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ID Date Author Type Category Subject
  1091   Sun Oct 26 21:02:18 2008 ranaUpdateComputer Scripts / ProgramsSVN medm problem
As we've seen in the past a few times, there's something wrong with the files in the trunk/medm area.
I get the following error message when doing a fresh checkout:
A    c1/lsc/help/C1LSC_LA_SET.txt
svn: In directory 'c1/lsc/help'
svn: Can't copy 'c1/lsc/help/.svn/tmp/text-base/C1LSC_RFadjust.txt.svn-base' to 'c1/lsc/help/.svn/tmp/C1LSC_RFadjust.txt.tmp.tmp': No such file or directory
It looks like that there are some .svn files which have been checked in as if they're some kind of source code instead of just maintenance files.
We probably have to go through and clean this out and then remove these excess files somehow.
  1090   Fri Oct 24 22:30:38 2008 Jenne,ranaUpdatePEMNoise from Guralp Seismometer
Attached is a Power Spectrum of the noise on the Vert1 channel of the Guralp seismometer. The noise is in the several hundreds of nV/rtHz up near 50Hz and higher, but is in the several microV/rtHz range at lower frequencies. Our high frequency noise is almost definitely below the noise of the ADC, but the lower frequencies, where we actually care, it's not as clear.

To Do list:
  • Measure the noise of the ADC - is the Guralp Box lower for all frequencies?
  • Use conversion factors to convert this measured noise into the minimum ground motion that we can measure. Is this at least a factor of 100 lower than our regular ground motion?

** UPDATE: This is actually the noise of the Guralp breakout box, not the Guralp itself. It is the noise measured on the output of the box
with the input shorted. The board is configured to have a gain of 20 (10 from the AD620 and 2x for differential drive). We also measured
directly at the AD620 output and all of this noise comes directly from that chip. If Jenne calculates that this noise is too high we would
have to find a replacement with a better low frequency floor (e.g. LT1012 or LT1007 depending on the Guralps source impedance).
Attachment 1: Vert1_Noise_24Oct2008.png
Vert1_Noise_24Oct2008.png
  1089   Fri Oct 24 21:49:15 2008 JenneConfigurationPEMShort Seismometer Cable
Bad news regarding the cable that goes between the Guralp seismometer and the box that I've been working on: it's too short by about a factor of 2. Dang it. I've placed the seismometer underneath the Beam Splitter Chamber (where it needs to go), and started running the cable toward the ADC rack where box was planned to go, and as Rana guessed earlier tonight, the cable isn't nearly long enough. We have some options: the seismometer can go back into the half-height rack near the BS, SRM, PRM oplev's optical table where I think it used to be, or it can go into the rack with the Kepco high voltage power supplies and the laser's supply. The cable won't reach any farther than that.

I think that we can just add BNC extensions onto the octopus cable that Bob made for the Guralp box, so all we need to figure out after we decide on a rack is the power for the box.
  1088   Fri Oct 24 20:54:41 2008 ranaConfigurationComputerslinux2
I have removed linux2 and its cables from the control room and put it into 1Y3 along with op340m.

When Joe next comes in we can ask him to Cat6 it to the rest of the world, although it already
seems to me that the CDS hub/switch next Alberto's desk is too full and that we need to purchase
a 48 port device for there.
  1087   Fri Oct 24 18:05:01 2008 AlbertoUpdateGeneralAbs length: transverse mode spacing measured for the X arm
The ETMX suffers of astigmatism. I measured the following frequencies for the higher order modes:
- f_01 = 6317500 +/- 500 Hz
- f_10 = 6305500 +/- 500 Hz

From

g2=1/g1*(cos(A*L*pi/c))^2

where A= (fsr-f_i), fsr=(3897654+/-15)Hz (see elog entry 956), L=(38.4580+/-0.0003)m, g1=0.9947 (from R1=7280m), I get the following values for the g-factor coefficients:

g2_x = 0.3164 +/- 0.0002
g2_y = 0.3209 +/- 0.0002

from which we have the radius of curvature of ETMX:

R_x = 56.26 +/- 0.01 m
R_y = 56.63 +/- 0.01 m


The specs for the mirror have R2= 57.57 m (unc).

So, they seem conditions similar of those of ETMY that Koji measured:

Rx = 56.1620 +/- 0.0013 [m]
Ry = 57.3395 +/- 0.0011 [m]

for which L_yarm: 38.6462 m +/- 0.0003 m
Attachment 1: 24OCT08_TEM10-01_comparison(file12-14).png
24OCT08_TEM10-01_comparison(file12-14).png
  1086   Fri Oct 24 17:21:13 2008 AlbertoUpdateGeneralAbs length: the right amount of beam clipping
I found the reason why the peak at about 6.3MHz appeared only on the TEM10 mode: the blade was clipping the beam too much and it was probably totally killing the mode. I'm attaching a plot that shows that difference when I did that.
Attachment 1: 24OCT08_levels_of_clipping_comparison.png
24OCT08_levels_of_clipping_comparison.png
  1085   Fri Oct 24 15:05:13 2008 steveUpdateVACrga is out of order
The old Dycor RGA is out of order.
I'm getting ready to purchase an SRS instrument.
  1084   Fri Oct 24 11:42:48 2008 AlbertoUpdateGeneralAbs length: locking the X arm cavity in TEM01/10
I went back to lock the arm cavity in either TEM01 or TEM10 mode. Attached are the results. We still have several resonances which we can't clearly identify. I expect TEM01/10 to be at 6.276MHz but we don't have a peak exactly there. What we have is:
- a peak at 6.320MHz in the measurement of the TEM01 mode (the one with the lobes of the spot almost on the vertical axis)
- a peak at 6.590MHz in both the TEM01 and TEM10 measurements.

