ELOG 40m

New 40m control machine.

I priced out a new control machine from Dell and had Steve buy it.

GigE cards (jumbo packet capable) will be coming seperately.

Specs:
Quad core (2+GHz)
4 Gigs @ 800MHz RAM
24" LCD
low end video card (Nvidia 8300 - analog + digital output for dual head config)

No floppy drive on this one (yet?)

381

Fri Mar 14 15:52:07 2008

I've edited the LSC code to send different signals to the ASS box. Now, instead of the previously selected error signals deemed to be acceptable for the Alignment Sensing and Stabalization system, it sends the LSC control signals for each suspension to the ASS box (in its new incarnation as the Adaptive Susurration Subtraction system). These are the signals after the output matrix, and also after the LSC-[SUS] filter modules.

380

Fri Mar 14 15:06:24 2008

routing PEM -> ASS -> SUS_MCL

Quote:

on ASS RFM 1 has PEM signals at

float at 0x100000 has c0dcu1 first ICS110B chan 1
float at 0x100004 has chan 2
etc.

ASS sends to RFM 0

float at 0x100000 goes to PRM MCL
0x100004 to BS MCL
0x100008 to IMTX MCL
0x10000c to ITMY MCL
0x100010 to SRM MCL
0x100018 to MC1 MCL
0x10001c to MC3 MCL
0x100020 to ETMX MCL
0x100024 to ETMY MCL

You can differentiate between RFM 0 and RFM 1 in the simulink model by adding 0x4000000 to the offsets for RFM 1.

379

Fri Mar 14 14:59:51 2008

josephb

Comparison between GC650 (CCD) and GC750 (CMOS) looking at ETMX

Cameras

Attached are images taken of ETMX while locked.

The first two are 300,000 microsecond exposure time, with approximately the same focusing/zoom. (The 750 is slightly more zoomed in than the 650 in these images). The second are 30,000 microsecond exposures. The la

The CMOS appears to be more sensitive to the 1064 nm reflected light (resulting in bright images for the same exposure time). This may make a difference in applications where images are desired to be taken quickly and repeatedly.

Both seem to be resolving individual specks on the optic reasonably well.

Next test is to place both camera on a Gaussian beam (in a couple different modes say 00, 11, and so forth), probably using the PMC.

378

Fri Mar 14 12:06:29 2008

josephb

GC750 looking at ETMX while locked

Cameras

The GC750 (CMOS) is currently looking at the front of ETMX. Unfortunately, its being routed through a 10Mbit connection (which I will be purchasing a replacement for today), so getting it to send images to Mafalda/Linux 2 or 3 isn't working well, but by using a local gigabit switch and a laptop I can get sufficient speed for full images with the sample viewer.

The attached image is from a full 752x480 reslution with 10,000 microsecond exposure with the X-arm locked. Although it looks like I still need to work on the focusing. Will be switching the GC750 with the GC 650 (CCD) later today and comparing the resulting images.

377

Thu Mar 13 18:20:29 2008

John

New Focus 4003 EOM 29.489MHz

General

I measured the modulation index as a function of drive power using an OSA. Agrees well with spec of 0.2 rad/V.

376

Thu Mar 13 13:15:09 2008

aivanov

new sfotware intall, backup files

New:
op440m:40m>ls -alt /cvs/cds/caltech/target/c1susvme[12]/*.o
-rw-r--r-- 1 controls staff 57920 2008-03-13 13:11 /cvs/cds/caltech/target/c1susvme2/losLinux2.o
-rw-r--r-- 1 controls staff 57976 2008-03-13 13:11 /cvs/cds/caltech/target/c1susvme1/losLinux1.o
op440m:40m>ls -alt /cvs/cds/caltech/target/c1isce[xy]/*.o
-rw-r--r-- 1 controls staff 246861 2008-03-13 13:12 /cvs/cds/caltech/target/c1iscey/losEtmy.o
-rw-r--r-- 1 controls staff 246861 2008-03-13 13:12 /cvs/cds/caltech/target/c1iscex/losEtmx.o
op440m:40m>ls -alt /cvs/cds/caltech/target/c0dcu1/*.o
-rw-r--r-- 1 controls staff 63547 2008-03-12 14:57 /cvs/cds/caltech/target/c0dcu1/dcuDma.o

