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  40m Log, Page 42 of 344  Not logged in ELOG logo
ID Date Author Typeup Category Subject
  348   Fri Feb 29 13:51:17 2008 JohnSummaryLSCPD6 response
I checked the response of PD6 using the AM laser. It looks happy enough.

16 averages
-10dBm source power
77.3mV dc on the diode
  359   Wed Mar 5 12:35:09 2008 JohnSummaryComputer Scripts / ProgramsPlot photodiode responses in MatLab
A matlab function to plot the responses of photodiodes. There's still plenty of room for improvement but it should work for all our diodes without any changes. You may want to adjust which points are used in the fit to remove time delay.

% Plot data from diode response measurements
function out = diodeplot(f_Hz,mag_dB,phase_deg,f_beat_MHz)

% $$$ clear all
% $$$ close all
% $$$ clc
% $$$
% $$$
% $$$ mag = dlmread('D:\40m\PD6\M7.txt','\t', 15, 0);
% $$$ phase = dlmread('D:\40m\PD6\P7.txt','\t', 15, 0);
% $$$
% $$$ % Frequency i.e. x-axis
% $$$ f = mag(:,1);
% $$$
% $$$ % Magnitude in dB
% $$$ mag_dB = mag(:,2);
% $$$
% $$$ % Phase in degrees
% $$$ phase_deg = phase(:,2);
% $$$
% $$$ % Frequencies of interest
% $$$ f_beat_MHz = [33 133 166 199]*1e6;
% $$$
% $$$ diodeplot(f, mag_dB, phase_deg, f_beat_MHz)

% x axis limits
xmin = 10e6;
xmax = 500e6;

% Unwrap phase
phase_deg = (180/pi)*unwrap((pi/180)*phase_deg);

%Find values at our freqeuncies of interest
Mag_f_beat = interp1(f_Hz,mag_dB,f_beat_MHz);

% Remove the time delay from the phase data
% (May want to adjust which points are selected here)

straight = @(a, x) a(1) * x + a(2);

xdata = f_Hz;
ydata = phase_deg;

aguess = [10 0.1];
a = lsqcurvefit(straight,aguess,xdata,ydata);
fit = straight(a,xdata);

phase_deg = phase_deg-fit;

ha = axes('units','normalized','position',[0 0 1 1]);
hi = imagesc(I);
colormap gray
set(ha,'handlevisibility','off', ...
hold on
hold off
ylabel('Phase/ degrees', 'FontSize',12)
xlabel('Frequency/ Hz', 'FontSize',12)
title('Removing the time delay','FontSize',16)
box off

set(gcf,'Color', [1 1 1])
subplot(4,1,[1 3])

title('Response of PD6','FontSize',16)
ylabel('Magnitude/ dB', 'FontSize',12)
xlim([xmin xmax])

MagLayout = get(gca, 'Position');
YLimits = get(gca, 'YLim') ;
LabelExt = [];

for ivar = 1:length(f_beat_MHz);

a = text(f_beat_MHz(ivar),1.05 * min(Mag_f_beat),...
sprintf('%2.1fdB @ %dMHz', Mag_f_beat(ivar),f_beat_MHz(ivar)/1e6),...
'VerticalAlignment','top','BackgroundColor',[.7 .9 .7],...
'Margin',0.5, 'Rotation',90);
LabelExt = [LabelExt; get(a,'Extent')];
LabelPos = get(a,'Position');


% Change YLim so that it is around the bottom of the labels
% There must be a better way
set(gca, 'YLim', [min(LabelExt(:,2)) YLimits(2)])

% Remove the last tick mark so that it doesn't overlap with the
% +180 of the phase plot
YTickLabelNew = str2num(get(gca, 'YTickLabel'));
YTickNew =[[] YTickLabelNew(2:end) ];
set(gca,'XTickLabel', [], 'YTick', YTickNew)

% Add lines now we know what the YLims are
for ivar = 1:length(f_beat_MHz);
line([f_beat_MHz(ivar) f_beat_MHz(ivar)], get(gca, 'YLim'))

xlim([xmin xmax])
ylabel('Phase/ degrees', 'FontSize',12)
xlabel('Frequency/ Hz', 'FontSize',16)
PhaseLayout = get(gca, 'Position');
PhaseLayout(4) = MagLayout(2)-PhaseLayout(2);

% Make the top of the phase plot align to the bottom of the
% magnitude plot
set(gca, 'Color', 'None', 'Position',PhaseLayout, 'YTick',[-180:45: ...
set(gcf,'units','normalized','outerposition',[0 0 1 1]);
  360   Wed Mar 5 12:51:48 2008 JohnSummaryLSCInitial Ligo Arm finesse versus lambda
I've taken the coating recipes for the initial ligo arm cavity from Rana's web page (ligo.caltech/edu/~rana/mat/)
and plotted the finesse as a function of wavelength. There is some uncertainty over the indices of refraction but
the main conclusion remains unchanged - i.e. it appears that using other wavelengths will be difficult.
Stefan is looking at how to tune the layers of any new mirrors to make dichroic optics.
  387   Thu Mar 20 17:45:36 2008 ranaSummaryASSAdaptive Filtering in the ASS system
Over the past couple weeks we (Matt, Alex, Rob, me) have worked on getting an adaptive filter
system working. We wanted to load this system into c1ass to use this processor. The dither alignment
system hasn't been employed here for awhile and so we have just used this box.

The signals are acquired in the PEM ADCU. Alex modified the code there to send the signals over to
the new system. We also get the SUS-LSC_OUT signals from each of the suspensions so that we can
try to minimize them.

The outputs of the adaptive filter go into the unused SUS-MCL inputs of all the suspensions (except
for MC2). In the current setup, we have 6 accelerometers and 1 seismometer around the MC to be used
to demonstrate the principle of the whole thing.