I'm either missing the real TEM01/10 mode or the peaks at 6.590MHz are those. If that were true, that would mean that the radius of curvature of ETMX is 49.29 m instead of 57.57 m as listed in the IFO data sheets. I think it's much more likely that the measurements are missing the right peaks.
Attachment 1: TRX_armTEM00-plot_09-10_together.png
TRX_armTEM00-plot_09-10_together.png
  1083   Fri Oct 24 11:21:26 2008 peteConfigurationPSLFSS LO input calibrated in dBm
Based on the measurements described in my previous elog, I created a new calc record in the file /cvs/cds/caltech/target/c1psl/psl.db
grecord(calc, "C1:PSL-FSS_LOCALC")
{
        field(INPA,"C1:PSL-FSS_LODET")
        field(SCAN,".1 second")
        field(PREC,"4")
        field(CALC,"6.29*LOGE(A)+5.36")
}

After restarting scipe3 to load this change, I told C1PSL_FSS.adl to look at this record instead of *LODET. That MEDM screen now shows LO input calibrated in dBm.

For reference, the operators available for use in the CALC field are listed in the EPICS Record ref manual, Chapter 9. The manual can be found here:
http://www.aps.anl.gov/epics/EpicsDocumentation/AppDevManuals/RecordRef/Recordref-3.html

Yoichi said he was fixing an SVN problem, so I have not yet committed the two files I changed: /cvs/cds/caltech/target/c1psl/psl.db and /cvs/cds/caltech/medm/c1/psl/C1PSL_FSS.adl.
  1082   Fri Oct 24 11:09:08 2008 steveUpdateSAFETYmore lexan plates under cameras
The MC2, MC3&1 and BSC-SUS cameras were repositioned somewhat in the
process of placing lexan disks under neat them.
MC1&3 will have to be readjusted.

Now all horizontal viewports are protected.
  1081   Fri Oct 24 10:06:16 2008 YoichiConfigurationIOOMC gain and FSS gain changed
Following the measurements of MC and FSS loop gains, I modified mcup script to set the MC VCO gain to 2dB (it was -4dB before).
I also changed the normal value of the FSS common gain to 7dB. The open loop transfer functions posted in the previous two entries
were measured with those settings.
  1080   Thu Oct 23 23:09:18 2008 YoichiUpdatePSLMC UGF is now 75kHz
I measured three loop transfer functions of the MC servo.
The blue curve in the first attachment is the overall open loop gain of the servo measured using
the sum-amp A of the MC board (it is the sum-amp in the common part).
The red curve is the transfer function measured by the sum-amp B of the MC board, which is in the VCO path.
Mathematically the measured transfer function is G_vco/(1+G_L), where G_L is the loop gain of the length path
and G_vco is the loop gain of the VCO path.
The green curve is G_L/(1+G_vco) which was measured from dtt by using C1:SUS-MC2_MCL_EXC.
The UGF of the MC loop is 75kHz with the phase margin of 27deg.
The cross over frequency of the two loops is 43Hz. The phase margin there seems OK.

The second attachment is the comparison of the MC open loop TF measured on Sep. 4 (old) and today (new).
The increased bandwidth of the FSS gave us a slight gain in the phase margin and the elimination of
the slight bump in the gain around 150kHz existed in the blue curve.
Attachment 1: MC_Loop.png
MC_Loop.png
Attachment 2: OldAndNew.png
OldAndNew.png
  1079   Thu Oct 23 21:52:27 2008 YoichiUpdatePSLFSS UGF now 450kHz
I measured the open loop transfer function of the FSS, for the first time after I mitigated the oscillation.
The attached plot shows the comparison of the OPLTF before and after the oscillation was mitigated.
Blue curves are when AD797 was oscillating, and the red ones are after AD797s were replaced by AD829s.
The FSS gain slider values are the same for the both measurements.
There is a notable difference in the shape of the TF.
Right now the UGF is around 450kHz with the phase margin of 50deg.
When the gain is increased by a few dBs in the common gain slider, the PC path becomes saturated.
This might be caused by the peak in the OPLTF at 1.7MHz sticking out of the 0dB line.
Another peak at 770kHz is also annoying.
Too bad that I did not take the TF above 1MHz before the oscillation was mitigated.
Also at 100kHz, the new TF has a lower gain than the old one, although it looks like the slope of the red curve is getting steeper and
it is catching up the blue one at lower frequencies.
I will measure the TF below 100kHz later.

With this bandwidth, I was able to increase the MC gain further.
I will report on the MC open loop measurements soon.
Attachment 1: FSS_OPLTF.png
FSS_OPLTF.png
  1078   Thu Oct 23 20:47:28 2008 peteConfigurationPSLFSS LO calibration for MEDM
Today I took a quick series of measurements to calibrate the FSS LO power measurement in the MEDM. This was done by using the spec.an. to measure the 21.5 MHz peak in dBm at the LO input to the FSS box on the PSL table, and recording the MEDM value, for attenuations applied at the FSS REF box output ranging from -5 dBm to -30 dBm.

