I gave some of the data analysts a look around because they asked and nothing was currently going on in the 40m. Nothing was changed.

[Jenne, EricQ, Rana]

Tonight we started prepping for an attempt at variable finesse locking. 

The idea is to put in a MICH offset and hold the lock with ASDC/POPDC (so that the offset can be larger than if we were just using RF signals).  This reduces the PRC buildup, which reduces / removes the double cavity resonance problems while reducing the CARM offset. 

• So.  Today, I pulled out the POP22 razor blade so that we can use the Thorlabs PD as POPDC, without the yaw coupling.  Our other option is to use the POP QPD SUM, but that would require some model changes and more importantly it's not a particularly low noise readout path.

• We re-set the analog whitening gains for ASDC and POPDC.
  • For ASDC, we want the half-fringe in the PRMI case to be not saturating.  We chose 18dB (it had been the default 0dB).
  • For POPDC, Rana and I saw that it was saturating all the time with the 33dB that it had when the carrier became resonant.  This was never really a problem in the past, but if we use it for normalization, we get glitches that knock us out of lock every time POPDC saturated.  So, now POPDC is at 0dB.  It still occasionally saturates when the PRMI is flashing, but we can't get lower than 0dB without going and putting an ND filter on the PD.
• We turned off the analog whitening filters and digital unwhitening for both ASDC and POPDC.  We can consider turning them back on later after we have acquired lock if we need them, but we need them off for acquisition.
• Locked MICH with ASDC/POPDC.  Good.  Stays locked even if PRM is flashing.
• Locked PRMI with PRCL on REFL33I and MICH on ASDC/POPDC.
• Locked arms, held off resonance with ALS, lock MICH with ASDC/POPDC. 
• Failed to lock PRMI with arms held off resonance, using the new scheme (no transition, trying to directly acquire)
• Locked PRMI on REFL33 I&Q with the arms held off resonance, and tried to transition MICH over to ASDC/POPDC, failed.
• Confusion about the relative phase between REFL33Q and ASDC.  It looks like it is ~45deg at 100 Hz, or ~90 deg at 375 Hz.  Why isn't it 0 or 180?
• Went back to PRMI-only, tried to map out fringe by changing MICH offset (tried while MICH was on both REFL33 and ASDC/POPDC).  Not really sure where we are on the fringe.

MICH locked on ASDC normalized by POPDC, PRM and ETMs (and SRM) all misaligned.

MICH offset of -20

MICH input = -0.04*ASDC normalized by 0.1*POPDC.

MICH gain = +5

MICH always triggered on (no triggering for DoF), but FM8 (CLP400) triggered to come on after lock (didn't write down the values).

PRMI locked with MICH on ASDC normalized by POPDC, PRCL on REFL33I, ETMs and SRM misaligned.

MICH offset of -10

MICH input = -0.04*ASDC normalized by 0.1*POPDC.

PRCL input = 1*REFL33I

MICH gain = +5

PRCL gain = -0.4 (factor ten times the regular value)

MICH always on, PRCL triggered on POP22.  MICH FM8 and PRCL FM1,2,6,9 triggered on.

Gives POPDC of about 20 counts, POP22 of about 12 counts, ASDC of about 500 counts.

Arms held at 3nm, MICH locked on ASDC/POPDC, PRM and SRM misaligned.

MICH offset of -10

MICH input = -0.04*ASDC normalized by 0.1*POPDC.

MICH gain = +5

MICH always on, PRCL triggered on POP22.  MICH FM8 and PRCL FM1,2,6,9 triggered on.

Arms held at 3nm, attempt at PRMI lock with MICH on ASDC/POPDC.

Failed.  Tried mostly same MICH gains as arms+mich, and PRCL at 10* normal gain.

Arms held at 3nm, PRMI locked with REFL 33 I&Q, attempt at transition to MICH on ASDC/POPDC.

Failed.  At first, I was putting in the TF line at ~375Hz, but we looked at the full transfer function between 100Hz and 1kHz, and there was a weird dip near 300Hz from PRCL-MICH loop coupling.  Here we were seeing that the phase between REFL33Q and ASDC was ~90 degrees.  What?

Tried putting the TF line at ~100 Hz (since MICH UGF is in the few tens of Hz anyway, so 100 is still above that), but still get weird relative phase.  Here it seems to be about 45 degrees when I inject a single line, although it didn't seem like a weird phase when we did the full swept sine earlier.  Maybe I was just not doing something right at that point??

Anyhow, no matter what values I tried to put into the input matrix (starting with REFL33I&Q, trying to get MICH to ASDC/POPDC), I kept losing lock.  This included trying to ramp up the MICH offset simultaneously with the matrix changing, which was meant to help with the PRCL gain change.  Q has since given us MICH and PRCL UGF servos.

Tomorrow:

• Why is there some weirdo phase between REFL33Q and ASDC at 100Hz?  Was I just being a spaz?
• With PRMI-only, figure out how to transition from REFL33 I&Q over to MICH on ASDC/POPDC.
• Then hold the arms off resonance, and do the same transition.  (First make sure we're at a good place on the fringe)
• Lower the CARM and DARM offsets, transition them to RF, engage CARM AO path.
• Reduce MICH offset, transition to RF.
• Celebrate (maybe).

Koji asked aloud tonight if we could measure the coating thermal noise of the refcav optics by beating the refcav light with the MC_TRANS light. Then we looked at our calculations for the noises:

Displacement noise of T=200ppm silica/tantala coating on a 1" silica substrate with a 300 micron beam spot = 1e-18 * sqrt(100 Hz / f) m/rHz.

Displacement noise from coating thermal in the MC is roughly smaller by the beam size ratio (1.8 mm / 0.3 mm). Some differences due to 3 mirrors and more layers on MC2 than the others, but those are small factors.

So, the frequency noise from the refcav should by larger than the MC thermal noise by a total factor of (1.8 / 0.3) * (13 m / 8 inches) ~ 400.

Another way to say it is that the effective strain noise in the RC is (1e-18 / 0.200) = 5e-18 /rHz. This translates into (5e-18 * 13) = 6.5e-17 m/rHz in the MC. (in frequency noise its 1.5 mHz/rHz).

I have measured the frequency noise in the LLO MC to be at this level back in 2009, so it seems possible to use our RC + MC to measure coating thermal noise by the length amplification factor and compete with Frank+Tara.

So today we set up the Jenny RC temperature setup to lock the LWE NPRO to the RC and then set up the beat note with the IFO REFL beam on the AS table. By using the 2 laser beat, we are avoiding the VCO phase noise issue which used to limit the PSL frequency noise at ~0.01 Hz/rHz. To do this we have reworked some of the optics on the PSL and AS tables, but I think its been done without disturbing the beams for the regular locking. Beat note has been found, but the NPRO has still not been locked to the RC - next we setup the lockin amp, dither the PZT, and then use the New Focus lock box to lock it to the RC.

You might think that its hard to measure this since the MC has ~1 MHz frequency fluctuations and we want to measure down to 1e-4 Hz. But, in fact, we can just use a 200 m MFD with a LT1128 preamp. Then we use the MFD to stabilize the MC length to the refcav and just use the control + error signal of the MFD setup as the coating thermal noise measurement.

