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ID Date Author Typeup Category Subject
  4494   Wed Apr 6 19:36:32 2011 AidanSummaryGreen Locking(In)sanity check of Green PD - some inconsistencies

I moved the Hartmut Green PD to the Jenne laser bench to try to determine if the response at RF was reasonable or somehow very much smaller than it should be. It was set up as shown in the attached diagram. The first pass at this was by comparing the ratio of the RF photocurrent of the green PD to the RF photocurrent of the New Focus 1611 InGaAs PD. That ratio (at a sufficiently low frequency) should be the same as the ratio the DC photocurrents of the two PDs.

Using the network analyzer I measured the ratio of the voltages of the two RF signals (and then scaled each of these by the respective transimpedances of the PDs: 700 Ohms for the 1611 and 240 Ohms for the Harmut PD). The resulting ratio is shown in the attached plot.

I measured the DC voltages from each PD and scaled those by the transimpedances to get the photocurrent (10 kOhm for the 1611 and 80 Ohm effective for the Harmut PD). The ratio of the DC photocurrents was 0.37. This is roughly 3x the ratio of the RF photocurrents at 500kHz (=0.14). This discrepancy is uncomfortably large.

 The full set of measurements is given in the table below:

Measurement Value
DC voltage from Hartmut PD 6.5mV (checked by turning laser on and off and measuring the difference)
DC voltage from 1611 InGaAs PD 2.20V
Transimpedance of Harmut PD at DC 80 Ohm (effective)
Transimpedance of Harmut PD at RF 240 Ohm
Transimpedance of 1611 InGaAs at DC 10 KOhm
Transimpedance of 1611 InGaAs at RF 700 Ohm
Incident Power on Hartmut PD (100% on PD area) 0.28mW (measured by Ophir power meter)
Incident Power on 1611 InGaAs (<100% on PD area) 0.64mW
Responsivity of Silicon PD at 1064nm 0.02 A/W (estimate)
Responsivity of 1611 New Focus PD at 1064nm ~0.8 A/W

There is one other troubling point: using the estimate of responsivity on the Harmut PD * incident power * transimpedance at DC = (0.02A/W) * (0.28mW) * (80 V/A) = 0.45 mV.

But the measured DC voltage is 6.5mV = inconsistent.

Attachment 1: PD_measurement.png
Attachment 2: plot_PD_RF_ratios.pdf
  4497   Thu Apr 7 11:51:13 2011 steveSummarySAFETYnew crane operator inaugurated


Mike Caton of Konecranes inspected and loadtested all 3  of the 40m cranes at max reach trolley positions with 1 ton.

 Konecrane representative gave crane operator training in the 40m. Koji has become a qualified, trained crane operator of the 40m lab.

Attachment 1: P1070535.JPG
  4500   Thu Apr 7 16:09:17 2011 AidanSummaryGreen Locking(In)sanity check of Green PD - some inconsistencies

I think I had underestimated the responsivity of the Silicon PD at 1064nm. The previous value was based on a rough search online for the responsivity of Silicon (I couldn't find the product number of the actual PD we are using). For instance, the PDA100A Si detector from Thorlabs has a responsivity of 0.35-0.4A/W at 1064nm. 

If we calculate the responsivity of the Hartmut PD from the measurements I made today (input power = 0.300mW, output voltage = 5.56mV, effective transimpedance = 80 Ohms), then the responsivity at 1064nm is 0.23 A/W which is not an unreasonable number given the response of the Thorlabs detector.


Measurement Value
Responsivity of Silicon PD at 1064nm 0.02 A/W (estimate)
Responsivity of 1611 New Focus PD at 1064nm ~0.8 A/W

There is one other troubling point: using the estimate of responsivity on the Harmut PD * incident power * transimpedance at DC = (0.02A/W) * (0.28mW) * (80 V/A) = 0.45 mV.

But the measured DC voltage is 6.5mV = inconsistent.


  4501   Thu Apr 7 19:28:02 2011 KojiSummaryGreen Locking(In)sanity check of Green PD - some inconsistencies

Responsivity of SGD-444A


For instance, the PDA100A Si detector from Thorlabs has a responsivity of 0.35-0.4A/W at 1064nm.


Attachment 1: SGD-444A.png
  4502   Thu Apr 7 21:58:57 2011 AidanSummaryGreen LockingBeat note amplitude

Having convinced myself that the green Hartmut PD is giving an acceptable response at RF frequencies I decided to double-check the beatnote at IR (fiber transmission from the X-end beating with the PSL). This took a while because I had to realign the beam into the fiber at the X-end (I had a PD monitoring the output from the fiber on the PSL table and 40m of BNC cable giving me the signal from it at the X-end).

Eventually, I managed to get a beatnote on the PD. At first there was no signal at the temperature calculated using Koji and Suresh's calibration, but it turned out that the mode-overlap wasn't good enough on the PD. Now I can clearly see beats between a couple of modes, one of which is much stronger than the other. I think we should use a frequency discriminator on the output from the IR PD to servo the end laser and keep the strong beat note within <100MHz of DC.


  4504   Fri Apr 8 19:43:03 2011 kiwamuSummaryIOORF combiner eases impedance mismatching

An RF combiner should be included in the triple resonant box because it eases impedance mismatching and hence lowers undesired RF reflections.

Therefore we should use three cables to send the RF signals to the box and then combine them in the box.


(RF combiner)

 With proper terminations an RF combiner shows 50 Ohm input impedance.

But it still shows nearly 50 Ohm input impedance even if the source port is not properly terminated (i.e. non 50 Ohm termination).

This means any bad impedance mismatching on the source port can be somewhat brought close to 50 Ohm by a combiner.

  The amount of deviation from 50 Ohm in the input impedance depends on the circuit configuration of  the combiner as well as the termination impedance.

For example a resistive 3-way splitter shows 40 Ohm when the source port is shorten and the other ports are terminated with 50 Ohm.

Also it shows 62.5 Ohm when the source port is open and the other ports are terminated with 50 Ohm.

In this way an RF combiner eases  impedance mismatching on the source port.


(RF signal transfer at the 40m)

 According to the prototype test of the resonant box it will most likely have a non-50 Ohm input impedance at each modulation freqeucy.

If we install the resonant box apart from the combiner it will create RF reflections due to the mismatch (Case 1 in the diagram below)

The reflection creates standing waves which may excite higher harmonics and in the worst case it damages the RF sources.

 To reduce such a reflection one thing we can do is to install the combiner as a part of the resonant box (Case 2).

It will reduce the amount of the mismatching in the input impedance of the resonant circuit and results less reflections.

A rule we should remember is that a cable always needs to be impedance matched.



  4505   Fri Apr 8 20:43:46 2011 kiwamuSummaryIOORF combiner + resonant box : impedance and reflection coefficient

 The input impedance of the resonant box was measured when an RF combiner was attached to the box.

Indeed the combiner makes the impedance more 50 Ohm and reduces the reflection.


**** measurement conditions ****

* The output of box, where the EOM will be connected,  was open so that the box tries resonating with a parasitic capacitor instead of the real EOM.

* ZFSC-3-13, a 3-way combiner from mini circuit, was used.

* The S-port of the combiner was directly attached to the box with a short connector (~ 30 mm).

* Port 1 and 2 are terminated by 50 Ohm.

* The input impedance was measured on port 3 with AG4395A net work analyzer.

* Reflection coefficient 'Gamma' were calculated from the measured impedance 'Z' by using an equation Gamma = (50-Z)/(50+Z).


The resonances are found at 11, 29 and 73 MHz (55 MHz resonance was shifted to 73 MHz because of no EOM).