I measured the loss due to the BNC cable I used, which was (19.66-19.50) dBm. I accounted for this and plotted ln(MEDM) vs. dBm on the attached plot. A linear fit of this gives the CALC field of a calc record for the IOC db:
6.29*LOGE(A)+5.36

Since no one knew how to do this nonlinear conversion in EPICS I will describe how to do it in detail tomorrow. It is simple, although it requires power cycling the scipe3 bunch (typing "reboot" or "ctl-x" at the command prompt took it down, but it did not come back). I did power cycle those computers a few times today.
Attachment 1: fss_lo_calibration.png
fss_lo_calibration.png
  1076   Thu Oct 23 18:51:19 2008 AlbertoMetaphysicsComputerseLog
I checked it and the latest version of the elog software, the 2.7.5 (we have the 2.6.5) has, among new nice features, the very good ability to fit the entries into the screen width without showing kilometric lines like we see now. Should we upgrade it?
  1075   Thu Oct 23 18:45:18 2008 AlbertoOmnistructureComputer Scripts / ProgramsPython code for GPIB devices developed for the Absl length experiment
I wrote two Python scripts for my measurement that can be also used/imitated by others: sweepfrequency. py and HP8590.py. The first is is the one that we run by a Python interpreter (just typing "python <name script> <parameters>"from the terminal). It manages the parameters that we have to pass it for the measurement and calls the second one, HP8590.py which actually does most of the job.

Here what it does. It scans the frequency of the Marconi and, for each step, searches the highest peak in the Spectrum Analyzer (which is centered 50 KHz around the frequency of the Marconi). It then associates the amplitude of the peak to the frequency of the Marconi and write the two number in two columns of a file.
The file name, the GPIB-to/LAN interface IP address, the frequency range, the frequency step amplitude and the number of measures we want it to average for each step, are all set by the parameters when we call sweepfrequency.py.
More details are in the help of the function or just looking at the header of the code.

I guess that one can perform other similar measurement just with little changes in the code so I think it could turn out useful to anyone else.
Attachment 1: HP8590.py
# This function provides the measuremeent of the peak amplitude on the spectrum analyzer
# HP8590 analyzer while sweeping the excitation frequency on the function generator.
#
# Alberto Stochino 2008

import re
import sys
import math
from optparse import OptionParser
from socket import *
... 55 more lines ...
Attachment 2: sweepfrequency.py
## sweepfrequency.py [-f filename] [-i ip_address] [-a startFreq] [-z endFreq] [-s stepFreq] [-m numAvg]
#
## This script sweeps the frequency of a Marconi local oscillator, within the range
## delimited by startFreq and endFreq, with a step set by stepFreq. An arbitary
## signal is monitored on a HP8590 spectrum analyzer and the scripts records the
## amplitude of the spectrum at the frequency injected by the Marconi at the moment.

## The GPIB address of the Marconi is assumed to be 17, that of the HP Spectrum Analyzer to be 18

## Alberto Stochino, October 2008
... 51 more lines ...
  1074   Thu Oct 23 18:27:04 2008 AlbertoUpdateGeneralAbs length

Quote:
Here are the measurements I've got yesterday. The plot shows the transmitted power after the X arm while sweeping the frequency of the beat between the two lasers. That frequency is changed by scanning the frequency of the local oscillator of the PLL (that is the Marconi).
The X arm cavity has been locked to the TEM00 of the main beam. I tilted ITMX in order to enhance the higher modes of the secondary beam with the purpose of making them beat with the main beam.
Three traces are shown in the plot correspondent to three different measurements in which I clipped the transmitted beam at the X end with a razor blade from up and from the side of the photodiode.
Both the beats of the TEM00 mode of the main laser with the TEM01 and TEM10 modes of the secondary laser are expected to be at 6.2763 MHz. The plot has a candidate peak at 6.325MHz but it does not appear on both the measurements with the blade. the peaks at 3.897MHz and 7.795MHz are the first and the second longitudinal modes of the X arm cavity.


Here is the Matlab code I use to calculate the HOM frequencies.
Attachment 1: HOM_Frequencies.m
% FP Cavity HOM Frequencies Estimate
% Alberto Stochino, October 2008

R1 = 7280;      % Mirror1 radius of curvature
R2 = 57.57;     % Mirror2 radius of curvature
L = 38.458;     % Length of the FP Cavity
n = 1;          % X Order of the Mode
m = 0;          % Y Order of the Mode

c = 299792458;  % Speed of Light
... 11 more lines ...
  1073   Thu Oct 23 18:23:47 2008 AlbertoUpdateGeneralAbs length

Quote:
Here are the measurements I've got yesterday. The plot shows the transmitted power after the X arm while sweeping the frequency of the beat between the two lasers. That frequency is changed by scanning the frequency of the local oscillator of the PLL (that is the Marconi).
The X arm cavity has been locked to the TEM00 of the main beam. I tilted ITMX in order to enhance the higher modes of the secondary beam with the purpose of making them beat with the main beam.
Three traces are shown in the plot correspondent to three different measurements in which I clipped the transmitted beam at the X end with a razor blade from up and from the side of the photodiode.
Both the beats of the TEM00 mode of the main laser with the TEM01 and TEM10 modes of the secondary laser are expected to be at 6.2763 MHz. The plot has a candidate peak at 6.325MHz but it does not appear on both the measurements with the blade. the peaks at 3.897MHz and 7.795MHz are the first and the second longitudinal modes of the X arm cavity.