Much more documentation and description of everything is necessary. We'll try to get Matt, Rob, and Alex
to use the elog.
  394   Sat Mar 22 22:39:02 2008 mevansSummaryCDSDirect Form 2 filters are bad
Here I show a comparison between the filter algorithm currently used in LIGO (Direct Form II), and an alternative algorithm designed to reduce numerical noise. The input signal is

x = sin(2 * pi * t) + 1e-9 * sin(2 * pi * (fs / 4) * t);

where fs = 16384 is the sample rate. The filter is a 4th order notch at 1Hz (f_poles = f_zeros = 1Hz, Q_poles = 1, Q_zeros = 1e6). It is clear that the DF2 algorithm produces a noise floor that is, for this simple filter, 1e-11 / rtHz smaller than the input drive amplitude (see plots). That should probably be scary given how many second-order-sections we run our signals through. The low-noise form does a somewhat better job. The low-noise algorithm has the same memory and computational requirements as DF2, and our CDS guys have the code in hand. I suggest we start testing soon.

(The code is included below. You will need my Matlab library to run the top level test script.)
  397   Sun Mar 23 10:42:54 2008 ValeraSummaryElectronicsRFAM of the RF stabilization box is measured
I reconstructed Tobin's setup to measure the RFAM after the RF stabilization box in the 166 MHz modulation path.
The setup consisted of the splitter and the mixer followed by the RF low pass filter and the SR560 (gain x100).
The RF level into splitter was 20 dBm. The Mini-Circuits ZLW-3H (17 dBm LO) mixer was used. The LO was taken
straight out of the splitter and the RF path was attenuated by 11 dBm, The DC out of the mixer was 700 mV.
The noise floor was measured with the RF input of the mixer terminated on 50 Ohm. The 45 MHz measurement
in broad band setting looks better than the noise floor at high frequencies. I am not sure what was wrong with
one or both of those measurements. The 9 MHz measurements are above the noise floor.

The RFAM meets the AdvLIGO requirements in the detection band (f > 10 Hz).

The attached zipped files are:
SRS003 9 MHz DC-200 Hz
SRS004 9 MHz DC-26 kHz
SRS006 45 MHz DC-200 Hz
SRS005 45 MHz DC-26 kHz
SRS007 Noise floor DC-200 Hz
SRS008 Noise floor DC-26 kHz
  399   Mon Mar 24 20:15:03 2008 JohnSummaryComputersc1susvme2
c1susvme2 isn't behaving itself. It keeps getting out of sync and/or giving a red status light.

After going through the usual restart procedures a few times (unsuccessfully) we power cycled the c1susvme & c1sosvme crates. We think everything came back okay.

We still can't get the status and CRC (cyclic redundancy check) to return to normal on c1susvme2. If Alex is around tomorrow please ask him to take a look.
  407   Mon Mar 31 14:01:40 2008 jamieSummaryLSCSummary of DC readout PD non-linearity measurements
From March 21-26, I conducted some measurements of the response non-linearity of some mock-up DC readout photodetectors. The detectors are simple:
Vbias ---
        |-------- output
This is a description of the final measurement.

The laser current modulation input was given a 47Hz sine wave at 20mV. A constant small fraction of the beam was shown onto the reference detector, and a beam that was varied in DC power level was incident on the test detector. Spectra were taken from both detectors at the same time, 0.25Hz bandwidth, over 100 averages.

At each incident power level on the test detector, the Vpk in all multiples of the modulation frequency were measured (ie. V[i*w]). The difference between the 2f/1f ratio in the test and reference was then calculated, ie:
V_test[2*w]/V_test[1*w] - V_ref[2*w]/V_ref[1*w]
This is the solid black line in the plot ("t21-r21_v_power.png").

The response of a simulated non-linear detector was also calculated based on the Vpk measured at each harmonic in the reference detector, assuming that the reference detector had a purely linear response, ie:
V_nl[beta,2*w]/V_nl[beta,1*w] - V_l[2*w]/V_l[1*w]
these are the dashed colored lines in the plot ("t21-r21_v_power.png").

The result of the measurement seems to indicate that the non-linearity in the test detector is less than beta=-1.

The setup that was on the big optics table south of the laser, adjacent to the mode cleaner, is no longer needed.
  410   Thu Apr 3 18:33:17 2008 AndreySummaryEnvironmentStatus of Weather Station

During the last two days some things related to weather station have been improved.

1) Startup file for the computer (processor) 'c1pem1' was changed so that now 'c1pem1' can be rebooted from "Linux1". Computer 'c1pem1' is responsible for communicating data between 'Weather Monitor' and control UNIX machines. Before April 1st it was impossible to reboot the computer 'c1pem1'. Now 'c1pem1' runs without difficulties.

2) It was determined that some ethernet cables of category "cat 5" were bad. I replaced one short cat 5 cable between 'c1pem1' and 'network-switch board' in the neighboring computer rack, and I still need to replace the internet ending of another long (~20 meters) cat 5 cable after Alex Ivanov will bring the tool for that.

3) 'Weather monitor' and 'WeatherLink' are temporarily moved away from their "nested" positions on the north wall, and they are now in the proximity of processor 'c1pem1'. Thus the signal about "Inside Temperature" goes into 'c1pem1' computer without any additional ethernet cables, and "inside temperature" is correctly displayed on the "Checklist" adl. MEDM screen on the control UNIX machines. The cable with a signal from the roof sensors (which might be dead due their 7-year age) is temporarily disconnected from the 'Weather Monitor'.

Result: 'Weather Monitor' and computer (processsor) 'c1pem1' are alive, they communicate reasonable "Inside Temperature" to the control UNIX-machines.

The fate of the outside sensors is currently unknown, I plan to go to the roof together with Mr. Steve Vass tomorrow and try to determine what should be done with them.

