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ID Date Author Typeup Category Subject
  13771   Thu Apr 19 18:23:51 2018 KiraUpdatePEMfinal setup sketch update

since we're just going from the short rack (not the tall rack) to the seismometer, can't we use a cable shorter than 45' ?

Quote:

I've added in the dimensions to my sketch.

the panel should be completely replaced like I described. We don't want to try to squeeze it in artificially and torque the wires. It just needs to be separated from the slab by a few more cm.

  13773   Fri Apr 20 00:26:34 2018 gautamUpdateALSFibers switched out

Summary:

I think the dominant cause for the fact that we were seeing huge swing in the power coupled into the fiber was that the beam being sent in was in fact not linearly polarized, but elliptically polarized. I've rectified this with the help of a PBS. Fiber has been plugged into my polarization monitoring setup. Let's monitor for some long stretch and see if the situation has improved.

Details:

  • The new fiber mount I ordered, K6XS, arrived today. I like it - it has little keys with which all DoFs can be locked. Moreover, it is compatible with the fixed collimators which IMO is the easiest way to achieve good mode-matching into the fiber. It is basically a plug-and-play replacement for the mounts we were using. Anyways, we can evaluate the performance over the coming days.
  • I installed it on the PSL table (started work ~10pm, HEPA turned up to maximum, PSL shutter closed).
  • But even with the new rotational DoF locking feature, I saw that slight disturbances in the fiber caused wild fluctuations in my polarization monitoring setup PD outputs. This was a useful tool through the night of checking the polarization content in the two special axes - Aidan had suggested using a heat gun but shaking the fiber a bit works well too I think.
  • The PM980 fiber has an alignment key that is aligned with the slow axis of the fiber - so it is a useful alignment reference. But even by perturbing the roational alignment about the vertical by +/-15 degrees, I saw no improvement in this behavior. So I began to question my assumption that the input beam itself had clean polarization content.
  • Since my pickoff beam has gone through a QWP and two PBSs, I had assumed that the beam was linearly polarized.
  • But by putting a PBS just upstream of the input fiber coupler, I could see a beam at the S-port with an IR card (while I expected the beam to be P-polarized).
  • OK - so I decided to clean up the input polarization by leaving this PBS installed. With this modification to the setup, I found that me shaking the fiber around on the PSL table didn't affect the output polarization content nearly as dramatically as before!!yes
  • The state I am leaving it in tonight is such that there is ~100x the power in the P-polarization output monitor as the S-polarization (PER ~ 20dB). I didn't try and optimize this too much more for now, I want to observe some long term trend to see if the wild power fluctuations have been mitigated.
  • The output coupler is mounted on the inferior K6X mount, and so there is the possibility that some drift will be attributable to rotation of the output coupler in it's mount. Thermally driven length changes / time varying stresses in the fiber may also lead to some residual power fluctuations. But I don't expect this to be anywhere near the ~25% I reported in the previous elog.
  • The rejected beam from the PBS was measured to be ~300 uW. I haven't dumped this properly, to be done tomorrow.
  • HEPA turned back down to 30%, PSL enclosure closed up, PSL shutter re-opened ~0030am.
  • Note that the EX and EY fiber coupled beams are also likely subject to the same problem. We have to double check. I think it's better to have a PBS in front of the input fiber coupler as this also gives us control over the amount of light coupled into the fiber.

Power budget:

Power in Measured power (Ophir, filter OFF)
@Input coupler, before PBS 4.4 mW
P-pol content @ input coupler 4.06 mW
S-pol (rejected) from PBS 275 uW
@Output coupler 2.6 mW (MM ~65%)

 

  13774   Fri Apr 20 15:07:45 2018 KiraUpdatePEMfinal setup sketch update

If we lay the cable along the floor then it should be around 6' to the current setup and about 20' to the actual seismometer.

Edit: 16 gauge wire should be good.

Quote:

since we're just going from the short rack (not the tall rack) to the seismometer, can't we use a cable shorter than 45' ?

 

  13775   Fri Apr 20 16:22:32 2018 gautamUpdateGeneralNodus hard-rebooted

Aidan called saying nodus was down at ~345pm. I was able to access it at ~330pm. I couldn't ssh in from my machine or the control room ones. So I went to 1X7 and plugged in a monitor to nodus. It was totally unresponsive. Since the machine wasn't responding to ping either, I decided to hard-reboot it. Machine seemed to come back up smoothly. I had trouble getting the elog started - it wasn't clear to me that the web ports were closed by default, so even though the startELOGD.sh script was running fine, the 8080 port wasn't open to the outside world. Anyways, once I figured this out, I was able to start the elog. DokuWiki also seems to be up and running now... 

  13776   Fri Apr 20 16:25:08 2018 SteveUpdateWiki ETMX table layout uploaded to wiki

ETMX table layout uploaded with beam paths to the wiki.   laugh

  13777   Fri Apr 20 23:36:28 2018 KevinUpdatePEMSeismometer BLRMs

Steve secured the GPS time server in the rack above the AA board and removed the wooden block that it was resting on. The new rack is shown in attachment 1.

I then opened the AA board to see why the channels aren't working. Even though the board was powered and outputting 4.6 V, none of the chips were getting power. I must have shorted something while trying to diagnose this and the board is no longer powered either.

The schematic is given in D990147. The D68L8EX filter is bypassed on all the channels, as can be seen in attachment 3, so the board isn't really doing anything. Rana suggested that we could just bypass the whole circuit by wiring the IN channels directly to the OUT channels going to the ADC. I'll try that next for a single channel.

