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ID Date Authordown Type Category Subject
  9059   Fri Aug 23 21:01:38 2013 Alex ColeHowToElectronicsAutomated Photodetector Frequency Response System

 This post describes how to use the Automated Photodetector Frequency Response System.

On the mechanical side, turn on:

-the diode laser (in rack 1Y1)

-the RF Switch (in rack 1Y1)

-the reference PD (under the POY table)

-the AG4395A Network Analyzer

The NA’s RF output should go to the laser’s modulation input, the reference PD’s output should go to the NA’s R input, and the RF Switch Chassis’s output (which is the combination of the two switches’ COM channels using a splitter) should go to the NA’s A input.

Once this is done, navigate into /users/alex.cole and run PDFR.sh. This script collects data for each photodetector under consideration by switching using a python script and communicating with the NA via GPIB. It then sends all the data to RF.m, which fits the functions, plots the latest data against canonical data, and saves the plots to file.

The fitting function, fit.m, also outputs peak frequency to the command line. This function uses PD name data (e.g. ‘REFL33’) to choose an interval with minimal noise to fit.

The main script prompts the user to press enter after each NA sweep to make sure that measurements don’t get interrupted/put out of order by RF switching.

Once you're done, you should turn off the laser, NA, RF Switch, and reference PD.


Sometimes, the NA throws up and doesn’t feel like running a particular sweep. If this happens, it’s a good idea to keep the matlab script from trying to analyze this PD’s data. Do this by opening up RF.m and commenting out the calls to ‘fit’ and ‘canonical’ for that PD.

If fit.m complains about a particular set of data, it is often the case that the N/P ratio (where N is order of approximation and P is number of points in the interval) is too high. You can fix this by reducing N or making the PD’s frequency range (chosen in the fnew_idx line) larger.

Choosing a single PD

If you only want to grab the transfer function for one PD, first look up which switch input it belongs to. This information is contained in /users/alex.cole/switchList. To turn the switch to a particular input, type something like:

python rf.py “ch7”

This command uses TCP/IP to tell the switch to look at channel 7. Switch input numbers range from 1 to 16, though not all of them are in use.

Once the switch is looking at the correct input, you can run a sweep and download the data by typing /opt/rtcds/caltech/c1/scripts/general/netgpibdata/NWAG4395A -s 1000000 -e 500000000 -c 499000000 -f [filestem for output] -d [path of directory for output] -i -g 10 -x 15. 

  8795   Wed Jul 3 11:07:17 2013 AlexSummary Photodetector Characterization

 [Alex, Koji]

We characterized Koji's BBPD MOD for REFL165 (see attachment).

First, we calibrated the Agilent 4395 Network Analyzer (NA) to account for differences in cable features between the Ref PD and Test PD connections. This was done using the 'Cal' softkey on the NA. 

Then we performed transimpedance measurements for the test PD and reference PD relative to the RF output of the NA and relative to each other (see 2nd attachment. Note that the NA's RF output is split and sent to both the IR Laser and the NA's Ref input).

Next, we made DC measurements of the outputs of the photodetectors to estimate the photocurrent distribution of the transimpedance setup (like the 2nd attachment, but with the outputs of the PDs going to a multimeter). By photocurrent distribution, we mean how the beamsplitter and respective quantum efficiencies/generalized impedance/etc. of the PDs influence how much current flows through each PD at with a DC input.

Finally, we measured the output noise as a function of photocurrent (like the 2nd attachment, but with a lightbulb instead of the IR Laser). Input voltages for the lightbulb ranged from 0mV to 6V. Data was downloaded from the NA using netgpibdata from the scripts directory. Analysis is currently in progress; graphs to come soon.


Attachment 1: BBPD_PCB.pdf
Attachment 2: transimpedance_measurement.pdf
  8806   Mon Jul 8 16:27:49 2013 AlexUpdate Planned rack additions

Alex and Eric

For the photodetector frequency response automation project, we plan to add modules to rack 1y1 as shown in the attached picture (Note: boxes are approximately to scale). 

The RF switch will choose which photodetector's output is sent to the Agilent 4395A Network Analyzer.

The Diode Laser Module is powered by Laser Power Supply, will be modulated by the Network Analyzer and will be output to a 1x16 optical splitter which is already mounted in another rack (not pictured). 

The Transformer Module has not been built yet.

We would like to install the power supply and the laser module tomorrow and will not begin routing fibers and cables until we post a drawing in the elog.

Also, our reference photoreceiver arrived today.


Attachment 1: Annotated_Rack_1y1.pdf
  8829   Thu Jul 11 12:00:50 2013 AlexUpdate Planned rack additions

[Eric, Alex]

We mounted our Laser Module and Laser Power Source in rack 1y1. We plan to add our RF Switch and Transformer Module to the rack, as pictured. (Note: drawn-in boxes in picture are approximately to scale.) Note that the panel of knobs which the gray boxes overlap is obsolete and will soon be removed.

Attachment 1: Annotated_Rack_1y1_-_update.pdf
  8849   Mon Jul 15 16:44:46 2013 AlexUpdateOMCOMC North Safety

 [Eric Alex]

We are planning on testing our laser module soon, so we have added aluminum foil and a safety announcement to the door of OMC North. The safety announcement is as pictured in the attachment.

Attachment 1: photo_2_(1).JPG
  8850   Mon Jul 15 16:51:37 2013 AlexConfiguration Planned AS Table addition

 [Eric, Alex]

We are planning to add our reference PD to the southern third of the AS Table as pictured in the attachment. The power supply will go under the table.

Attachment 1: AS_Table_Ref_PD_Addition.pdf
  17422   Wed Jan 25 16:58:19 2023 AlexUpdateCamerasRecording CCD cameras

Thus far, the software needed for the Magewell video encoder has been successfully installed on Donatella. OBS studio has also been installed and works correctly. OBS will be the video recording software that can be interfaced via command line once the SDI video encoder starts working. (https://github.com/muesli/obs-cli)

So far, the camera can not be connected to the Magewell encoder. The encoder continues to have a pulsing error light that indicates "no signal" or "signal not locked". I have begun testing on a secondary camera, directly connected to the Magewell encoder with similar errors. This may be able to be resolved once more information about the camera and its specifications/resolution is uncovered. At this time I have not found any details on the LCL-902K by Watec that was given to me by Koji. I will begin looking into the model used in the 40 meter next.

  17441   Wed Feb 1 16:53:55 2023 AlexSummaryGeneralShadowing Anchal on developing a change for the c1ioo CDS computer

During my time shadowing Anchal, we discussed the need for digital control systems on the suspension systems for the 40 meter optics. The controls and diagnostics system (CDS) allows us to develop our own feedback controls and filters for the suspension systems by taking in analog signals from the shadow sensors. The feedback control system developed in the CDS then utilizes the OSEM actuators to dampen harmonic motion and noise on the suspension lines. While improving these feedback loops is an ongoing challenge, it is a problem that is likely non-linear, meaning the system must be understood on a much higher level to make further improvements. This brings us to the new addition of a wavefront sensor in the 40m lab, which will allow for constant monitoring of the active wavefront in the interferometer. The wavefront will soon be used for gathering training data for a neural net that will help further analyze the non-linear effects within the suspension and damping system. What Anchal was working on today was an update within a CDS model for clioo to allow for the integration of the wavefront sensor such that he may use a switch to change between connections in the mode cleaner and the arm cavity. The CDS models may be edited and updated using Matlab/Simulink to arrange blocks and code in a robust and visual manner. The final system designed in Simulink can then be saved and compiled using the real-time code generator (RCG), which cross-compiles the Simulink file into C code that can be read by the CDS system to assign inputs, outputs, and various logic or algorithms for filtering.

