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ID Date Author Typeup Category Subject
  17   Fri Oct 26 09:10:17 2007 steveRoutinePEMPEM &PSL trend
The fires are out, lab particle counts are up.
Psl HEPAs are at 100% and mobel HEPAs are just turned on
20 days plot and 5 hrs plot below
  18   Fri Oct 26 16:19:29 2007 Tobin FrickeRoutineIOOMC resonances
We would like to measure the absorption of the mode cleaner optics. The plan is to repeat <a href="http://ilog.ligo-wa.caltech.edu:7285/mLIGO/Cleaning_the_Mode_Cleaner">Valera's experiment</a> in which we track the MC's thermal resonances to infer their power absorption. Last night Rana and I hooked up a lock-in amplifier to heterodyne the MC servo signal by 28 kHz and piped the output into an ADC using the MC_AO channel. We did not find any resonances.

Valera recommends we drive the POS of the three MC optics with bandlimited noise to excite the resonances.
  23   Mon Oct 29 09:16:31 2007 steveRoutineVACthe rga is back
We had no filament current since last power glitch of Oct. 8, 2007
First I thought that the filament was lost, but it was only bad contact.
The rga head pins were oxidized. Rga was turned back on last Friday.
It's temp is 55.3C normal
  24   Mon Oct 29 09:46:50 2007 steveRoutineVACvac & pem trend
Pumpdown 64 pumped by maglev for 125 days

Rob, can you tell me, when did the fire start on this plot?
  31   Tue Oct 30 16:55:40 2007 tobinRoutine Drag-wiping perfected
Steve, Tobin

Steve procured an assortment of syringes from the bio storeroom and we practiced drag-wiping the SOS in the flow bench. Using a 50 microliter Hamilton syringe to deliver 16 microliters of methanol seems perfect for drag-wiping the small optics. Drag-wiping in the downward direction seems to work very well, since we can squirt the optic directly in the center, and the (half) piece of kodak lens tissue fits easily between the bottom two earthquake stops.
  38   Wed Oct 31 10:31:23 2007 Andrey RodionovRoutineVACVenting is in progress

We (Steve, David, Andrey) started venting the vacuum system at 9.50AM Wednesday morning.
  39   Wed Oct 31 15:02:59 2007 tobinRoutineIOOMode Cleaner Mode Tracking
I processed the heterodyned mode cleaner data yesterday, tracking the three 28 kHz modes corresponding to MC1, MC2, and MC3. Unfortuntately the effect of our MC power chopping is totally swamped by ambient temperature changes. Attached are two plots, one with the tracked mode frequencies, and the other containing dataviewer trends with the MC transmitted power and the room temperature. Additionally, the matlab scripts are attached in a zip file.
  41   Wed Oct 31 19:26:08 2007 Andrey RodionovRoutineGeneralPhotographs of "Mode-Cleaner Entrance"

Here are the pictures of "inside the chamber".
  44   Thu Nov 1 09:17:27 2007 steveRoutineVACvent 64
Yesterday before vent I could not lock MC, therfore I could not measure the
transmitted power at MC2
The vent went well. We had lots of help.

We could not find the Nikon D40
PLEASE BORROW THINGS when taking them away
and bring them back promtly.

The laser was turned off for better visibility.

I see clean room frorks laying around here and there.
Please put them away so we do not carry excess particles into the chamber.
  13   Thu Oct 25 00:01:21 2007 ranaSoftware InstallationCDSGEO DV => LIGO DV
Martin Hewitson of GEO600 fame has modified the cool GEO DV
to work with the LIGO NDS system with some NDS advice from Rolf (who's over in Germany this week).

I've moved it onto the 40m CDS system and installed it on the AdhikariLab computer named 'django'. It worked immediately.

I modified the main .m file to include the 40m's NDS server. When you run it you have to include the path to the NDS
client written by Ben Johnson.

The attached is a screenshot of it working on a Mac; it looks as cool on Linux.

Its installed in /cvs/cds/caltech/apps/ligoDV/. In matlab you navigate to that directory and then
type addpath('/cvs/cds/caltech/apps/linux/UNIX_NDS_Client_beta2/') to add the NDS client.
On the Solaris machines, type type addpath('/cvs/cds/caltech/apps/solaris9/UNIX_NDS_Client_beta2/') instead.