Note: Beat found at ~40deg for the aux laser. The aux laser is on but the shutter is closed.
The AS camera seems to be hosed. Need a bit of alignment. (KA) ==> Fixed. (Jan 15)

- Sat amp mod and test: on going (Tega)
- Coil driver mod and test: on going (Tega)

- Acromag: almost ready (Yehonathan)

- IDC10-DB9 cable / D2100641 / IDC10F for ribbon in hand / Dsub9M ribbon brought from Downs / QTY 2 for two ends -> Made 2 (stored in the DSUB connector plastic box)
- IDC40-DB9 cable / D2100640 / IDC40F for ribbon in hand / DB9F solder brought from Downs  / QTY 4 for two ends -> Made 4 0.5m cables (stored in the DSUB connector plastic box)

- DB15-DB9 reducer cable / ETMX2+ETMY2+VERTEX16+NewSOS14 = 34 / to be ordered

- End DAC signal adapter with Dewhitening (with DIFF/SE converter) / to be designed & built
- End ADC adapter (with SE/DIFF converter) / to be designed & built

MISC Ordering

• 3.5 x Sat Amp Adapter made (order more DSUB25 conns)
  • -> Gave 2 to Tega, 1.5 in the DSUB box
  • 5747842-4 A32100-ND -> ‎5747842-3‎ A32099-ND‎ Qty40
  • 5747846-3 A32125-ND -> ‎747846-3‎ A23311-ND‎ Qty40
• Tega's sat amp components
  • 499Ω P499BCCT-ND 78 -> Backorder -> ‎RG32P499BCT-ND‎ Qty 100
  • 4.99KΩ TNPW12064K99BEEA 56 -> Qty 100
  • 75Ω YAG5096CT-ND 180 -> Qty 200
  • 1.82KΩ P18391CT-ND 103 -> Qty 120
  • 68 nF P10965-ND 209
• Order more DB9s for Tega's sat amp adapter 4 units (look at the AA IO BOM) 
  • 4x 8x 5747840-4 DB9M PCB A32092-ND -> 6-747840-9‎ A123182-ND‎ Qty 35
  • 4x 5x 5747844-4 A32117-ND -> Qty 25
  • 4x 5x DB9M ribbon MMR09K-ND -> 8209-8000‎ 8209-8000-ND‎ Qty 25
  • 4x 5x 5746861-4 DB9F ribbon 5746861-4-ND -> 400F0-09-1-00 ‎LFR09H-ND‎ Qty 35
• Order 18bit DAC AI -> 16bit DAC AI components 4 units
  • 4x 4x 5747150-8 DSUB9F PCB A34072-ND -> ‎D09S24A4PX00LF‎609-6357-ND‎ Qty 20
  • 4x 1x 787082-7 CONN D-TYPE RCPT 68POS R/A SLDR (SCSI Female) A3321-ND -> ‎5787082-7‎ A31814-ND‎ Qty 5
  • 4x 1x 22-23-2021 Connector Header Through Hole 2 position 0.100" (2.54mm)    WM4200-ND -> Qty5

Ordered compoenents are in.

- Made 36 more Sat Amp internal boards (Attachment 1). Now we can install the adapters to all the 19 sat amp units.

- Gave Tega the components for the sat amp adapter units. (Attachment 2)

- Gave Tega the componennts for the sat amp / coil driver modifications.

- Made 5 PCBs for the 16bit DAC AI rear panel interface (Attachment 3)

= BHD Platform assembly on the staging table =

• [Done] The assembly will be (mostly) done by the end of Thu (JC)
• [Done] OMC is going to be mounted on Fri (KA/JC)
   
• After the vent, we will bring out the BHD optic from the ITMY chamber.
   
• We'll continue to work on the BHD platform alignment on the staging table
  with the optics/optic mounts taken out from the chamber.
  + the OFI components (incl. the machines posts)
   
• Asking Dean for the mighty mouse connectors for the devices
  • -> Asked. We need the connectors and pins. Dean is working on the procurement.

= OMC mounting / locking =

• [Done] Bring the OMC#1 from the OMC lab (KA, Thu afternoon)
• [Done] Attach the kinematic mounting brackets on the OMC. 
• Blank OMC breadboard for counterweighting (KA, bring from the OMC lab) -> Brought
   
• Locking electronics 
  • [Done] Paco prepared:
    Moku, PDA10 (150MHz), HV Amp for Laser or OMC PZT
     
  • Prepare locking optics (steering mirrors, post, etc)
     
• OMC DCPD prep
  • [Done] Bring the DCPDs (Excelitas C30655) from the OMC lab
  • Remove the cap of the diodes (Asked Dean about the tool)
  • DCPD installation on the OMCs

= IFO work until the vent =

• [Done] X arm ASS repair (Radhika)
• FPMI / PRMI locking
  • BS is moving a lot -> fix

= Vent Prep =

• [Done] Watchdog implementation on all the optics
• Clipping investigation

= Vent =

• Table tilt check (digital tilt meter)
   
• Open ITMY:
  • pick up components for BHD platform
  • Turn SRM
  • BHD platform installation
  • Counter weight adjustment
     
• Open ITMX:
  • PR2 sus optic swap -> optic thickness 3/8" -> 1/2", needs adjustment
• Open BS / INJ
  • Clipping check
     
• Vacuum maintenance
  • Remove TP1 for maintenance
  • TP2 communication error problem

[Jenne, Mirko]

1. We should help the OAF by compensating for the actuator TF:

The actuator TF, from adaptive filter output to MC2, through PD, mixer, Pentek and into C1:IOO looks like this:

If we assume a white-ish error signal that the adaptive code tries to compensate for its job gets extra complicated because it has to invert this TF. So we really should compensate for that. Easiest place for that is the CORR filter directly behind the adaptive code block.

Using the TF measurement from above I used the vectfit (" /cvs/cds/caltech/apps/mDV/extra/firfit_forFotonMirkoComplex.m" ) to get fit a corresponding digital filter:

If we invert swap the zeros and poles in the digital filter we get the inverted TF.
(Todo: Figure out how to invert the TF. Just switching the poles and zeros doesn't work).

2. Wiener filtering

The idea was to use the adaptive filtering only for small corrections to the wiener filtering. So we really should try to get the wiener filtering going.

Howto:

1. Get data for STS1X and GUR1X and MC_F in matlab. E.g. via ligodv
2. Check the MC was in lock the entire time.
3, Filter MC_F with the actuator TF, so the wiener filter knows about that and compensates for it
4. Calculate the wiener filter " h1winolevLigoDV.m "
5. Export the data to the workspace. It is also saved to the disc as "h1filtcoeffTS.mat". Make sure there are first the witnesses, then MC_F
6. Execute " /cvs/cds/caltech/apps/mDV/extras/LHO/firfit_for_FotonMirko.m" while one directory higher. 
7. Copy the digital filter in SOS form that is printed into the matlab command line and put it into the corresponding filter in the OAF model via foton.

