ID 
Date 
Author 
Type 
Category 
Subject 
6417

Wed Mar 14 16:33:20 2012 
keiko  Update  LSC  RAM simulation / RAM pollution plot 
In the last post, I showed that SRCL element in the MICH sensor (AS55Imich) is chaned 1% due to RAM.
Here I calculated how is this 1% residual in MICH sensor (AS55 Imich) shown in MICH sensitivity. The senario is:
(1) we assume we are canceling SRCL in MICH by feed forward first (original matrix (2,3) element).
(2) SRCL in MICH (matrix(2,3) is changed 1% due to RAM, but you keep the same feed forward with the same feedforward gain
(3) You get 1% SRCL residual motion in MICH sensor. This motion depends on how SRCL is quiet/loud. The assumed level is
Pollution level = SRCL shot noise level in SRCL sensor x SRCL closed loop TF x 1% residual .... the following plot.
AS sensor = AS55Imich  SN level 2.4e11 W/rtHz  MICH SN level 6e17 m/rtHz
SRCL sensor = AS55 ISRCL  SN level 2e11 W/rtHz  SRCL SN level 5e14 m/rtHz
Quote: 
Adding some more results with more realistic RAM level assumption.
(4) With 0.1% RAM mod index of PM (normalized by (1) )

PRCL 
MICH 
SRCL 
REFL11I 
0.99999 
0.001807 
0.000148 
AS 55 Im 
0.000822 
1.000002 
0.000475 
AS 55 Is 
1.068342 
906.968167 
1.00559



Attachment 1: Mar14pollution.png


6419

Wed Mar 14 21:01:36 2012 
keiko  Update  LSC  evolution of the sensing matrix in PRMI as a function of time 
This is the simulated signals to compare with the original post #6403
PRMI configuration, PRCL signal
[W/m] 
Simulation 
Measured 
REFL11 
575440 
~10000

REFL33 
4571 
~50 
REFL55 
288400 
~5000 
REFL165 
891 
NA 
AS55 
71 
70 
PRMI configuration, MICH signal
[W/m] 
Simulation 
Measured 
REFL11 
2290 
~600

REFL33 
36 
~4 
REFL55 
5623 
~200 
REFL165 
17 
NA 
AS55 
6456 
~200

Simulated DC REFL power is 9mW (before the attenuator). AS DC is 0.3mW.
They don't agree. I suspect the PR gain for the SBs are somehow different. It is about 40 (or a bit less) in the simulation for 11MHz.

6449

Tue Mar 27 02:18:31 2012 
keiko  Update  IOO  Beam Profile measurement: IPPOS beam 
Keiko, Rana, Suresh
Related to the beam profile of IPPOS today, we tried to measure the beam size at the ETMY point in order to estimate the input beam mode. We measured the beam size hitting at the suspension frame by a camera image, with two situations to see two "z" for beam profile.
(1) Input beam is slightly misaligned and the injected beam hits the end mirror frame. Assuming z=0 at the input mirror, this should be z=40m.
(2) Input beam hits the centre of the end mirror, and ITMY is slightly misaligned and the beam hits the end mirror frame after the oneround trip. Assuming z=0 at the ITM, this position should be z=120m.
The injected beam at the end point and the one round trip ligt at the end point should be the same size, if the input mode matches to the cavity mode. You can see if your injected light is good for the cavity or not. We compared and assumed the above two beam sizes by looking at the photo of the beam spot.
(1) (2)
Assuming the zoom factor difference by the part below the beam (shown with allow in the photos. Arbitrary unit.), the beam in (2) is smaller than expected (roughly 40%?).
However this is a very rough estimation of the beam sizes! It is difficult to assume the beam size shown on the photos! It looks smaller only because the power of (2) is smaller than of (1). I don't think we can say anything from this rough estimation. One may be able to estimate better with CCD camera instead of this normal camera.

Attachment 1: text9149.png


6452

Tue Mar 27 16:06:59 2012 
keiko  Update  IOO  Beam Profile measurement: IPPOS beam 
I changed the ETMY CCD camera angle so that we can see the suspension frame in order to repeat the same thing as yesterday. The ETMY camera is not looking at the beam or mirror right now. 
6458

Tue Mar 27 21:37:51 2012 
keiko  Configuration  IOO  Beam Profile measurement: IPPOS beam 
From the mode measurement I and Suresh have done yesterday, I calculated what beam size we expect at ETM ((1) upper Fig.1) and at ETM after one bounce ((2) lower Fig.1).
Fig.1 (Yarm)
In case of (1), we expect approximately w=6300 um (radius), and w=4800 um for onebounce spot (2) from the measured mode, see Fig.2.
Fig.2
This roughly agree with what we observed on CCD camera. See, pic1 for (1) and pic2 for (2). The spot at the ETMY (1) is larger than the onebounced spot (2). From the monitor it is difficult to assume the radius ratio. The observed spot of (2) is a bit smaller than the prediction. It could happnen when (A) the ETMY (as a lens) is slightly back of the ideal position (= the distance between the ITM and ETM is longer than 40m) (B) the real waist is farer than ITM position toward MC (I assumed roughly 5 m from Jenne's plot, but could be longer than that).
pic1 (left): beam spot hitting on the suspension frame. pic 2 (right): the onebounced beam spot hitting on the suspension frame.

Attachment 1: expsche.png


Attachment 3: mmtdrawing.png


Attachment 4: drawing.png


Attachment 5: drawing.png


Attachment 8: drawing.png


6464

Thu Mar 29 11:29:27 2012 
keiko  Update  LSC  POP22/POP110 amplifires 
Yesterday I and Kiwamu connected two amplifiers (minicircuit, ZFL1000LNB+) for POP22/110. Dataviewer can see some signals. I'll test the signal levels and freq components before the rack just in case. [Kiwamu, Keiko] 
6466

Thu Mar 29 18:42:11 2012 
keiko  Update  LSC  POP22/POP110 amplifires 
Adding two amplifiers on POP22/110, I checked the signals going to the dmod board of 22 and 110.
The signal flows: Photodetector of POP > Amp1 > Amp2 > RF splotter > bandpass filter for 22MHz / 110MHz > 22MHz / 110MHz demod board.
Here is the picture of RF spectrum just after the bandpass filter of 22MHz going to the 22MHz demod board. The signal peak at 22MHz is about 40dBm. There is a structure slightly lower than 22MHz.
The below is the RF spectrum for 110MHz branch. The peak at 110MHz is about 15dBm. The peak on the left of 110MHz is 66MHz peak.
Quote: 
Yesterday I and Kiwamu connected two amplifiers (minicircuit, ZFL1000LNB+) for POP22/110. Dataviewer can see some signals. I'll test the signal levels and freq components before the rack just in case. [Kiwamu, Keiko]


