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ID Date Author Typeup Category Subject
  536   Tue Jun 17 22:00:53 2008 JohnHowToPSLProblems turning MZ servo on/off
We were unable to toggle the MZ servo on/off (Blank/Normal) from MEDM. Pushing on the Xycom board and cables changed the fault from constant to intermittent. At least one lock loss has been caused by a MZ glitch.
  551   Sun Jun 22 21:38:49 2008 robHowToGeneralIFO CONFIGURE

Now that we're getting back into locking, it's nice to have a stable alignment of the interferometer.
Thus, after you're done with your experiment using subsets of the interferometer (such as a single arm),

please use the IFO_CONFIGURE screen, and click "Restore last Auto-Alignment" in the yellow "Full IFO" section.

If you don't know what this means/how to do this, you shouldn't be using the interferometer on your own.
  615   Tue Jul 1 14:24:58 2008 robHowToComputer Scripts / Programsconlog time machine

I've written a perl script (now in the $SCRIPTS/general directory) which implements a "conlog restore" command, restoring channels matching a regexp to a given time using the conlog records and the EpicsTools.pm perl module. The script is called time_machine_conlog:



time_machine_conlog restores EPICS control settings using a conlog time
usage: time_machine_conlog [<--dryrun>] <date=yyyy/mm/dd,hh:mm:ss> <timezone> <regexp>

Can also accept a gps time, in which case timezone=gps.
Use the option <--dryrun> to see conlog output without restoring any settings.

EXAMPLE: time_machine_conlog 2008/05/30,12:00:00 PDT "C1:SUS-MC.*_(PIT|YAW)_COMM"

It sometimes returns an error message even when the command is successful--this is because conlog stores EPICS settings to an absurd level of precision, but ezcawrite will not write EPICS values to this level (or at least won't indicate if it did). I consider this a bug in ezcawrite so I'm not touching it.

The script is untested with regards to switch settings (such as ENABLE/DISABLE). It's mainly intended for numerical values.
  617   Tue Jul 1 21:27:27 2008 robHowToComputer Scripts / Programsslider twiddling after reboot

Sometimes after we reboot the front-end machines, some of the hardware gets stuck in an unknown state. We generally fix this by twiddling EPICS settings, which refresh the hardware somehow and put it into a known state. I've started a script (slider_twiddle) which we can just run after reboots to do this for us. Right now it just has the QPD whitening gain settings. As we find more stuff, we can add to it. It's in $SCRIPTS/Admin/.
  636   Sun Jul 6 16:17:40 2008 tobinHowToComputersSVN
I was able to check out the 40m SVN here in Livingston using this command:

svn co svn+ssh://controls@nodus.ligo.caltech.edu/cvs/cds/caltech/svn/trunk/medm

As you might guess, this uses ssh in place of the web server (which we don't have yet).
  639   Mon Jul 7 13:49:27 2008 YoichiHowToPSLMZ offset, gain tips
John, Yoichi

This morning John found that MZ servo is not working.
We were able to bring the MZ back by changing the output offset a bit. But we were not sure what was actually wrong.
So we pulled out the MZ board and checked several TPs to understand the behavior.
Here is the summary of what we learned this morning.

The MZ control board has the following stages:

[Mixer] -(error signal)-> [Sum amp for input offset] -(error + offset)-> [Variable Gain Amp] -> [Filter (x100 DC gain)] -(FB signal)-> [High Voltage Amp] -> output
(The HV amp also works as the sum amp for the output offset)

(1) We noticed that the Sum amp for the input offset has an output of -0.14V even when the offset input is 0V. This can be canceled by the input offset slider.
So for the moment, it is fine. But we might want to change the op-amp because the weird offset implies there might be something wrong with the chip.
The procedure to null the -0.14V offset is the following:
a) Enable Test 1 input on the MZ MEDM screen.
b) Move the input offset slider until the mixer monitor becomes 0V. Currently the input offset slider is at -7.5V to cancel the -0.14V offset.