I am also writing (right now) a wiki-40 page which explains what is the "Weather Station" and what is its status.
  413   Thu Apr 3 19:27:50 2008 AndreySummaryPhotosTour for prospective grad students
Last Friday (March 28), there was a tour of 40-meter lab for prospective graduate students.

Rana showed to the prospective students the interferometer. See pdf-attachment with pictures (two pictures of Rana with undergraduates (I took them) and two old pictures which I discovered on the memory card of Nikon d-40, it was not me who took those two last pictures).
  414   Fri Apr 4 16:54:06 2008 AndreySummaryEnvironmentWeather station is fully alive

After today's trip to the roof of our building the weather station seems to be completely resurrected!

We went to the roof together with Steve Vass, and we discovered that:

(1) Sensors of wind speed, wind direction and the bowl that measures the amount of precipitation do not have any visible defects, so there is no problem with all those sensors even after being outside for seven years.

(2) We discovered that there are cable junctions located on the roof, and those junctions were located close to the rim (edge) of the roof, before the cables go inside of 40-meter lab room. The taping in the place of the junction was not good due to the age, and the connections between the cables were disrupted (cable endings were out of the connectors). Therefore, no signal from the roof sensors could be transferred to the 'Weather Monitor'. It was not wise from the person who installed the weather station to leave the fragile cable connections outside, on the roof, because the length of the cables allowed to locate those three connectors inside of the building.

See the attached PDF-file with pictures.

(3) After the cables were plugged into the connectors, these cable junctions were gently pulled into the inside of the 40-meter interferometer room. These cable junctions should not be located outside of the building!

Immediately after all the above-mentioned steps, the reasonable indications of outside temperature, humidity, pressure, wind speed and direction appeared on the 'Weather Monitor'.

In order to see if there is any problem of communication between the 'Weather Monitor' and UNIX control computers through 'c1pem1', I rolled out two brand new black cat-5 ethernet cables on the floor of the interferometer room (they are on the floor temporarily, the ethernet cable will go from the floor into the ceiling cable tray eventually), connected the two cables together through freshly purchased from Caltech bookstore cable connectors, and thus connected the 'Weather Monitor' to the processor 'c1pem1'.

Result: Now we can see reasonable indications of outside temperature, pressure, amount of precipitation, wind speed and direction on the EPICS screen! Moreover, these indications are changing with time.

As a reminder for everyone: standard atmospheric pressure is about 101kPa, so the indications of pressure as 99900Pa is quite reasonable.

One thing is not clear for me yet: wind speed on the 'Weather Monitor' is fluctuating between 2 and 4 mph, while MEDM EPICS-screen values are fluctuation in the range between 0 and 3mph.

Many thanks to Steve Vass and Alexander Ivanov for their help.
  420   Wed Apr 16 09:47:35 2008 AndreySummaryPEMWeather Station
The weather station is functional again.

The long ethernet Cat5 cable connecting 'WeatherLink' and processor 'c1pem1' was repaired yesterday, namely the RJ45 connector was replaced,
and information about weather conditions is now again continuously being transferred from the 'Weather Monitor' to the control UNIX computers. We can see this information in 'c0Checklist.adl' screen and in Dataviewer.

Below are the two sets of trends for the temperature, wind speed and direction, pressure and the amount of precipitation.

The upper set of trends ("Attachment 1") is "Full Data" in Dataviewer for the 3 hours from 6.30AM till 9.30AM this morning,
and the lower set of trends ("Attachment 2") is "Minute Trend" in Dataviewer for 15 hours from 6.30PM yesterday till 9.30AM this morning.

I also updated the wiki-40 page describing the Weather Station and added to there a description of the process of attaching the RJ45 connector to the end of ethernet Cat5 cable. To access the wiki-40 page about the "weather station" you should go from the main page to "PEM" section and click on "Weather Station".
  422   Wed Apr 16 21:11:12 2008 ranaSummaryDAQAA/AI Filters for the DAQ & FE systems
I used Foton to make up some new filters which will be used all over the project in order to downsample/upsample.

There will be 2 flavors:

  • The first one will be a downsampling filter for use in the DAQ system.
    Whenever you specify a sampling rate in the .ini files below the natural rate of the ADC,
    the data will be downsampled using this filter (called ULYAW_0 in the plot). This one was
    designed for flat bandpass and a 'good' bandstop but no care given to the phase shift.

  • The second one will be used in the FE systems to downsample the ADC signal which is often
    sampled at 64 kHz down to something manageable like 2k or 16k. This one was tweaked for
    getting less phase lag in the 'control' band (usually 3x or so below Nyquist).

Here is the associated filter file:
# DESIGN   ULYAW 0 zpk([0.512+i*1024;0.512-i*1024;2.048+i*2048;2.048-i*2048], \
#                      [515.838+i*403.653;515.838-i*403.653;318.182+i*623.506;318.182-i*623.506;59.2857+i*827.88; \
#                      59.2857-i*827.88],0.988553,"n")
# DESIGN   ULYAW 1 zpk([0.512513+i*1024;0.512513-i*1024;1.53754+i*2048;1.53754-i*2048], \
#                      [200+i*346.41;200-i*346.41;45+i*718.592;45-i*718.592],1,"n")
# DESIGN   ULYAW 2 zpk([0.768769+i*1024;0.768769-i*1024;1.53754+i*2048;1.53754-i*2048], \
#                      [194.913-i*331.349;194.913+i*331.349;53.1611+i*682.119;53.1611-i*682.119],1,"n")
###                                                                          ###
ULYAW    0 21 3      0      0 DAQAA         0.00091455950698073    -1.62010355523604     0.67259370084279    -1.84740554170818     0.99961738977942
                                                                   -1.72089534598832     0.78482029284220    -1.41321371411946     0.99858678588255
                                                                   -1.85800352005967     0.95626992044093     2.00000000000000     1.00000000000000
ULYAW    1 21 2      0      0 FEAA            0.018236566955641    -1.83622978049494     0.85804776530302    -1.84740518752455     0.99961700649533
                                                                   -1.89200532023258     0.96649324616546    -1.41346289594856     0.99893883979950
ULYAW    2 21 2      0      0 ELP             0.015203943102927    -1.84117829296043     0.86136943504058    -1.84722827171918     0.99942556512240
                                                                   -1.89339022414279     0.96048849609619    -1.41346289594856     0.99893883979950
  429   Sun Apr 20 18:23:27 2008 ranaSummaryLSClocking attempts
I noticed that the adaptive FF for the MC had stopped doing anything; this turned out
to be that the MC lost lock and the mcdown script turned off the FF path to MC1.