Note that the resonances are at frequencies where the notches appear in the reflection coefficient plot.

Don't be confused by a peak at 70 MHz in the impedance. This is an extra resonance due to a leakage inductance from the transformer in the circuit.

Quote: from #4504

An RF combiner should be included in the triple resonant box because it eases impedance mismatching and hence lowers undesired RF reflections.

  4517   Tue Apr 12 18:15:07 2011 kiwamuSummaryIOORF combiner is more like attenuator

I realized that my impedance matching theory on an RF combiner was wrong !

In fact an RF combiner behaves more like an attenuator according to a reflection measurement that I did today.

A 3-way combiner reduces power of an input signal by a factor of 4.8 dB because it can be also considered as a 3-way splitter.

So it is just a lossy component or in other words it is just an attenuator.


(reflection measurement)

To check my speculation that I posted on #4504 I measured reflection coefficients for both cases.

In the measurement I used a heliax cable, which goes from 1X2 rack to the PSL table with a length of about 10 m. Note that this is the cable that had been used as '33 MHz EOM'.

At the input of the heliax cable it was connected to a direction coupler to pick off reflections and the reflected signal was sampled in AG4395A.

The other end of the cable (output side of the cable) was basically connected to the resonant box.

Then I did a reflection measurement for both cases as drawn in this entry (see #4504).

  - case 1 -  the combiner was inserted at the input side of the heliax cable.

  - case 2 - the combiner was directly attached to the resonant box

On the combiner, ZFSC-3-13, the port 1 and 2 were terminated with 50 Ohm, therefore the port 3 was used as an input and the source port is the output.

Here is a resultant plot of the reflection measurements.


Note that whole data are calibrated so that it gives 0 dB when the output side of the heliax is open.

There are two things we can notice from this plot:

 (1) The reflection coefficient at the resonant frequencies (where notches appear) are the same for both cases.

 (2) Over the measured frequency range the reflections were attenuated by a factor of about 9.6 dB , which is twice as large as the insertion loss of the combiner.

These facts basically indicates that  the RF combiner behaves as a 4.8 dB attenuator.

Hence the location of the combiner doesn't change the situation in terms of RF reflections.

Quote from #4505

 The input impedance of the resonant box was measured when an RF combiner was attached to the box.

Indeed the combiner makes the impedance more 50 Ohm and reduces the reflection.



  4538   Mon Apr 18 13:05:57 2011 kiwamuSummaryLSCdemod board modification

Here is the idea how we upgrade the demodulation boards.

Basically we go ahead with two steps as depicted in the cartoon diagram below.

Once we finish the first step of upgrade, the board will be ready to install although the circuit won't be awesome in terms of noise performance.




* * * (details) * * *

 First of all we will replace the home-made 90 degree splitter (see this entry) by a commercial splitter, PSCQ-2-51-W+ from Mini circuit. This is the step 1 basically.

At this point the boards will be ready to use in principle. I asked Steve to get three 90 degree splitters so that we can have at least three demodulators for the dual-recycled Michelson locking.

If they work very fine we will buy some more 90 degree splitters for full locking.

While we try to lock the dual-recycled Michelson once we will get a Cougar amplifier, remove all ERA-5s and install it such that we don't have to gain up and down in the circuit. This is the last step.

  4549   Wed Apr 20 23:20:49 2011 jamieSummaryComputersinstallation of CDS tools on pianosa

This is an overview of how I got (almost) all the CDS tools running on pianosa, the new Ubuntu 10.04 control room work station.

This is machine is experiment in minimizing the amount of custom configuration and source code compiling. I am attempting to install as many tools as possible from existing packages in

available packages

I was able to install a number of packages directly from the ubuntu archives, including fftw, grace, and ROOT:

apt-get install \
libfftw3-dev \
grace \


I installed all needed LSCSOFT packages (framecpp, libframe, metaio) from the well-maintained UWM LSCSOFT repository.

$ cat /etc/apt/sources.list.d/lscsoft.list
deb http://www.lsc-group.phys.uwm.edu/daswg/download/software/debian/ squeeze
deb-src http://www.lsc-group.phys.uwm.edu/daswg/download/software/debian/ squeeze contrib
sudo apt-get install lscsoft-archive-keyring
sudo apt-get update
sudo apt-get install ldas-tools-framecpp-dev libframe-dev libmetaio-dev lscsoft-user-en

You then need to source /opt/lscsoft/lscsoft-user-env.sh to use these packages.


There actually appear to be a couple of projects that are trying to provide debs of EPICS. I was able to actually get epics working from one of them, but it didn't include some of the other needed packages (such as MEDM and BURT) so I fell back to using Keith's pre-build binary tarball.


apt-get install \
libmotif-dev \
libxt-dev \
libxmu-dev \
libxprintutil-dev \
libxpm-dev \
libz-dev \
libxaw7-dev \
libpng-dev \
libgd2-xpm-dev \
libbz2-dev \
libssl-dev \
liblapack-dev \

Pulled Keith's prebuild binary:

cd /ligo/apps
wget https://llocds.ligo-la.caltech.edu/daq/software/binary/apps/ubuntu/epics-3.14.10-ubuntu.tar.gz
tar zxf epics-3.14.10-ubuntu.tar.gz


I built GDS from svn, after I fixed some broken stuff [0]:

cd ~controls/src/gds
svn co https://redoubt.ligo-wa.caltech.edu/svn/gds/trunk
cd trunk
#fixed broken stuff [0]
source /opt/lscsoft/lscsoft-user-env.sh
export GDSBUILD=online
export ROOTSYS=/usr
./configure --prefix=/ligo/apps/gds --enable-only-dtt --with-epics=/ligo/apps/epics-3.14.10
make install


I installed dataviewer from source:

cd ~controls/src/advLigoRTS
svn co https://redoubt.ligo-wa.caltech.edu/svn/advLigoRTS/trunk
cd trunk/src/dv
#fix stupid makefile /opt/rtapps --> /ligo/apps
make install

I found that the actual dataviewer wrapper script was also broken, so I made a new one:

$ cat /ligo/apps/dv/dataviewer
export DVPATH=/ligo/apps/dv
mkdir $DCDIR
trap "rm -rf $DCDIR" EXIT
$DVPATH/dc3 -s ${NDSSERVER} -a $ID -b $DVPATH "$@"


Finally, I made a environment definer file:

$ cat /ligo/apps/cds-user-env.sh
# source the lscsoft environment
. /opt/lscsoft/lscsoft-user-env.sh

# source the gds environment
. /ligo/apps/gds/etc/gds-user-env.sh

# special local epics setup
export LD_LIBRARY_PATH=${EPICS}/base/lib/linux-x86_64:$LD_LIBRARY_PATH
export LD_LIBRARY_PATH=${EPICS}/extensions/lib/linux-x86_64:$LD_LIBRARY_PATH
export LD_LIBRARY_PATH=${EPICS}/modules/seq/lib/linux-x86_64:$LD_LIBRARY_PATH
export PATH=${EPICS}/base/bin/linux-x86_64:$PATH
export PATH=${EPICS}/extensions/bin/linux-x86_64:$PATH
export PATH=${EPICS}/modules/seq/bin/linux-x86_64:$PATH

# dataviewer path
export PATH=/ligo/apps/dv:${PATH}

# specify the NDS server
export NDSSERVER=fb

[0] GDS was not compiling, because of what looked like bugs. I'm not sure why I'm the first person to catch these things. Stricter compiler?

