40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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ID Date Author Type Categoryup Subject
  1189   Tue Dec 9 10:48:17 2008 CarynSummaryGeneralcalibrating the jenne laser: impedance mismatch?

We sent RFout of network analyzer to a splitter, with one side going back to the network analyzer and the other to the laser modulation input. We observed a rippled transfer function through the splitter. The ripple is probably due to reflection due to an impedance mismatch in the laser.
Attachment 1: reflection.png
reflection.png
  1194   Fri Dec 19 11:18:52 2008 AlbertoConfigurationGeneralMode Cleaner Temperature Monitor
I reduced from 10 to 5 the gain of the SR560 that Caryn has set up after the lock-in amplifier nest to the PSL rack because the overload LED was flashing.
  1198   Sat Dec 20 23:37:43 2008 robOmnistructureGeneralSaturday Night Fever after presumed power failure

Just came by to pick something up...

... alarm handlers screeching...

... TP1 failure--closing V1... call Steve... Steve says ok till tomorrow...

... all front ends down (red)...

... all suspensions watchdogged...

... all (I think) servos off...

... PSL shutter closed ...

... chiller at 15C ... I turned it off to prevent condensation in PA...

... MOPA shutter closed... turned off key on Lightwave power supply

... good luck all, and happy holidays!
  1218   Thu Jan 8 20:26:17 2009 robOmnistructureGeneralEarthquake in San Bernardino
Magnitude 4.5
Date-Time

* Friday, January 09, 2009 at 03:49:46 UTC
* Thursday, January 08, 2009 at 07:49:46 PM at epicenter

Location 34.113N, 117.294W
Depth 13.8 km (8.6 miles)
Region GREATER LOS ANGELES AREA, CALIFORNIA
Distances

* 2 km (1 miles) S (183) from San Bernardino, CA
* 6 km (4 miles) NNE (25) from Colton, CA
* 8 km (5 miles) E (89) from Rialto, CA
* 88 km (55 miles) E (86) from Los Angeles Civic Center, CA

Location Uncertainty horizontal +/- 0.3 km (0.2 miles); depth +/- 0.8 km (0.5 miles)
Parameters Nph=142, Dmin=1 km, Rmss=0.38 sec, Gp= 14,
M-type=moment magnitude (Mw), Version=Q

I felt it from home.

All the watchdogs are tripped, vacuum normal. It looks like all the OSEM sensor values are swinging, so presumably no broken magnets. I'm leaving the suspensions off so we can take fine-res spectra overnight.

Watchout for crappy cables coming loose.
  1222   Mon Jan 12 10:57:38 2009 robUpdateGeneralsome stuff

The AS beam was not hitting the AS166 diode, so I aligned the last little steering mirror and adjusted the phase for MICH locking.

I turned on the HV supplies for the OMC.

Then I realigned the beam onto the AS166 diode, since the steering mirrors came on when I turned on the HV supplies.

It took awhile to find the alignment of the beam into the OMC. Once that was done, the output beam alignment was set, so I aligned onto the AS166 diode a third time.

The bottom two Sorensens in the OMC voltage supply don't look right. They have stickers that say +-24V, but each is sitting at 17.5V and showing no current draw. What's going on here?
  1263   Mon Feb 2 12:35:22 2009 AlbertoConfigurationGeneralNew Elog 2.7.5 in Service on Nodus
I moved the 40m, the Adhikari Lab and the SUS elogs from Dziban (located in Millikan's 6th floor) to our gateway server Nodus. In this way we should the complete control of it. I also updated the elog manager from the 2.6.5 version to the 2.7.5. Some smoothing of its interface might still be needed these days. We'll be testing it for a while before killing the old one. from now on everybody is invited to use only the new elog address since there will be no record of entries posted in the old one. Let me know of any possible difficulty in having access to it.
  1264   Mon Feb 2 17:25:44 2009 AlbertoConfigurationGeneralSome little problem with the new elog
For some reason the new elog does not look exactly like it should. 1) Some of the editing features are not available. 2) The Reply option opens the HTML of the message by default. I think this is happening because Nodus is a Sun of platform and things are a little bit different from linux. I'm working to fix these things. If I make any change and need to restart the elog, I'll try to be very quick. I apologize for the inconveniences.
  1265   Mon Feb 2 18:32:54 2009 AlbertoConfigurationGeneralSome little problem with the new elog

Quote:
For some reason the new elog does not look exactly like it should. 1) Some of the editing features are not available. 2) The Reply option opens the HTML of the message by default. I think this is happening because Nodus is a Sun of platform and things are a little bit different from linux. I'm working to fix these things. If I make any change and need to restart the elog, I'll try to be very quick. I apologize for the inconveniences.

 I think I solved the problem (as you can probably see).

The cause was that this WYSIWYG interface for HTML is provided by an independent text editor called FCKeditor which is included in the elog. Although the elog installer has a bug and does not unzip properly the relative package. One has to do it by hand. (going to /elog/scripts/ and unzipping fckeditor.zip by hand in the same directory).

  1266   Mon Feb 2 18:51:02 2009 AlbertoConfigurationGeneralNew Elog 2.7.5 in Service on Nodus

Quote:
I moved the 40m, the Adhikari Lab and the SUS elogs from Dziban (located in Millikan's 6th floor) to our gateway server Nodus. In this way we should the complete control of it. I also updated the elog manager from the 2.6.5 version to the 2.7.5. Some smoothing of its interface might still be needed these days. We'll be testing it for a while before killing the old one. from now on everybody is invited to use only the new elog address since there will be no record of entries posted in the old one. Let me know of any possible difficulty in having access to it.

 As a reference. The elog runs on background in nodus.

To kill the process:

1) pkill -3 elogd

2) rm -f /var/run/elogd.pid

To restart it:

elogd -p 8080 -c /export/elog/elog-2.7.5/elogd.cfg -D

  1267   Mon Feb 2 19:23:53 2009 YoichiUpdateGeneralNew optical layout plan
The attached is a plan of the optical layout in the central part for the upgrade.
I included, the folded recycling cavities, oplevs for the core optics, POX, POY, POB and video views.
I have not worked out how to handle the beams outside the chambers. It should not be that difficult.
I also did not include beam dumps for unwanted beams.

I used pink for main beams, brown for picked off beams, red for oplevs.