Backups:
op440m:40m>ls -alt /cvs/cds/caltech/target/c1susvme[12]/*.o.13mar08
-rw-r--r-- 1 controls staff 55960 2005-06-21 13:30 /cvs/cds/caltech/target/c1susvme2/losLinux2.o.13mar08
-rw-r--r-- 1 controls staff 55960 2005-06-21 13:30 /cvs/cds/caltech/target/c1susvme1/losLinux1.o.13mar08
op440m:40m>ls -alt /cvs/cds/caltech/target/c1isce[xy]/*.o.13mar08
-rw-r--r-- 1 controls staff 229793 2007-03-08 11:09 /cvs/cds/caltech/target/c1iscex/losEtmx.o.13mar08
-rw-r--r-- 1 controls staff 229793 2007-03-08 11:09 /cvs/cds/caltech/target/c1iscey/losEtmy.o.13mar08
op440m:40m>ls -alt /cvs/cds/caltech/target/c0dcu1/*.o.12mar08
-rw-r--r-- 1 controls staff 60810 2004-09-08 08:47 /cvs/cds/caltech/target/c0dcu1/dcuDma.o.12mar08

375

Thu Mar 13 12:11:58 2008

aivanov

routing PEM -> ASS -> SUS_MCL

374

Thu Mar 13 03:07:19 2008

My first (and hopefully not last) week at the 40m lab is ending Frown

I found this lab really cool, the people working here really cool as well, and this e-log....
this e-log is not just cool, it is FANTASTIC!!!

LISA

373

Thu Mar 13 02:52:06 2008

Today we have tried to use the reflected signal demodulated at 3*f1 ~ 99 MHz (REFL31) for length control.
This signal is cool because it is generated by the beating of sidebands, so it is not very sensitive to what the carrier does inside the IFO.
In particular, its gain and the demodulation phase shouldn't change much while changing the CARM offset during the locking sequence.
The idea is therefore to use REFL31_I and REFL31_Q for controlling MICH and PRCL, with the goal of making the lock acquisition sequence more robust.

We minimized hardware changes by using the 199MHz demodulation board, changing the local oscillator to 99.586317 MHz, with an amplitude of +10 dbm (the 3f signals are therefore acquired as LSC-PD6_I and LSC-PD6-Q).

We locked both the PRM and the DRM in a stable way using the REFL31_I and REFL31_Q, after tuning the demodulation phase (50) and removing their offsets.
On the other hand, we weren't able to acquire the lock in the DRM configuration directly by using the 3f signals. We needed instead to use the f signals first, and switch to the 3f signals once the lock was already acquired, otherwise ending up locking DRM at a different working point.
One explanation for that might be the fact that the beam impinging upon the 3f diode is too big compared with the diode size (only 1 mm, half of the size of the f1 diode).
For these reason, in presence of misalignments, some of the reflected light goes in high order modes, which can be partially (or all) off the diode, thereby generating multi-zero crossing in the demodulated error signal.

The next step before making the test with the whole IFO is therefore to modify the telescope in front of the 3f diode in order to reduce the beam size and repeat the tests we did tonight in DRM configuration.

P.S.: We made a test by changing the frequency of the local oscillator by a little bit and then coming back to the original value. We observed that the phase of the signal can change, so every time this frequency is moved the 3f demod phase need to be retuned.

John, Rob, Rana, Lisa

372

Wed Mar 12 23:05:44 2008

they are bad, somewhat

please fix

371

Wed Mar 12 00:47:26 2008

And this is a cool snapshot showing how this operation used 16 cores on menkar !

370

Wed Mar 12 00:40:35 2008

Same as above but with 2048 taps and a 128 Hz sample rate. Does much better at the 16 Hz bounce mode.

369

Wed Mar 12 00:36:52 2008

I used the MISO FIR Wiener matlab code to see how well we might do in principle.

The attached 3 page PDF file shows the MC_L control signal (force on MC2) and the residual
after subtracting off the accelerometer and seismometer using a 32 Hz sample rate and
512 taps (page 1), 1024 taps (page 2), and 2048 taps (page 3). As Matt smarmily points out,
there's not a lot to win by going beyond 512; maybe a factor of sqrt(2) for a factor of 4
tap number.

