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ID Datedown Author Type Category Subject
  679   Wed Jul 16 11:00:15 2008 MashaUpdateAuxiliary lockingimproving ADC input for the mach zehnder setup and completely unrelated happenings
For most of last week, the SURFs + Jenne were helping Mike and Ken with "stray light control for
Enhanced LIGO", i.e. cleaning and baking many many baffles which will catch scattered light in the
interferometer.

Otherwise, the two channels of the Mach Zehnder which will be used to measure fibre noise were
balanced, which should reduce the effect of laser amplitude noise in phase noise detection. I have
set up two digital channels to collect time series data from the two photodiodes and took some
preliminary noise measurements. I will be using Matlab to combine the signals as to directly measure
the phase noise, and I wrote some Matlab code to speed up this process: loading the files,
manipulating time series data, and converting into frequency domain. Currently I am building a
filter that will attenuate the signal at frequencies below 1Hz and amplify at higher frequencies in
order to whiten the spectra and reduce ADC noise.
  678   Wed Jul 16 10:50:55 2008 EricSummaryCamerasWeekly Summary
Finished unwrapping, cleaning, baking, wrapping, wrapping again, packing, and shipping the baffles.

Attempted to set up the Snap software so that it could talk directly to EPICS channels. This is not currently working due to a series of very strange bugs in compiling and linking the channel access libraries. Alex Ivanov directed Joe and me to a script and makefile that are similar to what we're trying to do and it may solve our problem, but at the moment this still doesn't work. We're currently using a workaround that involves making unix system calls to ezca command line tools, but this is too hacky to leave in the final program.

Attempted to fit Josh's PZT voltage vs power plot of the OMC (from about a year ago) to lorentzians in order to try to develop fitting tools for more recent data. This isn't working, due to systematic error distorting the shapes of the peaks. Good fits can be obtained by cutting the number of points to a very small number around the peak of resonance, but this leads to such a small percentage of the peak being used that I don't trust these results either. (In the graph (shows the very top of the tallest peak): blue is Josh's original data, green is a fit to this peak using the top 66% of the peak and arbitrary, equal values for the error on each point, red is Josh's data averaged over bins of size 0.005, teal is a fit to these bins where the error on each point is the standard deviation of each bin, and magenta is a fit to these same bins, except cropped to the top ~10% of the peak, x-axis is voltage, y-axis is transmission power). Rana suggested that I take my own sweeps of the PMC using scripts that are already written: I'm currently figuring out where these scripts are and how to use them without accidently breaking something.

We've begun running the Snap software for long periods of time to see how stable it is. Currently, its only problem appears to be that it memory leaks somewhat: it was up 78% memory usage after a little over an hour. It doesn't put much strain on the computer, using only ~20% CPU. Stress put on the network from the constant transfer of images from the camera to the computer is not yet known.
  677   Wed Jul 16 09:27:17 2008 steveUpdateALARMPSL-FSS_RMTEMP alarm is false
Morning alarm sound is good for people who does not drink coffee.
Our 40m alarm is on every morning.
Those whom are not here in the morning thinks that this beeping sound is inspirational.
Would someone change this sound into less punishing form, like mockingbird chirp....

The C1PSL_SETTINGS.adl (40mm PSL Settings ) indicating that
C1:PSL-FSS_INOFFSET (Input Offset Adjust ) should be 0.3 +-0.05 V (red warning tag )

Alarm Handler: 40M pointing to yellow grade warning of PSL-FSS_RMTEM
This is a false alarm.

Two years trend of these channels are here:
  676   Tue Jul 15 19:15:57 2008 ranaSummarySUSETMX Dewhitening characterization
Since the boys found that the ETM dewhitening transient was kicking the IFO out of lock we
decided to investigate.

First, we wrote a script to diagnose and then tune the DC gain of the dewhitening filters'
digital compensation filter (a.k.a. FM9 or SimDW). It is in the scripts/SUS/ directory
and is called dwgaintuner. It puts in an offset on each coil's DAC channel and
then reads back the Vmon on the coil driver with the DWF on and off. It reports the ratio of these
voltages which you can then type into the FM9/SimDW filter's gain field. We learned that the
difference between the analog DWF path and the bypass path was ~3% (which is consistent with
what you expect from the use of 1% resistors). We need to repeat this for all of the rest of
the suspended optics except for MC1 and MC3.

This Vmon method is better than what's used at the sites so we will export this new technology.