With data from 11-11-15 04:00 to 05:45. Sampling freq. 256Hz. 8000 Taps => length = 30.2s. Prefiltered to notch the 60Hz line in MC_F, but not compensation the actuator TF. This results in the following wiener filter and corresponding SOS filter to be copied into foton.
STS1X:

GUR1X:

[alex, gautam]

Alex is going to have an undergrad work on a calibration optimization project on the 40m RTCDS system. For this purpose, we wanted to setup a "Simulated DARM loop". Today, Alex and I set this up. I figured we can use the c1tst model for this purpose. We basically copied the topology from Figure 2 of the h(t) paper. Attached are screenshots of the MEDM screens of the system we setup, and the simulink block diagram - the main screen can be accessed from the "SIM PLANT" tab in the sitemp.

It remains to setup the appropriate filters in the filter banks, and an EPICS channel monitor for monitoring the single excitation testpoint in the model. We also did not set up any DQ channels for the time being, as it is not even clear to me what channels need to be DQ-ed.

Went through all of Pooja's elog posts, her report and am currently cleaning up her code and working on setting up the simulations of spot motion from her work last year. I've also just begun to look at some material sent by Gautam on resonators.

This week, I plan to do the following:

1) Review Gabriele's CNN work for beam spot tracking and get his code running.

2) Since the relation between the angular motion of the optic and beam spot motion can be determined theoretically, I think a neural network is not mandatory for the tracking of beam spot motion. I strongly believe that a more traditional approach such as thresholding, followed by a hough transform ought to do the trick as the contours of the beam spot are circles. I did try a quick and dirty implementation today using opencv and ran into the problem of no detection or detection of spurious circles (the number of which decreased with the increased application of median blur). I will defer a more careful analysis of this until step (1) is done as Gautam has advised.

3) Clean up Pooja's code on beam tracking and obtain the simulated data.

4) Also data like this  (https://drive.google.com/file/d/1VbXcPTfC9GH2ttZNWM7Lg0RqD7qiCZuA/view) is incredibly noisy. I will look up some standard techniques for cleaning such data though I'm not sure if the impact of that can be measured until I figure out an algorithm to track the beam spot.

A more interesting question Gautam raised was the validity of using the beam spot motion for detection of angular motion in the presence of other factors such as surface irregularities. Another question is the relevance of using the beam spot motion when the oplevs are already in place. It is not immediately obvious to me how I can ascertain this and I will put more thought into this.

1. I removed the flip-mount that was installed on the EY in-air table for the mode-spectroscopy project (see Attachment #1). The Transmon QPD at EY sees IR light again.
2. Dark noise checkout - see Attachment #2.
3. Light-level expectations:
   • For the current config, let's say 0.8 W reaches the PRM, and we will have a PRG of 50. 
   • This implies ~5.5 kW circulating power in the arms.
   • This implies ~70mW will get transmitted through the ETM, of which at most half makes it to the QPD. 
   • In the nominal operating condition, we expect more like 6 W circulating in the arm cavity. So something like 30uW is expected to make it out onto the Trans QPDs.
   • But in this condition, we expect to run with the high-gain Thorlabs PD.
   • In reality the number is likely to be somewhat smaller. But we should set the transimpedance gain of this photodiode accordingly. Currently, there are a bunch of ND filters installed on this photodiode, which probably should be removed.
4. Angular control
   • The other purpose these QPDs are expected to serve is to stabilize the angular motion of the cavities when locked with high circulating power.
   • Need to calculate what the sensing noise requirement is.

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

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

In continuation to my previous posts, I have been working on evaluating the data on transfer function. Recently, I have calculated the correlation values between the real and imaginary part of the transfer function. Also I have written the code for plotting the transfer function data stream at each frequency in the argand plane just for referring to. Also I have done a few calculations and found the errors in magnitude and phase using those in the real and imaginary parts of the transfer function. More details for the process are in this git repository.

The following attachments have been added:

1. The correlation plot at different frequencies. This data is for a 100 data files.
2. The Test files used to produce the abover plot along with the code for the plotting it as well as the text file containing the correlation values. (Most of the code is commented as that part wasn't needed fo rhte recent changes.)

Conclusion:

Seeing the correlation values, it sounds reasonable that the gaussian in real and imaginary parts approximation is actually holding. This is because the correlation values are mostly quite small. This can be seen by studying the distribution of the transfer function on the argand plane. The entire distribution can be seen to be somewhat, if not entirely, circular. Even when the ellipticity of the curve seems to be high, the curve still appears to be elliptical along the real and imaginary axes, i.e., correlation in them is still low.

To Do:

1. Use a better way to estimate the errors in magnitude and phase as the method used right now is a only valid with the liner approximation and gives insane values which are totally out of bounds when the magnitude is extrmely small and the phase is varying as mad.
2. Use the errors in the transfer function to estimate the coherence in the data for each frequency point. That is basically plot a cohernece Vs frequency plot showing how the coherence of the measurements vary as the frequency is varied.

In order to test the above again, with an even larger data set, I am leaving a script running on Ottavia. It should take more than just the night(I estimate around 10-11 hours) if there are no problems.

Summary

• Alex, Anchal, and I measure the open-loop transfer function for WFS and MC2_TRANS signal.
• We utilize Fourier transform of appropriately filtered Gaussian noise to obtain the transfer function.
• With appropriate frequency-dependant noise and appropriate overall gain, the transfer function at lower frequency around 1 Hz can be roughly measured in shorter time and with a narrower resolution than those of the swept sine.

Purpose

The purpose is to roughly measure the open-loop transfer function in shorter time and with a narrower resolution. The transfer function can usually be obtained the following process. We measure two points before (IN1) and after (IN2) the excitation signal injection point. We can get the transfer function by dividing IN1 signal by IN2 signal. However, this method has some difficulties: longer time to finish one measurement in lower frequency and less measuring points. These are because the frequency of excitation signal is fixed for every measuring point. The ordinary method is not suitable for rough measurement. Therefore, we try to utilize frequency-dependant noise for measuring the transfer function (Rana teaches us the method).

Method

We utilize the Gaussian noise instead of the fixed sine wave. We inject the noise, which is properly filtered, into the exciting point (such as C1:IOO-MC2_TRANS_YAW_EXC in C1IOO_WFS_MASTER window), and measure two signals in the points IN1 and IN2. The two signals are Fourier transformed. And we obtain the transfer function by dividing the transformed signal IN1 by that of IN2.

To get good SNR, the frequency dependence of the injecting noise signal is important. We use the awggui command to create the appropriately filtered noise. We decide the dependence from the coherence between the IN1 signal and the excitation signal. The coherence around 1 shows the good SNR. So the dependence is adjusted so that the coherence approaches 1 in the observation frequency range. Attachment 1 shows the frequency dependence of the filter. We cut the gain below 0.1 Hz and above 10 Hz to limit frequency range, and use Zero-Pole gain to treat the influence of the mirrors' suspension in the frequency range. The filter we used is 

• cheby1("BandPass", 6, 2, 0.1, 10)
• zpk([3], [0.3], 1, "n")
• zpk([0.375 + i*0.649519; 0.375 - i*0.649519], [0.75; 2.5 + i*14.7902; 2.5 - i*14.7902], 1, "n")gain(4.46889)
• zpk([13], [3], 1, "n")gain(1.05099)

The file is saved in /users/Templates/MC/wfsTFs/WFS_noise_injection_profile-230302, but the saved file loses some filter information... So we write all the filters above.

