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  13875   Mon May 21 18:02:55 2018 keerthanaUpdateGeneralTesting of the new mini-circuits frequency counter

Today, I tested the new mini-circuit frequency counter by connecting it with the beat signal output. The frequency counter works fine. Now I am trying to get a display of the frequency in the computer screen using python programming. I have made the code for remotely changing oscilator frequency and it is saved in the folder 'ksnair'. A picture of the new mini circuits frequency counter is attached below. Part no: UFC-6000, S/N: 11501040012, Run: M075270.

Attachment 1: frequency_counter.jpg
  12999   Fri May 19 19:18:53 2017 KaustubhSummaryGeneralTesting of the new Photo Detectors ET-3010 and ET-3040


I got some hands-on-experience on using RF photodetectors and the Network Analyzer from Koji. There were newly purchased RF photodetectors from Electro-Optics Technology, Inc.. These were InGaAs Photodetectors with model no.: 120-10050-0001(ET-3010) and 120-10056-0001(ET-3040). The User Guide for the two detectors can be found here. This is the first time we bought the ET-3010 model PD for the 40m lab. It has an operation bandwith >1.5GHz(not tested yet), much higher than other PDs of its kind. This can be used for detecting the output as we 'sweep' the laser frequency for getting data on the optical cavities and the resonating modes inside the cavity. We just tested out the ET-3040 model today but will test out the ET-3010 next week.

Tools and Machines Used:

We worked on the optical bench right in front of the main entrance to the lab. We put the cables, power chords, etc. to their respective places. We used screws, poles, T's, I's, multimeter, Network/Spectrum Analyzer(along with the moving table), a lab computer, Oscilloscope, power supply and the aforementioned PDs for our testing. We took these items from the stack of tools at the Y-arm and the boxes of various different labelled palced near the X-arm. We moved the Network Analyzer(along with the bench) from near the Y-arm to our workplace.


I will include a rough schematic of the setup later.

We alligned the reference PD(High Speed Photoreceiver model 1611) and the test PD(ET-3040 in this case) to get optimal power output. We had set the pump current for the laser at 19.5mA which produced a power of 1.00mW at the output of the fiber couple. At the reference detector the measured voltage was about 1.8V and at the DUT it was about 15mV. The DC transimpedance for the reference detector is 10kOhm and its responsivity to 1064 nm is around 0.75A/W. Using this we calculate the power at the reference detector to be 0.24mW. The DC transimpedance for the DUT is 50Ohm and the responsivity of about 0.9A/W. This amounts to a power of about 0.33mW. After measuring the DC voltages, we connected the laser input to the Network Analyzer and gave in an RF signal with -10dBm and frequency modulation from 100 kHz to 500 MHz. The RF output from the Analyzer is coupled to the Reference Channel(CHR) of the analyzer via a 20dB directional coupler. The AC output of the reference detector is given at Channel A(CHA) and the output from the DUT is given to Channel B(CHB). We got plots of the ratios between the reference detector, DUT and the coupled refernce for the Transfer Function and the Phase. We found that the cut-off frequency for the ET3040 model was at arounf 55 MHz(stated as >50MHz in the data sheet). We have stored the data using the lab PC in the directory .../scripts/general/netgpibdata/data.


The bandwidth of the ET-3040 PD is as stated in the data sheet, >50 MHz.


These PDs have an internal power supply of 3V for ET-3040 and 6V for ET-3010. Do not leave these connected to any instruments after the experiments have been performed or else the batteries will get drained if there is any photocurrent on the PDs.

To Do:

A similar procedure has to be followed in order to test the ET-3010 PD. I will be doing this tentatively on Monday.

Attachment 1: IMG_20170519_173247922.jpg
Attachment 2: IMG_20170519_173253252.jpg
Attachment 3: IMG_20170519_173300174.jpg
Attachment 4: PD_test_setup.png
  13005   Mon May 22 18:20:27 2017 KaustubhSummaryGeneralTesting of the new Photo Detectors ET-3010 and ET-3040

I am adding the text files with the data readings and paramater settings along with the Bode Plot of the data. I plotted these graphs using matplotlib module with python 2.7.



I got some hands-on-experience on using RF photodetectors and the Network Analyzer from Koji. There were newly purchased RF photodetectors from Electro-Optics Technology, Inc.. These were InGaAs Photodetectors with model no.: 120-10050-0001(ET-3010) and 120-10056-0001(ET-3040). The User Guide for the two detectors can be found here. This is the first time we bought the ET-3010 model PD for the 40m lab. It has an operation bandwith >1.5GHz(not tested yet), much higher than other PDs of its kind. This can be used for detecting the output as we 'sweep' the laser frequency for getting data on the optical cavities and the resonating modes inside the cavity. We just tested out the ET-3040 model today but will test out the ET-3010 next week...


Attachment 1: ET-3040_test.zip
Attachment 2: ET-3040_test.pdf
  15937   Thu Mar 18 09:18:49 2021 Paco, AnchalUpdateSUSTesting of new input matrices with new data

[Paco, Anchal]

Since the new generated matrices were created for the measurement made last time, they are of course going to work well for it. We need to test with new independent data to see if it works in general.

  • We have run scripts/SUS/InMatCal/freeSwingMC.py for 1 repition and free swinging duration of 1050s on tmux session FreeSwingMC on Rossa. Started at GPS: 1300118787.
  • Thu Mar 18 09:24:57 2021 : The script ended successfully. IMC is locked back again. Killing the tmux session.
  • Attached are the results of 1-kick test, time series data and the ASD of DOFs for calculated using existing input matrix and our calculated input matrix.
  • The existing one was already pretty good except for maybe the side DOF which was improved on our diagonalization.


After Anchal left for his test, I took the time to set up the iMAC station so that Stephen (and others) can remote desktop into it to use Omnigraffle. For this, I enabled the remote login and remote management settings under "Sharing" in "System Settings". These two should allow authenticated ssh-ing and remote-desktopping respectively. The password is the same that's currently stored in the secrets.

Quickly tested using my laptop (OS:linux, RDP client = remmina + VNC protocol) and it worked. Hopefully Stephen can get it to work too.

Attachment 1: MC_Optics_Kicked_Time_Series_1.pdf
Attachment 2: TEST_Input_Matrix_Diagonalization.pdf
TEST_Input_Matrix_Diagonalization.pdf TEST_Input_Matrix_Diagonalization.pdf TEST_Input_Matrix_Diagonalization.pdf
  15939   Thu Mar 18 12:46:53 2021 ranaUpdateSUSTesting of new input matrices with new data

Good Enough! Let's move on with output matrix tuning. I will talk to you guys about it privately so that the whole doesn't learn our secret, and highly sought after, actuation balancing.

I suspect that changing the DC alignment of the SUS changes the required input/output matrix (since changes in the magnet position w.r.t. the OSEM head change the sensing cross-coupling and the actuation gain), so we want to make sure wo do all this with the mirror at the correct alignment.


  3596   Thu Sep 23 02:23:04 2010 koji,taraSummaryElectronicsTesting new TTFSS

I tested the new table top frequency stabilization system(TTFSS),
I haven’t finished it yet, and accidentally fried one amplifier in the circuit.

We received three sets of a new TTFSS system which will replace the current FSS.
It needs to be checked that the system works as specified before we can use it.

- Result

I followed the instruction written on E10000405-v1
The first test inspected how much the currents were drawn from the +/- 24 V power supply.
+24 V drew 350 mA and -24 V drew 160 mA as shown on pwr supply’s current monitor.
They exceeded the specified value which was 200 +/- 20 mA, but nothing went wrong during the test.
Nothing got overheated, all voltage outputs were correct so I proceeded.
I have gone down the list to 6, and everything works as specified.

- Correcting the document for the test procedure

I found a few errors on the instruction document. I’ll notify the author tomorrow.

