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  8457   Mon Apr 15 17:44:28 2013 AlbertUpdateoptical tablesOptical Table Toolboxes Update

I decided to go see what the electrical tape looks like on the other tools.

These are the tools I felt were necessary to label with tape: (the others don't seem to be terribly important in terms of not interchanging between boxes)

photo.JPG

On another note I'm not sure why electrical tape can't be used on the Allen Wrenches too.

I also plan on ordering smaller flash lights for each table (this one is bulky and unwieldy), and filling in the gaps of the Allen Wrench sets as soon as I get the go-ahead.

  8502   Mon Apr 29 08:17:40 2013 AlbertUpdateoptical tablesOptical Table Toolboxes Update

Quote:

I decided to go see what the electrical tape looks like on the other tools.

These are the tools I felt were necessary to label with tape: (the others don't seem to be terribly important in terms of not interchanging between boxes)

photo.JPG

On another note I'm not sure why electrical tape can't be used on the Allen Wrenches too.

I also plan on ordering smaller flash lights for each table (this one is bulky and unwieldy), and filling in the gaps of the Allen Wrench sets as soon as I get the go-ahead.

 

  11006   Wed Feb 11 18:44:53 2015 manasaUpdateGeneralOptical fiber module

I have moved the optical fiber module for FOL to the PSL table. It is setup on the optical table right now for testing.

Once tests are done, the box will move to the rack inside the PSL enclosure. 

While doing any beat note alignment, please watch out for the loose fibers at the north side of the PSL enclosure until they are sheilded securely (probably tomorrow morning).

  16445   Tue Nov 2 18:54:41 2021 Anchal, PacoUpdateBHDOptical fibres laid for BHD upgrade

We successfully laid down all required optical fibre fiber cables from 1X4-1X7 region to 1Y1-1Y3 region today. This includes following cables:

  • Timing fibre fiber from Master Timing Synchornizer D050239 on 1X6 to C1SU2 I/O chassis on 1Y1.
  • Timing fibre fiber from Master Timing Synchornizer D050239 on 1X6 to C1BHD I/O chassis on 1Y3.
  • CX4 cable from Dolphin Card on 1X4 to C1SU2 FE on 1Y1 for IPC.
  • CX4 cable from Dolphin Card on 1X4 to C1BHD FE on 1Y3 for IPC.
  • DAQ Network extension fibre fiber optic cable from DAQ Network Switch on 1X7 to another switch we mounted on 1Y3 for local DAQ network distribution.
  17274   Wed Nov 16 18:41:17 2022 yutaSummaryBHDOptical gain calibrations for BHD MICH

Optical gains of AS55 and BH55 are calibrated for BHD MICH.

LO-ITM single bounce:
 With LO-ITM signle bounce fringe, optical gain of BH55_Q is measured using a method similar to MICH calibration in AS55 (40m/16929).
 Demodulation phase for BH55 is tuned to minimize I when LO-ITM is freeswinging (using getPhaseAngle.py).
 (Notebook: /opt/rtcds/caltech/c1/Git/40m/scripts/CAL/BHD/BHDOpticalGainCalibration.ipynb)
 Results are the following:

 LO-ITMY fringe: 7.84e9 counts/m (demod phase 147.1 +/- 0.3 deg) See Attachment #1
 LO-ITMX fringe: 8.44e9 counts/m (demod phase 149.6 +/- 0.4 deg) See Attachment #1

 Difference in the optimal demodulation phase 2.5 +/- 0.5 deg agrees with half of Schnupp asymmetry, as expected (40m/17007).
 Difference in the optical gain for LO-ITMY and LO-ITMX is probably from statistical fluctuation.


BHD MICH:
 Sensing matrix was measured by injecting a line at BS (300 counts @ 211.1 Hz), LO1 (5000 counts @ 287.1 Hz) and AS1 (5000 counts @ 281.79 Hz), when MICH is locked with AS55_Q and LO PHASE is locked with BH55_Q (both with no offset).
 Using the sensing matrix, demodulation phase was tuned to minimize I phase for MICH signal in AS55 and LO1 signal in BH55.
 After the demodulation phase tuning. sensing matrix was measured to be the following.
 See, also Attachment #3 for injected peaks. I phase signal is successfully suppressed by at least an order of magnitude.
 (Notebook: /opt/rtcds/caltech/c1/Git/40m/scripts/CAL/SensingMatrix/MeasureSensMatBHD.ipynb)

Sensing Matrix with the following demodulation phases (counts/counts)
{'AS55': -160.15695076011946, 'BH55': 154.13916838400047}
      Sensors           MICH @211.1 Hz          LO1 @287.1 Hz            AS1 @281.79 Hz           
C1:LSC-AS55_I_ERR_DQ    1.22e-05 (120.53 deg)   7.24e-07 (85.64 deg)     1.26e-06 (40.42 deg)    
C1:LSC-AS55_Q_ERR_DQ    2.95e-03 (-101.62 deg)  1.24e-06 (-80.43 deg)    1.69e-06 (152.31 deg)    
C1:LSC-BH55_I_ERR_DQ    1.28e-03 (80.95 deg)    3.44e-06 (109.31 deg)    2.22e-06 (154.40 deg)    
C1:LSC-BH55_Q_ERR_DQ    7.44e-03 (77.38 deg)    2.56e-04 (-59.85 deg)    2.42e-04 (6.40 deg)    
C1:HPC-BHDC_DIFF_OUT    2.21e-03 (82.45 deg)    4.37e-05 (121.87 deg)    3.61e-05 (-169.09 deg)

 Using BS actuation efficiency of 26.08e-9 /f^2 m/counts (40m/16929), optical gain for AS55_Q and BHDC_DIFF for MICH is

2.95e-03 / (26.08e-9/(211.1**2)) = 5.04e9 counts/m (AS55_Q for MICH)
2.21e-03 / (26.08e-9/(211.1**2)) = 3.78e9 counts/m (BHDC_DIFF for MICH)

 For AS55_Q, this is a factor of 4~5 higher than the previous measurement from free swing (40m/16929). Why?
 Free swing measurement was done again, and this gave 1.24e9 counts/m, which is consistent with the previous measurement (see Attachment #3).

 Using LO1 and AS1 actuation efficiencies of 3.14e-8 /f^2 m/counts (40m/17206), optical gains for BH55_Q for LO1 and AS1 are

2.56e-04 / (3.14e-8/(287.1**2)) = 6.72e8 counts/m (BH55_Q for LO1)
2.42e-04 / (3.14e-8/(281.79**2)) = 6.12e8 counts/m (BH55_Q for AS1)

Next:
 - Compare them with expected values
 - Measure them with different locking points (different LO phases, MICH offsets)
 - Investigate why MICH optical gain in AS55 is 4~5 times higher than free swing measurement (use different modulation frequency?)

