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ID Date Author Type Category Subject
394   Sat Mar 22 22:39:02 2008 mevansSummaryCDSDirect Form 2 filters are bad
Here I show a comparison between the filter algorithm currently used in LIGO (Direct Form II), and an alternative algorithm designed to reduce numerical noise. The input signal is

x = sin(2 * pi * t) + 1e-9 * sin(2 * pi * (fs / 4) * t);

where fs = 16384 is the sample rate. The filter is a 4th order notch at 1Hz (f_poles = f_zeros = 1Hz, Q_poles = 1, Q_zeros = 1e6). It is clear that the DF2 algorithm produces a noise floor that is, for this simple filter, 1e-11 / rtHz smaller than the input drive amplitude (see plots). That should probably be scary given how many second-order-sections we run our signals through. The low-noise form does a somewhat better job. The low-noise algorithm has the same memory and computational requirements as DF2, and our CDS guys have the code in hand. I suggest we start testing soon.

(The code is included below. You will need my Matlab library to run the top level test script.)
395   Sun Mar 23 00:43:08 2008 mevansHowToGeneralOnline Adaptive Filtering
I wrote a short document about the OAF running on the ASS. Since there is no BURT setup, I put a script in /cvs/cds/caltech/scripts to help with setting initial parameters: upass.
2728   Mon Mar 29 15:19:33 2010 mevansUpdateGreen Lockingfrequency discriminator for green PLL

Thanks for the great entry!

In order to make this work for higher frequencies, I would add Hartmut's suggestion of a frequency dividing input stage.  If we divide the input down by 100, the overall range will be about 200MHz, and the noise will be about 20Hz/rtHz.  That might be good enough... but we can hope that the commercial device is lower noise!

 Quote: Last Friday, Matt made a frequency discriminator circuit on a bread board in order to test the idea and study the noise level. I think it will work for phase lock acquisition of Green locking. As a result a response of 100kHz/V and a noise level of 2uV/rtHz @ 10Hz are yielded. This corresponds to 0.2Hz/rtHz @ 10Hz. The motivation of using frequency discriminators is that  it makes a frequency range wider and easier for lock acquisition of PLLs in green locking experiment.

4442   Fri Mar 25 01:27:29 2011 mevansFrogsGreen Lockingdigital frequency counting

Today we tried the Schmitt trigger DFD, and while it works it does not improve the noise performance.  At least part of our problem is coming from the discrete nature of our DFD algorithm, so I would propose that an industrious day job person codes up a new DFD which avoids switching.  We can probably do this by mixing the input signal (after high-passing) with a time-delayed copy of itself... as we do now, but without the comparator.  This has the disadvantage of giving an amplitude dependent output, but since we are working in the digital land we can DIVIDE.  If we mix the signal with itself (without delay) to get a rectified version, and low-pass it a little, we can use this for normalization.  The net result should be something like:

output = LP2[ s(t) * s(t - dt) / LP1[ s(t) * s(t) ]],

where s(t) is the high-passed input and LP is a low-pass filter.  Remember not to divide by zero.

6314   Fri Feb 24 16:10:48 2012 mikeUpdateComputersPyNDS and a Plot

Power Spectral Density plot using PyNDS, comparing 5 fast data channels for ETMX.

**EDIT** Script here:

import nds
import numpy as np
import matplotlib.pyplot as plt
import time
daq=nds.daq('fb', 8088)
channels=daq.recv_channel_list()
e=0
start=int(time.time()-315964819)
rqst=['C1:SUS-ETMX_SENSOR_UR','C1:SUS-ETMX_SENSOR_UL','C1:SUS-ETMX_SENSOR_LL','C1:SUS-ETMX_SENSOR_LR','C1:SUS-ETMX_SENSOR_SIDE']    #Requested Channels
for c in channels:
if c.name in rqst:
daq=nds.daq('fb', 8088)
data=daq.fetch(start-100, start, c.name)
vars()['psddata'+str(e)], vars()['psdfreq'+str(e)]=plt.psd(data[0],NFFT=16384,Fs=c.rate)
vars()['label'+str(e)]=c.name
e+=1
plt.figure(1)
plt.clf()
plt.title('PSD Comparison')
plt.grid(True, which='majorminor')
plt.xlabel(r'Frequency $Hz$')
plt.ylabel(r'Decibels $\frac{dB}{Hz}$')
for x in np.arange(0,e):
plt.loglog(psdfreq0, 10*vars()['psddata'+str(x)], label=vars()['label'+str(x)])
plt.legend()
plt.show()

3060   Wed Jun 9 19:47:08 2010 nancyUpdatePEMlead balls on concrete

Quote:

 Quote: Valera and I put the 2 Guralps and the Ranger onto the big granite slab and then put the new big yellow foam box on top of it. There is a problem with the setup. I believe that the lead balls under the slab are not sitting right. We need to cut out the tile so the thing sits directly on some steel inserts. You can see from the dataviewer trend that the horizontal directions got a lot noisier as soon as we put the things on the slab.

The tiles were cut out in 1.5" ID circle to insure that the 7/16" OD lead balls would not touch the tiles on Wednesday, May 26, 2010

Granite surface plate specifications: grade B, 18" x 24" x 3" , 139 lbs

These balls and granite plate were removed by  Rana in entry log #3018 at 5-31-2010

I tried to calculate the frequency of resonance using Rayleigh's method.  approximated the geometry of lead to be that of a perfect cylinder, and  the deformation in the lead by the deflection in a cantilever under  a shear strain.

this rough calculation gives an answer of 170Hz and depends on the dimensions of each lead, number of leads, and mass of the granite. But the flaw pointed out is that this calculation doesnot depend on the dimension of the granite slab, nor on the exact placing of the lead spheres with respect toteh COM of the slab.