The attached plot shows some switching transients with only the local damping on:
BLUE:   Output of filter bank during an FM9 turn off. This is the transient which goes to the DAC.
        The transients are mostly of the same magnitude as this.
RED:    This is the input of the filter module during another such transient.
GREEN:  Tried another switch; this time I filtered the time series in DTT by typing the SimDW into
        the Triggered Time Series filter field. This should be simulating what comes out of the
        output of the DW board - to convert to volts multiply by 15/32768.
PURPLE: Same kind of filtering as the GREEN, but with also a double 30 Hz highpass to remove the low
        frequency damping control signals. You can see that the total transient is only ~5 counts
        or ~1 mV at the coil driver output. This is comparable to the relative offset in the bypass
        and filter paths.
  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.
  674   Tue Jul 15 12:23:22 2008 JenneUpdateGeneralMC2 Watchdog tripped
Alberto, Jenne

Mode Cleaner was unlocked. We checked, and found that MC2's watchdog was tripped. It didn't look like anything bad was going on, so we turned the optic back on, and tried to relock the MC. It looks like the Mode Cleaner is now locked, but the lock bit on the LockMC screen is still red. I don't know what's up.
  673   Tue Jul 15 11:47:56 2008 JenneDAQPEMAccelerometer channels in ASS Adapt MEDM screen
Jenne, Sharon

We have traced which accelerometers correspond to which channels in the C1ASS_TOP MEDM screen.

Accelerometer Channel
------------- --------------------------
MC1-X C1:ASS-TOP_PEM_2_ADAPT_IN1
MC1-Y C1:ASS-TOP_PEM_3_ADAPT_IN1
MC1-Z C1:ASS-TOP_PEM_4_ADAPT_IN1
MC2-X C1:ASS-TOP_PEM_5_ADAPT_IN1
MC2-Y C1:ASS-TOP_PEM_6_ADAPT_IN1
MC2-Z C1:ASS-TOP_PEM_7_ADAPT_IN1

SEISMOMETER C1:ASS-TOP_PEM_1_ADAPT_IN1
  672   Tue Jul 15 10:24:57 2008 steveUpdatePSLPMC temp & pzt voltage
The PMC pzt HV was happy with no HEPA temp stability.
Can we thermally insulate the pmc ?
  671   Tue Jul 15 10:09:42 2008 EricDAQCamerasDid anyone kill the picture taking process on Mafalda?
Did anyone kill the process on Mafalda that was taking pictures of the end mirror of the x-arm last Friday? I need to know whether or not it crashed of its own accord.
  670   Tue Jul 15 09:47:09 2008 steveUpdatePEMlab temps and particles
All air condtion units were serviced last Friday.
AC filters are trying to control our particle counts but they have no capacity to match bad Pasadena conditions.
IFO room filters at CES were really clean.
Air make up filters inside and outside were dirty.
They showed the construction effect.
Control room and clean assembly units needed all filters replaced.

Note: the PSL-FSS_RCTEMP droped o.1C when enclouser HEPAs were turned back on
The RC temp controller should be better than that!
  669   Mon Jul 14 21:34:10 2008 AlbertoUpdateGeneralabs cavity length measurement experiment

Quote:
Lately I've been dealing with the alignment of the interferometer to have a good beam spot at the AS port. Today the alignment script kept failing because of computer problems (failure of the frame builder) and also because the IFO was probably too far from the range where the automatic alignment works.

An other problem I keep having with the alignment of the optics on the AP table is with multiple reflection beams of the NPRO beam at the Farady.
Although I believe that now the two beams are quite well aligned, I don't see any reflection of the secondary beam from the IFO anymore.

It's like the more I try to improve the alignment, the worse I get from the beam matching. I'll keep working on this.


Realigning the OSA I also had to move a little bit the mirror that reflects the IFO beam of at the AS port in order to raise the beam height. This had the effect of changing the position of the AS spot on the camera and on the monitors.

Tonight with John, we made sure that the AS beam was still aligned to the PD.
  668   Mon Jul 14 19:15:43 2008 AlbertoUpdateGeneralabs cavity length measurement experiment
Lately I've been dealing with the alignment of the interferometer to have a good beam spot at the AS port. Today the alignment script kept failing because of computer problems (failure of the frame builder) and also because the IFO was probably too far from the range where the automatic alignment works.

An other problem I keep having with the alignment of the optics on the AP table is with multiple reflection beams of the NPRO beam at the Farady.
Although I believe that now the two beams are quite well aligned, I don't see any reflection of the secondary beam from the IFO anymore.