To fix the following compile error:

TLGExport.cc:1337: error: ‘atoi’ was not declared in this scope

I made the following patch:

Index: /home/controls/src/gds/trunk/GUI/dttview/TLGExport.cc
--- /home/controls/src/gds/trunk/GUI/dttview/TLGExport.cc (revision 6423)
+++ /home/controls/src/gds/trunk/GUI/dttview/TLGExport.cc (working copy)
@@ -31,6 +31,7 @@
#include <iomanip>

#include <string.h>

#include <strings.h>

+#include <stdlib.h>

namespace ligogui {
using namespace std;

To fix the following compile error:

TLGPrint.cc:264: error: call of overloaded ‘abs(Int_t&)’ is ambiguous

I made the following patch:

Index: /home/controls/src/gds/trunk/GUI/dttview/TLGPrint.cc
--- /home/controls/src/gds/trunk/GUI/dttview/TLGPrint.cc (revision 6423)
+++ /home/controls/src/gds/trunk/GUI/dttview/TLGPrint.cc (working copy)
@@ -22,6 +22,7 @@
#include <fstream>

#include <map>
#include <cmath>

+#include <cstdlib>

namespace ligogui {
using namespace std;

  4575   Wed Apr 27 20:14:16 2011 AidanSummaryelogRestarted with script ...
  4585   Fri Apr 29 03:39:49 2011 KojiSummaryLSCCavity lengths

I tried the idea that the PRC can resonate f1 and f2 at the same time if the arm gives the reflection phase to f1 and f2 with the ratio of 1 vs 5.

The details are described on wiki. The point is this removes all of the PRC/SRC/asymmetry mumbo jumbo.

The calculated cavity lengths for f_mod of 11.065399MHz are:

  • Arm Length: 37.7974 [m]

  • PRC Length: 6.7538 [m]

  • SRC Length: 5.39915 [m]

  • Asymmetry (lx-ly): 0.0342 [m]

Here is the actual values derived from the photos.

  • Arm Length: 37.54 [m] (0.26m too short)

  • PRC Length: 6.760 [m] (6mm too long)

  • SRC Length: 5.415 [m] (16mm too long)

  • Asymmetry (lx-ly): 0.0266 [m] (8mm too long)

  4619   Tue May 3 18:25:38 2011 kiwamuSummaryLSCPRMI locking : plan


 Since we've got the PRMI locked we now should be able to do more qualitative measurements.

Here is a task list that we will measure/develop in the PRMI condition.



 - Optical gain measurements

 - Characterization of control loops

 - MICH and PRC calibrations

 - Noise budget

 - Development of automatic noise budget scripts

 - Arm loss measurement 

 - Shnupp asymmetry measurement

  4629   Wed May 4 15:56:09 2011 valeraSummaryGeneralPSL and MC trends

The attached plot shows 2 day trends of the PMC and MC reflected and transmitted power, the PSL POS/ANG QPD signals, and the temperature measured by the dust counter.

The power step in the middle of the plot corresponds to Koji/Jenne PMC realignment yesterday.

It looks like everything is following the day/night temperature changes.

Attachment 1: pslmcdrift.pdf
  4632   Thu May 5 04:38:20 2011 KojiSummaryLSCComparison between S3399 and FFD-100

Comparison between Hamamatsu S3399 and Perkin Elmer FFD-100

These are the candidates for the BB PD for the green beat detection as well as aLIGO BB PD for 532nm/1064nm.

FFD-100 seems the good candidate.


Basic difference between S3399 and FFD-100

- S3399 Si PIN diode: 3mm dia., max bias = 30V, Cd=20pF

- FFD-100 Si PIN diode: 2.5mm dia., max bias = 100V, Cd=7pF


The circuit at the page 1 was used for the amplifier.

- FFD-100 showed 5dB (= x1.8) larger responsivity for 1064nm compared with S3399. (Plot not shown. Confirmed on the analyzer.)

- -3dB BW: S3399 180MHz, FFD-100 250MHz for 100V_bias. For 30V bias, they are similar.

Attachment 1: PD_response.pdf
PD_response.pdf PD_response.pdf PD_response.pdf
  4647   Thu May 5 18:38:01 2011 ranaSummaryCDSSub-system TRAMP adjustments

I think that the gain ramping time (_TRAMP) should be set to 1 second for all filter modules by default. We don't want them to switch instantaneously except in a few special cases.

So Jamie and I wrote a script (in scripts/general/) which sets all of these fields to 1 for a given system. The name of the system is an argument to the script. e.g.

>  setTRAMP LSC 1

The idea is that we set it once and then from then on, its captured by the autoBURT. Of course, we have to run this script each time we add new filter modules to a model.

  4649   Fri May 6 01:27:12 2011 KojiSummaryGeneralaLIGO BBPD / Green PD investigation

Minicircuits ERA-5SM was used for the RF amp of the BBPD. This amp is promising as a replacement of Teledyne Cougar AP389
as ERA-5SM gave us the best performance so far among the BBPDs I have ever tested for the aLIGO BBPD/Green.

The -3dB bandwidth of ~200MHz and the noise floor at the shotnoise level of 0.7mA DC current were obtained.

1. Introduction

The aLIGO BBPD candidate (LIGO Document D1002969-v7) employs Teledyne Cougar AP389 as an RF amplifier.
This PD design utilizes the 50Ohm termination of the RF amp as a transimpedance resistance at RF freq.

However, it turned out that the bandwidth of the transimpedance gets rather low when we use AP389, as seen in the attachment2.
The amplifier itself is broadband upto 250MHz (the transfer function was confirmed with 50Ohm source).
The reason is not understood but AP389 seems dislike current source. Rich suggested use of S-parameter measurement
to construct better model of the curcuit.

On the other hand, the RF amplifiers from Minicircuits (coaxial type like ZFL-1000LN+), in general, exhibit better compatibility with PDs.
If you open the amplifier case, you find ERA or MAR type monolithic amplifiers are used.

So the question is if we can replace AP389 by any of ERA or MAR.

2. Requirement for the RF amp

- The large gain of the RF amp is preffered as far as the output does not get saturated.

- The amplifier should be low noise so that we can detect shot noise (~1mA).

- The freq range of the useful signal is from 9MHz to 160MHz.

The advanced LIGO BBPD is supposed to be able to receive 50mW of IR or 15mW of 532nm. This approximately corresponds to
5mA of DC photocurrent if we assume FFD-100 for the photodiode. At the best (or worst) case, this 5mA has 100% intensity modulation.
If this current is converted to the votage through the 50Ohm input termination of the RF amp, we receive -2dBm of RF signal at maximum.

This gives us a dilemma. if the amp is low noise but the maximum output power is small, we can not put large amount of light
on the PD. If the amp has a high max output power (and a high gain), but the amp is not low noise, the PD has narrow power range
where we can observe the shotnoise above the electronics noise.

What we need is powerful, high gain, and low noise RF amplifier!

Teledyne Cougar AP389 was almost an ideal candidate before it shows unideal behavior with the PD.
Among Minicircuits ERA and MAR series, ERA-5 (or ERA-5SM) is the most compatible amplifier.

AP389 ERA-5
Freq Range 10-250MHz DC-4GHz
Gain >24.5dB 20dBtyp
Output power (1dB compression)
23dBm 18.4dBm
IP3 36dBm 33dBm
Noise Figure <3.3dB 3.5dB

Considering the difference of the gain, they are quite similar for our purpose. Both can handle upto -2dBm,
which is just the right amount for the possible maximum power we get from the 5mA of photocurrent.

3. Test circuit with ERA-5SM

A test circuit has been built (p.1 attachment #1) on a single sided prototype board. 