Then type ligoDV to start it up. Then click away and have fun.

In the example I've selected
and plotted its specgram.

Big grin
  25   Mon Oct 29 11:07:22 2007 waldmanSoftware InstallationOMCSoftware install on OMS
[Alex, Sam]

We spent a little time this morning working on OMS and getting things restarted. A few changes were made. 1) We put openmotif on OMS so that the burtrb doesn't throw that crappy libXm any more. 2) We upgraded OMS to a 32 kHz sampling rate from 2 kHz. All the filters will have to be changed. We also added a PDH filter path to maybe feedback PDH signals cuz that will be cool. Maybe someday I will write up the very cool channel adding procedure.
  28   Mon Oct 29 23:25:42 2007 tobinSoftware InstallationCDSframes mounted
I mounted the frames directory on mafalda and linux3. It's intentionally not listed in the /etc/fstab so that an fb crash won't prevent the controls machines from booting. The command to mount the frames directory is:

mount fb40m:/frames/frames /frames
  46   Thu Nov 1 16:34:47 2007 Andrey RodionovSummaryComputersLimitation on attachment size of E-LOG

I discovered yesterday when I was attaching photos that it is NOT possible to attach files whose size is 10Mb or more. Therefore, 10Mb or something very close to that value is the limit.
  47   Thu Nov 1 16:42:48 2007 Andrey RodionovSummaryEnvironmentEnd of Daylight Saving Time this weekend
Useful information for everyone, as a friendly reminder:

According to the web-page


this coming weekend there will be the end of Daylight Saving Time.

Clocks will be adjusted backward one hour.
  56   Thu Nov 1 20:03:00 2007 Andrey RodionovSummaryPhotosProcedure "Drop and Drag" in pictures
  58   Fri Nov 2 12:18:47 2007 waldmanSummaryOMCLocked OMC with DCPD
[Rich, Sam]

We locked the OMC and look at the signal on the DCPD. Plots included.
  59   Sat Nov 3 16:20:43 2007 waldmanSummaryOMCA good day's work

I followed up yesterday's test of the PZT with a whole mess of characterizations of the PZT control and finished the day by locking the OMC with a PZT dither lock and a 600 Hz loop. I haven't analyzed any of the data yet, so its not calibrated in physical units and etc. etc. etc. Since a lot of the sweeps below are of a "drive the PZT, look at the PDH signal" nature, a proper analysis will require taking out the loop and calibrating the signals, which alas, I haven't done. Nonetheless, I include all the plots because they are pretty. The files included below are:

  • DitherLock_sweep: Sweep of the IN2/IN1 for the dither lock error point showing 600 Hz UGF
  • HiResPZTDither_sweep: Sweep of the PZT dither input compared to the PDH error signal. I restarted the front end before the sweep was finished accounting for the blip.
  • HiResPZTDither_sweep2: Finish of the PZT dither sweep

More will be posted later.
  65   Tue Nov 6 09:14:37 2007 steveSummaryVACpump down 65
8 hr plot,
precondition: 5 days at atm,
vent objective: drag wiping mc1, mc2 & mc3 accomplished,
hardware changes: IOO access connector, mc2 chamber door south & west
were removed and reinstalled
pump down mode: slow to avoid steering up dust
One roughing pump was used with closed down valve position in the first 4 hrs

Andrey was very helpful
  66   Tue Nov 6 09:45:22 2007 steveSummarySUSvent sus trend
The mc optics dragwippings were done by locking optics by eq stops and rotating-moving
cages so access were good. This technic worked well with mc1 & mc2
MC3 osems were reoriented only.
  104   Thu Nov 15 04:18:11 2007 JohnSummaryPSLPMC cavity pole measurements
In connection with our work on the ISS I attempted to measure the PMC cavity pole.

I swept the PMC PZT and looked at the transmission through the cavity on the ISS Monitor diode (which is now back on the table, feel free to remove it again tomorrow).

To avoid thermal effects I reduced the laser power using the half wave plate at the laser ouput (rotated from 6 deg to 340deg).