- How GVA-81 amplifier on D0901894 rev A got fried

During the test, I used a mirror on a stick that looked like a dental tool to see under the board.
Unfortunately, the steel edge touched a board and caused a spark. The voltage on -24 dropped to -16.
I think this happened because the pwr supply tried to decrease the current from shorted circuit,
as I shorted it only short time ( a blink of an eye), it could not reduce the voltage to zero.
When I was checking the power supply and about to adjust the voltage back to the right value
(about 4-5 seconds after the spark,) smoke came out of the circuit.

Koji investigated the circuit and found that a GVA 81 amplifier was broken.

This was checked by applying 5V to the amp, and slightly increasing the current.
The voltage dropped to zero as the amp was broken, so its circuit was shorted.

I’ll see if I can replace this at EE lab at Downs.
If I cannot find a spare one, I’ll replace it with a resistor and resume the test procedure.
Because it amplifies LO signal, which won’t be used during the test.

  9009   Tue Aug 13 21:49:32 2013 KojiSummaryGeneralTesting new AG4395A network analyzer

New AG4395, sn MY41101114  for West Bridge Labs was delivered. For the test purpose it is at the 40m now.

I made a series of tests in order to find anything broken.

Network analyzer test

- RF out / Rch test

RF out directly connected to R input channel.
The received power at the R-ch was measured while the output was swept from 10Hz to 500MHz.

The RF power was changed from -50dBm to +15dBm with +10dBm increment (but the last one).

The attenuator setting was changed from 50dB to 0dB.

=> The configured output power was properly detected by the R channel.

=> RF output is producing the signal properly. R-ch is detecting the produced signal properly.

- Ach/Bch test

Same test as above for Ach and Bch 

=> Same result as above

=> A-ch and B-ch are detecting the produced signal properly.

- Transfer function test

Connect a power splitter to the RF out. Detect the split signals by R-ch and A-ch

=> Measurement is at around 0dB +/- 1dB up to 500MHz.

Same measurement for B-ch

=> Same result

=> A/R and B/R indicates proper transfer function measurements.

- Calibration

RF out was split in to two. One was connected to R-ch. The other was connected to A-ch.
The thru response calibration was run.

=> The thru calibration was performed properly. 

- Practical tranfer function measurements.

In the above calibration setup, various RF filters were inserted in the Ach path.

The measured data was extracted via GPIB connection.

=> Practical transfer function measurements were performed.

=> GPIB connectivity was confirmed


External reference test

- External 10MHz reference from an SRS frequency counter was connected to Ext Ref In

=> Ext Ref indicator on the screen appeard

=> The internal oscillator seemed to be locked to the external reference in



Spectrum analyzer test

- Measured the signals from DS345 by R/A/B ch

Sinusoidal signal (1V) swept from 10MHz to 30Mhz

=> Corresponding moving peak was detected in each case

- Noise level measurement

R/A/B channels were terminated. The attenuation at each port was set to 0dB.

Frequency span was changed between 500MHz, 10MHz, 100kHz, 1kHz.

=> Noise level of ~10nV/rtHz between 0.1-500MHz was confirmed. All R/A/B channels have the same performance.

Attachment 1: AG4395A_noise.pdf
  5671   Sat Oct 15 16:42:08 2011 KojiUpdateLSCTesting REFL165

Test results of new REFL165 (the first attachment)

- The resonant freq 166.2MHz, Q=57 (previous Q was ~7)

- If we believe the TF measurement, the transimpedance at the resonance is 7.8k [V/A] and the shotnoise intercept current of ~1mA.
The linearity of the peak was confirmed by changing the modulation level of the beam.

- There is a riddle: the white light test indicates 4.5k [V/A] and 2.8mA for those numbers.
There are big descrepancies from those by the TF measurements.

Further analysis of the descrepancies:

Using the noise measurements with different DC current levels, the transimpedance for each frequency can be reconstructed.

Does this indicate the satiration by the white light???

- The TF measurement shows consistent mag&phase relationship at the resonance (c.f. LISO fit).
So this steep resonance is not an artifact by a noise or glitch but the real structure of the electronics.

- The TF measurement has been done with the photocurrent of ~0.3mA, while the transimpedance measurement
with the white light illumination has the practical effect only when the DC photocurrent is larger than 1mA
because of the circuit noise. Does this higher photo current affected the resonance?

- The off-resonant transimpedance agree with the TF measurement as far as we can see with those measurements.
This may mean that the actual resonant structure has been affected in the white light measurement.
(i.e. not the saturation of the RF opamp which causes the change of the gain at any freq.)
Is the above mentioned higher DC current causing the change of the diode capacitance or other property of the diode or the inductors???

Attachment 1: REFL165_test_111014_KA.pdf
REFL165_test_111014_KA.pdf REFL165_test_111014_KA.pdf REFL165_test_111014_KA.pdf REFL165_test_111014_KA.pdf
Attachment 2: REFL165_transimpedance2.pdf
  5673   Sun Oct 16 02:30:00 2011 ranaUpdateElectronicsTesting REFL165

Unless the bias feedback circuit has been tuned for the 1 mm diode, its possible that you are seeing some C(V) effects. Its easy to check by looking at the phase response at 165 MHz v. the DC photocurrent. Then the feedback or feedforward gain can be tuned.


  13009   Tue May 23 18:09:18 2017 KaustubhConfigurationGeneralTesting ET-3010 PD

In continuation with the previous(ET-3040 PD) test.

The ET-3010 PD requires to be fiber coupled for optimal use. I will try to test this model without the fiber couple tomorrow and see whether it works or not.

  7747   Mon Nov 26 19:27:59 2012 RijuHowTo Testing AG4395A+GPIB

Riju, Jenne

We have checked the transfer function of a bandpass filter using AG4395A network analyzer and retrieved the data through GPIB. The RF out signal of AG4395A had been divided by splitter with two outputs of the splitter going to through R and the filter which was connected to the A channel of the network analyzer. The GPIB data came in complex data format, from which the absolute value and phase had to be retrieved. 


The plot for the TF is as following

Attachment 1: tfmag.jpg
Attachment 2: tfphase.jpg
  7756   Tue Nov 27 19:06:16 2012 RijuUpdate Testing AG4395A+GPIB

 I ve tested another bandpass filter today with similar set-up. This time I took the data with corrected reference level. To set this reference-level the filter was disconnected and the cable was connected "thru" according to the instructions provided in the manual of AG4395A at http://cp.literature.agilent.com/litweb/pdf/04395-90040.pdf, page 3-10. The transfer functions are as follows 

Attachment 1: tfmag1.jpg
Attachment 2: tfphase1.jpg
  7817   Wed Dec 12 17:26:47 2012 RijuUpdate Testing AG4395A+GPIB

I repeated my experiment to get noise level. To get that I disconnected the bandpass filter SBP-10.7  from channel A of network analyzer AG4395A and terminated both the open ends (open end of filter and open end of channel A) with 50ohm terminator.

Reference level had been corrected, signal and noise data had been collected separately w.r.t that level.

Command for GPIB:   ./netgpibdata.py -i -d AG4395A -a 10 -f filename

The result is as follows


Attachment 1: TFbandpassfilter.pdf
  17030   Mon Jul 25 09:05:50 2022 PacoSummaryGeneralTesting 950nm laser found in trash pile

[Paco, Yehonathan]

==== Late elog from Friday ====

Koji provided us with a QFLD-950-3S (QPHOTONICS) salvaged from Aidan's junk pile (LD is alive according to him). We tested the Jenne laser setup with this just to decide if we should order another one, and it worked.

The laser driver anode and cathode pins (8/9, 4/5 respectively) on the rear DB9 port from the  ILX Lightwave LDX-3412 driver were connected to the corresponding anode and cathode pins in the laser package (5, and 9; note the numbers are reversed between driver and laser). Then, interlock pins 1 and 2 in the driver were shorted to enable operation. This is all illustrated in Attachments #1-2.

After setting a limit of 27.6 mA current in the driver, we slowly increased the actual current to ~ 19 mA until we could see light on a beam card. We can go ahead and get a 1060 nm replacement.