  13778   Sat Apr 21 20:19:05 2018 gautamUpdateGeneralMegatron hard-rebooted

I found megatron in a similar state to that which nodus was in yesterday. Clued by the fact that MCautolocker wasn't executing the mc scripts (as was evident from looking at the wall StripTool trace), I tried ssh-ing into megatron, but was unable to (despite it being responsive to ping requests). So I went into the VEA and plugged in a monitor to megatron - saw nothing on it. With no soft reboot options available, I power cycled the machine via the front panel button. It came back up smoothly. I manually restarted the autolocker, FSSslow and EX thermal control processes (the former two with initctl, while the latter runs in a tmux session). Everything seems alright for now. Not sure how long megatron has been dead for.

  13779   Sat Apr 21 20:25:12 2018 gautamUpdateALSPSL fiber pickoff status

Seems like there is still a bit of variation in the power in the two polarizations, though it is much smaller now, at the ~5% level (see Attachment #1). Since the pattern is repeating itself over the day timescale, I think this effect is not because of rotation of the output coupler in the mount, but is in fact a temperature driven waveplate effect because of imperfect alignment at the input coupler (which itself is locked down). I'm going to rotate the input coupler by 5 degrees (old = 110 degrees, new=115degrees) to see if the situation improves...


gautam Apr 24 2pm: Steve suggested confirming the correlation by hooking up the PSL table temperature sensor. This used to be logged but since the c1psl ADC card failure, has not been recorded. Assuming the sensor and preamp still work fine, we can use the PSL diagnostic Acromag (whose channels I have hijacked to monitor polarization stability already) to at least temporarily monitor the temperature inside the PSL enclosure. I am in need of a DB25 breakout board for this purpose which I am missing right now, as soon as I obtain one, I'll hook this up...

  13780   Mon Apr 23 20:06:35 2018 ranaUpdatePEMPID tune

This shows a step response of the EX seis temp control with K_I = -1 and K_P = -0.1. The time constants for both heatup and cooldown are ~2 hours.

I'm not so sure if the PID code itself makes sense though:

  # The basic finite-difference PID approximation
  e[0] = (p-s)
  print("Error signal = {}" .format(e[0])) 

  # These are the main equations of the PID Process
  u[0] = u[1]
  u[0] = u[0] + Kp * (e[0] - e[1])
  u[0] = u[0] + Ki * (e[0])
  u[0] = u[0] + Kd * (e[0] - 2*e[1] + e[2])

 

Seems like the Proportional term uses the difference (or derivative) of the error signal. This makes it more likely to pick up some high frequency noise; maybe we should low pass this signal somewhat, or at least implement a running average.

Since we still don't have an out of loop sensor or a PSL room temperature monitor or a particle counter in the frames, I've disabled the PID loop to see how much the can temperature varies with no feedback. Please leave it this way for a few days.

  13782   Tue Apr 24 09:10:20 2018 KiraUpdatePEMfinal setup sketch

I've attached the final sketch for the panel on the granite block.

  13783   Tue Apr 24 10:10:43 2018 gautamUpdateComputer Scripts / ProgramsParticle swarm hyper parameter optimization

I'm copying and pasting Nikhil's email here as he was unable to login to the elog (but should now be able to in order to reply to any comments, and add more details about this test, motivation, methodology etc).

I did some post-processing after running the grid search. The following steps were carried out:

1) Selected those sets whose cost fun were less than a specific threshold (here 10000)

2) Next task was to see if the parameters of these good solutions had some pattern

3) I used a dimensionality reduction technique called t-SNE to project the 6 dimensional parameter space to 2 dim (for better visualization )

4) Made a scatter plot of these (see fig )

5) Used K-Means to find the clusters in this data

6) MarkerSize & Color reflect the cost fun. Bigger the marker size means better the solution.

7) Visual inspection implied cluster 5 had the best ranking points & more than any other cluster

8) These points had the following Parameter set: Workers {20,40}, SwarmSize {500}, MaxIter {500}, Self Adjustment {1}, Social Adjustment {1}, Tolerance {1e-3,1e-8} 

     See fig: for the box plot 

9) It looks like is a particular set of values rather than individual values that gives the best results.

 

  13785   Tue Apr 24 15:59:23 2018 SteveUpdateWiki AP table layout 20180328
Quote:

ETMX table layout uploaded with beam paths to the wiki.   laugh

The pdf file is uploaded into the wiki.

  13787   Tue Apr 24 21:19:08 2018 KevinUpdatePEMSeismometer BLRMs

In the ongoing attempt to recover the seismometer BLRMS, I removed the AA board from the rack and modified the BS seismometer Z channel. The BS_Z BLRMs seem to be recovered after this modification.

I removed the three resistors from the output of the circuit and wired the input and from the seismometer directly to the input to the ADC. The modified schematic is shown in attachment 1. Attachments 2 and 3 show the top and bottom of the modified board. The board is doing nothing now other than serving as a connector for this channel.

I put the board back in the rack and injected a 2 Vpp signal into the BS_Z channel and saw +/- 1600 cts in C1PEM-SEIS_BS_Z. I then plugged the seismometer back into the board and took the spectrum shown in attachment 4. This shows the working Z channel giving a reasonable seismic spectrum. Note that X and Y are not modified yet.

If there are no objections, I will modify all the other channels on the board in the same way tomorrow.

  13788   Wed Apr 25 17:44:39 2018 ArnoldUpdatePEMPEM Anti-Alias wiring

Related image

 

  13790   Thu Apr 26 09:35:49 2018 KevinUpdatePEMPEM Anti-Alias wiring

I wired all 32 channels going to the AA board directly to the ADC as described in the previous log. However, instead of using the old AA board and bypassing the whole circuit, I just used a breakout board as is shown in the first attachment. I put the board back in the rack and reconnected all of the cables.

The seismic BLRMs appear to be working again. A PSD of the BS seismometers is shown in attachment 2. Tomorrow I'll look at how much the ADC alone is suppressing the common mode 60 Hz noise on each of the channels.