Today I repeated the measurement and I'm attaching the resulting plot. Still, not clear and (and most of all) not nice.
It seems like tilting ITMX is introducing a lot of unwanted higher modes that don't let us to clearly identify TEM01 and TEM10.
I think I'm going to stop it to get back to technique in which the arm cavity is locked to the TEM01/10 of the main beam.
Attachment 1: TRX_plot_06_07_08_together.png
TRX_plot_06_07_08_together.png
  1072   Thu Oct 23 15:27:19 2008 AlbertoUpdateGeneralAbs length
Here are the measurements I've got yesterday. The plot shows the transmitted power after the X arm while sweeping the frequency of the beat between the two lasers. That frequency is changed by scanning the frequency of the local oscillator of the PLL (that is the Marconi).
The X arm cavity has been locked to the TEM00 of the main beam. I tilted ITMX in order to enhance the higher modes of the secondary beam with the purpose of making them beat with the main beam.
Three traces are shown in the plot correspondent to three different measurements in which I clipped the transmitted beam at the X end with a razor blade from up and from the side of the photodiode.
Both the beats of the TEM00 mode of the main laser with the TEM01 and TEM10 modes of the secondary laser are expected to be at 6.2763 MHz. The plot has a candidate peak at 6.325MHz but it does not appear on both the measurements with the blade. the peaks at 3.897MHz and 7.795MHz are the first and the second longitudinal modes of the X arm cavity.
Attachment 1: TRX_aplot_03_04_05_together.png
TRX_aplot_03_04_05_together.png
  1071   Thu Oct 23 11:26:25 2008 steveBureaucracyVACoptosigma forks for vacuum
Nine short forks from OptoSigma were cleaned, baked and measured by Bob T.
They passed the LIGO vac compatiblity test as Rana predicted.
Remember: Thorlab and Newfocus forks failed this qualification process.
  1070   Wed Oct 22 20:50:30 2008 AlbertoOmnistructureComputersGPS
Today I measured the GPS clock frequency at the output of CLOCK_MON in a board on the same crate where the c1iool0 computer is located. The monitor was connected with a BNC cable to the 10MHz reference input of the frequency counter on top of that rack, where it was used to check the 166MHz coming from one of the Marconi.

The frequency was supposed to be 10MHz but I actually measured 8 MHz. I tracked down the GPS input cable to the board and it turned out to come from one of the 1Y7 rack. Here it was connected to a board with a display that was showing corrupted digits, plus some leds on the front panel were red.

I'm not sure the GPS reference is working properly.
  1069   Wed Oct 22 17:48:58 2008 YoichiUpdateGeneralLenses for focusing the optical lever laser (Re:divergence of He Ne 1035P)
Steve had difficulty in finding lenses for focusing the HeNe laser for the ITM op-lev.
Following his measurement of the beam divergence, I did some calculation to find a suitable set of lenses and positions.

First, I fitted Steve's data to get the waist size and location of the new HeNe.
The first plot shows the fitting result.
The size of the waist is 0.3mm at -367mm from the laser output (i.e. inside the laser).
(I only used horizontal beam size data.)

Then using the obtained beam parameter, I calculated the propagation of the beam through two lenses.
After playing with the focal length and location of the lenses, I found that with parameters {f1=-0.125m, f2=0.2m, d1=0.2m, d2=0.1m} we get about 1mm beam at the QPD (about 4m away from the laser). f1 and f2 are the focal lengths of the lenses, d1 is the distance from the laser to the first lens and d2 is the distance between the two lenses.
The second plot shows the beam size as a function of the distance from the laser.

The Mathematica notebook used to plot the beam propagation is attached.
By running it on Mathematica 6, you can dynamically change the parameters (focal lengths and locations) by sliders, and the plot (like the one shown in the second attachment) updates in real time. It is cool. Please try it.



Quote:
The ITM oplevs laser diodes are noisy.
They will be replaced by JDS 1035P
SN T8093307 was measured with the beamscanner.
This will able us to calculate the right lenses to get a small beam on the qpd.

**
The first column is distance from the front face of the laser in cm.
The second column is beam diameter in the horizontal direction in microns.
The third column is the beam diameter in the vertical direction in microns.
(edit by Rana)
Attachment 1: BeamProfile.png
BeamProfile.png
Attachment 2: BeamPropagation.png
BeamPropagation.png
Attachment 3: BeamPropagation.zip
  1068   Wed Oct 22 16:22:53 2008 steveBureaucracySAFETYCaryn received safety training
Caryn Polatchi has received 40m safety training on Monday, Oct 20
  1067   Wed Oct 22 12:37:47 2008 josephbUpdateComputersNetwork spreadsheet
Attached in open office format as well as excel format is spreadsheet containing all the devices with IP addresses at the 40m. Please contact me with any corrections.
Attachment 1: 40m_network_10-15-08.ods
Attachment 2: 40m_network_10-15-08.xls
  1066   Wed Oct 22 09:42:41 2008 AlbertoDAQComputersc1iool0 rebooted and MC autolocker restarted
This morning I found the MC unlocked. The MC-Down script didn't work because of network problems in communicating with scipe7, a.k.a. c1iool0. Telneting to the computer was also impossible so I power cycled it from its key switch. The first time it failed so I repeated it a second time and then it worked.
Yoichi then restarted c1iovme. It was also necessary to restart the MC autolocker script according to the following procedure:
- ssh into op440m
- from op440m, ssh into op340m
- restart /cvs/cds/caltech/scripts/scripts/MC/autolockMCmain40
  1065   Tue Oct 21 18:19:42 2008 YoichiConfigurationComputersLISO and Eagle installed
I installed LISO, a circuit simulation software, into the control room linux machines.
I also installed a PCB CAD called Eagle to serve as a graphical editor for LISO.
I put a brief explanation in the wiki.
http://lhocds.ligo-wa.caltech.edu:8000/40m/LISO

As a demonstration, I made a model of the FSS PC path and did a stability analysis of the op-amps.