Although there's no elog, it looks like there was ~60 attempts at locking the IFO
between 12:38 and 4:27 on Saturday afternoon. I'm attaching here a plot showing
lock attempt durations and a histogram of lock times.
  431   Sun Apr 20 23:39:57 2008 ranaSummarySUSMC1 electronics busted
I spent some time trying to fix the utter programming fiasco which was our MCWFS diagonalization script.

However, it still didn't work. Loops unstable. Using the matrix in the screen snapshot is OK, however.

Finally, I realized from looking at the imaginary part of the output matrix that there was something
wrong with the MC1 drive. The attached JPG shows TFs from pit-drives of the MC mirrors to WFS1.

MC1 & MC3 are supposed to have 28 elliptic low pass filters in hardware for dewhitening. The MC2
hardware is different and so we have given it a software 28 Hz ELP to compensate. But it looks like
MC1 doesn't have the low pass (no phase lag). I tried switching its COIL FM10 filters to make it
switch but no luck.

We'll have to engage the filters to make the McWFS work right and to get the MC noise down. This
needs someone to go check out the hardware I think.

I have turned the gain way down and this has stabilized the MC REFL signal as you can see from the StripTool screen.
  441   Thu Apr 24 11:50:10 2008 josephbSummaryComputer Scripts / ProgramsUseful tidbits learned while tracking the network setup
In process of understanding the network setup I've learned several things:

1) The status lights on C0DAQ_RFMNETWORK.adl are controlled by the fiber network, as opposed to the ethernet network. However, even if everything is working properly on the VME end, you may still need to reboot it in order to be able to contact it via the ethernet (ssh or telnet).

2) After disconnecting the hub out by 1Y9, I was able to telnet into c1vac1, but not c1vac2. I was told that the Turbo pump and Ion pump readbacks on C0VACMONITOR.adl had not been working for awhile (years?). So I went out and rebooted the c1vac2 card. This seemed to restore the epic channels and we now have correct readbacks on the turbo pumps. The ion pumps all are reading no voltage, which is good because they're turned off. However C1:Vac-IPSE_mon is reading "On", although Steve assures me the actual unit is currently off, so there may be a minor channel issue there.
  444   Thu Apr 24 22:06:47 2008 AndreySummaryComputersEthernet Cables and Hubs
Today in the morning (between 8.30AM and noon) Joe and I were working on understanding which ethernet cables connect "processors controlling the work of equipment in the interferometer room" and "Internet hub in the computer room".

Firstly, we took off several times the blue ethernet cables from the router located near ETMX in the morning. We were trying to understand which port in the hub is responsible for the interaction with that processor.

Secondly, we were working on reviving the connection with the computer controlling vacuum in the interferometer.

Later in the middle of the day (around 2PM) Joe continued some work with ethernet cables without me. We plan on continuing the cable work on Friday morning. A better and more detailed elog will appear then.
  449   Fri Apr 25 13:53:11 2008 josephbSummaryComputersNetwork setup
This is the promised more in detail summary from Andrey's log ID 444.

What we did was go around to each hub, one at a time, unplug the network connection, and figure out which light on which hub went out. We then, went back to the control room, confirmed that we were still able to talk to the devices connected to the hub, and if not, rebooted them. This process was repeated for each hub.

As it stands, the hubs located at the ends of arms (in racks 1X4 and 1Y9) are connected to the really old 24 port 10 Base T hub located in 1Y7. In addition, the 5 port SMC hub is plugged into the 8 port SMC switch in 1Y5 (which actually has enough ports to simply move all the connections over to it, so I'm not sure why there are two...).

All other hubs/switches are connected back to the control room 24 port switch.

Attached is a simple diagram of the network connections for the 40m lab.
  452   Sat Apr 26 01:45:38 2008 AndreySummaryPEMWeather Station enhancement
Two more things concerning weather monitoring have been done during this week.

1) A Dataviewer template was created, so that it allows to see "real-time" information from weather channels immediately, without adding many channels "manually".

If one wants to use this template,
open Dataviewer -> "File" -> "Restore Settings", /cvs/cds/caltech/users/Templates/Dataviewer_Templates/Weather.xml.

2) I wrote a couple of Matlab scripts that allow to read data (minute trends) from the Dataviewer channels over some time in the past, save the received data in mat-files, and plot those minute-trends. Thus, one can get plots that are very much similar to what one can see in Dataviewer. These two Matlab files are located in the directory
"/cvs/cds/caltech/users/weather_station". File "WeatherReading.m" allows reading from the weather channels (paths to mDV directory must be configured before using my script), file "WeatherTrends.m" allows plotting of those minute trends.

Unfortunately, hardware problems arise very often if we want to read for a somewhat long time in the past, so until now I have not succeeded in getting trends for more than 20 minutes. As an example, see the attached png-file with the 20-minutes trends of data from Thursday evening.

3) So far I did not have success in learning how to recalculate pressure from Pascals to mbars in EPICS (although I tried google-search).