Attachment 1: PXL_20220722_234600124.jpg
Attachment 2: PXL_20220722_234551918.jpg
  17064   Fri Aug 5 17:03:31 2022 YehonathanSummaryGeneralTesting 950nm laser found in trash pile

I set out to test the actuation bandwidth of the 950nm laser. I hooked the laser to the output of the bias tee of PD testing setup. I connected the fiber coming out of the laser to the fiber port of 1611 REF PD.

The current source was connected to the DB9 input of the PD testing setup. I turned on the current source and set the current to 20mA. I measured with a fluke ~ 2V at the REF PD DC port.

I connected the AC port of the bias tee to the RF source of the network analyzer and the AC port of the REF PD to the B port of the network analyzer. Attachment 2 shows the setup.

I took a swept sine measurement (attachment) from 100kHz to 500MHz.

It seems like the bandwidth is ~ 1MHz which is weird considering the spec sheet says that the pulse rise time is 0.5ns. To make sure we are not limited by the bandwidth of the cables I looped the source and the input of the network analyzer using the cables used for the previous measurement and observed that the bandwidth is a few 100s of MHz.

Attachment 1: 20220805_164434.jpg
Attachment 2: LaserActuation_TF_Measurement.drawio.pdf
  16042   Fri Apr 16 11:36:36 2021 Anchal, PacoUpdateSUSTested proposed filters for POS colum in MC2 output matrix

We tried two sets of filters on the output matrix POS column in MC2. Both versions failed. Following are some details.

How test was done:

  • PSL shutter was closed and autolocker was switch off.
  • Turned off damping on POS, PIT, and YAW using C1:SUS-MC2_SUSPOS_SW2, C1:SUS-MC2_SUSPIT_SW2, and C1:SUS-MC2_SUSYAW_SW2.
  • Reference data was taken with no excitation to get relative increase at excitation.
  • Frist we sent an excitation through LOCKIN1 at 0.11 Hz and 500 counts amplitude.
  • LOCKIN column in MC2 output matrix was kept identical to POS column, so all ones.
  • This formed our reference data set when no filters were used. Attachment 1.
  • Note that the peak at 0.03 Hz is due to LOCKIN2 that was left switched on due to autolocker.
  • Then the calculated filters were loaded using foton. Procedure:
    • Right click on filter bank med. Got to Execute-> Foton.
    • Go to File and uncheck 'Read Only'.
    • Find the filter module name in Module drop down.
    • Select an empty module section in Sections.
    • Write a name for the filter. We used DCcoupF2A and DCcouF2A2 for the two version respectively.
    • Paste the zpk foton format in Command.
    • Check with Bode plot if these are correct filters. Then click on Save. It will take about 30s to become responsive again.
    • GO back to filter bank medm screen and click on 'Load Coefficients'. This should start displaying your new filter module.
    • To switch on the module, click on the button below its name.
  • Once fitlers were loaded, we realized we can not use the LOCKIn to excite anymore as it comes as separate excitation.
  • So we used awggui to excite C1:SUS-MC2_LSCEXC at 0.11 Hz and 500 counts.
  • Then we retook the data and checked if the peaks are visible on PIT and YAW channels and how high they are.

Filer version 1

  • This was calculated by starting from ideal output matrix elements as they are currently loaded. All 1's for POS and so on.
  • The calculations were done in scripts/SUS/OutMatCalc/coilBalanceDC.py.
  • This file uses a state space model of the suspension and calculated the cross-coupling. Then the cross coupling is inverted and applied to the current output matrix elements to get correction DC gains.
  • These corrected DC gains are then used to create the filters as described in last post.
  • Attachment 2 shows the filter transfer functions and Attachment 3 shows the test results. Failed :(.
  • There was practivally no change in cross coupling that we can see.

Filter version 2:

  • In this version we used the output matrix optimized at high frequencies earlier (16009).
  • While testing this version, we also uploaded this optimised output amtrix at high frequency.
  • In this test, we realized the LOCKIN2 was on and switched it off manually. All excitations were done through awggui.
  • Attachment 4 shows the filter transfer functions and Attachment 5 shows the test results. Failed :(.
  • There was again practivally no change in cross coupling that we can see.

Forgot to upload new MC2 input matrix:

  • In hindsight, we should have uploaded our diagonalized suspension input matrix in MC2.
  • Without it, there was cross-coupling the in the sensor data to begin with.
  • But this can only be part of the reason why all our filters failed miserably.
  • Because the output matrix was not diagonalized earlier but it was not so bad. Onyl a fresh test can tell if it was the culprit.
Attachment 1: 20210416_MC2DCcoilBalancingNoFilters.pdf
Attachment 2: uncFilters.pdf
uncFilters.pdf uncFilters.pdf uncFilters.pdf
Attachment 3: 20210416_MC2DCcoilBalancingWithFilters.pdf
Attachment 4: uncFilters_v2.pdf
uncFilters_v2.pdf uncFilters_v2.pdf uncFilters_v2.pdf
Attachment 5: 20210416_MC2DCcoilBalancingWithFilters_v2.pdf
  16043   Fri Apr 16 15:47:58 2021 ranaUpdateSUSTested proposed filters for POS colum in MC2 output matrix

Looks mostly right, but you used the OSEM sensors as readbacks. We are diagonalizing using the cavity sensors. Using the diagonalized input matrix is also good since that will reduce the cross-coupling due to the damping loops.

Its sort of a subtle issue:

  1. The sensors are are diagonalized into the eigenmode basis, not the Cartesian basis of the mirror motion.
  2. What the cavity cares about is the Cartesian motion.
  3. Q1: in the model, how much Cartesian pitch motion is there at the POS eigenfrequency in the free-swinging case?
  4. Q2: should we somehow diag the input matrix into the Cartesian basis?
  5. Q3: if so, How?
  6. Q4: and why?
  16049   Mon Apr 19 12:18:19 2021 Anchal, PacoUpdateSUSTested proposed filters for POS colum in MC2 output matrix

The filters were somewhat successful, how much we can see in attachment 1. The tip about difference between eigenmode basis and cartesian basis was the main thing that helped us take data properly. We still used OSEM data but rotated the output from POS, PIT, YAW to x, theta, phi (cartesian basis where x is also measured as angle projected by suspension length).

Eigenmode basis and Cartesian basis:

  • It is important to understand the difference between these two and what channels/sensors read what.
  • Eigenmode basis as the name suggests is the natural basis for the suspended pendulum.
    • It signifies the motion along three independent and orthogonal modes of motion: POS (longitudinal pendulum oscillation), PIT, and YAW.
    • The position of optic can be written in eigenmode basis as three numbers:
      • POS: Angle made by the center of mass of optic with verticle line from suspension point.
      • PIT: Angle made by the optic face with the suspension wires (this is important to note).
      • YAW: Angle made by optic surface with the nominal plane of suspension wires. (the yaw angle basically).
  • Cartesian basis is the lab reference frame.
    • Here we define three variables that can also represent an optic positioned and orientation:
      • x: Angle made by the center of mass of optic with verticle line from suspension point. (Same as POS)
      • \large \theta: Angle made by the optic surface with absolute verticle (z-axis) in lab frame.
      • \large \phi: Twist of the optic around the z-axis. Same as YAW angle above.
  • We want to apply the feedback gains and filters in eigenmode basis because they are a set of known independent modes. (RXA: NOOO!!!!!! read me elog entry on this topic)
  • Hence, the output from input matrix of suspensions comes out at POS, PIT and YAW in the eigenmode basis.
  • However, the sensors of optic positional, and orientation such at MC_F, wave front sensors and optical levers measure it in lab frame and thus in cartesian basis.
  • Essentially, the \large \theta measured by these sensors is different from the PIT calculated using the OSEM sensor data and is related by:
    • \large \theta = PIT - POS, where PIT and POS both are in radians as defined above.
  • When we optimized the cross-coupling in output matrix at high frequencies using the MC_F and WFS data, we actually optimized it In cartesian basis.
  • The three feedback filters from POS, PIT and YAW which carry data in the eigenmode basis need to be rotated into the cartesian basis in the output matrix before application to the coils.
  • The so-called F2A and A2L filters are essentially doing this rotation.
  • Above the resonant frequencies, the PIT and \large \theta become identical. Hence we want our filters to go to unity

The two filter sets:

  • The filters are named Eg2Ctv1 and Eg2Ctv2 on the POS column of MC2 output matrix.
  • This is to signify that these filters convert the POS, PIT, and YAW basis data (eigenmode basis data) into the cartesian basis (x, theta, phi) in which the output matrix is already optimized at higher frequencies.
  • v1 filter used an ideal output matrix during the calculation of filter as described in 16042 (script at scripts/SUS/OutMatCalc/coilBalanceDC.py).
  • Attachment 2 shows these filter transfer functions.
  • v2 filter use the output matrix optimized to reduce cross-coupling amount cartesian basis modes (MC_F, WFS_PIT and WFS_YAW) in 16009.
  • Attachment 3 shows these filter transfer funcitons.
  • Because of this, the v2 filter is different among right and left coils as well. We do see in Attachment 1 that this version of filter helps in reducing POS->YAW coupling too.