Comments, suggestions are welcome.
Attachment 1: 40mUpgradeOpticalLayoutPlan01.pdf.zip
  1269   Tue Feb 3 19:24:14 2009 YoichiUpdateGeneralNew optics layout wiki page
I uploaded a slightly updated version of the new optics layout on the 40m wiki.
http://lhocds.ligo-wa.caltech.edu:8000/40m/Upgrade_08/Optical_Layout

I also uploaded the Mathematica notebook I used to calculate various parameters of the new recycling cavities, including the lengths, asymmetry, ROCs, PRM reflectivity and TT-mirror loss margin etc.
It would be nice if someone could check if the calculation is reasonable.
There is a PDF version of the document for non-Mathematica users.
  1271   Wed Feb 4 17:45:39 2009 YoichiUpdateGeneralMode matching of the upgraded IFO
I did mode matching calculations for the new optical layout.
For the input mode matching, we have to change the focal length of the second mirror from 687mm to 315mm and the distance between the two MMT mirrors from 137mm to 149.2mm.
For the mode matching to the OMC, we only have to change the distance between the OMMT mirrors from 384mm to 391mm. No need to change the mirrors.

Details of the calculations can be found in
http://lhocds.ligo-wa.caltech.edu:8000/40m/Upgrade_08/Optical_Layout?action=AttachFile&do=get&target=NewRecyclingCavities.zip
(Mathematica notebook)
or if you prefer PDF, here
http://lhocds.ligo-wa.caltech.edu:8000/40m/Upgrade_08/Optical_Layout?action=AttachFile&do=get&target=NewRecCav.pdf
  1272   Wed Feb 4 19:22:57 2009 YoichiUpdateGeneralDo we need off-axis parabolic mirrors ?
I also estimated the mode matching degradation caused by the astigmatism.
Since the incident angles to the mode matching mirrors are not 0, the effective focal lengths in the incident plane and the perpendicular plane are different.
This effect leads to astigmatism of the beam.
When there is astigmatism, the maximum achievable mode matching rate becomes less than 100%.
According to my calculation, the mode matching cannot be better than 94% for the input beam.
For the output mode matching, we can theoretically achieve more than 99% even with the astigmatism.
The difference comes from the fact that the OMMT is longer, thus the incident angle is smaller.

If we don't like this 94%, we have to use off-axis parabolic mirrors, or modify the IMMT to a longer one.
I prefer to make it longer. Just 5" elongation will increase the mode matching rate to 99.4%.
We have a room for this 5" elongation.

Again, the details of the calculation are added to the Mathematica notebook below.


Quote:
I did mode matching calculations for the new optical layout.
For the input mode matching, we have to change the focal length of the second mirror from 687mm to 315mm and the distance between the two MMT mirrors from 137mm to 149.2mm.
For the mode matching to the OMC, we only have to change the distance between the OMMT mirrors from 384mm to 391mm. No need to change the mirrors.

Details of the calculations can be found in
http://lhocds.ligo-wa.caltech.edu:8000/40m/Upgrade_08/Optical_Layout?action=AttachFile&do=get&target=NewRecyclingCavities.zip
(Mathematica notebook)
or if you prefer PDF, here
http://lhocds.ligo-wa.caltech.edu:8000/40m/Upgrade_08/Optical_Layout?action=AttachFile&do=get&target=NewRecCav.pdf
  1274   Thu Feb 5 10:42:33 2009 YoichiUpdateGeneralDo we need off-axis parabolic mirrors ? No way !
I made a mistake in estimating the astigmatism problem.
If we use the current MMT1 as it is, this one is already an off-axis parabolic (OAP) mirror.
In this case, the astigmatism of this mirror is very small (if we use it with the correct angle). I did not include this effect in the previous calculation.
It turned out that the maximum achievable mode matching becomes far smaller (only 77%) if we use the OAP for MMT1 and a spherical mirror for MMT2.
This is not acceptable.
The reason behind this is that when we use spherical mirrors for both MMT mirrors, the astigmatism caused by the MMT1 is somewhat canceled by the astigmatism of MMT2. We don't get this cancellation if we mix OAP and spherical mirrors.

We should either (1) change MMT1 to a spherical mirror and keep the length of the input MMT as it is, or (2) change MMT1 to a spherical mirror and elongate the length of the input MMT.
In the case of (1) the maximum achievable mode matching is 94%. The focal length of MMT2 should be 315.6mm.
If we do (2), the mode matching rate can be as high as 99.8%. The focal lengths are MMT1 = -301.3mm, MMT2=558mm. The distance between the mirrors is 262mm.
We have enough space to do this elongation. But we have to mechanically modify the MMT mount.
I prefer (2).

As usual, the document on the Wiki was updated to include the above calculations.
  1290   Wed Feb 11 00:50:24 2009 carynUpdateGeneralants?

So, near 2 of the trashcans in the control room and underneath a desk there are hundrends of ants. Is this normal?

  1293   Wed Feb 11 11:39:17 2009 steveConfigurationGeneralvac envelope ground
The vacuum envelope was grounded from the IOO chamber to master ground north (under electric breaker panel L)
with 4GA  25ft red battery cable.

 

  1297   Thu Feb 12 14:39:07 2009 ranaSummaryGeneralSilicon Beam Dump test
Yesterday evening, Ken Mailand and I tested the reflectivity of a piece of polished Silicon. Since Silicon has such a high thermalconductivity (compared to stainless and fused silica) and can take much more heat than black glass and should have a very good BRDF and should absorb most of the 1064 nm light if we hit it at Brewster's angle, we want to try it out in the first version high power, low scatterbeam dump. This dump will be a 'V' style dump like what Steve has tested nearly a year ago, but the incoming beam will first hit this piece of Silicon.

The pictures of the setup and the Silicon with the beam hitting it are here.

Brewster's angle for p-pol at 1064 nm is 74.2 deg (n = 3.53 @ 1064 nm). We set up a cube polarizer on the output of the ~1064 nm CrystaLaser. 144 mW got to the Si; the reflected beam was ~1.9-2.0 mW after tuning the angle for minimum power. Via eyeball and protractor it seems that we're at ~74 deg. So the reflectivity is < 1.5-2%. This is good enough; the reflected power will be < 1 W in all cases for eLIGO and that can be absorbed by the rest of the stainless V dump. The 35 W of heat in the silicon will be mostly gotten rid of through conduction into the attached heat sink fins.

This kind of dump would go into places like the PMC-REFL, MC-REFL, & IFO-REFL, where we occasionally need to take high power, but also are sensitive to backscatter.
  1302   Fri Feb 13 16:30:49 2009 steveConfigurationGeneralstatus quo is disturbed

I have been getting ready for the annual safety inspection in the past 2-3 days.

Meaning cleaning up and disturbing the status quo on the floor  mostly under the optical tables and their surroundings.
For example: pd power supplies, He/Ne laser ps. and their positions.
BNC cables and ac power line positions can be different.
The new rule: no electronic equipment on the floor.
 