I swept the PZT using the triangle wave command "trianglewave C1: PSL-PMC_RAMP -3.5 3.3 20 200". I noticed that the functional form of the resonances deteriorated over the duration of the excitation. Each sweep was able to capture just over one FSR. The resonances were a little close to the 'points' of the triangle wave for my liking although I don't think PZT hysteresis was a big factor.

Looking at the data the peaks are not of uniform width across a sweep or between consecutive sweeps. Hence any results from this mesurement are not particularly useful. I can't be sure if this was due to misalignments, thermal effects, higher order mode content or some other affect.

Rob suggests sweeping the laser frequency using the NPRO PZT instead.
  108   Thu Nov 15 18:36:48 2007 JohnSummary PSL table work
I've rotated the lambda/2 plate to 340deg (from 6 deg) and blocked one arm of the Mach-Zender. Undo both if you need to.
  116   Tue Nov 20 10:11:33 2007 JohnSummaryPSLPMC pole measurements
We measured the PMC pole in the following way.

1. Reduced laser power by rotating lambda/2 plate at laser output. Thermal effects in the PZT distort resonance peaks. Reducing power too much leads to problems with digitisation error.

2. Sweep NPRO PZT (C1: PSL-FSS_INOFFSET) using trianglewave. Record ramp, PMC transmission and reference cavity transmission ('C1: PSL-FSS_FAST','C1: PSL-ISS_INMONPD_F','C1: PSL-FSS_RCTRANSPD_F).

3. Since the PZT cannot sweep a full FSR in the PMC we looked at the sideband resonances within the reference cavity to calibrate the actuator.
Result: 7.35 +/- 0.22 MHz/V

4. Use #3 to calibrate the x axis of the PMC transmission.

5. Fit PMC resoances to an Airy function to get finesse. Take an average, weighted according to the resnorm. Calculate cavity pole frequency.
Result: 380kHz +/- 59kHz. This corresponds to a finesse of ~936. According to this plot the nominal pole is at 488kHz and the finesse is 732.

This is by no means a definitive measurement due to the misshapen resonance peaks recorded.
  119   Tue Nov 20 18:02:54 2007 JohnSummaryComputersPSL_Main screen
I've updated the PSL_MAIN screen. The old version may be found in cvs/cds/caltech/medm/old/medm/psl.
  144   Fri Nov 30 11:22:22 2007 ajwSummaryCDSGEO DV => LIGO DV

Martin Hewitson of GEO600 fame has modified the cool GEO DV
to work with the LIGO NDS system with some NDS advice from Rolf (who's over in Germany this week).

I've moved it onto the 40m CDS system and installed it on the AdhikariLab computer named 'django'. It worked immediately.

I modified the main .m file to include the 40m's NDS server. When you run it you have to include the path to the NDS
client written by Ben Johnson.

The attached is a screenshot of it working on a Mac; it looks as cool on Linux.

Its installed in /cvs/cds/caltech/apps/ligoDV/. In matlab you navigate to that directory and then
type addpath('/cvs/cds/caltech/apps/linux/UNIX_NDS_Client_beta2/') to add the NDS client.
On the Solaris machines, type type addpath('/cvs/cds/caltech/apps/solaris9/UNIX_NDS_Client_beta2/') instead.

Then type ligoDV to start it up. Then click away and have fun.

In the example I've selected
and plotted its specgram.

Big grin

Download and installation instructions, as well as a few examples for use
can be found here (typical lsc username and password):

  150   Fri Nov 30 20:13:57 2007 dmassSummaryGeneralHeNe UniPhase Laser
Data for the Uniphase 1.9 mW HeNe laser (labeled: "051507 From ISCT-BS") SN: 1284131 Model: 1103P

I used the Photon Beamscanner to obtain all data, then fit w(z) as shown on the plot with parameters w_0, z_R, and hidden parameter delta,
where z = delta + x, z is waist distance, x is distance from the laser.

Copies of the matlab code used to fit (/plot) are attached in .zip below.
  174   Thu Dec 6 15:22:42 2007 AndreySummaryElectronicsPictures of the inside of He-Ne laser

Steve gave me an old "dead" He-Ne laser that long time ago was used for ETMX optical lever.