  17459   Thu Feb 9 11:07:38 2023 AlexUpdateCDSAdding callibration filters to c1sus

Today I updated the ETMY suspension model to include 4 new filters at the output of the position, pitch, yaw and side summers and before the "To Coil Matrix". The library that was changed and updated is "sus_single_control_new". These callibration filters are labeled in the orange box as POSCAL, PITCAL, YAWCAL, and SIDECAL. The four filters are important as the will allow us to callibrate the position and side from counts to micro meters, and pitch and yaw from counts to micro radians.

The next steps for utilizing this update will be

    - create a few experiments to find the callibration constants for the 4 degrees of freedom

    - edit and update the ETMY Suspension screen to include selectable filter boxes to implement the callibration constants


For future reference, preform the update and restore the models to their previous states you may use the following:

to install the models we ssh into the computers running the ETMY suspension models (for example)

     ssh c1sus

then for each model using the suspension library (we used c1sus c1mcs c1scx c1scy c1su2 c1su3) do

     rtcds build-install c1sus

the watchdogs will need to be shut down for c1sus and the model will need to be restarted next

     rtcds restart c1sus

Now we restore the filter values to the last saved point (about an hour before the update) in cds folder

     python burtRestoreRTSepics.py -m c1sus c1mcs c1scx c1scy c1su2 c1su3 -o 10

Last we reset the watchdogs again using the following script in SUS>medm

     python resetFromWatchdogTrip.py MC1 MC2 MC3 BS PRM SRM ITMX ITMY ETMX ETMY

  17471   Thu Feb 16 23:54:11 2023 AlexUpdateDaily ProgressYaw and Pitch Calibration constants for ETMY op-lev

This work was done by Ancal and I. 

To recallibrate the op-lev for ETMY, a python script was first written to calculate the change in distance in x or y that the photodiode array will see when the mirror incurs a change in yaw or pitch. The python script approximates d by integrating, using a reimann sum, the area under a gaussian curve, given by I(r)= Iexp(−2r2/ 2w(z)2), where r is the radial position, and w(z) is the waist (radius) size of the gaussian beam where power reaches 1/eof its maximum. The distance d, is the difference from the center of the gaussian to the point at which the beam profile has a normalized area under the curve equal to that of the percent of the beam profile showing on one half of the circular photodiode array.

     Above, the gaussian is related to the translation of the beam profile on the photodiode where the area calculated under the curve of the gaussian, is equivalent to the ratio of the beam profile in 2 adjacent quaters of the photodiode array. 

The gaussian, is directly related to the waist size of the laser beam profile, and thus a beam profiler was used to calculate the waist size over an average of 100 takes. Due to the thickness of the beam profiler, we were unable to get a direct measurement of the size of the beam at the exact location of the photodiode. Instead, we took two seperate measurements while moving the profiler 1 inch further away from the photodiode and back calculated the average size of the beam at the photodiode assuming that at this distance away from the source, the beams width would expand linearly. This provided a 2*waist size of 1625 ± 40 um. 

     image above displays the laser beam profiler used to approximate the waist size of the op-lev laser.

The physically calculated translation of the beam profile, d, can then be used to determine the overall angle, theta, that the mirror has moved to create this offset. The relation between distance and theta is Theta = d/2R, where R is the length from the mirror surface to the photodiode. R was then measured by hand over the optics table, and estimated to the best of our ability using the accurate autocad drawings of ETMY. This provided us with an R length of 1.76 ± 0.02 meters. 

     Image above shows the current system in place for converting the photodiode counts into microradians. The calibration constant is implemented at the last green filter boxes for pitch and yaw. 

Lastly, to calculate the callibration constants, a series of tests were run on the ETMY suspeneded mirror. First, a time averaged value of the photodiode counts was taken with the mirror locked in place. Next, pitch and yaw were adjusted by 10 counts seperately, and the photodiode outputs recorded. This was done again but by moving the mirror 50 counts in pitch and yaw (seperately). The final result of the difference of the calculated theta values over the difference of pitch or yaw counts provided the following callibration constants:

      Pitch moved +10 counts: 131 ± 5 cts/urad

      Pitch moved +50 counts: 155 ± 5 cts/urad

      Yaw moved +10 counts: 237 ± 5 cts/urad

      Yaw moved +50 counts: 241 ± 5 cts/urad

Given our results, we believe that the values found for our 50 count translation to be the best approximation of the calibration constant due to its movement being more significant than that of the change seen from adjusting yaw or pitch by only 10 counts. 

Next steps will be to update the values in the controls system and improve the python script to be more autonomous rather than a a step by step calculation. 


  17477   Wed Feb 22 23:40:48 2023 AlexUpdateCalibrationAdding calibration constants for sus matrix and filter control buttons to the sus control screen

The callibration constants were updated for the oplev pitch and yaw. The values were changed as denoted in 17471 were:

     PITH: 175.7→ 155 cts/urad

     YAW: 193 → 241 cts/urad

To make these changes for the oplev callibration constants I went to ETMY - SELECTED OPLEV SERVO BOX

I then opened OLMATRIX and turned off PITCH and YAW servos in the ETMY SUSPENSION SCREEN such that the system does not attempt to actively make corrections while values are being changed. 

Then I adjusted the matrix to include our updated calibration constants and reinitiated the oplev ptich and yaw servo's

This updated the calibration constants for everything


The next change that was made was the addition of the calibration filters for position, pitch, yaw and side into the sitemap view for the suspension systems.

Adding calibration filters will allow us to callibrate the pos, pitch, yaw, and side to true values of urad and umeters (see 17459)

The final screen may be seen bellow (the updated area is outlined in red):


When each of the filter buttons is clicked, the following screen will now appear (circled in yellow is the calibration constant gain we will be calculating and entering into the system):


To create the edits to the controls screen we must complete the following process

We can edit the original screen - right click > evaluate > edit this screen

Then I adjusted the width of the overall screen, and moved the right half of the modules over to the right so I could fit in some filter buttons. I then Navigated to the c1ioo wfs master screen using the open feature to copy a pre existing filter module

I then adjusted the filter module and its contents to correspond to the features and autogenerated model files from RTCDS

There was some rearranging and adjusting needed to get these files in place first. The autogenerated files from the RTCDS can be found in dir = "/opt/rtcds/caltech/c1/medm/c1sus/"

They were autogenerated with names "C1SUS_BS_PITCAL.adl", "C1SUS_BS_POSCAL.adl", "C1SUS_BS_YAWCAL.adl","C1SUS_BS_SIDECAL.adl" 

We copied these files to dir = "/opt/rtcds/userapps/trunk/sus/c1/medm/templates/NEW_SUS_SCREENS/"

The file names were changed to "SUS_PITCAL.adl", "SUS_POSCAL.adl", "SUS_YAWCAL.adl", "SUS_SIDECAL.adl" 

The directory we placed them in is where the models for c1 sus can be found that are referenced by the sitemap suspension monitor screen

Each file was then opened in Vscode and a few changes were made such that the specific naming values referenced by the different screens of the sitemap and different optics, are replaced by the overarching values seen in each instance of the screens.