All electronic equipment were moved-placed into a plastic dish or tray.
  1331   Sun Feb 22 23:43:07 2009 carynSummaryGeneraltemperature sensor

Comparing  PSL-FSS-RMTEMP and PEM-MC1-TEMPS

So, to compare temp channels, I made a plot of PSL-FSS_RMTEMP and PEM-MC1_TEMPS(the test temp sensor channel after converting from cts to degC). This plot begins about 2 months ago t_initial=911805130. The temperature channels look kinda similar but MC1-TEMPS (the temp sensor clamped to MC1,3 chamber) is consistently higher in temperature than FSS_RMTEMP. See compare_temperature_channels.png.

MC1-TEMPS isn't exactly consistent with FSS-RMTEMP. I attached a few plots where I've zoomed in on a few hours or a few days. See compare_temperature_channels_zoom1.pdf & compare_temperature_channels_zoom2.pdf

Change the room temperature, see what happens to the chamber temperature

A while ago, somebody was fiddling around with the room temperature.  See compare_temperature_channels_zoom4.pdf.  This is a plot of PEM-MC1_TEMPS and PSL-FSS_RMTEMP at t0=911805130. You can see the chamber heating up and cooling down in happy-capacitory-fashion. Although, the PSL-FSS_RMTEMP and the PEM-MC1_TEMPS don't really line up so well. Maybe, the air in the location of the MC1,3 chamber is just warmer than the air in the PSL or maybe there's an offset in my calibration equation.

Calibration equation for PEM-MC1-TEMPS

For the calibration (cts to degC) I used the following equation based on the data-sheet for the LM34 and some measurements of the circuit:

TEMPERATURE[degC]=5/9*(((-CTS/16384/451.9/1.04094)-(.0499*10^-3))/(20*10^-6)-35);

How does the chamber temperature compare with the air temperature?

It looks like the chamber may be warmer than the air around it sometimes.

I wanted to check the temperature of the air and compare it with the temperature the sensor had been measuring. So, at t=918855087 gps, I took the temp sensor off of the mc1-mc3 chamber and let it hang freely, close to the chamber but not touching anything. See compare_temperature_chamber_air.png. MC1_TEMPS increases in temperature when I am handling the temp-sensor and then cools down to below the chamber temperature, close to FSS_RMTEMP, indicating the air temperature was less than the chamber temperature.

 When, I reattached temp sensor to the chamber at t=919011131 gps, the the temperature of the chamber was again higher than the temperature of the air. See compare_temperature_air2chamber.pdf.

Also, as one might expect, when the temp-sensor is clamped to the chamber, the temperature varies less, & when it's detached from the chamber, the temperature varies more. See compare_temperature_air_1day.pdf & compare_temperature_chamber_1day.pdf.

New temp-sensor power supply vs old temp-sensor power supply

The new temp-sensor is less noisy and seems to work OK. It's not completely consistent with PSL-FSS_RMTEMP, but neither was the old temp-sensor. And even the air just outside the chamber isn't the same temperature as the chamber. So, the channels shouldn't line up perfectly anyways.

I unplugged the 'old' temp-sensor power supply for a few hours and plugged in the 'new' one, which doesn't have a box but has some capacitors and and 2 more voltage regulators. The MC1_TEMPS channel became less noisy. See noisetime.png & noisefreq.pdf. For that time, the minute trend shows that with the old temp-sensor power supply the temp sensor varies +/-30cts and with the new power supply, it is more like +/-5cts (and Volt/16,384cts * 1degF/10mV -->  apprx +/-0.03degF). So, it's less noisy. 

I kept the new temp-sensor power supply plugged in for about 8 hours, checking if new temp sensor power supply worked ok. Compared it with PSL-FSS_RMTEMP after applying an approximate calibration equation. See ver2_mc1_rmtemp_8hr_appxcal.png.

Just for kicks

Measuring time constant of temp sensor when detached from chamber. At 918858981, I heated up the temp sensor on of the mc1-mc3 chamber with my hand. Took hand off sensor at  918859253 and let it cool down to the room temperature. See temperature_sensor_tau.pdf. 

Attachment 1: compare_temperature_channels.png
compare_temperature_channels.png
Attachment 2: compare_temperature_channels_zoom1.pdf
compare_temperature_channels_zoom1.pdf
Attachment 3: compare_temperature_channels_zoom2.pdf
compare_temperature_channels_zoom2.pdf
Attachment 4: compare_temperature_channels_zoom4.pdf
compare_temperature_channels_zoom4.pdf
Attachment 5: compare_temperature_chamber_air.png
compare_temperature_chamber_air.png
Attachment 6: compare_temperature_air2chamber.pdf
compare_temperature_air2chamber.pdf
Attachment 7: compare_temperature_air_1day.pdf
compare_temperature_air_1day.pdf
Attachment 8: compare_temperature_chamber_1day.pdf
compare_temperature_chamber_1day.pdf
Attachment 9: noisetime.pdf
noisetime.pdf
Attachment 10: noisefreq.pdf
noisefreq.pdf
Attachment 11: ver2_mc1_rmtemp_8hr_appxcal.pdf
ver2_mc1_rmtemp_8hr_appxcal.pdf
Attachment 12: temperature_sensor_tau.pdf
temperature_sensor_tau.pdf
  1340   Thu Feb 26 19:20:08 2009 YoichiConfigurationGeneralETMX camera centered. POX, POY PDs centered
Alberto, Yoichi

We centered the ETMX camera.
Alberto centered the POX and POY PDs.
We also updated the offset values of PD3 and PD4.
  1414   Fri Mar 20 15:54:29 2009 steveOmnistructureGeneral480V crane power switch on MEZ

CES Mezzanine is beeing rebuilt to accommodate our new neighbor: the 20ft high water slide...& .jacuzzi

All our ac power transformers are up there. Yesterday we labelled the power switch of 480VAC on the mezz

that we need to keep to run the 3 cranes in the lab.

  1446   Mon Mar 30 17:02:46 2009 YoichiConfigurationGeneralAP OSA aligned
I aligned the AP OSA, which had been mis-aligned for a while.
  1461   Wed Apr 8 18:46:50 2009 ranaConfigurationGeneralDMF, SVN, x2mc, and matlab

While waiting for the installation of the 32-bit Matlab 2009a to finish, I tried updating our seisBLRMS.m code.

Although DMF is in SVN, we forgot to check it out and so the directory where we have been doing our mods is not a working copy and our changes have not been captured: Shame.

We will probably have to wipe out the existing SVN trunk of DMF and re-import the directory after checking with Yoichi for SVN compliance.