4) I am making every effort in recent weeks not to put any personal or non-scientific information into elog, but this message could be important for all of us, so I cannot resist:
a shark in the Pacific Ocean has killed a swimmer near San-Diego (I saw this in russian news and then made a quick google-search).
  461   Wed Apr 30 20:48:58 2008 AndreySummaryPEMNew Weather Channels

I created the new channels for the weather station, all letters are capital ones. They are of the form "C1 : PEM-WS_PARAMETER" where "PARAMETER" is temperature, pressure, wind,... characteristics (names are self-obvious).

These new weather channels are indicated on the "Weather Checklist" MEDM screen. Also, units of pressure were changed from Pascal to torr and mbars.

The new weather channels are also visible in Dataviewer. I updated the template, and as an example of Dataviewer data I attach the following 5-hour trends of weather parameters from 3.30PM to 8.30PM on April 30th.
  468   Thu May 8 01:07:24 2008 ranaSummaryLSCFrequency Noise test: MC Trans Backscatter
There is a wandering hump in the MC_F spectrum. It can move around on the time
scale of seconds between 40 and 200 Hz. It has an amplitude ~5-50x above the background spectrum. This seems new; I don't remember it
from a year ago. It is there in the IFO unlocked as well as the IFO locked as well as the locked + CM mode.

Tapping the AS table and/or the PSL table enclosures produces a broadband increase in the MC_F spectrum but doesn't
selectively effect the hump.

We thought it might be backscatter from the MC TRANS path and so we stuck in one of Steve's cool black glass V's into
this space. No effect. We should design a black glass V dump which we can replicate in large quantities for us and for
the sites. Something like the one on the LSC PDs, but with a 1 sq. inch opening area and a 2 inch depth.

We have also done this on the MC2 - TRANS beam before. No noise reduced there either.

The noise hump is appearing in MC_F but not in CARM_IN1 (after the CM handoff) so it seems like the MC has enough gain
to squash it. This also exonerates the MC REFL path since anything there would not be effected by the MC servo gain and
so would be visible in CARM.

My best guess is that there is something really, really scattery on the PSL table. But for now it looks like this is not a
big factor in the locking
  469   Thu May 8 01:50:25 2008 ranaSummaryASCArm Cavity HOM Resonances
Nothing new, but I calculated the frequencies of the first 22 higher order transverse modes and thought I might as well list them here.

To do this I took formula (23) from page 762 of Siegmans book and put it into this form:
dfmn =   ----- * (m+n) * acos(sqrt(g1*g2))

and then calculated them from m+n = 1..22 (22 is not a magic number).

I also used the 'mod' function of matlab to calculate the frequency mod FSR so that we would know how far away
from a cavity resonance it is. I took as parameters: Larm = 38.55 m, Ritm = 1e6 m, Retm = 57.1 m. Kirk measured
the arm length some time ago; we need to measure the arm g-factor...maybe we'll put Tobin on this when he comes
by for a visit.

1.1936 (TEM01, TEM10)
0.8859 (TEM22, TEM13, TEM31)
0.2706 (TEM55, ...)
  470   Thu May 8 02:06:13 2008 ranaSummaryCOCThermal Lensing in the ITMs and BS may be a problem
The iLIGO interferometers start to see thermal lensing effects with ~2W into the MC, a recycling
gain of ~50, and a beam waist on the ITMs of ~3.5 cm.

At the 40m, the laser power into the MC is 1/2 as much, the recycling gain is 4-5x less, but the
beam on the ITM has a 3 mm waist. So the power in the ITM bulk is 10x less but the power density
is 100x more
. Seems like the induced lens in the ITM bulk might be larger and that if there's
significant absorption on the ITM face (remember our Finesse is 4-5x higher) the beam size in the
arm cavity may also change enough to measure.

Someone (like Andrey) should calculate how much the beam sizes change with absorbed power.
  476   Wed May 14 13:14:19 2008 AndreySummaryComputersReflective Memory Network is restored

Reflective Memory Network is restored, all watchdogs and oplevs are returned to the "enabled" state.

In order to revive the computers, several things were done.

1) Following Mr. Adhikari's elog entry #353, I walked around the interferometer room, and switched off the power keys in all crates with computers whose names are contained in the MEDM Reflective Memory screen, including the rack with the framebuilder. By the way, it was nontrivial to find the switch in the 1Y4 crate that would shut off/on processors "c1susvme1" and "c1susvme2": the switch turned out to be located at the rear side of the crate, and it is not a key but it is a button.

2) I was trying to follow wiki-40 computer restart procedures, but every time that I was trying to run "startup.cmd" screen from the corresponding target subdirectory, I got the error message "Device or resource busy".
By the way, one more thing was learned: if you firstly open in terminal burtgooey, select the snap file, then reboot the processor, and then will try to burt-restore it, you will get the message "Status Not OK". In order to really burt-restore the processor which was recently rebooted, you need to close the terminal with burtgooey and open burtgooey in a new terminal window which should be opened after rebooting the processor.

Feeling that my activities according to wiki-40 procedures do not revive computers, I invited Alex Ivanov.

3) Alex tried to touch the memory card in "c1iovme" in rack 1Y2, because once before this card failed causing network problems, but this did not help.

4) We shutted off and restarted again (pressing the power-switching button) the black Linux machine "c1dcuepics" (located in the very bottom below the framebuilder). Alex says that this machine is responsible for all EPICS. It was not restarted for 182 days, and probably some process there went wrong.

After restarting this machine "c1dcuepics" we were able to follow wiki-40 procedures for restarting all other computers (whose names are on the MEDM RFM network). We ran correcponding "startup.cmd" files and burt-restored them without error messages.

Now all the computers work and communicate in a proper way.