I dismantled it (cutting the metallic enclosure with a metallic saw), and these are two pictures of what is inside.
  178   Fri Dec 7 00:02:26 2007 ranaSummaryIOOMC/FSS Frequency Noise
The FSS frequency noise is not very bad.

I compared the MC_F spectra between Hanford and the 40m using DTT and its 'User NDS' option.
After Sam, Jenne, and DavidM installed the new MC Servo some time ago, the MC_F spectrum here
has had some whitening before it goes into the DAQ (on board; same as LLO & LHO). The tuning
coefficient of the VCO is also basically the same between all PSLs since everyone has the same
chip in the VCO driver.

Therefore, at the frequencies where the MC gain is more than ~4, the MC_F signal calibration is
the same here as anywhere. Since its the servo control signal, its basically a measure of the
frequency noise incident on the MC -- its just what comes out of the FSS with the table noise on
top. At low frequencies (< 100 Hz) its a measure of the motion of the MC mirrors.

Above 200 Hz ours is the same as theirs; except for the enormous power line spikes. I think that's
either all on the light. But our acoustics are better and the noise above 1 kHz levels off at the
same flat floor (the phase noise of the VCO) as H1. The huge lump around 100 Hz is the MC2 DAC noise and
it goes down to the H1 levels when we flip on the dewhites. The giant excess from 5-50 Hz is just the fact
that our stacks don't do much until 20-30 Hz.

So we can stop blaming the FSS and move on with life as soon as Tobin gets the ISS back in shape.
  199   Tue Dec 18 23:41:00 2007 AndreySummaryComputer Scripts / ProgramsResults of Mon/Tue overnight measurements (entry #194)

Here I inform our community about the results of the measurements of RMS values in XARM during the previous night from Monday to Tuesday (I announced those measurements in ELOG entry #194).

All the plots in today's report seem to agree well with the analogous plots from the night from Saturday to Sunday (those results are given in ELOG entry # 195).

All the intervals in which RMS have been calculated are the same as in yesterday's ELOG entry #195.

I plotted three results for RMS in the abovementioned three intervals in three different ways:

1) view from the top in the axes (Q_{ITMX}+Q_{ETMX})/2 and (Q_{ITMX}-Q_{ETMX}) -> first three graphs (attachments 1 -3);

2) view from the side in the same sum- and difference-axes -> next three graphs (attachments 4-6);

3) view from the side in Q_{ITMX} and Q_{ETMX} axes -> next three graphs (attachments 7-9, also attch. 12), above accelerometer spectra (attachments 10-11).

Also, I compared the ground noise level by comparing spectra of accelerometer signals at different times during that night. As a reminder, before my disease I installed one accelerometer near ITMX and another accelerometer near ETMX (see entries 161 and 172 in ELOG). The plots of ratios of accelerometer signals at different times (pairs of times that were used: 11PM and 2AM, 11PM and 5AM, 11PM and 8AM) are given below, see attachments 10-11. The program was running from 11PM on Monday till 9AM on Tuesday.

As I explained in the previous ELOG entry # 198, tonight I am taking experimental data in the narrowere interval from 1.00 to 4.50 with a smaller step 0.25.
  202   Wed Dec 19 16:07:37 2007 AndreySummaryComputer Scripts / ProgramsResults of overnight measurements Tue/Wed night (entry #198)

As indicated in ELOG entry 198, I was making overnight measurements during last night from Tuesday to Wednesday.

I was changing the suspension damping gain in ETMX and ITMX in "position" degree of freedom between values of 1.00 and 4.50 with the step 0.25.

Results for RMS of peaks (A) at 0.8Hz, (B) at about 3.0Hz and (C) in the range from 0.6Hz to 3.7Hz ("RMS in a broad interval") are given below:

I plotted three results for RMS in the abovementioned three intervals in three different ways:

1) view from the top in the axes (Q_{ITMX}+Q_{ETMX})/2 and (Q_{ITMX}-Q_{ETMX}) -> first three graphs (attachments 1 -3);

2) view from the side in the same sum- and difference-axes -> next three graphs (attachments 4-6);

3) view from the side in Q_{ITMX} and Q_{ETMX} axes -> next three graphs (attachments 7-9)

Attachments 10 and 11 show ratios of accelerometer signals at different times of the night/morning.