Also wrote a script: LSC/x2mc, which will transition from regular ETM based X Arm locking to the MC2 based locking. It ran once OK, but I get a segfault on the 'trianglewave' which was trying to run the 'ezcastep' perl script which was calling 'ezcastep.bin'.

I also restarted the seisBLRMS.m on a terminal on Mafalda in the new Matlab 2009a to see if it loses its NDS connection like it did with 2007a. I also reduced the 'delay' parameter to 4 minutes and the 'interval' to 1 minute. This should be so that the total delay is now 5 minutes between seismic noise and seismic trend.

  1464   Thu Apr 9 20:56:12 2009 YoichiHowToGeneralRestore the alignment. Write elog entries.
I often find that the mirrors are left mis-aligned (like in X-arm mode) when I come in for the locking, including tonight.
As Rob stated repeatedly in the past elog, leaving the mirrors mis-aligned for a long time without a reason is an abomination.
It will cause a slow drift of the mirrors and the lock acquisition work is severely slowed down as I have to run the alignment script many times.

I also found that the GPIB-Ethernet box (named teofila) was taken away from the SR785 hooked up to the CM board.
I found it connected to Alberto's setup. Instead, another GPIB box was left on the SR785 but not connected.
I couldn't find any elog entry about this.
This is totally unacceptable.
The SR785 has been used as a very important tool for monitoring the AO path loop gain during the power up.
You can use it if you need, but you have to note it in elog.

The other GPIB box left on the SR785 had a wrong name labeled on it. It had a name "ERMINIA", but the IP address written next to the name was actually assigned to "crocetta" in the DNS server on linux1. I don't know who made the label. I put a new and correct label on it.
Now I'm using crocetta for the SR785 so Alberto can keep using teofila.

Anyway, I think recently people are lazy about elog.
Whatever work you did, please put it in the elog even if you think it is trivial.
I also would like to see more detailed elog entries from people. Many of the recent elog entries are too simple or superficial that it is hard for other people to figure out what was really done.
  1472   Fri Apr 10 19:10:53 2009 JenneUpdateGeneralXarm locked?

I don't know who left the X arm locked, but I just ran the Align Full IFO script, so everything is good in case Yoichi/someone comes in to lock the IFO this weekend.

  1504   Mon Apr 20 20:45:25 2009 ranaConfigurationGeneralSVN: project area added
I added the /cvs/cds/project/ directory to the SVN. I've noticed that we've been using target/ for code which is not
being targeted for any IOCs. This is out of line with the intention of separating real time FE code from just regular
code that we use for diagnostics or otherwise.

So please move all of your non-FE code over to project from target. And if you didn't have it in SVN at all, you
should experience level 3 shame and then import it.
  1538   Fri May 1 18:24:36 2009 AlbertoSummaryGeneraljitter of REFL beam ?
Some loud thinking.
 
For the measurement of the length of the PRC, I installed a fast photodiode in the path of the beam reflected by PRM which goes to the 199 PD on the AS table. I picked up the beam by a flipping mirror on the same table.
I have the problem that the DC power that I measure at the PD when the PRC is locked is not constant but fluctuates. This fluctuation is irregular and has a frequency of about one Hz or so. I.e. it makes the 33 Mhz line on the PD oscillate by +/- 10 dBm.
 
Since this fluctuation does not appear at the REFL 33 PD, which has a much larger surface, but also shows up on the REFL 199 PD, I suspected that it was due to the very small size of the fast PDs. If the spot is too large, I thought, the power on the PD should be affected by the beam jitter.
 
Trying to avoid any beam jitter, I placed two lenses with focal lengths one ten times the other on the optical path in such a way to reduce the spot size on my fast PD by the same factors. The DC power was still fluctuating, so I'm not sure it's beam jitter anymore.
 
SPOB is definitely not constant when the PRC is normally locked, even with high loop gains, so maybe the reflected power really fluctuates that much.
Although, if it's actually the DC power that is fluctuating, shouldn't it appear also at the REFL 33 and shouldn't it be a problem that it shows up also in REFL 199? The elog doesn't say anything about that.
 

It's crucial that I get a stable transmitted power to have an accurate measurement of the PRC transmissivity and thus of its macroscopic length.

  1687   Fri Jun 19 13:39:29 2009 AidanUpdateGeneralUpper limit measurement of the scatter from the eLIGO beam dumps.

 

 

I measured the scatter from the eLIGO beam dumps as best I could. The experiment setup is shown in the attached diagram. 

 

After familiarizing myself with the equipment in the morning I noticed three issues with the setup

 

1 - around the minimum scatter the back scatter from the beam dump is very susceptible to the incident angle (makes sense since the Si plate inside the beam dump at Brewster's angle when there is minimum scatter).

2 - The mirrored plug (Part 20 in D0900095) which is suppose to be used for alignment is not very effective. It moves around too much in its hole in the front face of the beam dump. Just by touching it I could make the reflected beam jump around by about 0.1 radians.

- I think to align these properly we'll have to partly assemble the dumps. If we leave off the front plate of the horn then we can measure the reflection off the Si. If we measure this with a power meter then alignment becomes a simple matter of rotating until this reflection is minimized.

3. - For this measurement the incident beam was a small (~ 1mm diameter) central beam with a small amount of spray of laser light beyond that central region. This spray was hitting the aluminium front face of the beam dump and was scattering back to the photodiode. This was clearly the limiting factor in the measurement. Most of this light was spread horizontally so I placed a couple of pieces of black glass on either side of the aperture, just blocking the edges a little. This reduce the background reading at the minimum scatter from 17.0uV to around 4.5uV with still a little bit of light hitting the top and bottom of beam dump face.

 

The incident power on the beam dump fluctuated a little but was in the range 20.5 to 22mW. The response of the PD is approximately 0.2 A/W and the transimpedance is 7.5E4 V/A.

 

The SR830 Sensitivity was set to 1x1 mV.

 

It was difficult to measure the actual angle of incidence. The dump pivoted about a point directly under the input aperture at the front. By measuring the displacement of a point on the back of the dump as I rotated it and knowing the distance between this point and the pivot point I was able to make a reasonably accurate measurement of a range of angles about the minimum.

 

The measured scatter (in V measured directly by the PD and as a fraction of the incident power) is shown in the attached plots.

 

I think I can do a better job cleaning up the incident beam - so these numbers only represent an upper limit on the scatter.