Summary of actuation calibration so far (counts from C1:LSC-xx_EXC or C1:SUS-xx_LSC_EXC):
BS   : 26.08e-9 /f^2 m/counts (see 40m/16929)
ITMX :  5.29e-9 /f^2 m/counts (see
40m/16929)
ITMY :  4.74e-9 /f^2 m/counts (see
40m/16929)
ETMX : 10.91e-9 /f^2 m/counts (see 40m/16977 and 40m/17014)
ETMY : 10.91e-9 /f^2 m/counts (see 40m/16977)

MC2 : -14.17e-9 /f^2 m/counts in arm length (see 40m/16978)
MC2 :   5.06e-9 /f^2 m/counts in IMC length (see 40m/16978)
LO1 : 3.14e-8 / f^2 m/counts
(see 40m/17206)
LO2 : 2.52e-8 / f^2 m/counts (see 40m/17206)
AS1 : 3.14e-8 / f^2 m/counts (see 40m/17206)
AS4 : 2.38e-8 / f^2 m/counts (see 40m/17206)

Attachment 1: Screenshot_2022-11-16_18-57-12.png
Screenshot_2022-11-16_18-57-12.png
Attachment 2: Screenshot_2022-11-16_18-49-53_BHDMICHCalLines.png
Screenshot_2022-11-16_18-49-53_BHDMICHCalLines.png
Attachment 3: LSC-AS55_Q_ERR_DQ_1352689642.png
LSC-AS55_Q_ERR_DQ_1352689642.png
  17279   Thu Nov 17 14:12:58 2022 yutaSummaryBHDOptical gain calibrations for BHD MICH with lower UGF

[Paco, Yuta]

We found that MICH UGF was unexpectedly high, ~200 Hz, in the measurement yesterday, which makes the closed loop gain to be more than one at MICH line injection at 211.1 Hz.
We did optical gain calibrations for AS55, BH55 and BHDC_DIFF in BHD MICH again with UGF at around 10 Hz.
This solved the inconsistent result with free swing calibration.

What we did:
 Did the same measurement for BHD MICH as written in 40m/17274, but with MICH UGF of ~10 Hz and LO PHASE UGF of ~15 Hz (see OLTFs in Attachment #1, and filter configurations in Attachment #2).
 Updated sensing matrix is as follows

Sensing Matrix with the following demodulation phases (counts/counts)
{'AS55': -163.52789698340882, 'BH55': 152.7860744565449}
      Sensors        	MICH @211.1 Hz       	LO1 @287.1 Hz       	AS1 @281.79 Hz       	
C1:LSC-AS55_I_ERR_DQ	1.85e-05 (-118.82 deg)	3.31e-07 (-32.19 deg)	7.86e-07 (112.27 deg)	
C1:LSC-AS55_Q_ERR_DQ	7.32e-04 (59.57 deg)	1.19e-06 (158.17 deg)	9.07e-07 (-92.25 deg)	
C1:LSC-BH55_I_ERR_DQ	5.02e-04 (-123.21 deg)	1.79e-05 (-26.73 deg)	1.76e-05 (-120.23 deg)	
C1:LSC-BH55_Q_ERR_DQ	1.75e-03 (59.57 deg)	2.71e-04 (-22.64 deg)	2.56e-04 (-114.37 deg)	
C1:HPC-BHDC_DIFF_OUT	1.00e-03 (-115.93 deg)	3.09e-05 (-14.99 deg)	2.84e-05 (-110.23 deg)	

 Using BS actuation efficiency of 26.08e-9 /f^2 m/counts (40m/16929), optical gain for AS55_Q and BHDC_DIFF for MICH is

7.32e-03 / (26.08e-9/(211.1**2)) = 1.25e9 counts/m (AS55_Q for MICH) This is consistent with freeswing measurement (1.24e9 m/counts) 40m/17274
1.00e-03 / (26.08e-9/(211.1**2)) = 1.71e9 counts/m (BHDC_DIFF for MICH)

 Using LO1 and AS1 actuation efficiencies of 3.14e-8 /f^2 m/counts (40m/17206), optical gains for BH55_Q for LO1 and AS1 are

2.71e-04 / (3.14e-8/(287.1**2)) = 7.12e8 counts/m (BH55_Q for LO1)
2.56e-04 / (3.14e-8/(281.79**2)) = 6.47e8 counts/m (BH55_Q for AS1)

  (Notebook: /opt/rtcds/caltech/c1/Git/40m/scripts/CAL/SensingMatrix/MeasureSensMatBHD.ipynb)

Next:
 - Compare them with expected values
 - Measure them with different locking points (different LO phases, MICH offsets; LO phase can be calibrated using optical gain calibration of BH55_Q)

Attachment 1: Screenshot_2022-11-17_14-39-17_MICHLOPHASEOLTF.png
Screenshot_2022-11-17_14-39-17_MICHLOPHASEOLTF.png
Attachment 2: Screenshot_2022-11-17_14-41-40_LowUGFConfiguration.png
Screenshot_2022-11-17_14-41-40_LowUGFConfiguration.png
  12104   Mon May 2 19:14:18 2016 gautamUpdateendtable upgradeOptical layout almost complete

With Steve's help, I installed the Oplev earlier today. I adjusted the positions of the two lenses until I deemed the spot size on the QPD satisfactory by eye. As a quick check, I verified using the DTT template that the UGF is ~5Hz for both pitch and yaw. There is ~300uW of power incident on the QPD (out of ~2mW from the HeNe). In terms of ADC counts, this is ~13,000 counts which is about what we had prior to taking the endtable apart. There are a couple of spots from reflections off the black glass plate in the vacuum chamber, but in general, I think the overall setup is acceptable.

This completes the bulk of the optical layout. The only bits remaining are to couple the IR into the fiber and to install a power monitoring PD. Pictures to follow shortly. 

Now that the layout is complete, it remains to optimize various things. My immediate plan is to do the following:

  1. Maximize green transmission by tweaking alignment. I should also do a quick check using mirror specs to see that the measured transmitted green power compares favourably to what is expected.
  2. Check the green PDH loop transfer function at the X end - this will allow me to set the gain on the uPDH box systematically.
  3. Re-establish green beats, check noise performance.
  4. There are possibly multiple beam dumps that have to be installed. For now, I've made sure that no high power IR beams are incident on the enclosure. But there are a couple of red and green beams that have to be accounted for.

I will also need to upload the layout drawing to reflect the layout finally implemented.


Not directly related:

The ETMx oplev servo is now on. I then wanted to see if I could lock both arms to IR. I've managed to do this successfully - BUT I think there is something wrong with the X arm dither alignment servo. By manually tweaking the alignment sliders on the IFOalign MEDM screen, I can get the IR transmission up to ~0.95. But when I run the dither, it drives the transmission back down to ~0.6, where it plateaus. I will need to investigate further. 

 

GV Edit: There was some confusion while aligning the Oplev input beam as to how the wedge of the ETM is oriented. We believe the wedge is horizontal, but its orientation (i.e. thicker side on the right or left?) was still ambiguous. I've made a roughly-to-scale sketch (attachment #1) of what I think is the correct orientation - which turns out to be in the opposite sense of the schematic pinned up in the office area.. Does this make sense? Is there some schematic/drawing where the wedge orientation is explicitly indicated? My search of the elog/wiki did not yield any..