Steve: 5 of ADC DAC In Line Test Boards [ D060124 ] ordered. They should be here within 10 days.

  13793   Thu Apr 26 19:46:26 2018 ranaUpdatePEMPID Quixote

Increased the Integral gain (from -1 to -4) on the EX temperature controller. This didn't work a few weeks ago, but now with the added P gain, it seems stable. Daily temperature swings are now ~3x smaller.

Notes for Kira on what we need to do tomorrow (Friday):

  1. add the MEDM screen EPICS values to the DAQ so that we can plot those trends DONE
  2. add the out-of-loop sensor to the EX can
  3. reboot the AUX-EX so we can pick up the new channels and the fixed spelling of the old channels DONE
  4. Re-install EX seismometer and hook up seismometer channels to PEM DAQ so we can start testing its performance.

For those who are flabbergasted by the way I calibrated the TEMP_MON channel from volts to deg C, here's how:

XMgrace->Data->Transformations->Geometric Transforms...

use the 'scale' and 'translate' fields to change the slope and offset for calibration in the obvious ways

  13794   Thu Apr 26 20:22:21 2018 KevinUpdatePEMADC common mode rejection with new seismometer connections

Yesterday I wired the outputs from the seismometers directly to the ADC input bypassing the old AA board circuit as is described in this elog. The old circuit converted the single-ended output from the seismometers to a differential signal. Today I looked at whether 60 Hz noise is worse going directly into the ADC due to the loss of the common mode rejection previously provided by the conversion to differential signals.

I split the output from the BS Z seismometer to the new board and to an SR785. On the SR785 I measured the difference between the inner and outer conductors of the seismometer output, i.e. A-B with A the center conductor and B the outer conductor, with grounded input. At the same time I took a DTT spectrum of C1:PEM-SEIS_BS_Z_IN1. Both spectra were taken with 1 Hz bandwidth and 25 averages. The setup is shown in attachment 1.

The spectra are shown in attachment 2. The DTT spectrum was converted from counts to volts by multiplying by 2 * 10 V/32768 cts where the extra factor of 2 is from converting from single-ended to differential input. If there was common 60 Hz noise that the ADC was picking up we would expect to see less noise at 60 Hz in the SR785 spectrum measured directly at the output from the seismometer since that was a differential measurement. Since both spectra have the same 60 Hz noise, this noise is differential.

  13795   Thu Apr 26 23:00:42 2018 ranaUpdatePEMnew Seis temp chans

After fixing the spelling of the EX temperature readback, I also added all of the MEDM sliders to the C0EDCU.ini file (making sure to add an even number of channels). Restarted FB (after installing telnet on rossa):

telnet fb 8083

> shutdown


preferred method of posting DataViewer images: print as a SVG image (since its vectorized). Then from the command line do:

inkscape steven.svg --export-pdf=vass.pdf

  13797   Fri Apr 27 16:55:31 2018 gautamUpdateGeneralEY area access blocked

Steve was calibrating the load cells at the EY table with the crane - we didn't get through the full procedure today, so the area near the EY table is kind of obstructed. The 100kg donut is resting on the floor on the North side of the EY table and is still connected to the crane. There are stopper plates underneath the donut, and it is still connected to the crane. Steve has placed cones around the area too. The crane has been turned off.

  13798   Fri Apr 27 18:42:02 2018 ranaUpdatePEMnew Seis temp chans

for whatever reason, I am unable to get minute or second trends from nodus for any channels (IMC, PEM, etc) since the reboot. has there been some more recent FB failure or is this still a bug since last years FB catastrophe?

  13799   Sun Apr 29 22:53:06 2018 gautamUpdateGeneralDARM actuation estimate

Motivation:

We'd like to know how much actuation is required on the ETMs to lock the DARM degree of freedom. The "disturbance" we are trying to cancel is the seismic driven length fluctuation of the arm cavity. In order to try and estimate what the actuation required will be, we can use data from POX/POY locks. I'd collected some data on Friday which I looked at today. Here are the results.

Method:

  • I collected the error and control signals for both arm cavities while they were locked to the PSL.
  • Knowing the POX/POY sensing response and the actuator transfer functions, we can back out the free running displacements of the two arm cavities.
    • I used numbers from the cal filters which may not be accurate (although POX sensing response which was recently measured).
    • But the spectra computed using this method seem reasonable, and the X and Y arm asds line up around 1 Hz (albeit on a log scale).
    • In this context, L_X is really a proxy for |f_X - f_{MC}| and similarly for L_Y so I think the algebra works out correctly.
    • I didn't include any of the violin mode/AA/AI filters in this calculation.
  • Having calculated the arm cavity displacements, I computed "DARM" as L_y- L_x and then plotted its asd.
  • For good measure, I also added the quadrature sum of 4 optics' displacement noise as per the 40m GWINC model - there seems to be a pretty large discrepancy, not sure why.

If this approach looks legit, I will compute the control signal that is required to stabilize this level of disturbance using the DARM control loop, and see what is the maximum permissible series resistance we can use in order to realize this stabilization. We can then compare various scenarios like different whitening schemes, with/without Barry puck etc, and look at coil driver noise levels for each of them. 

  13800   Mon Apr 30 15:36:18 2018 KiraUpdatePEMfinal setup sketch

I've attached a sketch of how the panel will be mounted. We should make a small rectangular box that would raise the panel from the block by 1 cm or so to allow the cables to fit into the hole in the block without getting bent. It also has to be airtight so maybe having a thin layer of rubber between the mount and block would be good.

  13801   Mon Apr 30 23:13:12 2018 KevinUpdateComputer Scripts / ProgramsDataViewer leapseconds

I was trying to plot trends (min, 10 min, and hour) in DataViewer and got the following error message

Connecting.... done
 mjd = 58235
leapsecs_read()
  Opening leapsecs.dat
  Open of leapsecs.dat failed
leapsecs_read() returning 0
frameMemRead - gpstimest = 1208844718

 

thoough the plots showed up fine after. Do we need to fix something with the leapsecs.dat file?