368

Tue Mar 11 23:14:01 2008

Steve and Matt moved the accelerometers and seismometers today.
The accelerometers are now placed around the MC and the seismometer is in-between MC1 & MC2.

We have changed the names of the acc channels to reflect whether they are close to MC1/MC3
or MC2. We tested the accelerometer to channel name mapping by switching gains at the wilcoxon
breakout box and also by tapping. It seems now that the previous setup near the ITMX/ETMX had
some few channels mislabeled which would have given some confusing results.

Alex, Jay, and Rolf came over today and installed, then de-installed some of the hardware for
sending the PEM channels over to the C1ASS machine where the adaptive filter front end will go.
Everything should be back to the way it was...hopefully, the guys will modify the ADCU PEM
code to send the signals to the new FE over the reflective memory net and then send them to the
MCL inputs of the suspensions. So the first incarnation should use the accelerometers and seismometer
to drive MC1 and/or MC3.

367

Mon Mar 10 20:46:41 2008

I've placed a 10% reflector in the path from ETMY to the trans and quadrant photodiodes.

366

Mon Mar 10 02:05:08 2008

DRMI+2ARMs working better

Locking

Some encouraging progress on the locking front tonight. After the work on the DRM loops last week and a review of the settings for initial lock acquisition (loop gains, tickle amplitude, filter states, so on), the DRMI+2ARMS locking is working pretty well. That's to say, it takes from 5-15 minutes generally for the IFO to lock in the offset CARM state, with the arm powers at 0.5. It's then possible to raise the arm powers slightly, and handing off control of CARM to MCL works at low power, but engaging the AO path (using PO_DC as an error signal) is not working so well. Taking swept sines indicates that the PO_DC should be a good error signal. The next good thing to try might be just using PO_DC as an error signal for the length path, without using the AO path at all, to see if it's something in the hardware.

365

Fri Mar 7 19:04:39 2008

Green laser pointer was found in my desk.
I blamed Rana for not returning it to me after a conference talk.
It is surprisingly bright still.
I will bring sweets for Wednesday meeting.

364

Fri Mar 7 17:10:01 2008

Noise budget has been moved to the svn system. A checked out copy is in the directory caltech. From now on, I will try to use the work cycle as outlined in the svn manual. Changes made today include the following:
getNoiseBudget
/matlab/noise/NoiseBudget

Details of the modifications made may be found on the svn system. Please let me know if anyone has a suggestion or concern. Thank you - Max.

363

Fri Mar 7 00:47:54 2008

Yesterday evening around 7:30 PM, I changed the Ranger seismometer from a
vertical to a horizontal seismometer. To do this I followed the instructions
in the manual.

1) Lock it down.
2) Turn it sideways. Use the leveling screws to center the bubble level.
3) Carefully loosen the hanger rod and release slowly the tension to allow
   the mass to recenter.
4) Look through the little viewhole next to the rod to make the white lines
   line up. This means the mass is centered.
5) Look at the output on a scope. It should be freely moving with a ~1 sec.
   period.

The attached plot shows the before and after spectra.

362

Thu Mar 6 00:17:37 2008

Got the DD (double demod) handoff scripts working tonight, with just the DRMI. So, now acquisition with the single demod signals is working well, and handoffs to all double demod signals using the input matrix ramping worked several times with the scripts. Up next will be more work with the DRM+ARMs.

361

Wed Mar 5 17:35:24 2008

I used an ezcaservo command to adjust the offsets for Alberto's StochMon channels. They are all
at +2 V with no light on the RFAM PD (MC unlocked).

Then I looked at 5 minutes of second trend around when the MC locks. Since Alberto has chosen
to use +2V to indicate zero RF and a negative gain, there is a large RF signal when the StochMon
channels approach zero.

From the plot one can see that the RFAM for the 133 & 199 MHz channels is much worse than for the 33 and 166.
Its also clear that the turn on of the WFS (when the RFAMPD's DC light level goes up) makes the single demod
signals get better but the double demod get worse.

360

Wed Mar 5 12:51:48 2008

John

Summary

LSC

Initial 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.