6475

Mon Apr 2 18:24:34 2012 
keiko  Update  LSC  RAM simulation for Full ifo 
I extended my RAM script from DRMI (3DoF) to the full IFO (5DoF).
Again, it calculates the operation point offsets for each DoF from the opt model with RAM. Then the position offsets are added to the model, and calculates the LSC matrix. RAM level is assumed as 0.1% of the PM modulation level, as usual, and lossless for a simple model.
Original matrix without RAM:
REFL f1 : 1.000000 0.000000 0.000008 0.000005 0.000003
AS f2 : 0.000001 1.000000 0.000005 0.003523 0.000001
POP f1 : 3956.958708 0.000183 1.000000 0.019064 0.000055
POP f2 : 32.766392 0.154433 0.072624 1.000000 0.024289
POP f2 : 922.415913 0.006625 1.488912 0.042962 1.000000
(MICH and SRCL uses the same sensor, with optimised demodulation phase for each DoF.)
Operation position offsets are:
PRCL 3.9125e11 m
SRCL 9.1250e12 m
CARM 5.0000e15 m
and no position offsets for DARM and MICH (because they are differential sensor and not affected by RAM offsets).
Resulting matrix with RAM + RAM offsets, normalised by the original matrix:
REFL f1 : 0.001663 0.000000 0.003519 0.000005 0.000003
AS f2 : 0.000004 0.514424 0.000004 0.001676 0.000001
POP f1 : 7.140984 0.001205 15.051807 0.019254 0.000417
POP f2 : 0.029112 0.319792 0.042583 1.000460 0.024298
POP f2 : 0.310318 0.014385 1.761519 0.043005 0.999819
As you can see in the second matrix, the CARM and DARM rows are completely destroyed by the RAM offsets! The signals are half reduced in the DARM case, so the mixture between DARM and MICH are about 50% degraded.
I also would like to extend this script to use the DC readout, but don't know how to calculate the postion offset for AS_DC because the error signal is not zerocrossing for AS_DC anymore. Do you have any suggestions for me?

6480

Tue Apr 3 14:11:33 2012 
keiko  Update  LSC  RAM simulation for Full ifo 
Quote: 
Quote: 
I also would like to extend this script to use the DC readout, but don't know how to calculate the postion offset for AS_DC because the error signal is not zerocrossing for AS_DC anymore. Do you have any suggestions for me?

I don't think I understand the question. AS_DC should not have a zero crossing, correct?

That's right. I calculate the offset of the operation point (when you have RAM) from the zerocrossing point of the PDH signals. I don't know how to do that for AS_DC, because it doesn't cross zero anymore anytime. 
6481

Tue Apr 3 14:17:18 2012 
keiko  Update  LSC  RAM simulation for Full ifo 
I add a flowchart drawing what the scripts do and how the scripts calculate the LSC matrix.
(1) First, you calculate the LSC matrix WITHOUT RAM or anything, just for a reference. This is the first matrix shown in the quoted post.
(2) The script calculates the LSC matrix with RAM. Also, the heterodyne signals for all 5 DoF are calculated. The signals have offsets due to the RAM effect. The operating position offsets are saved for the next round.
(3) The script calculates the LSC matrix again, with RAM plus the offset of the operation points. The matrix is shown in the last part of the quoted post.
Now I am going to check (A) LSC matrices (matrix 2, the second matrix of above chart) with different RAM levels (B) Are posoffsets degrade the CARM and DARM so much (See, the quated result below), is that true?
Quote: 
Original matrix without RAM:
REFL f1 : 1.000000 0.000000 0.000008 0.000005 0.000003
AS f2 : 0.000001 1.000000 0.000005 0.003523 0.000001
POP f1 : 3956.958708 0.000183 1.000000 0.019064 0.000055
POP f2 : 32.766392 0.154433 0.072624 1.000000 0.024289
POP f2 : 922.415913 0.006625 1.488912 0.042962 1.000000
(MICH and SRCL uses the same sensor, with optimised demodulation phase for each DoF.)
Operation position offsets are:
PRCL 3.9125e11 m
SRCL 9.1250e12 m
CARM 5.0000e15 m
and no position offsets for DARM and MICH (because they are differential sensor and not affected by RAM offsets).
Resulting matrix with RAM + RAM offsets, normalised by the original matrix:
REFL f1 : 0.001663 0.000000 0.003519 0.000005 0.000003
AS f2 : 0.000004 0.514424 0.000004 0.001676 0.000001
POP f1 : 7.140984 0.001205 15.051807 0.019254 0.000417
POP f2 : 0.029112 0.319792 0.042583 1.000460 0.024298
POP f2 : 0.310318 0.014385 1.761519 0.043005 0.999819


6482

Tue Apr 3 15:50:58 2012 
keiko  Update  LSC  RAM simulation for Full ifo 
Oops, Yesterday's results for DARM was wrong!
I got more convincing results now.
> (B) Are posoffsets degrade the CARM and DARM so much (See, the quoted result below), is that true?
Here is the new results. It does change CARM a lot, but not DARM:
Matrix1 (normalised so that the diagonals are 1):
REFL f1 : 1.000000 0.000000 0.000008 0.000005 0.000003
AS f2 : 0.000001 1.000000 0.000005 0.003523 0.000001
POP f1 : 3956.958708 0.000183 1.000000 0.019064 0.000055
POP f2 : 32.766392 0.154433 0.072624 1.000000 0.024289
POP f2 : 922.415913 0.006625 1.488912 0.042962 1.000000
(=Matrix 2)
Position offsets:
only CARM, 4.6e16 (this number changed because I increased the resolution of the calculation)
Matrix3 (normalised by matrix 1):
REFL f1 : 0.039780 0.000000 0.003656 0.000005 0.000003
AS f2 : 0.000008 1.000017 0.000005 0.003499 0.000001
POP f1 : 159.146819 0.000138 15.605155 0.019393 0.000055
POP f2 : 1.277223 0.154415 0.047344 1.000008 0.024289
POP f2 : 35.422498 0.006633 1.886454 0.042963 1.000000
 CARM got a small position offset which degrades CARM signal 2 orders of mag (still the biggest signal in the sensor, though).
 DARM was not so bad, and probably the change of the DoF mixture is mostly not changed.
 Matrices don't change only with 1e4 RAM. It changes with position offsets.
 I'll see how the matrix changes without position offsets but only with RAM effects, changing RAM levels.
 Again, above is C1 configuration, 1e4 RAM level of PM level.
Quote: 
I add a flowchart drawing what the scripts do and how the scripts calculate the LSC matrix.
(1) First, you calculate the LSC matrix WITHOUT RAM or anything, just for a reference. This is the first matrix shown in the quoted post.
(2) The script calculates the LSC matrix with RAM. Also, the PDH signals for all 5 DoF are calculated. The PDH signals have offsets due to the RAM effect. The operating position offsets are saved for the next round.
(3) The script calculates the LSC matrix again, with RAM plus the offset of the operation points. The matrix is shown in the last part of the quoted post.
Now I am going to check (A) LSC matrices (matrix 2, the second matrix of above chart) with different RAM levels (B) Are posoffsets degrade the CARM and DARM so much (See, the quated result below), is that true?


