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ID Date Authorup Type Category Subject
  16772   Tue Apr 12 09:05:21 2022 JordanUpdateVACNew Pressure Gauge Install/Pump Spool Vent

Today, Tega and I would like to vent the pump spool an dinstall the new FRG-400 Agilent Pressure Gauges (per elog 15703). The attached picture shows the volume needed to be vented highlighted in red, and the gauges that need to be replaced/removed (purple dot next to the name).

The vent plan is as follows:

Open RV2

Open VM3

Open V7

Open V4

Shut down TP2

Install new gauges

Will add to post with updates post vent.

Attachment 1: Screenshot_2022-04-12_08-42-33.png
Screenshot_2022-04-12_08-42-33.png
Attachment 2: 81CB0936-1B19-4722-8A32-C3DC1D1FBC21.heic
Attachment 3: 2262ECEF-6200-4E95-8E32-C83CB9EB4F17.heic
Attachment 4: B5712B34-ECF6-43BE-BCB2-38CD775CF653.heic
Attachment 5: BEE14A07-976A-45C2-82A0-1774D377941E.heic
Attachment 6: 84557D6E-6AAE-47CF-A3AD-1DF329FEB550.heic
  16777   Thu Apr 14 09:04:30 2022 JordanUpdateVACRGA Volume RGA Scans

Prior to venting the RGA volume on Tuesday (4/12/2022) I took an RGA scan of the volume to be vented (RGA+TP1 volume+Manual Gate Valve) to see if there was a difference after replacing the manual gate valve. Attached is the plot from 4/12/22, and an overlay plot to complare 4/12/22 to 12/10/2021, when the same volume was scanned with the old (defective) manual gate valve.

There is a significant drop in the ratio O2 compared the the nitrogen peak and reduced Argon (AMU 40) which indicates there is no longer a large air leak.

12/10/21 N2/O2 ratio ~ 4 (Air 78%N2 / 21%O2)

4/12/22 N2/O2 ratio ~ 10      

There is one significant (above noise level) peak above AMU 46, which is at AMU 58. This could possibly be acetone (AMU 43 and 58) but overall the new RGA Volume scans look significantly better after the manual gate valve replacement. Well done!

Attachment 1: 40mRGA_Overlay.pdf
40mRGA_Overlay.pdf
Attachment 2: RGAVolume_4_12_22.PNG
RGAVolume_4_12_22.PNG
  16806   Fri Apr 22 14:14:33 2022 JordanUpdateVACTP3 Forepump tip seal replacement

Jordan, JC

While the pumpspool is vented, I thought it would be a convenient time to change out the tip seal on the TP3 forepump. This one had not been changed since 2018, so as preventative maintence I had JC remove the pump and begin cleaning/installing the new tip seal.

Unfortunately the tip seal broke, but I have ordered another. We should have this pump ready to go late next week. If one is needed sooner, there is a spare IDP 7 pump we can install as the TP3 forepump.

Attachment 1: IMG_0572.jpeg
IMG_0572.jpeg
Attachment 2: IMG_0573.jpeg
IMG_0573.jpeg
  16822   Mon May 2 10:00:34 2022 JordanUpdateVACTP3 Forepump tip seal replacement

[JC, Jordan]

Jordan recieved the new tip seal Friday afternoon and I continued the replacement process in the morning. Finishing up, we proceeded to test the pump in the Clean and Bake room. The pump's pressure lowered to 110 mTorr, and we continue pumping so the seal can recieve a good fitting.

Update: We have confirmed the pump is working great and have reinstalled this back into the vacuum system.                                                                                                                   Note: The same O-Rings were used.

Quote:

Jordan, JC

While the pumpspool is vented, I thought it would be a convenient time to change out the tip seal on the TP3 forepump. This one had not been changed since 2018, so as preventative maintence I had JC remove the pump and begin cleaning/installing the new tip seal.

Unfortunately the tip seal broke, but I have ordered another. We should have this pump ready to go late next week. If one is needed sooner, there is a spare IDP 7 pump we can install as the TP3 forepump.

 

  10279   Sat Jul 26 15:30:15 2014 Joseph AreedaUpdateComputer Scripts / ProgramsNDS2 server propem on megatron

The NDS2 server on megatron was unresponsive for what i think was the last couple of days.

The NDS the log file (~nds2mgr/logs/nds2-201407151045.log) started reporting "Stage: parser output queue is full." at 2014.7.24 14:47:54 also there are 16 connections still not closed with LindmeierLaptop.cacr.caltech.edu (131.215.146.102) with 15 of them in CLOSE_WAIT. 

To identify these zombie sockets we use "netstat -an | grep 31200"

The server was in a condition that /etc/init.d/nds2 stop didn't work and the process had to be manually kill -9'ed and then about 3 or 4 minutes later the zombie sockets were gone at /etc/init.d/nds2 start was used to restart the server.

The LindemejerLaptop was using pynds to get a bunch of channels at once to test drive a streaming visualization code for glitches.  It's unclear whether this bumped into a server limitation.  We have seen similar states in ldvw that seem to be the result of errors which result in client-server connections not being closed properly, leaving data in an output buffer causing Linux to wait for the other side to empty the buffer.

  5254   Wed Aug 17 12:14:27 2011 Josh SmithOmnistructureComputer Scripts / Programs40m summary page plans

Josh Smith, Fabian Magana-Sandoval, Jackie Lee (Fullerton)

Thanks to Jamie and Jenne for the tour and the input on the pages.

We had a look at the GEO summary pages and thought about how best to make a 40m summary page that would eventually become and aligo summary page. Here's a rough plan:

- First we'll check that we can access the 40m NDS2 server to get data from the 40m lab in Fullerton.

- We'll make a first draft of a 40m summary page in python, using pynds, and base the layout on the current geo summary pages.

- When this takes shape we'll iterate with Jamie, Jenne, Rana to get more ideas for measurements, layout.

Other suggestions: Jenne is working on an automated noisebudget and suggests having a placeholder for it on the page. We can also incorporate some of the features of Aidan's 40m overview medm screen that's in progress, possibly with different plots corresponding to different parts of the drawing, etc. Jenne also will email us the link of once per hour medm screenshots.

 

  1221   Fri Jan 9 17:30:10 2009 KakeruUpdateComputersSnapshots of MEDM screens
I wrote a web page which shows snapshots of MEDM screens generated by Yoich's script (e-log #1206).
https://nodus.ligo.caltech.edu:30889/medm/screenshot.html
This page refreshes itself every 5 minutes automatically.