I will put up the calculations details later, and also try to do a FEM analysis of the problem.

BTW, latex launched this new thing for writing pdfs. doesnot require any installations.  check  http://docs.latexlab.org

3081   Wed Jun 16 18:12:16 2010 nancyConfigurationComputers40MARS

i added my laptop's mac address to teh martian at port 13 today.

3101   Wed Jun 23 11:31:12 2010 nancyUpdateWIKI-40M UpdateWeekly Update

This week I attended a whole lot of orientations, lectures, and meetings related to SURF. Done with general and laser safety training.

read Nergis' thesis for, and other material on WFS.

got confused with how the sidebands and shifted carrier frequencies are chosen for the Interferometer, read initial chapters of Regehr's thesis for teh same.

Made a plan for proceeding with the WFS work through discussions with Koji.

Understood the MC cavity and drew a diagram for it and the sensors.

Did Calculations for Electric field amplitudes inside and outside the MC cavity.

Saw the hardware of the WFS and QPD inside, and their routes to computers. Figured out which computer shows up the conditioned data from teh sensors.

Tried calculating the cavity axis for MC using geometry and ray tracing. Too complicated to be done manually.

Read some material (mainly Seigman) for physics of calculating the eigen-axis of the MC cavity with mirrors mis-aligned. Will calculate that using simulations, using the ABCD matrices approach.

in the night, Made a simulink model of the sensor-mirror thing, with transfer functions for everything as dummy TFs. Compiles, shows signals in time. Remaining part is to put in real/near-real TFs in the model.

3143   Wed Jun 30 11:39:20 2010 nancyUpdateWIKI-40M UpdateWeekly Update

Wednesday Morning E-log :

Most of the time through this week, i was working towards making the simulink model work.

It involved learning simulink functions better, and also improving on the knowledge of control theory in general, and control theory of our system.

1. Thusrday : found tfs for the feedback loop. and tried many different filters and gains to stabilize the system (using the transient response of the system). - not through

2. Friday : decided to use error response and nullify the steady state error instead of looking at convergence of output. tried many other filter functions for that.

Rana then showed me his files for WFS.

3. Sunday - played with rana's files, learnt how to club simluink with matlab, and also about how to plot tfs using bode plots in matlab.

4. Monday : Read about state-space models, and also how to linearize in matlab. done with the latter, but the former still needs deeper understanding.

read ray-optics theory to calculate the geometric sensing matrix.

It first requires to calculate the eigen mode of the cavity with tilted mirrors. this eigen mode is needed to be found out using ray-optics transfer matrices for the optics involved  . figured out  matrices for the tilted plane mirrors, and am working on computing the same for MC2.

5. Tuesday : went to Universal Studios , Hollywood :P

6. Wednesday (today) : Writing the report to be submitted to SFP.

3168   Wed Jul 7 12:45:00 2010 nancyUpdate Weekly Update

Wednesday after the meeting - Started report, learnt mode cleaner locking from Kiwamu and Rana, saw how to move optics on the tables with Rana and kiwamu.

Tuesday - report.

Today - am trying locking the MC with kiwamu's help to see the WFS signals and also to start characterizing the QPD.

3174   Wed Jul 7 22:58:08 2010 nancyUpdateIOOMC alignment values.

Nancy and Koji:

This is what I and Koji measured after aligning the MC in the afternoon.

MC_Trans 4.595 (avg)

MC_Refl 0.203 (avg)

MC2_trans :

power = 1.34mW

13.5% width : x=6747.8 +- 20.7 um  , y = 6699.4+- 20.7 um

3182   Thu Jul 8 19:43:16 2010 nancyUpdateIOOWFS calculations

The WFS error signals were recorded in the order

WFS1_PIT

WFS1_YAW

WFS2_PIT

WFS2_YAW

these measurements are made in the linear region, that is the MC is nearly perfectly aligned.

This is  the average and std. dev.of 5 measurements taken of the same signals over 10 secs each. The std. dev are under 10%. And hence, I will be using 10 secs for measurements for the WFS signals after perturbations to the mirrors.

avg =

829.4408
-517.1884
297.4168
-944.7892

std_dev =

9.0506
22.9317
15.4580
8.9827

I perturbed the Pitch and Yaw of the Three mirrors (in order MC1,2,3), using ezcastep and calculated the coefficients that relate these perturbations to the WFS error signals.

The perturbation made is of -0.01 in each dof , and after measuring the WFS error for it, the system is reverted back to the previous point before making the other perturbation.

I was able to calculate the coefficients since I have assumed a linear relationship..

Following are the coefficients calculated using 10 secs measurements

coef_mat =

1.0e+05 *

MC1_P   MC1_Y  MC2_P   MC2_Y    MC3_P   MC3_Y  constant
WFS1_PIT        -0.1262    0.3677   -0.4539   -0.6297   -0.1889   -0.1356   0.013664
WFS1_YAW     -0.0112   -0.7415   -0.1844    2.4509   -0.0023   -0.3531  -0.016199
WFS2_PIT         0.1251    0.4824   -0.2028   -0.6188    0.0099   -0.1490   0.006890
WFS2_YAW      0.0120   -0.7957   -0.1793    0.9962   -0.0493    0.2672 -0.013695

Also, I measured the same thing for 100s, and to my surprize, even the signs of coeficients are different.

coef_mat =

1.0e+05 *

MC1_P   MC1_Y  MC2_P   MC2_Y    MC3_P   MC3_Y   constant
WFS1_PIT       -0.1981    0.3065   -0.6084   -0.9349   -0.4002   -0.3538   0.009796
WFS1_YAW     0.0607   -0.6977    0.0592    2.8753    0.3507    0.0373   -0.008194
WFS2_PIT        0.0690    0.4769   -0.2859   -0.7821   -0.1115   -0.2953  0.004150
WFS2_YAW     0.0580   -0.8153   -0.0937    1.1424    0.0650    0.4203  -0.010629

The reason I can understand is that the measurements were not made at the same time, and hence conditions might have changed.