The first attachment is the schematic of the model.
You can find the model in /cvs/cds/caltech/apps/linux/eagle/projects/liso-examples/FSS

The second attachment shows the stability analysis plot of the first two op-amps when AD829s are used.
The op-amp model is for the uncompensated AD829. The graph includes the bode plots of the open-loop transfer function of each op-amp.
If the phase delay is more than 360deg (in the plot it is 0 deg because the phase is wrapped within +/-180 deg) at the unity gain frequency,
the op-amp is unstable.
It is clear from the plot that this circuit is unstable. This is consistent with what I experienced when I replaced the chips to AD829 without
compensation.
Unfortunately, I don't have an op-amp model for phase compensated AD829. So I can't make a plot with compensation caps.

The third attachment is the stability analysis of the same circuit with AD797. It also shows that the circuit is unstable at 200MHz, though I
observed oscillation at 50MHz.

Finally, I did an estimate of frequency noise contribution from the noise of AD829.
First I estimated the voltage noise at the output of the board caused by the first AD829 using LISO's noise command.
Then I converted it into the input equivalent noise at the stage right after the mixer by calculating the transfer function
of the circuit using LISO.
Within the control bandwidth of the FSS, this input equivalent noise appears at the mixer output with the opposite sign.
Since we know the calibration factor from the mixer output voltage to the frequency noise, we can convert this into the frequency noise.
The final attachment is the estimated contribution of the AD829 to the frequency noise. As expected, it is negligible.
Attachment 1: FSS_PC_Path.pdf
FSS_PC_Path.pdf
Attachment 2: AD829Stability.png
AD829Stability.png
Attachment 3: AD797Stability.png
AD797Stability.png
Attachment 4: FreqNoiseByAD829.png
FreqNoiseByAD829.png
  1064   Tue Oct 21 17:52:30 2008 ranaSummaryPSLFSS Photo: early October
This is a photo of the FSS board before Yoichi did his surgery - it was taken with the D40 in macro mode, sitting on the big Gorilla pod.
Attachment 1: fss.jpg
fss.jpg
  1063   Tue Oct 21 16:17:45 2008 YoichiUpdatePSLAD797 Oscillation in the FSS board
I checked each op-amp's output in the FSS board to see if any indication of slew-rate saturation can be found.
PA85, which was the most suspicious one, actually has a very large slew rate limit (1000V/usec).
Its output swing was about 5V/usec. So PA85 was ok in terms of slew rate.
However, I found that an AD797 used at the first stage of the PC path was oscillating by itself, i.e. even without the loop closed.
The frequency was about 50MHz and the amplitude was large enough to reach the slew rate limit of this chip (the steepest slope was 30V/usec whereas the slew
rate limit of AD797 is 20V/usec).

I replaced it and another AD797 right after the oscillating one with AD829s. Just replacing the chips caused oscillation of AD829.
It was because there were no phase compensation capacitors connected to the pin 5 of AD829s.
Since the PCB was designed for AD797, there is no pattern for compensation caps. So I ended up putting Mica capacitors (47pF) across the pin 5 and the nearest ground point.
It worked and the oscillation stopped.

As I reported in an earlier elog, stopping the oscillation did not solve the problem of low FSS bandwidth.
  1062   Tue Oct 21 16:14:42 2008 steveUpdateGeneraldivergence of He Ne 1035P
The ITM oplevs laser diodes are noisy.
They will be replaced by JDS 1035P
SN T8093307 was measured with the beamscanner.
This will able us to calculate the right lenses to get a small beam on the qpd.

**
The first column is distance from the front face of the laser in cm.
The second column is beam diameter in the horizontal direction in microns.
The third column is the beam diameter in the vertical direction in microns.
(edit by Rana)
Attachment 1: 1035p_divergence.png
1035p_divergence.png
  1061   Mon Oct 20 20:50:09 2008 YoichiConfigurationPSLFSS board chip replacement
A quick update.

I changed two AD797s on the FSS board to AD829s to mitigate the 50MHz oscillation, which I plan to report later.
For some reason, the PA85 was broken after the replacement. So I had to replace it with a spare one too.
Right now the FSS is back and working. The oscillation is gone.
However, the maximum achievable gain is still about the same as before.
  1060   Mon Oct 20 16:18:00 2008 AlanConfigurationComputers/cvs/cds restored

Quote:
I moved missing files in /cvs/cds restored by Alan and Stuart to the original locations.
I confirmed autoburt runs, and dtt, which had also been having trouble running, runs ok now.

I found an interesting piece of evidence on allegra, our new 64bit linux machine.
In the Trash of controls Desktop on that machine, there is /cvs/cds/vw/ directory.
I remember that when I last time emptied the trash bin on the machine (yesterday), it took somewhat long time.
Too bad that I did not pay attention to what was actually in the Trash, but now I have a feeling that in the Trash were
missing /cvs/cds/* directories.
While emptying the Trash, I encountered several errors saying permission denied or something like that, and skipped those files.
Sometimes, when you move something from NFS mounted directories to the Trash, you get this kind of errors.
So my guess is that someone accidentally (or intentionally) moved /cvs/cds/* except for "caltech" to the Trash of allegra.
And I completely removed them carelessly.


In the meantime, I have re-started the nightly backup for /frames/minute-trends
but NOT YET for /cvs/cds ,
since I fear that we'll find another problem and will need to go back to the June 27 backup.
Let's wait a few days for the dust to settle,
and if everyone feels confident that /cvs/cds is ok,
I'll restart the backup of that.