Mr. Joseph Betzwiezer was helping me with all these activities (we decided that it is more important that cameras for now), thanks to him. But our joint skills turned out to be insufficient, so Alex Ivanov's contribution was the most important.
  480   Thu May 15 14:39:33 2008 CarynSummaryPEMfiltering mode cleaner with mic
Tried filtering for mode cleaner data(C1:IOO-MC_L) using a siso-firwiener filter and microphone data(C1:PEM-AS_MIC) for noise input. The noise reduction in mode cleaner data using the microphone-filter is comparable to the noise reduction when an accelerometer(C1:PEM-ACC_MC1_X) filter is used. See attached graphs.
  481   Thu May 15 16:24:18 2008 josephbSummaryCameras 
The GC750 camera is currently looking at a very small pickoff of the PSL output (transmission of a Y1-1037-45-S mirror). The plan is to take images tomorrow with it and the GC650 from the same spot and do comparisons.

For those interested, the camera can be run with two codes, from mafalda. Use ssh -X mafalda to login, to allow the live stream to work with the SampleViewer code. The codes can be found in:




Type Snap --help for a list of options for that program. Click the circle looking thing in SampleViewer to start the live stream. Note only 1 of the two programs can be running at a time, and the only way to change settings (such as exposure length) is with Snap at the moment.
  482   Fri May 16 14:38:50 2008 josephbSummaryCamerasTwo cameras setup
I've changed the pickoff setup from yesterday for the GigE cameras to include a 33% beam splitter (first one I could find). The reflection is going to the GC650 (CCD camera) while the transimission is going to the GC750 CMOS camera. This means the CMOS camera has roughly twice the light incident as the GC650 and should be kept in mind in all comparisons. The distances from the beam splitter are approximately the same both cameras, but some more accurate positioning might be useful.

Its very easy to get the GC650 camera into a bad state where you need to go out and cycle the power (simply unplug and re-plug in the power supply either at the camera or outlet). If the ListCamera program doesn't see it, this is probably necessary.

Andrey added at 6.30PM: Actually the 650 camera keeps crashing constantly. Every time I attempt to capture an image, the camera fails.
  484   Sun May 18 18:14:30 2008 ranaSummaryComputer Scripts / Programsautlockers and cron
Today I noticed that the MC was unlocked, the MC autolocker was off, the PSL autolocker was off,
and the PSL Slow loop was off.

Reading through .log files and our elog it seems like things have been this way since Tuesday
when Andrey went around rebooting computers to bring things back.

And it looks like the ETMY optical lever is dead.

I restarted the PSL & MC scripts on op340m. I also locked and aligned the X arm to verify that
not everything is broken. The Y Arm is unalignable until we replace the HeNe.
  485   Sun May 18 18:44:48 2008 ranaSummarySUSOptical Lever SUM Trend - 80 days
I used the OL-Trend.xml dataviewer template to make this plot. Looks like the ETMY optical lever
slowly degraded over the last few months and then finally died 10 days ago. Would someone please
replace this laser and tune the lens position to minimize the spot size on the quad?
  494   Fri May 23 21:21:52 2008 CarynSummaryGeneralfiltering mode cleaner with wiener filter
I tried filtering some saved MC_L data (from Mon May19 4:30pm) with multiple MISO filters of different orders, with various sampling rates, at different times. Plotted the max rms error (where error is signal minus signal-estimate). 2min of data (around Mon May19 4:30pm) were used to calculate each filter. And each filter was applied to data at later times to see how well it performed as time progressed. Plots are attached. There appears to have been a disturbance during the 3rd hour. Rana pointed out perhaps it would be better to use data from the evening rather than during the day.
  497   Sun May 25 20:30:25 2008 ranaSummaryPSLPMC Mode Matching
I checked the PMC mode matching by ramping the gain down to -10 dB (from +20 dB) and
moving the DC offset around until it caught lock on the different HOMs. Then I recorded
the output power (PMCTRANSPD). The DC offset on this EPICS channel was -0.013 V, so I
used its AOFF field to zero this out. Here is a list of the power in the largest modes:
Mode    Power (V)
----    ---------
00        2.7
10        0.2
04        0.04
02        0.02
BE        0.36      **Bull's Eye mode is TEM02 + TEM20. This can be fixed by lens adjustment.

N.B. To make a PNG file with DTT, just make an EPS file -- then use the eps2png perl script.
  503   Thu May 29 15:58:44 2008 JohnSummaryIOOMC realignment
I repeatedly adjusted the yaw of the upper mirror on the input periscope and re aligned the MC. With the PRM aligned I tried to optimise MC transmission and DC refl simultaneously. I subsequently centred the beams on WFS1/2. Attached is a 30 day trend of MC alignment and transmission.
  512   Tue Jun 3 02:15:29 2008 AndreySummaryCamerasFitting results

There have been a lot of work going on related to the processing of images captured by the cameras GC-650 and GC-750 recently.

In the end of the week of May 30 Joseph and me (Andrey) installed the two cameras capturing the images of the pick-off of the main beam on the PSL optical table. The cameras are located after the picked-off beam going towards the "PSL position QPD", after the 33-66 beamsplitter (33% of reflection and 66% of transmission).

Initially (on May 30) the GC-650 camera was taking the images of reflected beam, while the camera GC-750 was taking images of transmitted beam. On Monday June 2 we switched the positions of the cameras, so GC-650 appeared to be on the path of the transmitted beam and GC-750 on the path of the reflected beam.

I (Andrey Rodionov) was able in the weekend to succeed in writing a Matlab program that performs the two-dimensional Gaussian fitting of the captured images, and I used that program to fit the images from the cameras.

The program fits the camera data by a two-dimensional Gaussian surface:

Z = A * exp[ - 2 * (X - X_Shift)^2 / (Waist_X)^2 ] * exp[ - 2 * (Y - Y_Shift)^2 / (Waist_Y)^2 ] + CONST_Shift,

where A, X_Shift, Waist_X, Y_Shift, Waist_Y, CONST_Shift are 6 parameters of the fit.