Attachment 1: ETMX_wedge.pdf
ETMX_wedge.pdf
  12122   Thu May 19 16:29:20 2016 SteveUpdateendtable upgradeOptical layout almost complete

 

 

Attachment 1: ETMX_4x3_closed.jpg
ETMX_4x3_closed.jpg
Attachment 2: sealedETMXenclosure.jpg
sealedETMXenclosure.jpg
  7090   Mon Aug 6 11:07:06 2012 ManasaUpdate40m UpgradingOptical layout updated

ACAD files of the 40m optical layout have been updated as per the vent in Aug 2011.

Files are available at the 40m svn docs-->Upgrade12-->Opt_Layout2011.

 

  7125   Wed Aug 8 20:51:56 2012 ManasaUpdate40m UpgradingOptical layout updated

Quote:

ACAD files of the 40m optical layout have been updated as per the vent in Aug 2011.

Files are available at the 40m svn docs-->Upgrade12-->Opt_Layout2011.

 

 To ease the pain of hunting files, optical layout ACAD files have been moved to a new directory 40M_Optical Layout in the repository. Relevant files from directories Upgrade12 and upgrade 08 will be moved to "40M_Optical Layout" very soon and eventually these old directories will be removed. 

  7222   Fri Aug 17 18:49:55 2012 ManasaUpdate40m UpgradingOptical layout updated

Quote:

Quote:

ACAD files of the 40m optical layout have been updated as per the vent in Aug 2011.

Files are available at the 40m svn docs-->Upgrade12-->Opt_Layout2011.

 

 To ease the pain of hunting files, optical layout ACAD files have been moved to a new directory 40M_Optical Layout in the repository. Relevant files from directories Upgrade12 and upgrade 08 will be moved to "40M_Optical Layout" very soon and eventually these old directories will be removed. 

Changes mentioned by Koji and Steve have been updated to the files (except for the cable connector which have been added but whose part number has to be found to match accurately with the current layout). The file in the directory should now match the current setup after the last vent Aug 2011.

Let me know if you find any mismatch between the current setup and the layout.

Plans about new installations/reconfiguration during the new vent will be carried out in a separate file.

  13432   Thu Nov 16 13:57:01 2017 gautamUpdateOptical LeversOptical lever noise

I disabled the OL loops for ITMX, ITMY and BS at GPStime 1194897655 to come up with an Oplev noise budget. OL spots were reasonably well centered - by that, I mean that the PIT/YAW error signals were less than 20urad in absolute value.

Attachment #1 is a first look at the DTT spectra - I wonder why the BS Oplev signals don't agree with the ITMs at ~1Hz? Perhaps the calibration factor is off? The sensing noise not really flat above 100Hz - I wonder what all those peaky features are. Recall that the ITM OLs have analog whitening filters before the ADC, but the BS doesn't...

In Attachment #2, I show comparison of the error signal spectra for ITMY and SRM - they're on the same stack, but the SRM channels don't have analog de-whitening before the ADC.

For some reason, DTT won't let me save plots with latex in the axes labels...

Attachment 1: VertexOLnoise.pdf
VertexOLnoise.pdf
Attachment 2: ITMYvsSRM.pdf
ITMYvsSRM.pdf
  13433   Thu Nov 16 15:43:01 2017 ranaUpdateOptical LeversOptical lever noise

I bet the calibration is out of date; probably we replaced the OL laser for the BS and didn't fix the cal numbers. You can use the fringe contrast of the simple Michelson to calibrate the OLs for the ITMs and BS.

  13156   Tue Aug 1 16:05:01 2017 gautamUpdateOptical LeversOptical lever tuning - cost function construction

Summary:

I've been trying to put together the cost-function that will be used to optimize the Oplev loop shape. Here is what I have so far.

Details:

All of the terms that we want to include in the cost function can be derived from:

  1. A measurement of the open-loop error signal [using DTT, calibrated to urad/rtHz]. We may want a breakdown of this in terms of "sensing noises" and "disturbances" (see the previous elog in this thread), but just a spectrum will suffice for the optimal controller given the current noises.
  2. A model of the optical plant, P(s) [validated with a DTT swept-sine measurement]. 
  3. A model of the controller, C(s). Some/all of the poles and zeros of this transfer function is what the optimization algorithm will tune to satisfy the design objectives.

From these, we can derive, for a given controller, C(s):

  1. Closed-loop stability (i.e. all poles should be in the left-half of the complex plane), and exactly 2 UGFs. We can use MATLAB's allmargin function for this. An unstable controller can be rejected by assigning it an extremely high cost.
  2. RMS rrror signal suppression in the frequency band (0.5Hz - 2Hz). We can require this to be >= 15dB (say).
  3. Minimize gain peaking and noise injection - this information will be in the sensitivity function, \left | \frac{1}{1+P(s)C(s)} \right |. We can require this to be <= 10dB (say).
  4. RMS of the control signal between 10 Hz and 200 Hz, multiplied by the digital suspension whitening filter, should be <10% of the DAC range (so that we don't have problems engaging the coil de-whitening).
  5. Smallest gain margin (there will be multiple because of the various notches we have) should be > 10dB (say). Phase margin at both UGFs should be >30 degrees.
  6. Terms 1-5 should not change by more than 10% for perturbations in the plant model parameters (f0 and Q of the pendulum) at the 10% (?) level. 

We can add more terms to the cost function if necessary, but I want to get some minimal set working first. All the "requirements" I've quoted above are just numbers out of my head at the moment, I will refine them once I get some feeling for how feasible a solution is for these requirements.

Quote:

An elog with a first pass at a mathematical formulation of the cost-function for controller optimization to follow shortly.


For a start, I attempted to model the current Oplev loop. The modeling of the plant and open-loop error signal spectrum have been described in the previous elogs in this thread.

I am, however, confused by the controller - the MEDM screen (see Attachment #2) would have me believe that the digital transfer function is FM2*FM5*FM7*FM8*gain(10). However, I get much better agreement between the measured and modelled in-loop error signal if I exclude the overall gain of 10 (see Attachments #1 for the models and #3 for measurements).

What am I missing? Getting this right will be important in specifying Term #4 in the cost function...

GV Edit 2 Aug 0030: As another sanity check, I computed the whitened Oplev control signal given the current loop shape (with sub-optimal high-frequency roll-off). In Attachment #4, I converted the y-axis from urad/rtHz to cts/rtHz using the approximate calibration of 240urad/ct (and the fact that the Oplev error signal is normalized by the QPD sum of ~13000 cts), and divided by 4 to account for the fact that the control signal is sent to 4 coils. It is clear that attempting to whiten the coil driver signals with the present Oplev loop shapes causes DAC saturation. I'm going to use this formulation for Term #4 in the cost function, and to solve a simpler optimization problem first - given the existing loop shape, what is the optimal elliptic low-pass filter to implement such that the cost function is minimized? 