A thing to note in all these coefficients is that they relate the error signals to the 'perturbation' around a certain point (given below). That point is assumed to lie in the linear region.

MC1_PIT      2.6129
MC1_YAW   -5.1781
MC2_PIT       3.6383
MC2_YAW    -1.2872
MC3_PIT      -1.9393
MC3_YAW    -7.518

3183   Thu Jul 8 20:32:22 2010 nancyUpdateIOOMC alignment values.

I and Koji were trying to lock the mode cleaner for measuring the beam power at MC2 end. That is when we obtained the trans and refl values.

The beam characteristics at the MC2 were measured so that we could now use a dummy beam of similar power to test and characterize the QPD we are about to install at the MC2 end. This QPD wil provide two more signals in pitch and yaw, and hence complete 6 signals for 6 rotatioanl dof of the cavity. (4 are coming from WFS).

Once the QPD is characterised, it can be used to see the spot position at MC2. This is related to the mirror angles.

The width measurements were done using a beam scan. the beam scan was properly adjusted so that the maxima of the intensity of the sopt was at its center.

We also fitted gaussian curve to the beam profile, and it was a substantially good fit.

The whole idea is that I am trying  to look how the Wavefront sensors respond to the perturbations in the mirror angles. Once this is known, we should be able to control the mirror-movements.

the starting point would be to do just the DC measurements (which I did today). For proper analysis, AC measurements are obviously required.(will be done later).

The matrices so calculated can be inverted, and if found enough singular, the method can be used to control.

The first shot is to see teh dependency of teh error signals only on MC1 and MC3, and see if that is kind of enough to control these two mirrors.

If this works, the QPD signals could be used to control MC2 movements.

Quote:

Hmm. I expect that you will put more details of the work tomorrow.
i.e. motivation, method, result (the previous entry is only this),
and some discussiona with how to do next.

 Quote: Nancy and Koji: This is what I and Koji measured after aligning the MC in the afternoon. MC_Trans 4.595 (avg) MC_Refl 0.203 (avg) MC2_trans : power = 1.34mW 13.5% width : x=6747.8 +- 20.7 um  , y = 6699.4+- 20.7 um

3184   Thu Jul 8 21:44:43 2010 nancyUpdateIOOWFS calculations

I just found the singular values and the condition number of the 4*4 matrix relating the WFS error signals and the MC1 and MC2 movements.

### the condition number is ~12.5. I think its small enough to continue with the scheme. (if the measurements and all are reliable).

3197   Mon Jul 12 15:49:56 2010 nancyUpdateSUSCharacterisation of the QPD

I and koji setup the measurement of the QPD response to the pitch and yaw displacements of the beam spot.

We did this using a 100mW 1064nm laser. Its power was attenuated to ~ 1.9mW, and the spot size at the QPD position was 6000-7000 um .

The QPD was put on a translation stage, using which, the center of teh QPD wrt the beam spot could be moved in pitch and yaw.

Following are the measurements :

For yaw

:

The slope of teh linear region is -8356 /inch

For pitch

The slope of the linear region in this is 9085/inch

3198   Mon Jul 12 17:05:30 2010 nancyUpdateSUSCharacterisation of the QPD

 Quote: I and koji setup the measurement of the QPD response to the pitch and yaw displacements of the beam spot. We did this using a 100mW 1064nm laser. Its power was attenuated to ~ 1.9mW, and the spot size at the QPD position was 6000-7000 um . The QPD was put on a translation stage, using which, the center of teh QPD wrt the beam spot could be moved in pitch and yaw. Following are the measurements :

The slopes and other stats are

Pitch

Linear model Poly1:
f(x) = p1*x + p2
Coefficients (with 95% confidence bounds):
p1 =        8550  (7684, 9417)
p2 =       -2148  (-2390, -1906)

Goodness of fit:
SSE: 9944
R-square: 0.9923
RMSE: 44.59

Yaw

Linear model Poly1:
f(x) = p1*x + p2
Coefficients (with 95% confidence bounds):
p1 =       -8310  (-8958, -7662)
p2 =        2084  (1916, 2252)

Goodness of fit:
SSE: 6923
R-square: 0.9954
RMSE: 37.21

3208   Tue Jul 13 17:36:42 2010 nancyUpdateIOOWavefront Sensing Matrix Control

For yesterday - July 12th.

Yesterday, I tried understanding the MEDM and the Dataviewer screens for the WFS.

I then also decided to play around with the sensing matrix put into the WFS control system and see what happens.

I changed the sensing matrix to completely random values, and for some of the very bad values, it even lost lock :P (i wanted that to happen)

Then I put in some values near to what it already had, and saw things again.

I also put in the matrix values that I had obtained from my DC calculations, which after Rana's explanation, I understand was silly.

Later I put back the original values, but the MC lock didnot come back to what it was earlier. Probably my changing the values took it out of the linear region. THE MATRIX NOW HAS ITS OLD VALUES.

I was observing the POwer Spectrum of teh WFS signals after changing the matrix values, but it turned out to  be a flop, because  I had not removed the mean while measuring them.  I will do that again today, if we obtain the lock again (we suddenly lost MC lock badly some 20 minutes ago).