How I restored the files, for the record:

Stuart mounted /archive/backup onto an accessible computer (garrak.ligo.caltech.edu ) and I logged on to controls@nodus and ran this command:

/cvs/cds/caltech/scripts/backup/rsync --rsync-path=/usr/bin/rsync --rsh=/usr/bin/ssh --compress --verbose --archive --hard-links --exclude=caltech/ ajw@garrak.ligo.caltech.edu:/backup/40m/cvs /cvs/cds/recover_20081020

I had to type in my GC password, and it ran for ~20 minutes (would have been much longer had I asked for /cvs/cds/caltech as well!).

you can view the backups by logging on to garrak.ligo.caltech.edu with your GC account:
/backup/40m/cvs/cds/
/archive/frames/trend/minute-trend/40m
  1059   Mon Oct 20 15:02:00 2008 YoichiConfigurationComputers/cvs/cds restored
I moved missing files in /cvs/cds restored by Alan and Stuart to the original locations.
I confirmed autoburt runs, and dtt, which had also been having trouble running, runs ok now.

I found an interesting piece of evidence on allegra, our new 64bit linux machine.
In the Trash of controls Desktop on that machine, there is /cvs/cds/vw/ directory.
I remember that when I last time emptied the trash bin on the machine (yesterday), it took somewhat long time.
Too bad that I did not pay attention to what was actually in the Trash, but now I have a feeling that in the Trash were
missing /cvs/cds/* directories.
While emptying the Trash, I encountered several errors saying permission denied or something like that, and skipped those files.
Sometimes, when you move something from NFS mounted directories to the Trash, you get this kind of errors.
So my guess is that someone accidentally (or intentionally) moved /cvs/cds/* except for "caltech" to the Trash of allegra.
And I completely removed them carelessly.
  1058   Mon Oct 20 12:18:38 2008 AlanUpdateComputer Scripts / Programsburtwb missing on Solaris but installed on linux64

Quote:
c1lsc stalled this evening, so I powercycled it.
After that, I tried to lock arms to confirm the computer is working.
Then I realized that the restore alignment buttons do not work from any control room computer.
I found that it was because burtwb command was missing. For Solaris, looks like there used to be /cvs/cds/epics/extensions/burtwb but now
there is no /cvs/cds/epics directory. I thought there were directories other than "caltech" in /cvs/cds/, weren't there ?
Right now, there is only /cvs/cds/caltech.
Anyway, I installed burt for 64bit linux computer (under /cvs/cds/caltech/apps/linux64/epics/extensions/).
At this moment the alignment save/restore works on allegra (and probably on rosalba), but not on op440m yet.



The automatic backup of /cvs/cds (and /frames/minute-trends ) to the LIGO archive in Powell-Booth,
which runs from fb40m using the scripts in /cvs/cds/caltech/scripts/backup ,
stopped when fb40m was rebooted on June 28, 2008,
and the check_backup script I run to send an email when this happens also failed due to a scripting error.

But we still have a backup of /cvs/cds from June 27.

The backup of /cvs/cds (excluding /cvs/cds/caltech and /cvs/cds/tmp)
circa June 27, 2008
has been restored to
/cvs/cds/recover_20081020 .

Please check to see that it has what we need.

Before moving it over to where it belongs,
it would be really nice to figure out what happened...

Meanwhile, I have fixed the check_backup script and restarted the backup, which will run this evening...
but maybe I should wait till the dust settles?

Now is also a good time to think about whether there is anything else besides for
/cvs/cds and /frames/minute-trends that should be backed up regularly.


- Alan
  1057   Mon Oct 20 09:45:56 2008 steveUpdatePEMPSL HEPA on
The PSL HEPA filter was turned on.
It should be running all times.
The 0.5 micron particle count is up to 20,000 this morning.
  1056   Fri Oct 17 21:41:09 2008 YoichiUpdateComputer Scripts / Programsburtwb missing on Solaris but installed on linux64
c1lsc stalled this evening, so I powercycled it.
After that, I tried to lock arms to confirm the computer is working.
Then I realized that the restore alignment buttons do not work from any control room computer.
I found that it was because burtwb command was missing. For Solaris, looks like there used to be /cvs/cds/epics/extensions/burtwb but now
there is no /cvs/cds/epics directory. I thought there were directories other than "caltech" in /cvs/cds/, weren't there ?
Right now, there is only /cvs/cds/caltech.
Anyway, I installed burt for 64bit linux computer (under /cvs/cds/caltech/apps/linux64/epics/extensions/).
At this moment the alignment save/restore works on allegra (and probably on rosalba), but not on op440m yet.
  1055   Fri Oct 17 16:43:10 2008 YoichiConfigurationComputersmcup/down scripts on linux
I made some changes to /cvs/cds/caltech/medm/c1/ioo/cmd/medmMCup and medmMCdown so that those can be run from medm on linux machines.
  1054   Thu Oct 16 16:26:26 2008 peteConfigurationPSLFSS phase matching cable installed
RG 405 cable has a solid teflon dielectric, and a velocity factor of 0.69. To get the 8.2 degrees of additional phase on the LO output at 21.5 MHz then requires 22 cm of cable. I made a cable that ended up being 21 cm long after I'd gained some experience putting on the connector. It gives a phase difference between LO and RF of about 10 degrees. It is currently installed.
  1053   Thu Oct 16 13:12:58 2008 peteConfigurationPSLphase between FSS reference outputs
I verified the phase between the FSS reference outputs (used for LO and RF) using matched BNC cables. I measured 0.95 degree (average of 12 scope measurements).
  1052   Thu Oct 16 09:47:49 2008 YoichiConfigurationPSLFSS ref phase measurements

Quote:
I fit the bottom (quadratic) portion of this curve, and found an optimum delay of 25.8 ns, which can be implemented as 25.81 ns on the phase shift box (25 + 1/2 + 1/4 + 1/16).