6483

Tue Apr 3 22:50:37 2012 
keiko  Update  LSC  RAM simulation for Full ifo 
Koji and Jamie suggested me to include the coupling between DoFs when I calculate the last matrix. So far, I just add all the posoffsets of 5 DoFs and recalculate the matrix again. However, once I add one DoF posoffset, it could already change the LSC matrix therefore different posoffset to the other four DoF, we must iterate this process until we get the equilibrium posoffsets for 5 DoFs.
I also noticed an error in the optical configuration file. AM mod levels were smaller than that supposed to be because of the hald power going through the AMEOMs in the MZI paths. Also I have put PMMods in the MZT path which gives the smaller mod indexes. So, smaller mod levels were applied both for PM and AM. As PMAM ratio is still kept in this, so the matrices were not very wrong, I assume. I'll modify that and post the results again. 
6486

Wed Apr 4 23:57:35 2012 
keiko  Update  LSC  RAM simulation for Full ifo 
I'm still wondering whether iteration version or simple version is closer approximation to the real situation. Sorry for few explanations here. I will try to present those on Friday.
Anyway, here is the results for both:
%*.*.*. Original matrix w/o RAM .*.*.*
REFL f1 : 1.000000 0.000000 0.000003 0.000005 0.000007
AS f2 : 0.000002 1.000000 0.000009 0.003522 0.000002
POP f1 : 3954.521443 0.000965 1.000000 0.019081 0.000152
POP f2 : 32.770726 0.154433 0.072594 1.000000 0.024284
POP f2 : 922.393978 0.006608 1.488319 0.042948 1.000000
*** Iteration ***
%*.*.*. Resulting matrix w/ RAM .*.*.*
REFL f1 : 0.039125 0.000000 0.003665 0.000005 0.000007
AS f2 : 0.000010 1.000431 0.000009 0.003500 0.000002
POP f1 : 156.420221 0.000246 15.586838 0.019406 0.000154
POP f2 : 1.255806 0.154275 0.047313 1.000008 0.024285
POP f2 : 34.814720 0.006600 1.884850 0.042950 1.000000
Offsets converged to:
PRCL = 2.1e15, MICH = 1.1e17, SRCL = 3.8e15, CARM = 2.2e16, DARM = 0
(POP CARMs became so much smaller compared with the other matrix below, because the offsets are added al of 5 DoFsl at once here.)
*** no iteration, offsets added for each DoF separately ***
REFL f1 : 0.020611 0.000000 0.003600 0.000005 0.000007
AS f2 : 0.000002 1.000000 0.000009 0.003522 0.000002
POP f1 : 1842.776419 0.000198 21.533358 0.019404 0.000132
POP f2 : 32.700639 0.153095 0.072481 0.999995 0.024360
POP f2 : 922.393862 0.006435 1.488298 0.042949 0.999982
Added offsets:
PRCL = 7.5e15, MICH = 6.25e16, SRCL = 1.4e14, CARM = 4.5e16, DARM = 0
* So far, I used to add all the offsets at once. This time I add CARM and get the CARM row, add PRCL and get the PRCL row... and so on.
I
Quote: 
Koji and Jamie suggested me to include the coupling between DoFs when I calculate the last matrix. So far, I just add all the posoffsets of 5 DoFs and recalculate the matrix again. However, once I add one DoF posoffset, it could already change the LSC matrix therefore different posoffset to the other four DoF, we must iterate this process until we get the equilibrium posoffsets for 5 DoFs.
I also noticed an error in the optical configuration file. AM mod levels were smaller than that supposed to be because of the hald power going through the AMEOMs in the MZI paths. Also I have put PMMods in the MZT path which gives the smaller mod indexes. So, smaller mod levels were applied both for PM and AM. As PMAM ratio is still kept in this, so the matrices were not very wrong, I assume. I'll modify that and post the results again.


6504

Sat Apr 7 00:31:12 2012 
keiko  Update  LSC  RAM simulation for Full ifo 
I didn't understand how CARM can be decreased 2 orderes of magnitude and PRCL can be INCREASED by such small offsets (see the matrix quoted).
Apparently it was because of an opticalspring ish effect from the "detuning" (which is actually RAM position offsets). I put two plots which are CARM and PRCL tranfer functions to REFL f1 or POP f1, when there is a slight PRCL offset (0, 1e14m, and 1e15m cases are plotted). Looking at these plots, it was not a good idea to calculate the LSC matrix in DC because they are affected by this detuning a lot. I'll try f = 150 Hz for the matrix.
Quote: 
*** Iteration ***
%*.*.*. Resulting matrix w/ RAM .*.*.*
REFL f1 : 0.039125 0.000000 0.003665 0.000005 0.000007
AS f2 : 0.000010 1.000431 0.000009 0.003500 0.000002
POP f1 : 156.420221 0.000246 15.586838 0.019406 0.000154
POP f2 : 1.255806 0.154275 0.047313 1.000008 0.024285
POP f2 : 34.814720 0.006600 1.884850 0.042950 1.000000
Offsets converged to:
PRCL = 2.1e15, MICH = 1.1e17, SRCL = 3.8e15, CARM = 2.2e16, DARM = 0


2064

Wed Oct 7 11:18:40 2009 
kiwamu  Summary  Electronics  racks of electronics 
I took the pictures of all racks of electronics yesterday, and then uploaded these pictures on the wiki.
http://lhocds.ligowa.caltech.edu:8000/40m/Electronics
You can see them by clicking "pictures" in the wiki page.

2111

Sun Oct 18 22:05:40 2009 
kiwamu  Update  LSC  LSC timing issue 
Today I made a measurement to research the LSC timitng issue as mentioned on Oct.16th.
*method
I put the triangularwave into the OMC side (OMCLSC_DRIVER_EXT) by AWG,
then looked at the transferred same signal at the LSC side (LSC_DARM_IN1) by using tdsdata.
I have compared these two signals in time domain to check whether they are the same or not.
In the ideal case it is expected that they are exactly the same.
*preliminary result
The measured data are shown in attached fig.1 and 2.
In the fig.1 it looks like they are the same signal.
However in fig.2 which is just magnified plot of fig.1, it shows a timedelay apparently between them.
The delay time is roughly ~50 micro sec.
The surprising is that the LSC signal is going beyond the OMC signal, although the OMC signal drives the LSC !!
We can say it is "negative delay"...
Anyway we can guess that the time stamp or something is wrong.
*next plan
Tomorrow I'm going to measure the transferfunction between them to see the delay more clearly.
( And I would like to fix the delay. ) 
Attachment 1: rough.png