A little discussion about these graphs:

1) The areas of minima and of rapid growth are the same for all the measurements during all three nights.

2) Tonight there was a strange spike for the values of Q_{ETMX}=2.5 and Q_{ITMX}=4.0. I interpret that as an error of experiment.

3) On all the plots from all three nights there is a wide area of minimum on the plots for RMS at 0.8Hz and for "RMS in the broad interval",
and the graph for "RMS at 3Hz" indicates a clearer minimum in a localized area for Q_{ITMX}=2+-1, Q_{ETMX}=2+-1. Note that this area 2+-1
is included into the wide region of minimum for "RMS at 0.8Hz" and "RMS in a broad range".

Therefore, my guess at this stage is that we can choose the optimized value of suspension damping gains for both Q_{ITMX} and Q_{ETMX} somewhere
around 2+-1. I would like to make another overnight measurement (tonight) in that narrowed region with a small step to have more certainty.

By the way, I realized that I was a little bit careless and at some plots Q_I stands for {Q_ITMX}, and Q_E stands for Q_{ETMX}.
  209   Thu Dec 20 21:58:28 2007 AndreySummaryComputer Scripts / ProgramsResults for 2 previous XARM measurements have been added

I attached results (plots) of yesterday's daytime and overnight measurements to the initial reports about those measurements.

These are ELOG entries # 201 and # 205.
  219   Wed Jan 2 11:38:56 2008 tobinSummaryWIKI-40M Updatewiki spam
Our wiki keeps getting spammed. It turns out that you can upload attachments without a password, which is a bug. I'll ask David Barker whether there's a fix for this.
  231   Thu Jan 10 00:12:01 2008 tobinSummaryLockingDR
[John, Tobin, Rana]

1. We found SUS_BS_SENSOR_UL to have a ratty signal and low DC value. Twiddling the cables at the BS satellite amplifier and vacuum feedthrough brought the signal back (to 0.667V), but it is still spiky, spiking up to a couple times per second. Rana suggested that these spikes might be scattered YAG laser light (as hypothesized in August). The spikes go away when we misalign the PRM or either ITM, and when we unlock the mode cleaner, lending credance to this theory. SUS_BS_SENSOR_UR also spikes, but much less frequently. We turned off C1:SUS-BS_ULSEN_SW2 and continued.

2. After dither alignment the oplev beams were centred and we were able to lock DRM plus either arm reliably (however locking in this state broke ./drstep_bang at the first ``Going DD''). We ran scripts/DRFPMI/bang/nospring/drdown_bang and were subsequently able to lock DRFPMI (i.e., full IFO) a couple times.

3. To do: Debug ./drstep_bang with just the DRM (no arms).
  256   Wed Jan 23 12:31:36 2008 AndreySummarySUSDissapointing Results of XARM optimization (PDF-file)

I attach a PDF-file which summarizes briefly the results of measurements/calculations of Q-factors for ITMX mass as a function of suspension damping gain,

and this file contains the results of measurements of RMS peaks on the values of suspension gains of ITMX and ETMX (see ELOG entries from December 2007, specifically #202, #199, #194)),
but now those dependences are plotted in Q-ITMX and Q_ETMX axes.

Unfortunately, there are no clear narrow areas of minimum in those dependences (that explains the sad title of this ELOG entry).

The attached pdf-file can be shown as a short presentation for a wall during our Wednesday meeting.
  257   Wed Jan 23 20:52:40 2008 ranaSummaryEnvironmentFlooding from construction area
We noticed tonight around 7 PM that there was a lot of brown water in the control room and also in the interferometer area mostly concentrated around the north wall between the LSC rack and the AP table.

The leak was mainly in the NW corner of the interferometer area.

The construction crew had set up sandbags, plastic sheet, and gravel to block the drains outside of the 40m along the north wall. The rain had produced ponds and lakes outside in the construction area. Once the level got high enough this leaked through holes in the 40m building walls (these are crappy walls).