Test procedure:

  • We uploaded both the diagonalized input matrix and the diagonalized output matrix as calculated earlier.
  • We measured channels C1:SUS-MC2_SUSPOS_IN1_DQ, C1:SUS-MC2_SUSPIT_IN1_DQ, and C1:SUS-MC2_SUSYAW_IN1_DQ throughout this test.
  • These channels give output in an eigenmode basis (POS, PIT, and YAW) and the rows of the input matrix have some arbitrary normalization.
  • We normalize these channels to have same input matrix normalization as would be for ideal matrix (2 in each row).
  • Then, assuming the UL_SENS, UR_SENS, LR_SENS, and LL_SENS channels that come at input of the input matrix are calibrated in units of um, we calculate the cartesian angles x, theta, phi. for this calculation, we used the distance between coils as 49.4 mm (got it from Koji) and length of suspension as 0.2489 m and offset of suspension points from COM, b = 0.9 mm.
  • Now that we have true measures of angles in cartesian basis, we can use them to understand the effect on cross coupling from the filters we used.
  • PSL shutter is closed and autolocker is disabled. During all data measurements, we switched of suspension damping loops. This would ensure that our low frequency excitation survives for measurement at the measurement channels.
  • We first took reference data with no excitation and no filters for getting a baseline on each channel (dotted curves in Attachment 1).
  • We then send excitation of 0.03 Hz with 500 counts amplitude at C1:SUS-MC2_LSC_EXC and switched on LSC output.
  • One set of data is taken with no filters active (dashed curve in attachment 1).
  • Then two sets of data are taken with the two filters. Each data set was of 500s in length.
  • Welch function is used to take the PSD of data with bin widht of  0.01Hz and 9 averages.


  • Filter v1 was the most successful in reducing \large x \rightarrow \theta coupling by factor of 17.5.
    • The reduction in \large x \rightarrow \phi coupling was less. By a factor of 1.4.
  • Filter v2 was worse but still did a reduction of \large x \rightarrow \theta coupling by factor of 7.8.
    • The reduction in \large x \rightarrow \phi coupling was better. By a factor of 3.3.

Next, filters in PIT columns too

  • We do have filters calculated for PIT as well.
  • Now that we know how to test these properly, we can test them tomorrow fairly quickly.
  • For the YAW column though, the filters would probably just undo the output matrix optimization as they are derived from ideal transfer function models and ideally there is no coupling between YAW and other DOFs. So maybe, we should skip putting these on.
Attachment 1: CrossCoupleTestForEgToCtFilters.pdf
Attachment 2: uncFilters.pdf
uncFilters.pdf uncFilters.pdf uncFilters.pdf
Attachment 3: uncFilters_v2.pdf
uncFilters_v2.pdf uncFilters_v2.pdf uncFilters_v2.pdf
  1892   Wed Aug 12 13:35:03 2009 josephb, AlexConfigurationComputersTested old Framebuilder 1.5 TB raid array on Linux1

Yesterday, Alex attached the old frame builder 1.5 TB raid array to linux1, and tested to make sure it would work on linux1.

This morning he tried to start a copy of the current /cvs/cds structure, however realized at the rate it was going it would take it roughly 5 hours, so he stopped.

Currently, it is planned to perform this copy on this coming Friday morning.

  15930   Wed Mar 17 11:57:54 2021 Paco, AnchalUpdateSUSTested New Input Matrix for MC1

[Paco, Anchal]

Paco accidentally clicked on C1:SUS-MC1_UL_TO_COIL_SW_1_1 (MC1 POS to UL Coil Switch) and clicked it back on. We didn't see any loss of lock or anything significant on the large monitor on left.

Testing the new calculated input matrix

  • Switched off the PSL shutter (C1:PSL-PSL_ShutterRqst)
  • Switched off IMC autolocker (C1:IOO-MC_LOCK_ENABLE)
  • Uploaded the same input matrix as the current one to check writing function in scripts/SUS/InMatCalc/testingInMat.py . We have created backup text file for current settings in backupMC1InMat.txt .
  • Uploaded the new input matrix in normalized form. To normalize, we first made each row vector unit vector and then multiplied by the norm of current input matrix's row vectors (see scripts/SUS/InMatCalc/normalizeNewInputMat.py)
  • Switched ON the PSL shutter (C1:PSL-PSL_ShutterRqst)
  • Switched ON IMC autolocker (C1:IOO-MC_LOCK_ENABLE)
  • Locked was caught immediately. The wavefront sensor of MC1 shows usual movement, nothing crazy.
  • So the new input matrix is digestable by the system, but what's the efficacy of it?

< Two inspection people taking pictures of ceiling and portable AC unit passed. They rang the doorbell but someone else let them in. They walked out the back door.>

Testing how good the input matrix for MC1 is:


  • We loaded the input matrix butterfly row in C1:SUS-MC1_LOCKIN_INMATRX_1_4 to 8. This matrix is multiplied by C1:SUS-MC1_UL_SEN_IN and so on channels before the calibration to um and application of toher filters.
  • We tried to look around on how to load the same filter banks on the signal chain of LOCKIN1 of MC1 but couldn't, so we just manually added gain value of 0.09 in this chain to simulate the calibration factor at the very least.
  • We started the oscillator on LOCKIN 1 on MC1 with amplitude 1 and frequency 6 Hz.
  • We added butterfly mode actuation output column (UL:1, UR:-1, LL:-1, LR:1), nothing happened to the lock of probably because of low amplitude we put in.
  • Now, we plot the ASD of channels like C1:SUS-MC1_SUSPOS_IN1 (for POS, PIT, YAW, SIDE) to see if we see a corresponding peak there. No we don't. See attachment 1.

Restoring the system:

  • Added 0 to the LOCKIN1 column in MC1 output matrix.
  • Made LOCK1 oscillator 0 Amplitude, 0 Hz.
  • Changed back gain on signal chain of LOCKIN1 on MC1.
  • Added 0 to C1:SUS-MC1_LOCKIN_INMATRX_1_4 to 8.
  • Switched off the PSL shutter (C1:PSL-PSL_ShutterRqst)
  • Switched off IMC autolocker (C1:IOO-MC_LOCK_ENABLE)
  • Wrote back the old matrix by scripts/SUS/InMatCalc/testingInMat3.py which used the backup we created.
  • Switched ON the PSL shutter (C1:PSL-PSL_ShutterRqst)
  • Switched ON IMC autolocker (C1:IOO-MC_LOCK_ENABLE)
Attachment 1: 20210317_MC1_InMATtest.pdf
Attachment 2: MC1_Input_Matrix_Test.tar.gz
  16541   Tue Jan 4 18:26:59 2022 AnchalUpdateBHDTested 2" PR2 candidates transmission

I used the rejected light from the PBS after the motorized half-wave plate between PMC and IMC injection path (used for input power control to IMC) to measure the transmission of PR2 candidates. These candidates were picked from QIL (QIL/2696). Unfortunately, I don't think either of these mirrors can be used for PR2.