The .html file is generated by /cvs/cds/caltech/statScreen/bin/genHtml.pl
This script generates the .html file contains snapshots listed on /cvs/cds/caltech/statScreen/etc/medmScreens.txt every 5 minutes with cron.
When you wont to display other screens, please edit this .txt file and wait 5 minutes!


To make thumbnails, I wrote /cvs/cds/caltech/statScreen/bin/genThumbnail.pl
This script reads /cvs/cds/caltech/statScreen/etc/medmScreens.txt, too.
(Sometimes, it makes thumbnails with larger storage...)


Quote:
I wrote scripts to take snapshots of MEDM screens in the background.
These scripts work even on a computer without a physical display attached.
You don't need to have X running.
So now the scripts run on nodus every 5 minutes from cron.
The screen shots are saved in /cvs/cds/caltech/statScreen/images/

There is a wiki page for the scripts.
http://lhocds.ligo-wa.caltech.edu:8000/40m/captureScreen.sh

Someone has to make a nice web page summarizing the captured images.
  1225   Tue Jan 13 18:59:09 2009 KakeruUpdateLSCAS CCD centering and ASDD demod phase
I tuned the demod-phase for PRCL and SRCL hand-off, but it have not been optimized enoughly.
I continue this work tomorrow.


Quote:
After Rob's AS beam work, I centered the beam on the AS CCD.
I also optimized the ASDD demod-phase for the MICH signal.
Rob suggested to me that whenever we restart or change the frequency of the DD Marconis, we have to re-optimize the demod-phase
because the initial phase of the Marconi is random. We had the power failure, so it was time to do so.
I confirmed that MICH hand-off from REFL33Q to AS133DDQ is ok.
I will do the same thing for the PRCL, SRCL hand-offs.
  1241   Wed Jan 21 16:18:17 2009 KakeruUpdateLSCAS CCD centering and ASDD demod phase
I tuned the DD demod-pahse for SRM.
It was tuned as the error singnal is to be 0 when the cavity is locked.

The problem is that the good phase changes if MICH and PRM are handed to DD or not.
This may be a result of the demod-phase of these two signals are tuned to be maximise the error signal, not to be 0-offset.

I will tune these two demod-phases, and write a script to tune.


Quote:
I tuned the demod-phase for PRCL and SRCL hand-off, but it have not been optimized enoughly.
I continue this work tomorrow.


Quote:
After Rob's AS beam work, I centered the beam on the AS CCD.
I also optimized the ASDD demod-phase for the MICH signal.
Rob suggested to me that whenever we restart or change the frequency of the DD Marconis, we have to re-optimize the demod-phase
because the initial phase of the Marconi is random. We had the power failure, so it was time to do so.
I confirmed that MICH hand-off from REFL33Q to AS133DDQ is ok.
I will do the same thing for the PRCL, SRCL hand-offs.
  1249   Fri Jan 23 12:48:12 2009 KakeruUpdateoplevsarm cavity oplev calibration
I calibrated optlevs of x and y arm cavity, indipendently from Peter's work.

ITMX pit: 77 microrad/ct
ITMX yaw: 73 microrad/ct
ETMX pit: 280 microrad/ct
ETMX yaw: 263 microrad/ct

ITMY pit: 120 microrad/ct
ITMY yaw: 93 microrad/ct
ETMY pit: 280 microrad/ct
ETMY yaw: 270 microrad/ct

This result is similar to Royal's one (within 30% difference except for ETMX pit), but different from Peter's in ETMY.

The attached figure is the data and fitted curve of ITMX pit.
I took this data for 8s, with 4 Hz excitation.
Attachment 1: ITMX_pitch.png
ITMX_pitch.png
  1259   Thu Jan 29 17:24:41 2009 KakeruUpdateoplevsarm cavity oplev calibration
I calibrated optlevs again. My previous work has a lot of mistakes, so ignore it.

ITMX pit: 195 microrad/ct
ITMX yaw: 185 microrad/ct
ETMX pit: 303 microrad/ct
ETMX yaw: 296 microrad/ct

ITMY pit: 192 microrad/ct
ITMY yaw: 141 microrad/ct
ETMY pit: 294 microrad/ct
ETMY yaw: 301 microrad/ct

(For ITMY, the data is low quality)

My calcuration and Peter's(based on Royal's report) is different in two point.
i) Royal uses some geometrical factor to calibrate ITM.
ii) Royal fits data to exp(-a^2/(2*w0^2)), and I fit data to exp(-a^2/w0^2).

When I calculate with modification of these differences, my result became almost same value of Peter's one.
Now we are discussing which equation is correct.


But we must do some laser works before it...
  1262   Fri Jan 30 19:38:57 2009 KakeruUpdatePSLISS Bad
Kakeru, Peter

We try to improve ISS bord, but there isn't circuit diagram with correct parameters.
We are to measure transfar function and guess each parameter before we desogn new circuit parameters.
  1277   Fri Feb 6 09:52:35 2009 KakeruUpdatePSLCurrent shunt transfar function

I attach the transfar function of the current shunt.
There is a little gap at 10 Hz for phase, but it is a ploblem of measurement and not real one.
 

Attachment 1: TF_CS_gain.png
TF_CS_gain.png
Attachment 2: TF_CS_phase.png
TF_CS_phase.png
  1278   Fri Feb 6 09:56:11 2009 KakeruUpdatePSLISS servo transfar function

I attache the transfar function of ISS servo.

The 4th stage and variable gain amplifier has alomost same transfar function, so their lines pile up.

Attachment 1: TF_ISSservo_gain.png
TF_ISSservo_gain.png
Attachment 2: TF_ISSservo_phase.png
TF_ISSservo_phase.png
  1279   Fri Feb 6 10:46:40 2009 KakeruUpdatePSLISS servo and noise
I measured the output noise of eache stage of ISS servo, and calcurated the noise ratio between input and 
output of each stage.
Generaly, each noise ratio corresponds to their transfar function. This means servo filter works well, not 
adding extra noise.

I attache example of them.
For 2nd stage, the noise ratio is smaller than transfar function with a few factor. This is because the 
input noise is coverd by analyser's noise and ratio between output and input looks small.
This means the input noise of 2nd stage was enough small and all stage before 2nd stage work well
Attachment 1: ISS_servo_TF_noise.png
ISS_servo_TF_noise.png
  1289   Tue Feb 10 23:36:25 2009 KakeruUpdatePSLPA current and laser output
I changed the PA current and measured laser output power (monitor PD signal).
The gain of ISS is 13dB
Attached figure is the relation of PA current and the average and standard diviation of laser output.
The average of output power decreas as current increase. It looks something is wrong with PA.
When current is -0.125, 0, 0.5, ISS become ocsilating. This looks to be changed from previous measurement.