3218   Wed Jul 14 12:31:11 2010 nancyUpdateGeneralWeekly Update

Summary of this week's work Wednesday - Aligned the mode cleaner with Koji, and then measured the beam characteristics at MC2 end. Koji then taught me how to read the WFS signals Thursday - wrote a script to measure the signals and calculated the coefficients relating mirror movement and DC signals of WFS. To know the possibility of the control, found SVD of the coeff matrix, and condition number. Friday - Set up the measurement of QPD linear response using a laser outside the cavity. Took data. Monday - did the calculations and plotting for the above experiment. Then played around with the MEDM screens , and also tried to see what happens to the Power Spectrum of WFS signals by changing the coefficients in teh matrix. (failed) Tuesday - played around with WFS, tried seeing what it does when switched on at different points, and also what it does when I disturb the system while WFS has kept it locked.

Today - had switched off the WFS sensors yesterday night after locking the MC as wanted to know that how does MC behave when no WFS gain is applied. I checked in the morning, the MC was locked all night. I am now proceding with my calculations for the sensing matrix
3236   Fri Jul 16 15:39:27 2010 nancyUpdateIOOWavefront Sensors- switched off

I tuned the gain of WFS to 0 last night at about 3am.

I turned it back on now.

3253   Tue Jul 20 18:29:43 2010 nancyUpdateIOOQPD installed behind the MC2

Yesterday I installed teh QPD on the table behind MC2, and observed teh signal on it.

The MC_leak is directed to it by a steering mirror.

I used the A2L_MC2 script to minimise  teh pitch and yaw gains, and estimated teh spot position on teh MC2 using that.

This spot position was aligned to the center of teh QPD.

In the night while before taking measurements, I decided to turn off the Wavefront Sensor Servos, but just after that, the MC alignment went very bad, and I could not align it in the next 2 hours.

For some reason, the MC was really mad the whole day yesterday, and was getting misaligned again and again, even when the WFS feedback was on.

The table also had another IR laser in it, which I and Koji switched off.

I will continue measuring once we pump down again.

For now, I am analysing teh QPD circuit Transfer Function.

3352   Tue Aug 3 03:15:06 2010 nancyUpdateIOOMC back to locked mode

I turned the WFS gain to 0.02 back, and the MC is locked, the data for the seismic motion might be meaningful nowforth.

3357   Wed Aug 4 11:10:28 2010 nancyUpdateIOOMode Cleaner WFS

Yesterday, I started twiddling with the Mode Cleaner at about 2 pm.

So the seismic data should be all good before that.

I was using it till about 3.30 am, and then left for the night with locking it and swithcing on back the WFS control

Today morning, I have started twiddling with it again, at about 10.30 am.

About my work with the mode cleaner :

I am primarily exciting the mirrors in pitch and yaw, and trying to measure the response of the WFS and the MC2 OPLEV wrt the excitation.

This thus involves switching off the WFS control while measurement.

After two more of those measurements today, I will get to finding new values for the Output Matrix of the WFS for controlling MC1 & 3, and also, try giving in control to MC2 alignment using OPLEV signals.

3358   Wed Aug 4 12:49:42 2010 nancyUpdateIOOMode Cleaner WFS

 Quote: Yesterday, I started twiddling with the Mode Cleaner at about 2 pm. So the seismic data should be all good before that. I was using it till about 3.30 am, and then left for the night with locking it and swithcing on back the WFS control Today morning, I have started twiddling with it again, at about 10.30 am.   About my work with the mode cleaner :   I am primarily exciting the mirrors in pitch and yaw, and trying to measure the response of the WFS and the MC2 OPLEV wrt the excitation. This thus involves switching off the WFS control while measurement. After two more of those measurements today, I will get to finding new values for the Output Matrix of the WFS for controlling MC1 & 3, and also, try giving in control to MC2 alignment using OPLEV signals.

TFs after the measurement -

In the order - MC1 , MC2 , MC3 -pitch and yaw.

These plots let us know about how do the wavefront sensor signals actually respond to the mis-alignments in the mirrors.

For legibility, legend has been includded in only one plot in each pdf., its typically the same for all  3 plots.

the actual xml files for this measurement are in the directory /cvs/cds/caltech/users/nancy/Align_Matrix/highpower/spot_center

It was made sure before each measurement that the MC is best aligned, the WFS are turned off, and the spots on all 3 QPDs are centered.

3365   Thu Aug 5 01:29:39 2010 nancyUpdateIOOMode Cleaner WFS

I calculated the MC1&3 Vs WFS1&2 Output Matrix today from the above measurements with koji's help.

the matrix can be generated from the m file at /cvs/cds/caltech/users/nancy/Align_Matrix/matrix.m

these values were put in, and the direction of control is sort of confirmed. I tried twiddling with the gains in the loop to get a 4*4 stable control, but could not succeed.

the mode cleaner is back locked now, and WFS matrix as well as gains are reverted to the old values.  (1.30 am)

The output Matrices are

Pitch

 0.724 0.197 0 0 -1.448 -0.758

Yaw

 0.919 0.139 0 0 -0.0106 -0.1245

3366   Thu Aug 5 11:48:52 2010 nancyUpdateIOOMode Cleaner WFS

Quote:

I calculated the MC1&3 Vs WFS1&2 Output Matrix today from the above measurements with koji's help.

the matrix can be generated from the m file at /cvs/cds/caltech/users/nancy/Align_Matrix/matrix.m

these values were put in, and the direction of control is sort of confirmed. I tried twiddling with the gains in the loop to get a 4*4 stable control, but could not succeed.

the mode cleaner is back locked now, and WFS matrix as well as gains are reverted to the old values.  (1.30 am)

The output Matrices are

Pitch

 0.724 0.197 0 0 -1.448 -0.758

Yaw

 0.919 0.139 0 0 -0.0106 -0.1245

I realised today morning that there was a flaw in my calculations for the yaw matrix.