There are approximately 50 referenced file names of "C1:SUS-BS_PITCAL" etc. In each instance we made the following changes:

"-BS" was changed to "-$(OPTIC)"

"C1:" was changed to "$(IFO):"

The new strings should read "$(IFO):SUS-$(OPTIC)_PITCAL"

Once this change was made we can now right click on the filter module box, click on "Label/Name/Args" button

In the display file, we must add the path name for the calibration directory "/opt/rtcds/userapps/trunk/sus/c1/medm/templates/NEW_SUS_SCREENS/SUS_POSCAL.adl"

And for the arguments box we will enter OPTIC=$(OPTIC), IFO=$(IFO)

You can also copy and paste the directory names in the file boxes using right click copy from the file manager and paste into the box using a single click of the mouse scroller wheel

Lastly, the PV limits were changed for each number output right click value box > PV limits > Precision > Source changed to "Default" with a value of 1.

The shown value of the position, pitch, yaw, and side was then changed to show the output from the newly added filter. This is done also by right clicking the value box and adjusting the "Readback Channel".

Value changed from "$(IFO):SUS-$(OPTIC)_TO_COIL_1_#_INMON" to the outputs from the filters which are

       "$(IFO):SUS-$(OPTIC)_POSCAL_OUTMON" (for others changing POSCAL to the appropriate variable)

This is how to edit and add the Medm screens for single suspension optics into the sitemap IFO SUS screen


Lastly, Tomohiro and I worked on acquiring 6 data sets from DC stepping through adjustments in pitch and yaw for MC1, MC2 and MC3. These datasets will be fit quadratically and combined with more tests dine by AC driving the stepper motors tomorrow to find the calibration constants for the mirrors.

Attachment 2: InkedScreenshot_2023-02-22_18-28-41.jpg
Attachment 3: InkedScreenshot_2023-02-22_18-29-00.jpg
  17481   Fri Feb 24 13:29:16 2023 AlexSummaryIMCUpdated angular actuation calibration for IMC mirrors

Also reply to: 40m/17352

Tomohiro, Anchal, and I did the following to make updates to the calibration constants for pitch and yaw on MC1, MC2 and MC3.

To acquire the data used for fitting a curve respective to the change in counts per change in mirror pitch and yaw, we utilized some code that Anchal has already developed.

The scripts used to take time averaged data points of the IMC mirrors can be found by entering the command $ s into a terminal window to enter the scripts folder. Then enter the path "SUS/angActCal"

The following scripts will be found there to be used for this experiment:

angActCal.py & parabolaFit.py

To take data we used the angActCal.py function with set values for the time averaging = 5 s, settle time = 5 s, and adjusted the offset such that we would acquire approximately 20 data points given our ASC Bias limits. We defined the limits for each plot based on where the transmission fall off from the maximum value reached an average range of 10,000 counts.

The "readChannel" for each was the "C1:IOO-MC_TRANS_SUMFILT_OUTPUT" and can be found from the site map at IOO>Lock MC> see MC2_TRANS

The adjustment channels for Pitch and yaw on each IMC mirror were entered as the offset value found in the IMC screen at ALIGNMENT OFFSETS > BIASPIT/BIASYAW > OFFSET

For the code to work, the offset switch must be turned on. parabolaFit.py 

The data from MC1, MC2, and MC3 for pitch and yaw was saved to individual text files which were then entered into the parabolaFit.py function to get the results seen in attachment 1 and 2.


The above images show the printout from the plot fitting function and one of the graphs produced.

Optic ACT

Fit curve factor for DC (1/cts^2)


2.41 +/- 0.01 e-3


4.12 +/- 0.02 e-3


5.75 +/- 0.03 e-3


8.48 +/- 0.13 e-3


1.83 +/- 0.03 e-3


4.52 +/- 0.05 e-3

From the fitted curve values we then derived the equations that will soon be described further by Tomohiro (see entry _____) to arrive at the final callibration constants.


Optic ACT

Callibration constant at DC (urad/cts)


12.66 +/- 0.03


6.64 +/- 0.02


lock6.83 +/- 0.02


4.69 +/- 0.04


11.03 +/- 0.09


6.96 +/- 0.04

Final Calibration Constants for MC1, MC2, & MC3


We then utilized our calculated calibration constants (as seen bellow) to adjust the following filter parameters in the IMC control panel.


To make the updates such that the IMC screens show the correct urad values at the output of the filter banks, we must do the following steps to MC1, MC2, and MC3:

First, to make changes to our calibration filters, we must first shut off the pitch and yaw feedback loop controls.

TO do so for the Lock Filters, we will set the pitch and yaw SUS ASC inputs to 0 but entering the sitemap > IOO > C1IOO_WFS_MASTER

Nex head to action at the top right, and we can select "MC WFS relief 60s", this will relieve the values from the pitch and yaw inputs to the 40m Mode Cleaner Alignment settings to save the overall alignment and allow us to turn off the WFS servos to make the necessary adjustments on the lock filters.

Once we have waited a sufficient amount of time for the values on the ASC inputs to hover around 0, select Turn WFS ON/OFF button and choose "Turn OFF MCWFS Servo"


Next, we will press on the "on/off" button (see attachment 3 - circled in orange) for pitch and yaw found in just the LOCK FILTERS windows.

Once these are off we will stay in the same screen and adjust the gain values (boxed in yellow) for pitch and yaw.

Next, we will take the current value and divide it by the newly found corresponding calibration constant. This is to adjust for the changes we will be making on the output end of the filter banks such that all values in the feedback controls are normalized to the same scale.

The changes made here can be seen bellow:


Damp Filter Orig

Damp Filter NEW

Lock Filter Orig

Lock Filter New
































Now that these changes have been made in the damp and lock filter banks, with the pitch and yaw feedback loops STILL OFF, we may adjust the newly made calibration filters for pitch and yaw (as seen in attachment 4).

The "P" and "Y" filters may be opened (boxed in red) and we may adjust the gain (circled in yellow). Because each of these filters have just been created, the value is set to 1. This value can be completely replaced with the calibration constant found in our table above. Thus we will now change MC1 Pitch to have a "gain" of 12.66 and so forth.

Once each of the calibration filters have been updated, you may go back into the damp filters and reinitiate the feedback loops.

Once all values have been entered,

This concludes the updating of the IMC filter calibration constants at DC.