 

attachment 1: beam dump assembly

attachment 2: experimental layout

attachment 3: scatter measurement

attachment 4: BRDF - (scatter divided by the solid angle = 1.1 m steradians)

attachment 5: (slightly blurred )photo of dump - overhead view 

Attachment 1: D0900095_ELIGO_35_WATT_AIR_COOLED_BEAM_DUMP_3INCH_P.POL-3.PDF
D0900095_ELIGO_35_WATT_AIR_COOLED_BEAM_DUMP_3INCH_P.POL-3.PDF
Attachment 2: beam_dump_expt.png
beam_dump_expt.png
Attachment 3: scatter_measurement1.pdf
scatter_measurement1.pdf
Attachment 4: BRDF1.pdf
BRDF1.pdf
Attachment 5: IMG_0308.JPG
IMG_0308.JPG
  1694   Wed Jun 24 10:53:34 2009 Chris ZimmermanUpdateGeneralWeek 1/2 Update

I've spent most of the last week doing background reading; fourier transforms, shm, e&m, and other physics that I didn't cover at school.  I also read a few chapters in Saulson, especially the chapter on noise and shot noise.  To get a better grip on what I'm going to be doing I read through the polarization chapter in Hobbs' "Optics" text, mostly on wave plates since that's a large part of this readout.  Since then I've been working up to calculating the shot noise, starting with the electric field throughout the new interferometer readout.

  1695   Wed Jun 24 11:20:40 2009 StephanieUpdateGeneralMultiply Resonant EOM Update

I have created the attached EOM circuit with resonances at 11 MHz, 29.5 MHz, and 55 MHz (the magnitude and phase of the voltage across the EOM are shown in the attached plot). The gain is roughly the same for each resonant peak. Although I have managed to get the impedances at all of the resonant frequencies to equal each other, I am having more trouble getting the impedances to be 50 Ohms (they are currently all around 0.66 Ohms).

For the current circuit, initial calculations show that we will need around 4.7 - 14.2 A of current to drive the EOM at the desired voltage (8 - 24 V); this is much higher than the current rating of most of the available transformers (250 mA), but the necessary current will change as the impedance of the circuit is corrected, so this is probably not a cause for concern. For example, the necessary driving voltages for the current circuit are (2.8 - 8.5 V); if we assume that the 50-Ohm impedance will be purely resistive, then we get a current range of 56 - 170 mA.

Attachment 1: EOM_CktDiagram.JPG
EOM_CktDiagram.JPG
Attachment 2: EOM_VoltagePlot.JPG
EOM_VoltagePlot.JPG
  1710   Wed Jul 1 10:56:42 2009 Chris ZimmermanUpdateGeneralWeek 2/3 Update

I spent the last week working a lot with the differences between a basic Michelson readout and the new one as a displacement sensor.  The new one (w/ wave plates) ends with two differently polarized beams and should have better sensitivity; I've also been going through noise/sensitivity calculations for each, although that hit a road block when I had to start the 1st SURF progress report, which has taken up most of my time since Saturday.

  1711   Wed Jul 1 11:00:52 2009 StephanieUpdateGeneralMultiply Resonant EOM Update

Since last week, I have come up with a new circuit, which is shown in the attached figure. The magnitude (solid) and phase (dashed) of the voltage across the EOM (red), the ratio between the voltage across the EOM and the voltage across the primary nodes of the transformer (blue), and the impedance through the primary port of the transformer (red) are also shown in an attached figure. As can be seen on the plot, resonance occurs at 11 MHz, 29.5 MHz, and 55 MHz, as specified. Also, at these resonant frequencies, the impedance is about 50 Ohms (34 dB). The gain between the voltage across the EOM and the voltage across the primary nodes of the transformer (or output of the crystal oscillator) is about 12 dB; we'd like a higher gain than this, but this gain is primarily governed by the ratio between the secondary and primary inductances in the transformer, and we are using the largest available ratio (on the Coilcraft website) that has the necessary bandwidth. Because of this, we will likely have to add another component between the crystal oscillator and the EOM circuit, to get the voltage to the desired 8.5 Vp across the EOM (for an optical modulation depth of 0.1 rad).

The current and power through the primary port of the tranformer are 43-85 mA and 25-92 mW, respectively. Since the transformer ratings are 250 mA and 1/4 W for current and power; these values should be safe to use with the intended transformer. Also, the highest power dissipated by a resistor in the circuit (not including the 50 Ohm resistor that is part of the crystal oscillator setup) is around 74 mW.

Attachment 1: EOMCKT.png
EOMCKT.png
Attachment 2: PR1_VoltagePlot.pdf
PR1_VoltagePlot.pdf
  1719   Wed Jul 8 10:56:04 2009 StephanieUpdateGeneralMultiply Resonant EOM Update

This week, I've been working on adapting the last week's circuit to make it buildable. Mostly this has involved picking components that are already in the lab, adding tunable components when necessary, and planning roughly how the components should be laid out on a board. I then built the circuit and put it in a box with BNC connectors for easy connection during testing. A picture of the built circuit is attached.

For initial testing, the transformer was removed from the design; since this changed the response of the circuit, I added two resistors to correct the response. A figure showing a schematic of the built circuit is attached. The expected responce of the circuit is also shown; the magnitude (solid) and phase (dashed) of the voltage across the EOM are shown in green, and the impedance of the circuit is shown in blue. While this response has sharp peaks and 50 Ohms (34 dB) of impedance at resonances, the gain is low compared to the circuit with the transformer. This means that, as is, this circuit cannot be used to drive the EOM; it is simply for testing purposes.

Attachment 1: DSC_0566.JPG
DSC_0566.JPG
Attachment 2: InitialBuiltCkt.pdf
InitialBuiltCkt.pdf
Attachment 3: BuiltCkt_ExpectedResponse.png
BuiltCkt_ExpectedResponse.png
  1720   Wed Jul 8 11:05:40 2009 Chris ZimmermanUpdateGeneralWeek 3/4 Update

The last week I've spent mostly working on calculating shot noise and other sensitivities in three michelson sensor setups, the standard michelson, the "long range" michelson (with wave plates), and the proposed EUCLID setup.  The goal is to show that there is some inherent advantage to the latter two setups as displacement sensors.  This involved looking into polarization and optics a lot more, so I've been spending a lot of time on that also.  For example, the displacement sensitivity/shot noise on the standard michelson is around 6:805*10^-17 m/rHz at L_=1*10^-7m, as shown in the graph.  NSD_Displacement.png

  1734   Sun Jul 12 23:14:56 2009 JenneOmnistructureGeneralWeb screenshots aren't being updated

Before heading back to the 40m to check on the computer situation, I thought I'd check the web screenshots page that Kakeru worked on, and it looks like none of the screens have been updated since June 1st.  I don't know what the story is on that one, or how to fix it, but it'd be handy if it were fixed.