I wrote matlab code for this measurement. The code is
/cvs/cds/caltech/users/kakeru/scripts/CS_evaluate.m
This function uses
/cvs/cds/caltech/users/kakeru/scripts/moveCS.m
Attachment 1: PA_current_output.png
PA_current_output.png
  1295   Wed Feb 11 23:51:53 2009 KakeruUpdatePSLPA current and laser output
I attached a plot of ISS monitor PD and MOPA output to PA current.
The both end of PA current (26.0353[A] and 28.4144[A]) correspond to the slider value of -2.0 and 1.0 .
It looks that we must use MOPA with PA current below 27.5[A].
Attachment 1: PA_current_output.png
PA_current_output.png
  1299   Thu Feb 12 18:35:10 2009 KakeruConfigurationPSLPA current limitter


I added a PA current limiter.
It is only a voltage devider (composed with 3.09k and 1.02k resiste) between DAC and PA current adjustment input.
The output range of DAC is +/- 10[V] and  the conversion factor of PA current adjustment is 0.84[A/V] (measured value), so the PA current adjustment is limited +/- 2.1[A] ( 10[V]*1.02k/(1.02k+3.09k)*0.84[A/V] ).


Actually, the manual of the PA tells that the conversion factor is 0.25[A/V].
There is 3 possibility.
1) There are some mistakes in channels of digital system.
2) The PA manual is wrong.
  2-1) The conversion factor of current adjustment is wrong.
  2-2) The conversion factor of current monitor is wrong.
I measured the signal of current adjustment and current monitor directly, and confirm that they are consistent to the value monitord from MEDM.
Hence the PA manual must be wrong, but I don't know which factor is wrong (or both?).
If the suspect 2-2) is guilty, it means we adjust PA current with very small range.
This is a completly safety way, but a wast of resource.


Now, the slider to control current adjustment indicate the output of DAC.
I will improve this to indicate  current adjustment input, but it takes some time for me to learn about EPICS.

  1328   Fri Feb 20 01:54:18 2009 KakeruUpdateComputer Scripts / Programstdsdata might have a bug

I found a strange jump of value in my data taken with tdsdata.
I couldn't find same jump in a playback of DataViewer, so I think this is a problem of tdsdata.
Be careful when you use tdsdata!

The attached file is an example of jumped data.
I try to get data with allegra and op440m, and both has same kind of jump.
(A downsampling or interpolation may be wrong.)

Rana said there is a fixed version of tdsdata in some PC, but 64bit linux may not have.
I try it tomorrow.

Attachment 1: jumped_data.png
jumped_data.png
  1362   Thu Mar 5 23:18:38 2009 KakeruConfigurationComputerstdsdata doesn't work
I found that tdsdata doesn't work.

When I star tdsdata, he takes a few ~ 10 seconds of data, and he dies with a message "Segmentation fault".
I tried to get data for some times and some channels, and this problem was observed everytime.
I also tried tdsdata on allegra, op440m and mafalda, and it didn't work on all of them.

Yesterday, I got a new version of tdsdata (which modified the problem of Message ID: 1328) and tried to build 
thme on my directory (/cvs/cds/caltech/users/kakeru.....)
This may have some relation to this problem.
  1375   Mon Mar 9 14:57:30 2009 KakeruUpdateComputer Scripts / Programstdsdata doesn't work

I tested new tdsdata and found it was working well.

I excited C1:SUS-ITMY_SUSPIT_EXC with tdssine, and get data from C1:LSC-TRY_OUT (testpoint) and C1:SUS- ITMY_OPLEV_PERROR (recorded point) with new and old tdsdata.

With old tdsdata (/cvs/cds/caltech/apps/linux/tds/bin/tdsdata), I found some jumps of datapoint, which is a same problem with before (Attachment 1).

With new tdsdata (/cvs/cds/caltech/apps/linux/tds_090304/bin/tdsdata), there looks to be no jumps (Attachment 2; taken about 10 minutes after Attachment 1).

The problem of old tdsdata looks to be remaining even for recordedpoints.

You should use /cvs/cds/caltech/apps/linux/tds_090304/bin/tdsdata.

Quote:

Matt logged in and rebuilt the TDS stuff for us on Mafalda in /cvs/cds/caltech/apps/linux/tds_090304.

He says that he can't build his stuff on 64-bit because there's not a sanctioned 64-bit build of GDS yet.

This should have all the latest fixes in it. I tried using both the old and new code from allegra and they both are fine:

./tdsdata 16384 2 C1:IOO-MC_F > /users/rana/test.txt

I loaded the data I got with the above command and there were no data dropouts. Possibly the dropout problem is only

associated with testpoints and so we have to wait for the TP fix.

 

Attachment 1: oldtds.png
oldtds.png
Attachment 2: newtds.png
newtds.png
  1398   Thu Mar 12 20:59:04 2009 KakeruUpdateIOOMC drift is terrible
After Rana went for his dinner, I aligned periscope to make the MC output 3.2 (Attachment 1).

After that, to align WFS, I unlocked the MC, unlocked the MZ and decrease the beam power to WFS QPD, and re-centerd WFC beam.
I restored MZ and MC lock.
I enabled MC autolocker, and change C1:IOO-WFS_Gain_Slider from 0 to 0.02 to lock WFS.


Quote:
Kakeru, Rana, Yoichi

We used the SUS DRIFT MON screen to set the MC biases such that the mirrors were returned to the old OSEM values.
To do this, we set the nominals and tolerances using the appropriate scripts in the mDV/extra/C1/ directory.

We then used the MC_ALIGN screen to set the angle bias sliders.

Then Kakeru and I went to the PSL table to the periscope magic and maximize the MC transmission. Kakeru seems to
have the careful Japanese alignment touch and I am hungry, so I am leaving him to optimize the power. After he
finishes he is going to align the beam to the WFS and turn the MC autolocker back on. The x-arm is locked on a
TEM00 mode so the MC alignment is maybe OK.
Attachment 1: MCtrans090312.png
MCtrans090312.png
  1403   Sat Mar 14 22:53:12 2009 KakeruUpdateoplevsarm cavity oplev calibration
I finished a calibration of optical levers.

To calibrate oplevs, I locked appropriate cavity and tilted a mirror.
A cavity with tilted mirror decrease its arm power. So I can know how much the tilt is.
For calibration of ITMX and ETMX, I locked X arm and measured TRX.
For ETMX, ETMY and BS, I locked Y arm and measured TRY
For PRM, I locked PRC and measured SPOB
For SRM, I locked SRC and measured REFL166

I used, for example, C1:SUS-ITMX_OPLEV_PERROR as an oplev signal.

