The next steps we should do are :

We can modify the freq divider circuit to make it a comparator.

There are 3 standard techniques to reduce this effect:

1) Stabilize the end laser by sensing the green light coming into the PSL before recombination and feeding back with SR560 (this is the only one that you should try at first).

2) Moving to the center of the MFD fringe via ETM steps.

3) Auto-alignment of the beam to the arm.

[Jenne, Chris, Kiwamu]

 A photo diode and an AOM driver have been newly setup on the PSL table to measure the intensity noise coupling to the beat note signal.

We tried taking a transfer function from the PD to the beat, but the SNR wasn't sufficient on the PD. So we didn't get reasonable data.

(what we did)

  - put a DCPD after the doubling crystal on the PSL table. The PD is sitting after the Y1 mirror, which has been used for picking off the undesired IR beam.

  - installed the AOM driver (the AOM itself had been already in place)

  - injected some signals onto the AOM to see if we can see an intensity fluctuation on the PD as well as the beat signal

(intensity noise)

  In order to have better SNR for the intensity measurement, we put an AC coupled SR560 with the gain of 100 just before the ADCs.

When a single frequency signal was applied from a Stanford Research's function generator to the AOM, we could clearly see a peak at the doubled frequency of the injected signal.

Also a peak at the same frequency was found on the beat note signal as well.

But when random noise was injected from the same function generator, the random noise looked below the ADC noise.

Jenne adjusted the output voltage from the PD to about 1 V to avoid a saturation in the analog path, but later we realized that the ADC counts was marely ~ 20 counts.

So we will check the ADC tomorrow. Hopefully we will get a good SNR.

Aidan: Joe and I have added a channel that takes the DC output from the vertex beatnote PD and sends it, via RFM, to a DAC at the ETMX end. Immediately before the output is a filter C1GCX_AMP_CTRL. The output of the DAC is connected to the CURRENT LASER DIODE modulation input on the back of the Innolight driver. This will modulate the current by 0.1A/V input.

We should be able to modulate the green laser on the end now and stabilize the intensity of the amplitude on the beatnote PD at the vertex. (In this configuration, the ampltiude noise of the PSL laser will be injected onto the end laser - we may want to revisit that).

Joe's comments on model change:

I added a RFM connection at the output of the C1:GCV-XARM_BEAT_DC filter in the c1gcv model.  The RFM connection is called: C1:GCV-SCX_ETMX_AMP_CTRL.

This RFM connection goes to the c1scx model and into Kiwamu's GCX box, which uses top_names.  There's a filter inside called AMP_CTRL, so the full filter name is C1:GCX-AMP_CTRL.  The output then goes to the 7th DAC output.

Photos:

1. NPRO CURRENT CTRL plugged into DAC channel 7
2. You can actually see it's channel 7 in this image
3. The other end plugged into the back of the Innolight driver
4. Schematic of the setup
5. Updated C1ALS_OVERVIEW MEDM screen (I don't know why the field in the background turned orange - maybe it's coming into a long dry summer?)

The reason that I chose this PD is that, apparently, the green light coming from the cavity is clipped when it is picked off for its DC PD.

Ridiculous and hacky. Digital stabilization removed as well as the old "leave a pile of equipment on a stool" strategy.

We used a a BNC cable to send a pickoff of the beam before the recombination to the end via an SR560.

 Goal:

 To interface the Mini Circuits RF Frequency Counter(FC) Model UFC-6000 with Raspberry Pi on Linux platform. Also to create a User friendly interface, to control the FC with command lines.

Highlights of the Code(script attached):

The  code enables the user to communicate and control different parameters of the UFC like:

1)Frequency Range Selection( for the device to read different frequencies, AutoRange is set by default).

2)Sampling Time (The time intervals for which the data will be retrieved)

3)Read Device Status(Whether the device is reading data or not).

Description of the Code:

HID USB Interfacing by sending byte Values.

 1)Read The Freq or Range 

Reading the Freq is done by reading the 1st and 2nd LCD of the Frequency counter.

1st line containing Range information, 2nd line is the Frequency result

the code should be send is 2

1st byte: 2

The returned 64 byte array is as follows:

1st byte: 2

2nd byte to Byte17 the ascii value of 16 characters of the 1st LCD line

Byte18 to Byte33  the ascii value of 16 characters of the 2nd LCD line

2) Set the Range  

By default Freq Counter is in "AutoRange" mode.

To set the range manually send the code 4

1st byte: 4

2nd byte: the range value. can be any legal range value. for auto range  need to be 255.

the 64 byte array is:

1st byte: 4

3)Set the Sample Time   

By default Freq Counter Sample Time is 1 sec.

you can set the sample time from 0.1 sec and up in step of 0.1 sec.To set the Sample Time send the code 3

1st byte: 3

2nd byte: the sample value in sec double 10.

for example: to set the sample time  to 0.4 sec 2nd byte need to be: 4

the 64 byte array is:

1st byte: 3

These bytes can be changed by changing the values of buffer[0] and buffer[1]  in function /*Send Report to the device*/ in the main program.