Correcting the values, and also making teh tables more readable.

I will test these values once our computers are back to working condition.

 PITCH WFS1 WFS2 MC1 0.724 0.1964 MC2 0 0 MC3 -1.4436 -0.756

 YAW WFS1 WFS2 MC1 0.0710 0.1074 MC2 0 0 MC3 0.0082 -0.962

3387   Mon Aug 9 13:32:02 2010 nancyUpdateIOOMode Cleaner ASC

E-log entry for Friday - will attach more plots to this entry on wednesday after i am back   to the 40.

Started working at some 1030 hrs and recording the Open Loop Tfs for all 6 loops.
The control was not so good, and I lost the lock quite a number of times while measureing
WFS  did not converge when the spot was aligned to the center. But there was convergence to a non-center point. So if  the control system was switched on near those points, it was converging to that point.

Autolocker : switches WFS control on directly, whereas the best way is to gradually increase the gain to 1. Also, the autolocker code now needs to be changed to incoporate the switing off the MC2 oplev in down and switch it on in the up script.

After Koji locked the Reference Cavity in the evening, I resumed measurements for the Open Loop TFs.

Measurement of the Open Loop Transfer Functions :

noise waveform was generated using arbitrary wf generator and injected into each loop.
An LPF was applied to have max co-relation at minimum disturabnce. (thanks to Rana)
The Transfer functions, Co-relations and Power Spectra were then measured using the DTT.

Power Spectrum of the IN1, IN2 and EXC shows clearly the suppression of the noise, and OLTF shows the phase margins.

- Courtesy Rana again for suggesting the idea of plotting power spectra of all signals in the same graph.

Later in the night , Koji worked with me and we reflected upon all TFs and changed gains whereevr required according to the phase margin considerations from the Open Loop TFs.
We used the same output matrix given in the previous e-log.

Final gains -

Alignment Gain in the WFS Master - 1.000

 Loop Gain WFS1 P 0.27 WFS1 Y 0.7 WFS2 P 0.15 WFS2 Y 0.110 MC 2OPLEV P -0.1 MC2 OPLEV Y -0.1

this measurement invloved locking the MC to the correct position, with the spot centered at both the WFS and the QPD. invloved some cheating (offsets) after we tried centering w/o offsets.
demod signal was also centered while alignment.
credits to Koji for getting the correct lock position and also staying with me till late night in the lab

Important Points to be noted

1. All loops' histories have to be cleared while swtiching them on.
2. turn the loop output before the loop input so that there is no remnant history in the loop.
2. Alignment gain was gradually increased to 1. and tehn the oplevs turned on.

Later measured teh PSD of  6 error signals under 3 conditions -

New Control ON

New Control OFF

Old Control ON

Also measured the time series for the MC_trans and MC_refl for the 3 conditions.

 Status MC_Trans MC_REF New Control ON New Control OFF Old Control ON

3389   Mon Aug 9 21:50:50 2010 nancyUpdateIOOMode Cleaner ASC

 Quote: The WFS and QPD servos were working. That was great. Everything was fine except for the time series plots. I could not get what story you are telling with the time series. (e.g. your's are good or bad or anything)

Well, the data is kind of not enough to be analysed in time domain,

But by far from what I analyse, I think that the new control is not worse than the old one.

I donot also find any better results, except for this one being theoritically stronger.

3417   Thu Aug 12 23:49:04 2010 nancyUpdateEnvironmentLaser chiller temp raised

Since the laser is off, Jenne and I rasied the chiller-chiller (small AC in the Control Room) set point temperature to 73 degree F (from 68F) to save people from shivering.

3419   Fri Aug 13 09:41:00 2010 nancyOmnistructureComputersCharger for dell laptop

I have taken the charger for the dark gray dell laptop from its station, and have labelled the information there too.

Will keep it back tonight.

3244   Mon Jul 19 14:14:03 2010 nancy, kojiUpdateIOOQPD Response Transfer Function

Friday night myself and Koji measured the Transfer function of the QPD circuit at MC2 side using a chopper . Following was our procedure :

We connected some wires at the input and output of the filter circuit to one of the segment of teh QPD. - seg 1.

A laser light was shined on to the QPD, it was pulsed using a chopper. The frequency of rotation of the chopper was varied.

These wires were then fed to the spectum analyser , and a transfer funstion was observed, It was nearly a low pass filter

The chopper frequency was then made variable by giving the chopper a signal from the spectrum analyser. This signal just swiped a large range of the rpm of the chopper.

Now the input signal looked like a sine wave of varying frequency. the transfer function looked like a perfect LPF, with a small SNR.

Attaching the plot of the TF in the next e-log (this one is on windows and can't access /cvs/cds)

3245   Mon Jul 19 14:16:01 2010 nancy, kojiUpdateIOOQPD Response Transfer Function

 Quote: Friday night myself and Koji measured the Transfer function of the QPD circuit at MC2 side using a chopper . Following was our procedure :   We connected some wires at the input and output of teh filter circuit to one of the segment of teh QPD. - seg 2. A laser light was shined on to  the QPD, it was pulsed using a chopper. The frequency of rotation of teh chopper was varied. These wires were then fed to the spectum analyser , and a transfer funstion was observed, It was nearly a low pass filter The chopper frequency was then made variable by giving the chopper a signal from teh spectrum analyser. This signal just swiped a large range of the rpm of the chopper. Now the input signal looked like a sine wave of varying frequency. the transfer functino looked like a perfect LPF, with a small SNR. Attaching the plot of the TF in the next e-log (this one is on windows and cant access /cvs/cds)

3372   Fri Aug 6 10:44:55 2010 nancy, kojiUpdateIOOMode Cleaner WFS

 Quote: Upon Nancy's request, I checked the status of the suspensions. I found that the power strip of the 1Y4 rack was turned off. Since it has a over current breaker, I don't know whether it happened by someone or over current. Anyway, I restarted the sus computers, and now the suspensions are damping as usual. The MC has been aligned, the auto locker is also working. Incidentally, I found that the WFS servos are not working. Actually since the last night It repeated losing lock and unlock. Probably some values of the matrix or the gain is wrong. I left the WFS as it is because Nancy will put new values this afternoon. I will ask her to confirm that the old values work at the end of her work.