(2) Because the gain of the Variable Gain Amp and the Filter combined is large, the Filter can be easily saturated if the output offset is not right.
This was the cause of the MZ problem this morning. The output offset slider was at a wrong position making the error signal slightly off centered from zero.
This residual DC error signal was amplified by the large gain chain and saturated the filter amp.
Our experience is that the output offset cannot go below -3V. We set it at 0V for now.
  654   Thu Jul 10 13:47:12 2008 YoichiHowToComputerssvn access via https
Now you can access to the svn repository on nodus by https.
To perform a checkout, you can use the following command

svn co --username svn40m https://nodus.ligo.caltech.edu:30889/svn/trunk/chans

This will check out "chans" directory.
The password for svn40m is written in the usual place.
You can also access the URL by a web browser to see the repository in a very primitive way.
A nice web interface for browsing the repository is planed but not yet implemented.
  788   Mon Aug 4 00:56:07 2008 KojiHowToGeneralAbs. Len. Meas. ~ Auto freq scanner with GPIB
Work log on August 3rd - Part1

o Yesterday I was too much tired of changing the RF frequency, reading peaks on the RF spectrum, and writing the values. Rana saw me and thought I was such poor that he gave me an USB-GPIB adapter.

o I dig into the internet for the manuals of the adapter, IFR2023A(Marconi), and HP8591E(RF spectrum analyzer) in order to learn how to use them.

o I had LabVIEW installed on my laptop. Finally I understand how to use that adapter (by Agilent) with LabVIEW. I made a small program to scan the frequency of IFR2023A, and read the peak values from HP8591E. It is unfortunate that there is no LabVIEW in the 40m lab. I think I can make an independent executable which does not need the LabVIEW itself. Give me some time to understand how to do it.
Attachment 1: freq_scan.png
  833   Thu Aug 14 10:26:45 2008 steveHowToSUSsus cable pin cheater for out of vac damping
The 40m D25 vacuum feed troughs give you a mirror image pin count.

Sus damping outside of the vacuum envelope require this cheater cable where
on the male D pin 1 is connected to female D 13 and so on
and male D pin 14 is connected to female D 25 and so on
Attachment 1: suscabmin.png
  867   Thu Aug 21 17:55:14 2008 ranaHowToIOOMC WFS DC Offsets
I ran the McWFS_dc_offsets script to trim out the DC offsets on the MC WFS DC signals.

Rob says "who cares?"
  875   Mon Aug 25 10:23:53 2008 steveHowToGeneralcable killer
Rack 1Y7 double violation:

BNC cables left to be jammed by door

and see destroyed BNCs

RED fibers should be rerouted.
I placed protective obstacle in position
so the door can not be closed.

Please do not do this!

DNA analysis is in progress on your finger prints.
Attachment 1: cablkill.png
Attachment 2: cablkll2.png
  882   Mon Aug 25 17:45:34 2008 rana, josephb, robHowToPEMAccelerometer range
Joe shows us by jumping up ~15" in the control rom that the accelerometers are set with not enough gain.

Since this is taken around 5:30 in the evening, so we can take the nearby time series to represent what a
high noise level is. I recommend we up the gain using the ICS-110B .ini file.
Attachment 1: Screenshot-4.png
  889   Tue Aug 26 19:07:37 2008 YoichiHowToComputersReading data from Agilent 4395A analyzer through GPIB from *Linux* machine
I succeeded in reading data from Agilent 4395A analyzer, who's floppy is crappy, through GPIB from a Linux machine using
agilent 82357B USB-GPIB interface.
I installed the linux GPIB driver to one of the lab. laptops (the silver DELL one currently sitting on the 4395A analyzer).
I wrote an initialization script for the USB-GPIB interface and a small python script for reading data from the analyzer.


1. Connect the USB-GPIB interface to the laptop and the analyzer.
2. Run /usr/local/bin/initGPIB command (it takes about 10sec to complete).
3. Run /usr/local/bin/getgpibdata.py > data.txt to save data from the analyzer to a text file.