The data is written into a .txt file(example attached) and the user can  control the recording of data. The frequency data can now be made to talk to EPICS through slow channels.

The data from the .txt file can be used for error analysis at different sampling periods.

Results:

The interface of the FC with the Pi is now complete.

Plan:

 Make this FC talk to EPICS through slow channels.

I'm currently running a measurement on the PRC.

Please don't interfere with the IFO until it is done. Talk with Alberto if you've been intending to work inside the lab.

Thank you.

From 2PM, Jenne/Den/Koji. Finished at 10:30PM

• General
  • More LCD screens! Wider screens!
    • Allegra - only can handle single head right now, but should prepare for the eventual upgrade of that videocard/whole computer and get 2 monitors.
    • Every workstation should have 2 24" monitors.  We currently have 2 good ones (one on Rossa, one on Pianosa), so we need 6.
  • Remove Control room shelf currently holding OSA 'scopes
  • Adjust both TV shelves so that they're at the same height, ~6" higher than the current left shelf.
    This gives space for stacking the 24" monitors for each computer.
  • Audio system for the signals!!!! Even a crappy one!
         /cvs/cds/ligo/centos5.5/cds/project/gds-2.14.2/Monitors/rockIFO
         /cvs/cds/gds/gds/Monitors/rockIFO
         (really /cvs/cds, not /opt)
    
    
• IOO
  • PZT or Picomotor mounts for PSL/ALS beams
  • ALS on the both arm simultaneously / common/diff ALS scripts
• SUS
  • PRM OPLEV servos are sometimes not stable. (fixed, JCD/DM/KA, 5/2/2012)
  • ETMX oplev - replace 1064nm lens with 632nm lens (KBC037, -100)
• IFO
  • It seems that there is an occasional common-mode power transient in the arm transmissions.
    -> Track down the cause and fix.
  • Fix arm ASS even on CentOS
  • Drift of the green incident axis -> Assess the amount of the drift / replace the mount
  • Calibration of POP22 / AS110
  • PMC/IMC/ARM characterization (loss, finesse, reflectivity, etc)
• CDS
  • Capture OSA signals in CDS (the 'scope TDS1001B has a USB port in the back for connecting to the computer)
  • Transmon (arms) for high and low power
  • POX11 whitening is not toggling the analog whitening???
  • CentOS machines cannot open simulink models properly (get "Bad Link"s everywhere, so you can't do anything useful).
  • Dataviewer and DTT can't connect to framebuilder from CentIOS machines
• Electronics
  • Actuator noise level characterization (coil driver response in V/m & coil driver noise level V/rtHz)
  • Beat box
  • I/Q DFD
  • Improvement of POP22/110/AS110 RF circuits.
• MEDM
  • OL alert in the watch dog screen (this is awesome!) should have small text saying "OL" (done, JCD, 5May2012)
  • Complete 40m overview screen - everything should be clickable with pseudo 3D icons
  • BETTER SUSPENSION SCREEN!!!
  • Script to generate a MEDM tree
  • Resurrect MEDM snapshots
     
  • The LSC screen has some "white" boxes -> investigate and fix them (done, KA, 5/2/2012)
  • Make the LSC control screen (compact) in the vertical arrangement (done, KA, 5/2/2012)
  • The signals of the watch dog screen should go red if any of the WDs are not enabled.
    =>Copy the logic of the signals in LSC screen. (done, KA, 5/2/2012)
  • Remove c1gfd from the cds status screen (done, KA, 5/2/2012)
  • Add "BURT" status indicators on the cds status screen (done, KA, 5/2/2012)
• SCRIPT
  • Locking scripts with integrator triggers / disabling when unlocked
  • Daily diagnosis of the MC spot positions (there must be something already...)
  • Daily/occasional adjustment of the incident axis on the MC
  • Suspension "misalign/restore" script is too wild => make a new script (Done, JCD, 7May2012)
  • IFO_CONFIGURE scripts still do a burt restore, so step the optics.  Need to remove optic alignment from config .snap files, use reg restore script instead.
  • OPLEV/OSEM trending script before the IFO work for diagnosis.
  • Auto-locker for PMC/Arm/etc
• Video
  • If each video screen has a caption, that would be great
  • GUI interface of "videoswitch" Mike!
  • Mouse Jiggler for Zita (called Swinput?)
• Ubuntu
  • burttoday is not aliased in ubuntu. burttoday:      aliased to cd /opt/rtcds/caltech/c1/burt/autoburt/today/
  • ASS doesn't run on Ubuntu!
    ezcawrite: error while loading shared libraries: libca.so: cannot open shared object file: No such file or directory
ezcaswitch: error while loading shared libraries: libca.so: cannot open shared object file: No such file or directory
 

This afternoon, I tried to lock the interferometer again after a few days.

After a couple of failed attempts, and relocks of the MZ, the interferometer stayed locked continuously for about 50 minutes, with arm power of about 92.