There is also the question of how to go about doing the optimization, given that our cost function is a vector rather than a scalar. In the coating optimization code, we converted the vector cost function to a scalar one by taking a weighted sum of the individual components. This worked adequately well.

But there are techniques for vector cost-function optimization as well, which may work better. Specifically, the question is  if we can find the (infinite) solution set for which no one term in the error function can be made better without making another worse (the so-called Pareto front). Then we still have to make a choice as to which point along this curve we want to operate at.

Attachment 1: loopPerformance.pdf
loopPerformance.pdf
Attachment 2: OplevLoop.png
OplevLoop.png
Attachment 3: OL_errSigs.pdf
OL_errSigs.pdf
Attachment 4: DAC_saturation.pdf
DAC_saturation.pdf
  13141   Tue Jul 25 02:03:59 2017 gautamUpdateOptical LeversOptical lever tuning thoughts

Summary:

Currently, I am unable to engage the coil-dewhitening filters without destroying cavity locks. One reason why this is so is because the present Oplev servos have a roll-off at high frequencies that is not steep enough - engaging the digital whitening + analog de-whitening just causes the DAC output to saturate. Today, Rana and I discussed some ideas about how to approach this problem. This elog collects these thoughts. As I flesh out these ideas, I will update them in a more complete writeup in T1700363 (placeholder for now). Past relevant elogs: 5376, 9680

  1. Why do we need optical levers?
    • ​​To stabilize the low-frequency seismic driven angular motion of the optics.
  2.  In what frequency range can we / do we need to stabilize the angular motion of the optics? How much error signal suppression do we need in the control band? How much is achievable given the current Oplev setup?
    • ​​To answer these questions, we need to build a detailed Oplev noise budget.
    • Ultimately, the Oplev error signal is sensing the differential motion between the suspended optic and the incident laser beam.
    • What frequency range does laser beam jitter dominate the actual optic motion? What about mechanical drifts of the optical tables the HeNes sit on? And for many of the vertex optics, the Oplev beam has multiple bounces on steering mirrors on the stack. What is the contribution of the stack motion to the error signal?
    • The answers to the above will tell us what lower and upper UGFs we should and can pick. It will also be instructive to investigate if we can come up with a telescope design near the Oplev QPD that significantly reduces beam jitter effects (see elog 10732). Also, can we launch/extract the beam into/from the vacuum chamber in such a way that we aren't so susceptible to motion of the stack?
  3. What are some noises that have to be measured and quantified?
    • Seismic noise
    • ​Shot noise
    • Electronics noise of the QPD readout chain
    • HeNe intensity noise (does this matter since we are normalizing by QPD sum?)
    • HeNe beam pointing / jitter noise (How? N-corner hat method?)
    • Stack motion contribution to the Oplev error signal
  4. How do we design the Oplev controller?
    • ​The main problem is to frame the right cost function for this problem. Once this cost function is made, we can use MATLAB's PSO tool (which is what was used for the PR3 coating design optimization, and also successfully for this kind of loop shaping problems by Rana for aLIGO) to find a minimum by moving the controller poles and zeros around within bounds we define.
  5. What terms should enter the cost function?

    • ​In addition to those listed in elog 5376
    • We need the >10Hz roll-off to be steep enough that turning on the digital whitening will not significantly increase the DAC output RMS or drive it to saturation.
    • We'd like for the controller to be insensitive to 5% (?) errors in the assumed optical plant and noise models i.e. the closed loop shouldn't become unstable if we made a small error in some assumed parameters.
    • Some penalty for using excessive numbers of poles/zeros? Penalty for having too many high-frequency features.
  6. Other things to verify / look into
    • ​Verify if the counts -> urad calibration is still valid for all the Oplevs. We have the arm-cavity power quadratic dependance method, and the geometry method to do this.
    •  Check if the Oplev error signals are normalized by the quadrant sum.
    • How important is it to balance the individual quadrant gains?
    • Check with Koji / Rich about new QPDs. If we can get some, perhaps we can use these in the setup that Steve is going to prepare, as part of the temperature vs HeNe noise invenstigations.

Before the CDS went down, I had taken error signal spectra for the ITMs. I will update this elog tomorrow with these measurements, as well as some noise estimates, to get started.

  13147   Fri Jul 28 15:36:32 2017 gautamUpdateOptical LeversOptical lever tuning thoughts

Attachment #1 - Measured error signal spectrum with the Oplev loop disabled, measured at the IN1 input for ITMY. The y-axis calibration into urad/rtHz may not be exact (I don't know when this was last calibrated).

From this measurement, I've attempted to disentangle what is the seismic noise contribution to the measured plant output.

  • To do so, I first modelled the plant as a pair of complex poles @0.95 Hz, Q=3. This gave the best agreement with measurement by eye, I didn't try and optimize this too carefully. 
  • Next, I assumed all the noise between DC-10Hz comes from only seismic disturbance. So dividing the measured PSD by the plant transfer function gives the spectrum of the seismic disturbance. I further assumed this to be flat, and so I averaged it between DC-10Hz.
  • This will be a first seismic noise model to the loop shape optimizer. I can probably get a better model using the GWINC calculations but for a start, this should be good enough.

It remains to characterize various other noise sources.

Quote:

Before the CDS went down, I had taken error signal spectra for the ITMs. I will update this elog tomorrow with these measurements, as well as some noise estimates, to get started.


I have also confirmed that the "QPD" Simulink block, which is what is used for Oplevs, does indeed have the PIT and YAW outputs normalized by the SUM (see Attachment #2). This was not clear to me from the MEDM screen.


GV 30 Jul 5pm: I've included in Attachment #3 the block diagram of the general linear feedback topology, along with the specific "disturbances" and "noises" w.r.t. the Oplev loop. The measured (open loop) error signal spectrum of Attachment #1 (call it y) is given by:

y_{meas}(s) = P(s)\sum_{i=1}^{3}d_{i}(s) + \sum_{k=1}^{4}n_{k}(s)

If it turns out that one (or more) term(s) in each of the summations above dominates in all frequency bands of interest, then I guess we can drop the others. An elog with a first pass at a mathematical formulation of the cost-function for controller optimization to follow shortly.

Attachment 1: errSig.pdf
errSig.pdf
Attachment 2: QPD_simulink.png
QPD_simulink.png
Attachment 3: feedbackTopology.pdf
feedbackTopology.pdf
  14733   Mon Jul 8 17:33:10 2019 KruthiUpdateLoss MeasurementOptical scattering measurements

I came across a paper (see reference) where they have used DAOPHOT, an astronomical software tool developed by NOAO, to study the point scatterers in LIGO test masses using images of varying exposure times. I'm going through the paper now. I think using this we can analyze the MC2 images and make some interesting observations.

Reference:  L.Glover et al., Optical scattering measurements and implications on thermal noise in Gravitational Wave detectors test-mass coatings Physics Letters A. 382. (2018)

  7774   Sat Dec 1 16:58:14 2012 ManasaUpdateWIKI-40M UpdateOptical tables

I have updated the wiki with the layout of the out-of-vac optical tables: Updated optical tables

I used the new camera to take pictures.