First, the transfer function was measured with FFD-100. With the bias 100V (max) the -3dB bandwidth of ~200MHz was observed.
This decreases down to 75MHz if the bias is 25V, which is the voltage supplied by the aLIGO BBPD circuit. The transimpedance
at the plateau was ~400Ohm.

Next, S3399 was tested with the circuit. With the bias 25V and 30V (max) the -3dB bandwidth of ~200MHz was obtained although
the responsivity of S3399 (i.e. A/W) at 1064nm is about factor of 2 smaller than that of FFD-100.

The noise levels were measured. There are many sprious peaks (possibly by unideal hand made board and insufficient power supply bypassing?).
Othewise, the floor level shows 0.7mA shotnoise level.

Attachment 1: PD_response.pdf
PD_response.pdf PD_response.pdf PD_response.pdf PD_response.pdf
Attachment 2: FFD-100_AP389_MCL.pdf
  4651   Fri May 6 10:20:00 2011 steveSummarySAFETY2011 safety audit

The emphasis of this annual safety audit  was on  safe  electrical housekeeping on March 3, 2011

Safety audit correction list for the electric shop:

1, install breaker panel door in room 101
2, install conduit- AC out let in the east arm for USB camera table and
    south arm for maglev- external fan
3, replace AC cord to south end work bench and door alarm
4, trace breaker of 1Y4

Requested completion date: 3-28-2011 at estimated cost $1,500.
All recommendations  for improvement were done by April 1, 2011
We thank the participants for making the 40m a safer  place to work.
Attachment 1: sa2011done1.pdf
Attachment 2: P1070448.JPG
  4658   Sat May 7 12:57:54 2011 KojiSummaryGeneralaLIGO BBPD / Green PD investigation

The RF amplifier of the prototype BBPD has been replaced from ERA-5SM to MAR-6SM.
The bandwidth is kept (~200MHz for S3399 with 30V_bias), and the noise level got better
while the maximum handling power was reduced.

MAR-6SM is a monolithic amplifier from Minicircuits. It is similar to ERA-5SM but has lower noise
and the lower output power.

AP389 ERA-5 MAR-6
Freq Range 10-250MHz DC-4GHz DC-2GHz
Gain >24.5dB 20dBtyp 21.8dBtyp
Output power (1dB comp.)
+23dBm +18.4dBm +3.7dBm
IP3 36dBm 33dBm 18.1dBm
Noise Figure <3.3dB 3.5dB 2.3dB

The noise floor corresponds to the shotnoise of the 0.4mA DC current.
Now the mess below 50MHz and between 90-110MHz should be cleaned up.
They are consistently present no matter how I change the PD/RF amp (ERA<->MAR)/bias voltage.

I should test the circuit with a different board and enhanced power/bias supply bypassing.

Discussion on the RF power (with M. Evans)

- Assume 5mA is the maximum RF (~50mW for 1064nm, ~15mW for 532nm). This is already plenty in terms of the amount of the light.

- 100% intenisty modulation for 5mA across 50Ohm induces -2dBm RF power input for the amplifier.

- Assume if we use MAR-6 for the preamplifier. The max input power is about -18dBm.
  This corresponds to 16% intensity modulation. It may be OK, if we have too strong intensity modulation, we can limit the power
  down to 0.8mA in the worst case. The shot noise will still be above the noise level.

- In the most of the applications, the RF power is rather small. (i.e. 40m green beat note would expected to be -31dBm on the RF amp input at the higherst, -50dBm in practice)
So probably we need more gain. If we can add 10-12dB more gain, that would be useful.

- What is the requirement for the power amplifier?

  • Gain: 10~12dB
  • Output (1dBcomp): +3dBm +Gain (13dBm~15dBm)
  • Noise level / Noise Figure: 3nV/rtHz or NF=14dB
    The output of MAR-6 has the votage level of ~7nV/rtHz. If we bring the power amplifier with input noise of ~3nV/rtHz,
    we can surppress the degradation of the input equivalent noise to the level of 10%. This corresponds to N.F. of 14dB.

Search result for Freq Range 10-200MHz / Max Gain 14dB / Max NF 15dB / Min Power Out 13dBm
GVA-81 is available at the 40m. ERA-4SM, ERA-6SM, HELA-10D are available at Downs.

Model Name Frequency [MHz] DC Power Case Style Price
Low High Current [mA] Volt [V]
ERA-4 DC 4000 65 4.5 VV105
ERA-4SM DC 4000 65 4.5 WW107
ERA-4XSM DC 4000 65 4.5 WW107
ERA-6 DC 4000 70 5 VV105
ERA-6SM DC 4000 70 5 WW107
GALI-6 DC 4000 70 5 DF782
GVA-81+ DC 7000 112 5 DF782
HELA-10C 5 450 525 12 CM624
HELA-10D 8 300 525 12 CM624

Freq Range DC-6GHz DC-4GHz DC-4GHz DC-4GHz
Gain 10.5dB 13.7dB 12.6dB 12.2dB
Output power (1dB comp.)
+19dBm +17.5dBm +17.1dBm +18.2dBm
IP3 42dBm 36dBm 36.5dBm 35.5dBm
Noise Figure 7.3dB 4dB 4.4dB 4.5dB


Conversion between nV/rtHz and NF (in the 50Ohm system)

SN1: Connect signal source (50Ohm output) to a 50Ohm load.
Power ratio between the noise and the signal

SN1 = (4 k T (R/2)) / (S/2)^2

SN2: Connect signal source (50Ohm output) to an RF amp.
Only the voltage noise was considered.

SN2 = (4 k T (R/2) + Vn^2) / (S/2)^2

10 Log10(SN2/SN1) = 10. Log10(1 + 2.42 (Vn / 1nVrtHz)^2)

Vn: 0 nVrtHz ==> 0dB
Vn: 0.5 nVrtHz ==> 2dB
Vn: 1 nVrtHz ==> 5dB
Vn: 2 nVrtHz ==> 10dB
Vn: 3 nVrtHz ==> 13.5dB

Attachment 1: PD_response.pdf
PD_response.pdf PD_response.pdf PD_response.pdf
  4771   Tue May 31 11:34:13 2011 steveSummarySAFETYsafety glasses checked

  1064 nm transmison were measured of 40m safety glasses as shown . Their performance did not degrade. They are as good as their labels.

Attachment 1: P1070823.JPG
  4779   Thu Jun 2 10:19:37 2011 Alex IvanovSummaryDAQinstalled new daqd (frame builder) program on fb (target/fb/daqd)

I hope that new daqd code will fix the problem with non-aligned at 16 seconds frame file GPS times.

I have compiled new daqd program under /opt/rtcds/caltech/c1/core/release/build/mx and installed it under

target/fb/daqd, then restarted daqd process on "fb" computer. It was installed with the ownership of user root

and I did chmod +s on it (set UID on execution bit). This was done in order to turn on some code to renice daqd process

to the value of -20 on the startup. Currently it runs as the lowest nice value (high priority).


controls@fb /opt/rtcds/caltech/c1/target/fb $ ls -alt daqd
-rwsr-sr-x 1 root controls 6592694 Jun  2 10:00 daqd


Backup daqd is here:


controls@fb /opt/rtcds/caltech/c1/target/fb $ ls -alt daqd.02jun11
-rwxr-xr-x 1 controls controls 6768158 Feb 21 11:30 daqd.02jun11



  4821   Wed Jun 15 01:30:38 2011 JamieSummaryLSCSchnupp asymmetry measurement

Measurement of Schnupp asymmetry

This was done by measuring the relative phase between the sidebands reflected from the two arms while the arm cavities are locked.