Attached are the pdf-files showing the results: images taken with our cameras, the 2-dimensional Gaussian fit for these images and the surfaces of residuals. Residuals are differences between the exact beam profile and the result of fitting. In normalized version of residual graph I normalize it by the first coefficient of fitting A, the factor in front of the exponents.
  518   Wed Jun 4 16:25:06 2008 CarynSummaryPEMmicrophone moved
The microphone 'C1:PEM-AS_MIC' has been moved right a bit. This change didn't seem to have much effect on filtering the 'C1:IOO-MC_L' signal, at least not compared to how the filter changes with time. Also used microphone data to filter MC_L data using firwiener filter/levinson. The N(order) and sample rate were varied to see how the filter changed. Attached are graphs of the max(rms(noise_estimate)) vs N or IR for varying srate. Note that filtered_signal=signal-noise_estimate. So, the larger the noise_estimate, the more the filter subtracts from the signal.
Green-filtered signal
blue-noise estimate
red-MC_L signal
note decreasing sample rate is more effective than increasing N (higher N takes more time to compute)
note sample rate doesn't change the max(rms(noise_estimate)) very much if impulse response time remains constant
note the 64hz, N=7000 (impulse response about 110s) filter is a better filter than the 512Hz, N=7000(impulse response about 14s)
  522   Fri Jun 6 11:19:13 2008 CarynSummaryPEMFiltering MC_L and MC_F with PEM:ACC and microphone
Tried to filter MC_L and MC_F with acc/seis data and microphone data using wiener filter (levinson)

-Used get_mic_data.m and miso_filter_lev.m to make SISO filter for 2 minutes of IOO-MC_F data. Used PEM-AS_MIC signal as noise input data. Filters calculated at initial time were applied to later data in 1 hour intervals.
-microphone filter did not seem to filter MC_F very well in high frequency range using this filtering procedure.
-residual is larger than est (see MC_F pdf)
-Used do_all_time_lev.m to make graph of max(rms(residual)) to N(order) for different times.(note for each N, filter was calculated for initial time and then applied to data at other times).
-relation of max(rms(residual)) to N(order) is time sensitive (note-on graph, time interval is 1hour) (see MC_F pdf)
-Presumably, max(rms(residual)) should decrease as N increases and increase as time increases since the filter probably becomes worse with time. I think the reason this isn't always true in this case is that the max(rms(residual)) corresponds to a peak (possibly a 60Hz multiple) and the wiener filter isn't filtering out that peak very well.

-Used get_z_data.m and miso_filter_lev.m to make MISO filter for 2 minutes of IOO-MC_L used the following signals as noise input data
-Filter was applied to later data in 2hour intervals.
-Used do_all_time_lev.m to make graph of max(rms(residual)) to N(order) for different times.(note for each N, filter was calculated for initial time and then applied to data at other times).
-acc/seis filter seemed to filter MC_L OK for 128,256,512Hz srates. 64 Hz wasn't ok for certain N's after a period of time.
-residual is smaller than est for srates not 64Hz (see MC_L pdf)
-residual is larger than est for 64Hz at N=1448 for later times (see MC_L pdf)
-relation of max(rms(residual)) to N is not as time sensitive for higher sample rates (note-on graph, time interval is 2hours) (see MC_L pdf). Perhaps the levinson 64Hz sample rate filter doesn't do as well as time passes for these signals. When the filter didn't do well, the max(rms(residual)) seemed to increase with N.
-For 512Hz sample rate filter the max(rms(residual)) decreased with time. If the max(rms(residual)) were an indication of filter performance, it would mean that the 512Hz filter calculated at the initial time was performing better later as hours passed by! Perhaps max(rms(residual)) isn't always great at indicating filter performance.

Programming notes
-I had to modify values in do_all_time_lev.m to get the program to loop over the srates,N's,times I wanted
-do_all_time_lev.m is not as clean as do_all_lev.m
-for making the plots do_all_lev.m (which isn't really a procedure and is messy) has some examples of how to plot things from do_all_time_lev.m.
  538   Wed Jun 18 16:07:57 2008 robSummaryComputersRFM network down

The RFM network tripped off around noon today. It's still down. The problem appears to be with the EPICS interface (c1dcuepics). Trying to restart one of the end stations yields the error: No response from EPICS.

Possible causes include (but not limited to): busted RFM card on c1dcuepics, busted PMC bus on c1dcuepics, busted fiber from c1dcuepics to the RFM switch. We need Alex.
  554   Mon Jun 23 19:48:28 2008 rana,albertoSummaryIOOStochMon trends (80 days)
Here's a StochMon plot showing the RFAM after the MC. Remember that in these units, 2V means no RFAM
and 0 V means lots of RFAM. Alberto says "the calibration is in Tiramisu". So there you go.
  557   Tue Jun 24 15:15:09 2008 JohnSummaryLSCLocking efforts
Rob, Rana, John

In the past week or so we've been working on reducing the CARM offset using a DC signal (SPOB DC).
We were able to get up to arm powers of around 30 (where a single arm cavity lock is a power of 1)
before instability set in and we would lose lock for, as yet, unknown reasons.

In recent nights locking efforts have taken a few backward steps.

Since last Thursday engaging the AO path has proved troublesome, i.e. engaging it would instantly
cause loss of lock. This seems to be related to problems with the mode cleaner servo. For the past
few nights it has been behaving strangely and could not be operated with the usual super boost stages.
Last night the situation was improved. MC boost stages could be used and the AO path engaged. The
cause of this problem and its spontaneous resolution are not understood.