Lesson learnt after the update:

To use the new canon to take better pictures of optics tables; set the camera to manual mode; no flash and iso at around 800 or higher if you can hold the camera still for that long. The autofocus works beautifully...so you will not need any minor tweaking of lens to take pictures. 

  3287   Sun Jul 25 18:47:23 2010 AlbertoUpdateSVNOptickle 40mUpgrade model updated to include short cavity length corrections

I uploaded an updated optickle model of the upgrade to the SVN directory with the optickle models (here).

  643   Mon Jul 7 19:15:38 2008 AlbertoUpdateGeneralOptics alignement on the ABS length experiment
Today I started setting up the PLL instruments to lock the frequency of the NPRO beam to the IFO beam. with no need of a new alignment after the weekend I was able to see the beat again, although this time I found at a different temperature of the NPRO laser of about 54 degrees (vs 51 of the last time).
I've got the Marconi as local oscillator (LO), the mixer Koji suggetsed, the SR560 and a 5 MHz low pass filter to cut the 33, 66 and 99 MHz present in the output signal from the PD. The filter worked well and I was able to single out only the beat resonance from the power spectrum.
In the attempt to enhance the amplitude of the beat, as Koji suggested, I tried to work on the alignment of the steering mirrors. While I was doing that, for some reason the pre-modecleaner lost the alignment and I had to ask John to help me lock it again. during the process I lost the old alignment but at the end I got a new one, apparently (from the camera) even better than the other. Although after that the beats were gone. Actually after the lock-in of the PMC the IFO beam didn't look as good as before, so it might be also for that reason.

I'll try again tomorrow, after that probably tonight Rob is going to reset the alignments of the interferometers.
  7313   Wed Aug 29 21:02:45 2012 JenneUpdateIOOOptics between Faraday and PRM are centered, realigned

[Jenne, Suresh, with support from Jamie and Koji]

MC spots measured, MC1, MC3 no change.

No clipping going through Faraday.

Beam hitting to the right of center of PZT1.  It was translated sideways so we are now hitting it on the center.  Knobs adjusted so we hit center of MMT1.

Beam totally obscured by Faraday on the way to MMT2.  MMT2 moved north, so that we clear the Faraday by more than a beam diameter.  MMT1 knobs adjusted to hit center of MMT2.

MMT2 knobs adjusted to hit center of PZT2.

PZT2 didn't have enough range with knobs, so we loosened it, pointed then adjusted with knobs so we're hitting center of PRM. 

We need to check spot centering on PRM with camera tomorrow.

Suresh checked that we're not clipped by IP ANG/POS pickoff mirrors, but we haven't done any alignment of IP ANG/POS.

 

Tomorrow:  Open ITMX door.  Check with Watek that we're hitting center of PRM.  Then look to see if we're hitting center of PR2.  Then, continue through the chain of optics.

  5729   Mon Oct 24 17:23:14 2011 SUS_DiagonalizerUpdateSUSOptics kicked
This is a cron-elog test. No optics have been kicked.
  5823   Sun Nov 6 09:39:25 2011 Dr. SUSUpdateSUSOptics kicked
All suspended optics have been kicked at Sun Nov 6 09:39:25 PST 2011. Watchdogs will be reengaged in 5 hours. Please refrain from disturbing the optics in the meantime.

EDIT ZK: After all that, I left the 'doirun' bit off in runDrSUS. I ran it manually at the above time.
  7523   Wed Oct 10 21:50:39 2012 SUS_DiagonalizerUpdateSUSOptics kicked
All suspended optics have been kicked at Wed Oct 10 21:50:39 PDT 2012. Watchdogs will be reengaged in 90 minutes.
  7524   Thu Oct 11 00:22:58 2012 SUS_DiagonalizerUpdateSUSOptics kicked

Quote:
All suspended optics have been kicked at Wed Oct 10 21:50:39 PDT 2012. Watchdogs will be reengaged in 90 minutes.


New SUS input matrix diagonalization complete.
  7979   Thu Jan 31 22:14:11 2013 ranaSummaryASCOptics lit

 Gouy not Guoy:

http://www.rp-photonics.com/gouy_phase_shift.html

pronounced Goo-eee, with the emphasis on the second syllable.

  7982   Fri Feb 1 12:22:27 2013 ZachSummaryASCOptics lit

It's OK; even Siegman got it wrong---48 times.

RA: NO, stil not OK.

Quote:

 Gouy not Guoy:

http://www.rp-photonics.com/gouy_phase_shift.html

pronounced Goo-eee, with the emphasis on the second syllable.

 

  13981   Mon Jun 18 14:32:42 2018 gautamUpdatePSLOptics on AS table

Yesterday, I moved the following optics:

  1. Lens in front of AS110 PD.
  2. BS splitting light between AS110 and AS55.

After moving these components around a bit, I locked them down once I was happy that the beam was pretty well centered on both of them, and also on AS110 and AS55 (measured using O'scope with single bounce from one ITM, other optics misaligned).

The beam was close to clipping on the lens mentioned in #1, probably because this wasn't checked when the 90-10 BS was installed for the AUX laser. Furthermore, I believe we are losing more than 10% of the light due to this BS. The ASDC (which is derived from AS55 PD) level is down at ~110cts as the Michelson is fringing, while it used to be ~200 cts. I will update with a power measurement shortly. But I think we should move ahead with the plan to combine the beam into the IFO's AS mode as discussed at the meeting last week.


Unrelated to this work, but c1psl and c1iscaux were keyed. 


ASDC has something weird going on with it - my main goal yesterday was to calibrate the actuators of ITMX, ITMY and BS using the Michelson. But with the Michelson locked on a dark fringe, the ASDC level changed by up to 50 counts seemingly randomly (bright fringe was ~1000 cts, I had upped the whitening gain to +21dB), even though the CCD remained clearly dark throughout. Not sure if the problem is in the readout electronics or in the PD itself.

  13982   Mon Jun 18 15:59:17 2018 johannesUpdatePSLOptics on AS table
Quote:

Furthermore, I believe we are losing more than 10% of the light due to this BS. The ASDC (which is derived from AS55 PD) level is down at ~110cts as the Michelson is fringing, while it used to be ~200 cts. I will update with a power measurement shortly. But I think we should move ahead with the plan to combine the beam into the IFO's AS mode as discussed at the meeting last week.

Is the 10% specified for P-Pol or for UNP? I contacted CVI about beamsplitters, since their website doesn't list a BS1-1064-90-... option on the website. They say a R=90% beamsplitter would be a custom job. The closest stock item they got is BS1-1064-95-2025-45UNP specified at R=95% for UNPolarized beams. They were kind enough to sent me the measured transmission curves for a recent lot of these, which is attached was uploaded to the wiki [Elog Police K: NO PROPRIETARY DOCUMENTS ON THE ELOG, which is public. Put it on our wiki and put the link here]. The figure is not labeled, but according to the contact Red is S-Pol and Blue is P-Pol, which means that this one actually has R=~90% for P, pretty much what we want. We'll need to buy two of these to make the swap in the setup.