  1748   Wed Jul 15 12:11:17 2009 StephanieUpdateGeneralMultiply Resonant EOM Update

This week I've been working on testing the first version of the prototype circuit. Initially, I tested the circuit that I built last week, which had resistors in the place of the transformer. The magnitude and phase of the transfer function, as measured by the Agilent 4395A, are shown in the attached plot (first plot, MeasuredTransferFunction_R.jpg). The transfer function doesn't look like the simulated transfer function (second plot, BuiltCkt_ExpectedResponse.png), but I think I see the three peaks at least (although they're at the wrong frequencies). I spent some time trying to recreate the actual transfer function using LTSpice, and I think it's reasonable that the unexpected response could be created by extra inductance, resistance, capacitance and interaction between components.

When the transformer arrived  yesterday, I replaced the resistors in the circuit with the transformer, and I have measured the following response (last plot, MeasuredTransferFunction.jpg). The gain is much lower than for the circuit with the resistors; however, I am still trying to track down loose connections, since the measured transfer function seems very sensitive to jiggled wires and connections.

Meanwhile, the parts for a flying-component prototype circuit have been ordered, and when they arrive, I'll build that to see if it works a little better.

Attachment 1: MeasuredTransferFunction_R.jpg
MeasuredTransferFunction_R.jpg
Attachment 2: BuiltCkt_ExpectedResponse.png
BuiltCkt_ExpectedResponse.png
Attachment 3: MeasuredTransferFunction.jpg
MeasuredTransferFunction.jpg
  1750   Wed Jul 15 12:44:28 2009 Chris ZimmermanUpdateGeneralWeek 4/5 Update

I've spent most of the last week working on finishing up the UCSD calculations, comparing it to the EUCLID design, and thinking about getting started with a prototype and modelling in MATLAB.  Attached is something on EUCLID/UCSD sensors.

Attachment 1: Comparison.pdf
Comparison.pdf Comparison.pdf
  1754   Wed Jul 15 18:35:11 2009 StephanieUpdateGeneralMultiply Resonant EOM Update

Using FET probes, I was able to measure a transfer function that looks a little more like what I expected. There are only two peaks, but I think this can be explained by a short between the two capacitors (and two tunable capacitors) in the LC pairs, as shown (in red) in the circuit diagram attached. The measured transfer function (black), along with the simulated transfer functions with (red) and without (blue) the short are shown in the attached plot. The measured transfer function doesn't look exactly like the simulated transfer function with the short, but I think the difference can be explained by stray impedances.

Attachment 1: BuiltCkt1_Final.png
BuiltCkt1_Final.png
Attachment 2: BuiltCkt1_TransferFunctions.png
BuiltCkt1_TransferFunctions.png
  1762   Sun Jul 19 22:38:24 2009 robOmnistructureGeneralWeb screenshots aren't being updated

Quote:

Before heading back to the 40m to check on the computer situation, I thought I'd check the web screenshots page that Kakeru worked on, and it looks like none of the screens have been updated since June 1st.  I don't know what the story is on that one, or how to fix it, but it'd be handy if it were fixed.

 Apparently I broke this when I added op540m to the webstatus page.  It's fixed now.

  1775   Wed Jul 22 11:08:36 2009 StephanieUpdateGeneralMultiply Resonant EOM Update

I have built a version of the circuit with flying components; the completed circuit is shown in the attached picture. I built the circuit in segments and measured the transfer function after each segment to see whether it matched the LTSpice simulation after each step. The segments are shown in the circuit diagram.

After building the first segment, the measured transfer function looked pretty much the same as the simulated transfer function; it appears shifted in the attached plot, but this is because I didn't do a careful job of tuning at this point, and I'm relatively sure that I could have tuned it to match the simulation. After adding the second segment of the circuit, the measured and simulated transfer functions were similar in shape, but I was unable to increase the frequency of the peaks (through tuning) any more than what is shown in the plot (I could move the peaks so that their frequency was lower, but they are shown as high as they will go). When I added the final segment to complete the circuit, the measured and simulated transfer functions no longer had the same shape; two of the peaks were very close together and I was barely able to differentiate one from the other.

In order to understand what was happening, I tried making modifications to the LTSpice model to recreate the transfer function that was measured. I was able to create a transfer function that closely resembles the measured transfer function in both the circuit as of the 2nd segment and the completed circuit by adding extra inductance and capacitance as shown in red in the circuit diagram. The transfer functions simulated with these parasitic components are shown in red in both plots. While I was able to recreate the response of the circuit, the inductance and capacitance needed to do this were much larger than I would expect to occur naturally within the circuit (2.2uH, 12 pF). I'm not sure what's going on with this.

Attachment 1: BuiltCkt_Picture.png
BuiltCkt_Picture.png
Attachment 2: BuiltCkt2_Final.png
BuiltCkt2_Final.png
Attachment 3: 1stSegment.png
1stSegment.png
Attachment 4: 2ndSegment_ExtraL.png
2ndSegment_ExtraL.png
Attachment 5: Complete_ExtraL.png
Complete_ExtraL.png
  1779   Wed Jul 22 16:15:52 2009 Chris ZimmermanUpdateGeneralWeek 5/6 Update

The last week I've started setting up the HeNe laser on the PSL table and doing some basic measurements (Beam waist, etc) with the beam scan, shown on the graph.  Today I moved a few steering mirrors that steve showed me from at table on the NW corner to the PSL table.  The goal setup is shown below, based on the UCSD setup.  Also, I found something that confused me in the EUCLID setup, a  pair of quarter wave plates in the arm of their interferometer, so I've been working out how they organized that to get the results that they did.  I also finished calculating the shot noise levels in the basic and UCSD models, and those are also shown below (at 633nm, 4mw) where the two phase-shifted elements (green/red) are the UCSD outputs, in quadrature (the legend is difficult to read).

 

 

Attachment 1: Beam_Scan.jpg
Beam_Scan.jpg
Attachment 2: Long_Range_Michelson_Setup_1_-_Actual.png
Long_Range_Michelson_Setup_1_-_Actual.png
Attachment 3: NSD_Displacement.png
NSD_Displacement.png
  1787   Fri Jul 24 17:47:52 2009 StephanieUpdateGeneralMultiply Resonant EOM Update

After speaking with Rana and realizing that it would be better to use smaller inductances in the flying-component circuit (and after a lot of tinkering with the original), I rebuilt the circuit, removing all of the resistors (to simplify it) and making the necessary inductance and capacitance changes. A picture of the circuit is attached, as is a circuit diagram.