The calibration factors for each mirror is below. The attachment is figures of my fitting.
I used modified equation for ITM calibration from my last calibration, so the value become small around 30%.

ITMX Pitch: 142   microrad/counts
ITMX Yaw:   145   microrad/counts
ITMY Pitch: 257   microrad/counts
ITMY Yaw:   206   microrad/counts

ETMX Pitch: 318   microrad/counts
ETMX Yaw:   291   microrad/counts
ETMY Pitch: 309   microrad/counts
ETMY Yaw:   299   microrad/counts

BS Pitch:    70.9 microrad/counts
BS Yaw:      96.3 microrad/counts

PRM Pitch:   78.5 microrad/counts
PRM Yaw:     79.9 microrad/counts

SRM Pitch:  191   microrad/counts
SRM Yaw:    146   microrad/counts


It looks strange that ITMY, BS and SRM has different value. I think this is a fitting problem.
These data have some asymmetry and cause these 20%-30% difference.
Actually, PRM Yaw has a little asymmetry but the value doesn't differ from Pitch.
This means that this calibration factor potentially has below 30% error.
(These data are the most fine data. I think we must adjust Y arm yaw alignment. The beam spot of ETMY looks too low!)
For SRM, I couldn't get fine data because it was very sensitive to tilt and easily lose its lock.
When I tuned cavity enough, The data become almost flat, so I used detuned cavity.

It is also strange that ITMX and ITMY is different. I guess that this is caused by the difference of the QPD input. The sum of QPD is around 10000 for ITMX and around 4500 for ITMY.
The difference between BS or PRM and SRM is same, I guess. The sum of QPD input for BS and SRM is around 1500, but for SRM, it is around 10000.

I will write more detailed document and upload it with my calibration code.
Attachment 1: oplev.pdf
oplev.pdf oplev.pdf oplev.pdf
  1413   Fri Mar 20 15:37:58 2009 KakeruUpdateoplevsarm cavity oplev calibration

I calibrated several oplevs with OSEM signal as a confirmation of my fitting method the method is:

1) I tilted mirrors and get signals from oplevs (C1:SUS-XXXX_OPLEV_PERROR) and OSEM (C1:SUS-XXXX_SUS{PIT/YAW}_IN1).
2) I compared amplitudes of two signals and calculated conversion factors.
3) I calibrated factors above to microrad/counts with
i) The calibration factor of OSEM (2 V/mm)
ii) The calibration factor from count to V of OSEM; 1/16384 V/counts
iii) The shape of whitening filter of OSEM: 30, 100:3 (these values is taken from http://www.ldas-sw.ligo.caltech.edu/ilog/pub/ilog.cgi?group=40m&task=view&date_to_view=04/07/2005&anchor_to_scroll_to=2005:04:07:20:28:36-rana).
iv) The size of mirrors; 125mm for large optics and 75.5mm for small optics.


This calibration has some uncirtainties.

1) The calibration factor of OSEM looks very rough.
2) Output matrixes looks not to be normalized. It looks vary from 0.5 to 1.5 .
3) I don't know where OSEMs are put on mirrors accurately.

So, this calibration is very rough and may have uncertnty of a few factors, I could confirm my fitting calibration in orders.

From this calibration, I got calibration factors listed below.

ITMY Pit: 76 microrad/counts (257 microrad/counts with fitting method)
ITMY Yaw: 58 microrad/counts (206 microrad/counts)
BS Pit : 27 microrad/counts (70.9 microrad/counts)
PRM Yaw : 22 microrad/counts (79.9 microrad/counts)

For the other mirrors, OSEM outputs matrixes are not optimized and I couldn't get fine signals (I think this is not good!).

Each value is smaller than the value calibrated with fitting method in factor 3-4. There looks to be some systematic error, so there must be some difference in parameters used in OSEM calibration.
  1434   Thu Mar 26 09:08:18 2009 KakeruUpdateoplevsarm cavity oplev calibration
I uploaded a document about my oplev calibration.
/cvs/cds/caltech/users/kakeru/oplev_calibration/oplev.pdf

At same place I put my matlab codes for calibration.
/cvs/cds/caltech/users/kakeru/oplev_calibration/oplev_calibration.m
  1389   Wed Mar 11 21:03:51 2009 Kakeru and KiwamuUpdateIOOPSL angle QPD

Kakeru and Kiwamu

We placed a QPD on the PSL bench for PSL angle monitor.

 

Quote:

I checked a broken QPD, which was placed for PSL angle monitor, and finally I cocluded one segment of the quadrant diode was broken.

The broken segment has a offset voltage of -0.7V after 1st I-V amplifier. It means the diode segment has a current offset without any injection of light.

Tomorrow I will check a new QPD for replacement.

Kiwamu IZUMI

 

 As we mentioned before, old QPD which used to be placed is broken.

 And we put broken QPD into the "photodiodes" box under the soldering table.

 

 

  1386   Wed Mar 11 14:51:01 2009 Kakeru, Joe, RobUpdateIOOMC alignment

This morning, MC alignment was gone and MC wasn't lock.

We checked old value of pitch, yaw, and position offset of each MC mirror, and found they were jumped.

We don't know the reason of this jump, but we restore each offset value and MC backed to lock.

  1404   Sun Mar 15 21:50:29 2009 Kakeru, Kiwamu, OsamuUpdateComputersSome computers are rebooted

We found c1lsc, c1iscex, c1iscey, c1susvme, c1asc and c1sosvme are dead.
We  turned off all watchdogs and turned off all lock of suspensions.
Then, I tried to reboot these machines from terminal, but I couldn't login to all of these machines.

So, we turned off and on key switches of these machines physically, and login to them to run startup scripts.

Then we turned on all watchdogs and restored all IFO.

Now they look like they are working fine.
 

  1270   Tue Feb 3 23:44:44 2009 Kakeru, Peter, YoichiUpdatePSLISS unstability

We found that one OP-amp used in ISS servo oscillated in 10 MHz, 100mV.

Moreover, we found another OP-amp had big noise.

We guess that these oscilation or noise cause saturation in high frequency, and they effect to lower frequency to cause 

 Attached files are open loop transfar function of ISS.

The blue points are open loop TF, and the green line is product of TF of ISS servo filter and TF of current shunt TF of servo filter.

This two must be same in principle, but They have difference f<2Hz and f>5kHz.