Back to your original point: There's only a BS1-1064-10-2025-45UNP on the website, so unless we got these as custom items, the R for P-Pol is probably NOT actually 10%, just somewhere between 0% and 20%

  13983   Mon Jun 18 16:57:54 2018 KojiUpdatePSLOptics on AS table

Of course, many (but no all) of the optics were custom-ordered back in ~2000.

  14006   Fri Jun 22 14:18:04 2018 SteveUpdatePSLOptics on AS table

 

Quote:
Quote:

Furthermore, I believe we are losing more than 10% of the light due to this BS. The ASDC (which is derived from AS55 PD) level is down at ~110cts as the Michelson is fringing, while it used to be ~200 cts. I will update with a power measurement shortly. But I think we should move ahead with the plan to combine the beam into the IFO's AS mode as discussed at the meeting last week.

Is the 10% specified for P-Pol or for UNP? I contacted CVI about beamsplitters, since their website doesn't list a BS1-1064-90-... option on the website. They say a R=90% beamsplitter would be a custom job. The closest stock item they got is BS1-1064-95-2025-45UNP specified at R=95% for UNPolarized beams. They were kind enough to sent me the measured transmission curves for a recent lot of these, which is attached was uploaded to the wiki [Elog Police K: NO PROPRIETARY DOCUMENTS ON THE ELOG, which is public. Put it on our wiki and put the link here]. The figure is not labeled, but according to the contact Red is S-Pol and Blue is P-Pol, which means that this one actually has R=~90% for P, pretty much what we want. We'll need to buy two of these to make the swap in the setup.

Back to your original point: There's only a BS1-1064-10-2025-45UNP on the website, so unless we got these as custom items, the R for P-Pol is probably NOT actually 10%, just somewhere between 0% and 20%

4  std cataloge item fused silica  BS1-1064-95-2025-45UNP 

ordered today. They will arrive no later than July 13, 2018

  10454   Thu Sep 4 18:30:13 2014 GabrieleSummaryASCOptimal Gouy phase for POP QPD

 Jenne asked me to simulate the signals on POP QPD when moving different mirrors, as a function of the Gouy phase where the QPD is placed.

I used the opportunity to create a MIST simulation file of the entire 40m interferometer, essentially based on my aLIGO configuration file. I used the recycling cavity lengths obtained from our survey, and other parameters from the wiki page. The configuration file is attached (fortymeters.mist).

Coming back to the main simulation, here is the result, both for the "regular" POP QPD and for a 22MHz demodulated one. The Gouy phase is measured starting from PR2. Cavity mirrors are easily decoupled from PRM in the "regular" QPD. As already demonstrated in a previous simulation, ETMs signals are very small in the 22 MHz QPD. Moreover, it is possible to zero the contribution from ITMs by choosing the right Gouy phase, at the price of a reduction of the PRM signal by a factor of 3-4. Simulation files are attached.

pop_qpd_dc.png

 

Attachment 2: fortymeters.mist
###########################################################################
# Configuration file for full dual recycled 40m interferometer
classname FortyMeters
################################################################ Parameters

# General parameters
const Pin 1             # input power

# Mirror parameters
const T_ITM 0.01384     # ITM transmission [from https://wiki-40m.ligo.caltech.edu/Core_Optics]
... 143 more lines ...
Attachment 3: fortymeters_pop_qpd.mist
###########################################################################
# Configuration file for full dual recycled 40m interferometer
classname FortyMetersPOP_QPD
################################################################ Parameters

# General parameters
const Pin 1             # input power

# Mirror parameters
const T_ITM 0.01384     # ITM transmission [from https://wiki-40m.ligo.caltech.edu/Core_Optics]
... 148 more lines ...
Attachment 4: pop_qpd.m
% compile and create simulation class
clear classes
MIST('fortymeters_pop_qpd.mist');
s = FortyMetersPOP_QPD(4);

% set angular motion of ITMs, ETMs and PRM
s.ETMX.setMotionShape('pitch');
s.ETMY.setMotionShape('pitch');
s.ITMX.setMotionShape('pitch');
s.ITMY.setMotionShape('pitch');
... 47 more lines ...
  11407   Tue Jul 14 10:23:27 2015 IgnacioUpdateGeneralOptimal detector array placement thoughts

Over the past few days, I've been thinking about how to workout the details conerning Rana's request about a 'map' of the vicinity of the 40m interferometer. This map will take the positions of N randomly placed seismic sensors as well as the signals measured by each one of them and the calculated cross correlations between the sensors and between the sensors and the test mass of interest to give out a displacement vector with new sensor positions that are close to optimum for better seismic (and Newtonian) noise cancellation.

Now, I believe that much of the mathematical details have been already work out by Jenne in her thesis. She explains that the quantity of interest that we wish to minimize in order to find an optimal array is the following,

R = \sqrt{1-\frac{\vec{C}_{SN}^T C_{SS}^{-1}\vec{C}_{SN} }{C_{NN}}}

where  \vec{C}_{SN} is the cross-correlation vector between the seismic detectors and the seismic (or Newtonian) noise, C_{SS} is the cross-correlation matrix between the sensors and C_{NN} is the seismic (or Newtonian) noise variance. 

I looked at the paper that Jenne cited from which she obtained the above quantity and noted that it is a bit different as it contains an extra term inside the square root, it is given by

R' = \sqrt{1-\frac{\vec{C}_{SN}^T (C_{SS}^{-1}+C_{\Sigma\Sigma})\vec{C}_{SN} }{C_{NN}}}

where the new term, C_{\Sigma\Sigma} is the matrix describing the self noise of the sensors. I think Jenne set this term to zero since we can always perform a huddle test on our detectors and know the self noise, thus effectively subtracting it from the signals of interest that we use to calculate the other cross correlation quantities.

Anyways, the quantity R above is a function of the positions of the sensors. In order to apply it to our situation, I'm planning on:

     1) Performing the huddle tests on our sensors, redoing it for the accelerometers and then the seismometers (once the data aquisition system is working... )  

     2) Randomly (well not randomly, there are some assumptions we can make as to what might work best in terms of sensor placement) place the sensors around the interferometer. I'm planning on using all six Wilcoxon 731A accelerometers, the two Guralps and the STS seismometer (any more?).

     3) Measure the ground signals and use wiener filtering in order to cancel out their self noises.

     4) From the measured signals and their present positions we should be able to figure out where to move the sensors in order to optimize subtraction.

i have also been messing around with Jenne's code on seismic field simulations with the hopes of simulating a version of the seismic field around the 40m in order to understand the NN of the site a little better... maybe. While the data aquisition gets back to a working state, I'm planning on using my simulated NN curve as a way to play around with sensor optimization before its done experimentally.

i have as well been thinking and learning a little bit about source characterization through machine learning methods, specially using neural networks as Masha did back in her SURF project on 2012. I have also been looking at Support vector machines. The reasons why I have been looking at machine learning algorithms is because of the nature of the everchanging seismic field around the interferometer. Suppose we find a pretty good sensor array that we like. How do we make sure that this array is any good at some time t after it has been found? If the array mostly deals with the usual seismic background (quiet) of the site of interest, we could incorporate machine learning techniques in order to mitigate any of the more random disturbances that happen around the sites, like delivery trucks, earthquakes, etc.