  13803   Tue May 1 11:15:19 2018 KiraUpdatePEMPID Quixote

I added an out of loop sensor to the can by placing the lab temperature sensor inside the can. I'm not sure which channel is logging this temperature though. I also noticed that the StripTool still had the old misspelled name for the temperature readout so I fixed that as well.

I've attached a picture of the setup.

Quote:

Increased the Integral gain (from -1 to -4) on the EX temperature controller. This didn't work a few weeks ago, but now with the added P gain, it seems stable. Daily temperature swings are now ~3x smaller.

Notes for Kira on what we need to do tomorrow (Friday):

  1. add the MEDM screen EPICS values to the DAQ so that we can plot those trends DONE
  2. add the out-of-loop sensor to the EX can
  3. reboot the AUX-EX so we can pick up the new channels and the fixed spelling of the old channels DONE
  4. Re-install EX seismometer and hook up seismometer channels to PEM DAQ so we can start testing its performance.

For those who are flabbergasted by the way I calibrated the TEMP_MON channel from volts to deg C, here's how:

XMgrace->Data->Transformations->Geometric Transforms...

use the 'scale' and 'translate' fields to change the slope and offset for calibration in the obvious ways

 

  13804   Tue May 1 15:23:18 2018 KiraUpdatePEMnew ADC channel setup issue

[Kira, Johannes]

I connected up the channels for the ADC Acromag a while back and we were planning to install it today so that we could set up a new channel for the out of loop sensor. Unfortunately, the Acromag seems to be broken. We connected up a precision 10V voltage to one of the channels, but the Acromag read out ~7V and it kept fluctuating. Even after calibration, we still got the same result. When enabling the legacy support, we got ~11V. But when we measured the voltage at the screw terminals with a multimeter and it showed 10V, so the issue is not with the wiring. All of the channels have this same issue. We will be ordering more Acromags soon, so hopefully we'll be able to set up the channel soon. I've attached a picture of the Acromag along with the front panel with the channels labeled

  13805   Tue May 1 19:37:50 2018 gautamUpdateGeneralDARM actuation estimate

Here is an updated plot - the main difference is that I have added a trace that is the frequency domain wiener filter subtraction of the coherent power between the L_X and L_Y time series. I tried reproducing the calculation with the time domain wiener filter subtraction as well, using half of the time series (i.e. 5 mins) to train the wiener filter (with L_X as target and L_Y as witness), but I don't get any subtraction above 5 Hz on the half of the data that is a test data set. Probably I am not doing the pre-filtering correctly - I downsampled the signal to 1 kHz, weighted it by low passing the signal above 40 Hz and trained the Wiener filter on the resulting time series. But this frequency domain Wiener filter subtraction should be at least a lower bound on DARM - indeed, it is slightly lower everywhere than simply taking the time domain subtraction of the two data streams.

To do:

  • Re-measure calibration numbers used.
  • Redo calculation once the numbers have been verified.

Putting a slightly cleaned up version of this plot in now - I'm only including the coherence-inferred DARM estimate now instead of the straight up time domain subtraction. So this is likely to be an underestimate. At low (<10 Hz) frequencies, the time domain computation lines up fairly well, but I suspect that I am getting huge amounts of spectral leakage (see Attachment #2) in the way I compute the spectrum using scipy's filtering routine (once the Wiener filter has been computed). Note that Attachment #2, I didn't break up the data into a training/testing set as in this case, we just care about the one-off offline performance in order to get an estimate of DARM.

The python version of the wiener filter generating code only supports [b,a] output of the digital filter, an sos filter might give better results. Need to figure out the least painful way of implementing the low-noise digital filtering in python...

  13808   Thu May 3 00:42:38 2018 KevinUpdatePonderSqueezeCoil driver contribution to squeezing noise budget

In light of the discussion at today's meeting, Guantanamo and I looked at how the series resistance for the test mass coil drivers limits the amount of squeezing we could detect.

The parameters used for the following calculations are:

  • 4.5 kΩ series resistance for the ETM's (this was 10 kΩ in the previous calculations, so these numbers are a bit worse); 15 kΩ for the ITM's
  • 100 ppm transmissivity on the folding mirrors giving a PRC gain of 40
  • PD quantum efficiency of 0.88

Since we need to operate very close to signal recycling, instead of the current signal extraction setup, we will need to change the macroscopic length of the SRC. This will change the mode matching requirements such that the current SRM does not have the correct radius of curvature. One solution is to use the spare PRM which has the correct radius of curvature but a transmissivity of 0.05 instead of 0.1. So using this spare PRM for the SRM and changing the length of the SRC to be the same as the PRC we can get

  • 0.63 dBvac of squeezing at 205 Hz for 1 W incident on the back of PRM
  • 1.12 dBvac of squeezing at 255 Hz for 5 W incident on the back of PRM

This lower transmissivity for the SRM also reduces the achievable squeezing from the current transmissivity of 0.1. For an SRM with a transmissivity of 0.15 (which is roughly the optimal) we can get

  • 1 dBvac of squeezing at 205 Hz for 1 W incident on the back of PRM
  • 1.7 dBvac of squeezing at 255 Hz for 5 W incident on the back of PRM

The minimum achievable squeezing moves up from around 205 Hz at 1 W to 255 Hz at 5 W because the extra power increases the radiation pressure at lower frequencies.

  13812   Thu May 3 12:19:13 2018 gautamUpdateCDSslow machine bootfest

Reboot for c1susaux and c1iscaux today. ITMX precautions were followed. Reboots went smoothly.

IMC is shuttered while Jon does PLL characterization...