Attachment 1: TFgain.png
TFgain.png
Attachment 2: TFphase.png
TFphase.png
  1313   Mon Feb 16 21:49:06 2009 Kakeru, RanaUpdateIOOWFS

We centerd the input of WFS QPD.

  1358   Thu Mar 5 00:06:32 2009 Kakeru, RanaUpdateIOOWFS centering
We found that the MC REFL image was no longer round and that the MCWFS DC quadrant spots were mostly
in one quadrant. So we re-centered the MCWFS beams in the following way:

1) We unlocked the MZ and adjusted the PZT voltage to keep the beam on the WFS from saturating.
2) Re-aligned the black hole beam dump to center its beam in its aperture.
3) centered the beam on the MCWFS optics and MCWFS QPD displays.
4) Relocked MC.

Below is the image of the IOO Strip tool. You can see that the MC REFL DC is now more flat. The
MC pointing has also been changed (see the MC TRANS HOR & VERT channels). The MC transmitted
light is also now more stable and higher.

We tried to center the QPD, and we found that there were a few hundred mV of dark offset for each 
quadrant of QPD. We adjusted them with this scripts:
/cvs/cds/caltech/scripts/MC/WFS/McWFS_dc_offsets
Attachment 1: IOO_graph.jpg
IOO_graph.jpg
  1376   Mon Mar 9 16:54:52 2009 Kakeru, RanaUpdateComputer Scripts / Programstdsdata doesn't work

We confirmed that new tds(/cvs/cds/caltech/apps/linux/tds_090304/) works well on linux 64, and replaced it to /cvs/cds/caltech/apps/linux/tds/

The old /cvs/cds/caltech/apps/linux/tds is put in /cvs/cds/caltech/apps/linux/tds.bak

  1283   Fri Feb 6 23:23:48 2009 Kakeru, YoichiUpdatePSLISS is fixed

Yoichi and me found that the transfar function of the current shunt changed with the current of PA.
We changed PA current and fixed the unstability of ISS.
Now, laser power is stabilized finely, with band of about 1 Hz.
Yoich will post the stabilized noise spectrum.

There looks to be some non-linear relation between PA current and  the TF of current shunt.
It had changed from the TF which we measured yesterday, so it might change again.

I try to write scripts to sweep PA current and measure the laser power and its rms automatically.
It will be apply for auto-adjustment of PA current.


Attached files are the transfar function of the current shunt with changing PA.
They have difference in lower frequency.

Attachment 1: Current_ShuntTF_gain.png
Current_ShuntTF_gain.png
Attachment 2: Current_ShuntTF_phase.png
Current_ShuntTF_phase.png
  1391   Wed Mar 11 23:41:33 2009 Kakeru, YoichiUpdateIOOWFS centering

We found the MC reflection was distorted . And WFC beam went to upward of QPD

We recentered WFC beam and these problems were fixed

  10776   Wed Dec 10 21:05:56 2014 KateUpdateSEIGuralp briefly powered down

 Kate & Jenne

About 2:30 this afternoon, we briefly powered off the Guralp (C1:PEM-SEIS_GUR1_{X,Y,Z}) in order to better align it with the other seismometers along its marked N/S direction. It had been visibly off by a few degrees. 

  3431   Tue Aug 17 23:59:46 2010 KatharineUpdateelogMaglev update

Katharine, Sharmila

Update: 
We haven't been posting in the elog regularly, for which we are very sorry.  We have been taking notes in our log books, but we ought to have posted here as well.  We apologize and now present an overview of what we've been up to.

Some time ago, we created a Simulink model to predict the response of our system, but for the model to be useful we needed to include approximately correct gains for each block in the diagram, including the magnet force and coil force gradients and OSEM "gain." We also needed to better quantify the 1x1 levitation.


Adjusting the potentiometers:

The circuit which converts current to voltage in the Quadrant maglev control has a variable resistor. This is useful as it gives us a way to zero the current when the levitated object is in the equilibrium position. It was done as follows. The output voltage from the circuit converting current to voltage is fed into the oscilloscope. The voltage values for zero and complete blockage of the LED is noted(say 2V). We adjust the resistor to make the voltage output to be V when the flag completey bolcks the LED. This gives a zero current when the flag is in the equilibrium position.

OSEM Calibration:

The OSEM works by blocking the light that goes into the photodetector from the LED by a flag. To simulate the model we had on simulink, we needed to find what the gain of the OSEM was. The gain of the OSEM is the current it gives per unit displaccement of the flag. To determine this we attached a micrometer to the OSEM flag. The micrometer was long eneough to push the flag to completey block the OSEM. We connected the output of the PD test point (which was the voltage after the photodiode current was converted into voltage) to the oscilloscope. We noted down the voltage difference in the oscilloscope with a fixed reference for different positons of the flag. From the oscilloscope output, we were able to get the PD current. We then selected a linear region of the plot of PD current vs flag position(which is usually in the middle) to fit the graph with a straight line. The slope gives the OSEM gain.

Magnet strength
    We need to know about the relative strengths of our magnets (levitated and fixed in the coil) in order to do magnet matching.  We used a Gaussmeter to measure the field from each coil magnet at  ~2 mm away from the center (the probe was fixed to an aluminum block, so that the tip had the same vertical separation for each of the four fixed plate magnets).  We labeled each of the four magnets and calculated the field at this distance to be 0.206 kG, 0.210 kG, 0.212 kG, and 0.206 kG,  respectively, for coils 1-4.  However, each measurement had a rather large uncertainty of 0.01 kG, because the field strength varied a lot with position on the magnet, and the measurements were limited by how well we could align the probe tip with the center.

Fixed Plate Magnets - magnetic field (kG)           
meas't    1        2        3        4
1       0.205    0.213    0.209    0.204
2       0.211    0.219    0.223    0.207
3       0.199    0.205    0.211    0.201
4       0.207    0.203    0.206    0.213
average 0.206    0.210    0.212    0.206
stdev   0.005    0.007    0.007    0.005

    We also planned to take the same measurements for the coil magnets.  We noted that the magnetic field varied a lot depending on the probe's location, but not in the way we would expect.  At the edges of the magnet, the field was much stronger (~2 kG) than at the center (~0.5 kG).  We initially thought this might have to do with how we were holding the probe -- for instance, if we measured the force towards the edge by moving the tip all the way across the center of the magnet, there might be some kind of integration effect which does not accurately represent the field.   However, we measured the field at the edge with the probe across the magnet and also with the probe, so this is clearly not the case.