The data format is explained in the comments of getgpibdata.py
This method is way faster than the unreliable floppy. The data is transfered in a few sec.

I'm now writing a wiki page on this

I will install the same thing into the other DELL laptop soon.
Let me know if you have trouble with this.
  890   Wed Aug 27 10:55:35 2008 YoichiHowToComputersAnnoying behavior of the touch pads of the lab. laptops is fixed
I was sick of the stupid touch pad behavior of the lab. laptops, i.e. firefox goes back and forth in the history when the cursor is moved.
It was caused by firefox mis-interpreting the horizontal scroll signal as back/forward command.
I stopped it by going to about:config in firefox and set mousewheel.horizscroll.withnokey.action to 0 and
mousewheel.horizscroll.withnokey.sysnumlines to true.
  904   Fri Aug 29 18:24:48 2008 ranaHowToPSLPMC: PZT Calibration
I calibrated the PMC PZT at DC by using 'trianglewave' to drive the DC offset slider
and reading back PMC_PZT and PMC_TRANSPD_F (both are DC coupled DAQ channels).

The attached PDF illustrates the method: look at the voltage required to span 1 FSR and then divide.
PMC_cal (m/V) = (1064 nm)/2 / V_FSR
The calibration for our PZT is therefore 10.4 nm/V.
The full scale (0-300 V) range is 3.1 microns.

From Jenne's elog entry we know that the series resistor to the PZT is 63.6 kOhms. The PZT is labeled as
having a capacitance of 279 nF. So the PMC drive's pole frequency is 1/2/pi/63.6e3/279e-9 = 9 Hz +/- 0.5 Hz.
The cable capacitance is ~20 pF/foot so its not significant for this.

The template file is Templates/PMC-PZTcal.xml.

Using the above calibrations, also plot the calibrated PMC ERR and PZT spectra.
Attachment 1: pmc-pzt-cal.pdf
Attachment 2: mcf.png
  966   Thu Sep 18 18:38:14 2008 YoichiHowToComputersHow to compile an SNL code for VxWorks
Dave Barker guided me through how to compile an SNL code into a Motorola 162 CPU object.

Here is the procedure:

(1) You need an account at LHO and a password for ops account at LHO. Contact Dave if you don't have these.

(2) Copy your code (say Particle.st) to the LHO gateway machine.
scp Particle.st username@lhocds.ligo-wa.caltech.edu:/cvs/cds/lho/target/t0sandbox0
(3) Login to lhocds.ligo-wa.caltech.edu
ssh username@lhocds.ligo-wa.caltech.edu
(4) Login to control0
ssh ops@control0
(5) Change directory to the sandbox dir.
cd /cvs/cds/lho/target/t0sandbox0
(6) Prepare for the compilation
setup epics
(7) Edit makefile in the directory. You have to modify a few lines at the end of the file.
There are comments for how to do it in the file.

(8) Compile
make Particle.o
(9) Copy the object file to the 40m target directory
scp Particle.o controls@nodus.ligo.caltech.edu:/cvs/cds/caltech/target/c1psl/

That is it.
  977   Mon Sep 22 16:51:27 2008 YoichiHowToComputersNetwork GPIB
I was able to make the wireless connected GPIB interface work with SR785.
Now you can download data from SR785 through network, wherever it is located.
Say good bye to floppy disks.

I wrote an installation note in the wiki.

I wrote a new script called "netgpibdata.py" which works similarly as "getgpibdata.py".
It is in the 40m svn. Instructions on how to use it is on the above mentioned wiki page.
  983   Tue Sep 23 00:47:24 2008 YoichiHowToComputersNetwork GPIB


I wrote a new script called "netgpibdata.py" which works similarly as "getgpibdata.py".
It is in the 40m svn. Instructions on how to use it is on the above mentioned wiki page.

netgpibdata.py is now installed on the controls machines (/cvs/cds/caltech/scripts/general/netgpibdata/netgpibdata.py).
You can use it like,
netgpibdata.py -i -d AG4395A -a 10 -f spectrum01