It's like the more I try to improve the alignment, the worse I get from the beam matching. I'll keep working on this.
  667   Mon Jul 14 12:43:07 2008 JohnSummaryComputersRestarted fb40m, tpman and c1ass
  666   Mon Jul 14 10:57:00 2008 KojiFrogsEnvironmentSomeone at 40M sent LHO water of life
Someone at the 40m sent Mike@LHO a pound of peets coffee with the name of Koji Arai.
It was a good surprise! Thanks, we will enjoy it!
I will return to Pasadena next week. See you then.
  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.
  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.
  663   Sun Jul 13 17:19:29 2008 ranaSummaryPSLMOPA SLOWM Calibration
John, Rana

We first unlocked the FSS and ramped the SLOW actuator. With the PMC locked we observed the PMC PZT voltage
as a function of SLOWM (SLOW loop actuator voltage). We believed this to be ~1-5 GHz / V. Since this is
not so precise we then ran a slow (2 min. period) triangle wave into the slow actuator and looked at the
ref cav transmission peaks to calibrate it.

Plot is attached>

We assume that the reference cavity length = 203.2 mm then the FSR = 737.7 MHz. So looking at the plot
and using our eye to measure the SLOWM calibration is 1054 +/- 30 MHz/V. This is probably dominated by
our eye method.

Note: we tried to get the length from T010159-00-R (Michele, Weinstein, Dugolini). In that doc,
the length used is 203.3 mm whereas its 203.2 mm in the PSL FDD (?). The calculation of the FSR is also
incorrect (looks like they used c = 299460900 instead of 299792458 m/s). We took the length from the PSL FDD
(T990025-00-D) but not the FSR, since they also did not find the right value of 'c'. I guess that the speed
of light just ain't what it used to be.
  662   Sat Jul 12 23:28:31 2008 ranaUpdatePSLPMC needs help
As everyone has noticed recently, the PMC seems to have a PZT problem. It often zooms
of to one of its rails after locking as if the PZT range has decreased dramatically.

WE should check this on Monday by disabling the FSS and applying a slow triangle wave to
the NPRO frequency. The PMC will track this frequency change and this will allow us to
diagnose its problems.

If it has real problems, I have a spare in W. Bridge which we can swap in temporarily.

The attached plot shows 3 years of trend; looks like it went bad in summer of last year.

This also seems to be the cause of our ISS saturation problems: lowering the gain of the PMC
even slightly increased the intensity noise enough to cause saturation. Increasing the gain
even slightly increased the intensity noise enough to cause saturation due to PMC servo oscillation.
  661   Fri Jul 11 23:55:25 2008 alanUpdateLockingRF common mode at zero offset

Quote:
rob, john, yoichi

Last night we succeeded in reducing the CARM offset to zero.



Congratulations! Well done! I look forward to hearing the details and further progress!
  660   Fri Jul 11 20:16:01 2008 EricDAQCamerasTaking data from the GC 750 Camera
Mafalda has been set up with a background process to constantly take data from the GC 750 camera (at the end of the x-arm) for the weekend. This camera will otherwise be inoperable until then.

In the small chance that this slows either Mafalda or the network to a crawl, the process to kill should have PID 26265.
  659   Fri Jul 11 09:29:02 2008 steveUpdatePSLthe PMC still hangs up
Morning alarms:

PMC high voltage is railing, it's auto locker is frosen
I have to move DC Output Adjust slider by hand and it locks immediately

PSL_ISS is saturating. Saturation goes away when PMC is locked.

Laser chiller water is overflowing again: removed 450 cc water
  658   Fri Jul 11 00:30:24 2008 robMetaphysicsComputersstrange SUS controllers

rob, johnnieM

We were hampered early tonight by the fact that someone sneakily turned off the HP RF Ampflier on the AS table.

After that, we were hampered further by mode cleaner strangeness. It would occasionally spontaneously unlock & blow its watchdogs. It never made it through the ontoMCL script (putting DC-CARM onto the MCL). After some investigation, we found that c1susvme1 and c1susvme2 were running stochastically late (SYNC_FE != 0), even though their computation times never got above 61. Also, the end SUS controllers were never late.

Weird.