The Schnupp asymmetry is measured to be:   Lsa = 3.64 ± 0.32 cm



As a phase reference we use the zero crossing of the response function for the out-of-phase control signal for the single arm cavity lock [0]. The difference in the RD rotation phase of the response zero crossings indicates the phase difference in the sideband signals reflected from the arms. Assuming the asymmetry is less than half the RF modulation wavelength [1], the asymmetry is given by the following formula:

       \Delta \phi   c   1 
L_sa = ----------- ----- -
           360     f_RSB 2

We use a LSC digital lock-in to measure the response of the arm cavity at a single-frequency drive of it's end mirror.

[0] The locations of the zero crossings in the out-of-phase components of the response can be determined to higher precision than the maxima of the in-phase components.

[1] fRSB = 55 MHz,     c/fRSB/2 = 2.725 m


  1. Lock/tune the Y arm only.
    • We use AS55_I to lock the arms.
  2. Engage the LSC lock-in.
  3. Tune the lock-in parameters:
  4. lock-in freq: 103.1313 Hz
    I/Q filters:  0.1 Hz low-pass
    phase:        0 degrees
  5. Set as input to the lock-in the out-of-phase quadrature from the control RFPD.  In this case AS55_Q->LOCKIN.
  6. Drive the arm cavity end mirror by setting the LOCKIN->Y_arm element in the control matrix.
  7. Note the "RD Rotation" phase between the demodulated signals from the control PD (AS55)
  8. For some reasonable distribution of phases around the nominal "RD Rotation" value, measure the amplitude of the lock-in I output.
    • Assuming the Q output is nearly zero, it can be neglected.  In this case the Q amplitude was more than a factor of 10 less than the I amplitude.
    • Here we take 5 measurements, each separated by one over the measurement bandwidth (as determined by the lock-in low pass filter), in this case 10 seconds.  The figure above plots the mean of these measurements, and the error bars indicate the standard deviation.

The data and python data-taking and plotting scripts are attached.

Error Analysis:

To to determine the parameters of the response (which we know to be linear) we use a weighted linear least-squares fit to the data:

y = b X


X0j = 1
X1j = xj              # the measurement points
y = yi                 # the response
b = (b0, b1)     # line parameters

The weighting is given by the inverse of the measurement covariance matrix. Since we assume the measurements are independent, the matrix is diagonal and Wii = 1/\sigmai2 The
estimated parameter values are given by:

\beta  =  ( XT W X )-1 XT W y  =  ( X'T X' )-1 X'T y'

where X' = w X, y' = w y and wii = \sqrt{Wii}.

The X' and y' are calculated from the data and passed into the lstsq routine. The output is \beta.

The error on the parameters is described by the covariance matrix M\beta:

M\beta = ( XT W X)-1 = ( X'T X')-1

with correlation coefficients \rhoij = M\betaij / \sigmai / \sigmaj.

The x-axis crossing is then given by:

X(Y=0) = - \beta1 / \beta0


Valera's LLO measurement

Attachment 2: arm_phase.py
#!/usr/bin/env python

import sys
import os
import subprocess
import time
import pickle
from numpy import *
import nds
import matplotlib
... 229 more lines ...
Attachment 3: plot.py
#!/usr/bin/env python

import pickle
from numpy import *
import matplotlib
from matplotlib.pyplot import *


... 137 more lines ...
Attachment 4: schnupp_ETMX.pik
... 341 more lines ...
Attachment 5: schnupp_ETMY.pik
... 341 more lines ...
  4835   Mon Jun 20 00:59:02 2011 kiwamuSummaryGeneralWeekly report
This is a summary for the week ending June 19th. Feel free to edit this entry.
(Number of elog entries = 27)

* Refinement of LSC screen
    -> Kissel buttons and some indicators were newly installed
    -> A script to autonatically generate kissel buttons was made

* New BIO installed on ETMY

* LightWave for ABSL
    -> taken out from the MOPA box and put on the AP table with temporary use of the Y end laser controller
* Shipping 2 RFPDs to LLO
* LEDs on the BIO for the vertex suspensions were blown
    -> fixed and re-installed. A test script will be prepared
* PEM AA board was fixed
* A plot of the MICH noise was produced for the first time
* Schnupp asymmetry measurement : Las = 3.64+/-0.32cm
* The photo diode on WFS2 has been replaced by YAG-444-4A
* SUS binary IO crates were taken out
* Fiber died
     ->C1LSC was unable to communicate to C1SUS. Installing a new copper Dolphine fixed the issue.
* SURF students came
  4853   Wed Jun 22 12:24:44 2011 NicoleSummarySUSMidweek 2 Work Summary

I have made my transfer function model and posted it to the suspension wiki. Here is the link to my model!

Bode Plot Model

Please let me know if there need to be any adjustments, but I have posted the bode plots, a model image, and an explanation of why I think it's right! ^ ___^ V

I am currently working on the photo sensor circuit for the displacement detector. So far, I have gotten the infared LED to light up! ^ ___^ V

I am now trying to get a plot of forward voltage versus current for the LED. HOPEFULLY it will match the curve provided in the LED datasheet.

I'm using the bread board circuit box and when I'm not working at the bench, I have signs posted. PLEASE DO NOT REMOVE THE CONNECTIONS! It is

fine to move the bread board circuit box, but please do not disturb the connections > ____<

Here is a photo of the workspace


  4854   Wed Jun 22 12:29:57 2011 IshwitaSummaryAdaptive FilteringWeekly summary

I started on the 16th with a very intense lab tour & was fed with a large amount of data (I can't guarantee that I remember everything....)

Then... did some (not much) reading on filters since I'm dealing with seismic noise cancellation this summer with Jenne at the 40m lab.

I'll be using the Streckeisen STS-2 seismometers & I need to use the anti aliasing filter board that has the 4 pin lemo connectors with the seismometers & its boxes that require BNC connectors. I spent most of the time trying to solder the wires properly into the connectors. I was very slow in this as this is the first time I'm soldering anything.... & till now I've soldered 59 wires in the BNC connectors....



  4858   Wed Jun 22 18:41:23 2011 NicoleSummarySUSBROKEN bread board circuit box and L9337 LED Current Versus Voltage Curve

NOTE: The potentiometers on the bread board circuit box (the one I have been using with the signal generator, DC power, LED displays, and pulse switches) is BROKEN!

The potential across terminals 1 and 2 (also 2&3) fluctuates wildly and there dial does not affect the potential for the second potentiometer (the one with terminals 4, 5, and 6).

This has been confirmed by Koji and Jaimie.  PS I didn't break it! >____<


NEVERTHELESS, using individual resistors and the 500 ohm trim resistor, I have managed to get the current versus forward voltage plot for the Hamamatsu L9337 Infared LED


  4859   Wed Jun 22 18:50:45 2011 JamieSummaryGeneralJuly 2011 vent plan

Kiwamu and I have started to put together a vent plan on the 40m wiki:


We will keep working on this (there's still a *lot* to fill in), but please help fill in the plan by adding questions, answers, procedures, preparations, etc.


  4861   Wed Jun 22 21:36:41 2011 ranaSummaryGeneralJuly 2011 vent plan

I put a paper Peet's bag with half of the Mini-Moos into George.

  4875   Fri Jun 24 01:05:32 2011 NicoleSummarySUSTransfer Function Model Analysis Summary and New Posted LED V vs. I Curve

I have updated the TT suspension wiki to include a new page on my transfer function model. In this new page, an introduction and analysis of my transfer function (including a comparison of the transfer functions for a flexibly- and rigidly-supported damper) are included.  This page contains linear and logarithmic bode plots.  Here is a link to the transfer function page.


