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ID Date Authorup Type Category Subject
  290   Fri Feb 1 10:43:05 2008 JohnUpdateEnvironmentConstruction work
The boys next door have some bigger noisier toys.
Attachment 1: DSC_0433.JPG
DSC_0433.JPG
  293   Fri Feb 1 17:17:05 2008 JohnSummaryPSLMach-Zender tweaking
I helped Rob adjust the alignment of the Mach-Zender to try and reduce any AM on the laser light. Our goal was to reduce the large offsets in the DD signals.

We reduced the MZ refl from 0.54 to 0.39. We were able to re-lock the mode cleaner without problems. We then centred the WFS heads.

No change in the DD signal offsets.
  294   Sat Feb 2 14:11:27 2008 JohnSummaryComputersOPTLEVmaster screen
I changed the layout of the optlev master screen. The old version is /cvs/cds/caltech/medm/old/C1ASC_OPTLEVmaster080202.adl
  296   Mon Feb 4 22:01:57 2008 JohnSummaryLSCFibres auxiliary locking - Fibers
I managed to couple ~75% of the light transmitted from the y arm, through the fibre, back to the SP table. I hoped that this would be a good way to match the beam from the fibre into the arm. Still no flashes. It looks like the cameras just aren't sensitive enough.
  304   Sat Feb 9 13:05:48 2008 JohnSummaryIOOPMC camera/ HEPA
I replaced the Gig-E camera on the PMC trans beam. The PZT was close to railing and I wanted to adjust it. I just did a quick job, there is a little scattered light on the image. If Joe is finished with the Gig-E I'll take another look at it.

The HEPA in the PSL table was turned off for some reason. I turned it back on.
  305   Sat Feb 9 13:32:07 2008 JohnSummarySUSAll watchdogs tripped
When I arrived this afternoon the watchdogs had tripped on all optics. I reset them and enabled the coil currents.

I had to adjust the alignment of the mode cleaner to get it to lock.
  315   Wed Feb 13 20:37:11 2008 JohnUpdateLSCFibre locking - Fiber
Sam and I observed fringes in the light reflected from the Y arm. These fringes are due to the sidebands and not the carrier. To improve matters we plan to reduce the RF AM and increase our modulation index.
  324   Tue Feb 19 18:28:41 2008 JohnUpdatePEMMore seismic in Baja California
Steve spotted more activity from the same quake.

Reset watchdog on ETMY.
  328   Thu Feb 21 18:29:28 2008 JohnSummaryGeneralHP Network Analyser Analyzer
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
  342   Wed Feb 27 22:05:03 2008 JohnUpdateLSCAuxiliary locking
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
  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;

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]);
Attachment 3: PDbw.jpg
PDbw.jpg
  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.
Attachment 1: FofLambdaLIGOI.jpg
FofLambdaLIGOI.jpg
  367   Mon Mar 10 20:46:41 2008 JohnConfigurationLSCETMY Trans PD & QPD
I've placed a 10% reflector in the path from ETMY to the trans and quadrant photodiodes.
  377   Thu Mar 13 18:20:29 2008 JohnUpdateGeneralNew Focus 4003 EOM 29.489MHz
I measured the modulation index as a function of drive power using an OSA. Agrees well with spec of 0.2 rad/V.
  396   Sun Mar 23 00:56:42 2008 JohnUpdateLSCMore on 3f
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.
  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.
  402   Tue Mar 25 15:56:09 2008 JohnUpdateTreasureAssorted pictures
Some pictures scavenged from the D40.
Attachment 1: D40.pdf
D40.pdf D40.pdf
  405   Wed Mar 26 22:26:15 2008 JohnUpdateComputersc1susvme
I removed the fan and tweaked the timing cables to see if they were the source of our problems. I saw no effect. I'm leaving the fan off for the moment to see if that helps. It is on top of the filing cabinet next to my desk.
  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.
  536   Tue Jun 17 22:00:53 2008 JohnHowToPSLProblems turning MZ servo on/off
We were unable to toggle the MZ servo on/off (Blank/Normal) from MEDM. Pushing on the Xycom board and cables changed the fault from constant to intermittent. At least one lock loss has been caused by a MZ glitch.
  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.
Attachment 1: mcl080623.png
mcl080623.png
  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.
Attachment 1: MC2noise080623.png
MC2noise080623.png
  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
Idea:

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

Reasoning:

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.

Conclusion:


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.
Attachment 1: gettingcloser.png
gettingcloser.png
  586   Fri Jun 27 19:59:44 2008 JohnUpdateComputersc1iovme
C1susvme2 and C1iovme crashed which sent the optics swinging and tripped the watchdogs.

Koji and I were able to restore c1susvme2 without any trouble.