Attachment 1: angActCal_C1-SUS-MC1_BIASPIT_OFFSET_to_C1-IOO-MC_TRANS_SUMFILT_OUT_1361152703.png
Attachment 2: Screenshot_2023-02-23_16-47-58.png
Attachment 3: InkedScreenshot_2023-02-23_17-02-13.jpg
Attachment 4: InkedScreenshot_2023-02-23_17-02-49.jpg
  17484   Sun Feb 26 00:13:55 2023 AlexConfigurationASCIOO MC PIT/YAW gain change

The following changes were made to the WFS MASTER IMC Pitch and Yaw gains:

Gain values for the pitch and yaw on MC1, MC2, and MC3 filters on the SUS ASC inputs have been carried over to the WFS MASTER output filters.
This was done such that Tomohiro and I could take AC measurements at an oscillation freq of 77 Hz on the pitch and yaw mirrors, while being sure that the amplitude of the AC signal being applied to each mirror is the same. The filters on the WFS output will have gains changed from 1.0 to the previously mentioned calibration values described in ELOG 17481

The values calculated for each filter were inverses of the callibration constants. The filters at the SUS ASC inputs were modified to read gain values of 1.0 again.
See the table bellow for the values passed to each filter.
In summary:
originally IOO-MC1,2,3_PIT/YAW_GAIN = 1.0. Now:



IOO-MC1,2,3_PIT/YAW_GAIN >> 1.0

  17486   Wed Mar 1 17:13:38 2023 AlexUpdateIMCTransfer Function for IMC mirrors using sine sweep

The following work has been done by Tomohiro, Anchal and I:

To acquire the transfer functions for each of the IMC mirrors, we utilized diaggui, the CDS Diagnostic Test tool. We would like to measure the open loop transfer function, which is the ratio of In1 and In2, corresponding to before and after the injection point of the excitation signal.

A sinusoidal excitation signal was swept from 0,2 Hz to 5 Hz and includes 11 data points from an average of 10 cylcles per point.

NOTE: the WFS gain must be adjusted from 1.0 to 4.0 for these measurements (this is the slider underneath the "Turn WFS ON/OFF" button in C1:IOO_WFS_MASTER.

For the three sets of data taken for Pitch in WFS1, WFS2, and MC2 Trans, the amplitude of the excitation wave was 30,000.

In each measurement, the injection point is "C1:IOO-X_EXCMON", where X is the WFS or MC2 + Pitch or Yaw.


We will be conculding our measurements tomorrow and will report the findings for YAW in WFS1, WFS2, and MC Trans2.

Attachment 1: WFS1_PIT_OLTF.pdf
Attachment 2: WFS2_PIT_OLTF.pdf
Attachment 3: MC2_TRANS_PIT_OLTF.pdf
  17500   Thu Mar 9 10:29:15 2023 AlexUpdateIMCStep response test on MC1, MC2, and MC3 YAW

Tomohiro, Anchal and I completed the following processs for acquiring a new Output Yaw matrix for the "C1IOO_WFS_OUTMATRIX".

To did this by following the same process in 17493 but instead of adding our offsets in the WFS1, WFS2 and MC Trans filter banks, offsets were added at the end of the feedback loop at the optics, MC1, MC2 and MC3 YAW.

Optimal offset values were found such that the offset change did not disrupt the output WFS transmission signal by more than about a one thousand counts. Each limit was set to come close to this limit.

Our final offset values were:


Offset Value

MC1 55
MC2 15
MC3 35

The step response was than observed in Diaggui, but the entire 800 s run was unable to be viewed at once. We then utilized our python script from the previous step response data that we took to develop the following:

The measured response from stepping the optics was:

\begin{pmatrix} 1.31\pm0.24 & 54.2\pm1.3 & -0.28\pm0.03\\ -2.13\pm0.23 & -20.7\pm1.6 & 1.11\pm0.03\\ 1.82\pm0.27 & -25.8\pm1.5 & 0.16\pm0.03\\ \end{pmatrix} \begin{pmatrix} MC_{1Y}\\ MC_{2Y}\\ MC_{3Y}\\ \end{pmatrix} = \begin{pmatrix} WFS_{1Y}\\ WFS_{2Y}\\ MC_{2Y-TRANS}\\ \end{pmatrix}

*The values in this matrix represent the number of counts/offset count. Thus all ovalues found from the step response were divided by the number of counts on each offset.

To find the new yaw matrix, we then take the inverse of the step response output matrix to get:

\begin{pmatrix} MC_{1Y}\\ MC_{2Y}\\ MC_{3Y}\\ \end{pmatrix} = \begin{pmatrix} 0.188 & -0.009 & 0.403 \\ 0.017 & 0.005 & -0.006 \\ 0.689 & 0.987 & 0.656 \end{pmatrix} \begin{pmatrix} WFS_{1Y}\\ WFS_{2Y}\\ MC_{2Y-TRANS}\\ \end{pmatrix}

The results from the step response may also be seen graphically in attachment 1. The first plot shows all 3 response signals. Then each following plot shows the individual signals and the step responses overlayed for each one.

The plots also include horizontal lines that represent the average for the stepped signals and the average of the signal at rest along with shading for their associated uncertainties.


This was then tested in C1IOO_WFS_BASIS Yaw matrix, and at first did not work well. The WFS1 Yaw output would rail toward the limits. To fix this, the sign of the gain was flipped (from 0.5 to -0.5) which seemed to solve this issue.

This was then transmitted to the matrix to give:

\begin{pmatrix} MC_{1Y}\\ MC_{2Y}\\ MC_{3Y}\\ \end{pmatrix} = \begin{pmatrix} -0.188 & -0.009 & 0.403 \\ - 0.017 & 0.005 & -0.006 \\ -0.689 & 0.987 & 0.656 \end{pmatrix} \begin{pmatrix} WFS_{1Y}\\ WFS_{2Y}\\ MC_{2Y-TRANS}\\ \end{pmatrix}

This did not solve all issues, the overall ouput signals from the WFS filters still seemed to have large fluctuations. I then began adjusting the gains of the WFS1, WFS2 and MC Trans yaw output filters and achieved much steadier signals.

The following table describes the current best gain valuse for our Yaw matrix:

Sensor Gain Value
WFS1 YAW 5.94
WFS2 YAW 6.44

The results from our found matrix and gain changes can be seen on the left of attachement 2 that displays the ouputs on the Error Signal Monitor. The original output yaw matrix signals can be seen on the right hand side. There is work to still be done on adressing these issues, but overall this may be improved by some additional changes in the gains on each channel.

Attachment 1: step_response_080323.pdf
Attachment 2: Screenshot_2023-03-08_18-17-35.png
  17501   Thu Mar 9 14:22:24 2023 AlexUpdateComputer Scripts / ProgramsUpdate to toggleWFSoffsets.py for step response testing

I have pushed changes made to the toggleWFSoffsets.py script to the git.

This file may be found in: "/opt/rtcds/caltech/c1/Git/40m/scripts/MC/WFS/"

The changes made are:

Updated the script to allow for toggling step responses on either optics or sensors (default = optics), chosen by user

The script orignally asked user to make any last changes to the offsets before hitting enter to run without displaying the new changes.