Now relocked.

  13815   Fri May 4 18:59:39 2018 gautamUpdateSUSStack measurement ongoing

[SV,KA,RXA,GV]

The stack weight measurement is going on at EX. ETMX watchdog is shutdown. Area is off limits over the weekend until the test is finished.


Not related to this work, but the dog clamps used on the EX table have to be re-positioned such that the clamping force is better distributed. The 2" beam splitter mount used to pick off a portion of the EX NPRO beam to the fiber has to be rotated. Also, there was a M6.9 EQ in Hawaii while we were doing this work it seems..

  13818   Sat May 5 20:30:21 2018 KojiUpdatePSLModulation depth measurement for the 3IFO aLIGO EOM and aftermath

Caution: Because of this work and my negligence, the RF output of the main Marconi for the IFO modulation is probably off. The amplifier (freq gen. box) was turned on. Therefore, we need to turn the Marconi on for the IFO locking.

I worked on my EOM m easurement using the beat setup. As there was the aux injection electronics, I performed my measurement having tried not to disturb the aux setup. The aux Marconi, the splitted PD output, and an open channel of the oscilloscope were used for my purpose. I have brought the RF spectrum analyzer from the control room. I think I have restored all the electronics back as before. I have re-aligned the beat setup after the EOM removed. Note that the aux NPRO, which had been on, was turned off to save the remaining life of the laser diode.

  13819   Sat May 5 22:32:07 2018 KojiUpdatePSLModulation depth measurement for the 3IFO aLIGO EOM

The 3IFO EOM was formerly tuned as the H2 EOM, so the resonant frequencies are different from the nominal aLIGO ones.

PORT1: 8.628MHz / 101 +/- 6 mrad_pk/V_pk
PORT2: 24.082MHz / 41.2 +/- 0.7 mrad_pk/V_pk
PORT3: 43.332MHz / 62.2 +/- 4 mrad_pk/V_pk

9MHz modulation is about x2.4 better than the one installed at LHO.
24MHz modulation is about x14 better. (This is OK as the new 24MHz is not configured to be resonant.)
45MHz modulation is about x1.4 better.
 

  13820   Mon May 7 11:46:07 2018 gautamUpdatePEMFW parameter update

As part of investigation into this issue, Jonathan Hanks pointed out that the "minute trends" being recorded by our system were actually only being recorded every 120 seconds (a.k.a. 2 minutes). He had fixed the appropriate line in the parameter file, but had not restarted the FW processes. I had restarted it on Friday. (but failed to elog it !) no

To check if this made any difference, I pulled 1 hour of "minute trend" data for the PSL table temperature channel from ~1 hour ago, and compared the number of datapoints against a 1 hour minute trend time series from 2 May. I've put the display with # of datapoints (for an identical length of time) from before [left] and after [right] the restart next to the plots in Attachment #1. Seems like we are getting minute trends written every 60 seconds now, as it should be yes.

The unavailability of trends from nodus is a separate issue for which JH has suggested another fix, to be elogged separately.

Quote:

for whatever reason, I am unable to get minute or second trends from nodus for any channels (IMC, PEM, etc) since the reboot. has there been some more recent FB failure or is this still a bug since last years FB catastrophe?

  13821   Mon May 7 15:27:28 2018 gautamUpdateSUSStack measurement expectation

[steve,gautam]

We tried to estimate what the load cell measurement should yield. Here is the weight breakdown (fudge factor for Al table is to try and account for tapped holes):

Element

Diameter [m]

Height [m]

Density [kg/m^3]

Mass [kg]

Number or fudge factor

Dim in inches

Table 1.22 0.08 2700.00 240.07 0.85 Dia=48", thickness=3"
Stack leg 0.36 0.13 8000.00 100.85 9 Dia=14", thickness=5"
Base plate 1.37 0.05 8000.00 600.18 1 Dia=60",thickness=2"
Base rods 0.10 1.83 8000.00 118.55 2 Dia=4", length=6ft
Stuff on table       100.00    
Blue beams       100.00    
             
Total [kg]       2149.01    
Total [lbs]       4835.28  

 

  • Steve pointed out that there is some material removed from the stack legs for stability (hollows into which the viton springs fit). These countersinks have dimensions of diameter=2", height=1.75". So if we assume each leg has 10% less mass, the total weight becomes ~4600lbs.
  • I think we will need to use one more load cell (i.e. total 4) for this measurement (we have more load cells, just need to setup one more controller).
  • Steve is looking into acquiring some low profile jacks to deal with the fact that we only have limited travel range on the overall stack height because of the bellows.
  • A useful document, from which we pulled some numbers (which also look reasonable using estimated dimensions and density calculations): P952005
  13822   Mon May 7 16:23:06 2018 gautamUpdateGeneralDARM actuation estimate

Summary:

Using the Wiener Filter estimate of the DARM disturbance we will have to cancel, I computed how the control signal would look like for a few scenarios. Our DACs are 16-bit, +/-10V (i.e. +/-32,768cts-pk, or ~23,000cts RMS). We need to consider the shape of the de-whitening filter to conclude whether it is feasible to increase the series resistance by x10 or not.

Some details:

Note that in this first computation, I have not considered

  • Actuation range required by other loops (e.g. local damping, Oplev etc).
  • At some point, I need to add the 2P/c radiation pressure disturbance as well.
  • The control signal is calculated assuming we are actuating equally on both ETMs (but with opposite phase).
  • RMS computation is done from 30 Hz downwards, as above 30 Hz, I think the estimate from the previous elog is not true seismic displacement. 
  • De-whitening filters (or digital whitening), which will be required to suppress DAC noise at 100Hz.
  • DARM loop shape, specifically low-pass to avoid sensing noise injection. In this calculation, I just used the pendulum transfer function.