I just wanted to check the status of the interferometer so I didn't do any particular measurement in the meantime.

I've done some preliminary modeling to see if there is a good candidate for an IR DARM control signal that is available before the AS55 sign flip. From a DC sweep point of view, ASDC/(TRX+TRY) may be a candidate for further exploration. 

As a reminder, both Finesse and MIST predict a sign flip in the AS55 Q control signal for DARM in the PRFPMI configuration, at a CARM offset of around 118pm.

The CARM offset where this sign flip occurs isn't too far off of where we're currently losing lock, so we have not had the opportunity to switch DARM control off of ALS and over to the quieter IR RF signal of AS55. 

Here are simulated DC DARM sweep plots of our current PRFPMI configuration, with a whole bunch of potential signals that struck me. 

Although the units of most traces are arbitrary in each plot (to fit on the same scale), each plot uses the same arbitrary units (if that makes any sense) so slopes and ratios of values can be read off. 

In the 300 and 120pm plot, you can see that the zero crossing of AS55 is at some considerable DARM offset, and normalizing by TRX doesn't change much about that. "Hold on a second," I hear you say. "Your first plots said that the sign flip happens at around 120pm, so why does the AS55 profile still look bad at 50pm?!" My guess is that, probably due to a combination of Schnupp and arm length asymmetry, CARM offsets move where the peak power is in the DARM coordinate. This picture makes what I mean more clear, perhaps:

Thus, once we're on the other side of the sign flip, I'm confident that we can use AS55 Q without much problem. 

Now, back to thoughts about an interim signal:

ASDC by itself does not really have the kind of behavior we want; but the power out of AS as a fraction of the ARM power (i.e. ASDC/TRX in the plot) seems to have a rational shape, that is not too unlike what the REFLDC CARM profile looks like.

Why not use POPDC or REFLDC? Well, at the CARM offsets we're currently at, POPDC is dominated by the PRC resonating sidebands, and REFLDC has barely begun to decline, and at lower CARM offsets, they each flatten out before the peak of the little ASDC hill, and so don't do much to improve the shape. Meanwhile, ASDC/TRX has a smooth response to points within some fraction of the DARM line width in all of the plots. 

Thus, as was discussed at today's meeting, I feel it may be possible to lock DARM on ASDC/(TRX+TRY) with some offset, until AS55 becomes feasible.

(In practice, I figure we would divide by the sum of the powers, to reduce the influence of the DARM component of just TRX; we don't want to have DARM/DARM in the error signal for DARM)

Two caveats are:

• The slope of this signal actually looks more quadratic than linear. Is this ok/manageable?
• I have not yet made any investigation into the frequency dependent behavior of this thing. Transmission in the denominator will have the CARM pole in it, might get complicated. 

[Code and plots live in /svn/trunk/modeling/PRFPMI_radpressure]

I've added (TRX-TRY)/(TRX+TRY) to the DC DARM sweep plots, and it looks like an even better candidate. The slope is closer to linear, and it has a zero crossing within ~10pm of the true DARM zero across the different CARM offsets, so we might not even need to use an intentional DARM offset. 

We also took this opportunity to re-connect the interlock to the Innolight controller (after it was disconnected for diagnosing the mysterious NPRO self-shutdowns). The diode pump current was dialled down to 0, the interlock wires reconnected, and then the diode current was ramped back up to the nominal 2.1 A. The fan to cool the unit remains mounted in a flaky way as we couldn't locate the frame Chub had made for a more secure mounting solution. 

It seems like the pointing of the beam out of the laser head varies somewhat after the startup - I had to adjust the pointing into the PMC a couple of times by ~1 full turn of the Polaris mount screws, but the IMC has been locked (mostly) for the last ~16 hours.

[Paco, JC]

While changing out one of the N2 tanks today, one of the fitting stripped. This caused a major loss of pressure. I replaced one fitting then realized there was a second leak around the area of the gauge. Paco and I changed this and everything should be back up and running. Thhe interlocks may have been tripped  within the last 2 hours.

The attached plot shows the 30 day trend of the MC3 UL PD signal. The signal dropped to zero at some point but now it is close to the level it was a few weeks ago. There still could be a problem with the cable.

The rest of the MC1,2,3 PD signals looked ok.

Steve showed me how to send an international fax today:

1. Load paper.
2. Dial:   011 - (country code) - number
3. Press START (either the black or color option)
4. wait for the screaming fax noise
5. Done

The new rtcds utility

I have written a new utility for interacting with the CDS RTS/RCG system: "rtcds".  It should be available on all workstations and front-end machines, but certain commands are restricted to run on certain front end machines (build, start, stop, etc.).  Here's the help:

controls@c1lsc ~ 0$ rtcds help
Usage: rtcds <command> [arg]

Available commands:

  build|make SYS      build model
  install SYS         install model
  start SYS|all       start model
  restart SYS|all     restart running model
  stop|kill SYS|all   stop running model
  list                list all models for current host

controls@c1lsc ~ 0$ 

Please use this new utility from now on when interacting with RTS.