Now the script checks for changes made by the user to the offsets and displays them if detected. If no changes are made, the code starts running the steps.



  17505   Mon Mar 13 15:37:13 2023 AlexUpdateIMCStep Response of newly diagonalizing YAW output matrix

From the work that Anchal has completed for diagnolizing the YAW ouput matrix, a step response was taken of this new matrix using our previous methodolgies and the following results:

The step response can be seen plotted in attachment 1. The off diagonal terms of this new matrix sum to 1.24, which is a large decrease from the current matrix and the matrices that were tested from our previous step responses. 

Tomohiro and I are now currently working futher to configure the UGF's for YAW given this new output matrix.


Tomohiro and I have completed testing the YAW Sensor outputs with broadband noise injection and have confirmed that gains currently set on each filter module (which is 1.0 for WFS1, WFS2, and MC Trans) provides us with adequate UGF's. As seen bellow in attachment 2-3, WFS1 and WFS2 have UGF's between 2 and 3 Hz. MC Trans can be seen in attachment 4 and has been confirmed to have a UGF around 0.1 Hz.

Finally, attachment 5 displays the off diagnolized sums and uncertainties for each of our previous step response results and the newest result (labeled "new") for Anchal's OUTPUT YAW matrix. The first graph in blue displays the overall sum and uncertainty related to each step response taken. Then in the following 3 plots, the sum's and uncertaintes for each sensor are displayed individually for each step response test.

For reference:

New: corresponds to Anchal's YAW OUPUT MATRIX

D0: refers to the previously implemented matrix, prior to any testint or updates

D1: refers to the matrix that was computed based off of the first test Tomohiro and I performed

D2: refers to the matrix computed as a secondary result from D1. This matrix was thought to provide a lower off diagonal sum, but did not.

This thoroughly displays our results such that the newly computed matrix from Anchal is much more diagnolized then that of the step response matrices Tomohiro and I have computed.


Attachment 1: step_response_YAW_130323.pdf
Attachment 2: WFS1_YAW_OLTF_NI.pdf
Attachment 3: WFS2_YAW_OLTF_NI.pdf
Attachment 4: MC2_YAW_OLTF_NI.pdf
Attachment 5: Mar13_Dfactor.pdf
  17507   Tue Mar 14 11:34:05 2023 AlexHowToComputer Scripts / ProgramsSummary Pages Restart

If the summary pages go down, it could be from a break in the script or some small error. The first remedy for fixing this can be to remove the cron jobs in the que and restart the "gw_daily_summary.sub" and "gw_daily_summary_rerun.sub" scripts. 

For more information on how to do this, follow instructions found in the wiki.


  17515   Tue Mar 21 18:41:12 2023 AlexUpdateIMCDither Lines set on MC1, MC2, MC3 for the night

With Anchal's help, I have setup dither lines for Rana on MC1,2,3 that will be running overnight. The oscilations were set on MC1,2,3, oscillator screens.
The following table describes the current setup:

Mirror Frequency Amplitude
MC1 21.12 Hz 2000
MC2 25.52 Hz 1000
MC3 27.27 Hz 2500

These frequencies and amplitudes were set on LOCKIN1 for each MC1,2,3. The output filters matrix for MC1,2,3 was also updated to reflect the degree of freedom being tested: PITCH.

The frequencies were picked to avoid the dewhitening frequency: 28Hz, and the Bounce/Roll frequencies: 16 Hz & 24 Hz. Furthermore, decimal value frequencies were utilized to avoid the multiples of 1 Hz.

The oscilators were originally started at 1363480200 and will be turned off at 1363535157.

See attachment 1 for the plot of the power spectrum. This test is done to find the beam offset for pitch.

Attachment 1: 21032023_Dither_lines_plot
  17516   Wed Mar 22 15:51:44 2023 AlexUpdateIMCBeam offset calculation for MC1,2,3 from dither results

I have organized the resulting data from running dither lines on MC1,2,3. The data has been collected from diaggui as shown in attachment 1.

Mirror f_l Avg Re (+/- 1000) Avg Im (+/- 1000) Peak Power (\delta f) Cts/urad
MC1 21.12 7000 4000 8062 12.66
MC2 25.52 13000 10000 16401 6.83
MC3 27.27 4000 -600 4044 11.03

Next using the following equations we can find \Delta Y:

\Delta L = \Delta Y \cdot \theta_{AC}

Where \Delta L is the change in length in result of the dithering and \Delta Y is the overall change in beam spot position

Delta L can be calculated by:

\Delta L = \frac{\delta f}{v_{laser}} \cdot L_{IMC}

where \delta f is the peak power of the line frequency and is found by taking the square root of the magnitude of the Real and imaginary terms, v_{laser} is frequency the laser light is traveling at (281 THz) and L_{IMC} is the lenght of the IMC (13.5 meters).

\theta_{AC} can then be calculated by:

\theta_{AC} = \theta_{DC}/f_l^2

where  \theta_{AC} is the angle at which the mirror was shaken at a given frequency. We can find \theta_{DC} by converting the amplitude of the frequency that the mirror was shaken at and converting it into radians using the conversion constants found here: 17481.

\theta_{AC} is then shown to be found by this angle diveded by the line frequency.

The final values are calculated and displayed bellow:

Mirror \theta_{DC} \theta_{AC} \Delta L \Delta Y
MC1 157.9 urad 0.35 urad 0.38 nm 1.08 mm
MC2 146.4 urad 0.23 urad 0.78 nm 3.39 mm
MC3 226.7 urad 0.31 urad 0.19 nm 0.61 mm


Attachment 1: 22032023_Dither_lines_demod_MC1_21-12.pdf
22032023_Dither_lines_demod_MC1_21-12.pdf 22032023_Dither_lines_demod_MC1_21-12.pdf
  1947   Tue Aug 25 23:16:09 2009 Alberto, ranaConfigurationComputerselog moved in to the cvs path

In nodus, I moved the elog from /export to /cvs/cds/caltech. So now it is in the cvs path instead of a local directory on nodus.

For a while, I'll leave a copy of the old directory containing the logbook subdirectory where it was. If everything works fine, I'll delete that.

I also updated the reboot instructions in the wiki. some of it also is now in the SVN.

  2887   Thu May 6 17:47:01 2010 Alberto, kiwamu, Jc The 3rd (aka The Drigg)OmnistructureTMIMinutes from the Lab Organization Commitee meeting

Today we met and we finally come up with a lot of cool, clever, brilliant, outstanding ideas to organize the lab.

You can find them on the Wiki page created for the occasion.