Note: The noise filter has a ripple around the cutoff frequency. It comes from cheby1. Chebyshev Type 1 filter can drop the gain rapidly but has the ripple around the cutoff frequency.

Longer averaging time is also important to get the better SNR. The time is estimated from the resolution frequency and overwrap of the time-series data. We set the resolution as 0.01 Hz and the overwrap as 50 %, so the 10 times averaging takes about 8 minutes. In contrast, it takes about 2 hours if we measure 10 cycles of sine wave for every frequency with the ordinary transfer function measurement. The method of using the noise signal can inject multiple frequencies simultaneously into the excitation points, and can reduce the total measuring time.

We use the diaggui command for measuring the transfer function. Fourier Tools in Measurement tab translates the time-series signals, and the transfer function is obtained by Graph, Transfer function, in Result tab. Fig 2 is an example. The settings are saved, for example, in /users/Templates/MC/wfsTFs/MC2-TRANS_YAW_230302.xml.

In every measurement, we inject the noise into every excitation point of WFS1, 2 and MC2_TRANS, and PIT and YAW, and take every transfer function. We change overall gain of the filter in every measurement. The values are listed as follows.

Note: The gain of the transfer function is changed from 0.7 to 21 in the WFS1_PIT case only. The value of the case is much bigger than other measurements. After the experiment, the gain is put back.

Result

We show some results (YAW of WFS1, 2, and MC2_TRANS) as an example. The MC2_TRANS_YAW data only has structures around 3 Hz and 7 Hz shown in Attachment 2. The coherence of all measurements in the frequency range [0.1 Hz, 10 Hz] is around 1 except for the pendulum frequency of IMC mirrors. All the results have similar trend, which is low-pass like frequency dependence and has resonant of the pendulum. The trend is also obtained in the previous measurement using the ordinary method such as 40m/17486 and 40m/17472.

Discussion

Phase margin result for every measurement is listed. MC2_PIT data is 'N/A' because the transfer function does not exceed 0 dB at the observation frequency range. The phase margin values except for WFS1_PIT case are small, that is, the servos are nearly unstable. In WFS1_PIT, the phase margin is larger than other data because we increase the overall gain of the loop from 0.7 to 21 during measurement. This indicates the overall gain of the loop should be increased.

The pendulum resonance reduces the coherence. The coherence shows the signal relevance at the excitation point (input) and the measurement point (output). We can estimate whether the injecting signal is buried by background noise. The noise filter is not optimized yet, and we use the same filter for all the measurements. It causes the reduction of the coherence around the pendulum resonance. To increase the coherence and take better measurement, we have to optimize the frequency-dependance of the noise filter and increase averaging times for every measurement.

Only in the case of MC2_TRANS_YAW, the sudden gain changes exist around 3 Hz and 7 Hz. The sudden change is small peak at 3 Hz and large dip at 7 Hz. The result in 40m/5928 has a structure at 3 Hz, but we cannot find the structure at 7 Hz in the past entry... But both sudden changes do not make the loop unstable because the gain at the frequencies are smaller than 0 dB. We will check the detail and the origin.

In Future

• The overall open-loop gain should be increased.
• If necessary, we have to optimize the noise filter for every measurement.
• If necessary, we will check the detail and the origin of the sudden gain changes around 3 Hz and 7 Hz in MC2_TRANS_YAW.

that is great

I think we would like to set the WFS1 P/Y UGFs to be ~2-3 Hz, and the MC_TRANS loops to have a UGF of ~0.1 Hz.

Could you use your loop gain measurements to set the _GAIN values for those UGFs? I am curious to see if the system is stable with that control.

Summary

• Alex, Anchal, and I adjusted the every overall gain iin P/Y of WFS1, 2 and MC2_TRANS loop.
• We set the WFS1, 2 P/Y UGFs to be ~2-3 Hz, and the MC2_TRANS loops to have a UGF of ~0.1 Hz.

Method

From the previous results (40m/17489) and measuring the open-loop transfer function (OLTF) by broadband noise, we adjusted the overall gain in P/Y of WFS1, 2 and MC2_TRANS loop. The table represents the changed values.

We also note the overall gain of the injecting noise: WFS1_PIT 52345, WFS2_PIT 152345, MC2_TRANS_PIT 152345, WFS1_YAW 152345, WFS2_YAW 102345, and MC2_TRANS_YAW 102345. The values are used in the awggui window.

We measured the OLTF by the appropriately filtered noise. The filter we used is the same as that of the previous measurement.

Result

Attachment 1 shows the OLTF whose gain is adjusted.

does Anyone understand why the broadband noise injection is so bad around 1 Hz? we do not see this issue with swept sine. noise seems good at other frequencies.

Does it have anything to do with the time constant of the resonances?

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

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

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

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

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

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

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

Yesterday, I measured the transfer function of the YARM PDH box.

I tested the electronic board and couldn't find a frequency dependent behaviour. So I measured the TF again and it looked nice.

Today's nice measurement could is/was reproducible. I suppose yesterday's measurement is just an artefact.

The electronic board is modified according to Kiwamu's wiki entry http://blue.ligo-wa.caltech.edu:8000/40m/Electronics/PDH_Universal_Box

Btw. The light could be locked to the cavity for ~3min.

 I measured FSS's open loop transfer function.

For FSS servo schematic, see D040105-B.  

4395A's source out is connected to Test point 2 on the patch panel.

Test Point 2 is enabled by FSS medm screen.

"A" channel is connected to In1, on the patch panel.

"R" channel is connected to In2, on the patch panel.

the plot shows signal from A/R.

Note that the magnitude has not been corrected for the impedance match yet.

So the real UGF will be different from the plot.

-------------------------

4395A setup

-------------------------

network analyzer mode

frequency span 1k - 10MHz

Intermediate frequency bandwidth 100Hz

Attenuator: 0 for both channels

Source out power: -30 dBm

sweep log frequency

------------------------------

medm screen setup

-----------------------------

TP2: enabled

Common gain -4.8 dB

Fast Gain 16 dB

Using free-swinging Mode Cleaner OSEM data and Guralp seismometers, I have taken transfer functions of the Mode Cleaner stacks.

During this experiment, the MC was unlocked overnight, and one Guralp seismometer was underneath each chamber (MC1/MC3, and MC2).  Clara will let me know what the orientation of the seismometers were (including which seismometer was underneath which chamber and what direction the seismometer axes were pointing), but for now I have included TFs for every combination of suspension motion and seismometer channels.

I combined the 4 OSEM channels for each optic in POS and PIT, and then calibrated each of my sus channels using the method described in Kakeru's elog entry 1413. Units are meters for POS, and radians for PIT.  I also calibrated the guralp channels into meters.

The traces on each plot are: MC_{POS or PIT} / Guralp_{1 or 2}_{direction}.  So each plot shows the coupling between every seismometer direction and a single mirror direction.  The colors are the same for all the plots, ie the gold trace is always Gur1Z.

Looks like all of the accelerometers and seismometers have been disconnected since early AM last Monday when Clara disconnected them for her sensor noise measurement.