I'll be improving and expanding it as we go.   Please let me know if you encounter any problems.

For the sake of future users, I have decided to periodically add tips and tricks in using COMSOL that I have figured out, most probably after hours of circuitous efforts. They will always be listed under the new COMSOL Tips category.

Today's topic: Intrusions

COMSOL has a very user-friendly interface for taking objects from 2D to 3D using the "extrusion" feature. But suppose one wants to design an object which contains screw holes or some other indentation. I've found that creating "punctures" in COMSOL is either impossible or very complicated.

Instead, COMSOL encourages users to always "add" to the object. In other words, one must form the lowest level first, then build layers sequentially on top using new work plane and boolean difference operators. This will probably be a bit clearer with an example:

1) First, create the planar projection in a work plane:

2) Extrude the first layer only in the regular fashion:

 3) Add a new work plane which is offset in the z-direction to the deepest point of the intrusion.

 4) Now, create the shape of the intrusion in this new work plane.

5) Use the Boolean "Difference" to let COMSOL know that, on this plane, the object has a hole.

 6) Extrude once more from the second work plane to complete the intrusion.

 An entry on the 40m wiki page might serve you better, and be easier to sift through once all is said and done

I set up instant green oplevs for ITMs.

A green laser pointer has been set on each end table. It illuminates the ITM center. The beam goea through the ETM substrate.
The reflected green beam returns to the ETM if the ITMs are aligned. Even though the reflected beam to the end is too big, this can
be a rough reference for each ITM.

Note: The green laser pointer at the ETMX were borrowed from Frank. We must return it to him when we finish the work.

--Apologies for the late post--

I was at the PSL table taking an inventory of the components for a while after Koji, Steve, and Kiwamu were there. I set the HEPAs back to 20% when I left (assuming that they were turned up when the compartment was opened).

I did a quick sweep of the lab to find out what hardware has already been acquired for the X-end table upgrade. The attached PDF is an inventory check in the spirit of this elog.

Some things we have to decide:

• Are we okay with using the old green coloured faraday mount for the IR faraday? I have in hand a piece identical to the one used at the Y-end for the green faraday, that is red in colour, so I guess we can switch this out.
• The way in which the doubling oven is currently mounted at the X-end is using some posts cobbled together. The Y-end looks to have a custom mount machined for it (see Attachment #2). Do we want to go ahead and get something like this done?
• I suppose it is okay to reuse all the old optics (mirrors, lenses, harmonic separators) and PDs? It may be that we need to order som extra mirrors/lenses/posts (this will become clear once I do the layout)

I have not gotten around to planning the layout or doing drawings. I will try and first work through a mode-matching solution to make sure we have all the required lenses. It may be that we need some 1" or 2" mirrors as well. The beam from the lightwave NPRO is quite elliptical, but we have a number of cylindrical lenses in hand already if we decide we want to use these, so I guess we don't have to worry about this...

This is quite a preliminary list, and I will add/update over the coming days as I do more detailed planning, but have I missed out anything obvious?

Its not a good idea to use green mounts with green lasers. Steve should be able to get another copy of the EY doubler mount made up if we really don't have another one sitting in the Manasa end table box which Koji mentioned.

I located the second doubler mount, it was sitting inside a cabinet along the Y-arm. So this will not have to be machined. The doubling oven mount is black in colour.

So as things stand now, the only thing that needs to be machined is a non-green mount for the IR faraday (IO-5-1064-HP) - is it possible to just coat the existing mount with a different color? I've got a drawing for this part ready, but it seems unnecessary to machine the whole thing from scratch when only the color is an issue. Steve was talking about dipping this in some sort of solution and taking the green off. But if this isn't possible, I'll send Steve the drawings tomorrow so that he can place the order with the machine shop...

I will work on the mode-matching calculations over the next couple of days to make sure we have all the mirrors and lenses we need.

Our online subtraction filters for PRC angle and MC length were trained on the raw ADC signals, so I've inverted the filters that Rana installed in the PEM filter banks in the OAF signal conditioning filter banks (C1:OAF-WIT_STS1X, etc.)

It's not perfect, since the inversion would be unstable, and thus needs a low pass. I used an ELP at 800Hz. The error in the inversion is then something like half a degree at 5Hz, which is the highest frequency we really ever subtract at. It should be ok.

[Paco, Anchal]

- Started zoom stream; thanks to whoever installed it!
- Spent some time trying to understand how anything we did last thursday lead to the sensing matrix change, but still cannot figure it out. 
- Tracking back on our actions, at ~10:30 we ran burt Restore with the 08:19/.*snap and in lack of a better suspect, we blame it on that action for now.