A plot of the measured and simulated transfer functions is also attached; the general shape matches between the two, and the resonant frequencies are roughly correct (they should be 11, 29.5, and 55 MHz). The gain at the 55 MHz peak is lower than the other two peaks (I'd like them all to be roughly the same). I currently have no idea what the impedance is doing, but I'm certain it is not 50 Ohms at the resonant peaks, because there are no resistors in the circuit to correct the impedance. Next, I'll have to add the resistors and see what happens.

Attachment 1: BuiltCkt2_Picture_Simplified.png
BuiltCkt2_Picture_Simplified.png
Attachment 2: BuiltCkt2_Simplified.png
BuiltCkt2_Simplified.png
Attachment 3: Simplified.png
Simplified.png
  1789   Sat Jul 25 13:34:58 2009 KojiUpdateGeneralWeek 5/6 Update

Quote:

The last week I've started setting up the HeNe laser on the PSL table and doing some basic measurements (Beam waist, etc) with the beam scan, shown on the graph.  Today I moved a few steering mirrors that steve showed me from at table on the NW corner to the PSL table.  The goal setup is shown below, based on the UCSD setup.  Also, I found something that confused me in the EUCLID setup, a  pair of quarter wave plates in the arm of their interferometer, so I've been working out how they organized that to get the results that they did.  I also finished calculating the shot noise levels in the basic and UCSD models, and those are also shown below (at 633nm, 4mw) where the two phase-shifted elements (green/red) are the UCSD outputs, in quadrature (the legend is difficult to read).

 

 

Chris,

Some comments:

0. Probably, you are working on the SP table, not on the PSL table.

1. The profile measurement looks very nice.

2. You can simplify the optical layout if you consider the following issues
  A. The matching lenses just after the laser:
      You can make a collimated beam only with a single lens, instead of two.
      Just put a lens of f0 with distance of f0 from the waist. (Just like Geometrical Optics to make a parallel-going beam.)

      Or even you don't need any lens. In this case, whole optical setup should be smaller so that your beam
      can be accomodated by the aperture of your optics. But that's adequately possible.

  B. The steering mirrors after the laser:
      If you have a well elevated beam from the table (3~4 inches), you can omit two steering mirrors.
      If you have a laser beam whose tilte can not be corrected by the laser mount, you can add a mirror to fix it.

  C. The steering mirrors in the arms:
      You don't need the steering mirrors in the arms as all d.o.f. of the Michelson alignment can be adjusted
      by the beamsplitter and the mirror at the reflected arm. Also The arm can be much shorter (5~6 inches?)

  D. The lenses and the mirrors after the PBS:
      You can put one of the lenses before the PBS, instead of two after the lens.
      You can omit the mirror at the reflection side of the PBS as the PBS mount should have alignment adjustment.

The simpler, the faster and the easier to work with!
Cheers.

  1790   Sat Jul 25 13:49:28 2009 KojiUpdateGeneralMultiply Resonant EOM Update

Quote:

After speaking with Rana and realizing that it would be better to use smaller inductances in the flying-component circuit (and after a lot of tinkering with the original), I rebuilt the circuit, removing all of the resistors (to simplify it) and making the necessary inductance and capacitance changes. A picture of the circuit is attached, as is a circuit diagram.

A plot of the measured and simulated transfer functions is also attached; the general shape matches between the two, and the resonant frequencies are roughly correct (they should be 11, 29.5, and 55 MHz). The gain at the 55 MHz peak is lower than the other two peaks (I'd like them all to be roughly the same). I currently have no idea what the impedance is doing, but I'm certain it is not 50 Ohms at the resonant peaks, because there are no resistors in the circuit to correct the impedance. Next, I'll have to add the resistors and see what happens.

Stephanie, 

This is a quite nice measurement. Much better than the previous one.

1) For further steps, I think now you need to connect the real EOM at the end in order to incorporate
the capacitance and the loss (=resistance) of the EOM. Then you have to measure the input impedance
of the circuit. You can measure the impedance of the device at Wilson house.
(I can come with you in order to consult with Rich, if you like)

Before that you may be able to do a preparatory measurement which can be less precise than the Wilson one,
but still useful. You can measure the transfer function of the voltage across the input of this circuit,
and can convert it to the impedance. The calibration will be needed by connecting a 50Ohm resister
on the network analyzer.

2) I wonder why the model transfer function (TF) has slow phase changes at the resonance.
Is there any implicit resistances took into account in the model?

If the circuit model is formed only by reactive devices (Cs and Ls), the whole circuit has no place to dissipate (= no loss).
This means that the impedance goes infinity and zero, at the resonance and the anti-resonance, respectively.
This leads a sharp flip of the phase at these resonances and anti-resonances.

The real circuit has small losses everywhere. So, the slow phase change is reasonable.

  1804   Wed Jul 29 12:00:49 2009 StephanieUpdateGeneralMultiply Resonant EOM Update

For the past couple of days I have been trying to understand and perform Koji's method for impedance measurement using the Agilent 4395A Network Analyzer (without the impedance testing kit). I have made some headway, but I don't completely understand what's going on; here's what I've done so far.

I have made several transfer function measurements using the attached physical setup (ImpedanceTestingPhysicalSetup.png), after calibrating the setup by placing a 50 Ohm resistor in the place of the Z in the diagram. The responses of the various impedances I've measured are shown in the attached plot (ImpResponses.png). However, I'm having trouble figuring out how to convert these responses to impedances, so I tried to derive the relationship between the measured transfer function and the impedance by simplifying the diagram Koji drew on the board for me (attached, ImpedanceTestingSetup.png) to the attached circuit diagram (ImpedanceTestingCktDiagram.png), and finding the expected value of VA/VR. For the circuit diagram shown, the equation should be VA/VR = 2Z/(50+Z). 50 Ohms is good to use for calibration because the expected value of the transfer function for this impedance is 1 (0 dB).

So I used this relationship to find the expected response for the various impedances, and I also calculated the impedance from the actual measured responses. I've attached a plot of the measured (red) and expected (black) response (top) and impedance (bottom) for a 1 nF capacitor (1nF.png). The expected and measured plots don't really match up very well; if I add extra inductance (7.6 nH, plots shown in blue), the two plots match up a little better, but still don't match very well. I suspect that the difference may come from the fact that for my analysis, I treated the power splitter as if it were a simple node, and I think that's probably not very accurate.

Anyway, the point of all this is to eventually measure the impedance of the circuit I created on Friday, but I don't think I can really do that until I understand what is going on a little better.