    ..
m * x  = (x_G - x) * k  + d(x_G - x) * b
                          dt

• m = mass
  
• x = displacement of the mass
  
• x_G = displacement of the ground
  
• k = spring constant
  
• b = damping constant
  

x               w0^2  +  i*w*w0/Q
----    =    -----------------------
x_G           w0^2 + i*w*w0/Q - w^2

• w0 = sqrt(k/m) = natural frequency of spring + mass
  
• w = frequency of ground motion
  
• Q = q-factor of spring + mass system = 1/2 for critically damped system
  

d  (x - x_G)          (    w0^2  +  i*w*w0/Q          )    .                    w^2               .
dt                 =  (  -----------------------  - 1 ) * x_G   =      ----------------------- * x_G
                      (   w0^2 + i*w*w0/Q - w^2       )                w0^2 + i*w*w0/Q - w^2

I  measured the transfer function of the new coil driver board. This was done to estimate the correct Sim-Dewhithinng and Anti-Dewhitening digital filters in the CDS. 

Attachment 1: Shows the setup used to measure the TF of the Coil driver board.
Attachment 2: Coil driver board replaced by a DB9 cable (Reference).
Attachment 3: The magnitude and phase response of the measured and simulated TF (Coil driver parameters mentioned here (D2100145) )

Update

Attachment 4: The magnitude and phase response of the simulated and measured TF for the two operating modes. (The coil driver has two modes of operation i.e. Run and Acuisition)

I estimated the transfer function of the seismic stacks using a rough model I made based on the LIGO document LIGO T000058 -00. I used a Q of 3.3 for the viton springs, and resonant frequencies of 2.3, 7.5, 15, and 22 Hz (measured in that document for the horizontal motion). I multiplied the simple mass-spring transfer function four times for each layer of metal/spring, with the respective resonant frequency for each. The pendulum suspending the test masses has a resonant frequency of 0.74 and a Q of 3, according to the same document.

When I multiply the net transfer function (pendulum included, the green line above) by the differential motion of the x arm that I measured in eLog 7186, I find the differential motion of the test mass (NOTE: I converted the differential motion to displacement by multiplying by (1/2*pi*f)).

It agrees within an order of magnitude to the seismic wall from the displacement noise spectrum hanging above the control room computers.

Finally, I looked at how the geophone and accelerometer noise spectra looked compared to the ground differential motion (any STACIS sensor signal will also be multiplied by the stack/pendulum transfer function, so I'm comparing to the differential motion before it goes through the chamber). Below about 1 Hz, it is clear from the plot below that the STACIS could never be of any benefit, even with accelerometers rather than geophones as the feedback sensors.

 I made the plots a little nicer and added new sensor noises (from Brian Lantz's scripts and measurements). Click to enlarge.

The last plot shows that these other sensors' noises are lower than the differential ground motion below 1 Hz.  Though 3 seismometers per STACIS is impractical, this shows that such seismometers could be used as feedforward sensors and provide isolation against differential ground motion. At these noise levels, the noise of the high voltage amplifier circuit in the STACIS would probably be the limiting factor.

For the preparation of the electronics upgrade, three 18bit DAC AI chassis were transformed to 16bit version.

The power supply connections were touched, so the units were tested with +/-18V, and they work as expected.

Using Alberto's paper LIGO-T10002-09-R titled "40m RF PDs Upgrade", I calibrated the vertical axis in the bode plots I had obtained for the two PDs ET-3010 and ET-3040.

I am not sure whether the values I have obtained are correct or not(i.e. whether the calibration is correct or not). Kindly review them.

EDIT: Attached the formula used to calculate transimpedance for each data point and the values of other paramaters.

EDIT 2: Updated the plots by changing the conversion for gettin ghte ratio of the transfer functions from 10^(y/10) to 10^(y/20).

EDIT: Please ignore the following data. The revised data and plot are in Elog 10089 

Yesterday evening, I conducted the same measurements done in Elog-10059 using the same REF PD (NF 1611) and the same model of BBPD, but on different piece that needed to be checked. 

I moved the NA from near rack 1Y1 to the Jenne laser table and back again after the readings were done.

 Acquiring data

• The following conditions were set on Network Analyzer Agilent 4395:

1) Frequency sweep range: 1MHz to 300 MHz.

2) Number of Points sampled in  the range: 201

3) Type of sweep: Logarithmic

• Set the NA to give the corresponding transfer function value (output of BBPD over output of 1611) and also Phase response in degrees.
• Save the data into floppy disk for processing on the computer.

 Results

The Plots of transimpedence obtained are attached. The data and matlab code used is in the zip file.

The transimpedance of  Broadband photodiode (D1002969-v8) was around 50kV/A-70kV/A (Unusually high) for most of the range (2), but the value started falling as the frequency approached 200 MHz.

The high impedance might be because the PD is faulty.   

Oh, nice! This must be a new technique to have a higher transimpedance by breaking the PD.

Now both BBPDs are showing abnormally high impedance.
(Remember, you have not revised your previous entry after my pointing out you have a bug in the code.)

You should break down the measurement into each raw numbers for validation.
And if this high impedance is still true, you should point out what is causing of this anomaly.

  [Nichin, Koji] 

Today evening, me and koji decided to get down to the problem of why the trasimpedence plots were not as they were supposed to be for Broadband photodiode (D1002969-v8) S1200269. There were a few problems that we encountered:

• Turns out the REF PD was not illuminated properly, for maximum output. The DC output voltage turned out to be much higher than the previous measurement. Since I assumed that the REF PD had not been touched since the first day I took readings, I did not check this.
• The fork holding the Test PD was a bit out of shape and only one side of it was clamping down the PD. This made the PD vulnerable swivel about that one side. We replaced it with a new one.
• I was setting the current diving the Jenne laser to about 20mA and this resulted in nocthes at higer frequencies in the network analyzer due to over driving of the diode laser. Once we reduced this to about 12.5-13 mA they disappeared. Also, the current limit setting was set at 40mA which is way too high for the jenne laser and might have resulted in damaging it if someone had accidentally increased the current. We have now set it at 20mA.

After these changes the measurements are as follows:

I moved the NA from near rack 1Y1 to the Jenne laser table. 

 Acquiring data

• Jenne Laser driving current: 12.8mA 
• The following conditions were set on Network Analyzer Agilent 4395:

1) Frequency sweep range: 1MHz to 300 MHz.

2) Number of Points sampled in  the range: 801

3) Type of sweep: Logarithmic

• Set the NA to give the corresponding transfer function value (output of BBPD over output of 1611) and also Phase response in degrees.
• Save the data into floppy disk for processing on the computer.

 Results

DC output voltage of REF PD: 0.568V

DC output voltage of BBPD: 18mV

Power incident on REF PD and BBPD respectively: 0.184mW  and 0.143mW

Hence, Responsivity for REF PD and BBPD respectively:  0.315 A/W and 0.063 A/W 

Responsivity given in the Datasheet for REF PD and BBPD : 0.68 A/W and 0.1 A/W

The reason for these differences are unknown to me and must be investigated.

The Plots of transimpedence obtained are attached. The data and matlab code used is in the zip file.

The transimpedance of  Broadband photodiode (D1002969-v8) S1200269 was around 1kV/A-2kV/A for most of the range, but the value started falling as the frequency approached 100 MHz. This BBPD is best when used at 10-30 MHz.