Attachment 2: detail.png


2114

Mon Oct 19 10:00:52 2009 
kiwamu  Update  LSC  RE: LSC timing issue 
Of course I know there is a downconversion in OMC signal from 32k to 16k.
But I was just wondering if the delay comes from only downconversion.
And I can not find any significant noise in both signals because I use the triangular, which cause the higer harmonics and can hide the timing noise in frequency domain.
So I'm going to make the same measurement by using sinusoidal instead of triangular, then can see the noise in frequency domain.
Quote: 
You yourself told me that tdsdata uses some downconversion from 32k to 16k!
So, how does the downconversion appears in the measurement?
How does the difference of the sampling rate appears in the measurement?
If you like to understand the delay, you have to dig into the downconversion
issue until you get the EXACT mechanism including the filter coefficients.
AND, is the transfer function the matter now?
As far as the LSC and OMC have some firm relationship, whichever this is phase delay or advance or any kind of filering,
this will not introduce any noise. If so, this is just OK.
In my understanding, the additional noise caused by the clock jitter is the essential problem.
So, did you observe any noise from the data?
Quote: 
*preliminary result
The measured data are shown in attached fig.1 and 2.
In the fig.1 it looks like they are the same signal.
However in fig.2 which is just magnified plot of fig.1, it shows a timedelay apparently between them.
The delay time is roughly ~50 micro sec.
The surprising is that the LSC signal is going beyond the OMC signal, although the OMC signal drives the LSC !!
We can say it is "negative delay"...
Anyway we can guess that the time stamp or something is wrong.
*next plan
Tomorrow I'm going to measure the transferfunction between them to see the delay more clearly.
( And I would like to fix the delay. )



2122

Mon Oct 19 23:14:32 2009 
kiwamu  Update  LSC  LSC timing issue 
I measured the noise spectrum of LSC_DARM_IN1 and OMCLSC_DRIVE_EXC by using DTT,
while injecting the sinwave into the OMCLSC_DRIVE by AWG.
The attached are the results.
No significant differences appears between OMC and LSC in this measurement.
It means, in this measurement we can not figure out any timing noise which might be in LSCclock.
In addition there are the noise floor, whose level does not change in each 3figures. The level is about ~4*10^{8} count/sqrt[Hz]
(The source of the noise floor is still under research.) 
Attachment 1: SPE20Hz.png


Attachment 2: SPE200Hz.png


Attachment 3: SPE2kHz.png


2145

Mon Oct 26 18:49:18 2009 
kiwamu  Update  LSC  OMCLSC timing issue 
According to my measurements I conclude that LSCsignal is retarded from OMCsignal with the constant retarded time of 92usec.
It means there are no timing jitter between them. Only a constant timedelay exists.
(Timing jitter)
Let's begin with basics.
If you measure the same signal at OMCside and LSCside, they can have some time delay between them. It can be described as followers.
where tau_0 is the time delay. If the tau_0 is not constant, it causes a noise of the timing jitter.
(method)
I have injected the sinewave with 200.03Hz into the OMCLSC_DRIVE_EXC. Then by using get_data, I measured the signal at 'OMCLSC_DRIVE_OUT' and 'LSCDARM_ERR' where the exciting signal comes out.
In the ideal case the two signals are completely identical.
In order to find the delay, I calculated the difference in these signals based on the method described by Waldman. The method uses the following expression.
Here the tau_s is the artificial delay, which can be adjusted in the off line data.
By shifting tau_s we can easily find the minimal point of the RMS, and at this point we can get tau_0=tau_s.
This is the principle of the method to measure the delay. In my measurement I put T=1sec. and make the calculation every 1sec. in 1 min.
(results)
Attachment is the obtained results. The above shows the minimum RMS sampled every 1sec. and the below shows the delay in terms of number of shifts.
1 shift corresponds to Ts (=1/32kHz). All of the data are matched with 3 times shift, and all of the minimum RMS are completely zero.
Therefore I can conclude that LSCsignal is retarded from OMCsignal with constant retarded times of 3*Ts exactly, and no timing jitter has been found.

Attachment 3: OMC_LSC60sec.png


2146

Mon Oct 26 19:12:50 2009 
kiwamu  Update  LSC  diagnostic script for LSC timing 
The diagnostic script I've written is available in the 'caltech/users/kiwamu/work/20091026_OMCLSCdiag/src'.
To run the script, you can just execute 'run_OMC_LSC.sh' or just call the mfile ' OMC_LSC_timinig.m' from matlab.
NOTES:
The script destructs the lock of DARM and OMC, be careful if you are working with IFO. 
2153

Tue Oct 27 19:37:03 2009 
kiwamu  Update  LSC  cron job to diagnose LSCtiming 
I set a cron job on allegra.martian to run the diagnostic script every weekend.
I think this routine can be helpful to know how the trend of timingshift goes
The cron runs the script on every Sunday 5:01AM and diagnostics will take about 5 min.
! Important:
During the running of the script, OMC and DARM can not be locked.
If you want to lock OMC and DARM in the early morning of weekend, just log in allegra and then comment out the command by using 'crontab e'

2167

Mon Nov 2 10:56:09 2009 
kiwamu  Update  LSC  cron job works succesfully & no timing jitter 
As I wrote on Oct.27th, the cron job works every Sunday.
I found it worked well on the last Sunday (Nov.1st).
And I can not find any timing jitter in the data, its delay still stay 3*Ts. 
2169

Mon Nov 2 13:34:36 2009 
kiwamu  Configuration  PSL  removed multiply resonant EOM 
I removed the multiply resonant EOM that has been set by a SURF student from PSL table.
I will use it for checking the resonant circuit. 
2179

Thu Nov 5 12:34:26 2009 
kiwamu  Update  Computers  elog rebooted 
I found elog got crashed. I rebooted the elog daemon just 10minutes before. 
2244

Wed Nov 11 20:57:06 2009 
kiwamu  Update  Electronics  Multiresonant EOM  LC tank circuit  
I have been working about multiresonant EOM since last week.
In order to characterize the behavior of the each components, I have made a simple LC tank circuit.
You can see the picture of the circuit below.
Before constructing the circuit, I made an "ideal" calculation of the transfer function without any assumptions by my hand and pen.
Most difficult part in the calculation is the dealing with a transformer analytically. Eventually I found how to deal with it in the analytical calculation.
The comparison of the calculated and measured transfer function is attached.
It shows the resonant frequency of ~50MHz as I expected. Those are nicely matched below 50MHz !!
For the next step, I will make the model of the circuit with stray capacitors, lead inductors, ... by changing the inductance or something.

Attachment 2: LCtank_complete.png


2262

Fri Nov 13 03:38:47 2009 
kiwamu  Update  Electronics  multiresonant EOM  impedance of LC tank circuit  
I have measured the impedance of the LC tank circuit which I referred on my last entry.
The configuration of the circuit is exactly the same as that time.
In order to observe the impedance, by using Koji's technique I injected a RF signal into the output of the resonant circuit.
In addition I left the input opened, therefore the measured impedance does not include the effect of the transformer.
            results
The measured impedance is attached below; "LCtank_impedance.png"
The peak around 50MHz is the main resonance and it has impedance of ~1500 [Ohm], which should go to infinity in the ideal case (no losses).
In fact the impedance looked from the input of the circuit gets reduced by 1/n^2, where "n" is the turn ratio of the transformer.
By putting the n=4, the input impedance of the circuit should be 93 [Ohm]. This is a moderate value we can easily perform impedancematching by some technique.
I also fitted the data with a standard model of equivalent circuit (see attachment 2).
In the figure.2 red component and red letter represents the design. All the other black stuff are parasites.
But right now I have no idea the fitted value is reasonable or not.
For the next I should check the input impedance again by the direct way; putting the signal into the input.