Yesterday , I put in the Output Matrix, and changed the gain sliders for the 4 WFS loops.

It worked and was keeping the lock for the MC.

I then tested whether the MC1 and 3 were following any change in MC2 alignment. It was indeed workinng,

Next we stepped to putting in the gains for the MC2 oplev servo.

the signs are decided on the basis of convergence, and the magnitude is kept very low, to have a very slow control for MC2.

This complete 6 * 6 model does work, and was able to keep the transmission held.

I also tried poking each mirror in pitcg and yaw, and the cavity comes back to high resonance after some time.

This time is indeed large if the poking is made for MC2, and the transmission comes back to normal after big oscillations.

I tried to measure the Open loop TFs for all these loops yesterday, but somehow could not find a correct excitation.

I will do it today.

1.  Center the spot on MC2 and the QPD

2. Optimize the gains by looking at response to noise.

3. Measure Power Spectrum Density of each error signal.

10117   Tue Jul 1 18:06:13 2014 nichinUpdateComputer Scripts / ProgramsNetwork Analyzer NWAG4395A data acquisition

EDIT: The script and template file have been moved to /opt/rtcds/caltech/c1/scripts/general/netgpibdata/

___________________________________________________________________________________________________________

The NEW and IMPROVED script for remotely getting data from Agilent 4395A network analyzer is located at /users/nichin

This script is quite different from the one in Elog 10108 and fetches us both magnitude and phase. There is an added feature of setting the IF Bandwidth.

The network analyzer is located at crocetta.martian (192.168.113.108)

### How to run the script:

> python NWAG4395A_data_acq.py [filename.yml]

1. The script accepts sweep parameters and output options via a .yml file that is written following a template that can be found at /users/nichin/NWAG4395A_parameters.yml
2. The data obtained is stored as a .dat file and the corresponding details regarding the acquired data is in a .par parameter file
3. Separate .dat and .par files are created for phase and magnitude of voltage data.
4. You can choose to get a plot of the data obtained by specifying it in the .yml file. The plots are automatically stored as PDF.
5. Plots, data and parameter files are all stored in a new folder that is created with a timestamp in its name.
6. NOTE: Plotting options are only available in computers running numpy versions of 1.6.0 or above.(Currently only Ottavia and Chiara)

### Test Run:

I connected a simple 2MHz Low pass filter between the modulation output and signal input of the NA and ran a scan from 100KHz to 20MHz. The script was run from Ottavia.

The expected plot was obtained and is attached here.

### Current work:

Setting up the RF switch in rack 1Y1 to select between required PDs and scripts to tell it which channel to choose over the Ethernet.

8035   Fri Feb 8 12:42:45 2013 nicolasSummaryGeneralPRC/arm mode matching calculations

 Quote: The main issue is that flipping PR3 induces considerable astigmatism.

Yes, at 45degrees PR3 will only have a curvature of about 850m for the vertical mode of the beam, apparently not enough to stabilize the cavity.

8693   Tue Jun 11 10:00:54 2013 nicolasUpdateGreen LockingY arm locked with green but bad mode matching

 Quote: Still no good locking! After making the reflected beam size closer to the injected one, I maximized alignment. I locked again in 00 mode, but I couldn't maximize the power.  I just realized that maybe I'm not using the correct radius of curvature for the ETMY in the simulation. Tomorrow I will start checking from that.

Also make sure you are taking into account the substrate of the ETM.

8701   Thu Jun 13 16:01:48 2013 nicolasUpdateGreen LockingY arm locked with green but bad mode matching

 Quote: After restoring alignment I could see again strong 00 flashes (about 250-300 counts on ALS-TRY). So I locked the arm with IR and after enabling the PDH servo for the green locking, I also locked the green on the Y arm in 00 mode. Then I moved the two mode matching lenses to maximize the power into the 00 mode, but I didn't reach more than 30-35 counts. Green power injected into the Y arm                    0.680mW Green power reflected back                                  0.090mW Green power transmitted on the PSL                  few uW I would expect more power on the PSL table (maybe 10x more).

Is this reflection measured with the cavity locked or unlocked?

So what's the actual designed reflectivity of the ETM for green? No one seems to be able to give me a straight answer about this.

Looking at the reflected beam when the beam is misaligned makes it look like it's << 0.9. Is that expected given the coating spec?

You say the cavity scan goes as high as 300cts but you can only lock to 30cts, are you locked on the sideband?

8702   Thu Jun 13 16:13:08 2013 nicolasUpdateLSCNew modeled sensing matrix

I'd repeat the measurement for REFL11. The PRC arrow has some big error bar on it, and maybe the true error is even bigger.

Also, please make the placement of the plots the same for modeled and measured so it's easy to compare.

9385   Thu Nov 14 14:27:51 2013 nicolasOmnistructureGeneralSR785 Analyzer CRT replaced

The 785 analyzer in the 40 had a wonky hard to read screen. I was hoping that a new white CRT would fix all the problems.