[Gautam Koji]

Taking the opportunity to shutdown c1ioo for adding a DAC card, we shutdown chiara and worked on moving of the main disk to the bigger home.

We shutdown most of the martian machines including the control machines, megatron, optimus, and nodus.

- Before shutting down chiara, we ran rsync to make the 4TB disk (used to be teh backup) and /cvs/cds synced.

sudo rsync -a --progress /home/cds/ /media/40mBackup

- Modified /etc/fstab

proc            /proc           proc    nodev,noexec,nosuid 0       0
# / was on /dev/sda1 during installation
UUID=972db769-4020-4b74-b943-9b868c26043a /               ext4    errors=remount-ro 0       1
# swap was on /dev/sda5 during installation
UUID=a3f5d977-72d7-47c9-a059-38633d16413e none            swap    sw              0       0
UUID="90a5c98a-22fb-4685-9c17-77ed07a5e000"    /media/40mBackup       ext4      defaults,relatime,commit=60       0         0
#fb:/frames      /frames nfs     ro,bg

UUID=92dc7073-bf4d-4c58-8052-63129ff5755b   /home/cds    ext4    defaults,relatime,commit=60    0   0

- Shutdown chiara. Put the 4TB disk in the chassis. We also installed a new disk (but later it turned out that it only has 2TB...)

- Restart the mahcine. This already made the 4TB disk mounted as /cvs/cds .

- Restart bind9 with DHCP for the diskless clients (cf. https://wiki-40m.ligo.caltech.edu/CDS/How_to_join_martian)

sudo service bind9 restart
sudo service isc-dhcp-server restart

- Looks like /etc/resolv.conf is automatically overwritten by a tool or something everytime we restart the machine!? I still don't know how to avoid this. (cf.  https://www.ctrl.blog/entry/resolvconf-tutorial). But at least for today we manually wrote /etc/resolv.conf

controls@chiara|backup> cat /etc/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 192.168.113.104
nameserver 131.215.125.1
nameserver 8.8.8.8

search martian

Follow up:

- At least it was confirmed that the local backup (4TB->2TB) is regularly running every morning.

- The 2TB disk was used up to 95%. To ease the size of the remaining space, I have further compressed the burt snapshot folders. (~2016). This released another 150GB. The 2TB is currently used up to  87%.

Prev

Filesystem      1K-blocks       Used  Available Use% Mounted on
/dev/sdc1      3845709644 1731391748 1918967020  48% /home/cds
/dev/sdd1      2113786796 1886162780  120249888  95% /media/40mBackup

Now

Filesystem      1K-blocks       Used  Available Use% Mounted on
/dev/sdc1      3845709644 1731706744 1918652024  48% /home/cds
/dev/sdd1      2113786796 1728124828  278287840  87% /media/40mBackup

[Jenne, Diego]

Tonight we were able to transition DARM from DC transmission signals to AS55Q/(TRX+TRY).  That's about as far as we've gotten though.

Here are the details:

• Set the ASDC->MICH matrix element such that the MICH fringes were 0-1.  For some reason this number seems to change by ~10% or so each night.
• Followed main carm_cm_up script, although stopped at MICH offset of 25% (mostly because I forgot to let it go to 50% - no fundamental reason)
• So, MICH was at 25% (with a + for the gain accidentally, even though we decided yesterday that - was better), arm powers were about 1.1 or so.
• Took transfer functions driving DARM and looking at normalized AS55Q, and driving CARM looking at normalized REFL11I.
  • There is still not a lot of coherence in the CARM->REFL11I case, so we decided to stick with DARM for starters.
  • The TF between DARM and AS55Q looked really nice!
• Prepared the unused DARM error signal row, including an offset before the blend matrix.
• Transitioned over to normalized AS55Q.
  • This left the DARM servo filterbank with a zero digital offset.
  • But, the error signal had an offset before it got to the DARM filter bank.
    • This offset does not have any ramping (I don't know how to do that when building a model), so it's not as nice for reducing an offset.
    • Maybe we can, after transitioning to the new signal, move the offset to the DARM servo filterbank?
• Was reducing the DARM offset so that we were at the true AS55Q zero crossing.
• Saw that the UGF servo lines were starting to get a bit lost in the noise, so I increased the DARM's amplitude.
  • I don't know if the UGF servo was already too far gone and increasing the SNR couldn't recover it, or if I was driving too hard and directly kicked myself out of lock.  Either way, we lost lock.

The carm_cm_up script now should get all the way to this point by itself, although occasionally the PRMI part will lose lock (but not the arms), so you have to go back to the 3nm CARM offset and relock the central part.  I have written a little "relockPRMI.sh" script that lives in ..../scripts/PRFPMI/ that will take care of this for you.  

We were able to transition DARM to AS55Q a total of 3 or so times tonight.  The first time was with the + MICH gain, and the rest of the times were with - MICH gain.  The carm_up script now asks for a sign for the MICH gain just after asking for a CARM offset sign. 

I think that we understand all of our locklosses from these states.  Twice (including the time described above) the UGF lines got lost in the noise, and the UGF servos went crazy.  Once the PRCL loop rang up, because a filter that wasn't supposed to be on was on.  This was a terrible filter that I had made a long time ago, and was never supposed to be part of the locking sequence, but it was getting turned on by a restore script, and kept eating our phase.  Anyhow, I have deleted this terrible boost filter so it won't happen again (it was called "boost test", which may give you an idea of how non-confident I was in its readiness for prime-time).  The last time of the night I must not have been quite close enough in CARM offset, so we should probably check with a TF before making this last jump.

Diego wrote a nifty burt restoring script that will clear out all the elements of the input matrix and the normalization matrix for a row that you tell it (i.e. DARM_A will clear out all the elements in the first row of those 2 matrices).  This is useful for the switches back and forth between the _A and _B signals, to make sure that everything is in order.  So, I now run those clear scripts, then put in the elements that I want for the next step.  For example, DARM initially locks with ALS using the A row.  Then, DARM transitions to the B row for DC transmission.  Then, I prepare the A row for AS55Q locking, and I don't want any elements accidentally left from the ALS signal.  It lives in ..../scripts/LSC/InputMatrix/

Thoughts for tomorrow:

Daytime re-commission the Xarm ASS.

Nighttime try to get back to DARM on AS55Q and push farther forward. 

Why AS55/(TRX + TRY) instead of just TRX? Isn't (TRX+TRY) controlled by CARM?

(question is secretly from Kiwamu)

Better elog tomorrow - notes for now:

REFL165 for PRMI has been "a champ" (quote from Q).  We're able to sit on ALS at average arm powers of 30ish.  Nice. 

Some ALSfool work - measured cancellation almost as good as single arm. 

One time transitioned CARM -> normalized REFL55I

Many times did DARM -> normalized AS55Q, see lots of noise at 39ish Hz - may be coupling from MICH??

Arm ASC loops helped improve dark port contrast. 

Note to selfs:  Need to make sure DTT templates have correct freq ordering - must be small freqs to large freqs.

[Jenne, EricQ]

A slightly more coherent elog for last night's work.