While doing this calculation, I have accounted for the fact that right now, the analog de-whitening filters in the ETM drive chain have a x3 gain which we will remove. Actually this is an assumption, I have not yet measured a transfer function, maybe I'll do one channel at EY to confirm. Also, the actuator gains themselves need to be confirmed.

As I was looking at the coil driver schematic more closely, I realized that there are actually two separate series resistances, one for the fast controls path, and another for the DC bias voltage from the slow ADCs. So I think we have been underestimating the Johnson noise of the coil drivers by sqrt(2). I've also attached screenshots of the IFOalign and MCalign screens. The two  ITMs and ETMX have pitch DC bias values that are compatible with a x10 increase of the series resistance. But even so, we will have ~3pA/rtHz per coil from the two resistances.


gautam 8pm May8: Seems like I had confirmed the x3 gain in the EX de-whitening board when Johannes and I were investigating the AI board offset.

  13823   Mon May 7 20:01:14 2018 RorpheusUpdateGeneralUse anti-dewhitening + show CARMA/DARMA

What If I Told You - What If I Told You that bogus plots are fake news

example of plots illustrating DAC range / saturation

  13826   Tue May 8 11:41:16 2018 gautamUpdateGeneralIFO maintenance

There was an earthquake, all watchdogs were tripped, ITMX was stuck, and c1psl was dead so MCautolocker was stuck.

Watchdogs were reset (except ETMX which remains shutdown until we finish with the stack weight measurement), ITMX was unstuck using the usual jiggling technique, and the c1psl crate was keyed.

  13827   Wed May 9 17:30:04 2018 gautamUpdateGeneralInput beam misaligned

There is no beam going into the IFO at the moment. There was definitely a spot on the AS camera after I restored the suspensions yesterday, as you can see from the ASDC level in Attachment #1. But at around 2pm Pacific yesterday, the ASDC level has gone to 0. I suspect the TTs. There is no beam on the REFL camera either when PRM is aligned, and PRM's DC alignment is good as judged by Oplev.

Normally, I am able to recover the beam by scanning the TTs around with some low frequency sine waves, but not today. We don't have any readback (Oplev/OSEM) of the TT alignment, and the DC bias values havent jumped abnormally around the time this happened, judging by the OUT16 monitor points (see Attachment #2). The IMC was also locked at the time when this abrupt drop in ASDC level happened. Unfortunately, we don't have a camera on the Faraday so I don't know where the misalignment is happening, but the beam is certainly not making it to the BS. All the SOS optics (e.g. BS, ITMX and ITMY) are well aligned as judged by Oplev.

Being debugged now...

  13828   Wed May 9 19:51:07 2018 gautamUpdateGeneralInput beam misaligned

As suspected - the problem was with the TTs. I tested the TT signal chain by driving a low frequency sine wave using AWG and looking at the signal on an o'scope. But I saw nothing, neither at the AI board monitor point, nor at the actual coil driver mon point. I decided to look at the IOP testpoints for the DAC channels, to see if the signals were going through okay on the digital side. But the IOP channels were flatlined, as viewed on dataviewer (see Attachment #1). This despite the fact that the DAC output monitor screen in the model itself was showing some sensible numbers, again see Attachment #1.

Looking at the CDS overview screen, there were no red flags. But there was a red indicator sneakily hidden away in the IOP model's CDS status screen, the "DAC" field in the state word is red. As Attachment #2 shows, a change in the state word is correlated with the time ASDC went to 0.

Note that there are also no errors on the c1lsc frontend itself, judging by dmesg. I want to do a model restart, but (i) this will likely require reboots of all vertex FEs and (ii) I want to know if any CDS experts want to sniff for clues to what's going on before a model restart wipes out some secret logfiles. I'm a little confused that the rtcds isn't throwing up any errors and causing models to crash if the values are not being written to the registers of the DAC. It may also be that the DAC card itself is dead sad. To re-iterate, all the EPICS readbacks were suggesting that I am injecting a signal right up to the IOP.

Quoting from the runtime diagnostics note:

NOTE: As V2.7, if this error is detected, the IOP will output zero values to all DAC modules, as a protective measure. Only method to clear this is to restart the IOP and all applications on that computer
  13829   Thu May 10 08:45:16 2018 SteveUpdateGeneral4.5M eq. Cabazon, CA

20180508 4:49am Cabazon earth quake 4.5M at 79 miles away.  ETMX is in load cell measurment condition.

Quote:

There was an earthquake, all watchdogs were tripped, ITMX was stuck, and c1psl was dead so MCautolocker was stuck.

Watchdogs were reset (except ETMX which remains shutdown until we finish with the stack weight measurement), ITMX was unstuck using the usual jiggling technique, and the c1psl crate was keyed.

 

  13830   Thu May 10 11:38:19 2018 gautamUpdateGeneralITMY UL

Looking at Steve's plot, I was reminded of the ITMY UL OSEM issue. The numbers don't make sense to me though - 300um of DC shift in UL with negligible shifts in the other coils should have made a much bigger DC shift in the Oplev spot position.

  13831   Thu May 10 14:13:22 2018 gautamUpdateGeneralMore refinement of DARM control signal projection

Summary:

  1. It seems that after a x10 increase in the coil driver resistance, we will have enough actuation range to control (anti de-whitened) DARM without saturating the DAC.
  2. The Barry puck doesn't seem to help us much in reducing the required RMS for DARM control. If this calculation is to be believed, it actually makes the RMS actuation a little bit higher.

See Attachment #1 for the projected control signal ASDs. The main assumption in the above is that all other control loops can be low-passed sufficiently such that even with anti-dewhitening, we won't run into saturation issues.

DARM control loop:

  • I'm now calculating the DARM control signal in counts after factoring into account a digital DARM control loop.
  • The loop shape is what we used when the DRFPMI was locked in Oct 2015.
  • I scaled the overall OLTF gain to have a UGF around 200Hz.
  • The breakdown of how the DARM loop is constructed is shown in Attachment #2.