  8987   Thu Aug 8 18:43:12 2013 SujanSummaryPEMOptimally subtracting signals from two seismometers.

An exercise of optimally subtracting one seismometer signal by another using weiner filters was done. Results have been summarized document attached.

Attachment 1: Results.pdf
Results.pdf
  16965   Thu Jun 30 18:06:22 2022 PacoUpdateALSOptimum ALS recovery - part I

[Paco]

In the morning I took some time to align the AUX beams in the XEND table. Later in the afternoon, I did the same on the YEND table. I then locked the AUX beams to the arm cavities while they were stabilized using POX/POY and turned off the PSL hepa off temporarily (this should be turned on after today's work).

After checking the the temperature slider sign on the spectrum analyzer of the control room I took some out-of-loop measurements of both ALS beatnotes (Attachment #1) by running diaggui /users/Templates/ALS/ALS_outOfLoop_Ref_DQ.xml and by comparing them against their old references (red vs magenta and blue vs cyan); it seems that YAUX is not doing too bad, but XAUX has increased residual noise around and above 100 Hz; perhaps as a result of the ongoing ALS SURF loop investigations? It does look like the OLTF UGF has dropped by half from ~ 11 kHz to ~ 5.5 kHz.

Anyways let this be a reference measurement for current locking tasks, as well as for ongoing SURF projects.

Attachment 1: als_ool_06_2022.png
als_ool_06_2022.png
  16154   Sun May 23 18:28:54 2021 JonUpdateCDSOpto-isolator for c1auxey

The new HAM-A coil drivers have a single DB9 connector for all the binary inputs. This requires that the dewhitening switching signals from the fast system be spliced with the coil enable signals from c1auxey. There is a common return for all the binary inputs. To avoid directly connecting the grounds of the two systems, I have looked for a suitable opto-isolator for the c1auxey signals.

I best option I found is the Ocean Controls KTD-258, a 4-channel, DIN-rail-mounted opto-isolator supporting input/output voltages of up to 30 V DC. It is an active device and can be powered using the same 15 V supply as is currently powering both the Acromags and excitation. I ordered one unit to be trialed in c1auxey. If this is found to be good solution, we will order more for the upgrades of c1auxex and c1susaux, as required for compatibility with the new suspension electronics.

  16166   Fri May 28 10:54:59 2021 JonUpdateCDSOpto-isolator for c1auxey

I have received the opto-isolator needed to complete the new c1auxey system. I left it sitting on the electronics bench next to the Acromag chassis.

Here is the manufacturer's wiring manual. It should be wired to the +15V chassis power and to the common return from the coil driver, following the instructions herein for NPN-style signals. Note that there are two sets of DIP switches (one on the input side and one on the output side) for selecting the mode of operation. These should all be set to "NPN" mode.

Attachment 1: optoisolator.jpeg
optoisolator.jpeg
  16178   Thu Jun 3 17:15:17 2021 YehonathanUpdateCDSOpto-isolator for c1auxey

As Jon wrote we need to use the NPN configuration (see attachments). I tested the isolator channels in the following way:

1. I connected +15V from the power supply to the input(+) contact.

2. Signal wire from one of the digital outputs was connected to I1-4

3. When I set the digital output to HIGH, the LED on the isolator turns on.

4. I measure the resistance between O1-4 to output(-) and find it to be ~ 100ohm in the HIGH state and an open circuit in the LOW state, as expected from an open collector output.

Unlike the Acromag output, the isolator output is not pulled up in the LOW state. To do so we need to connect +15V to the output channel through a pull-up resistor. For now, I leave it with no pull-up. According to the schematics of the HAM-A Coil Driver, the digital output channels drive an electromagnetic relay (I think) so it might not need to be pulled up to switch back. I'm not sure. We will need to check the operation of these outputs at the installation.

During the testing of the isolator outputs pull-up, I accidentally ran a high current through O2, frying it dead. It is now permanently shorted to the + and - outputs rendering it unusable. In any case, we need another isolator since we have 5 channels we need to isolate.

I mounted the isolator on the DIN rail and started wiring the digital outputs into it. I connected the GND from the RTS to output(-) such that when the digital outputs are HIGH the channels in the coil driver will be sunk into the RTS GND and not the slow one avoiding GND contamination.

Attachment 1: Optical_Isolator_NPN_Input.png
Optical_Isolator_NPN_Input.png
Attachment 2: Optical_Isolator_NPN_Output.png
Optical_Isolator_NPN_Output.png
  16181   Thu Jun 3 22:08:00 2021 KojiUpdateCDSOpto-isolator for c1auxey

- Could you explain what is the blue thing in Attachment 1?

- To check the validity of the signal chain, can you make a diagram summarizing the path from the fast BO - BO I/F - Acromag - This opto-isolator - the coil driver relay? (Cut-and-paste of the existing schematics is fine)

 

  16182   Fri Jun 4 14:49:23 2021 YehonathanUpdateCDSOpto-isolator for c1auxey

I made a diagram (Attached). I think it explains the blue thing in the previous post.

I don't know what is the grounding situation in the RTS so I put a ground in both the coil driver and the RTS. Hopefully, only one of them is connected in reality.

Quote:

- Could you explain what is the blue thing in Attachment 1?

- To check the validity of the signal chain, can you make a diagram summarizing the path from the fast BO - BO I/F - Acromag - This opto-isolator - the coil driver relay? (Cut-and-paste of the existing schematics is fine)

 

 

Attachment 1: Optical_isolator_Wiring.pdf
Optical_isolator_Wiring.pdf
  16183   Fri Jun 4 17:46:25 2021 unYehonathanUpdateCDSOpto-isolator for c1auxey

I mounted the optoisolator on the DIN rail and connected the 3 first channels

C1:SUS-ETMY_UL_ENABLE
C1:SUS-ETMY_UR_ENABLE

C1:SUS-ETMY_LL_ENABLE

to the optoisolator inputs 1,3,4 respectively. I connected the +15V input voltage into the input(+) of the optoisolator.

The outputs were connected to DB9F-2 where those channels were connected before.

I added DB9F-1 to the front panel to accept channels from the RTS. I connected the fast channels to connectors 1,2,3 from DB9F-1 to DB9F-2 according to the wiring diagram. The GND from DB9F-1 was connected to both connector 5 of DB9F-2 and the output (-).