We called the on-call facilities team (1 guy). He showed up, cut through the construction fence lock, and then unblocked the drains. This guy was pretty good (although inscrutable); he adjusted the sandbags to control the flow of the lake into the drains. He went along the wall and unblocked all 3 drains; there were mini-lakes forming there which he felt would eventually start leaks all along our north wall.

In the morning we'll need volunteers to move equipment around under Steve's direction while the floor gets mopped up. There's dirt and mud all over, underneath the chambers and racks.

Luckily Alberto spotted this early and he, Jon, Andrey and Steve kept the water from spreading and then scooped it all up with a wet-vac that the facilities guy brought over.
Extra Napoleon to them for late evening mud clearing work.

Many pictures were taken: Update and pictures will appear later.
  259   Thu Jan 24 12:50:50 2008 JohnSummaryTreasureSugar Napoleons
Some pictures from the group meeting yesterday.
  271   Sat Jan 26 02:02:43 2008 JohnSummaryGeneralNew Channels
I added the following channels.



The old .ini file is /cvs/cds/caltech/chans/daq/C0EDCU_26_1_2008.ini
  275   Sat Jan 26 18:48:43 2008 JohnSummaryComputersRestart iscepics
iscepics died this afternoon. We restarted it and restored settings from yesterday. I've written up instructions in the wiki.
  283   Mon Jan 28 19:35:55 2008 ranaSummaryPEMAccelerometer and Seismometer Coherences
The attached PDF shows that there is some strange behavior at low frequencies.

From the plot it looks like to me that the Wilcoxon accelerometers (which are supposed to have good response down to 0.05 Hz) are not displaying real seismic motion below 0.3 Hz. Because the coherence length for seismic waves at those frequencies should be 100's of meters we should expect that the accelerometers would have good coherence (>0.8) down there. Instead, my guess is that its all air currents, temperature, or electronics noise. These sensors are not reliable indicators for the microseism.

The Ranger seismometer, however, seems to work fine down to just below the microseism. The Ranger is mounted down around the X end and pointing in the z-direction. The coherence I plotted between it and EX_Z is larger than any other acc/seis pair (as expected).

JM and I discussed what could be done; if we get a SURF student who's into building stuff we can ask them to make a styrofoam hut for the Wilcoxons to see if that helps anything. JM also asked what the point of all this is.

IF we want to do good Adaptive Noise subtraction then we need sensors which can sense the motion which disturbs the mirrors and they need to sense it with a good SNR to get a good subtraction ratio. If the styrofoam thing doesn't work, we should probably look into getting a Guralp 3-axis seismometer for the corner area and just move the accelerometers down to the ends. The sites have Guralp CMG-40T units (~ 8k$). I think we should check out the CMG-3T or the CMG-3ESP.

Does anyone know someone in the Geo depts that we can borrow one from?
  285   Wed Jan 30 11:49:30 2008 AlbertoSummaryElectronicsRF monitor's filters final schematics and transfer functions
These are the final schematics for the 6th order Chebyshev filters of the RF monitor board. I'm also attaching the TF as I measured. The tuning is probably not optimal, less insertion noise could be achieved.
  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.
  306   Sun Feb 10 20:47:01 2008 AlanSummarySUSAll watchdogs tripped
A moderate earthquake occurred at 11:12:06 PM (PST) on Friday, February 8, 2008.
The magnitude 5.1 event occurred 21 km (13 miles) NW of Guadalupe Victoria, Baja California, Mexico.
  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.

  338   Fri Feb 22 20:42:44 2008 AndreySummaryComputer Scripts / ProgramsIt 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.

  341   Tue Feb 26 20:24:04 2008 AndreySummaryTMISorrow
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.
  348   Fri Feb 29 13:51:17 2008 JohnSummaryLSCPD6 response
I checked the response of PD6 using the AM laser. It looks happy enough.

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

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

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

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

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

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

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

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

xdata = f_Hz;
ydata = phase_deg;

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

phase_deg = phase_deg-fit;

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

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

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

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

for ivar = 1:length(f_beat_MHz);

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


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

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

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

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

% Make the top of the phase plot align to the bottom of the
% magnitude plot
set(gca, 'Color', 'None', 'Position',PhaseLayout, 'YTick',[-180:45: ...
set(gcf,'units','normalized','outerposition',[0 0 1 1]);
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