  3049   Fri Jun 4 11:32:51 2010 Alberto, kiwamuUpdateIOOMC MMT1 Mirror Tests
[Alberto, Kiwamu]
Last Wednesday, we measured the beam profile after the MC mode matching telescope n.1 (MMT1). We found that the reflected beam had an irregular profile when observed with the beam scan. Fringes also appeared on an IR card.
We thought that such effect could be due to interference of the main reflected beam with the beam reflected by the back surface of the mirror.
To test the hypothesis we checked the transmitted and the reflected beams of a spare optic identical to MMT1. (This was the same optic that got dropped during the cleaning/baking process.)
We tested it on the PSL table, using a 200mW beam coming from the new 2W Innolight  laser. To maximize the separation between the two beams, we tested MMT1 at 45 degrees. The setup we used is shown here:
We looked at the beam reflected by MMT1 about 5 meters from the mirror. At that distance the beam spot had a size of about 1-2cm. it didn't look perfectly round, but it showed no fringes, as it had happened with original MMT1 inside the MC chamber.
At the transmission, the second ghost beam due to the back surface reflection (see picture above) was very week. In order to be able to see it on an IR card, we had to increase the laser pumping current from 1A to about 1.5A.
We are now thinking of a way to measure the relative power between the two. The problem is that they run very close to each other and it's not easy to resolve them with a power meter or a photodiode.
  1193   Thu Dec 18 19:15:54 2008 Alberto, YoichiConfigurationSUSMode Cleaner Cavity Alignment

This morning I found the MC locked to the 10 mode. When I locked it on the 00 mode, it was unstable and eventually it always got locked to the wrong mode.

I looked at the Drift Mon MEDM screen, which shows a reference record for position, pitch and yaw of each mirror, and I found that the MC optics were in a different status. Moving the sliders of the mirrors' actuators, I brought them back to the reference position. Then the lock got engaged and it was stable, although the MC reflection from the photodiode, with the wave front sensors (WFS) off, was about 2V. That's higher than the 0.5V the it could get when we aligned the cavity and the input periscope last time.

With the WFS on, the reflection dropped to 0.3V and, so far, the the cavity has been stably locked.

This evening the mode cleaner was again locking on a higher mode so we tweaked the mirrors' actuators by their sliders on the MEDM screen until we improved the reflection to 0.3V.

Then we went inside and, on the AS table, we centered the beam on the wave front sensors.

Now the mode cleaner is locked, the reflection is less than 0.3V and the transmission about 3V, tha is it is in ideal conditions. We'll see if it holds.
  1195   Fri Dec 19 11:29:16 2008 Alberto, YoichiConfigurationMZMZ Trans PD
Lately, it seems that the matching of the input beam to the Mode Cleaner has changed. Also, it is drifting such that it has become necessary to continuously adjust the MC cavity alignment for it to lock properly.

Looking for causes we stopped on the Mach Zehnder. We found that the monitor channel:

which supposedly reads the voltage from some photodiode measuring the transmitted power from the Mach Zehnder, is totally unreliable and actually not related to any beam at all.

Blocking either the MZ input or output beam does not change the channel's readout. The reflection channel readout responds well, so it seems ok.
  2477   Tue Jan 5 10:26:32 2010 Alberto, SteveOmnistructureEnvironmentAdded new wall cable-racks

we hung two new WALL cable racks. One is on the pillar next to the Sp table, the other is next to the PSL computer rack.

To do that we had to drill holes in the wall since the simple screws weren't strong enough to keep them up.

One of the racks, the yellow, is dedicated to 4-pin lemos and other thick cables.


  2106   Fri Oct 16 16:44:39 2009 Alberto, SanjitUpdateComputerselog restarted

This afternoon the elog crashed. We just restarted it.

  1162   Tue Nov 25 18:38:03 2008 Alberto, RobUpdatePSLMC Periscope Alignment
This morning when I came in I found the MC cleaner unlocked and the autolocker script could not lock it. The reflected beam was quite off and showed in the bottom left corner of the IMCR camera. After turning off the WFS locking, I started slightly changing the alignment of the steering mirrors on the MC periscope, waiting for the LSC servo to lock the cavity. It didn't work. At some point I lost the beam from the IMCR camera and that is how someone might have found it when I left it for about one hour.

When I came back and tried again adjusting the steering mirrors, I noticed that the autolocker was working and was trying to lock the cavity. After just a bit of adjustment, the MC got easily locked.

After that, I spent a couple of hours trying to improve the alignment of the periscope to minimize the reflection and maximize the transmission. I started with a transmission of 0.4 V but, despite all the tweaking (I used the technique of turning both yaw knobs at the same time), I couldn't get more than 1.2 V (and 2.4 V at the reflection) if only the LSC servo was on. Looking at the camera, I moved the beam around to look for a more favorable spot but the MC wouldn't lock with the beam in other places. Maybe I could do better or maybe not because the cavity is not aligned. I'm going to try again tomorrow.
  1166   Tue Dec 2 17:56:56 2008 Alberto, RanaConfigurationPSLMC Alignment
In the attempt to maximize the Mode Cleaner transmission and minimize the reflection from the steering mirrors of the MC periscope, we could not get more ~2 V at the MC Trans PD and ~ 0.5 V at MC REFL_DC. As it turned out from the SUS Drift Monitor, the reason was that the MC optics had been somehow displaced from the optimal position.

After restoring the reference position values for the mirrors and tweaking again the periscope, we got ~3V at the MC TransPD and 0.5V at the reflection.
The beam was then probably clipped at the REFL PD so that we had to adjust the alignment of one of the BS in the transmitted beam path on the AS table.
We also zeroed the WFS PDs, but not before reducing the power from the MZ, for their QPDs not to saturate.

After relocking, the transmission was 3V and the reflection ~0.3V.

The beam isnow centered on the Trans PD and REFL PD and the Mode Cleaner locked. More details on the procedure will follow.
  1883   Mon Aug 10 20:49:13 2009 Alberto, RanaUpdatePSLPMC Mode Matching Lenses Tuning

Rana, Alberto

This afternoon we tried to improve the mode matching of the beam to the PMC. To do that we tuned the positions of the two lenses on the PSL table that come before the PMC.

We moved the first lens back an forth the without noticing any improvement on the PMC transmitted and reflected power. Then we moved the first backwards by about one cm (the order is set according to how the beam propagates). That made the things worse so we moved also the second lens in the same direction so that the distance in between the two didn't change significantly. After that, and some more adjustments on the steering mirrors all we could gain was about 0.2V on the PMC transmission.

We suspect that after the problems with the laser chiller of two months ago, the beam size changed and so the mode matching optics is not adequate anymore.

We have to replace the mode matching lenses with other ones.


  2468   Wed Dec 30 18:01:03 2009 Alberto, RanaUpdateGeneralAll watchdogs tripped this morning


This morning I found all the watchdogs had tripped during the night.

I restored them all.

I can't damp ITMX. I noticed that its driving matrix is all 1s and -1s as the the right values had been lost in some previous burtrestoring.


Rana fixed the problem. He found that the side damping was saturating. He lowered the gain a little for a while, waited for the the damping to slow down the optic and then he brought the gain back where it was.

He also upadted the MEDM screen snapshot.

  3029   Wed Jun 2 01:47:28 2010 Alberto, KiwamuUpdateIOOmode measurement of new input optics

The mode profile of the new input optics was measured.

Although the distance between each optic was not exactly the same as the design because of narrow space,

we measured the profile after the curved mirror (MMT1) that Jenne and Kevin put in the last week.


(interference from MMT1)

Below is a sketch of the current optical path inside of the chamber.