I installed a white CRT, which didn't fix the wonkyness, but I adjusted the CRT position, brightness, focus settings to make the screen somewhat more readable.

BEFORE:

AFTER:

If we want to send the thing in for service to fix the wonkyness, we should probably hold on to the old CRT because they will probably replace the whole screen assembly and we'll lose our white screen.

9709   Mon Mar 10 21:13:43 2014 nicolasSummaryLSC Composite Error Signal for ARms (2)

In order to better understand how the composite signal would behave in the presence of noise, I decided to do a simple analysis of the cavity signals while sweeping through resonance.

My noise model was to just assume that a given signal has some rms uncertainty (error bars) and use linear error propagation to propagate from simple signals to more complicated ones.

I used the python package uncertainties to do the error propagation.

I assumed that the ALS signal, the cavity transmission, and the cavity PDH error signal all have some constant noise that is independent of the cavity detuning. Below is a sweep through resonance (x axis is cavity detuning in units of radians).

The shaded region represents the error on each signal.

Next I calculated the 'first order' calculated error signals. These being a raw PDH, normalized PDH, an inverse square root trans, and the normal ALS again. I tuned the gains so they match appropriately.

Here, one can see how the error in the trans signal propagates to the normalized and trans signals and becomes large are the fractional error in the trans signal becomes large.

Next I did some optimization of linear combinations of these signals. I told the code to maximize the total signal to noise ratio, while ensuring that the overall signal had positive gain. I did this again as a function of the cavity detuning.

Each curve represents the optimized weight of the corresponding signal as a function of detuning.

So this is roughly doing what we expect, it prefers ALS far from the resonance, and PDH close to the resonance, while smoothly moving into square root trans in the middle.

It's a little fake, but it gives us an idea of what the 'best' we can do is.

Finally I used these weights to recombine the signals into a composite, to get an idea of the noise of the overall signal. At the same time, I plot the weighting proposed by Koji's mathematica notebook (using trans and 1-trans, and a hard switch to ALS).

So as one can see, at least for the noise levels I chose, the koji weighting is not much worse than the 'optimal' weighting. While it is much simpler.

The code for all this is in the svn at 40mSVN/nicolas/workspace/2014-03-06_compositeerror

10014   Mon Jun 9 20:07:53 2014 nicolasHowToComputer Scripts / ProgramsLatex (math) in the elog

in the elog

One feature that has been sorely missing in the elog has been the ability to easily add mathematical symbols. Here is an imperfect solution.

There is a browser plugin available for firefox, safari and chrome that allow you to add “markdown” formatting to any rich text input box in the browser. One feature of markdown is latex math formulae.

http://markdown-here.com/

The way it works is you type some latex formatted math text in between dollar signs, click the button in your browser, and it converts them to rendered images.

So this

$E=mc^2.$

becomes this

Some drawbacks:

The images are actually rendered through a google service, so if that service changes or goes down, the images won’t render, however the HTML source still contains the source string.
The size of formulae are not really matched to the text.
Going back and forth between rendered and unrendered can lose changes (if you make changes after rendering).

Bonus features:

It also works in Gmail!
You can do code highlighting:

#!/bin/bash   ### this is a comment  PATH=\$PATH:/home/user/path    echo "How cool is this?" 

EDIT: it looks like the code highlighting is sort of broken :-(.

10543   Fri Sep 26 11:44:55 2014 nicolasFrogsComputer Scripts / ProgramsLoaded larry's fake filter into C1:ALS-OFFSETTER2

Larry and Nicolas

Larry's transfer function measurements suddenly started returning 0dB 0degrees when before there was some fake filter in the C1:ALS-OFFSETTER2 filter bank.

We looked in the filter bank and his filter was gone. So I created a new filter called LARRYP in FM2. We also disabled the output so he could drive the filter bank and test his TF code.

99   Wed Nov 14 07:48:38 2007 nornaOmnistructureOMCOMC Cable dressing
[Snipped from an email]

1) Last Friday Pinkesh and I set the OMC up with only the top three OSEMs and took a vertical transfer function. We had removed the other OSEMs due to difficulty of aligning all OSEMs with the weight of the bench etc bringing the top mass lower than the tablecloth can accommodate. See attached TF.Clearly there are extra peaks (we only expect two with a zero in between) and my belief is that at least some of them are coupling of other degrees of freedom caused by the electrical wiring. Pinkesh and I also noticed the difficulty of maintaining alignment if cables got touched and moved around. So.....

2) Yesterday Dennis and I took a look at how much moving a cable bundle around (with the peak shielding) changed the DC alignment. In a not too precise experiment ( using HeNe laser reflecting off the bench onto a surface ~ 1 metre away) we saw that we could reposition the beam one or two mm in yaw and pitch. This corresponds to ~ one or two mrad which is ~ the range of the OSEM DC alignment. We discussed possibility of removing the cabling from the middle mass, removing the peak and taking it from the bench directly to the structure above. I asked Chub if he could make an equivalent bundle of wires as those from the two preamps to see what happens if we repeat the "moving bundle" experiment. So...

3) Today Chub removed the cabling going to the preamps and we replaced it with a mock up of wire bundle going directly from the preamps to the structure above. See attached picture. The wires are only attached to the preamp boxes weighted down with masses but the bundle is clamped at the top. We repeated the "wiggle the bundle" test and couldnt see any apparent movement ( so maybe it is at most sub-mm). The cable bundle feels softer.