De-whitening and Anti-De-whitening:

  • The existing DW shape in the ITM and ETM signal chains has ~80dB attenuation around 100 Hz.
  • Assuming ~5uV/rtHz noise from the DAC, 60dB of low-passing gets us to 5nV/rtHz. With 4.3kohm series resistance, this amounts to ~1pA/rtHz current noise (compared to ~3pA/rtHz from the Johnson noise of the series resistance). Actually, I measured the DAC noise to be more like ~700nV/rtHz at 100 Hz, so the current noise contribution is only 0.16pA/rtHz.
  • This amounts to getting rid of the passive filter at the end of the chain in the de-whitening board.
  • Attachment #3 shows the existing and proposed filter shapes.

It remains to add the control signals for Oplev, local damping, and ASC to make sure we have sufficient headroom, but given that current projections are predicting using up only ~1000cts of the ~23000cts (RMS) available from the DAC, I think it is likely we won't run into saturations. Need to also figure out what the implication of the reduced actuation range will be on handling the locking transient.

  13833   Fri May 11 13:58:42 2018 ranaUpdateGeneralMore refinement of DARM control signal projection

I think "OLG" trace is not labeled right; it would be good to see the actual OLG in addition to whatever that trace actually is.

Based on the first plot, however, my conclusion is that:

  1. we don't need the passive isolator to reduce the control signal; the control signal is dominated by f < 10 Hz.
  2. we should still look into isolators for the reduction of the f > 50 Hz stuff, just to make the overall DARM sensitivity better. But this does not have to be pneumatic since we no longer need 10 Hz isolation. It can instead be a solid piece of rubber to give us a ~20-30 Hz resonance. That would still give us a factor of 5-10 improvement above 100 Hz.
  3. In this case, we only need a mass estimate of the end chamber contents with an accuracy of ~25%. If we think we have that already, we don't need to keep doing the jacks-strain gauge adventure.
  13834   Fri May 11 18:17:07 2018 gautamUpdateDetCharAUX laser PLL setup

[koji, gautam]

As discussed at the meeting earlier this week, we will use some old *MOPA* channels for interfacing with the PLL system Jon is setting up. He is going to put a sketch+photos up here shortly, but in the meantime, Koji helped me identify a channel that can be used to tune the temperature of the Lightwave NPRO crystal via front panel BNC input. It is C1:PSL-126MOPA_126CURADJ, and is configured to output between +/-10V, which is exactly what the controller can accept. The conversion factor from EPICS value to volts is currently set to 1 (i.e. EPICS value of +1 corresponds to +1V output from the DAC). With the help of the wiring diagram, we identified pins 3 and 4 on cross-connect #J7 as the differential outputs corresponding to this channel. Not sure if we need to also setup a TTL channel for servo ENABLE/DISABLE, but if so, the wiring diagram should help us identify this as well. 

The cable from the DAC to the cross-connect was wrongly labelled. I fixed this now.

  13835   Fri May 11 19:02:52 2018 gautamUpdateGeneralMore refinement of DARM control signal projection

I was a bit hasty in posting the earlier plots. In the earlier plot, the "OLG" trace was OLG * anti dewhitening as Rana pointed out.

Here are the updated ones, and a cartoon (Attachment #5) of the loop topology I assumed. I've excluded things like violin filters, AA/AI etc. The overall gain scaling I mentioned in the previous elog amounts to changing the optical sensing response in this cartoon. I now also show the DARM suppression (Attachment #4) for this OLG and the DARM linewidths for RSE. I don't think the conclusions change.

Note that for Signal Recycling, which is what Kevin tells us we need to do, there is a DARM pole at ~150 Hz. I assume we will cancel this in the digital controller and so can achieve a similar OLG shape. This would modify the control signal spectrum a little around 150Hz. But for a UGF on the loop of ~150 Hz, we should still be able to roll-off the control signal at high frequencies and so the RMS shouldn't be dramatically affected.

Steve is looking into acquiring 4.5kohm Vishay Wirewound resistors with 1% tolerance. Plan is to install two in parallel (so that we get 2kohm effective resistance) and then snip off one once we are convinced we won't have any actuation range issues. Do these look okay? They're ~$1.50ea on mouser assuming we get 100. Do we need the non-inductive winding?

Quote:

I think "OLG" trace is not labeled right; it would be good to see the actual OLG in addition to whatever that trace actually is.


  13836   Sat May 12 10:02:03 2018 ranaUpdateGeneralMore refinement of DARM control signal projection

Good question! I've never calculated what the resonance frequency would be if had an inductive resistor with our cable capacitance (~50 pF/m I guess).

  13837   Sun May 13 15:15:18 2018 gautamUpdateGeneralCDS crash

I found the c1lsc machine to be completely unresponsive today. Looking at the trend of the state word, it happened sometime yesterday (Saturday). The usual reboot procedure did not work - I am not able to bring back any of the models on any of the machines, during the restart procedure, they all fail. The logfile reads (for the c1ioo front end, but they all behave the same):

[  309.783460] c1x03: Initializing space for daqLib buffers
[  309.887357] CPU 2 is now offline
[  309.887422] c1x03: Sync source = 4
[  309.887425] c1x03: Waiting for EPICS BURT Restore = 2
[  309.946320] c1x03: Waiting for EPICS BURT 0
[  309.946320] c1x03: BURT Restore Complete
[  309.946320] c1x03: Corrupted Epics data:  module=0 filter=1 filterType=0 filtSections=134610112
[  309.946320] c1x03: Filter module init failed, exiting
[  363.229086] c1x03: Setting stop_working_threads to 1
[  364.232148] DXH Adapter 0 : BROADCAST - dx_user_mcast_unbind - mcgroupid=0x3
[  364.233689] Will bring back CPU 2
[  365.236674] Booting Node 1 Processor 2 APIC 0x2
[  365.236771] smpboot cpu 2: start_ip = 9a000
[  309.946320] Calibrating delay loop (skipped) already calibrated this CPU
[  365.251060] NMI watchdog enabled, takes one hw-pmu counter.
[  365.252135] Brought the CPU back up
[  365.252138] c1x03: Just before returning from cleanup_module for c1x03