359

Wed Mar 5 12:35:09 2008

John

Summary

Plot 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;

figure(1)
ha = axes('units','normalized','position',[0 0 1 1]);
uistack(ha,'bottom');
I=imread('PDbw.jpg');
hi = imagesc(I);
colormap gray
set(ha,'handlevisibility','off', ...
'visible','off')
plot(xdata,ydata,'r')
hold on
plot(xdata,fit,'k')
plot(xdata,phase_deg,'b')
hold off
ylabel('Phase/ degrees', 'FontSize',12)
xlabel('Frequency/ Hz', 'FontSize',12)
title('Removing the time delay','FontSize',16)
legend('data','fit','data-fit',0)
set(hi,'alphadata',.35)
set(gca,'Color','None')
box off

figure(2)
set(gcf,'Color', [1 1 1])
subplot(4,1,[1 3])

semilogx(f_Hz,mag_dB,'k','LineWidth',2.5)
title('Response of PD6','FontSize',16)
ylabel('Magnitude/ dB', 'FontSize',12)
xlim([xmin xmax])
grid

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),...
'FontSize',10,'FontWeight','Bold','HorizontalAlignment','right',...
'VerticalAlignment','top','BackgroundColor',[.7 .9 .7],...
'Margin',0.5, 'Rotation',90);
LabelExt = [LabelExt; get(a,'Extent')];
LabelPos = get(a,'Position');

end

% 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'))
end

subplot(4,1,4)
semilogx(f_Hz,phase_deg,'r','LineWidth',2.5)
xlim([xmin xmax])
ylabel('Phase/ degrees', 'FontSize',12)
xlabel('Frequency/ Hz', 'FontSize',16)
grid
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: ...
180])
set(gcf,'units','normalized','outerposition',[0 0 1 1]);

358

Tue Mar 4 23:22:32 2008

I found that some channels from c1susvme1 and c1susvme2 were not being recording by the DAQ (and were not showing up in DV). I rebooted these processors, which fix the problem. If you see other cases of this (signal exactly zero, but not a testpoint problem), just reboot the corresponding processor.

357

Tue Mar 4 20:14:02 2008

The MC alignment was pretty far off. We were getting TEM01 mode locks only.
Rather than inspect what happened I just aligned the MC suspensions to get
the transmission higher. Now Matt should be able to lock the X arm and collect
adaptive filter data.

356

Tue Mar 4 19:14:09 2008

Matt, Rob, Rana

Today we added the TDS software to the 40m SVN repo.

First we rationalized things by deleting all the old TDS directories and taking
the tds_mevans dir and making it be the main one (apps/linux/tds).

We also deleted all of the TDS directories in the project area. It is now very
likely that several scripts will not work. We're going to have the teething
problems of repointing everything to the nominal paths (in the apps areas).

Finally we did:

svn import tds https://40m.ligo.caltech.edu/svn/40m/tds --username rana

to stick it in. To check it out do:

svn checkout https://40m.ligo.caltech.edu/svn/40m/tds --username rana

We'll get a couple of the O'Reilly SVN books as well to supplement our verion control knowledge.
Unitl then you can use the SVN cheat sheets available at:

http://www.digilife.be/quickreferences/quickrefs.htm

355

Tue Mar 4 10:08:21 2008

green lights unreliable when c0daqctrl down

So far I've tried powering off the framebuilder, power-cycling the RAID (it was showing an error message about bad IDE channel #4), and rebooting the LSC (just for fun). When I reset the LSC, its green light on the RFM_NETWORK screen did not turn red, making all these lights suspect. The iscepics40m process is what controls these red/green lights, so maybe it's gone wonky. It appears to be running however, on c1dcuepics, and it also seems to be functioning correctly in other ways (it's communicating correctly with the LSC).

Update: Alex and Jay came by. The solution was to reset the c0daqctrl processor, which apparently was not done in Rana's rebooting spree. Or maybe it needed to be done last.

354

Tue Mar 4 00:42:51 2008

The framebuilder is still down. I tried restarting the daqd task and resetting the RFM
switch like it says in the Wiki but it still doesn't work right. The computer itself is
running (I can ssh to it) and the daqd process is running but there's a red light for
it on the RFM screen and dataviewer won't connect to it.