Attachment 1: LCtank_impedance.png


Attachment 2: LCtank_model.png


2263

Fri Nov 13 05:03:09 2009 
kiwamu  Update  Electronics  multiresonant EOM  input impedance of LC tank  
I measured the input impedance of the LC tank circuit with the transformer. The result is attached.
It looks interesting because the input impedance is almost dominated
by the primary coil of the transformer with inductance of 75nH (see attachment 1).
The impedance at the resonance is ~100 [Ohm], I think this number is quite reasonable because I expected that as 93 [Ohm]
Note that the input impedance can be derived as follower;
(input impedance) = L1 + Z/n^2.
Where L1 is the inductance of the primary coil, Z is the load in the secondary loop and n is the turn ratio.
I think now I am getting ready to enter the next phase \(^o^)/ 
Attachment 1: input_impedance.png


Attachment 2: input_impedance2.png


2277

Mon Nov 16 17:35:59 2009 
kiwamu  Update  LSC  OMCLSC timing get synchronized ! 
An interesting thing was happened in the OMCLSC timing clock.
Right now the clock of the OMC and the LSC are completely synchronized.
The trend data is shown below. At the first two measurements (Oct.27 and Nov.1), LSC had constant retarded time of 3Ts (~92usec.).
The last measurement, on Nov.15, number of shifts goes to zero, this means there are no retarded time.
Also the variance between the two signal gets zero, so I conclude the OMC and the LSC are now completely synchronized.
The measurement on Nov.8 is somehow meaningless, I guess the measurement did not run correctly by an influence from megatron(?)

2292

Wed Nov 18 14:55:59 2009 
kiwamu  Update  Electronics  multiresonant EOM  circuit design  
The circuit design of multiresonant EOM have proceeded.
By using numerical method, I found the some best choice of the parameters (capacitors and inductors).
In fact there are 6 parameters (Lp, L1, L2, Cp, C1, C2) in the circuit to be determined.
In general the less parameter gives the less calculation time with performing the numerical analysis. Of course it looks 6 parameters are little bit large number.
In order to reduce the arbitrary parameters, I put 4 boundary conditions.
Each boundary conditions fixed resonant peaks and valleys; first peak=11MHz, third peak=55MHz, first valley=19MHz, second valley=44MHz.
So now the remaining arbitrary parameters successfully get reduced to 2. Only we have to do is optimize the second peak as it to be 29.5MHz.
Then I take C1 and C2 as free parameters seeing how the second peak agree with 29.5MHz by changing the value of the C1 and C2.
the red color represents the good agreement with 29.5MHz, in contrast blue contour represents the bad.
You can see some best choice along the yellow belt. Now what we should do is to examine some of that and to select one of those. 
2294

Wed Nov 18 16:58:36 2009 
kiwamu  Update  Electronics  multiresonant EOM  EOM characterization  
In designing the whole circuit it is better to know the characteristic of the EOM.
I made impedance measurement with the EOM (New Focus model 4064) and I found it has capacitance of 10pF.
This is good agreement with the data sheet which says "510pF".
The measured plot is attached below. For comparison there also plotted "open" and "10pF mica".
In the interested band( from 1MHz to 100MHz), EOM looks just a capacitor.
But indeed it has lead inductance of 12nH, resistance of 0.74[Ohm], and parasitic capacitance of 5.5pF.
In some case we have to take account of those parasites in designing.

2340

Wed Nov 25 20:44:48 2009 
kiwamu  Update  Electronics  Multiresonant EOM  Qfactor  
Now I am studying about the behavior of the Qfactor in the resonant circuit because the Qfactor of the circuit directly determine the performance as the EOM driver.
Here I summarize the fundamental which explains why Qfactor is important.

The EOM driver circuit can be approximately described as shown in figure below
Z represents the impedance of a resonant circuit.
In an ideal case, the transformer just raise the voltage level ntimes larger. Rin is the output impedance of the signal source and usually has 50[Ohm].
The transformer also makes the impedance Z 1/n^2 smaller. Therefore this configuration gives a following relation between Vin and Vout.
Where G is the gain for the voltage. And G goes to a maximum value when Rin=Z/n^{2}. This relation is shown clearly in the following plot.
Note that I put Rin=50 [Ohm] for calculating the plot.
Under the condition Rin=Z/n^{2}( generally referred as impedance matching ), the maximum gain can be expressed as;
It means that larger Z makes more efficient gain. In our case, interested Z is considered as the impedance at a resonance.
So what we should do is making a resonant circuit which has a higher impedance at the resonance (e.g. high Qresonant circuit).

2363

Tue Dec 8 03:53:49 2009 
kiwamu  Update  SUS  Free swinging spectra of ETMX 
In this night, I checked the free swinging spectra of ETMX to make sure nothing wrong with ETMX by the wiping.
Compared with the past (Aug.6 2008), the spectra of ETMX doesn't show significant change.
Successfully the wiping activity didn't change its configuration so much and didn't bring bad situations.
(bad situation means for example, the suspended components hit some others).
The spectra of ETMX by DTT are attached. Also you can see the past spectra in Yoichi's entry.
Yoichi's data was taken during the airpressure condition, so it's good for comparing.
Actually I compared those data by my eyes, because I could not get the past raw data somehow.
The resonant frequencies and their typical height changed a little bit, but I think those are not significant.
NOTE: In the figure, pitch and yaw modes (~0.57Hz and ~0.58Hz) look like having a smaller Qfactor than the past.

Attachment 1: ETMX_air.png


2368

Tue Dec 8 23:13:32 2009 
kiwamu  Update  SUS  free swinging spectra of ETMY and ITMX 
The free swinging spectra of ETMY and ITMX were taken after today's wiping, in order to check the test masses.
These data were taken under the atmospheric pressure condition, as well as the spectra of ETMX taken yesterday.
Compared with the past (see Yoichi's good summary in Aug.7 2008), there are no significant difference.
There are nothing wrong with the ETMY and ITMX successfully.

By the way I found a trend, which can be seen in all of the data taken today and yesterday.
The resonances of pitch and yaw around 0.5Hz look like being damped, because their height from the floor become lower than the past.
I don't know what goes on, but it is interesting because you can see the trend in all of the data.

Attachment 1: SUSETMY.png


Attachment 2: SUSITMX.png


2372

Wed Dec 9 17:51:03 2009 
kiwamu  Update  SUS  watchdogs 
Please do not touch the watchdogs for all SUSs except for MCs,
because I am going to measure the free swinging spectra for ITMs, ETMs, BS, PRM, SRM tonight.
Today, it is good chance to summarize those data under atmospheric pressure.
thank you.

2374

Wed Dec 9 21:09:28 2009 
kiwamu  Update  SUS  Re: free swinging spectra of ETMY and ITMX 
Okay, now the data are attached. At that time I just wanted to say like the follower.
  