# ARM locking??
- Reading (not running) the scripts/XARM/lockXarm.py script and try to understand the workflow. It is pretty confusing that the result was to lock Yarm last time.
- It looks like this script was a copy of lockYarm.py, and was never updated (there's a chance we ran it for the first time last thursday)
- *Is there a script to lock the Arms?* Or should we write one? To write one, we first attempt a manual procedure;
    1. No need to change RFPD InMTRX
    2. All filters inputs / outputs are enabled 
    3. Outputs from XARM and YARM in the Output matrix are already going to ETMX and ETMY
      - Maybe we can have the ARM lock engage by changing the MC directly?
    4. Change C1:SUS-MC2_POS_OFFSET from -38 to -0, and enable C1:SUS-MC2_POS_OFFSET_ON
    5. Manually scan MC2_POS_OFFSET to 250 (nothing happens), then -250, then back to -38 (WFS1 PIT and YAW changed a little, but then returned to their nominal values)
      - Or maybe we need to provide the right gain...
    6. Disabled C1:SUS-MC2_POS_OFFSET_ON (back to nominal state)
    7. Look into manually changing C1:LSC-XARM_GAIN;
      From the command line using python:
      >> import epics
      >> ch_name = 'C1:LSC-XARM_GAIN'
      >> epics.caput(ch_name, 0.155) # nominal = 0.150
      - Could be unrelated, but we noted a slow spike on C1:PSL-FSS_PCDRIVE (definitely from before we changed anything)
      - Still nothing is happening
    8. Changed the gain to 0.175, then back to 0.150, no effect... then 0.2, 0.3 ...
      - Stop and check SUS_Watchdogs (should not have changed?) and everything remains nominal
      - Revert all changes symmetrically.
      - Could we have missed enabling FM1?
      - Briefly lost MC lock, but it came back on its own (probably unrelated)

- Wrap it up for the day. In summary; no harm done to our knowledge.

For the arm locking, the "Restore Xarm (XARM POX)" script from the "IFO_CONFIGURE" MEDM screen should get you there (I just checked it and it works fine). It is worth getting a hang of the PDH signal chain (read what the script is doing and map it to the signal chain) so you get a feel for where there may be offsets, saturations, what the trigger logic is etc. The LSC overview screen is supposed to be pretty intuitive (if you think it can be improved, I'd love to hear it but please don't change it without documenting) and there are also the webviews of the simulink models (these are RO so feel free to click around, for the LSC the c1lsc model is the relevant one).

We've known for years that the IMC WFS sensing chain is pointlessly bad, but until recently, we haven't thought it was worth it to fix.

There are problems in all parts of the chain:

1. The WFS Photodetectors oscillate ~200 MHz when turned up to full gain. Diego and I confirmed this today by measuring the RF spectrum of the signals going into the WFS demod boards and seeing the oscillation change (not much) with RF gain. I recommend we switch the heads into the full gain mode (turn all of the attenuators OFF). At the moment we are operating with the 2dB and 8dB attenuators ON.
2. The demod board has some bad gain allocation and noisy opamps.
3. The whitening board has too much up/down of gain with noise injection along the way. And the range cannot fill up the ADC.

Attachment #1: spectra of the phase noise between LO and IFO output fields sensed using the RF44 signal.

• Measurement setup:
  • LO an IFO fields are combined on a beamsplitter, with ~60% mode-matching efficiency.
  • One port of the BS goes to a DCPD.
  • The other port goes to an RF sensing photodiode, PDA10CF. The spec-ed dark noise NEP is ~12 pW/rtHz at 1.6 um, (so let's say 25 pW/rtHz) and transimpedance is 5kohms into a 50 ohm load. We can convert this to an equivalent sensing noise at the error point of this loop, though it's more likely that the electronics (demod, ADC etc) noise downstream dictate the sensing limit, which I measure by blocking light on the photodiode.
• The demodulation is done on one of the newly received D0902745 boards - this was just a more compact setup than many cascaded minicircuit components. We don't have the hardware to package this into a chassis to shield against electronics noise pickup yet, so I'm using a bench supply to power this for now (via a voltage regulation board, D1000217.
• "Dark Noise" = ASD with no light incident on the photodiode. "LO field only" = ASD with only the LO field incident on the photodiode.
• The "Dark noise" trace and "LO field only" traces are converted from cts/rtHz to rad/rtHz by noting that when the Michelson is locked on a dark fringe, the demodulated RF44 quadratures have a pk-pk amplitude of ~160 cts (corresponding to pi radians of phase shift). Since in these conditions the demodulated quadratures do not undergo any fringe wrapping, I converted the spectra by simple multiplication.
• For the "RF44 open loop" trace:
  • The DC offset in the demodulated signal (due to the RF44 signal from the LO field only) is digitally compensated, so that the fringing has (roughly) zero offset.
  • The Michelson was locked on a dark fringe, and the demodulated RF44 quadratures were monitored for ~5 mins. Then arctangent (specifically, arctan2 to get the correct quadrant in the IQ plane) of the two signals was taken to convert the fringing signals to phase noise.