After rebooting the vertex SUS controllers and the c1lsc, things appear to be working again.
  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
  656   Thu Jul 10 19:12:07 2008 AlbertoUpdateGeneralabs cavity length measurement experiment
Yesterday morning, when I started, I found the IFO beam on a different position and the beam spot at the AS port looked very deformed. The overlapping with the secondary beam was not good enough to observe the beats anymore. Restoring the alignments of the interferometers did not work because, as John found out later, some of the photodiodes had offsets and gain which made the restore script ineffective. After resetting the parameters, we had to align every mirror of the interferometers and save the configuration twice. The second times was because on the first time the alignment had been done with the illuminators on. To avoid that in the future, John wrote an alarm to warn about the status of the lights.

After that we fixed the IFO beam, I had to realign the optics in the table to match the secondary beam to the IFO beam. I got the two beam overlapping and, even though the NPRO spot looked distorted, I could observe again some signal of the beat. To do that it was also necessary to have all the interferometer mirrors aligned so that we had more power from the ifo beam although it also made the spot flash. Ideally, to avoid the flashing (which we would also impede the PLL to work) we should work with the interferometer locked. Since that doesn't seem actually possible, we should just keep one of the ITM aligned and improve the beam matching so that we can observe the beats even with less power.

Today I spent the day trying to improve the alignement of the optics to observe the beats with only the ITM aligned, resetting the alignment of both beams with the ireses, with the Farady and all the rest. It was a rather long and tiring process but I think I'm close to the target and maybe tomorrow.
  655   Thu Jul 10 14:59:01 2008 robUpdateLockingRF common mode at zero offset
rob, john, yoichi

Last night we succeeded in reducing the CARM offset to zero.

We handed off control of the common mode servo from PO-DC to POX-I.

We pushed the common mode servo bandwidth to ~19kHz. Without the boosts, it had ~80 degs of phase margin. Didn't measure it after engaging the boosts (Boost + 1 superboost). Trying to engage the second superboost stage broke the lock.

The process is fully scripted, and the script worked all the way through several times.

The DARM ugf was ~200Hz. The RSE peak could clearly be seen. No optical spring, as expected (we're locking in anti-spring mode).

Engaging test mass de-whitening filters did not work (broke the lock).

I'm attaching a lock control sequence diagram and a trend of the arm power during a scripted up-sequence. I think the script can be sped up significantly (especially the long ramp period).

Up next:

Calibrated DARM spectrum
Noise hunting (start with dewhites)
DC - Readout
Lock to the springy side.
  654   Thu Jul 10 13:47:12 2008 YoichiHowToComputerssvn access via https
Now you can access to the svn repository on nodus by https.
To perform a checkout, you can use the following command

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

This will check out "chans" directory.
The password for svn40m is written in the usual place.
You can also access the URL by a web browser to see the repository in a very primitive way.
A nice web interface for browsing the repository is planed but not yet implemented.
  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.
  652   Wed Jul 9 15:04:22 2008 steveMetaphysicsPhotosSURFs helping hands
Surf students are helping out with baffle cleaning.
  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.
  650   Tue Jul 8 21:58:22 2008 albertoUpdateGeneralSecondaty beam aligned to the IFO beam again
Yesterday the alignment of the secondary beam to the IFO was completely lost and today I had to realign all the optics before I was able to match the two spots again. I had to reset the height of the irises and I had also to replace mirror M1 with one with a larger angular motion. Eventually I obtained the beat again. Working on the optics table I inadvertently misaligned the OSA but I didn't make in time to bring it back before the night shift people came. I'll work on that tomorrow morning.
  649   Tue Jul 8 21:46:38 2008 YoichiConfigurationPSLGC650M moved to the PMC transmission
I moved a GC650M, which was monitoring the light coming out of the PSL, to the transmission port of the PMC to see the transmitted mode shape.
It will stay there unless someone find other use of it.

Just FYI, you can see the picture from the control computers by the following procedure:

ssh -X mafalda
cd /cvs/cds/caltech/target/Prosilica/40mCode
./SampleViewer

Chose 02-2210A-06223 and click on the Live View icon.
  648   Tue Jul 8 12:25:54 2008 JohnSummaryPSLISS gain set to 2dB
  647   Tue Jul 8 10:26:30 2008 MashaUpdateAuxiliary lockingsetup updates
Yesterday I changed one of the beam splitters in the Mach Zehnder to one with a more stable mount as to reduce the system's coupling to environmental noise.

