera_F1_comp.pdf
Attachment 3: phase_camera_F2_comp.pdf
Attachment 4: load_raw_data.m
% load a raw data file into MATLAB

fid = fopen('phase_camera_data.dat');
n1 = 750;
A3D = ones(n1, n1, 58);

for jj = 1:58
    A = fread(fid, [1024, 1024], 'uint16');
    A3D(:,:,jj) = A((512-floor(n1/2)):(512-floor(n1/2))+n1-1, ...
... 64 more lines ...
  2955   Thu May 20 10:06:56 2010 AidanHowToPhase CameraPhase Camera- raw data video


  2982   Tue May 25 16:32:26 2010 kiwamuHowToElectronicsfront ends are back

 [Alex, Joe, Kiwamu]

Eventually all the front end computers came back !! 

There were two problems.

(1): C0DCU1 didn't want to come back to the network. After we did several things it turned the ADC board for C0DCU1 didn't work correctly.

(2): C1PEM1 and C0DAQAWG were cross-talking via the back panel of the crate.

(what we did)

* installed a VME crate with single back panel to 1Y6 and mounted C1PEM1 and C0DAQAWG on it. However it turned out this configuration was bad because the two CPUs could cross-talk via the back panel.

* removed the VME crate and then installed another VME crate which has two back panels so that we can electrically separate C1PEM1 and C0DAQAWG.  After this work, C0DAQAWG started working successfully.

 * rebooted all the front ends, fb40m and c1dcuepics.

 * reset the RFM bypath. But these things didn't bring C0DCU1 back.

 * telnet to C0DCU1 and ran "./startup.cmd" manually. In fact "./startup.cmd" should automatically be called when it boots.

 * saw the error messages from "./startup.cmd" and found it failed when initialization of the ADC board. It saids "Init Failure !! could not find ICS"

*  went to 1Y7 rack and checked the ADC. We found C0DCU1 had two ADC boards, one of two was not in used.

* disconnected all two ADCs and put back one which had not been in used. At the same time we changed the switching address of this ADC to have the same address as the other ADC. 

* powered off/on 1Y7 rack. Finally C0DCU1 got back.

* burtrestored the epics to the last Friday, May 21st 6:07am

  3000   Thu May 27 10:30:32 2010 kiwamuHowToGreen LockingPSL setup for green locking

 I leave notes about a plan for the green locking especially on the PSL table.



 (1) open the door  of the MC13 tank to make the PSL beam go into the MC.  Lock it and then optimize the alignment of the MC mirror so that we can later align the incident beam from the PSL by using the MC as a reference.   

 (2) Remove a steering mirror located just after the PMC on the PSL table. Don't take its mount, just take only the optic in order not to change the alignment .

 (3) Put an 80% partial reflector on that mount to pick off ~200mW for the doubling . One can find the reflector on my desk.

 (4) Put some steering mirrors to guide the transmitted beam through the reflector to the doubling crystal. Any beam path is fine if it does not disturb any other setups. The position of the oven+crystal should not be changed so much, I mean the current position looks good.

 (5) Match the mode to the crystal by putting some lenses. The optimum conversion efficiency can be achieved with beam waist of w0~50um (as explained on #2735). 

 (6) Align the oven by using the kinematic mount. It takes a while. The position of the waist should be 6.7 mm away from the center of the crystal (as explained on #2850). The temperature controller for the oven can be found in one of the plastic box for the green stuff. After the alignment, a green beam will show up.

(8) Find the optimum temperature which gives the best conversion efficiency and measure the efficiency.

(7)  Align the axis of the PSL beam to the MC by steering the two mirrors attached on the periscope.

  3017   Sun May 30 17:51:04 2010 kiwamuHowToPEMAllegra dataviewer

I found the dataviewer didn't work only on Allegra. This thing sometimes happened as described in the past entry.

I rebooted Allegra, then the problem was fixed.


  3070   Fri Jun 11 22:09:58 2010 valeraHowToCDSfoton

 It appears that foton does not like the unstable poles, which we need to model the transfer functions.

But one can try to load the filters into the front end by generating the filter file e.g.:

### DARM_ASDC                                                                   ###
### ####
DARM_ASDC  0 21 6  0  0 darm 1014223594.005454063416 -1.95554205062071  0.94952075557861 0.06176931505784 -0.93823068494216
                         -2.05077577179611   1.05077843532639  -2.05854170261687  1.05854477394411
                         -1.85353637553024   0.86042048250739  -1.99996540107622  0.99996542454814 
                         -1.93464836371852   0.94008893626414  -1.89722830906561  0.90024221050918
                         -2.04422931770060   1.04652211283968  -2.01120153956052  1.01152717233685 
                         -1.99996545575365   0.99996548582538  -1.99996545573320  0.99996548582538




Unfortunately if you open and later save this file with foton it will strip the lhp poles.

  3085   Fri Jun 18 13:42:52 2010 KojiHowToGeneralUpdate your work

All SURFs (and all others as always) are supposed to post the update of your status on the elog.

In fact, I already heard that Sharmila had been working on the serial connection to TC-200 and made some results. All of us like to hear the story.