Closing a feedback loop:

• Since it seems like we are sensing a signal (below ~1kHz at least), I tried to close a feedback loop (modelled loop shape shown in Attachment #2, it's just a model because I have to guess what the sensing and actuation gains are, and they're both assumed to be flat, digital delays etc aren't accounted for). I've also added the inferred loop gain by taking the ratio of the in loop and unsuppressed ASDs (though of course I don't account for the flat sensing noise at higher frequencies). At least qualitatively, things line up...
• While I can get the light level on the DCPD to stabilitze somewhat, the loop is not at all stable, and the suppression isn't very good at all.
• Not sure how meaningful any of the spectra with the loop closed are, but FWIW, I've put in the spectra of the demodulated RF44 signals with the loop engaged (RF44 Q is used as the error signal). A clear problem is evident at ~120 Hz, and the forest of lines isn't helping for sure. Also unclear to me why the I and Q signals don't have the same profile at low frequencies.

Conclusions/Questions:

1. What is the reason for the huge forests of lines in the "RF44 open loop" ASD, that are absent in the other two traces? If this were electrical pickup, it should be there in all three traces?
2. Is the shape of the spectrum reasonable? The roll-off above ~5 Hz doesn't seem quite steep enough to be seismic noise from the suspensions. Can it really be that the Michelson dark field has such high phase noise?
3. How can we get this scheme to give us cleaner sensing?
4. The actuation chain was verified to work fine with the single bounce beam from an ITM interfered with the LO field, and using the DC light level as an error signal and locking to the half-fringe point. So the problem is not due to insufficient actuation range. Seems like the error signal is so polluted with these forests of lines that even though there is some suppression of the error signal at low frequencies, the unsuppressed noise is still significant. I can't solve the problem by simply increasing the loop gain...
5. It is not shown here, but with only the LO field incident on the RFPD, I see a drift of the demodulated signals on the ~5 minute timescale - is this just due to fiber length change? If so, this is potentially problematic, as on long time scales, the true zero of the error point of the servo would be changing on the ~5 minute timescale. This would be true even for the final suspended scheme - if the path length between PR2 and the homodyne BS changes by some microns, we would have to correct this at DC?

Summary:

I've been looking into the cross-coupling from the SRCL loop control point to the Michelson error point.

[Attachment #1] - Swept sine measurement of transfer function from SRCL_OUT_DQ to MICH_IN1_DQ. Details below.

[Attachment #2] - Attempt to measure time variation of coupling from SRCL control point to MICH error point. Details below.

[Attachment #3] - Histogram of the data in Attachment #2.

[Attachment #4] - Spectrogram of the duration in which data in #2 and #3 were collected, to investigate the occurrance of fast glitches.

Hypothesis: (so that people can correct me where I'm wrong - 40m tests are on DRMI so "MICH" in this discussion would be "DARM" when considering the sites)

• SRM motion creates noise in MICH.
• The SRM motion may be naively decomposed into two contributions -
  • Category #1: "sensing noise induced" motion, which comes about because of the SRCL control loop moving the SRM due to shot noise (or any other sensing noise) of the SRCL PDH photodiode, and
  • Category #2: all other SRM motion.
• We'd like to cancel the former contribution from DARM.
• The idea is to measure the transfer function from SRCL control point to the MICH error point. Knowing this, we can design a filter so that the SRCL control signal is filtered and summed in at the MICH error point to null the SRCL coupling to MICH.
• Caveats/questions:
  • Introducing this extra loop actually increases the coupling of the "all other" category of SRM motion to MICH. But the hypothesis is that the MICH noise at low frequencies, which is where this increased coupling is expected to matter, will be dominated by seismic/other noise contributions, and so we are not actually degrading the MICH sensitivity.
  • Knowing the nosie-budget for MICH and SRCL, can we AC couple the feedforward loop such that we are only doing stuff at frequencies where Category #1 is the dominant SRCL noise?

Measurement details and next steps:

Attachment #1

• This measurement was done using DTT swept sine.
• Plotted TF is from SRCL_OUT to MICH_IN, so the SRCL loop shape shouldn't matter.
• I expect the pendulum TF of the SRM to describe this shape - I've overlaid a 1/f^2 shape, it's not quite a fit, and I think the phase profile is due to a delay, but I didn't fit this.
• I had to average at each datapoint for ~10 seconds to get coherence >0.9.
• The whole measurement takes a few minutes.

Attachments #2 and #3

• With the DRMI locked, I drove a sine wave at 83.13 Hz at the SRCL error point using awggui.
• I ramped up the amplitude till I could see this line with an SNR of ~10 in the MICH error signal.
• Then I downloaded ~10mins of data, demodulated it digitally, and low-passed the mixer output.
• I had to use a pretty low corner frequency (0.1 Hz, second order butterworth) on the LPF, as otherwise, the data was too noisy.
• Even so, the observed variation seems too large - can the coupling really change by x100?
• The scatter is huge - part of the problem is that there are numerous glitches while the DRMI is locked.
• As discussed at the meeting today, I'll try another approach of doing multiple swept-sines and using Craig's TFplotter utility to see what scatter that yields.

