ELOG 40m

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]);

360

Wed Mar 5 12:51:48 2008

John

Initial Ligo Arm finesse versus lambda

LSC

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.

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.

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.

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.

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.

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.

366

Mon Mar 10 02:05:08 2008

rob

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.

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.

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.

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.

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.

371

Wed Mar 12 00:47:26 2008

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

372

Wed Mar 12 23:05:44 2008

they are bad, somewhat

please fix

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

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

375

Thu Mar 13 12:11:58 2008

aivanov

routing PEM -> ASS -> SUS_MCL

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

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

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.

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.

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.

380

Fri Mar 14 15:06:24 2008

rob

routing PEM -> ASS -> SUS_MCL

Quote:

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

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.

382

Fri Mar 14 16:56:03 2008

Dmass

Bureaucracy

Computers

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?)

383

Sun Mar 16 17:03:32 2008

I've updated the ass.mdl file in the directory:

/cvs/cds/caltech/users/alex/cds/advLigo/src/epics/simLink/

to get us started in the adaptive PEM noise subtraction.

After several iterations of remote help from Alex, the code compiles and runs, receives signals from the LSC, PEM, and MC2, and communicates with the suspension controllers. I've also adapted the .par file from the code generator, but haven't got the testpoints working with the new ASS code. There are no MEDM screens yet, and Matt's adaptive filter code has not been installed (there's a matrix as a placeholder).

Putting in the adaptive code should be simple, building the MEDM screens tedious, and getting the testpoints working uncertain. I noticed that the new testpoint.par file starts at a different channel number than the previous (working) version, which is strange. I probably have a script somewhere to change all these numbers by a constant offset, but I don't know if that's the actual problem--maybe stuff just needs to be rebooted.

The code receives as input the first 24 channels from the PEM ADCU, the eight suspension control signals from the LSC, and the output of the MCL filter from MC2. It outputs to the MCL filter input of each suspension (except MC2).

384

Mon Mar 17 18:30:48 2008

It seems that adaptive filtering can achieve results similar to those of the MISO FIR Wiener (entry 369). The adaptive code simulates real-time operation, but uses the same data used by Rana for the Wiener filter. I ran the adaptive filter over the data 100 times to ensure that it was well trained... maybe too well.

385

Thu Mar 20 15:28:20 2008

steve

VAC

tp2 's drypump replaced

The fore pump of tp2 was replaced at fore line pressure 998m Torr

386

Thu Mar 20 16:06:27 2008

I changed the LSC code again. I noticed that when turning off the LSC (e.g., going from LA to OFF), the cpu time would jump from ~50 to ~80, and irrevocably de-sync all the SUS controllers. This was because turning off the LSC would suddenly zero the inputs to the decimation filters that send information to the ASS box, which for some reason greatly increases the computation time of the iir filter function call. I changed the code so that these inputs are never zeroed. The ASS receives inputs from the LSC all the time now.

I also noticed that the ASS machine was running in ~2400 usec. Yes, 2,400 microseconds. I don't know how long it's been doing that, but I restarted it. Immediately after restart, it ran at 1700 microseconds. After using the "RESET" field in the adaptOnline code, that dropped to ~100 usec. Now it's not doing any adaptive filtering, as I don't know what the good settings are and no-one has been elogging their IFO work the last few days.

387

Thu Mar 20 17:45:36 2008

Adaptive Filtering in the ASS system

ASS

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.

388

Fri Mar 21 09:02:03 2008

Small turbo #2 is the forepump of the maglev.
It failed last night, shut down the maglev and interlock closed V1
Ifo pressure is 20 mTorr now. The Yarm was still locked at 8am this morning.
The PSL beam to MC was blocked just before the output periscope.
The psl mechanial shutter did not work from epic screen.

389

Fri Mar 21 11:54:38 2008

Quote:

The PSL mechanical shutter actually did trip last night, greatly confusing me and Rana. Not realizing that the software vacuum interlock had tripped, we manually re-opened the shutter. I'll modify the relevant MEDM screens to indicate when the EPICS interlock trips.