All night, we've been using REFL165 to hold the PRMI.  It's working very nicely.  To help it catch lock, I've set the gain in the PRCL filter bank high, and then the *0.6 filter triggers on.  The carm_cm_up script now will lock the PRMI on REFL165. 

We had to reset the REFL165 phase after we acquired lock - it was -91, but now is -48.  I'm not sure why it changed so significantly from the PRMI-only config to the PRFPMI config.

We measured the ALS fool cancellation with the arms held off resonance, at arm powers of a few.  Although, they were moving around a lot, but the measurement stayed nice and smooth.  Anyhow, we get almost as good of cancellation as we saw with the single arm (after we made sure that both phase trackers had the same UGF):

ALSfool_PRFPMI_2Mar2015.pdf

We were able to partly engage it one time, but we lost lock at some point.  Since the frame builder / daqd decided that that would be just the *perfect* time to crash and restart, we don't have any frame data for this time.  We can see up to a few seconds before the lockloss, while we were ramping up the RF PD loop gain though, and MICH was hitting the rails.  I'm not sure if that's what caused the lockloss, but it probably didn't help.

The ALS fool gain was 22, and we were using FMs 4, 6 (the pendulum and Rana's "comp1"), the same filters that were used for the single arm case.  The LSC-MC filter bank gain lost lock when we got to about 5.6 (we were taking +3dB steps).

We were using REFL55I/(TRX + TRY) as our CARM RF error signal.  We were using REFL55 rather than REFL11 because we were worried that REFL11 didn't look good - maybe it was saturating or something.  To be looked into.

Here's the striptool that was running at the time, since we don't have frame data:

At this point, since we weren't sure what the final gain should be for the RF CARM signal, and we could sit at nice high arm powers (arm powers of 30ish correspond to CARM offsets of about 50pm), we decided to try just a straight jump over to the RF signals. 

The first time around, we jumped CARM to (-0.2)*REFL55/(TRX+TRY), but we only stayed lock for 1 or 2 seconds.  That was around 1:55am.

We decided that perhaps it would be good to get DARM moved over first, since it has a much wider linewidth, so the rest of the trials for the night were transitioning DARM over to (0.0006)*AS55Q/(TRX + TRY).  AS55 was saturating, so we reduced its analog gain from 18dB to 9dB and re-ran the LSC offsets.  The MICH noise was pretty high when we were at low CARM offset, although we noticed it more when DARM was on AS55.  In particular, there is some peak just below 40Hz that is causing a whole comb of harmonics, and dominating the MICH, PRC and DARM spectra.  I will try to get a snapshot of that tonight - I don't think we saved any spectra from last night.  Turning off DARM's FM3 boost helped lower the MICH noise, so we think that the problem is significant coupling between the two degrees of freedom. 

After the first one or two tries of getting DARM to AS55, we started engaging the arm ASC loops - they helped the dark port contrast considerably.  The POP spot still moves around, but the dark port gets much darker, and is more symmetric with the ASC on.

Just in case there was some confusion, the champagne on my desk is not to be opened before I get back, no matter how many signals are transitioned to RF.

[Jenne, Diego, EricQ]

Hopefully there will be more later, but Chiara just went down (network? other?  Q is in there right now looking at it), so this is a so-far-tonight elog.

We have successfully transitioned MICH over from REFL33Q to ASDC in both the PRMI and PRFPMI configurations.  Next up is to start reducing the CARM offset.

Resetting the REFL demod phases

I have been unable to lock the PRMI for more than teeny blips since Thursday.  So, tonight I finally got it to lock with MICH on AS55Q and PRCL on REFL33I, and used that to set the demod phases. 

Setting the demod phases, I used an oscillation of 100 cts to PRM, at 400.123 Hz.

REFL 33 demod phase started at 148deg, now 133.2deg.

REFL165 phase started at -105.53, now -172.

No signal in REFL55????  Time series and spectra both look just like noise.  Need to check alignment of beam on PD, or if cables unplugged!!

REFL11 phase started at 16.75, now 18.9deg.

Was then able to lock on REFL 33 I&Q, like normal.

Transitioning PRMI from REFL33Q to ASDC

With the PRMI locked on REFL33 I&Q, I found that a MICH offset of -5 counts gives a minimum in ASDC.  From my earlier elog this evening (http://nodus.ligo.caltech.edu:8080/40m/10887), I expect the minimum to be at +1.4nm.  This is only one point though, so I don't know the calibration of the MICH offset yet (we should get this calib during the day by looking at MICH-only).  Anyhow, this informed which side was positive and negative relative to my Optickle plots, so I know that I wanted positive offset in the MICH servo.

I was able to comfortably hold lock at +20 counts.  Looking at a calibration line at 143.125 Hz, I determined that I wanted the matrix element for ASDC to be -0.05.  After I made that transition using ezcastep, I put the POPDC normalization in.  At the time, POPDC was about 151counts, so I put 1/151 in the POPDC->Mich matrix element.

So, here were the final lock parameters.  Note that in PRMI-only, you can acquire lock like this, and with a variety of MICH offsets:

Locking PRMI part of PRFPMI

Since the PRMI has been fussy, I'm including a brief note on the PRMI settings when the arms are held with ALS off by roughly 3nm.  To get to this point, we just ran the usual carm_cm_up script, and didn't let it run anymore when it asked for confirmation that PRMI was locked.

With MICH offset of -30 counts, AS port is pretty bright.  ASDC dark offset is set to -475.4 by the LSCoffsets script. with MICH offset = 0, ASDC_OUT is around 300counts.  But, with MICH offset = -30, ASDC_OUT is about 525 counts.  So, I put that 525 counts into the ASDC filterbank offset (so it is now the dark offset + this extra offset), so the ASDC offset is currently around -1,000.  This makes the ASDC signal roughly zero when I am ready to transition MICH over to it.  In principle I should probably set it so the average is the same as the MICH offset, but the noise is so high relative to that offset, that it doesn't matter.

After this, we engaged the CARM and DARM UGF servos.  MICH was gain peaking, so I think we might want to turn that one on too, rather than my by-hand turning down the gain.

The transition has been successful 4 or 5 times with the arms held off resonance at 3nm.  Once, we reduced the CARM offset as low as 1.7 (and had to lower the MICH gain to 1.5), but we were still hearing a woomp-woomp sound.  Not sure what that was from.  At this point, Chiara died, so we lost lock.  After that, we re-acquired lock a few more times, but MC keeps losing it.  We are still able to make the MICH to ASDC transition though, which is good.

The transition won't work if the PRCL UGF servo is not on.  The gain multiplier goes from about 1.1 up to 2.4, so the PRCL gain is certainly changing through the transition.

Diego has written up scripts for the individual UGF servos (look for an elog from him separately), so now the carm_cm_up script goes as far as locking the PRMI on REFL33 I&Q, and then it starts to transition.  PRCL UGF is engaged, MICH offset is set to -30 counts, MICH is transitioned to ASDC, POP normalization engaged, CARM UGF servo turned on, and DARM UGF servo turned on.  There are "read"s in the script before each step, so you can stop whenever you like.

Here's the final configuration for the PRFPMI while the arms are held at 3nm, with MICH on ASDC (so after the transition):

The transition for MICH to ASDC has been successful with the arms held off resonance several times tonight. It's all part of the carm_cm_up script now. I think that if we hadn't lost about an hour of time and our momentum, we would have gotten farther.  I have high hopes for tomorrow night!