I have also updated my photosensor page on the TT suspension wiki so that the experimental data points in my current versus voltage plot are plotted against the curve provided by the Hamamtsu data sheet. I have also included an introduction and analysis for my mini-experiment with the forward voltage and forward current of the LED. Here is link to the photsosensor page.

  4890   Mon Jun 27 10:04:29 2011 kiwamuSummaryGeneralWeekly report

 Summary for the week ending June 26th.  (Number of elog entries = 53)

  A BIO installed on 1X2.
  A peak finding script was prepared for diagonalization of the OSEM input matrices
  The suspension readout coefficients were changed to have unit of [um] and [urad] in each signal.
    LWE NPRO controller was brought by Peter King.
    The I-P cuvre and beam profile was measured. Nominal current was chosen to 1.8 [A].
    The access tube between PSL and AS table was back in place.
   The REFL55 characterization was analyzed (impedance gain = 615 Ohm, shot noise intercept current = 1.59 mA )
- MC
   WFS1 check, the 29MHz resonance need to be adjusted.
   The MC locking gain was increased by 6 dB to avoid an oscillation at 30 kHz.
  The sensing matrices were measured in DRMI configuration and PRMI configuration
- Fiber experiment
   QPDY_PD was repositioned to accommodate the fiber stuff on the ETMY table.
   Succeeded in introducing the IR beam into the fiber coupler.
- TT characterization
    Th optic bench next to MC2 was cleaned up and leveled
- Vent list wiki page
   A wiki page was made for the vent detailed plan.
  A foton's malfunction was found. It can run correctly only on Pianosa.
  Some Dell machines were gone to Rod Luna
- 40m specfic safety training for the SURFs
  4908   Wed Jun 29 11:25:07 2011 NicoleSummarySUSWeekly Summary of Work

Update of Week 3 Work:

-I've finished reading The Art of Electronics Ch 1, 2, and 4.

-The mechanical stage for the horizontal displacement measurements is set up.

-I've opened up the circuit box for the quad photodiode and am currently working on the circuit diagram for the box and for the quad photodiode sensors.


Later this week, I plan to finish the circuit diagrams and figure out how the circuits work with the four inputs. I also plan to start working on my first

progress report.


  4913   Wed Jun 29 22:35:06 2011 NicoleSummarySUSCompleted Quad photodiode Box Circuit Diagrams

I have finished drawing the circuit diagrams for the quad photodiode boxes. Here are copies of the circuit diagram.

There are three main operation circuits in the quad photdiode box: a summing circuit (summing the contributions from the four inputs),

a Y output circuit (taking the difference between the input sums 3+2 and 1+4), and an X output circuit (taking the difference between the

input sums 3+4 and 1+2). I will complete an mini report on my examination and conclusions of the QPD circuit for the suspension wiki tomorrow.



  4915   Thu Jun 30 00:58:19 2011 KojiSummaryLSCLSC whitening filter test

[Jenne, Koji]

We have tested the LSC whitening filters. In summary, they show the transfer functions mostly as expected (15Hz zerox2, 150Hz pole x2).
Only CH26 (related to the slow channel "C1:LSC-PD9_I2_WhiteGain. VAL NMS", which has PD10I label in MEDM) showed different
phase response. Could it be an anti aliasing filter bypassed???

The 32 transfer functions obtained will be fit and summarized by the ZPK parameters.


The CDS system was used in order to get the transfer functions
- For this purpose, three filter modules ("LSC-XXX_I", "LSC-XXX_Q", "LSC-XXX_DC") were added to c1lsc
in order to allow us to access to the unused ADC channels. Those filter modules have terminated outputs.
The model was built and installed. FB was restarted in order to accomodate the new channels.

- Borrow a channel from ETMY UL coil output mon. Drag the cable from the ETMY rack to the LSC analog rack.
- Use 7 BNC Ts to split the signal in to 8 SMA cables.
- Put those 8 signals into each whitening filter module.

- The excitation signal was injected to C1:SUS-ETMY_ULCOIL_EXC by AWGGUI.
- The transfer functions were measured by DTT.
- The excitation signal was filtered by the filter zpk([150;150],[15;15],1,"n")
   so that the whitened output get flat so as to ensure the S/N of the measurement.

- For the switching, we have connected the CONTEC Binary Output Test board to the BIO adapter module
   in stead of the flat cable from the BIO card. This allow us to switch the individual channels manually.

- The whitening filters of 7 channels were turned on, while the last one is left turned off.
- We believe that the transfer functions are flat and equivalent if the filters are turned off.
- Use the "off" channel as the reference and measure the transfer functions of the other channels.
- This removes the effect of the anti imaging filter at ETMY.

- Once the measurement of the 7 channels are done, switch the role of the channels and take the transfer function for the remaining one channel.


- We found the following channel assignment

  • The ADC channels and the PDs. This was known and just a confirmation. 
  • The ADC channels and the WF filter on MEDM (and name of the slow channel)

- We found that the binary IO cable at the back of the whitening filter module for ADC CH00-CH07 were not connected properly.
This was because the pins of the backplane connector were bent. We fixed the pins and the connector has been properly inserted.

- CH26 (related to the slow channel "C1:LSC-PD9_I2_WhiteGain. VAL NMS", which has PD10I label in MEDM) showed different
phase response from the others although the amplitude response is identical.

Summary of the channel assignment (THEY ARE OBSOLETE - SEPT 20, 2011)

ADC                    Whitening Filter
CH  PD                 name in medm   related slow channel name for gain
00  POY11I             PD1I           C1:LSC-ASPD1_I_WhiteGain. VAL NMS
01  POY11Q             PD1Q          
02  POX11I             PD2I           C1:LSC-SPD1_I_WhiteGain. VAL NMS
03  POX11Q             PD2Q           C1:LSC-SPD1_Q_WhiteGain. VAL NMS
04  REFL11I            PD3I           C1:LSC-POB1_I_WhiteGain. VAL NMS
05  REFL11Q            PD3Q           C1:LSC-POB1_Q_WhiteGain. VAL NMS
06  AS11I              PD4I           C1:LSC-ASPD2_I_WhiteGain. VAL NMS
07  AS11Q              PD4Q           C1:LSC-ASPD2_Q_WhiteGain. VAL NMS
08  AS55I              AS55_I         C1:LSC-ASPD1DC_WhiteGain. VAL NMS
09  AS55Q              AS55_Q         C1:LSC-SPD1DC_WhiteGain. VAL NMS
10  REFL55I            PD3_DC         C1:LSC-POB1DC_WhiteGain. VAL NMS
11  REFL55Q            PD4_DC         C1:LSC-PD4DC_WhiteGain. VAL NMS
12  POP55I             PD5_DC         C1:LSC-PD5DC_WhiteGain. VAL NMS
13  POP55Q             PD7_DC         C1:LSC-PD7DC_WhiteGain. VAL NMS
14  REFL165I           PD9_DC         C1:LSC-PD9DC_WhiteGain. VAL NMS
15  REFL165Q           PD11_DC        C1:LSC-PD11DC_WhiteGain. VAL NMS
16  NC (named XXX_I)   PD5I           C1:LSC-SPD2_I_WhiteGain. VAL NMS
17  NC (named XXX_Q)   PD5Q           C1:LSC-SPD2_Q_WhiteGain. VAL NMS
18  AS165I             PD6I           C1:LSC-SPD3_I_WhiteGain. VAL NMS
19  AS165Q             PD6Q           C1:LSC-SPD3_Q_WhiteGain. VAL NMS
20  REFL33I            PD7I           C1:LSC-POB2_I_WhiteGain. VAL NMS
21  REFL33Q            PD7Q
           C1:LSC-POB2_Q_WhiteGain. VAL NMS
22  POP22I             PD8I
           C1:LSC-ASPD3_I_WhiteGain. VAL NMS
23  POP22Q             PD8Q
           C1:LSC-ASPD3_Q_WhiteGain. VAL NMS
24  POP110I            PD9I
           C1:LSC-PD9_I1_WhiteGain. VAL NMS
25  POP110Q            PD9Q
           C1:LSC-PD9_Q1_WhiteGain. VAL NMS
26  NC (named XXX_DC)  PD10I
          C1:LSC-PD9_I2_WhiteGain. VAL NMS
27  POPDC              PD10Q
          C1:LSC-PD9_Q2_WhiteGain. VAL NMS
28  POYDC              PD11I
          C1:LSC-PD11_I_WhiteGain. VAL NMS
29  POXDC              PD11Q
          C1:LSC-PD11_Q_WhiteGain. VAL NMS
30  REFLDC             PD12I
          C1:LSC-PD12_I_WhiteGain. VAL NMS
31  ASDC               ASDC
           C1:LSC-PD12_Q_WhiteGain. VAL NMS