In the freeswinging spectra around ~0.5Hz, you can see the two resonances, which come from pitch and yaw mode of the pendulum.
Note that, the vertical and the horizontal axis are adjusted to be the same for the two plots in the figure .
And I found that
* the floor levels are almost the same (the factor of about 1.5 or something like that) compared to the past.
* however the peak heights for two resonances are several 10 times smaller than the past.
* this tendency are shown in all of the data (ITMX, ETMX, ETMY).
If such variation of the peak heights is cased by the seismic activity, it means the seismic level change by several 10 times. It sounds large to me.
Quote: 
Where is the plot for the trend?
It can be either something very important or just a daydream of you.
We can't say anything before we see the data.
Quote: 
By the way I found a trend, which can be seen in all of the data taken today and yesterday.
The resonances of pitch and yaw around 0.5Hz look like being damped, because their height from the floor become lower than the past.
I don't know what goes on, but it is interesting because you can see the trend in all of the data.



Attachment 1: PitchYaw_modes.png


2391

Thu Dec 10 17:13:36 2009 
kiwamu  Update  SUS  Free swiging spectra under the atmospheric pressure 
The free swinging spectra of ITMs, ETMs, BS, PRM and SRM were measured last night in order to make sure that nothing wrong have happened by the wiping.
I think there are nothing wrong with ITMs, ETMs, BS, PRM and SRM successfully.
For the comparison, Yoichi's figure in his elog entry of Aug.7 2008 is good, but in his figure somehow PRM spectrum doesn't look correct.
Anyway, compared with his past data, there are no significant changes in the spectra. For PRM which has no counterpart to compare with, its shape of spectra looks similar to any other spectra. So I think PRM is also OK. The measured spectra are attached below.
Indeed the current data are still showing smaller peak height for their pitch and yaw modes (roughly factor of 10 ).

Attachment 1: summary_freeswing.pdf


2401

Fri Dec 11 17:36:37 2009 
kiwamu  Update  General  IFO restoring plan 
Alberto, Jenne, Kiwamu
We together will lead the IFO restoring and the following is our plan.
                                                     
#.0  measuring the free swinging spectra (weekend by kiwamu) DONE
#.1  turn ON the PZTs for steering mirror and so on. (Dec.14 Mon.) DONE
#. 1  lock around PSL DONE
#.2  deal with mechanical shutter (Dec.14 Mon.)DONE
#.3  lock MCs (Dec.14 Mon.)DONE
#.4  align the IFO (Dec.15 Tue.)DONE
#.5  lock full IFO (Dec.15 Tue.)DONE
                                                    
Thank you. 
2405

Sun Dec 13 17:43:10 2009 
kiwamu  Update  SUS  free swinging spectra (vacuum) 
The free swinging spectra of ITMs, ETMs, BS, PRM and SRM were measured under the vacuumcondition. The attachment are measured spectra.
It looks there are nothing wrong because no significant difference appear from the past data and the current data (under atmosperic pressure).
So everything is going well. 
Attachment 1: summary_FreeSwinging_vacuum.pdf


2446

Tue Dec 22 15:49:31 2009 
kiwamu  Update  General  elog restarted 
I found the elog has been down around 3:40pm, then I restarted the elog. Now it's working.
Thanks. 
2450

Thu Dec 24 01:25:29 2009 
kiwamu  Update  Electronics  impedance analyzing 
The validation for high impedance measurement has been well done.
The impedance measurement is one of the keys for designing the EOM circuit.
So far I was very struggling to measure the high impedance ( above several 1000 Ohm) at RF because the EOM circuit has a high impedance at its resonance.
Finally I realized that the measured impedance was suppressed by a parasitic resistance, which especially reduces the impedance at the resonance.
Also I found that we can extract the TRUE impedance data by subtracting the effect of the parasitic resistance from resultant data.
In order to confirm whether this subtraction works correctly or not, the impedance was directly remeasured with another analyzer for crosscheck.
The followers are details about the remeasurement.
(measurement )
The measurement has been performed with help from Peter and Frank. ( Thank you !)
By using network analyzer AG4395A with the impedance test kit AG43961A (these are at the PSL lab.), the impedance of resonant circuit with EOM was measured.
The picture of setup is attached. This impedance test kit allows to measure typically 0.1 [Ohm]1M [Ohm] and frequency range of 100kHz500MHz.
(result)
The resultant plot is attached. In the plot the blue curve represents the impedance measured by usual analyzer at 40m.
Note this curve is already subtracted the effect of the parasitic resistance.
( the parasitic resistance is in parallel to the circuit and it has ~7.8k Ohm, which is measured while the probe of the analyzer stays open. )
The red curve is the remeasured data using the impedance test kit.
The important point is that; these two peak values at the resonance around 40MHz show good agreement in 10%.
The resonant frequencies for two data differs a little bit, which might be the effect of a stray capacitance ( ~several [pF] )
The red curve has a structure around 80MHz, I think this comes from the noncoaxial cables, which connect the circuit and analyzing kit.
You can see these cables colored black and red in the picture.
( conclusion )
Our measurement with the subtraction of the parasitic resistance effect is working reliably ! 
Attachment 1: DSCN0421.JPG


Attachment 2: EOM.png


2453

Sun Dec 27 20:05:28 2009 
kiwamu  Update  Computers  can not communicate with frontends 
In this evening I found that fb40m has been down, then I restarted fm40m successfully.
However there still is a problem, the reflective memory can not communicate with some frontend CPUs ( such as c1iscey, c1susvme, ...etc.)
Right now I don't have any ideas about this, I am leaving them as they are now .... we can deal with them tomorrow.
The followers are what I did.
(1) ssh to fb40m then "pkill tpman"
(2) telnet to fb40m then typed "shutdown". ( These procedure are on the 40m wiki)
(3) make sure fb40m gets recovered while watching the medm screen C0DAQ_DETAIL.adl
(4) run the backup script in fb40m
(5) in order to fix the communication problem, physically turn off c1dcuepics and c0daqctrl
(6) keying some frontend CPUs. > still some of front ends indicate RED on the medm screen C0DAQ_DETAIL.adl ( figure attached )

Attachment 1: C0DAQ_DETAIL.png


2470

Wed Dec 30 22:17:07 2009 
kiwamu  Update  General  Camera input and monitor output 
The input channels of the cameras and the output channels for the monitors are summarized on the wiki.
The channel table on the wiki is very helpful when you want to make a change in the video matrix.
thank you. 
2523