The gain of the loop is sinusoidally dependent on the phase delay. So the fit will be better with a function like this: 1/(1+G*sin(dphi + const)).
  1051   Thu Oct 16 09:44:49 2008 YoichiUpdatePSLBad cable for FSS
Yesterday arount 1:30PM, we lost the LO signal for the FSS.
I found it was caused by a bad cable connecting from the peter's RF oscillator box to the LO of the FSS.
I temporarily replaced it with a BNC cable of comparable length.
  1050   Wed Oct 15 22:07:52 2008 peteConfigurationPSLFSS ref phase measurements
Optimizing the FSS LO/RF phase at 500 kHz, above the servo band, proved to be noisy and those measurements were useless. Today I repeated
the measurement at 35 kHz and got good signal to noise. I've attached a plot of the 35 kHz peak in dBm as measured at IN2 by SR785, with
an injection into TEST2 at 35 kHz with 0.2 Vpp, as a function of delay in ns given by the delay phase shifter normally used by the 166 MHz.
I fit the bottom (quadratic) portion of this curve, and found an optimum delay of 25.8 ns, which can be implemented as 25.81 ns on the phase
shift box (25 + 1/2 + 1/4 + 1/16). This is an uncalibrated number and meaningless.. For all these measurements a very long SMA cable
(did not measure) was inserted on the RF output of the 21.5 MHz reference box. The actual phase difference depends on these cable lengths
which I didn't measure.

To determine the actual phase difference I compared the LO and RF input points with the 25.81 ns delay, using a scope with poor man's
averaging (33 manual triggers and recording the phase measurements). The phase difference was 8.24 degrees with an error on the mean of 3.4%,
with the LO having the longer effective cable (cable plus delay from the phase delay box). As a sanity check I set the phase delay box
to 20 ns and re-measured, and found 49.5 degrees. (1/21.5 MHz) * (49.5-8.24)/360 = 5.3 ns, which is about the difference between 20 ns
and 25.81 ns. I did the same with 0 ns dialed in, and found a difference of 21.5 ns (I expected 25.8 ns). So it is possible that the
phase delay box isn't too precise.

Finally, to determine the length of cable needed to implement 8.24 degrees of phase at 21.5 MHz with RG58 cable, I made some phase measurements
using the FSS reference box and mismatched cables. I used three cable lengths (93 cm, 140.5 cm, and 169.5 cm ) and two mismatched pairs with
dL of 29 and 76.5 cm. For each pair I took average of 20 measurements, finding 22.54 degrees mean for the dL=29 cm pair (0.78 degrees/cm, or
a speed of light of 1.0e10 cm/s, or 10.6 cm of cable length on the LO) and 43.57 degrees mean for dL=76.5 cm pair (0.57 degrees/cm, or a speed
of light of 1.4e10 cm/s, or 14.5 cm of cable length on the LO). I expected more precise agreement.

Maybe the 21.5 MHz reference box is not zero phase between the outputs. This could be easily tested. It might be interesting to repeat this
measurement with a few more dL values.
Attachment 1: phasedelay.png
phasedelay.png
  1049   Wed Oct 15 17:40:50 2008 ranaUpdatePSLPMC Offset adjusted
I set the PMC servo input offset: closed the MOPA shutter, zeroed the mixer output with the offset slider,
relocked everything, and set the nominal to the new value of -6 V.
  1048   Tue Oct 14 19:24:34 2008 YoichiConfigurationPSLFSS light power reduced
Rana, Yoichi

To change the gain distribution in the FSS, Rana reduced the VCO power for the AOM to reduce the light incident to the reference cavity.
Now the transmitted power of the RC is 2.3V compared to 6.5V before.
The FSS common gain can be increased to 5dB. I haven't changed the normal gain for this slider, so the mcup script will still set
the common gain to 1.5dB after an MC lock.
With this change, we take some gain from the optical part and give more gain in the electronics.
This might relieve the slew rate limit problem if it is happening in an early stage of the electronics.
  1047   Tue Oct 14 19:18:18 2008 YoichiUpdateComputersBootFest
Rana, Yoichi

Most of the FE computers failed around the lunch time.
We power cycled those machines and now all of them are up and running.
I confirmed that the both arms lock.
Now the IFO is in "Restore last auto-alignment" status.
  1046   Tue Oct 14 14:19:36 2008 peteConfigurationPSLFSS ref phase
Today I made several measurements which should yield the optimized phase for the FSS 21.5 MHz reference. I made two sets of measurements, using the 166 MHz phase delay shifter. For each phase value I made 5 measurements of a 500 kHz injection into test2 at 1 Vpp, with the 4195 spectrum analyzer on in1 with the high impedance probe, 51 points, a 10 kHz range. It was surprisingly noisy. I will make plots using matlab to find the maximum, and hope for consistent results between the two sets of measurements. If it is too noisy or inconsistent I will repeat the measurement at ~800 kHz.

Once I find the phase which yields peak amplitude in in1, I will measure the relative phase between LO and RF going in to the FSS, measure the speed of light in RG58 cable, and construct a new cable which will implement the desired relative phase.
  1045   Mon Oct 13 18:59:39 2008 YoichiUpdatePSLNPRO EMI and FSS error signal correlation
I made a simple loop antenna to measure the electro-magnetic inteference (EMI) around the master oscillator NPRO.

The first plot shows the comparison of the FSS error signal with the EMI measured when the antenna was put next to the NPRO (the MOPA box was opened).
There are harmonics of 78.1kHz which are present in both spectra. It is probably coming from the DC-DC converter in the NPRO board.

The second plot is the same spectra when the antenna was put far from the NPRO (just outside of the PSL enclosure).
The 78.1kHz harmonics are gone. So these are very likely to be coming from the NPRO.