These are the parameters of the UGF servos we used last night:

Some tweaking of such parameters and the commissioning of the MICH servo will be done soon; an elog post about the UGF scripts/medm screens also will be done soon.

Steve pointed out to me (this is not in his original elog, although you can see it in the photo if you look closely), that we can't really move the table legs any closer to the chamber.  We have maybe 3" of clearance between the table leg and the blue support tube that supports the bottom of the stack.  Therefore, we can't just

So Steve's proposal is to leave the legs exactly where they are, and just put a larger table on those legs.  This leaves 9" unsupported on the chamber side, and 3" unsupported on the far side.  The tables are 4" thick. 

Steve also mentions that we will lose 1.5" on all 4 sides of the table, with the new acrylic boxes, so we'll be down to 1'9" unless we get the larger table, in which case we'd have 2'9", and 3'9" on the long direction.

I would like to see a sketch of the end tables, so we can see if 1'9" x 3'9" is enough.  Manasa is working on a new end table layout in parallel to the ringdown stuff.  If we're actually concerned about the input angle of the oplevs, then to fix that we need to either get the bigger table and hang it off the edge of the legs, or perhaps as Dmass suggested, get a "doggy cone collar", and give ourselves a larger opening angle of access to the viewport, from the current table location.

I measured the transmitted power @1064nm on one of the LaserOptik mirrors labled SN6

Here is the data

The mirror is not a good reflector at 0 deg.

 More data on the transmission. Measured the tranmission as a funtion of incidence angle at 1064nm

...Looks like the coating is out of spec at any angle for 1064nm. E11200219-v2

The coating should have very low 1064nm p transmission at 45 degrees, which the plot seems to indicate that it does.  That's really the only part of the spec that this measurement is saying anything about.    What makes you say it's out of spec?

Ok, yes, sorry, the data itself does indicate that the transmission is way too high at 45 degrees for 1064 p.

 I have completed all of the model modifications and medm screen updates to allow for feedback from the transmon QPD pitch and yaw signals to the ITMs. Now, we can design and test actual loops...

The signals come from c1sc[x/y] to c1rfm via RFM, and then go to c1ass via dolphin. 

Out of curiosity about the RFM+dolphin delay, I took a TF of an excitation at the end SUS model (C1:SUS-ETM[X/Y]_QPD_[PIT/YAW]_EXC) to the input FM in the ASC model (C1:ASC-ETM[X/Y]_QPD_[PIT/YAW]_IN1). All four signals exhibit the same delay of 122usec. I saved the dtt file in Templates/ASC/transmonQPDdelay.xml

This is less than a degree under 20Hz, so we don't have to worry about it. 

We need to work farther on checking out the end transmission QPD electronics situation. 

In bullet-point form, we need to:

* Ensure that the Weiss QPD head modifications have been made on these diodes.  (cf. Rai W's LLO elogs on QPDs)

* Ensure that the QPD biases are somewhere in the range of 10-15V, not the old 100V.  (Because we only need HV to make the capacitance low for RF use. Low voltage means less power dissipation in the head)

* Ensure the Rana/Rob modifications have been propagated to the whitening boards, so that we have full dynamic range.  (Steve is looking for the marked up paper schematics)

* Replace signal path resistors with low noise metal film resistors.

* Check QPDs / whitening boards for oscillation (with a scope probe), ensure that we chose an appropriate analog gain.

In thinking about the transimpedances that we want, we thought about the current that we expect.  We should get about 100 mW of light transmitted through the ETMs when we have full IFO lock.  There is a 50/50 BS to split the light between the QPD and the Thorlabs transmission diode, so we have about 50 mW incident on the QPDs, which is about 13 mW per quadrant.  With a sensitivity of about 0.15 Amps/Watt for silicon, this means that we're expecting to see about 2 mA of current per quadrant once we have the IFO fully resonant. We want this to correspond to about 5V, which means we want a transimpedance gain of around 2.5 kOhm. 

For the things that need checking, each quadrant has:

Photodiode  ------  Gain Switch 1 ----- Gain Switch 2  ------ Gain Switch 3 ------ Variable Gain Amplifier ------- Whitening stage 1 (z @ 4 Hz, p @ 40 Hz)  ------- Whitening stage 2 (z @ 4 Hz, p @ 40 Hz)

We want to check on the status of each of these switches, and whether they actually do what they say on the QPD Head screens.  Q has checked out and fixed the bit outputs for the whitening stages, but the rest still needs to be checked out.  Also note that the Switch 1, Switch 2 and Switch 3 are common to all 4 quadrants (i.e. enabling switch 1 on one quadrant enables it on all quadrants), but the variable gains and the whitening stages are individual for each quadrant.

I've measured the sensing for each of the arms, by using our calibrated oplevs, in terms of QPD counts per micron. It is:

In the absence of a lens, the QPD would be significantly more sensitive to cavity axis translation than tilt, and thus about equally sensitive to ITM and ETM angle. However, there are lenses on the end tables. I didn't go out and look at them, but found some elogs from Annalisa that mentioned 1m focal length lenses. Back-of-the-envelope calculations convince me that this can plausibly lead to the above sensitivity ratios.

I used these quantities to come up with an actuation matrix for the ASC loops, and measured the effective plant seen by the FM, fitted it to some poles( looks like zpk([],-2*pi*[1.47+3.67i,1.47-3.67i],160); ), and designed a control servo. Here is the designed loop:

The servo works on both arms, both DoFs. A DTT measurement agrees with the designed loop shape, up to a few degrees, which are probably due to the CDS delay. The RMS of the QPD error signals goes down by about 20dB, and are currently dominated by the bounce mode, so maybe we can try to sneak in some resonant gain...?

Once we confirm that they work when locking, we can write up and down lines into the locking scripts...

 [Quick post, will follow up with further detail later. Excuse my sleepy ELOG writing]

Goal: Check out the transmon QPD signal chain; see if whitening works. Assess noise for 1/sqrt(TRX/Y) use. 

First impression: Whitening would not switch on when toggling the de-whitening. The front monitors on the whitening boards are misleading; they are taken a few stages before the real output. ADC noise was by far the limiting noise source. 

I updated the binary logic in the c1scx and c1scy to actually make the binary IO module output some bits. 

After consulting a secret wiring diagram on the wiki, not linked on the rack information page (here), I worked out which bits correspond to the bypass switches in the whitening board ( a fairly modified D990399, with some notes here)

Now, FM1 and FM2 (dewhitening filters on the ETM QPD quadrants) trigger the corresponding whitening in the boards. Here's a quick TF I took of the quadrant 1 board at ETMY. (I should take a whitening+dewhitening TF too, and post it here...)

Seems to roughly work. Some features may be due to non-accounted for elements in the anti-imaging of the DAC channels I used for the excitation, or such things. The board likely needs some attention, and at least a survey of what is there. 

I also need to take dark noise data, and convert into the equivalent displacement noise in the 1/sqrt(TRX/Y) error signals. For the no-whitening ADC noise, I estimated ~1pm RMS noise on a 38pm linewidth of PRFPMI arms.