  Polarization Incident Power [mW] Transmitted Power [mW] Transmission [ppm]
V2-2239 & V2-2242 s-pol 940 0.015 16.0
V2-2239 & V2-2242 p-pol 935 0.015 16.0
V6-704 & V6-705 p-pol 925 21 22703

If I remember correctly, we are looking for a 2" flat mirror with a transmission of the order of 1000 ppm. The current PR2 is supposed to have less than 100 ppm transmission which would not leave enough light for LO path.

I've kept the transmission testing setup intact on the PSL table, I'll test existing PR2 and another optic (which is 0.5" thick unfortunately) tomorrow.

  16543   Wed Jan 5 17:46:04 2022 AnchalUpdateBHDTested 2" PR2 candidates transmission

I tested 2 more optics today, the old PR2 that we took out and another optic I found in QIL. Both these optics are also not good for our purpose.


Polarization Incident Power [mW] Transmitted Power [mW] Transmission [ppm]
Existing PR2 p-pol 910 0.004 4.4
V2-1698 & V2-1700 p-pol 910 595 653846

I'll find thw Y1S optic and test that too. We should start looking for alternate solutions as well.


  16566   Mon Jan 10 18:20:45 2022 AnchalUpdateBHDTested 2" PR2 candidates transmission

I tested 2 more optics found by Paco and Yehonathan in QIL.

  Polarization Incident Power [mW] Transmitted Power [mW] Transmission [ppm]
V6-704 V6-706 p-pol 850 17.1 20118
Yellow cylindrical box p-pol 850 <1 ( could not even see it to measure it with a more sensitive power meter) <1000

I would like someone to redo the second test. I'm not sure what was happening but I could not find the transmitted beam at all on my card even with all lights out. This is either too good a coating and not useful for us or I did something wrong while measuring it.

V6-704, V6-706 mirror seemed like a good candidate as the paper with it said it would be a 200 ppm mirror. But I measured a lot more transmission than that. Now that I see that paper more carefully, it is a 45 degree s-pol mirror, probably that's why it had so much transmission for p-pol at near-normal incidence.


  4163   Mon Jan 17 15:31:50 2011 josephbUpdateCamerasTest the Basler acA640-100gm camera

The Basler acA640-100gm is a power over ethernet camera.  It uses a power injector to supply power over an ethernet cable to the camera.  Once I got past some initial IP difficulties, the camera worked fine out of the box.

You need to set some environment variables first, so the code knows where its libraries are located.

setenv PYLON_ROOT /opt/pylon
setenv GENICAM_ROOT_V1_1 /opt/pylon
setenv GENICAM_CACHE /cvs/cds/caltech/users/josephb/xml_cache
setenv LD_LIBRARY_PATH /opt/pylon/lib64:$LD_LIBRARY_PATH

I then run the /opt/pylon/bin/PylonViewerApp

Notes on IP:

Initially, you need to set the computer connecting to the camera to an ip in the 169.254.0.XXX range.  I used on megatron's eth1 ethernet connection.  I also set mtu to 9000.

You can then run the IpConfigurator in /opt/pylon/bin/ to change the camera IP as needed.

Attachment 1: PylonViewer.jpg
  10212   Wed Jul 16 01:46:41 2014 NichinUpdateElectronicsTest run of PDFR system

A test run was conducted on the PDFR system last afternoon and transimpedance plots were generated for 6 of the PDs. The laser was shut down after the test run.

I have not verified (yet) if the transimpedance values indicated by the plots are correct or not. The values mostly look INCORRECT. But the peaks are exactly where they need to be. *phew!*

Reasons: Incorrect calibration, Light other than from the PDFR system fibers on the PDs

Will have to work on debugging all this.

Attachment 1: PDFR_testRun_15-07-2014.pdf
PDFR_testRun_15-07-2014.pdf PDFR_testRun_15-07-2014.pdf PDFR_testRun_15-07-2014.pdf PDFR_testRun_15-07-2014.pdf PDFR_testRun_15-07-2014.pdf PDFR_testRun_15-07-2014.pdf
  10214   Wed Jul 16 02:22:10 2014 KojiUpdateElectronicsTest run of PDFR system

Log-log ... 

  8797   Wed Jul 3 14:33:46 2013 KojiSummaryLSCTest result for the REFL165 photodetector

P.1 Circuit diagram

Added components are indicated by red symbols.

- The diode on the board is HAMAMATSU S3399. It is a Si PIN diode with φ3.0 mm.

- Based on prototype version of aLIGO BBPD D1002969-v8 (although the board says v7, It is v8.)

- The input impedance of the MAR-6SM amplifier (50Ohm) provides the transimpedance.

- The first notch (Lres and Cresa/b) is actually not notch but a LF rejection with DC block.

- The second and third notches are tuned to 11MHz and 55MHz.

- Another notch is implemented between the RF amps. The 33MHz signal is weak so I expected
to have no saturation at the first amplifier.

- As you see from the DC path, the transimpedance of the DC path is 2k V/A. If this is too high,
  we need to replace R9 and R11 at the same time. TP1 is providing +10V such that the total
  reverse bias becomes 25V without bringing a special power supply.

P.2 Transimpedance

The transimpedance is measured with an amplitude modulated diode laser.

The transimpedance is 1k V/A ish. It is already at the edge of the bandwidth.
If we need more transimpedance at 165MHz, we should replace
the PD with FFD-100 (I have one) and apply 100V of reverse bias.

P.3 Current noise spectrum

The measured dark noise voltage spectrum was converted to the equivalent current noise at the diode.

The measured transimpedance is ~1.2kV/A.
The reduction of the transimpedance above 100MHz has been seen as 165MHz is already at the edge of the bandwidth.
If we need more transimpedance at 165MHz, we should replace the diode with FFD-100 (I have one) and apply 100V of reverse bias.

P.4 Shot-noise intercept current

Shot-noise intercept current was measured with a white light from a light bulb.
This measurement suggests the shot-noise intercept current of 1mA, and transimpedance of 1.5kV/A.

Attachment 1: REFL165_response_130702.pdf
REFL165_response_130702.pdf REFL165_response_130702.pdf REFL165_response_130702.pdf REFL165_response_130702.pdf
  1204   Wed Dec 24 12:46:54 2008 YoichiUpdateComputersTest points are back
Rob told me how to restart the test point manager.
It runs on fb40m and actually there is an instruction on how to do that in the Wiki.

I couldn't find the page because when I put a keyword in the search box on the upper right
corner of the Wiki page and hit "enter", it only searches for titles. To do a full text
search, you have to click on the "Text" button.

Anyway, now the test points are back.
  3906   Fri Nov 12 10:49:34 2010 josephb, valeraUpdateCDSTest of ADC noise


Look at the effects of the ADC voltage range on the ADC noise floor.

ADC input was terminated with 50 ohms.  We then looked at the channel with DTT. This was at +/- 10 V range.  We used C1:SUS-PRM_SDSEN_IN1 as the test channel.

The map.c file (in /opt/rtcds/caltech/c1/core/advLigoRTS/src/fe/ ) then had two lines added at line 766.

//JCB temporary 2.5V test, remove me
  adcPtr[devNum]->BCR &= 0x84240;

This hard coded the 2.5 V range (we default to the 10 V range at the moment).

We then rebuilt the c1x02 model and reran the test.

Finally, we reverted the code change to map.c and rebuilt c1x02.

I've attached the DTT output of the two tests.

It appears the ADC is limited by 1.6 uV/rtHz.  Hence the increase in noise in counts by a factor of 4 when we drop to +/- 2.5 V from +/- 10 V.

Attachment 1: ADC_noise.pdf
  3910   Fri Nov 12 19:24:56 2010 KojiUpdateCDSTest of ADC noise

[Koji Yuta]

We found one of the ADC cables were left unconnected. This left the MC suspensions uncontrollable through the whole afternoon.
Please keep the status updated and don't forget to revert the configuration...



Look at the effects of the ADC voltage range on the ADC noise floor.

ADC input was terminated with 50 ohms.  We then looked at the channel with DTT. This was at +/- 10 V range.  We used C1:SUS-PRM_SDSEN_IN1 as the test channel.