Last night we were unable to switch CARM to SPOB DC. I've attached a spectrum of the MC2 length signal.
This path is being used for CARM and so gives an indication of the frequency noise after the mode
cleaner. At the moment the plot is calibrated in units of Rana's gut feeling. We already tested to see if
any of the excess noise was introduced by the WFS. No evidence was found. We'll try to make a useful
calibration soon and see if our problems are related to excess frequency noise.

Another realisation from last night was the effect of arm detuning on the analogue CARM path. When CARM is detuned
the coupled cavity pole removes an extra 90 degrees of phase. The digital path has the `moving zero' to compensate
for this. The analogue path has no such compensation and can therefore become unstable at moderate detunings.
We propose trying to reduce the CARM offset further before engaging the analogue path. This will give higher
gain and move the UGF to a region of increased phase margin.
  560   Tue Jun 24 22:43:23 2008 ranaSummarySEIStack TF
  561   Wed Jun 25 00:35:40 2008 KojiSummaryGeneralOptical Layout on the AP table
I have visited the AP table in order to investigate where we are going to put the optical setup for the abs. length meas.
I have attached the PNG and PDF files to share the optical layout. It is not complete. Any comments or corrections are welcome.
  562   Wed Jun 25 01:30:19 2008 JohnSummaryIOOFrequency noise after the MC
I made some (very) rough estimates of the contribution made to the noise after the mode cleaner by three sources.

Seismic noise - how much of the signal is due to the mode cleaner compenstaing for seismic disturbance of CARM.
Actuator noise - coil drivers and DAC noise.
MC_F - estimate of MC_F suppressed by the loop gain.
  566   Wed Jun 25 12:25:28 2008 EricSummaryCameras2D Gaussian Fitting Code
I initially wrote a script in MATLAB that takes pictures of the laser beam's profile and fits them to a two dimensional gaussian in order to determine the position and width of the beam. This code is now (mostly) ported to C so that it can be imbedded in the camera software package that Joe is writing. The fitting works fairly well for pictures with the beam directly incident on the camera, and less well for pictures of scatter off the end mirrors of the arms, since scatter from defects in the mirror have intensities much greater than the intensity of the beam's gaussian profile.

The next steps are to finish up porting the fitting code to C, and then modify it so it can better handle the images off the end mirror. Some thoughts on how to do this are to use a fourier transform and a low pass filter, or to simply use a center-of-mass calculation (with the defect peaks reduced in intensity), since position is more important than beam width in this calculation. The eventual goal is to include the edge of the optic in the picture and use the fit of the beam position in comparison to the optic's position to find the beam's location on the mirror.
  568   Wed Jun 25 13:56:56 2008 JohnSummaryLockingTuesday night locking
Rob, John

Worked to try and reduce the CARM offset using the dc arm transmissions before changing to SPOB DC. This proved somewhat unsuccessful, the offset couldn't be reduced to more than five (arms storing 5x more power than single arm cavity lock).
  573   Thu Jun 26 12:30:40 2008 JohnSummaryLockingCARM on REFL_DC

Try REFL_DC as the error signal for CARM rather than PO_DC.


The PO signal is dominated by sideband light when the arms are detuned so that any misalignment in the recycling cavity introduces spurious signals. Also, the transfer function from coupled cavity excitation to REFL signal is not so steep and hence REFL should give a little more phase. Finally, the slope of the REFL signal should make it easier to hand over to RF CARM.


The REFL signal showed no clear improvement over PO signals. We've gone back to PO.

During the night we also discovered that the LO for the MC loop is low.
  582   Fri Jun 27 14:36:39 2008 JohnSummaryLocking 
Rob, Yoichi, John

Some progress last night:

Switched back to SPOB_DC for CARM.

Shaped the MC LSC loop to reduce excess noise in the 20-30Hz band. Likely the most significant change.
Could this be due to fan noise from the laptop on the SPOB table?

Brought in the AO path earlier (at low gain).

Reduced offset to 6 and increased MC gain before handing off to SPOB. Ramped up AO and MC gain then switched off the
moving zero.

Looks like PD11 is the most promising candidate for RF CARM although the demod phase needs attention.
  591   Sun Jun 29 11:31:52 2008 JohnSummaryPSLISS
I reduced the gain of the ISS (C1: PSL-ISS_VGAGAIN) from 5dB to 2dB. Any higher and it constantly saturates.
  593   Sun Jun 29 18:58:43 2008 ranaSummaryComputers1e20 is too big for AWG and/or IOVME
While testing out my matlab/awgstream based McWFS diagnostic script I accidentally put a
huge excitation into
. This went to 1e20 and then caused
some SUS to trip and c1susvme2 to go red. I tried booting it via the normal procedures
but it wouldn't come back, even after 2 crate power cycles. I also tried booting AWG
via the vmeBusReset, but that didn't do it. Then I booted c1iovme from the telnet prompt
and then I could restart c1susvme2 successfully.

The reason the excitation was so large is that the following filter command is unstable:
[b,a] = butter(4,[0.02 30]/1024);

The low pass part is OK, but it looks like making such a low frequency digital filter
is not. Que lastima. On the bright side, the code now has some excitation amplitude
  594   Sun Jun 29 19:19:47 2008 ranaSummaryIOOTrends of the PSL/IOO Quads over 1000 days
Only IOO POS has been working for the past 2 years. I guess we should recommission the IOO ANG and REFL QPDs
  595   Sun Jun 29 19:53:26 2008 JohnSummaryPSLISS

I reduced the gain of the ISS (C1: PSL-ISS_VGAGAIN) from 5dB to 2dB. Any higher and it constantly saturates.

Seemed to go back to normal after the frame builder came back.
  596   Sun Jun 29 20:09:40 2008 JohnSummaryIOOmcup and mcdown indicators
I edited the mcup and mcdown scripts so that C1IFO_STATE shows when these scripts are running.

I also added indicators to the LockMC screen.
ELOG V3.1.3-