    We also noticed that the cylindrical magnet we used for single-magnet levitation was not attracted to the coil magnets in the way we expected.    Though the cylindrical magnet was oriented so that it was strongly attracted to the coil magnet, it was attracted more to the edges than the center, so that it seemed to be repelled by the centers of the coil magnets.  Though this follows somewhat from the Gaussmeter readings, it is not the behavior we would expect when considering the coil magnets as magnetic dipoles.

Attempting single-magnet levitation for each coil:
    We attempted to levitate single magnets using all four OSEM/coil combinations.   We assembled the magnets and OSEMs using Haixing's mount, and, adjusting the height of the OSEM plate, attempted to levitate the single magnet with a flag with which we were previously successful.   This was completely unsuccessful using all of the coil magnets (and when we tried to levitate using the south magnets, we flipped the cylindrical magnet's orientation).
    Since we had already achieved this levitation, this seemed particularly wrong.  We disassembled the fixed OSEM plate in Haixing's mount and built a cursory OSEM mount, similar to the one we had used for levitation before, and did not fix it in place.  After a little experimenting with the height and position of the OSEM, we were able to achieve levitation with coils 1 and 4.
    We noted the levitation magnet separation (~4.5 mm) and the height of the OSEMs at which levitation was achieved (147 +/- 1 mm for coil 1, 146 +/- 1 mm for coil 4).  Then, we reassembled Haixing's OSEM plate and tried to levitate the cylindrical magnet at coil 1 and coil 4, respectively, adjusting the OSEM plate so that the height of the OSEM of interest was the same as when we achieved single-magnet levitation.  This was unsuccessful, which leads us to believe that there is some alignment issue between the fixed coil magnets and the OSEMs in the mount,  possibly due to the unusual field from the fixed coil magnets.
    We also were completely unable to levitate using coils 2 and 3.  Coils 1 and 4 have identical circuit paths, whereas 2 and 3 differ slightly.  With more time, we need to investigate this further.

Force-distance measurements
    We also measured the repulsive force between the cylindrical magnet and the coil magnets as a function of separation.  We fixed each of the coil magnets, individually, on a stack of sticky notes on a precision balance (the stack of sticky notes was to prevent the coil magnet from interacting with the digital balance) and zeroed the balance.  We then fixed the cylindrical magnet (oriented so that it would be repelled by the coil magnet) to a teflon rod, and mounted the rod so that we could slide it up and down a long cylindrical post.  Noting the position of the rod and cylindrical magnet, we were able to measure the repulsive force as a function of separation (see Excel graph).
    However, because the magnetic field varied so much with position on the coil magnet, there is a lot of uncertainty associated with these measurements.    We tried to keep the cylindrical magnet in the same horizontal position, but it was impossible to keep the exact position while sliding the mounted teflon rod up and down the posts.    In spite of this, we fit the linear region of this graph, near the equilibrium separation of the magnets, for a very approximate measurement of the magnetic field force gradient. The slope gives the force per unit distance of the magnet.

Coil-force measurement
    We measured the force by changing the current through the coil of wire, using a very similar setup as described above.  Since we are concerned with the magnetic force as a function of current, not separation, we fixed the teflon rod so that the cylindrical magnet and coil magnet were separated by ~4.5 mm, the approximate levitation separation of the two magnets.   We then completely blocked the OSEM with the flag, creating a maximum PD current, and measured the coil current using an oscilloscope when the LED was fully blocked and the current when we removed the flag.  At the same time, we measured the repulsive force by looking at the precision balance.
    Unfortunately, we had difficulty taking further readings, because our circuit starting behaving oddly (described below).  Otherwise, we would repeat this process by blocking the OSEM LED by various amount and measuring the change in coil current, and the corresponding reading on the precision balance.   However, the force should be linearly dependent on coil current, and we ought to know one other point: when there is no current in the coil, there should be no magnetic force from the coil to the magnet.  Using this information, we can determine the slope of magnetic force by coil current, but it's not very reliable as we have only one real data point.
    One additional aspect makes this reading questionable.  When we switched on the power supply, the reading on the precision balance changed, before we had blocked the OSEM LED at all. Since no light was blocked, theoretically no photocurrent should be coming from the PD and there should not be a coil current from the feedback, so the force should not be changing. We are not sure why this is.

Recent Circuit Behavior
    Some noise in the circuit appears to be hugely amplified when the gains of each coil are high, resulting in a high frequency signal of a few hundred kHz.  When the gains are all sufficiently high, this noise can saturate the coil current so that when PD current changes, there is no visible change in coil current.
    On Saturday, we noticed some odd behavior from the circuit.  We hooked up the oscilloscope so we could see both PD current and coil current, and were very surprised that the PD current signal was oscillating and continually changing even when no flag was inside the OSEM.   This was also affecting the coil current as well.  We thought this might be due to some component burning out in our circuit, or RC coupling somewhere, but we did not get a chance to pinpoint the origin of this problem.

Modeling
Initially we had attempted to model the force-distance treating the two cylindrical magnets as dipoles, and finding the attraction/repulsions between the four distinct poles.  However, the resulting equation did not have a maximum, which is what we got in our measured values, so it seems this is not the best approach.  We would like to try the current loop approximation.

Attachment 1: repulsiveforce.png
repulsiveforce.png
Attachment 2: OSEMcalibration.png
OSEMcalibration.png
Attachment 3: OSEMslopes.png
OSEMslopes.png
  3100   Wed Jun 23 11:25:14 2010 Katharine and SharmilaUpdateWIKI-40M UpdateMaglev

Weekly update


Lab work

We compared the magnetic field strength for 4 magnets in the original setup. The standard deviation was 3.15 G which corresponds to a variation of 2.4%. We had encountered difficulties with the stability of the Gaussmeter. The tip of the Gaussmeter was unsteady and wobbling which led to huge variations for a small change in distance. We stabilized the meter by taping it to a pencil and securing it with wire ties to an aluminum block. We then used translation stages to find the point of maximum field strength for each magnet, which allowed us much more stable readings.

Readings

We are reading and learning about feedback control systems. 

Modelling

Learning to model in Comsol. Our goals for the 1X1 model include incorporating the gravitational force in the measurements and find the distance for which attraction is the strongest, and experimenting with the mesh density and boundary conditions of the domain.

Meetings/seminars

Attended many meetings, including:
Laser safety training
SURF safety training
LIGO seminars
Journal club
LIGO experimental group meeting

  3181   Thu Jul 8 17:29:20 2010 Katharine, SharmilaUpdateelog 


Last night, we successfully connected and powered our circuit, which allowed us to test whether our OSEMs were working.  Previously, we had been unable to accomplish this because (1) we weren't driving it sufficiently high voltage, and  (2) we didn't check that the colored leads on our circuit actually corresponded to the colored ports on the power supply (they were all switched, which we are in the process of rectifying), so our circuit was improperly connected to the supply .  Unfortunately, we didn't learn this until after nearly cooking our circuit, but luckily there appears to have been no permanent damage .