Attachment 1: ImpedanceTestingPhysicalSetup.png
ImpedanceTestingPhysicalSetup.png
Attachment 2: ImpResponses.png
ImpResponses.png
Attachment 3: ImpedanceTestingSetup.png
ImpedanceTestingSetup.png
Attachment 4: ImpedanceTestingCktDiagram.png
ImpedanceTestingCktDiagram.png
Attachment 5: 1nF.png
1nF.png
  1810   Wed Jul 29 19:41:58 2009 ChrisConfigurationGeneralEUCLID-setup configuration change

David and I were thinking about changing the non-polarizing beam splitter in the EUCLID setup from 50/50 to 33/66 (ref picture).  It serves as a) a pickoff to sample the input power and b) a splitter to send the returning beam to a photodetector 2 (it then hits a polarizer and half of this is lost.  By changing the reflectivity to 66% then less (1/3 instead of 1/2) of the power coming into it would be "lost" at the ref photodetector 1, and on the return trip less would be lost at the polarizer (1/6 instead of 1/4).

 

 

Attachment 1: EUCLID.png
EUCLID.png
  1813   Thu Jul 30 19:55:23 2009 KojiUpdateGeneralMultiply Resonant EOM Update

Quote:

For the past couple of days I have been trying to understand and perform Koji's method for impedance measurement using the Agilent 4395A Network Analyzer (without the impedance testing kit). I have made some headway, but I don't completely understand what's going on; here's what I've done so far.

I have made several transfer function measurements using the attached physical setup (ImpedanceTestingPhysicalSetup.png), after calibrating the setup by placing a 50 Ohm resistor in the place of the Z in the diagram. The responses of the various impedances I've measured are shown in the attached plot (ImpResponses.png). However, I'm having trouble figuring out how to convert these responses to impedances, so I tried to derive the relationship between the measured transfer function and the impedance by simplifying the diagram Koji drew on the board for me (attached, ImpedanceTestingSetup.png) to the attached circuit diagram (ImpedanceTestingCktDiagram.png), and finding the expected value of VA/VR. For the circuit diagram shown, the equation should be VA/VR = 2Z/(50+Z). 50 Ohms is good to use for calibration because the expected value of the transfer function for this impedance is 1 (0 dB).

So I used this relationship to find the expected response for the various impedances, and I also calculated the impedance from the actual measured responses. I've attached a plot of the measured (red) and expected (black) response (top) and impedance (bottom) for a 1 nF capacitor (1nF.png). The expected and measured plots don't really match up very well; if I add extra inductance (7.6 nH, plots shown in blue), the two plots match up a little better, but still don't match very well. I suspect that the difference may come from the fact that for my analysis, I treated the power splitter as if it were a simple node, and I think that's probably not very accurate.

Anyway, the point of all this is to eventually measure the impedance of the circuit I created on Friday, but I don't think I can really do that until I understand what is going on a little better.

 I checked the setup and found RF reflection at the load was the cause of the unreasonable response in the impedance measurement.
So, I have put a total 22dB attenuation (10+6+6 dB) between the power splitter and the load to be measured. See the picture.
This kind of attenuators, called as PADs, is generally used in order to improve the impedance matching, sacrificing the signal amplitude at the load.

Then, It looks the measurements got reasonable up to 100MHz (at least) and |Z|<1kOhm.
For the measurements, I just followed the procedure that Stephanie described.
Stephanie has measured the impedance of her resonant circuit.


As a test of the method, I measured impedances of various discrete devices. i.e. 50Ohm, 10-1000pF Cap, Inductances, circuit opened.

a) 50Ohm (marine-blue) was calibrated to be recognized as 50Ohm.

b) The mica capacitances (orange 10pF, yellow 100pF, green 1000pF) appeared as the impedances f^-1 in the low freq region. It's nice.
At high frequency, the impedances deviate from f^-1, which could be caused by the lead inductance. (Self Resonance)
So 1000pF mica is not capacitance at 50MHz already.

c) Open BNC connector (Red) looks have something like 5pF. (i.e. 300Ohm at 100MHz)

d) I could not get good measurements with the inductors as I had 200nH (and some C of ~5pF) for a Pomona clip (blue).
This is just because of my laziness such that I avoid soldering the Ls to an RF connector!

Attachment 1: imepedance.png
imepedance.png
Attachment 2: impedance_meas.jpg
impedance_meas.jpg
  1815   Fri Jul 31 09:52:38 2009 StephanieUpdateGeneralMultiply Resonant EOM Update

I was able to make an impedance measurement of the flying-component circuit using Koji's method for impedance measurement. I first measured the impedance of the circuit with a 10 pF capacitor in the place of the EOM (as shown in the circuit diagram). This impedance plot is attached. I then added resistance to adjust the impedance slightly, attached the circuit to a New Focus KTP 4064 EOM, and took another impedance measurement (circuit diagram and impedance plot attached). The peaks are relatively close to 50 Ohms; they are at least the same order of magnitude.

Attachment 1: BuiltCkt2_Simplified_EOM.png
BuiltCkt2_Simplified_EOM.png
Attachment 2: ImpedanceAG4395A_with10pF.png
ImpedanceAG4395A_with10pF.png
Attachment 3: BuiltCkt2_Simplified_EOM_R.png
BuiltCkt2_Simplified_EOM_R.png
Attachment 4: ImpedanceAG4395A_withEOM.png
ImpedanceAG4395A_withEOM.png
  1816   Fri Jul 31 11:04:42 2009 StephanieUpdateGeneralMultiply Resonant EOM Update

I put the flying-component circuit in a box; a photo is attached. I also measured the impedance; it looks exactly the same as it looked before I put the circuit in the box.

Attachment 1: BoxPic.png
BoxPic.png
Attachment 2: BoxPic2.png
BoxPic2.png
  1834   Wed Aug 5 11:49:49 2009 StephanieUpdateGeneralMultiply Resonant EOM Update

I have spent the past couple of days gathering optics and mounts so that I can observe the modulation of the EOM attached to the circuit I built using the optical spectrum analyzer (OSA). A rough diagram of the planned layout is attached.

I also built a short SMA cable so that the EOM did not have to be connected directly to the circuit box. The cable is shown attached to the EOM and circuit box in the attached photo. After checking to make sure that all of the connections in the cable were sound, I remeasured the input impedance of the circuit; the impedance measurement (black) is shown in the attached plot with the impedance before the SMA cable was added with and without the box (green and blue, respectively--these two are almost identical). The new impedance has a strange shape compared to the original measurements; I'd like to understand this a little better, since adding extra inductance in LTSpice doesn't seem to have that effect. Since I had already taken apart the setup used for the previous impedance measurements, I had to rebuild and recalibrate the setup; I guess the difference could be something about the new calibration, but I don't really think that that's the case.

Attachment 1: OSASetup.png
OSASetup.png
Attachment 2: SMAPic.png
SMAPic.png
Attachment 3: WithSMA.png
WithSMA.png
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