If Alex isn't over by ~10 AM, we should call him and ask for help.

353

Mon Mar 3 19:34:40 2008

Quote:

The CODAQ_RFNETWORK are down, except C1SUSVME & AWG

All of the FE machines were found to be down this afternoon. I called Alex and he suggested several
things which didn't work (restart EPICS tasks, power cycle RFM switch, etc.).

Then he suggested that I go around and power cycle every crate!!! And that sometimes the order of this
matters!!! I think he was just recording this conversation so that he could have a laugh by playing it on Youtube.

However, power cycling all of the FE crates seemed to work. Alex's theory is that 'something goes bad in the
RFM cards sometimes'.

Its all green now.

352

Mon Mar 3 13:58:10 2008

The CODAQ_RFNETWORK are down, except C1SUSVME & AWG

351

Mon Mar 3 09:25:33 2008

steve

rga scan logging is working now

VAC

Quote:

The rga head and controller are running fine, but the data logging is not.

It should run tonight at 1:25 AM. To get the cron job to work properly on op340m, I had to make wrapper sh script which defines the perl library before calling the actual RGAlogger script.

Thanks to Rob, it is working !

The baked, calibrated rga head
model# M206M, s/n #c128035 was reinstalled at the 40m ifo on Feb. 8, 2008
Faraday mode dwell time was increased from 2 to 16 sec
Rga head temp at top silver gaskit 45.2 C
The noise floor is at 1E-12 Torr

There is more detail in logbook VMI-14 p 107

pd65-m-d119

349

Sun Mar 2 23:43:45 2008

John's PD plotting script is superior to all of the ones we had before; lets make him post the script so we can all use it.

Looks like PD6 is not too happy after all; the 199 MHz response is not much higher than the 166 MHz response. I thought we were supposed to have them balanced to within 6 dB or so?

348

Fri Feb 29 13:51:17 2008

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

347

Thu Feb 28 19:49:21 2008

Quote:

With Ben, we hooked up the RF Monitor box into the PSL rack and created 4 EPICS channels for the outputs:

C1:IOO_RF_STOC_MON_33
C1:IOO_RF_STOC_MON_133
C1:IOO_RF_STOC_MON_166
C1:IOO_RF_STOC_MON_199

The power cable bringing +15V to the preamplifier on the PSL table should be replaced eventually.

I changed the names of these channels to the more appropriate (and informative, as they're coming from the RFAMPD):

C1:IOO-RFAMPD_33MHZ
C1:IOO-RFAMPD_133MHZ
C1:IOO-RFAMPD_166MHZ
C1:IOO-RFAMPD_199MHZ

I also added them in an aesthetically sound manner to the C1IOO_LockMC.adl screen and put them in trends. Along the way, I also lost whatever Alberto had done to make these monitors read zero when there's no light on the diode. It doesn't appear to be written down anywhere, and would have been lost with a reboot anyway. We'll need a more permanent & automatable solution for this.

346

Thu Feb 28 19:37:41 2008

multiple cameras running and seisBLRMS

Quote:

1) Mafalda is now connected via an orange Cat5E ethernet cord to the gigabit ethernet switch in rack in the office space. It has been labeled at both ends with "mafalda".

2) Both the GC650M camera (from MIT) and the GC750M are working. I can run the sampleviewer code and get images simultaneously. Unforutnately, the fps on both cameras seems to drop roughly in half (not an exact measurement) when displaying both simultaneously at full resolution.

3)Discovered the Gigabit ethernet card in Mafalda doesn't support jumbo packets (packets of up to 9k bytes), which is what they recommend for optimum speed.

4)However, connecting the cameras through only gigabit switches to Mafalda did seem to increase the data rate anyways, roughly by a factor of 2. (Used to take about 80 seconds to get 1000 frames saved, now takes roughly 40 seconds).

5)Need to determine the bottleneck on the cameras. It may be the ethernet card, although its possible to connect multiple gigabit cards to single computer (depending on the number of PCI slots it has). Given the ethernet cards are cheap ($300 for 20) compared to even a single camera (~$800-1500), it might be worth while outfitting a computer with multiple.