The map.c file (in /opt/rtcds/caltech/c1/core/advLigoRTS/src/fe/ ) then had two lines added at line 766.

//JCB temporary 2.5V test, remove me
  adcPtr[devNum]->BCR &= 0x84240;

This hard coded the 2.5 V range (we default to the 10 V range at the moment).

We then rebuilt the c1x02 model and reran the test.

Finally, we reverted the code change to map.c and rebuilt c1x02.

I've attached the DTT output of the two tests.

It appears the ADC is limited by 1.6 uV/rtHz.  Hence the increase in noise in counts by a factor of 4 when we drop to +/- 2.5 V from +/- 10 V.


  3915   Sun Nov 14 11:56:59 2010 valeraUpdateCDSTest of ADC noise


We missed a factor of 2 in the ADC calibration: the differential 16 bit ADC with +/-10 V input has 20 V per 32768 counts (1 bit is for the sign). I confirmed this calibration by directly measuring ADC counts per V.

So the ADC input voltage noise with +/-10V range around 100 Hz is 6.5e-3 cts/rtHz x 20V/32768cts =  4.0 uV/rtHz. Bummer. 

The ADC quantization noise limit is 1/sqrt(12 fs/2)=1.6e-3 cts/rtHz. Where the ADC internal sampling frequency is fs=64 kHz. If this would be the limiting digitization noise source then the equivalent ADC input voltage noise would be 1 uV/rtHz with +/-10 V range.

  14798   Mon Jul 22 13:32:55 2019 KruthiUpdateSUSTest mass pitch adjustment test

[Kruthi, Milind]

On Friday, Milind and I performed the pitch adjustment test Rana had asked us to do. Only 1 blue beam in case of ITMX and two in case of ETMY, ETMX and ITMY were accessible. Milind (of mass 72 kg as of 10 May 2019) stood on each of the accessible blue beams of the test mass chambers for one minute and I recorded the corresponding gps time. Before moving to the next beam, we spared more than a minute for relaxation after the standing end time. Following are the recorded gps times. 







Beam 1

Beam 2

Beam 1

Beam 1

Beam 2

Beam 1

Beam 2

Standing start time (gps)








Standing end time (gps)








PS: For each blue beam relaxation time ~ 1 min after the standing end time

Attachment 1: ETMX.pdf
Attachment 2: itmx.pdf
Attachment 3: ETMY.pdf
Attachment 4: ITMY.pdf
Attachment 5: 3f1a82f2-b86a-469e-8914-9278a216c5f9.jpg
Attachment 6: 1d174307-d940-42e6-812b-83417d0f5f6a.jpg
  15542   Wed Aug 26 16:12:25 2020 gautamUpdateElectronicsTest mass coil current requirements

Attachment #1 is a summary of the current to each coil on the suspensions. The situation is actually a little worse than I remembered - several coils are currently drawing in excess of 10mA. However, most of this is due to a YAW correction, which can be fixed somewhat more easily than a PIT correction. So I think the circuit with a gain of 31 for an input range of +/-10 V, which gives us the ability to drive ~12mA per coil through a 25kohm series resistor, will still provide sufficient actuation range. As far as the HV supplies go, we will want something that can do +/- 350 V. Then the current to the coils will at most be ~50 mA per optic. The feedback path will require roughly the same current. The quiescent draw of each PA95 is ~10mA. So per SOS suspension, we will need ~150mA.

If it turns out that we need to get more current through the 25kohm series resistance, we may have to raise the voltage gain of the circuit. Reducing the series resistance isn't a good option as the whole point of the circuit is to be limited by the Johnson noise of the series resistance. Looking at these numbers, the only suspension on which we would be able to plug in a HV coil driver as is (without a vent to correct for YAW misalignment) is ITMY.

Update 2 Sep 2020 2100: I confirmed today that the number reported in the EPICS channel, and the voltage across the series resistor, do indeed match up. The test was done on the MC3 coil driver as it was exposed and I didn't need to disable any suspensions. I used a Fluke DMM to measure the voltage across the resistor. So there is no sneaky factor of 2 as far as the Acromag DACs are concerned (unlike the General Standards DAC).

Attachment 1: coilCurrents.png
  13265   Tue Aug 29 01:52:22 2017 gautamUpdateSUSTest mass actuator calibration

[ericq, gautam]

Tonight, we decided to double-check the POX counts-to-meters conversion.

It is unclear when this was last done, and since I modified the coil driver electronics for the ITMs and BS recently, I figured it would be useful to get this calibration done. The primary motivation was to see if we could resolve the discrepancy between the current ALS noise (using POX as a sensor) compared to the Izumi et. al. plot.

Because we are planning to change the coil driver electronics further soon anyways, we decided to do the calibration at a single frequency for tonight. For future reference, the extension of this method to calibrate the actuator over a wider range of frequencies is here. The procedure followed, and the relevant numbers from tonight, are as follows.


  1. Set dark offsets on all DCPDs and LSC PDs.
  2. Look at the free swinging Michelson signal on ASDC.
    • For tonights test, ASDC was derived from the AS55 photodiode.
    • The AS110 photodiode actually has more light on it, but we think that the ADC that the DCPD board is interfaced to is running on 0-2V rather than 0-10V, as the signal seemed to saturate around 2000 counts. It is unclear whether the actual photodiode is saturating, to be investigated.
    • So we decided to use ASDC from AS55 photodiode with 15dB whitening gain.
    • There is also some issue with the whitening filter (not whitening gain) on ASDC - engaging the whitening shifts the DC offset. This has to be investigated while we get stuck into the LSC electronics.
  3. Look at the peak-to-peak swing of ASDC. Use algebraic expression for reflected power from Michelson interferometer to calibrate the ASDC slope at Michelson half-fringe. For the test tonight, ASDC_max = 1026 counts, ASDC_min = 2 counts.
  4. Lock the Michelson at half-fringe, with ASDC as the error signal.
    • Zero out the MICH elements in the RFPD input matrix.
    • Set the matrix element from ASDC to MICH in the DCPD LSC input matrix to 1.
    • The servo gain used was +0.005 on the MICH_A servo path.
    • A low-frequency boost was turned on.
  5. Use the sensing matrix infrastructure to drive a line in the optic of interest.
    • Tonight, we looked at ITMX and ITMY.
    • The line was driven at 311.1Hz, and the amplitude was 300 counts.
    • Download 60secs of ASDC data, demodulate at the driven frequency to find the peak height in counts, and using the slope of ASDC (in cts/m) at the Michelson half-fringe, calculate the actuator gain in m/cts.
    • ITMY: 2.55e-9 / f^2 m/count
    • ITMX: 2.65e-9 / f^2 m/count
    • These numbers kind of make sense - the previous numbers were ~5nm/f^2 /ct, but I removed an analog gain of x3 in this path. Presumably there has been some change in the N/A conversion factor - perhaps because of a change in the interaction between the optics' face magnets and the static magnetic field in the OSEMs?
  6. Lock the arms with POX/POY, and drive the newly calibrated ITMs.
    • So we know how many meters we are driving the ITMs by.
    • Looking at POX/POY, we can calibrate these into meters/count.
    • Both POX and POY were whitened.
    • POX whitening gain = +30dB, POY whitening gain = +18dB.
    • ITMX and ITMY were driven at 311.1Hz, with amplitude = 2counts.
    • Download 60 secs of data, demodulate at the drive frequency to find the peak height, and use the known ITM actuator gains to calibrate POX and POY.
    • POX: 7.34e-13 m / count (approx. 5 times less than the number in the Foton filter bank in the C1:CAL-CINV model).
    • POY: 1.325e-13 m / count
    • We did not optimize the demod phases for POX/POY tonight. 

Once these calibrations were updated, we decided to control the arms with ALS, and look at the POX spectrum. Y-arm ALS wasn't so stellar tonight, especially at low frequencies. I can see the GTRY spot moving on the CCD monitor, so something is wonky. To be investigated. But the X arm ALS noise looked pretty good.