The next thing Chub did was to remove the second bundle ( from photodiodes, heater, pzt) from its attachment to the middle mass and strip off the peek. It is now also going to the top of the structure directly. The whole suspension now appears freer. We discussed with Dennis the "dressing " of the wires. There are some minor difficulties about how to take wires from the bright side to the dark side, but in general it looks like that the wires forming the second "bundle" could be brought to the "terminal block" mounted on the dark side and from there looped up to the top of the structure. We would have to try all this of course to see the wiring doesnt get in the way of other things (e.g. the L and R OSEMs). However this might be the way forward. So...

4) Tomorrow Pinkesh and I will check the alignment and then repeat the vertical transfer function measurement with the two bundles as they are going from bench to top of structure. We might even do a horizontal one if the middle mass is now within range of the tablecloth.
We can then remove preamp cables completely and lay the second bundle of cables on the optical bench and repeat the TFs.

The next thing will be to weigh the bench plus cables. This will allow us to
a) work out what counterbalance weights are needed - and then get them manufactured
b) firm up on how to handle the extra mass in terms of getting the masses at the correct height.

And in parallel Chub will work on the revised layout of cabling.

Looking a little further ahead we can also get some stiffness measurements made on the revised bundle design ( using Bob's method which Alejandro also used) and fold into Dennis's model to get some sanity check the isolation.

I think that's it for now. Comments etc are of course welcome.

Norna
10055   Wed Jun 18 11:57:44 2014 not JenneUpdateLSCIFO alignment recovery

 Quote: I noticed today, and Rana said that he saw Saturday, that the MC refl value when the MC is unlocked is unusually high.  It typically goes to about 4.5 V, but now is going up to 6.5V.  Since the PMC output is the same as usual (max seen has been about 0.82 today), something must have happened between the PMC and the IMC.  Late last week, EricG and Nichin were looking at things on the AS table.  Was anything touched on the AS table?  Was anything touched on the PSL table?  'Fess up please, so that we can pinpoint what the change was.

Nope, we did not touch any of the PDs other than AS55. I have mentioned in  my elog:10037 what we did exactly.

We just looked at all the other PDs to check if they were being illuminated by the correctly labeled fiber. Nothing other than that.

5917   Wed Nov 16 20:30:27 2011 not KojiUpdateIOOMC unlocked and misaligned.

 Quote: Actually, do we need to reset the filter history at every lock loss of the MC? Those DC offsets were necessary to keep the alignment good just until the MC is unlocked. So if we keep the history, we can maintain the good alignment.

I suspect the integrators get fed a huge wrong signal on lockloss. Clearing the history on the trans DOFs when the MC was badly aligned gets it nicely aligned again. I switched off the alignment transmission DOFs for now.

10182   Fri Jul 11 09:41:43 2014 not KojiUpdateGeneralCoupling telescope design

 Quote: CFC-2X-C has a FIXED focal length of 2mm, but the collimator lens position is adjustable. I'm not yet sure this affects your calculation or not as what you need is an approximate mode calculation; once you couple the any amount of the beam into the fiber, you can actually measure it at the output of the fiber with a collimator attached.

I don't believe it had any effect, as all the calculations gave me the same target waist.

12258   Wed Jul 6 21:09:09 2016 not KojiUpdateComputer Scripts / ProgramsNew Tabs and Working Summary Pages

I don't know much about how the cron job runs, I'll forward this to Max.

 Quote: I started to receive emails from cron every 15min. Is the email related to this? And is it normal? I never received these cron emails before when the sum-page was running.

Max says it should be fixed now. Have the emails stopped?

14181   Thu Aug 23 16:10:13 2018 not KojiUpdateIMCMC/PMC trouble

Great, thanks!

 Quote: I don't know what had been wrong, but I could lock the PMC as usual. The IMC got relocked by AutoLocker. I checked the LSC and confirmed at least Y arm could be locked just by turning on the LSC servos.

14537   Thu Apr 11 12:21:01 2019 not KojiUpdatePSLPSL fan is noisy

I could probably install the new fan if we have one.  Can you do without the laser for a while?

 Quote: This thread: ELOG 10295 My interpretation of these ELOGs is that we did not have the replacement, and then I brought unknown fan from WB. At the same time, Steve ordered replacement fans which we found in the blue tower yesterday. The next action is to replace the internal fan, I believe.
15586   Sat Sep 19 19:37:16 2020 not KojiUpdateVACTP3 RP failure

Disconcerting because those tip seals were just replaced [15417]. Maybe they were just defective, but if there is a more serious problem with the pump, there is a spare Varian roughing pump (the old TP2 dry pump) sitting at the X-end.

I reset the interlock error to unfreeze the vac controls (leaving V5 closed).

 Quote: So the conclusion is that RP for TP3 has failed. Presumably, the tip-seal needs to be replaced. Right now TP3 was turned off and is ready for the tip-seal replacement. V5 was closed since the watchdog tripped.
16561   Mon Jan 10 14:00:44 2022 not KojiUpdateBHDSOS assembly -- SR2

Yes,

For the thin optics adapter design, we want Peek 1/4-20 screw (part # 98885A131) to replace the lower back long EQ stop. On it, we will have a Peek washer (part # 93785A600) fastened between two Peek nuts (part #98886A813).

For the thick optics adapter design, we want Peek 1/4-20 screw (part # 98885A131) to replace both the upper and lower back EQ stop. On the upper stop, we need a single Peek nut (part #98886A813).

I will cure-test the Vacseal.

Quote:

Vacseal in the freezer. It could have been expired sooooo many years ago, We need some cure testing.

Can you release the part numbers of the ordered components (and how/where to use them), so that we can incorporate them into the CAD model?

 Quote: Again, we should apply some glue to the counterweight to prevent it from spinning on the setscrew. Is there a glue other than EP30 that we can use? Related: Peek nuts, screws and washers were ordered from Mcmaster.

ELOG V3.1.3-