In this example, data from Agilent 4395A analyzer at GPIB address 10 connected to the GPIB-LAN box with the IP address
is downloaded and saved to spectrum01.dat. The measurement parameters are saved to spectrum01.par.
  1125   Mon Nov 10 11:06:09 2008 robHowToIOOmode cleaner locked

I found the mode cleaner unlocked, with (at least) MC1 badly mis-aligned. After checking the coil alignment biases and finding everything there looking copasetic, I checked the trends of SUS{PIT,YAW,POS} and found that both MC1 and MC3 took a step this morning. The problem turned out to be loosed/jiggled cables at the satellite amplifiers for these suspensions. Giving them a good hard push to seat them restored the alignment and the mode cleaner locked right up.
  1132   Thu Nov 13 11:33:25 2008 AlbertoHowToTreasureMaking (good) Matlab figures
Just a little summary of some useful ways to change plot settings in Matlab that I wanted to share and remember for the future:

  1139   Mon Nov 17 11:01:15 2008 AlbertoHowToElectronicsCalibrating the Frequency Standard of the Marconi
I locked the SRS Rubidium Frequency Standard FS275 to the the 1pps from the GPS. The specs from the manual provide a frequency accuracy of 5x10^-11, that is 5x10-4 @ 10 MHz, since this is the reference signal frequency we're are going to use.
The Marconi internal frequency standard is provided by a TCXO oscillator. The instrument can be set in either one of these ways: 1) Indirect Synchronization, by which the internal TCXO is phase-locked to the external frequency standard (i.e. the SRS FS275 in our case) 2) Direct Sync, in which the internal TCXO is bypassed and the frequency standard is the external one.

I checked the specs of both frequency standards and found:

SRS FS275: 5x10^-11 -> 5x10^-10 Hz @ 10 MHz

Marconi: here what the data sheet says is that "the temperature coefficient is 7 in 10^7 in the temperature range between 0 and 55 C" and so should be also the frequency accuracy.

The SRS FS275 seems more accurate than the TCXO therefore I'm going to set the Marconi on the direct external mode.
Attachment 1: 2023ASeriesOperatingManual.pdf
2023ASeriesOperatingManual.pdf 2023ASeriesOperatingManual.pdf 2023ASeriesOperatingManual.pdf 2023ASeriesOperatingManual.pdf
Attachment 2: SRS_FS275_Rubidium_Frequency_Standard.pdf
SRS_FS275_Rubidium_Frequency_Standard.pdf SRS_FS275_Rubidium_Frequency_Standard.pdf
  1150   Fri Nov 21 16:03:50 2008 ranaHowToGeneralRecharging Batteries
I found some black & red "Ninja" alkaline AA batteries in the battery charger. This is dangerous. Please
do not put alkaline batteries in there, only Nimh. If you need help with the battery charger you can
come and talk to me or Rob and we can help you out getting started.
  1181   Fri Dec 5 20:40:38 2008 YoichiHowToComputersElog multi-keyword search
The current Elog search allows you to look for only one keyword in the text.
You cannot search for two keywords by simply separating them with a white space.
That is, a search term "abc def" matches a literal "abc def", not a text containing "abc" and "def".
This is extremely annoying. However, there are still some ways to search for multiple keywords.
The Elog search fields are treated as regular expressions.
In order to match a text containing "abc" and "def", you can use a search term "abc.*def".
A period (.) means "any character", and an asterisk (*) means "any number of repetition of the preceding character".
Therefore, ".*" matches "any number of any character" i.e. anything.
The search term "abc.*def" works fine when you know "abc" appears first in the text you are looking for.
If you don't know the order of appearance of the keywords, you have two choices: either to use,
The vertical bar (|) means "or". Parentheses are used for grouping.
The first example does exactly what you want. However, you have to list all the permutations of your keywords
separated by |. If you have more than two keywords, it can be a very very long search word.
(The length of the search word is O(n!), where n is the number of keywords).
In the second example, the length of the keyword is O(n). However, it can also match a text containing two "abc".
This means the search result may contain some garbages (entries containing only "abc").
I guess in most cases we can tolerate this.