Not sure what is going on here, or what "Corrutped EPICS data" is supposed to mean. Thinking that something was messed up the last time the model was compiled, I tried recompiling the IOP model. But I'm not able to even compile the model, it fails giving the error message

make[1]: Leaving directory '/opt/rtcds/caltech/c1/rtbuild/3.4'
make[1]: /cvs/cds/rtapps/epics-3.14.12.2_long/modules/seq/bin/linux-x86_64/snc: Command not found
make[1]: *** [build/c1x03epics/c1x03.c] Error 127
Makefile:28: recipe for target 'c1x03' failed
make: *** [c1x03] Error 1

I suspect this is some kind of path problem - the EPICS_BASE bash variable is set to /cvs/cds/rtapps/epics-3.14.12.2_long/base on the FEs, while /cvs isn't even mounted on the FEs (nor do I think it should be). I think the correct path should be /opt/rtapps/epics-3.14.12.2_long/base. Why should this have changed?

I've shutdown all watchdogs until this is resolved.

  13838   Sun May 13 17:31:51 2018 gautamUpdateGeneralCDS crash

As suspected, this was indeed a path problem. Johannes will elog about it later, but in short, it is related to some path variables being changed in order to try and streamline the EPICS processes on the new c1auxex machine (Acromag Era). It is confusing that futzing around with the slow computing system messes with the realtime system as well - aren't these supposed to be decoupled? Once the paths were restored by Johannes, everything compiled and restarted fine. We even have a beam on the AS camera, which was what triggered this whole thingyes.

Anyways, Attachment #1 shows the current status. I am puzzled by the red TIMING indicators on the c1x04 and c1x02 processes, it is absent from any other processes. How can this be debugged further?

Quote:
 

I suspect this is some kind of path problem - the EPICS_BASE bash variable is set to /cvs/cds/rtapps/epics-3.14.12.2_long/base on the FEs, while /cvs isn't even mounted on the FEs (nor do I think it should be). I think the correct path should be /opt/rtapps/epics-3.14.12.2_long/base. Why should this have changed?

  13839   Sun May 13 20:48:38 2018 johannesUpdateGeneralCDS crash

I think the root of the problem is that the /opt/rtapps/ and /cvs/cds/rtapps/ mounting locations point to the same directory on the nfs server. Gautam and I were cleaning up the /cvs/cds/caltech/target/ directory, placing the previous contents of /cvs/cds/caltech/target/c1auxex/, including database files and startup instructions in /cvs/cds/caltech/target/c1auxex_oldVME/, and then moved /cvs/cds/caltech/target/c1auxex2/, which has the channel database and initialization files for the Acromac DAQ, to /cvs/cds/caltech/target/c1auxex/.

This also required updating the systemd entries on c1auxex to point to the changed directory. While confirming that everything worked as before we noticed that upon startup the EPICS IOC complains about not being able to find the caRepeater binary. This was not new and has not limited DAQ functionality in the past, but we wanted to fix this, as it seemed to be some simple PATH issue. While the paths are all correctly defined in the user login shell, systemd runs on a lower level and doesn't know about them. One thing we tried was to let systemd execute /cvs/cds/rtapps/epics-3.14.12.2_long/etc/epics-user-env.sh initializing EPICS. It was strange that the content of that file was pointing to /opt/rtapps/epics-3.14.12.2_long/base, which is not mounted on the slow machines, so we changed the /opt/ it to /cvs/cds/, not realizing that the frontends read from the same directory (as Gautam said, /cvs/cds does not exist as a mount point on the frontend). It ended up not working this way, and apparently I forgot to change it back during clean up. But worse, never elogged it!

In the end, we managed to to give systemd the correct path definitions by explicitly calling them out in /cvs/cds/caltech/target/c1auxex/ETMXenv, to which a reference was added in the systemd service file. The caRepeater warning no longer appears.

  13841   Mon May 14 18:58:32 2018 KevinUpdatePonderSqueezeSqueezing with no SRM
Quote:

Note that for Signal Recycling, which is what Kevin tells us we need to do, there is a DARM pole at ~150 Hz.

To be quantitative, since we are looking at smaller squeezing levels and considering the possibility of using 5 W input power, it is possible to see a small amount of squeezing below vacuum with no SRM.

Attachment 1 shows the amount of squeezing below vacuum obtainable as a function of homodyne angle with no SRM and 5 W incident on the back of PRM. The optimum homodyne angle at 210 Hz is 89.2 deg which gives -0.38 dBvac of squeezing. Figure 2 is the displacement noise at this optimal homodyne angle and attachment 3 is the same noise budget shown as the ratio of the various noise sources to the unsqueezed vacuum.

The other parameters used for these calculations are:

  • 4.5 kΩ series resistance for the ETM coils; 15 kΩ for the ITM coils
  • 100 ppm transmissivity on the folding mirrors giving a PRC gain of 40
  • PD quantum efficiency of 0.88

So maybe it's worth considering going for less squeezing with no SRM if that makes it technically more feasible.

  13842   Tue May 15 10:42:14 2018 KojiUpdatePSLModulation depth measurement for the 3IFO aLIGO EOM and aftermath

The marconi RF output was turned on and thus the RF generator condition was restored to the nominal state on Friday 11th.

ELOG V3.1.3-