With help from John, I worked out how to get the signals from the two channels of the interferometer into the digital system. I put up BNC cables along part of the Y arm to connect the output of the detectors into the digital channels.
  646   Tue Jul 8 10:20:10 2008 steveUpdatePEMHEPA turned on
It is specially important to run the PSL-HEPA filters when inside counts is peaking at 30,000 counts

There is a small label at the hepa on/off switch:
enclosure open 100%,
low noise off,
normal 60% of Variac voltage setting on the top of the enclosure

Not running the HEPAs will lower the temp fluctuations from 1.5 to o.5 degree C
at the cost of particle counts from 0 to immidiate room counts.
  645   Tue Jul 8 08:16:56 2008 steveUpdatePSLPMC problem
The PMC is unhappy. PMC auto locker is not working.
DC output slider adjust has to be moved from rail to rail before it locks.

MZ is working great.
  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.
  643   Mon Jul 7 19:15:38 2008 AlbertoUpdateGeneralOptics alignement on the ABS length experiment
Today I started setting up the PLL instruments to lock the frequency of the NPRO beam to the IFO beam. with no need of a new alignment after the weekend I was able to see the beat again, although this time I found at a different temperature of the NPRO laser of about 54 degrees (vs 51 of the last time).
I've got the Marconi as local oscillator (LO), the mixer Koji suggetsed, the SR560 and a 5 MHz low pass filter to cut the 33, 66 and 99 MHz present in the output signal from the PD. The filter worked well and I was able to single out only the beat resonance from the power spectrum.
In the attempt to enhance the amplitude of the beat, as Koji suggested, I tried to work on the alignment of the steering mirrors. While I was doing that, for some reason the pre-modecleaner lost the alignment and I had to ask John to help me lock it again. during the process I lost the old alignment but at the end I got a new one, apparently (from the camera) even better than the other. Although after that the beats were gone. Actually after the lock-in of the PMC the IFO beam didn't look as good as before, so it might be also for that reason.

I'll try again tomorrow, after that probably tonight Rob is going to reset the alignments of the interferometers.
  642   Mon Jul 7 16:30:08 2008 steveUpdatePSLPSL-PEM 16 days trend
This morning the laser head temp was up to 20.3C because the laser chiller was overflowing.
I removed 700 cc water.

The PSL-FSS_RMTEMP became much more stable during the holidays as the psl enclosure was closed for 4 days

The high particle counts can be explaned by construction activity today.

The PMC & MZ PZT high voltages were out of range this morning.
  641   Mon Jul 7 14:02:05 2008 YoichiUpdateComputersSVN conversion progress
So far /cvs/cds/caltech/medm, /cvs/cds/caltech/chans and /cvs/cds/caltech/scripts have been converted to svn working copies.
Now /cvs/cds/caltech/target is being converted.
  640   Mon Jul 7 13:58:37 2008 Eric, josephbDAQPEMUsing unused PEM channels to test camera code
Joe and I have taken control of the EPICS channels C1:PEM-Stacis_EEEX_geo and C1:PEM-Stacis_EEEY_geo since we heard that they are no longer in use.  We are currently 
using them to test the ability for the Snap camera code to read and write from EPICS channels.  Thus, the information being written to these channels is completely unrelated
to their names or previous use.  This is only temporary; we'll create our own channels for the camera code shortly (probably within the next couple of days).

- Eric
  639   Mon Jul 7 13:49:27 2008 YoichiHowToPSLMZ offset, gain tips
John, Yoichi

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

The MZ control board has the following stages:

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

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

(2) Because the gain of the Variable Gain Amp and the Filter combined is large, the Filter can be easily saturated if the output offset is not right.
This was the cause of the MZ problem this morning. The output offset slider was at a wrong position making the error signal slightly off centered from zero.
This residual DC error signal was amplified by the large gain chain and saturated the filter amp.
Our experience is that the output offset cannot go below -3V. We set it at 0V for now.
  638   Mon Jul 7 13:06:38 2008 KojiUpdateGeneralBeats of the two lasers in the absolute length measurement observed
One may need an RF filter after the mixer. I expect the SR560 does work for this purpose.
If it does not, a passive LPF can be used.


Quote:
I didn't post a screenshot from the RF SA because I had troubles with the interface with the computer (unfortunately the network SA cannot export the data).

There's is problem with the PLL circuit. The signal, beside the beat, also contains peaks at 33, 66 and 99 MHz, so we should think about filtering those out, correct?
  637   Mon Jul 7 11:22:02 2008 AlbertoUpdateGeneralBeats of the two lasers in the absolute length measurement observed
I didn't post a screenshot from the RF SA because I had troubles with the interface with the computer (unfortunately the network SA cannot export the data either).