The third plot shows the coherence functions between the signal from the antenna and the FSS error signal.
When the antenna was put near the NPRO, there is a strong coherence seen around 78.2kHz, whereas there is no strong coherence
when the antenna is far away from the NPRO.
This is a strong evidence that the 78.2(or 78.1)kHz harmonics is coming from the NPRO itself.

There are many peaks other than 78.1kHz harmonics in the FSS error signal spectrum. For most of them you can also find corresponding peaks in the EMI spectrum.
We have to hunt down those peaks to avoid the slew-rate saturation of the FSS.
Attachment 1: IMG_1692.JPG
IMG_1692.JPG
Attachment 2: Spectrum.png
Spectrum.png
Attachment 3: SpectrumFar.png
SpectrumFar.png
Attachment 4: Coherence.png
Coherence.png
  1044   Mon Oct 13 13:56:03 2008 YoichiUpdatePSLMOPA is not that much in trouble now
The problem was found to be all to do with the shutter.
The shutter started to work again, after a while, apparently for no clear reason.
The alignment to the PA was actually not screwed, and the MOPA output is now slowly increasing.
We figured that the 126MON PD has been mis-aligned for a long time. It was just picking the
scattered light from the output of the PA. So when the shutter is closed, it is natural that 126MON also goes down to zero.
It is a bit difficult to center the beam on the PD because there is not much room for moving the PD.
However, Alberto came up with a configuration (flip the PD and reflect back the beam with a mirror to the PD), which seems to
be feasible. We will do this modification when the MOPA is confirmed to be ok.

Here is more detail about the shutter problem:
The shutter is controlled by the MOPA power supply. There are three ways to command the power supply.
The switch on the front panel of the power supply, the EPICS switch (through a XYCOM XY220), and the interlock.
The ribbon cable from the power supply's back is connected to J1 of the cross connect. The pin 59 of the cable is the one
controlling the shutter. It is then routed to J12 pin 36. The interlock and a XYCOM switch are both connected to this
pin.
Now what happened was, on the way tracking down those cables, I pushed some connectors, especially the ones on the XYCOM.
After that, I was able to open the shutter from the EPICS button.
Steve and Alberto tried the EPICS button many times in the morning without success.
My guess is that it was some malfunctioning of the XY220 accidentally fixed by my pushing of the cables.
But I cannot exclude the possibility of the interlock malfunctioning.



Quote:
Steve, Alberto, Yoichi

A quick update.
The MOPA output went down to zero on Sunday early morning (00:28 AM).
We found that the NPRO beam is mis-aligned on the power monitoring PD (126MON).
We don't know yet if it is also mis-aligned to the power amplifier (PA) because the mechanical shutter is not working (always closed).
Most likely the beam is not aligned to the PA.
A mystery is that although the beam is terribly (more than a half inch) missing the monitor PD, the beam still goes through two faradays.
Another mystery is that the NPRO output power is now increased to 600mW.

The power drop was a very fast phenomenon (less than 1/16 sec).
We are trying to figure out what happened.
The first step is to fix the mechanical shutter. We have a spare in our hand.
  1043   Mon Oct 13 13:51:49 2008 peteConfigurationPSLattempt to measure FSS ref phase
On Friday I began a measurement of the FSS reference phase. The setup involves the following:
+ turn off the 166 MHz LO (top signal generator on 1Y2 rack)
+ bring FSS LO 21.5 MHz to the 166 MHz delay line phase shifter, and back out the phase shifter with a second length of cable
+ add a length of cable to the RF 21.5 MHz in preparation for measuring FSS IN2 as a function of delay

Trouble locking the FSS, and ran out of time before the measurement could be performed.
  1042   Mon Oct 13 11:32:50 2008 YoixhiUpdatePSLMOPA is in trouble now
Steve, Alberto, Yoichi

A quick update.
The MOPA output went down to zero on Sunday early morning (00:28 AM).
We found that the NPRO beam is mis-aligned on the power monitoring PD (126MON).
We don't know yet if it is also mis-aligned to the power amplifier (PA) because the mechanical shutter is not working (always closed).
Most likely the beam is not aligned to the PA.
A mystery is that although the beam is terribly (more than a half inch) missing the monitor PD, the beam still goes through two faradays.
Another mystery is that the NPRO output power is now increased to 600mW.

The power drop was a very fast phenomenon (less than 1/16 sec).
We are trying to figure out what happened.
The first step is to fix the mechanical shutter. We have a spare in our hand.
Attachment 1: powerdrop.png
powerdrop.png
  1041   Fri Oct 10 20:03:35 2008 YoichiConfigurationComputersmedm, dataviewer, dtt on 64 bit linux
I compiled EPICS (base, medm and ezca) and dataviewer for 64 bit linux.
These are installed in /cvs/cds/caltech/apps/linux64/.
I also configured cshrc.40m to make it possible to run the 32bit dtt on 64bit machines.
64bit ligotools is also installed to /cvs/cds/caltech/apps/linux64/ligotools although I haven't tested it extensively.

With those essential tools available for 64bit linux, Joe and I decided to install 64bit CentOS to the new linux machine.
It is named allegra.
Now, medm, dataviewer, dtt, awg, foton and ezca commands all work on rosalba and allegra.
I put some notes on how to make things work on 64bit in the wiki.
http://lhocds.ligo-wa.caltech.edu:8000/40m/Building_LIGO_softwares_for_64_bit_linux

I compiled dtt (actually the whole GDS tree) for 64bit linux and the build process finished normally.
But somehow dtt does not work properly. It starts on my laptop but does not retrieve data. It crashes on rosalba.
So I had to retreat to 32bit.
ELOG V3.1.3-