390

Fri Mar 21 17:01:21 2008

Locale change on Mafalda & seisBLRMS restart

DMF

Ever since we moved the accelerometers to be around the MC and changed their names, the seisBLRMS
has not been working. I tried to restart it today after fixing the channel names in the par file
but I ran into a PERL / UBUNTU bug.

perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
        LANGUAGE = (unset),
        LC_ALL = (unset),
        LC_TIME = "en_US.ISO8859-1",
        LC_MONETARY = "en_US.ISO8859-1",
        LC_CTYPE = "en_US.ISO8859-1",
        LC_COLLATE = "en_US.ISO8859-1",
        LC_MESSAGES = "C",
        LC_NUMERIC = "en_US.ISO8859-1",
        LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").

I don't know how this crept up or when it started. There were a bunch of fixes on the Ubuntu
forums which didn't work.

In the end I just set the 'unset' environment variables via our cshrc.40m file and this seemed
to make ligotools/perl happy. Lets hope this lasts...I love Linux.

391

Fri Mar 21 23:15:11 2008

Ranger SS-1: New Setup

The Ranger seismometer has been in a bad state. Its output had been sent into a SR560 without any termination.

The seismometer is, internally, just a mass on a flexure with a magnet and a pickup coil for readout.
The damping of the system depends on the resistor hooked up across the coil. With the SR560 this is
the 1 Meg input impedance of it and so the mass is undamped.

I installed a 4300 Ohm resistor in there which seems to nearly critically damp it. However, this will not
allow us to reach the ultimate quantum noise limited performance. We will have to analyze the thermal, voltage,
and current noise to get that.

I then also increased the gain from 10 to 100 on the SR560. This should now make the front end noise of the
seismometer/SR560 close to equal to the noise of the PEM ADC.

392

Fri Mar 21 23:17:47 2008

I updated the seisBLRMS par file with the new channel names of the accelerometers and the seismometer and then
recompiled the code and restarted it according to Rob's elog entry. It went fine and the seisBLRMS is now back in
action.

394

Sat Mar 22 22:39:02 2008

mevans

Direct Form 2 filters are bad

CDS

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.)

395

Sun Mar 23 00:43:08 2008

mevans

HowTo

General

Online Adaptive Filtering

I wrote a short document about the OAF running on the ASS. Since there is no BURT setup, I put a script in /cvs/cds/caltech/scripts to help with setting initial parameters: upass.

396

Sun Mar 23 00:56:42 2008

We ended our last attempt at 3f locking concerned about the beam size on PD6. I investigated tonight. The beam was not obviously overfilling the diode and a quick tweak of the steering mirror revealed a decent plateaux. Nevertheless we decided to try a different approach to see if we found the same problems as before on a different diode.

This time our 3f diode was Refl 33. I put a splitter on the output of the diode at the LSC rack sending one half into the usual refl 33 board, the other into refl DD 199 (which is demodulating at 99Mhz).

I got as far as handing off PRC to the 3f signal in lock. More work needed.

397

Sun Mar 23 10:42:54 2008

Valera

RFAM of the RF stabilization box is measured

Electronics

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

398

Mon Mar 24 13:03:54 2008

Quote:

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).

The HP4195A is back from repair. At first, it exhibited exactly the same behaviour for which it was sent in for repair, and which is described above (pillage from entry 337). After speaking with the repair tech on the phone, who tried to imply that the digital scope was tricking us, I plugged the output into our HP8591E spectrum analyzer, just to have firm ammunition to combat the repair guy's looniness. This led to even weirder behaviour, like no output and overload signals on the inputs (with nothing connected). After turning the unit on and off several times, and firmly seating (and screwing in) the DB9 connectors in the back of the unit, it appears to be working properly. Except for a brief glitch as it passes through 150MHz, the swept sine signal now appears normal, both on the scope and in the spectrum analyzer.

Apparently the whole thing is due to a loose connection somewhere in the box, which wasn't actually fixed by the repair, but has at least been temporarily fixed by me stumbling around with a screwdriver and then pushing the power button a couple of times.

399

Mon Mar 24 20:15:03 2008

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.

400

Tue Mar 25 10:44:24 2008

Quote:

I rebooted it again this morning. The ASS machine is currently not running its process, for whatever reason (someone turn it off?). Let's leave it like this for a day and see how the c1susvme2 does. The other recent change is Steve's install of a cooling fan--maybe that's causing the problem.

401

Tue Mar 25 13:21:25 2008

Andrey