To automatically construct a multiple keyword search term for the Elog, I wrote a bash script called elogkeywd
and it is installed in the control room machines.
You can type
elogkeywd keyword1 keyword2 keyword3
to generate a regular expression for searching a text containing "keyword1", "keyword2" and "keyword3".
The generated expression is of the second type shown above. You can then copy-and-paste the result to
the Elog search field.
The script takes any number of keywords. However, there seems to be a limit on the number of characters you can type
into the search field of the Elog. I found the practical limit is about 3 keywords.
  1226   Wed Jan 14 09:22:43 2009 steveHowToVACN2 supply pressure lowered for vac valves

I've been replacing the N2 bottles recently.
I noticed that the consumption is too high. I had to replace them every two days.
Normally the interval is three or more days.
I suspect there is some leak in the line.

Strangely, it is always the left hand bottle which goes empty. The right hand bottle has been
there for more than a week at about 1000 psi.

We should check it when Steve is back.

All vac valves operated by N2
The two cylinders are located in entry room 103
There is an auto switch over valve between them to insure continuous supply.
The pressure regulator should be set 70 PSI on the gauge
This pressure we keep constant.
All vac valves will close in case of running out of N2 or losing ac power so
it is essential that one replaces empty N2 cylinder.

Simply disconnect large CGA580 fitting with a crescent wrench.
Swap in full cylinder from outside, reconnect fitting tightly and open cylinder valve.
Now you should be reading the full cylinder pressure.
Write each cylinder pressure and date-time on the board so one can see if there is a leak
Attachment 1: n280d.jpg
  1238   Mon Jan 19 15:10:37 2009 YoichiHowToComputersloadLIGOData a GUI for mDV
I installed loadLIGOData, a product of my weekend project, in /cvs/cds/caltech/apps/loadLIGOData.
This is a Matlab GUI for getting data from nds servers. It uses a modified version of mDV to retrieve data.
You can choose and download LIGO data into Matlab quickly.
I also wrote a GUI to plot the downloaded data easily.
With this GUI, you can plot multiple channel data in a single figure, which is useful to identify the cause for a lock loss etc.
You can change the time axis labels to UTC or Local time in stead of GPS second.

You can run it by typing loadLIGOData in a terminal of a linux machine.
A brief explanation of how to use it is written here:

At this moment, data from test points cannot be retrieved properly (of course there is no way to go back to the past for test points.
But still we should be able to get data in real time.). I'll try to find a solution.
Attachment 1: loadLIGOData.png
Attachment 2: plotLigoData.png
  1247   Thu Jan 22 23:36:50 2009 peteHowTooplevsarm cavity oplev calibration
calibrated the y-arm oplevs. the procedure is contained in a matlab script. the whereabouts of this script will be revealed in a future log entry.

ITMYpit 140 microrad/ct
ITMYyaw 98 microrad/ct
ETMYpit 400 microrad/ct
ETMYyaw 440 microrad/ct (previous measurement gave 420 microrad/ct)


1) Start with a single arm aligned and locked. Dither the mirror tilt in a DOF. Measure arm cavity power and oplev error signal. See the first attached plot.

2) Fit the plot to a gaussian and determine mu and sigma.

3) For a spherical ETM optic, the power in the cavity P(a), as a function of translational beam axis displacement a=R*sin(theta), is proportional to exp[-a^2/(2*x^2)] where x is the waist size (D. Anderson APPLIED OPTICS, Vol. 23, No. 17, 1984). The power as a function of mirror tilt in cts, P(tilt) is proportional to exp[-(tilt-mu)^2 /(2*sigma^2)]. So if R is the mirror radius then theta = arcsin(a/R) = arcsin[(1/R)*(tilt-mu)*x/sigma)].

4) Fit theta versus mirror tilt to get the calibration. See the second attached plot.