Mon Jan 18 23:44:19 2010 
kiwamu  Update  Electronics  triple resonant circuit for EOM 
The first design of the triple resonant EOM circuit has been done.
If only EOM has a loss of 4 Ohm, the gain of the circuit is expected to be 11 at 55MHz
So far I've worked on investigation of the single resonant circuit and accumulated the knowledge about resonant circuits.
Then I started the next step, designing the triple resonant circuit.
Here I report the first design of the circuit and the expected gain.
( What I did )
At first in order to determine the parameters, such as inductors and capacitors, I have solved some equations with numerical ways (see the past entry).
In the calculation I put 6 boundary conditions as followers;
(first peak=11MHz, second peak=29.5MHz, third peak=55MHz, first valley=22MHz, second valley=33MHz, Cp=18pF)
The valley frequencies of 22MHz and 33MHz are chosen in order to eliminate the higher harmonics of 11MHz, and Cp of 18pF represents the capacitance of the EOM.
Basically the number of parameters to be determined is 6 ( L1, L2, ...,), therefore it is completely solved under 6 boundary conditions. And in this case, only one solution exists.
The point is calculation does not include losses because the loss does not change the resonant frequency.
( results )
As a result I obtained the 6 parameters for each components shown in the table below.
Cp [pF] 
18.1 
C1 [pF] 
45.5 
C2 [pF] 
10.0 
Lp [uH] 
2.33 
L1 [uH] 
1.15 
L2 [uH] 
2.33 
Then I inserted the loss into the EOM to see how the impedance looks like. The loss is 4 Ohm and inserted in series to the EOM. This number is based on the past measurement .
Let us recall that the gain of the impedancematched circuit with a transformer is proportional to squareroot of the peak impedance.
It is represented by G = sqrt(Zres/50) where Zres is the impedance at the resonance.
As you can see in the figure, Zres = 6.4 kOhm at 55MHz, therefore the gain will be G=11 at 55MHz.
Essentially this gain is the same as that of the single resonant circuit that I've been worked with, because its performance was also limited mainly by the EOM loss.
An interesting thing is that all three peaks are exactly on the EOM limited line (black dash line), which is represented by Zres = L/CR = 1/ (2pi f Cp)^2 R. Where R = 4 Ohm.
( next plan )
There are other solutions to create the same peaks and valleys because of the similar solution.
It is easy to understand if you put Cp' = Cp x N, the solutions must be scaled like L1'=L1/N, C1'=C1 x N, ..., Finally such scaling gives the same resonant frequencies.
So the next plan is to study the effect of losses in each components while changing the similar solution.
After the study of the loss I will select an optimum similar solution. 
2525

Tue Jan 19 02:39:57 2010 
kiwamu  Update  Electronics  design complete  triple resonant circuit for EOM  
The design of the triple resonant circuit has been fixed.
I found the optimum configuration, whose gain is still 11 at 55MHz even if there are realistic losses.
As I mentioned in the last entry, there are infinite number of the similar solutions to create the same resonant frequencies.
However owing to the effect of the losses, the resultant gain varies if the similar solution changes
The aim of this study is to select the optimum solution which has a maximum gain ( = the highest impedance at the resonance ).
In order to handle the losses in the calculation, I modeled the loss for both inductors and the capacitors.
Then I put them into the circuit, and calculated the impedance while changing the solutions.
(method)
1). put the scaling parameter as k in order to create the similar solution.
2). scale the all electrical parameters (L1, L2,...) by using k, so that C1'=C1 x k, L1'=L1/k ,...
3). Insert the losses into all the electrical components
4). Draw the impedance curve in frequency domain.
5). See how the height of the impedance at the resonance change
6). Repeat many time this procedure with another k.
7). Find and select the optimum k
There is a trick in the calculation.
I put a capacitor named Cpp in parallel to the EOM in order to scale the capacitance of the EOM (see the schematic).
For example if we choose k=2, this means all the capacitor has to be 2times larger.
For the EOM, we have to put Cpp with the same capacitance as Cp (EOM). As a result these two capacitors can be dealt together as 2 x Cp.
So that Cpp should be Cpp = (k1) Cp, and Cpp vanishes when we choose k=1.
The important point is that the scaling parameter k must be greater than unity, that is k > 1.
This restriction directly comes from Cp, the capacitance of the EOM, because we can not go to less than Cp.
If you want to put k < 1, it means you have to reduce the capacitance of the EOM somehow (like cutting the EO crystal ??)
(loss model)
I've modeled the loss for both the inductors and the capacitors in order to calculate the realistic impedance.
The model is based on the past measurements I've performed and the data sheet.
Loss for Capacitor : R(C) = 0.5 (C / 10pF)^{0.3} Ohm
Loss for Inductor : R(L) = 0.1 ( L / 1uH) Ohm
Of course this seems to be dirty and rough treatment.
But I think it's enough to express the tendency that the loss increase / decrease monotonically as L / C get increased.
These losses are inserted in series to every electrical components.
( Note that: this model depends on both the company and the product model. Here I assume use of Coilcraft inductors and mica capacitors scattered around 40m )
( results )
The optimum configuration is found when k=1, there is no scaling. This is the same configuration listed in last entry
Therefore we don't need to insert the parallel capacitor Cpp in order to achieve the optimum gain.
The figure below shows the some examples of the calculated impedance. You can see the peak height decrease by increasing the scale factor k.
The black dash line represents the EOMloss limit, which only contains the loss of the EOM.
The impedance at the resonance of 55MHz is 6.2 kOhm, which decreased by 3% from the EOMloss limit. This corresponds to gain of G = 11.
The other two peaks, 11MHz and 29.5MHz dramatically get decreased from EOMloss limit.
I guess this is because the structure below 50MHz is mainly composed by L1, L2, C1, C2.
In fact these components have big inductance and small capacitance, so that it makes lossy.
( next step )
The next step is to choose the appropriate transformer and to solder the circuit. 
2529

Tue Jan 19 03:27:47 2010 
kiwamu  Update  Electronics  Re: triple resonant circuit for EOM 
1. You are right, the gain for the single resonant circuit was about 9.3 in my measurement.
But the reason why the triple is better than the single resonant circuit comes from the transformer.
The impedance can be degraded by a loss of the transformer, because it got worse after applying the transformer in the past measurement.
Also I definitely confirmed that the circuit had the impedance of 7.2 kOhm at the resonance of 52.9MHz without the transformer.
So it shall give the gain of 12, but did not after applying the transformer.
2. Yes, I think we need some variable components just in case.
5. For the impedance matching, I will select a transformer so that 55MHz is matched. In contrast I will leave two lower resonances as they are.
This is because 11MHz and 29.5MHz usually tend to have higher impedance than 55MHz. In this case, even if the impedance is mismatched, the gain for these can be kept higher than 11.
I will post the detail for this mismatched case tomorrow.
Quote: 
The design looks very good. I have some questions.
1. As far as I remember, you've got the gain of slightly worse than 10 for a 55MHz single resonant case. Why your expectation of the gain (G=11) for the highest resonance better than this?
Supposing the loss exists only on the EOM, the other part of the LC network for the triple work as an inductor at the resonant frequency. This is just equivalent as the single resonant case. So the expected gain at 55MHz should coincides with what we already have. Probably, the resistance of 4 Ohm that is used here had too rough precision???
2. How can you adjust the resonances precisely?
Do we need any variable components for Cs and Ls, that may have worse quality than the fixed one, generally speaking.
I myself has no experience that I had to tune the commercial EOM because of a drift or whatever. I hope if you can adjust the resonance with a fixed component it should be fine.
3. Changing Cp. What does it mean?
Do you put additional cap for Cp?
4. The resonances for the lower two look very narrow. Is that fine?
This will show up in a better shape if we look at the transfer function for the gain. Is this right?
If we have BW>100kHz, it is sufficient.
5. Impedance matching for the lower two resonances.
Yep. You know this problem already.