In the beginning of this measurement, the angle between the incident and the reflection on MMT1 (denoted as theta on the sketch) was relatively big (~40deg) although MMT1 was actually made for 0deg incident.

At that time we found a spatially large interference imposed on the Gaussian beam at the beam scan. This is not good for mode measurement

This bad interference can be caused by an extra reflection from the back surface of MMT1 because the interference completely vanished by removing MMT1  .

In order to reduce the interference we decreased the angle theta as small as possible. Actually we made it less than 10deg which was our best due to narrow space. 

Now the interference got less and the spot looks better.

The picture below shows an example of the beam shape taken by using the beam scan.

Top panel represents the horizontal mode and bottom panel represents the vertical mode.

You can see some bumps caused by the interference on the horizontal mode, these bumps may lead to overestimation of the horizontal spot size .






 The above plot shows the result of the mode measurement.

 Here are the parameter obtained by fitting. The data is also attached as attachment:4

waist size for vertical  w0v [mm]  0.509 +/-0.0237
waist size for horizontal

w0h  [mm]

 0.537  +/- 0.0150
waist position from MMT1 for vertical  xv[m]  -2.91 +/- 0.214
waist position from MMT1 for horizontal xh[m]   -2.90 +/-  0.127

Attachment 3: MMT1_.dat.zip
  3046   Thu Jun 3 14:40:28 2010 Alberto, KiwamuUpdateIOOmode measurement of new input optics




For the record, we wanted to check whether the fringes on the beam spot were caused by SM2 (see diagram above). We tried two different mirrors for SM2,

The first was one of the flat, 45 degree ones that were already on the BS table. The last, which is the one currently in place, was inside the plastic box with the clean optics that Jenne left us .

The fringes were present in both cases.

  1261   Fri Jan 30 17:30:31 2009 Alberto, JosephbConfigurationComputersNew computer Ottavia set up
Alberto, Joseph,

Today we installed the computer that some time ago Joe bought for his GigE cameras. It was baptized "OTTAVIA".

Ottavia is black, weighs about 20 lbs and it's all her sister, Allegra (who also pays for bad taste in picking names). She runs an Intel Core 2 Quad and has 4GB of RAM. We expect much from her.

Some typical post-natal operations were necessary.

1) Editing of the user ID
  • By means of the command "./usermod -u 1001 controls" we set the user ID of the user controls to 1001, as it is supposed to be.

2) Connection to the Martian network
  • Ottavia was given IP address by editing the file /etc/sysconfig/networ-scripts/ifcfg-eth0 (we also edited the netmask and the gateway address as in the Wiki)
  • In linux1, which serves as name server, in the directory /var/named/chroot/var/named, we modified both the IP-to-name and name-to-IP register files 131.215.113.in-addr.arpa.zone and 131.215.11in-addr.martian.zone.
  • We set the file /etc/resolv.conf so that the OS knows who is the name server.

3) Mounting of the /cvs/cds path
  • We created locally the empty directories /cvs/cds
  • We edited the files /etc/fstab adding the line "linux1:/home/cds /cvs/cds nfs rw,bg,soft 0 0"
  • We implemented the common variables of the controls environment by sourcing the cshrc.40m: in the file /home/controls/.cshrc we added the two lines "source /cvs/cds/caltech/cshrc.40m" and "setenv PATH ${PATH}:/cvs/cds/caltech/apps/linux64/matlab/bin/"
  2490   Fri Jan 8 20:13:49 2010 Alberto, JoBConfigurationComputersThe 40m Kaiser Permanent Reboot Marathon
This morning after Alex and Jo's tinkering with Megatron the RFM network crashed and it brought down also some computers. The effect was that it was not possible to lock the mode cleaner anymore.
A few computers crashed and things didn't come back to their origianl state.
After an endless day of rebooting and fixing problems with the single front ends (in particular with c1susvme1), eventually the mode cleaner got locked again.
Among my weapons I also used the Nuclear Option (TM).
Maybe I'll include more details in a future elog entry.
Anyway, in the end I burtrestored everything to Jan 8 2009 at 9:00.


  2971   Fri May 21 16:41:38 2010 Alberto, JoUpdateComputersIt's a boy!

Today the new Dell computer for the GSCS (General SURF Computing Side) arrived.

We put it together and hooked it up to a monitor. And guess what? It works!

I'm totally impressed by how the Windows get blurred on Windows 7 when you move them around. Good job Microsoft! Totally worth 5 years of R&D.

  2520   Mon Jan 18 09:44:36 2010 Alberto, BobOmnistructureEnvironmentNo rain water infiltrations so far

It has rained continuously for the last 24 hours. Bob walked through the lab looking for possible water infiltrations. The floor looked dry: no puddles or leaks anywhere so far.

  131   Wed Nov 28 16:18:15 2007 AlbertoMetaphysicsEnvironmentso clean you can eat on it
I tidied up the desks in the lab, brought the Spectrum Analyzers back to the Salumeria (you don't want to know about that), sorted a lot of stuff and boxed up what I didn't know (you can find it in a couple of carton boxes on the table).
The blackmail with the pie might not work next time.
Please, preserve the common sort.

Attachment 1: DSC_0180.JPG
Attachment 2: DSC_0181.JPG
  142   Thu Nov 29 18:10:13 2007 AlbertoHowToComputer Scripts / ProgramsGPIB Scripts
I've spent a lot of time trying to configurate the GPIB-USB interface for the HP4195. After installing 1) the Agilent libraries, 2) the drivers, 3) the matlab Instrument Toolbox, 4) Jamie script, 5) Alice's script the computer can see the HP but still they can't 'talk' to each other.
I give up. I asked Alice Wang how she managed to get data. I'm not sure she used the GPIB interace. Rob said she might have used the old fashion floppy disks that we can't read anymore here.
I would really appreciate any suggestion by anyone who happened to have the same problems.
  246   Thu Jan 17 18:22:14 2008 AlbertoUpdateElectronicsRF Monitor Band-pass Filter
After we finalized the schematic for the RF monitor board based on buffered LC resonators, on Richard Abbott's suggestion to avoid the complication brought in by the fast op-amps, we gave another chance to the a passive configuration of the band-pass filter based on a Chebyshev topology. Rich and Ben gave me an old but very powerful software tool to design that kind of filters and showed me the way to circumvent many hassles in making RF test boards.

I made a test circuit for the 166MHz line (see attached schematic), using tunable inductors. The TF are also attached.
We get more than 20 dB of isolation after 33MHz (with a loss of only few dB at the resonance - it could be less), which is enough for all the other frequencies (33,133,199 MHz) but we would like more for the 166. We are going to add one or two extra orders to the filter.

We also have to understand the spike at about 320Mhz and eventually somehow get rid of it.

Attachment 1: RF166Mhz.png
Attachment 2: Chebyshevb.png
Attachment 3: Chebyshev2b.png
  248   Fri Jan 18 11:53:50 2008 AlbertoUpdateElectronicsRF Monitor Band-pass Filter
The response is asymmetric and on the left side of the peak, we have at least 33dB within 33Mhz, which is enough for all the frequencies. We probably don't need an higher order filter but just low pass filters in series.