Our circuit specs suggested powering it with a voltage difference of 48V, so we needed to run our circuit at a difference of at least 36-40 V.  Since our power supply only supplied a difference of up to 30V in each terminal, we combined them in order to produce a voltage of up to double that.  We decided to power our circuit with a voltage difference of 40V (+/- 20V referenced to true ground).  The current at the terminals were 0.06 and 0.13 A. 

To test our circuit, we used a multimeter to check the supplied voltage at different test points, to confirm that an appropriate input bias was given to various circuit elements.  We identified the direction of LED bias on our OSEM, and connected it to our circuit. We were extremely gratified when we looked through the IR viewer and saw that, in fact, the LED in the OSEM was glowing happily .

P7070240.JPG P7070242.JPG

We hooked up two oscilloscopes and measured the current through the coil, and also through the LED and photodiode in the OSEM.  We observed a change in the photodiode signal when we blocked the LED light, which was expected.  The signal at the PD and the LED were both sinusoidal waves around ~3 kHz.

P7070255.JPG 

P7070257.JPG

 

We then went back to our levitation setup, and crudely tried to levitate a magnet with attached flag by using our hands and adjusting the gain (though we also could have been watching the PD current).  The first flag we tried was a soldering tip; we couldn't levitate this but achieved an interesting sort of baby-step "levitation" (levitation .15) which allowed us to balance the conical flag on its tip on top of the OSEM (stable to small disturbances).  After learning that conical flags are a poor idea, we switched our flag to a smaller-radius cylindrical magnet.  We were much closer to levitating this magnet, but were unable to conclusively levitate it .

 P7070249.JPG
Current plan:

Adjust the preset resistors to stabilize feedback

Check LED drive circuit.

Finish calculating the transfer function, and hook up the circuit to the spectrum analyzer to measure it as well.

Observe the signal from the photocurrent as disturbances block the LED light.

Play with the gain of the feedback to see how it affects levitation.

 

Attachment 1: P7070254.JPG
P7070254.JPG
  3200   Mon Jul 12 21:26:02 2010 Katharine, SharmilaUpdateelogmaglev coils

The connection between our coil wires and BNC terminals was pretty awful (soldered wires broke off ) so we removed the old heat shrink and re-soldered the wires.  We then chose more appropriately sized heat shrinks (small one around each of the two soldered wires, a medium-sized shrink around the wires together, a large one covering the BNC terminal and the wire) and used the solder iron and heat gun to shrink them.

P7120276.JPG

 

 

  3234   Fri Jul 16 12:36:00 2010 Katharine, SharmilaUpdateeloglevitation

After last night's challenge (or inspiration), we levitated our magnet this morning.  Since the nice Olympus camera is not currently in the 40m, we had to use my less stellar camera, but despite the poor video quality you can still see the magnet returning to its stable equilibrium position.  Once we recover the better camera, we will post new videos.  Also, we haven't yet figured out how to put videos in line in the elog entry, so here are the youtube links:

 

levitation 1

levitation 2

 

We adjusted the gain on coil 1 so that the resistance from the pots was 57.1k (maximum gain of 101.2,).

currents from power supply, pre-levitation: 0.08 A and 0.34 A

post levitation: 0.08 A and 0.11 A


note: we're not sure why changing the gain on coil 3 changes the current through the power supply, so we'd like to investigate that next.

Attachment 1: CIMG0649.AVI
  3256   Wed Jul 21 12:03:14 2010 Katharine, SharmilaUpdateWIKI-40M Updateweekly update

This past week, we levitated our small cylindrical magnet (with the flag made from heat shrink).  Though the levitated magnet didn't appear very jittery to the eye, we looked at the PD current on the scope and could see oscillations that corresponded to the flag hitting the sides of the OSEM.  The oscillations were more pronounced as we gently hit/vibrated the lab bench, and by pounding on the bench Rana knocked the levitated magnet completely out of the setup.  So, we're currently working on building a new, stabler mount.  The biggest challenge here is fixing the OSEM in place, but we're experimenting with different optics pieces to see which is the most stable for our purposes.   Jenne taught us how to make through holes using the drill press so we can add slats of aluminum to adjust the height of the OSEM mount.  We also plan to fix some heavy plates to the bottom of our system to decrease its vibration frequency.

We also calculated the transfer function of our circuit, which seems to match the measured frequency response to within a small factor.  We're playing with Rana's Simulink models and are currently modeling our own system to determine what gains we would expect to use and get a better understanding of our circuit.


Once our system is successfully mounted stably, we plan to experimentally observe the effects of changing the gain and integrator by looking at time series measurements of the PD current, as well as using the spectrum analyzer to compare the frequency response of our system at different gain settings.

  3111   Wed Jun 23 23:55:03 2010 Katharine, Sharmila, Rana, Steve and KiwamuUpdateVACwiped the BS

Some unused optics in the BS chamber were removed. 

After that the beam splitter has been drag wiped. 

So now the BS chamber is waiting for the installation of  the other core optics i.e. PRM, SRM and Tip-Tilts. 

 

-- removing of unused optics

      There were some unused optics, mainly 1.5 inch optics which had been used for the oplevs in the chamber. 

Kathaine, Shamila (Team Magnet) and Kiwamu took those optics out from the chamber.

And then we carefully wrapped each of them by aluminum foils and put them in some clear boxes.

In fact, before wrapping them, we gently attached lens papers on their HR surfaces such that aluminum foils can not damage it.

Now there are only three 1.5 inch optics in the chamber, and they are supposed to be used for the oplevs.

We didn't remove any of the 2 inch optics and the PZT mirrors because they are still going to be used.

These are the pictures of the BS chamber after we cleaned up them. 

 

-- wiping of the BS

        Rana and Kiwamu drag wiped the HR surface of the BS by using lens paper with the solvents.

The below is the procedure we did. You can find some details about the wiping technique for suspended optics in this entry.

In this time we could wipe the beam splitter without removing the front earthquake stops because the beam splitter was brought close enough to us. 

 

(1). put some blocks attaching the edge of the bottom plate of the tower in order to record the original position.

(2).  locked the beam splitter to the frame by screwing the earthquake stops.

(3). made sure if it is really locked by seeing the output signal of the OSEMs in dataviewer. If it's locked successfully, the resonant frequency gets higher and the Q-value gets lower.

(3).  moved the BS tower close to the door in order to reach the beam splitter easily.