We have been unable to revive c1iovme. We have tried telneting in and running startup.cmd,
the process runs for a while then hangs with "DAQ init failed -- exiting".

Resetting the board doesn't help. I didn't try keying the whole crate.

All optics are back to normal with damping restored.
  588   Sat Jun 28 14:56:44 2008 JohnUpdateComputersini files
In short, I was editing the ini files yesterday evening, I didn't e-log it and after some investigation this afternoon it apears
that I am to blame for all the computer problems which followed.


I wanted to edit C0EDCU.ini and C1IOOF.ini to change C1: PSL-FSS_FAST to a fast channel as C1: PSL-FSS_FAST_F
was dead.

I opened these files and made backups. It appears this is where it all went awry. My backup for C1IOOF
is called C1IOO.ini.090627 i.e. missing the F.

Later c1susvme2 and c1iovme crashed. After failing to bring c1iovme back I wondered if my edits had
caused the problems so I restored the back up files. It appears that here I wrote over C1IOO with my backup of
C1IOOF (presumably because I had made a typo in the name).

To remedy the situation we could restore C1IOO from e.g. chans/archive/C1IOO_080618_160028.ini

No excuses for not e-logging this activity.
  589   Sat Jun 28 23:23:50 2008 JohnUpdateComputersRebooting
All of the computers are now showing green lights.

Remaining problems:

Alignment scripts are failing with "ERROR: LDS - NDS server error #13"
I think this is a server transmission error.

Dataviwer shows all channels as zero.
  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.
  595   Sun Jun 29 19:53:26 2008 JohnSummaryPSLISS

Quote:
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.
Attachment 1: mcscreen.png
mcscreen.png
Attachment 2: ifostate.png
ifostate.png
  598   Mon Jun 30 01:49:06 2008 JohnUpdateIOOMC work
I'm in the process of aligning the mode cleaner/ input beam.

I turned off the WFS and cleared their histories, adjusted the input periscope and re-aligned the mode-cleaner accordingly.
I then unlocked the cavity and centred the beams on the WFS.

MC transmission is ~3.3 and the REFL beam looks a little better.

However, turning the WFS on now lowers the transmission. More thought tomorrow.

I'm leaving the MC locked with WFS off.
  601   Mon Jun 30 09:46:15 2008 JohnUpdateIOOMC WFS
MC WFS are on. They seem to do some good during the day.
  604   Mon Jun 30 15:08:52 2008 JohnSummaryPSLMZ alignment
I adjusted the alignmnet of the Mach-Zehnder's two North mirrors (downstream of the EOMs).

MZ REFL is reduced from 0.54 to 0.43. The largest improvement was due to pitch on the PZT mirror.
Attachment 1: mzalign.png
mzalign.png
  613   Tue Jul 1 12:51:34 2008 JohnSummaryGeneralIFO alignment
Rana, Rob, Yoichi, John

The recent computer problems and MZ work had disturbed the alignment of the interferometer.

We adjusted the MC alignment back to nominal positions using old OSEM values. We then walked
the input beam to match the MC. Coupling into the interferometer has increased noticeably.
The rest of the IFO was then aligned to the new input beam.

Proceeding to full IFO locking we were able to engage the AO path and hand off CARM to SPOBDC.
Arm powers got up to 4.

If the new alignment proves successful we will centre all QPDs etc so we can easily return to
this state.
Attachment 1: align080701.png
align080701.png
  618   Tue Jul 1 21:45:48 2008 JohnUpdatePSLMach Zehnder script and screen
I've edited C1: PSL_MACH_ZEHNDER.adl and /cvs/cds/caltech/scripts/PSL/MZ/lockMZ
to reflect the changes described in entry #616.
  625   Wed Jul 2 17:19:03 2008 JohnSummaryComputersop440m - shutdown and restarted
After 160days op440m was getting a little slow.
  626   Wed Jul 2 18:30:01 2008 JohnUpdateIOOQPD alignment
I aligned the beams on the following QPDs

IP POS
IP ANG
MC TRANS
IOO POS
Attachment 1: IOO080702.png
IOO080702.png
Attachment 2: MC080702.png
MC080702.png
  633   Thu Jul 3 16:57:23 2008 JohnSummaryGeneralFSS_RMTEMP
The FSS room temp alarm has been beeping a lot recently. I altered the FSS_RMTEMP alarm levels using the
same method as Rana.

The alarm is still souding so, at least by my calculations, it must be colder than usual.
Attachment 1: FSStime.png
FSStime.png
Attachment 2: FSSalarm.png
FSSalarm.png
  644   Tue Jul 8 00:14:28 2008 JohnSummaryComputersAlarm handler
Rob thought it would be nice to have some alarms on the cpu loads and FE syncs.
I added all these channels to the alarm handler config file and wrote a script
which would set their values (HIHI,HIGH etc).