I tested the channels: I connected a DB9 breakout board to DB9F-2. I measured the resistance between the RTS GND and the isolated channels while switching them on and off. In the beginning, when I turned on the binary channels the resistance was behaving weird - oscillating between low resistance and open circuit. I pulled up the channels through a 100Kohm resistor to observe whether the voltage behavior is reasonable or not. Indeed I observed that in the LOW state the voltage between the isolated channel and slow GND is 15V and 0.03V in the HIGH state. Then I disconnected the pull up from the channels and measured the resistance again. It showed ~ stable 170ohm in the HIGH state and an open circuit in the LOW state. I was not able to reproduce the weird initial behavior. Maybe the optoisolator needs some warmup of some sort.

 

We still need to wire the rest of the fast channels to DBF9-3 and isolate the channels in DBF9-4. For that, we need another optoisolator.

 

There is still an open issue with the BI channels not read by EPICS. They can still be read by the Windows machine though.

Attachment 1: 20210604_173420.jpg
20210604_173420.jpg
  16184   Sun Jun 6 03:02:14 2021 KojiUpdateCDSOpto-isolator for c1auxey

This RTS also use the BO interface with an opto isolator. https://dcc.ligo.org/LIGO-D1002593

Could you also include the pull up/pull down situations?

  16186   Sun Jun 6 12:15:16 2021 JonUpdateCDSOpto-isolator for c1auxey

Since this Ocean Controls optoisolator has been shown to be compatible, I've gone ahead and ordered 10 more:

  • (1) to complete c1auxey
  • (2) for the upgrade of c1auxex
  • (7) for the upgrade of c1susaux

They are expected to arrive by Wednesday.

  16187   Sun Jun 6 15:59:51 2021 YehonathanUpdateCDSOpto-isolator for c1auxey

According to the BO interface circuit board https://dcc.ligo.org/D1001266, PCIN wires are connected to the coil driver and they are not pulled either way.

That means that they're either grounded or floating. I updated the drawing.

Quote:

This RTS also use the BO interface with an opto isolator. https://dcc.ligo.org/LIGO-D1002593

Could you also include the pull up/pull down situations?

 

Attachment 1: Optical_isolator_Wiring.pdf
Optical_isolator_Wiring.pdf
  16199   Mon Jun 14 15:31:30 2021 YehonathanUpdateCDSOpto-isolator for c1auxey

I checked the BI situation on the HAM-A coil driver. It seems like these are sinking BIs and indeed need to be isolated from the Acromag unit GND to avoid contamination.

The BIs will have to be isolated on a different isolator. Now, the wires coming from the field (red) are connected to the second isolator's input and the outputs are connected to the Acromag BI module and the Acromag's RTN.

I updated the wiring diagram (attached) and the wiring spreadsheet.

In the diagram, you can notice that the BI isolator (the right one) is powered by the Acromag's +15V and switched when the coil driver's GND is supplied. I am not sure if it makes sense or not. In this configuration, there is a path between the coil driver's GND and the Acromag's GND but its resistance is at least 10KOhm. The extra careful option is to power the isolator by the coil driver's +V but there is no +V on any of the connectors going out of the coil driver.

I installed an additional isolator on the DIN rail and wired the remaining BOs (C1:SUS-ETMY_SD_ENABLE, C1:SUS-ETMY_LR_ENABLE) through it to the DB9F-4 feedthrough. I also added DB9F-3 for incoming wires from the RTS and made the required connection from it to DB9F-4.

I tested the new isolated BOs using the Windows machine (after stopping Modbus). As before, I measure the resistance between pin 5 (coil driver GND) and the channel under test. When I turn on the BO I see the resistance drops from inf to 166ohm and back to inf when I turn it off. Both channels passed the test.

 

Attachment 1: Optical_isolator_Wiring.pdf
Optical_isolator_Wiring.pdf
  16203   Tue Jun 15 21:48:55 2021 KojiUpdateCDSOpto-isolator for c1auxey

If my understanding is correct, the (photo receiving) NPN transistor of the optocoupler is energized through the acromag. The LED side should be driven by the coil driver circuit. It is properly done for the "enable mon" through 750Ohm and +V. However, "Run/Acquire" is a relay switch and there is no one to drive the line. I propose to add the pull-up network to the run/acquire outputs. This way all 8 outputs become identical and symmetric.

We should test the configuration if this works properly. This can be done with just a manual switch, R=750Ohm, and a +V supply  (+18V I guess).

Attachment 1: Acromag_RTS_BI_config.jpg
Acromag_RTS_BI_config.jpg
  16205   Wed Jun 16 17:24:29 2021 YehonathanUpdateCDSOpto-isolator for c1auxey

I updated the wiring diagram according to Koji's suggestion. According to the isolator manual, this configuration requires that the isolator input be configured as PNP.

Additionally, when the switch in the coil driver is open the LED in the isolator is signaling an on-state. Therefore, we might need to configure the Acromag to invert the input.

There are the Run/Aquire channels that we might need to add to the wiring diagram. If we do need to read them using slow channels, we will have to pull them up like the EnableMon channels to use them like in the wiring diagram.

Attachment 1: Optical_isolator_Wiring.pdf
Optical_isolator_Wiring.pdf
  16207   Wed Jun 16 20:32:39 2021 YehonathanUpdateCDSOpto-isolator for c1auxey

I installed 2 additional isolators in the Acromag chassis. I set all the input channels to PNP. I ran the digital inputs (EnableMon channels) through these isolators according to the previous post.

I tested the digital inputs in the following way:

I connected an 18V voltage source to the signal wire under test through a 1Kohm resistor. I connected the GND of the voltage source to the RTN wire of the feedthrough. When the voltage source was connected, the LED on the isolator turned on and the EPICs channel under test was Enabled. When I disconnected the voltage source or shorted the signal wire to GND the LED on the isolator turned off and the EPICs channel showed a Disabled state.

  16243   Fri Jul 9 18:35:32 2021 YehonathanUpdateCDSOpto-isolator for c1auxey

Following Koji's channel list review, we made changes to the wiring spreadsheet.

Today, I made the changes real in the Acromag chassis. I went through the channel list one by one and made sure it is wired correctly. Additionally, since we now need all the channels the existing isolators have, I replaced the isolator with the defective channel with a new one.

The things to do next:

1. Create entries for the spare coil driver and satellite box channels in the EPICs DB.

2. Test the spare channels.

  16244   Mon Jul 12 18:06:25 2021 YehonathanUpdateCDSOpto-isolator for c1auxey

I edited /cvs/cds/caltech/target/c1auxey1/ETMYaux.db (after creating a backup) and added the spare coil driver channels.

I tested those channels using caget while fixing wiring issues. The tests were all succesful. The digital output channel were tested using the Windows machine since they are locked by some EPICs mechanism I don't yet understand.

One worrying point is I found that the differential analog inputs to be unstable unless I connected a reference to some stable voltage source unlike previous tests showed. It was unstable (but less) even when I connected the ref to the ground connectors on the power supplies on the workbench. This is really puzzling.

When I say unstable I mean that most of the time the voltage reading shows the right value, but occasionly there is a transient sharp volage drop of the order of 0.5V. I will do a more quantitative analysis tomorrow.

 

ELOG V3.1.3-