Attachments #2

• Spectrogram generated with 1 second time strides, for the duration in which the 83 Hz line was driven.
• There are a couple of large fast glitches visible.

I believe the aLIGO style invac dsub cables and the conventional 40m ones are incompatible.
While the aLIGO spec is that Pin1 (in-vac) is connected to the shield, Pin13 (in-vac) is the one for the conventional cable. I still have to check if Pin13 is really connected to the shield, but we had trouble before for the IO TTs https://nodus.ligo.caltech.edu:8081/40m/7864.
(At least one of the existing end cables did not show this Pin13-chamber connection. However, the cables OMC/IMC chambers indicated this feature. So the cables are already inhomogenious.)

- Which way do we want to go? Our electronics are updated with aLIGO spec (New Sat amp, OMC electronics, etc), so I think we should start making the shift to the aLIGO spec.

- Attachment Top: The new coil drivers can be used together with the old cables using a custom DB25 cable (in-air).

- Attachment Mid: The combination of the conventional OSEM wiring and the aLIGO in-vac cable cause the conflict. The pin1 which is connected to the shield is used for the PD bias.

- Attachment Bottom: This can be solved by shifting the OSEMs by one pin.

Notes:
o The aLIGO cables have 12 twisted pair wires, but paired signals do not share a twisted pair.
   --- No. This can't be solved by rotating the connectors.
o This modification should be done only for the new suspension.
   --- In principle, we can apply this change to any SOSs. However, this action involves the vent. We probably want to install the new electronics for the existing suspensions before the vent.
o ^- This means that we have to have two types of custom DB25 in-air cables.
   --- Each cable should handle "Shield wire" from the sat amp correctly.

Related Links:

Active TT Pin Issue
https://nodus.ligo.caltech.edu:8081/40m/7863
and the thread

Hacky solution
https://nodus.ligo.caltech.edu:8081/40m/7869

Photo
https://photos.google.com/u/1/album/AF1QipOEDi7iBdS4EHcpM7GBbv9l6FiJx-Tkt1I2eSFA
Active TT Pin Swapping (December 21, 2012)

TT Wiring Diagram (Wiki)
https://wiki-40m.ligo.caltech.edu/Suspensions/Tip_Tilts_IO

Koji and I noticed that there was a comb* of peaks in the MC and FSS at harmonics of ~37 kHz. Today I saw that this shows up (at a much reduced level) even when the input to the MC board is disconnected.

It also shows up in the PMC. At nominal gains, there is just the 37 kHz peak. After tweaking up the phase shifter settings, I was able to get PMC servo to oscillate; it then makes a comb, but the actual oscillation fundamental is 1/3 of 37 kHz (some info on Jenne from elog 978 back in 2008).

Not sure what, if anything, we do about this. It is curious that the peak shows up in the MC with a different harmonic ratio than in the PMC. Any theories?

Anyway, after some screwing around with phase and amplitude of the RF modulation for the PMC from the phase shifter screen**, I think the gain is higher in the loop and it looks like the comb is gone from the MC spectrum.

Another clue I notice is that the PCDRIVE mad times often are coincident with DC shifts in the SLOWDC. Does this mean that its a flakiness with the laser? While watching the PCDRIVE output from the TTFSS interface board on a scope, I also looked at MIXER mon. It looks like many of the high noise events are associated with a broadband noise increase from ~50-140 kHz, rather than some specific lines. Don't know if this is characteristic of all of the noisy times though.

* this 'comb' had several peaks, but seem not be precise harmonics of each other: (f3 - 3*f1)/f3 ~ 0.1%

** I think we never optimized this after changing the ERA-5 this summer, so we'd better do it next.

 *** UPDATE: the second plot show the comparison between the new quiet and noisy states. Its just a broad bump.

[Paco, Yuta]

After several hours of unattended IFO, we realigned the IFO and somehow BH55_Q error signal looked better, LO_PHASE locking was more robust, and we could lock FPMI BHD.

Sensing matrix:
 - Attached #1 is the sensing matrix with FPMI BHD locked, with LO_PHASE locked with BH55_Q using AS4, and below is the calibrated one.