Attachment 1: chans_24_31_WeirdPhase.pdf
Attachment 2: Octopus.jpg
Attachment 3: Test_Inputs_Plugged_In.jpg
Attachment 4: Contec_Tester_Board.jpg
  4934   Fri Jul 1 20:26:29 2011 ranaSummarySUSAll SUS Peaks have been fit

         MC1    MC2    MC3    ETMX   ETMY   ITMX   ITMY   PRM    SRM    BS     mean   std
Pitch   0.671  0.747  0.762  0.909  0.859  0.513  0.601  0.610  0.566  0.747  0.698  0.129
Yaw     0.807  0.819  0.846  0.828  0.894  0.832  0.856  0.832  0.808  0.792  0.831  0.029
Pos     0.968  0.970  0.980  1.038  0.983  0.967  0.988  0.999  0.962  0.958  0.981  0.024
Side    0.995  0.993  0.971  0.951  1.016  0.986  1.004  0.993  0.973  0.995  0.988  0.019

There is a large amount of variation in the frequencies, even though the suspensions are nominally all the same. I leave it to the suspension makers to ponder and explain.

Attachment 1: Screen_shot_2011-07-01_at_8.17.22_PM.png
  4936   Mon Jul 4 14:27:35 2011 kiwamuSummaryGeneralWeekly report

Summary of the week ending July 3rd.  Number of elog entries = 44 


   * The output TO_COIL matrix were simplified
   * Checked all the BO whitening switch => Only ITMY_UL didn't switch
   * All the DOF filters were normalized.
       => All the DOF filters are now ("3:0.0", "Cheby", "BounceRoll") 
       => The High pass should have 30Hz cut off ("30:0.0") ?
   * All the resonant peaks has been fit


   * MICH noise budget.
               => dominated by sensing noise.
   * The sensing matrix in the PRMI configuration was measured. 
               => The demodulation phase on AS55 seemed wrong. Need a doublecheck
   * A new screen, called C1LSC_OVERVIEW.adl, was released.

   * A channel name modification: "PRC" and "SRC" => "PRCL" and "SRCL" and etc.
   * The response of the LSC whitening filters were checked. 
                 => CH26 showed different phase response.

- MC work

 * Power budget on the AP table was made (in a high power situation).
REFL11 = 7.4 mW
REFL55 = 22 mW
        MCREFL = 114 mW
        WFS1   = 1.24 mW
        WFS2   = 2.7 mW
 * Measurement and adjustment of RFQPD response
         Resonance frequencies of WFS1 and WFS2 were adjusted. WFS1 and WFS2 were installed on the AP table
 * Started working on MCL path. 
         => needs some more CDS jobs to correctly assign ADC channels


 * Joe modified the automated scripts for producing model webviews


  * The alignment of the injection beam was done.

- Fiber experiment

 * A fiber was laid down from the ETMY table to the PSL table

- TT characterization

 * The mechanical stage for the horizontal displacement measurements is set up. 

- Configuration and other topics

      * Maglev stuff has gone to bridge lab.
      * Chris.W told us that the EPICS mutex issue can be solved by upgrading the EPICS version
      * All the PDs are stored in the east arm cabinet E4
      * Safety interlocks were connected to the ETMY laser and ABSL laser
      * Cshrc.40m was modified to make 32-bit machine happy
      * NDS2 buffer size on Mafalada had been too small and was increased somewhat such that we can still work for the SUS peak fit job
  4950   Wed Jul 6 23:53:38 2011 kiwamuSummaryGeneralminutes of 40m meeting
Attachment 1: meeting.pdf
meeting.pdf meeting.pdf
  4951   Thu Jul 7 02:23:59 2011 JenneSummaryLSCLSC Whitening Filters have been fit

I have fit all of the LSC whitening filters using vectfit4.m

All the data is in my folder ..../users/jenne/LSC_WhiteningTest_29June2011/

The zpk info is saved with each plot of the fit.  The pdfs are kind of huge to stitch together (or rather my computer doesn't want to do it), so I'll just post a representative one for now.


During the daytime either tomorrow or Friday I'll adjust the actual dewhitening filters to match the measured zpk values.

  4955   Thu Jul 7 15:34:44 2011 JenneSummaryLSCLSC Whitening Filters have been fit


During the daytime either tomorrow or Friday I'll adjust the actual dewhitening filters to match the measured zpk values.

 I made a handy-dandy table showing the zpk values for each whitening filter in the wiki: New whitening filter page

Next on the whitening filter to-do list: actually put these values into the dewhitening filters in foton.

  4956   Fri Jul 8 09:53:49 2011 Nicole SummarySUSSummer Progress Report 1

A copy of my summer progress report 1 has been uploaded to ligodcc 7/711 and I have just added a copy to the TTsuspension wiki


PDF copy of Summer Progress Report

  4969   Thu Jul 14 20:24:32 2011 NicoleSummarySUSPhotosensor Head Lessons

Today I tested the photosensor head combination (2 Hamamatsu S5971 photodiodes and 1 Hamamatsu L9337 LED). I discovered that I had burnt out the LED and the photodiodes when I soldered them to the PCB board.

After looking up soldering information on Hamamatsu photodiodes, I learned that I need to solder at least 2 mm away from the head. I checked the pins of my burnt-out photodiodes and I had soldered 1.5 mm away from the head. To prevent this problem from happening again, Suresh suggested that I clip a lead onto photodiode/LED pin while I solder on connections to help dissipate some of the heat.

Today I was able to get a single photodiode (not attached to the PCB) to measure light emitted from an LED and I observed how voltage fluctuated as I moved the photodiode around the LED.

Suresh and Jamie also helped me to fix my photosensor head design (to make it more electrically-stable). Originally, I had planned to solder the LED and photodiodes onto a PCB and to mount that PCB to the front of a small metal Pomona Electronics box (with a whole cut out for the photodiodes and LED) using spacers, screws, and nuts.  However, the PCB I am using to solder on the LED and photodiodes has metal connections that may cause problems for the LED and photodiodes lying on the surface. Now, the plan is to have the LED and photodiodes mounted to the PCB with an insulatory PCB in between. Below is an explanatory picture.  I will determine the placement of the LED and photodiodes after making screws holes in the two PCBs to attach to the metal face of the box. I want to attach the screw holes first to make sure that the PCBs (and attached photosensor) are centered.



  4970   Fri Jul 15 01:11:21 2011 KojiSummarySUSPhotosensor Head Lessons

Rotate the PDs and the LED so that you can put them as close as possible.
This is to increase the sensitivity of the sensor. Think why the closer the better.