Seems like updating the calibration did the job; see the attached comparison plot.

Attachment 1: ALS_comparison.pdf
  2228   Tue Nov 10 17:49:20 2009 AlbertoMetaphysicsComputersTest Point Number Mapping

I found this interesting entry by Rana in the old (deprecated) elog : here

I wonder if Rolf has ever written the mentioned GUI that explained the rationale behind the test point number mapping.

I'm just trying to add the StochMon calibrated channels to the frames. Now I remember why I kept forgetting of doing it...

  2231   Tue Nov 10 21:46:31 2009 ranaSummaryComputersTest Point Number Mapping


I found this interesting entry by Rana in the old (deprecated) elog : here

I wonder if Rolf has ever written the mentioned GUI that explained the rationale behind the test point number mapping.

I'm just trying to add the StochMon calibrated channels to the frames. Now I remember why I kept forgetting of doing it...

 As far as I know, the EPICS channels have nothing to do with test points.

  10886   Mon Jan 12 18:11:25 2015 ericqUpdateASCTest Mass -> Transmon QPD TFs measured

We want to have some angular control of the arms during lock acquistion. 

In single arm lock, Diego and I shook the TMs and measured how the QPDs responded. (I would've liked to do a swept sine in DTT, but the user envelope function still isnt' working!)

For now, we can close simple loops with QPD sensor and ITM actuator, but, as Rana pointed out to Diego and me today, this will drive some amount of the angular cavity degree of freedom that the QPD doesn't sense. So, ideally, we want to come up with the right combination of ITM and ETM motion that lies entirely within the DoF that the QPD senses.

I created a rudimentary loop for Yarm yaw, was able to get ~20Hz for the upper UGF, a few mHz for the lower, but it was starting to leak into the length error signal. Further tweaking will be neccesary...

Attachment 1: Jan12_singleArmSensing.pdf
Attachment 2: Jan12_singleArmSensing.xml.zip
  2232   Wed Nov 11 00:55:47 2009 JenneUpdateAdaptive FilteringTerms put on some ADC inputs

Mostly a note to self:  I have put terminators on the ADC inputs which are usually the PEM-SEIS-GUR2_(XYZ) channels.  Since these 3 signals are currently going into the ASS ADC, these PEM ADC inputs are open, and have predefined channel names.  I'll collect the data and put it as the ADC noise level in my nifty plot which will show the noise limits of all things which affect Wiener Filtering.

  3139   Tue Jun 29 20:47:19 2010 JenneUpdatePEMTerminator put on Guralp Box

A little D-sub terminator was put on the Gur1 input to the Guralp box, to check again the noise level of the box.

  16571   Tue Jan 11 10:58:58 2022 TegaUpdateSUSTemporary watchdog

Started working on this. First created a git repo for tracking https://git.ligo.org/40m/susaux.git

I have looked through the folder to see what needs doing and I think I know what needs to be done for the final case by just following the same pattern for the other optics, which I am listing below

- Create database file for the BHD optics, say C1_SUS-AUX_LO1.db by copying another optic database file say C1_SUS-AUX_SRM. Then replace the optic name.

- Insert a new line "C1:SUS-LO1_LATCH_OFF" in the file autoBurt_watchdogs.req

- Populate the file autoBurt.req with the appropriate channels for LO1

- Populate the file C1SUSaux_post.sh with the corresponding commands for LO1

- Add the line dbLoadDatabase("/cvs/cds/caltech/target/c1susaux/C1_SUS-AUX_LO1.db") to the file C1SUSaux.cmd


For the temporary watchdog, we comment everything I have just talked about, and do only what come next.

My question is the following:

I understand that we need to use the OUT16 slow channel as a temporary watchdog since we don't currently have access to the slow channels bcos the Acromag units have not been installed. My guess from Koji's instructions is that we need to update the channels in the last two fields "INPA" and "INPB" below

        field(DESC,"ANDs Enable with Watchdog")
        field(SCAN,"1 second")
        field(INPA,"C1:SUS-LO1_UL_COMM  PP  NMS")
        field(INPB,"C1:SUS-LO1_LATCH_OFF  PP  MS")

Suppose we replace the channel for INPA with C1:SUS-LO1_ULCOIL_OUT16, what about INPB. Is this even the right thing to do as I am just guessing here?


  16573   Tue Jan 11 13:43:14 2022 KojiUpdateSUSTemporary watchdog

I don't remember the syntax of the db file, but here this calc channel computes A&B. And A&B corresponds to INPA and INPB.

        field(INPA,"C1:SUS-LO1_UL_COMM  PP  NMS")
        field(INPB,"C1:SUS-LO1_LATCH_OFF  PP  MS")

What is this LATCH doing?


  16600   Wed Jan 19 21:39:22 2022 TegaUpdateSUSTemporary watchdog

After some work on the reference database file, we now have a template for temporary watchdog implementation for LO1 located here "/cvs/cds/caltech/target/c1susaux/C1_SUS-AUX_LO1.db".

Basically, what I have done is swap the EPICS asyn analog input readout for the COIL and OSEM to accessible medm channels, then write out watchdog enable/disable to coil filter SW2 switch. Everything else in the file remains the same. I am worried about some of the conversions but the only way to know more is to see the output on the medm screen.

To test, I restarted c1su2 but this did not make the LO1 database available, so I am guessing that we also need to restart the c1sus, which can be done tomorrow.

  16601   Thu Jan 20 00:26:50 2022 KojiUpdateSUSTemporary watchdog

As the new db is made for c1susaux, 1) it needs to be configured to be read by c1susaux 2) it requires restarting c1susaux 3) it needs to be recorded by FB 4) and restartinbg FB.
(^-Maybe not super exact procedure but conceptually like this)



  16606   Thu Jan 20 17:21:21 2022 TegaUpdateSUSTemporary watchdog

Temp software watchdog now operational for LO1 and the remaining optics!

Koji helped me understand how to write to switches and we tried for a while to only turnoff the output switch of the filters instead of the writing a zero that resets everything in the filter.

Eventually, I was able to move this effort foward by realising that I can pass the control trigger along multiple records using the forwarding option 'FLNK'. When I added this field to the trigger block, record(dfanout,"C1:SUS-LO1_PUSH_ALL"), and subsequent calculation blocks, record(calcout,"C1:SUS-LO1_COILSWa") to record(calcout,"C1:SUS-LO1_COILSWd"), everything started working right.


After some work on the reference database file, we now have a template for temporary watchdog implementation for LO1 located here "/cvs/cds/caltech/target/c1susaux/C1_SUS-AUX_LO1.db".

Basically, what I have done is swap the EPICS asyn analog input readout for the COIL and OSEM to accessible medm channels, then write out watchdog enable/disable to coil filter SW2 switch. Everything else in the file remains the same. I am worried about some of the conversions but the only way to know more is to see the output on the medm screen.

To test, I restarted c1su2 but this did not make the LO1 database available, so I am guessing that we also need to restart the c1sus, which can be done tomorrow.


  15402   Tue Jun 16 13:35:03 2020 JonUpdateVACTemporary vac fix / IFO usable again

[Jon, Jordan, Koji]

Today Jordan reconfigured the vac system to allow pumping of the main volume resume, with Jon and Koji remotely advising. All clear to resume normal IFO activities. However, the vac system is operating in a temporary configuration that will have to be reverted as we locate replacement components. Details below.


Since serial readback of the TP2 controller seems to be failing, we reconfigured the system with TP3 now backing for TP1. TP2 was valved off (at V4) and shut down until we can replace its controller.

TP3 has its own problems, however. It was valved off in January after its temperature readback began glitching and spuriously triggering the interlocks [ELOG 15140]. However the problem appears to be limited only one readback (rotation speed, current, voltage are fine) and there is enough redundancy in the pump-dependent interlock conditions to safely connect it to the main volume.

We also discovered that sometime since January, the TP3 dry pump has failed. The foreline pressure had risen to 165 torr. Since the TP2 and TP3 dry pumps are not interchangeable (Agilent vs. Varian), we instead valved in the auxiliary dry pump and disconnected the failed dry pump using a KF blank. This is a temporary arrangement until the permanent dry pump can be repaired. Jordan removed it to replace the tip seals and will test it in the bake lab before reinstalling.