(4). inspected the surface by using a fiber light. There were about 10 bright spots on the HR surface.

(5). wiped the surface three times by using the lens paper with Aceton.

(6). wiped it several times with Isopropyl.

(7). inspected the surface again, found there were no big bright spots near the center. Thumbed up 

(8). put the tower back to the original place and released the beam splitter from the earthquake stops.

  5470   Mon Sep 19 21:19:25 2011 KatrinUpdateGreen LockingBroadband photodiode characterization

Another Hamasutu S3399 photodiode was tested with the electronic circuit as described in LIGO-D-1002969-v.

RF transimpedance is 1k although the DC transimpedance is 2k.

The noise level is 25pA/sqrt(Hz) which corresponds to a dark current of 1.9mA or 1.7mA in the independent measurement.

At all frequencies the noise is larger compared to Koji's measurement (see labbook page 4778).

 


In file idet_S3399.pdf the first point is not within its error bars on the fitted curved. This point corresponds to the dark noise measurement

I made this measurement again. Now it is on the fitted curve. In the previous measurement I pushed the save button a bit too early. The

averaging process has not been ready while I pushed the 'save'  button.

Dark current is 1.05mA and noise is lower than in the previous measurement.

New file are the XXX_v2.pdf files

current_noise_S3399_v2.pdf

 idet_S3399_v2.pdf

 


 idet_S3399.pdf

 current_noise_S3399.pdf

S3399_response.pdf

  5511   Thu Sep 22 01:05:28 2011 KatrinUpdateGreen LockingNew modulation frequency (Y arm)

[Kiwamu / Katrin]

 

On Wednesday, the green light was locked to the Y arm cavity.

Modulation frequency was changed from 279kHz to 178875Hz. The amplitude was changed from 10Vpp to 0.01Vpp to achieve a modulation index of 0.38. The modulation frequency was changed to minimize AM. With the new modulation frequency the laser light could still locked to the cavity.

The signal of the LO and the photodiode are multiplied by a ZAD-8 mini circuit mixer (Level 7). This mixer requires LO input is +7dBm = 1.4Vpp. Thus we put a 36dB attenuator between the LO and the PZT at the laser. PDH error signal shows lots of peaks that are most likely higher order sidebands. Thus, the next step is to work on the low-pass filter. However the SNR of the error signal has improved with the new modulation frequency. With the old mod. frequency the PDH signal was 4mVpp and the noise floor was 2mVpp.

Phase between the photodiode signal and LO is shifted by about 10 degrees. Step two is to work on a phase shifter.

 

 

  5531   Fri Sep 23 17:31:14 2011 KatrinUpdateGreen LockingStray light reduction (Y)

I inserted several beam blocks and iris on the Y arm Green table. There was/is lots of stray light because a lot of the mirrors are not under an angle of incident of 45°. Some stray light is left since couldn't find an appropriate beam block/dump due to lack of space on the table.

 

  5585   Fri Sep 30 15:22:17 2011 KatrinUpdateGreen LockingWhat happened on green YARM?

 

This is a kind of summary of what I have worked on this week.

After all the changes made last week, I could not manage to lock the green light to the cavity, but the PDH error signal looks nicer.....at least something.

 

Alignment of the light to the cavity:

  • DC level of green PD when light is non-resonating 100%
  • DC level of green PD when light resonates 75%
  • --> Not sure if this alignment is good enough
  • In comparision to last week the cavity mirrors seem to move more or my alignment is way worse than last week. The bright spot on ETMY could not be observed for more than let's say a second in the unlocked configuration.

 

Low-pass filter (LPF)

  • The PDH error signal was covered with oscillations of 3.3 kHz, 7.1 kHz and 35 kHz.
  • Measured cut-off frequency of the LPF used so far is 35 kHz
  • Designed and build a new LPF: second order, cut of frequency of 1.1 kHz (this is just the design value, haven't measured that so far)
  • With the new LPF the PDH error signal is free of the above mentioned oscillations.
  • Impedance should be checked

 

PDH error signal

  • Signal-to-noise ratio (SNR) could be improved to values between 7.8 and 11.1 (old SNR was 5 to 7)
  • Looks more like a PDH signal than with the old LPF (now just derivative of the carrier and the first order sidebands show up)
  • Amplitude of the first order sidebands are smaller than the zero order, but are still too high (about 80% of the first order), need to work on the proper value of the LO amplitude an the voltage averager

 

Phase shift between green PD signal and LO

  • Phase shift is about 1MHz
  • Tried to find a capacity that compensates the phase shift. This was not successful since the PD frequency changed every now and than by +/- 20 kHz
  5619   Tue Oct 4 20:34:20 2011 KatrinUpdateGreen Locking7kHz Peak in servo input YARM

[Kiwamu, Katrin]

As reported earlier an oscillation around 7kHz is an the PDH error signal. The lower spectrum show that there is a peak from 6-7kHz.

This peak is somehow dependent on the modulation frequency. This means the peak can be shifted to a higher frequency when the modulation frequency is increased (see for comparsion f_mod=279kHz).

If the power supply for the green PD is switched of the peak vanishes. The same happens if the LO is switched of.

servoinput.png servoinput2.png

  5623   Wed Oct 5 18:31:02 2011 KatrinUpdateGreen LockingExchanged mirror on YARM table

On the Green YARM end table the second mirror behind the laser has been exchanged.

Reason: The light is impinging on the mirror under an angle of  about 10 degrees, but the old mirror was coated for angle of incidence (aoi) of 45°.

Thus it was more like a beam splitter. The new mirror is a 1" Goock & Housego mirror which has a better performance for an aoi of 10 degree.

Realignment through Faraday Isolator and SHG cristall as well as 532nm isolator is almost finished.

  5631   Fri Oct 7 17:35:26 2011 KatrinUpdateGreen LockingPower on green YARM table

After all realignment is finished, here are the powers at several positions:

 

DSC_3496_power.JPG

  5646   Mon Oct 10 18:53:04 2011 KatrinUpdateGreen LockingMirrors whose angle of incidence is not 45

The angle of incidence of light is for some mirrors on the YARM end table different from 45° even though the mirrors are coated for 45°.

The mirrors below are useful if there are plans to replace these mirrors by properly coated ones.

 

Mirror
Angle of incidence (degree)
1st 1" mirror right after laser* 10
2nd 1" mirror right after laser 35
1st 2" steering mirror to vacuum system 15
2nd 2" steering mirror to vacuum system 28

 

* This is the new mirror as decribed on http://nodus.ligo.caltech.edu:8080/40m/5623

 

ELOG V3.1.3-