I found the SampleViewer running and displaying images from the two cameras. This kept mafalda's network so busy that the seisBLRMS program fell behind by a half-hour from its nominal delay (so 45 minutes instead of 12), and was probably getting steadily further behind. I killed the SampleViewer display on linux2, and seisBLRMS is catching up.

345

Thu Feb 28 16:19:37 2008

josephb

Mafalda rewired and multiple cameras running

344

Thu Feb 28 13:04:59 2008

rga logging working again

VAC

Quote:

The rga head and controller are running fine, but the data logging is not.

It should run tonight at 1:25 AM. To get the cron job to work properly on op340m, I had to make wrapper sh script which defines the perl library before calling the actual RGAlogger script.

343

Thu Feb 28 12:31:33 2008

Bureaucracy

MDV library does not work at "LINUX 2"

Quote:

While working on Thursday evening with Matlab scripts "dttfft2" and "get_data", I noticed that mDV library does not work at computer "LINUX 2" (the third computer in the control-room if you enter it from the restroom). There are multiple error messages if we try to run "hello_world", "dttfft2" or "get_data". In order to take data from accelerometers, I changed the computer - I was working from "LINUX 3" computer, the most right computer in the control room, but for the future someone should resolve the issue at "LINUX 2". I am not experienced enough to revive the correct work of mDV directory at "LINUX 2".

Andrey.

This turned out to be due to /frames not being mounted on linux2, as a result of a reboot. The issue is discussed in entry 270. I remounted the /frames, and added a line to mdv_config.m to check whether the frames are mounted.

342

Wed Feb 27 22:05:03 2008

A summary of the status of the auxiliary arm locking effort.

To help with lock acquisition we are attempting to independently lock the Y arm using light injected through ETMY. At present this secondary light source is an NPRO laser situated on the SP table. The laser light is transported to the ETM using a single mode optical fibre. In the future we might pick off some PSL light and apply a frequency shift.

We have been able to successfully mode match the fibre beam into the cavity and have been attempting lock the cavity using standard PDH signals (phase modulation sidebands are added to the light before it enters the fibre).

As yet no acceptable error signals have been produced. The demodulated RF signal is showing a time varying, bipolar dc offset.

We have minimised the residual amplitude modulation of the EOM but we expect small signals due to the undercoupled nature of the system, it could be that whatever RFAM still present is varying with time and causing this behaviour. We are also able to produce similar offsets by stressing (i.e. bending, shaking) the fibre. Could it be that the fibre is somehow converting PM into AM? Are we seeing etalon effects in the fibre or elsewhere?

If we cannot make any further progress with the existing setup we shall move the NPRO to the ETM table and try again. We are also looking into purchasing some other types of fibre.

Other things to consider are injecting through POY or using some other wavelength - neither seems obviously better.

Fiber, behavior

341

Tue Feb 26 20:24:04 2008

As for that plot of three-dimensional surface, I indeed was wrong with the axis "Q_ETMX-Q_ITMX" (I put there wrong string "Q_ITMX-Q_ETMX"). On Friday plot there were values 10^(-12) on the z-axis, and that should be really meters, but the point that as I realized on Monday, I have never calibrated experimental measurement results from counts to meters , that's why it is this difference between 10^(-6) and 10^(-12). I still did not find the way to compare experim. and theoretical plots, because even if I leave "counts" on both plots, so that I have scale 10^(-6) on both plots, then the change in theoretical plot is just 0.02*10^(-6) for the range of Q-factors change, while the change in experimental measurements is an order of magnitude more 0.4*10^(-6), so the surface for theretical plot would be almost flat in the same axes as experimental results.

340

Sun Feb 24 10:51:58 2008

Fri Feb 22 21:19:38 2008

Andrey

Bureaucracy

MDV library does not work at "LINUX 2"

338

Fri Feb 22 20:42:44 2008

Andrey

Summary

It seems I succeeded in theoretical simulations

I am pretty happy at this moment.

I definitely feel that it took me too much time to understand how to do the Matlab program and how to overcome difficulties,

but eventually at last my Matlab program seems to start working.