2533

Tue Jan 19 23:26:07 2010 
kiwamu  Update  Electronics  Re:Re: triple resonant circuit for EOM 
Quote: 
5. For the impedance matching, I will select a transformer so that 55MHz is matched. In contrast I will leave two lower resonances as they are.
This is because 11MHz and 29.5MHz usually tend to have higher impedance than 55MHz. In this case, even if the impedance is mismatched, the gain for these can be kept higher than 11.
I will post the detail for this mismatched case tomorrow.

Here the technique of the impedance matching for the triple resonant circuit are explained.
In our case, the transformer should be chosen so that the impedance of the resonance at 55MHz is matched.
We are going to use the transformer to step up the voltage applied onto the EOM.
To obtain the maximum stepupgain, it is better to think about the behavior of the transformer.
When using the transformer there are two different cases practically. And each case requires different optimization technique. This is the key point.
By considering these two cases, we can finally select the most appropriate transformer and obtain the maximum gain.
( how to maximize the gain ?)
Let us consider about the transformer. The gain of the circuit by using the transformer is represented by
(1)
Where ZL is the impedance of the load (i.e. impedance of the circuit without the transformer ) and n is the turn ratio.
It is apparent that G is the function of two parameters, ZL and n. This leads to two different solutions for maximizing the gain practically.
 case.1 : The turn ratio n is fixed.
In this case, the tunable parameter is the impedance ZL. The gain as a function of ZL is shown in the left figure above.
In order to maximize the gain, Z must be as high as possible. The gain G get close to 2n when the impedance ZL goes to infinity.
There also is another important thing; If the impedance ZL is bigger than the matched impedance (i.e. ZL = 50 * n^2 ), the gain can get higher than n.
 case.2 : The impedance ZL is fixed.
In contrast to case1, once the impedance ZL is fixed, the tunable parameter is n. The gain as a function of n is shown in the right figure above.
In this case the impedance matched condition is the best solution, where ZL=50*n^2. ( indicated as red arrow in the figure )
The gain can not go higher than n somehow. This is clearly different from case1.
( Application to the triple resonant circuit )
Here we can define the goal as "all three resonances have gain of more than n, while n is set to be as high as possible"
According to consideration of case1, if each resonance has an impedance of greater than 50*n^2 (matched condition) it looks fine, but not enough in fact.
For example if we choose n=2, it corresponds to the matched impedance of 50*n^2 = 200 Ohm. Typically every three resonance has several kOhm which is clearly bigger than the matched impedance successfully.
However no matter how big impedance we try to make, the gains can not be greater than G=2n=4 for all the three resonance. This is ridiculous.
What we have to do is to choose n so that it matches the impedance of the resonance which has the smallest impedance.
In our case, usually the resonance at 55MHz tends to have the smallest impedance in those three. According to this if we choose n correctly, the other two is mismatched.
However they can still have the gain of more than n, because their impedance is bigger than the matching impedance. This can be easily understand by recalling the case1.
(expected optimum gain of designed circuit)
By using the equation (1), the expected gain of the triple resonant circuit including the losses is calculated. The parameters can be found in last entry.
The turn ratio is set as n=11, which matches the impedance of the resonance at 55MHz. Therefore 55MHz has the gain of 11.
The gain at 11MHz is bigger than n=11, this corresponds to the case1. Thus the impedance at 11MHz can go close to gain of 22, if we can make the impedance much big.

2586

Wed Feb 10 17:28:02 2010 
kiwamu  Update  Electronics  triple resonant EOM  preliminary result 
I have made a prototype circuit of the triple resonant EOM.
The attached is the measured optical response of the system.
The measured gains at the resonances are 8.6, 0.6 and 7.7 for 11MHz, 29.5MHz and 55MHz respectively.
I successfully got nice peaks at 11MHz and 55MHz. In addition resultant optical response is well matched with the predicted curve from the measured impedance.
However there is a difference from calculated response (see past entry) (i.e. more gains were expected)
Especially for the resonance of 29.5MHz, it was calculated to have gain of 10, however it's now 0.6. Therefore there must a big loss electrically around 29.5MHz.
I am going to reanalyze the impedance and model the performance in order to see what is going on. 
Attachment 1: mod_depth.png


2590

Thu Feb 11 16:52:53 2010 
kiwamu  Update  Electronics  triple resonant EOM  preliminary result 
The commercial resonant EOM of New Focus has the modulation efficiency of 50150mrad/Vrms. ( This number is only true for those EOM made from KTP such as model4063 and model4463 )
Our tripleresonant EOM (made from KTP as well) has a 90mrad/Vrms and 80mrad/Vrms at the reosonances of 11MHz and 55MHz respectively.
Therefore our EOM is as good as those of companymade so that we can establish a new EOM company
Quote: 
Hey, this looks nice, but can you provide us the comparison of rad/V with the resonant EOM of New Focus?
Quote: 
I have made a prototype circuit of the triple resonant EOM.
The attached is the measured optical response of the system.
The measured gains at the resonances are 8.6, 0.6 and 7.7 for 11MHz, 29.5MHz and 55MHz respectively.
I successfully got nice peaks at 11MHz and 55MHz. In addition resultant optical response is well matched with the predicted curve from the measured impedance.
However there is a difference from calculated response (see past entry) (i.e. more gains were expected)
Especially for the resonance of 29.5MHz, it was calculated to have gain of 10, however it's now 0.6. Therefore there must a big loss electrically around 29.5MHz.
I am going to reanalyze the impedance and model the performance in order to see what is going on.



2596

Fri Feb 12 13:15:41 2010 
kiwamu  Update  Electronics  triple resonant EOM  liniaryity test 
I have measured the linearity of our triple resonant EOM (i.e. modulation depth versus applied voltage)
The attached figure is the measured modulation depth as a function of the applied voltage.
The linear behavior is shown below 4Vrms, this is good.
Then it is slowly saturated as the applied voltage goes up above 4Vrms.
However for the resonance of 29.5MHz, it is difficult to measure below 7Vrms because of the small modulation depth.
Our triple resonant EOM looks healthy
    result from fitting   
11MHz: 91mrad/Vrms+2.0mrad
29.5MHz: 4.6mrad/Vrms+6.2mrad
55MHz:82mrad/Vrms+1.0mrad 
Attachment 1: linearity_edit.png


2601

Fri Feb 12 18:58:46 2010 
kiwamu  Update  Green Locking  take some optics away from the ETM end table 
In the last two days Steve and I took some optics away from the both ETM end table.
This is because we need an enough space to set up the green locking stuff into the end table, and also need to know how much space is available.
Optics we took away are : Alberto's RF stuff, fiber stuff and some optics obviously not in used.
The picture taken after the removing is attached. Attachment1:ETMX, Attachment2:ETMY
And the pictures taken before the removing are on the wiki, so you can check how they are changed.
http://lhocds.ligowa.caltech.edu:8000/40m/Optical_Tables 
Attachment 1: DSC_1164.JPG


Attachment 2: DSC_1172.JPG