  4971   Fri Jul 15 08:48:36 2011 JamieSummarySUSPhotosensor Head Lessons

Nicole: I thought we had decided to use teflon as the insulator between the PCB (yellow) and the LED/PDs?  I don't think you should use another circuit board with copper on it.  The copper will short the LED/PD heads to the metal box, which might be problematic.

Otherwise the design looks pretty good.  I think the PDs have three leads each, yes?

  4974   Fri Jul 15 14:23:30 2011 NicoleSummarySUSPhotosensor Head Lessons


 Ah! I see! Thank you!

I should put the LEDs and photodiodes closer together so that more of the reflected light falls on the photodiodes and the photodiodes have a higher response.

Also the reflectivity of the mirror will be optimized if the incident light is normal to the mirror surface. We will be setting up the photosensor and mirror so that the LEDs

emit light normal to the mirror surfaceDuring displacement, this light may be slightly off-normal but still close to normal incidence. We want the photodiodes to be close to the LED since we want

them to detect light that is close to the path of normal incidence (small angles of reflection). [Thanks to Jenne for helping me figure this one out!]


Thank you for the suggestion ^___^

  4975   Fri Jul 15 14:29:30 2011 NicoleSummarySUSPhotosensor Head Lessons


 You are right Jamie! Thank you for the correction! I will now use the Teflon sheet instead of the PCB piece.

The photodiodes do have three legs, but I imagined the third one lying on a different plane, since it is spaced apart from the two I have drawn.

I should include this third leg in my drawing?

  5000   Wed Jul 20 12:05:08 2011 NicoleSummarySUSWeekly Summary

Since last week Wednesday, I have since found a Pomona Electronics box (thanks to Jenne)

to use for my photosensor head circuit (to house the LED and 2 photodiodes). Suresh has

shown me how to use the 9-pin Dsub connector punch, and I have punched a hole in this box

to attach the Dsub connector. 


Since this past entry regarding my mechanical design for the photosensor head (Photosensor Head Lessons),

I have modified the design to use a Teflon sheet instead of a copper PCB and I have moved the LED

and photodiodes closer together, upon the suggestions of Jamie and Koji.  The distance between

components is now 0.112" instead of the initial 0.28".  Last night, I cut the PCB board for the LED

and photodiodes and I drilled holes onto the PCB board and Teflon sheet so that the two may be

mounted to the metal plate face of the Pomona box.  I still need to cut the viewer hole for and

drill screws into the face plate.


I have also been attempting to debug my photosensor circuit (box and LED/photodiode combination).

Since this last entry (Painful Votlage Regulator and Circuit Lessons), Suresh has helped me to get the parts

that I need from the Downs Electronics lab (15 wire ribbon cable, two 9 pin D-sub connectors M,

one 15 pin D-sub connector M, one 16 pin IDC connector). Upon the suggestion of Jamie, I have

also made additional safety changes to the circuit by fixing some of the soldering connections

so that all connections are done with wires (I had a few immediate lines connected with solder).

I believe the the photosensor circuit box is finally ready for testing. I may just need some help

attaching the IDC connector to the ribbon cable. After this, I would like to resume SAFELY

testing my circuit.


I have also been exploring SimMechanics. Unfortunately, I haven't been able to run the

inverted pendulum model by Sekiguchi Takanori. Everytime I attempt to run it, it says

there is an error and it shuts down Matlab. In the meanwhile, I have been watching

SimMechanics demos and trying to understand how to build a model. I'm thinking that

maybe once I figure out how SimMechanics works, I can use the image of his model

(I can see the model but it will not run) to construct a similar one that will hopefully work.


I have also been attempting to figure out the circuitry for the pre-assembled

accelerometer (made with the LIS3106AL chip).  I have been trying to use a multi-meter

to figure out what the components are (beyond the accelerometer chip, which I have

printed out the datasheet for), but have been unsuccessful at that. I have figured out

that the small 5 pin chip says LAMR and is a voltage regulator. I am hoping that if I can

find the data sheet for this voltage regulator, I can figure out the circuitry. Unfortunately,

I cannot find any datasheets for a LAMR voltage regulator. There is one by LAMAR, but

the ones I have seen are all much larger. Does anyone know what the miniature voltage

regulator below is called and if "LAMR" is short for "LAMAR"?




  5003   Wed Jul 20 18:44:54 2011 KojiSummarySUSWeekly Summary

Find Frank and ask him about those components.

  5022   Sun Jul 24 20:36:03 2011 haixingSummaryElectronicsAA filter tolerance analysis

Koji and Haixing,

We did a tolerance analysis to specify the conner frequency for passive low-pass filtering in the AA filter of Cymac. The
link to the wiki page for the AA filter goes as follows (one can have a look at the simple schematics):

Basically, we want to add the following passive low-pass filter (boxed) before connecting to the instrumentation amplifier:


Suppose (i) we have 10% error in the capacitor value and (ii) we want to have common-mode rejection
error to be smaller than 0.1% at low frequencies (up to the sampling frequency 64kHz), what would be
conner frequency, or equivalently the values for the capacitor and resistor, for the low-pass filter?

Given the transfer function for this low-pass filter:
transfer_function.png     f0.png
and the error propagation equation for its magnitude:
we found that the conner frequency needs to be around 640kHz in order to have
DT.pngwith Dc.png

  5023   Sun Jul 24 20:47:21 2011 ranaSummaryElectronicsAA filter tolerance analysis

This is sort of OK, except the capacitor connects across the (+) terminals of the two input opamps, and does not connect to ground.

Also, we don't care about the CMRR at 64 kHz. We care about it at up to 10 kHz, but not above. The sample frequency of the ADC is 64 kHz, but all of the models run at 16 kHz or less, so the Nyquist frequency is 8 kHz.

And doesn't the value depend on the resistors?

  5024   Sun Jul 24 22:19:19 2011 haixingSummaryElectronicsAA filter tolerance analysis


>> This sort of OK, except the capacitor connects across the (+) terminals of the two input opamps, and does not connect to ground:



>> Also, we don't care about the CMRR at 64 kHz. We care about it at up to 10 kHz, but not above.

In this case, the conner frequency for the low-pass filter would be around 100kHz in order to satisfy the requirement.

>>And doesn't the value depend on the resistors?

Yes, it does. The error in the resistor (typically 0.1%)  is much smaller than that of the capacitor (10%). Since the resistor error propagates in the same as the capacitor,
we can ignore it.

Note that we only specify the conner frequency (=1/RC) instead of R and C specifically from the tolerance analysis, we still need to choose appropriate
values for R and C with the conner frequency fixed to be around 100kHz, for which we need to consider the output impedance of port 1 and port 2.



  5026   Mon Jul 25 11:02:19 2011 kiwamuSummaryGeneralWeekly report

 Summary of the week ending July 10th.  Number of elog entries = 21


 + The cutoff frequency of the high pass filters for the damping were set to 30Hz.
 + Turned off all the BounceRoll filters.
 + The BS oplev was checked and seemed healthy.


 + All the measred data of the LSC whitening filters were fit.
 + All the zpk parameters are recorded on the wiki.



+ The setup completed.  
 + The freqeucy-lock of the ABSL laser was achieved with UGF of ~ 40kHz.
 + The temperature of the ABSL laser was adjusted to be 47.25 deg


 (Fiber experiment)
 + The I-P curve of the ETMY laser was measred.
 + The current set point is 1.8 [A], which used to be 1.5 [A], corresponding to the output of power of 197 [mW] and 390 [mW] respectively.

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