Ezcawrite allowed me to set the alarm levels (and ezcaread would give the correct
value) but no matter what I set the value to the alarm wouldn't sound.

After experimenting with a few other channels it appears that the alarm handler will
not show alarms if the alarm levels are absent from the db file (even though ezca
gives a value).

I edited the following files so we can have alarms on the cpus.

In c1iscepics:
lsc40m.db
asc40m1.db

In c1losepics:
bs.db
etmx.db
etmy.db
itmx.db
itmy.db
mc1.db
mc2.db
mc3.db
prm.db
srm.db

I saved backups in the appropriate folders.

Next time we have a bootfest please also do c1iscepics and c1losepics so these changes
will be implemented.
  648   Tue Jul 8 12:25:54 2008 JohnSummaryPSLISS gain set to 2dB
  651   Wed Jul 9 12:42:14 2008 JohnUpdateLockingHand off to RF CARM
Rob, Yoichi, John

Last night we were able to reduce the CARM offset to around 80. This was achieved by increasing the DARM gain and
switching to AS_I when AS_Q went bad. This is probably a temporary solution, we will probably switch to DC readout
for DARM as we bring the arms on resonance.

Having reduced the arm offset enough to get us into the linear region of the RF_CARM signal (POX_I) we worked on
analogue conditioning of this signal to allow us to hand over. Lock was maintained for over 20 minutes as we did
this work.

We were able to partially switch over both the frequency and length paths to this new signal before losing lock.
Attachment 1: LongLock080709.png
LongLock080709.png
  653   Wed Jul 9 17:58:19 2008 JohnSummaryGeneralIlluminator alarms
This morning some time was wasted on alignment due to the illuminators.

I added the illuminators to the alarm handler. They will give a RED alarm whenever
they are turned on. You can find the alarms in 40M->Misc->Illuminators.

To do this I edited the Illuminators.db file and restarted c1aux by telneting and typing Ctl-X.
I then added the groups and channels to 40M.alhConfig.
  657   Thu Jul 10 23:27:57 2008 JohnMetaphysicsCamerasSecret handshakes
Rob and I have joined the ranks of the illuminati and exercised our power.


Quote:
Osamu showed me the secret way to change the video labels for the quads and
so we fixed them. He made me swear not to divulge this art.

- Rana Adhikari
  664   Sun Jul 13 22:39:16 2008 JohnSummaryGeneralEdited medm screens
I've edited the FSS and PMC screens so that red boxes are shown around the appropriate slider if a gain or offset is not within the limits defined in C1PSL_SETTINGS_SET.adl

With the current setting of 0 V the FSS input offset is red. According to the settings screen the nominal value is 0.3 +/- 0.050. Are there any objections to editing the nominal value?

I changed the LockMC screen so that red boxes are not shown when the up/down scripts are not running; when they are active you should see a green box.
  665   Mon Jul 14 00:36:19 2008 JohnSummaryPSLSlow sweep of laser temp - PMC PZT response
John, Rana

Follow up to # 663

Top trace: C1: PSL-PMC_PZT
Middle: C1: PSL-FSS_SLOWDC
Bottom: C1: PSL-PMC_PMCTRANSPD

The only calibration I could find for the PMC PZT (LLO e-log Sep 3 2003 - 23 MHz/V) predicts 31V for an FSR. I did a rough calibration and got our FSR to be around 210 V. I assumed 713 MHz for an FSR and applied this calibration (~3.4 MHz/ V) to the PZT data.

In terms of volts per metre our PZT gives 2.54 nm/ V whereas the LLO PZT is 17.16 nm/ V.
Attachment 1: SlowTsweep.png
SlowTsweep.png
  667   Mon Jul 14 12:43:07 2008 JohnSummaryComputersRestarted fb40m, tpman and c1ass
  675   Tue Jul 15 12:44:08 2008 JohnSummaryLockingDRFPMI with DC readout
Rob, John

Last night, despite suspect alignment, we were again able to reduce the CARM offset to zero using
the RF signal.We were also able to transfer to dc readout taking calibrated spectra in both states.
DC readout shows a marked improvement over RF above ~1kHz but introduces some noise around 100Hz.
Broadband sensitivity appears to be more than ten times worse than previously. The calibration
being used remains to be confirmed.

Engaging the ETMY dewhitening caused lock to be lost. We'll check this today. The OMC alignment loops
may also need some attention.

We looked at REFL_166 as a candidate for CARM, at present POX still looks better.

The DARM filters were modified to reduce excess noise around 3Hz. Updating filter coefficients does
not cause loss of lock.
  684   Wed Jul 16 17:36:51 2008 JohnDAQPSLFSS input offset
I changed the nominal FSS input offset to 0 from 0.3. Tolerance remains unchanged at +/-0.05.
ELOG V3.1.3-