5) For a flat ITM optic, mirror tilt causes an angular displacement of the beam. The math for this case is given in Anderson.
Attachment 1: ETMYpitpower.png
Attachment 2: ETMYpitcal.png
  1342   Thu Feb 26 20:09:32 2009 YoichiHowToComputersSR785 python scripts now produce plots
I updated the python scripts to remotely perform measurements with an SR785.
Now these scripts can plot the results immediately using python's matplotlib capability. The sample plots can be seen in my previous elog entry.
In addition to the transfer function (TFSR785.py) and spectrum measurement (SPSR785.py) scripts, I also wrote a script for time series measurements (TSSR785.py).
This is useful when you want to check the signal level flowing in the channels before determining the excitation amplitude.
TSSR785.py will measure and show the time series and histogram of the signal measured by the SR785.
More detailed usage is explained in this wiki page:
  1464   Thu Apr 9 20:56:12 2009 YoichiHowToGeneralRestore the alignment. Write elog entries.
I often find that the mirrors are left mis-aligned (like in X-arm mode) when I come in for the locking, including tonight.
As Rob stated repeatedly in the past elog, leaving the mirrors mis-aligned for a long time without a reason is an abomination.
It will cause a slow drift of the mirrors and the lock acquisition work is severely slowed down as I have to run the alignment script many times.

I also found that the GPIB-Ethernet box (named teofila) was taken away from the SR785 hooked up to the CM board.
I found it connected to Alberto's setup. Instead, another GPIB box was left on the SR785 but not connected.
I couldn't find any elog entry about this.
This is totally unacceptable.
The SR785 has been used as a very important tool for monitoring the AO path loop gain during the power up.
You can use it if you need, but you have to note it in elog.

The other GPIB box left on the SR785 had a wrong name labeled on it. It had a name "ERMINIA", but the IP address written next to the name was actually assigned to "crocetta" in the DNS server on linux1. I don't know who made the label. I put a new and correct label on it.
Now I'm using crocetta for the SR785 so Alberto can keep using teofila.

Anyway, I think recently people are lazy about elog.
Whatever work you did, please put it in the elog even if you think it is trivial.
I also would like to see more detailed elog entries from people. Many of the recent elog entries are too simple or superficial that it is hard for other people to figure out what was really done.
  1496   Sun Apr 19 11:34:33 2009 josephbHowToCamerasUSB Frame Grabber - How to

To use the Sensoray 2250 USB frame grabber:

Ensure you have the following packages installed: build-essential, libusb-dev

Download the Linux manual and linux SDK from the Sensoray website at:


Go to the Software and Manual tab near the bottom to find the links.  The software can also be found on the 40m computers at /cvs/cds/caltech/users/josephb/sensoray/

The files are Manual2250LinuxV120.pdf and s2250_v120.tar.gz

Run the following commands in the directory where you have the files.

tar -xvf s2250_v120.tar.gz

cd s2250_v120


cd ezloader


sudo make modules_install

cd ..

At this point plug in the 2250 frame grabber.

sudo modprobe s2250_ezloader

Now you can run the demo with

./sraydemo or ./sraydemo64

Options will show up on screen.  A simple set to start with is "encode 0", which sets the recording type, "recvid test.mpg", which starts the recording in file test.mpg, and "stop", which stops recording.  Note there is no on screen playback.  One needs an installed mpeg player to view the saved file, such as Totem (which can screen cap to .png format) or mplayer.

All these instructions are on the first few pages of the Manual2250LinuxV120 pdf.



  1517   Fri Apr 24 16:02:31 2009 steveHowToVACcryo pump interlock rule

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

Attachment 1: cryo.png
  1529   Tue Apr 28 16:36:24 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.

Attachment 1: CARM_phases_REFL.pdf
CARM_phases_REFL.pdf CARM_phases_REFL.pdf CARM_phases_REFL.pdf CARM_phases_REFL.pdf
Attachment 2: SRCL_phases_REFL.pdf
SRCL_phases_REFL.pdf SRCL_phases_REFL.pdf SRCL_phases_REFL.pdf SRCL_phases_REFL.pdf
  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.

ELOG V3.1.3-