There is problem with the PLL circuit. The signal, beside the beat, also contains peaks at 33, 66 and 99 MHz, so we should think about filtering those out.


Quote:
Great! Conguraturation! I wish if I could see it! It's nice if you can put the photo or anything of the RF spectrum analyzer.

Next step:
o You can try to maximize the beat amplitude by the tuning of the Injection steering mirrors.

o At the south end of the SP table, I prepared a frequency mixer. You can put the beat signal into the RF input, and an oscillator (which you can bring from somewhere) to the LO input in order to obtain the error signal of the PLL. Put the IF output of the mixer in a SR560, and please try to lock it by a simple 6db/oct (1st order) LPF of the SR560. For the actuator you can use the fast-pzt input of the NPRO.


Quote:
Then I explored the range of temperature of the NPRO from 35deg (C) to 51.2807deg and at that point I could observe a peak corresponding to the beat at about 10MHz on the network analyzer.
  636   Sun Jul 6 16:17:40 2008 tobinHowToComputersSVN
I was able to check out the 40m SVN here in Livingston using this command:

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

As you might guess, this uses ssh in place of the web server (which we don't have yet).
  635   Thu Jul 3 22:54:45 2008 KojiUpdateGeneralBeats of the two lasers in the absolute length measurement observed
Great! Conguraturation! I wish if I could see it! It's nice if you can put the photo or anything of the RF spectrum analyzer.

Next step:
o You can try to maximize the beat amplitude by the tuning of the Injection steering mirrors.

o At the south end of the SP table, I prepared a frequency mixer. You can put the beat signal into the RF input, and an oscillator (which you can bring from somewhere) to the LO input in order to obtain the error signal of the PLL. Put the IF output of the mixer in a SR560, and please try to lock it by a simple 6db/oct (1st order) LPF of the SR560. For the actuator you can use the fast-pzt input of the NPRO.


Quote:
Then I explored the range of temperature of the NPRO from 35deg (C) to 51.2807deg and at that point I could observe a peak corresponding to the beat at about 10MHz on the network analyzer.
  634   Thu Jul 3 18:48:09 2008 AlbertoUpdateGeneralBeats of the two lasers in the absolute length measurement observed
I adjusted the alignment of the flipper mirror as suggested by Koji making the two beam spots match. I also aligned all the IFO mirrors (ITMs, PRM, SRM, ETMs) to have more power for the IFO signal at the AS port. When I did that I could see the beats at the AS OSA. Then I explored the range of temperature of the NPRO from 35deg (C) to 51.2807deg and at that point I could observe a peak corresponding to the beat at about 10MHz on the network analyzer. The peak tends to drift because the laser takes probably a longer time to actually thermalize and it moves very rapidly changing the temperature of the laser.
  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.
  632   Thu Jul 3 16:18:51 2008 robSummaryLockingspecgrams
I used ligoDV to make some spectrograms of DARM_ERR (1), QPDX (2), and QPDY (3). These show the massive instability from 30-40Hz growing in the XARM in the last two minutes of a reasonably high power lock (arm powers up to 30). It's strange that it only shows up in one arm.

CARM is on PO-DC, for both the MCL and the AO path.
DARM is on AS166Q.
  631   Thu Jul 3 13:54:26 2008 robConfigurationComputersmDV on rosalba

Does mDV work on rosalba? It can't find NDS_GetChannels. Looking on mafalda, I see that NDS_GetChannels is a mexglx. I think this means someone may need to compile it for 64-bit matlab before we can have mDV on rosalba. When that's done, we should get mDV running on megatron.
  630   Thu Jul 3 13:12:32 2008 Rob, Yoichi, JohnUpdateLockingMore oscillations
Bounce/ roll filters were added to the short degrees of freedom to reduce the effect of the 24Hz line seen on Tuesday night.

However last night saw the arrival of a new oscillation at ~34Hz. This may be the second harmonic of the MOS roll mode. Reducing the arm offset would cause this oscillation to ring up and break the lock (first plot). This effect was repeatable.

No signal was seen in the oplevs or osems which leads us to rule out alignment problems, at least for now.

Although one can clearly see DARM_ERR increasing as arm power increases adding a resonant gain in the DARM loop had no effect.

We also noticed that x arm transmission was significantly more noisy than the Y (second plot). And showed greater coherence with the increase in DARM noise. Investigations showed that the PD was not the source of the difference.

Turning up the MC gain seems to help a little.

We're now looking at POX as a candidate for RF_CARM (third plot).
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