The spike at 320MHz doesn't depend on the circuit board. It's either the cables, their connection, or the splitters.

Note that the frequency of this test circuit has still to be tuned exactly at 166MHz (now it's 149).


After we finalized the schematic for the RF monitor board based on buffered LC resonators, on Richard Abbott's suggestion to avoid the complication brought in by the fast op-amps, we gave another chance to the a passive configuration of the band-pass filter based on a Chebyshev topology. Rich and Ben gave me an old but very powerful software tool to design that kind of filters and showed me the way to circumvent many hassles in making RF test boards.

I made a test circuit for the 166MHz line (see attached schematic), using tunable inductors. The TF are also attached.
We get more than 20 dB of isolation after 33MHz (with a loss of only few dB at the resonance - it could be less), which is enough for all the other frequencies (33,133,199 MHz) but we would like more for the 166. We are going to add one or two extra orders to the filter.

We also have to understand the spike at about 320Mhz and eventually somehow get rid of it.

Attachment 1: Chebyshevb.png
  268   Fri Jan 25 15:53:59 2008 AlbertoUpdateElectronics40 dB from the 3rd order Chebyschev
I managed to tune the 7 knobs in the 3rd order Chebyshev bandpass filter obtaining the tranfer function attached to this entry. We have now 40 dB of attenuation between 166 Mhz and 133 and 199. With this tuning the insertion loss is rather high. We need a better one.

Attachment 1: 166MhzElog.png
  285   Wed Jan 30 11:49:30 2008 AlbertoSummaryElectronicsRF monitor's filters final schematics and transfer functions
These are the final schematics for the 6th order Chebyshev filters of the RF monitor board. I'm also attaching the TF as I measured. The tuning is probably not optimal, less insertion noise could be achieved.
Attachment 1: 33Melog30Jan08.png
Attachment 2: 133Melog30Jan08.png
Attachment 3: 166Melog30Jan08.png
Attachment 4: 199Melog30Jan08.png
Attachment 5: 33elog30Jan08.png
Attachment 6: 133elog30Jan08.png
Attachment 7: 166elog30Jan08.png
Attachment 8: 199elog30Jan08.png
  314   Wed Feb 13 11:41:00 2008 AlbertoUpdateElectronicsSome characterization of the RF Monitor Box (StocMon)
I'm attaching a table with some measurements and the power spectrum from the pd to help evaluate the numbers.

The box output ranges from 0.5V to 2.1V. The coefficient between power and voltage is negative so higher voltage means lower power.

The red numbers are the outputs from each channel at their resonant frequencies. As one can see these are not very well centered on the dynamic range of the power detectors.

The cross coupling seems to be not a problem.

Even if the 166 filter, which handles the smallest of the frequencies and is also the most lossy (for construction reason), mounts a preamplifier, the output is still rather small. this explain also the high bias due to the noise amplification at the maximum power (13dB). A better insertion loss either remaking the filter or re-tuning that one would simplify many problems, i.e. there is not much room in the metal pomona box to fit the amplifier. I might want to consider, after everything else is ready and if I have time before leaving next week, to work on a new 166 filter.
Attachment 1: CircuitCharacterization.png
Attachment 2: alberto.spectrum3.png
  321   Mon Feb 18 12:04:39 2008 AlbertoUpdateElectronicsRF Monitor (StocMon)
I put the amplifiers next to the monitor on the PSL table, layed the power and the RF SMA cables out to the rack. I'm powering the box and the amplifiers with the power supply, waiting for someone to show me tomorrow how to connect it to the Sorensen (Steve, Ben?).

I'm ready to hook up the channels into EPICS.
Attachment 1: DSC_0443.JPG
  331   Fri Feb 22 08:29:07 2008 AlbertoUpdateElectronicsRF Monitor (StocMon)

I put the amplifiers next to the monitor on the PSL table, layed the power and the RF SMA cables out to the rack. I'm powering the box and the amplifiers with the power supply, waiting for someone to show me tomorrow how to connect it to the Sorensen (Steve, Ben?).

I'm ready to hook up the channels into EPICS.

Me and Ben Abbot were plugging the cables that power that RF Monitor box into the PSL rack when inadvertently we made some arcs spark between the pins on the back of one of the ADC. Somehow that made the laser shut down although the MOPA stayed on. We also notice some smell of burn.

Later on, after several failed attempts, Rob, Ben and Steve could restart the laser. It took some times because the written procedure to start the chiller is not very precise.
  332   Fri Feb 22 08:33:18 2008 AlbertoUpdateElectronicsRF Monitor (StocMon)

I put the amplifiers next to the monitor on the PSL table, layed the power and the RF SMA cables out to the rack. I'm powering the box and the amplifiers with the power supply, waiting for someone to show me tomorrow how to connect it to the Sorensen (Steve, Ben?).

I'm ready to hook up the channels into EPICS.

With Ben, we hooked up the RF Monitor box into the PSL rack and created 4 EPICS channels for the outputs:


The power cable bringing +15V to the preamplifier on the PSL table should be replaced eventually.
  545   Thu Jun 19 15:52:06 2008 AlbertoConfigurationComputersMeasure of the current absorbed by the new Megatron Computer
Together with Rich Abbot, sam Abbot and I measured the current absorbed by the new Megatron computer that we installed yesterday in the 1Y3 rack. The computer alone absorbs 8.1A at the startup and then goes down to 5.9A at regime. The rest of the rack took 5.2A without the computer so the all rack needs 13.3 at the startup and the 11.1A.

We also measured the current for the 1Y6 rack where an other similar Sun machine has been installed as temporary frame builder and we get 6.5A.

Alberto, Rich and Sam Abbot
  555   Mon Jun 23 21:51:19 2008 AlbertoUpdateGeneralArm Cavity Length Measurement
We measured the arm cavity lengths sweeping the ETM mirror position and looking at the reflected demodulated output. We excited the mirror by a sine wave of 0.2 Hz and amplitude of 30000 counts. From the time series of the occurrences of the resonances of the sidebands and of the carrier we evaluated the free spectral range of the cavities and thus the lengths. The details of the procedure are explained in the attached document. As discussed in it, for each cavity we obtain two possible values of the length depending on which of the sideband resonances is that corresponding to the upper sideband and which corresponds to the lower one instead. The numbers are:
Lx=(38.30 +/- 0.08)m / (38.45 +/- 0.08)m
Ly=(38.16 +/- 0.08)m / (38.70 +/- 0.08)m

Since the difference between the two possibilities is quite large, we should be able to decide which one is correct by somehow measuring directly the cavity length. We want to try it tomorrow by a tape meter.

Alberto and Koji
Attachment 1: 40mLengthMeasure.pdf
40mLengthMeasure.pdf 40mLengthMeasure.pdf
  621   Wed Jul 2 06:46:05 2008 AlbertoConfigurationGeneralNPRO on to warm up
This morning I turned on the NPRO on the AP table so that it can warm up for a few hours before I start using it today.
The flipping mirror is down so no beam is injected in to the IFO.

ELOG V3.1.3-