  3114   Thu Jun 24 11:16:32 2010 Sharmila, Rana and KiwamuHowToVACInspection of the BS (sorry, no sounds)
  3118   Fri Jun 25 01:28:33 2010 DmassHowToSVNSVN woes

I am trying to get an actual complete install of the 40m svn on my machine. It keeps stopping at the same point:

I do a

svn checkout --username svn40m https://nodus.ligo.caltech.edu:30889/svn /Users/dmass/svn

A blah blah blah many files


A    /Users/dmass/svn/trunk/medm/c1/lsc/C1LSC_ComMode.adl.28oct06
svn: In directory '/Users/dmass/svn/trunk/medm/c1/lsc'
svn: Can't copy '/Users/dmass/svn/trunk/medm/c1/lsc/.svn/tmp/text-base/C1LSC_MENU.adl.svn-base' to '/Users/dmass/svn/trunk/medm/c1/lsc/.svn/tmp/C1LSC_MENU.adl.tmp.tmp': No such file or directory

I believe I have always had this error come up when trying to do a full svn install. Any illumination is welcome.



  3123   Sat Jun 26 05:02:04 2010 ranaHowToSVNSVN woes


I am trying to get an actual complete install of the 40m svn on my machine. It keeps stopping at the same point:

 I have always seen this when checking out the 40m medm SVN on a non-Linux box. I don't know what it is, but Yoichi and I investigated it at some point and couldn't reproduce it on CentOS. I think its some weirdness in the permissions of tmp files. It can probably be fixed by doing some clever checkin from the control room.

Even worse is that it looks like the whole 'SVN' mantra has been violated in the medm directory by the 'newCDS' team. It could be that Joe has decided to make the 40m a part of the official CDS SVN, which is OK, but will take some retraining on our part.

  3193   Mon Jul 12 11:20:56 2010 Gopal HowToCOMSOL TipsIntrusions (Negative Extrusions)

For the sake of future users, I have decided to periodically add tips and tricks in using COMSOL that I have figured out, most probably after hours of circuitous efforts. They will always be listed under the new COMSOL Tips category.

Today's topic: Intrusions

COMSOL has a very user-friendly interface for taking objects from 2D to 3D using the "extrusion" feature. But suppose one wants to design an object which contains screw holes or some other indentation. I've found that creating "punctures" in COMSOL is either impossible or very complicated.

Instead, COMSOL encourages users to always "add" to the object. In other words, one must form the lowest level first, then build layers sequentially on top using new work plane and boolean difference operators. This will probably be a bit clearer with an example:

1) First, create the planar projection in a work plane:


2) Extrude the first layer only in the regular fashion:


 3) Add a new work plane which is offset in the z-direction to the deepest point of the intrusion.


 4) Now, create the shape of the intrusion in this new work plane.


5) Use the Boolean "Difference" to let COMSOL know that, on this plane, the object has a hole.


 6) Extrude once more from the second work plane to complete the intrusion.


  3194   Mon Jul 12 12:16:50 2010 DmassHowToCOMSOL TipsIntrusions (Negative Extrusions)

 An entry on the 40m wiki page might serve you better, and be easier to sift through once all is said and done

  3233   Thu Jul 15 23:51:47 2010 Mr. MaricHowToSUSLevitate me if you can

You guys must work harder.


  3291   Mon Jul 26 11:15:23 2010 GopalHowToCOMSOL TipsPictures from Transfer Function Tutorial on the Wiki

The attached pictures give a brief overview of my transfer function measurement procedure in COMSOL. For more details, please see the Wiki.








  3296   Tue Jul 27 11:24:53 2010 josephbHowToComputer Scripts / Programskilldataviewer script

I placed a script for killing all instances of the dataviewer program on the current computer in /cvs/cds/caltech/scripts/general/.  Its called killdataviewer.  This is intended to get rid of a bunch of zombie dataviewer processes quickly.  These processes get into this bad state when the dataviewer program is closed in any way other than the graphical menu File -> Exit option.

Its contents are very simple:


kill `ps -ef | grep dataviewer | grep -v grep | grep -v killdataviewer | awk '{print $2}'`

  3336   Fri Jul 30 17:54:55 2010 steveHowToVACHow to stop and start slow pumpdown


Bob and Steve closed BS chamber with the help of the manual Genie lift and the pump down started. The PSL shutter was closed and manual block was placed in the beam path. High voltage power supplies were checked to be off.

Pumping speed ~ 1 Torr/min was achieved at  1/8 of a turn opened roughing valve RV1

 We are at 370 Torr at 9 hrs of  pumping. RV1 is opened to ~ 3/8 turn orifice. We are using one roughing pump RP3  and butterfly valve is in place.


How to stop: 1, close RV1 by torque wheel  2, close V3 from MEDM screen  3, turn off RP3 roughing from MEDM screen  4, disconnect metal hose to oily pump

after butterfly valve. This KF-45 O-ring seal should be kept clean 5, place/close  45 mm cover blanks at the end of the hose and and on the 5" nipple.


How to start: 1, remove blanks from  hose and nipple 2, reconnect roughing pump hose to RV1 nipple  3, turn on PR3  4, open V3  5, open RV1 by wrench to ~3/8

6, fine tune RV1 opening to 1 Torr/min


ESSENTIAL: one operator has to be present when oilly roughing pump is connected to the vac. envelope

ELOG V3.1.3-