With this configuration in place, we proceeded to pump down the main volume without issue (attachment 1). We monitored the pumpdown for about 45 min., until the pressure had reached ~1E-5 torr and TP3 had been transitioned to standby (low-speed) mode.

Summary of topology changes:

  • TP2 valved off and shut down until controller can be replaced
  • TP3 temporarily backing for TP1
  • Auxiliary dry pump temporarily backing for TP3
  • TP3 dry pump has been removed for repairs
Attachment 1: Pumpdown.png
  3153   Thu Jul 1 14:03:40 2010 josephbUpdatePEMTemporary disconnect of some PEM channels for ~20 minutes

In order to identify the output adapter of the BNC patch panel used for about 20 PEM channels, I had to disconnect its power and remove the back panel.  Channels coming into that panel (seismometers and so forth) was out from 1:36 to 1:56 pm.

I did a quick check of some of the channels and it looks like its working again after putting it all back together.

  3843   Tue Nov 2 00:17:01 2010 SureshConfigurationLockingTemporary changes to the Video Mux

Fiber coupling 1064 nm light at the end of X arm

This is 'work in progress'.  The attempt is to bring a few milliwatts of the 1064 nm light from the NPRO at the end of the South(X) Arm to the PSL table through an single mode optical fiber.  This would enable us to tune the two NPRO's to be less than 15 MHz apart by looking at their beat frequency before doubling.  Because we have a 1GHz bandwidth PD at 1064 nm, while the photodiode for green has a BW of about 30MHz.

A PBS (P-type) cube has been introduced into the beam of the X arm NPRO  (between the lamda/2 plate and the input lens of the doubling crystal).  By rotating the face of the PBS slightly away from normal incidence, I have diverted away 1.5mW of the 1064 light for coupling into the fiber. The beam has shifted slightly because of this and the green beam from the south arm has to be realigned to reach the PSL table.

A single mode fiber (Thorlabs SM980-5.8-125),  which was already laid half way, has been extended all the way to the PSL table. It runs along the  South arm in the cable tray. 

A pair of mirrors have been arranged in a zig-zag to steer the beam into a fiber coupler.  There was some hope that this coupler had been aligned at some point in the past and that attaching a fiber might result in some transmission.  But this is not the case and fiber coupler needs to be readjusted.

In order to see the light transmitted through the fiber, a camera has been set up on the PSL table.  Its output has been routed into the 'Ref Cavity reflected' video signal.  A video cable running from the ETMX to the Video-MUX used to be connected to the input channel 9 of the Video MUX.  This has now been shifted to output channel 25 of the MUX and disconnected from the camera at the ETMX.   The 'Ref Cav Refl.' video signal has been routed to the output channel 25.  The camera looking at the fiber output can now be seen on a local monitor at the end of the X arm and on the video monitor in the control room.

With the fiber disconnected, the 1064 nm beam was steered into the fiber coupler and its transmission maximised by observing  with an IR viewer.  The fiber was then connected and then the transmission at the PSL table was sought.  There was no transmission seen after a searching around this region for a few mins.

The plan is to purchase a Visual fault locator which would enable us to quickly get a rough alignment of the fiber coupler. A local vendor is listed as a distributor for this product from JDSU.  Contact info:

DuVac Electronics (EDGE)
Tel: 626-796-3291
Email: jack@duvac.com
1759 E Colorado Blvd
Pasadena, CA 91106


  3853   Wed Nov 3 15:13:55 2010 josephbUpdateCDSTemporary RFM slow read work around


Each RFM read in the c1mcs model is adding ~7 microseconds to the cycle time.  Adding too many pushes it over the 62 microsecond limit.

RFM writes do not have this problem.

Temporary Solution:

The fastest fix was to create a new front end model, called c1rfm, which does nothing but read in the MC1, MC2, MC3 PIT and YAW signals from the c1ioo machine, and then passes them along to the c1mcs model via shared memory, which is fast.

This means the data being sent is 2 cycles slow, one to go over the RFM, and one to go over shared memory.  It is running at 16384 cycles/second, so it shouldn't have much impact at the frequencies we use those channels for.

MC_L is still being sent directly to the c1mcs front end code via RFM.

Current Status:

The c1mcs model is running at  30-33 microseconds for CPU time.

The c1rfm model is running at 45-47 microseconds for CPU time.

All 7 channels, MC_L, MC1_PIT, MC1_YAW, MC2_PIT, MC2_YAW, MC3_PIT, MC3_YAW are responding.

The c1rfm model was added to the /diskless/root/etc/rtsystab file on the fb machine so that it automatically starts on the reboot of c1sus.

The USR and CPU time channels for c1rfm were added to the MCS_SLOW.ini file in /opt/rtcds/caltech/c1/chans/daq/ so that the framebuilder records them, namely:


The framebuilder was restarted to take these new channels into account.


Finish implementing and debugging the "round robin" RFM reader so as to not require a seperate model to be doing RFM reads in parallel.

Look into improving read speed by either merging timestamps and data into a single  or reading time stamp once every tenth or hundreth cycle, although this at best provides a factor of 2 improvement.

Check to see if RFM card being on the IO chassis or directly in the computer chassis makes a difference.

Get Alex and Rolf to improve RFM read speed.

  13645   Wed Feb 21 00:04:27 2018 gautamUpdateElectronicsTemporary RF power monitor setup

I made a voltage divider using a 20.47kohm and 1.07kohm (both values measured with a DMM). The whole thing is packaged inside a Pomona box I found lying around on the Electronics bench. I have hooked it up to the ALSY_I channel and will leave it so overnight. The INMON of this channel isn't DQed, but for this test, the 16Hz EPICS data will suffice. I've locked the EX laser to the arm, enabled slow temperature servo to allow overnight lock (hopefully) and disabled LSC mode (as locking the arm to the MC tends to break the green lock)

To convert the INMON counts to RF power, I will use (based on my earlier calibration of this monitor channel, see DCC document for the demod chassis).

\mathrm{P_{RF}} (\mathrm{dBm}) = \frac{19.13 \times \frac{cts}{1638.4} - 10.23}{0.12}

1AM update: Attachment #1 shows that the RF amplitude has been relatively stable (less than 10% of nominal value variation) over the course of the last hour or so. Even though there is some low frequency drift over timescales of ~20mins, no evidence of the wild ~20dB amplitude changes I saw last week. The signs are encouraging...

overnight update: See Attachment #2 - looking at the past 11 hours of second trend data during which the arm stayed locked, there actually seems to have been more significant variation in the beatnote amplitude. Swings of up to 6dBm are seen on a ~20min timescale, while there is also some longer term drift over 12 hours by a couple of dBm. There is probably a systematic error in the Y-axis, as I measured the RF power at the input of the power splitter at the LSC rack to be ~3dBm, so I expect something closer to 0dBm to be the LO input power which is what I am monitoring. So further debugging is required - I think I'll start by aligning the X fiber coupled beam to one of the fiber's special axes.

Attachment 1: RFbeatAmp.png
Attachment 2: BeatMouthX_RFAM_20180221.pdf
  3498   Tue Aug 31 16:42:26 2010 josephbUpdateCDSTemporarily reverting to CDS revision 2005

Apparently updating to the latest revision of the RCG has some issues with diaggui and awgtpman.  Alex had to do some recompiling up at Hanford which apparently took him some time.  He'll be coming by tomorrow to try to bring those codes to the front end machines.

As a temporary fix, until Alex gets here tomorrow, we're reverting to the 2005 revision in the svn of the cds code.  I'm placing it in the location it is supposed to go in the new advLIGO scheme, which is /opt/rtcds/caltech/c1/core/, which is where Keith had it at LLO.  Once we get the new codes working, we will do an svn update on that location and migrate our work to that install location, at which point I'll remove the old /cvs/cds/caltech/cds/advLigoRTS/ location.

ELOG V3.1.3-