Briefly: What the program does?
--> take time-domain signal from two accelerometers near ITMX and ETMX (use 'get_data');
--> calculate the time-evolution of those two signals through the system "stack + pendulum" to the test-masses ITMX and ETMS (use 'lsim' in Matlab),
which gives us the time-domain evolution of the deviation of the position of individual test-mass from its average position.
--> Subtract the two results from each other in time-domain, this gives us the deviation of the length of the XARM-cavity from its average value
(roughly speaking, deviation of the length of the cavity from exactly 40 meters, although I am aware that the exact average length of XARM is less than 40 meters).
--> Take the amplitude spectrum of the result, using Sqrt(pwelch) and calibrate it from "counts" to "meters".
--> Calculate root-mean-square of peaks at different frequency intervals, for example near 0.8Hz,
and plot the three-dimensional surface showing the dependence of RMS on Q-factors Q_{ETMX} and Q_{ITMX}.

Eventually I am able to create these dependences of RMS.

I see that the minimum of the dependence is close to the diagonal corresponding to exact equality of Q_ETMX} and Q_{ITMX}, but not exactly along the diagonal. The plot allows to say
which of two conditions "Q_I > Q_E" or "Q_E < Q_I" should be fullfilled for optimization reasons. My plot is raw, I might have made a mistake in axis-label, I do not garantee now that the axis label "Q_ITMX - Q_ETMX" is correct,
maybe I need to change it for "Q_ETMX - Q_ITMX". I need some more time to determine this on Monday, but clearly there is asymmetry between Q_I and Q_E.

The peak at 0.8 Hz is pretty stable, while the peak at around 3Hz is not very repeatable, therefore in both experimental measurements and these simulations the amplitude of RMS of peak at 3Hz) is several orders of magnitude smaller than for RMS of peak at 0.8Hz, and I do not see minimum somewhere in the RMS-dependence, I see now only steady growth of RMS as Q_factors increase.

I will need to spend some time on Monday trying to understand how the sampling frequency and number of fft-points influence my results when I take amplitude spectrum using pwelch-command, as well I will need to double-check the correctness of normalization from counts to meters (I am not confident right now that amplitude of order of 10^(-12) meters is correct).

So, I need some time after the weekend to analyze my results and maybe make some slight changes, but I am glad that my Matlab model started to work in principle. I wanted to let others know about the status of the progress in my work. The fact that Matlab program works now is a good ending of a week.

Andrey.

337

Fri Feb 22 16:47:54 2008

Well I guess Rana didn't study too hard at Professor School, either. If he'd even bothered to actually read John's entry, he might have looked at the RF Out from the HP Analyzer. As it is, this experience so far has been like taking your car to a highly respected mechanic, telling him it's having acceleration problems, and then he takes a rag and wipes some dirt off the hood and then tells you "It's running fine. That'll be 500 bucks."

I make the current score:

Snarkiness: 2
Education:  0

I did RTFM, and it doesn't mention anything about crazy behaviour on the RF Output. So, I set up the analyzer to do a sweep from 500MHz to 1MHz, with output power of 0dBm, and plugged the output directly into the 300MHz scope with the input set to 50 Ohm impedance. The swept sine output looks totally normal from 500Mhz to 150MHz (measuring ~220mVrms below 300MHz -- 0dBm), where it abruptly transitions to a distorted waveform which the scope measures as having a frequency of ~25MHz and with 450mVrms (+6dBm). It then transitions again at some other part of the sweep to a cleaner-looking 25MHz waveform with ~1.2Vrms (+15dBm). See the attached Quicktime movie. The screeching in the background is the PSL door.

With this bizarre behaviour, it's actually possible that even someone who does everything carefully and correctly could break sensitive electronics with this machine. Let's get it fixed or get a new one.

Don't use the HP4195A anymore unless you want broken electronics.

Quote:

I'm not sure where Ward and Miller went to Analyzer school, but it was probably uncredited.
I turned it on and used 2 BNC cables and a T to hook up the source to the 2 inputs and measured the always-exciting TF of cable.

Score:  HP Analyzer  1
        Rob & John   0

I have left the analyzer on in this complicated configuration. RTFM boys.

Quote:

The HP 4195A network analyser may be broken, measurements below 150MHz are not reliable. Above 150MHz everything looks normal. This may be caused by a problem with its output (the one you'd use as an excitation) which is varying in amplitude in a strange way.

Analyzer

336

Fri Feb 22 15:16:33 2008

Andrey