Sensing matrix with the following demodulation phases (counts/m)
{'AS55': -168.5, 'REFL55': 92.32, 'BH55': -110.0}
Sensors       DARM @307.88 Hz           CARM @309.21 Hz           MICH @311.1 Hz           LO1 @315.17 Hz           
AS55_I       (+0.43+/-2.22)e+11 [90]    (+5.26+/-1.26)e+11 [0]    (-0.15+/-5.88)e+10 [0]    (+0.05+/-1.94)e+09 [0]    
AS55_Q       (-3.73+/-0.19)e+11 [90]    (-0.09+/-1.06)e+11 [0]    (+0.21+/-6.82)e+09 [0]    (-0.24+/-2.41)e+08 [0]    
REFL55_I       (+0.08+/-1.17)e+12 [90]    (+3.14+/-0.07)e+12 [0]    (-0.01+/-1.31)e+11 [0]    (+0.07+/-1.03)e+09 [0]    
REFL55_Q       (+0.51+/-1.09)e+10 [90]    (+1.80+/-2.35)e+10 [0]    (+0.01+/-1.44)e+09 [0]    (-0.79+/-5.41)e+07 [0]    
BH55_I       (+1.20+/-0.34)e+11 [90]    (+0.26+/-1.07)e+11 [0]    (-0.04+/-1.33)e+10 [0]    (-1.07+/-1.82)e+09 [0]    
BH55_Q       (+1.12+/-1.52)e+11 [90]    (-3.40+/-1.98)e+11 [0]    (-0.01+/-4.16)e+10 [0]    (-5.55+/-1.66)e+09 [0]    
BHDC_DIFF       (+6.95+/-0.25)e+11 [90]    (+0.01+/-1.60)e+11 [0]    (-0.70+/-4.49)e+09 [0]    (+4.24+/-4.14)e+08 [0]    
BHDC_SUM       (+7.06+/-2.64)e+10 [90]    (-0.32+/-3.24)e+10 [0]    (+0.05+/-4.26)e+09 [0]    (+1.30+/-6.33)e+08 [0]    

BH55_Q:
 - We are not sure why BH55_Q error signal got better. Peak to peak amptidue of BH55_Q when LO_PHASE is not locked is at around 800 (even if LO_PHASE locking cannot be stably locked), but when we couldn't lock LO_PHASE stably, it was noisier. This suggests that BHD alignment is not bad.
 - Attachment #2 shows the spectrum of BHDC_DIFF, BH55_Q (measured at LO_PHASE_IN1) and AS55_Q when FPMI is locked with AS55_Q, and LO_PHASE is locked with BH55_Q. Dashed darker curves are when we could not lock LO_PHASE stably. You can see broad noise in BH55_Q at around 60 Hz and its harmonics when it is noisy, but they are not present when LO_PHASE can be locked stably. Also, AS55_Q stays the same, which suggests that the cause is not in FPMI to AS55, but in BHD path to BH55.

Sensitivity comparison with different LO_PHASE locking actuator:
  - We compared FPMI sensitivity with LO_PHASE locked with LO1 (red) vs with AS4 (orange). Didn't change, as expected (Attachment #3).

Next:
 - Investigate what is causing noisy BH55. Is it FPMI alignment, BHD alignment, suspensions in LO/AS paths, or electronics?
 - Try locking LO_PHASE with an offset to BH55_Q to see if BHD_DIFF sensitivity to DARM changes, and to see if we can reduce BHD_DIFF dark noise contribution to FPMI sensitivity
 - Try BH55+audio and BH44 to lock LO_PHASE.
 - PRMI and PRFPMI

[Yutaro, Koji]

Recently "EPICS Freeze" is so frequent and the normal work on the MEDM screen became almost impossible.

As a part of the investigation, all 19 realtime processes were stopped in order to see any effect on the probem.

IN FACT, when the realtime processes were absent (still slow machines were running), frequency of EPICS Freeze
became much less. This might mean that the issue is related to the data collection of the slow channels. We need more investigation.

After the testing, all the processes were restored although it was not so straghtforward. Particularly, c1sus DAC had an error which was
not visible from the CDS Status screen. We noticed it as suspension damping was not effective on any of the vertex suspensions.
This has been solved by restarting c1x02 process.

In preparation for the ASS debugging, I decided to check out the beam path on the EY table. In order to be able to do this, I had to setup the POY locking to trigger on AS110 instead of TRY (as is usual for this kind of debugging). Then I could poke an IR card in the beam path without destroying the lock.

There are two irides in the beam path immediately between the vacuum window and the harmonic separator that splits off the IR and green beams. I found that the beam was in fact getting clipped on both of them. It was also somewhat off center on a 2" beamsplitter that sends half of the light to the QPD (currently decommissioned). The purpose of these irides are (I think) to eliminate some ghost reflections of the green beam and also the Oplev beam. I opened up the irides until I felt that there wasn't any more clipping of the IR beam, but the appropriate ghost beams were still getting caught.

I also re-aligned the beam onto the TRY Thorlabs PD so as to better center it on the active area. In summary, the result of this work was that the TRY level went from ~0.6 to ~0.93. There may still be some scope for optimizing this - I tried running the Y-arm ASS scripts, and already, the loops don't run away any more. I'll do the systematic analysis of the servo anyways. But given that the IMC Trans lev el used to be ~15,500 counts and is now ~14,500 counts, I think ~7% drop in TRY level is in line with what we "expect" (assuming the pre-power-degradation TRY level was 1.000).

Note that these irides were installed (I think) by Yuki, and so cannot explain the ASS anomalies of July 2018 (i.e. it does not exonerate in-vacuum clipping of the beam, as Koji had already verified that the in-air path was clean back then).

The local backup seems working fine again. But I found that megatron is down and this is a real issue. This should be fixed at the earliest chance.

It seems that the local backup has been successfully taken this morning.

controls@nodus|backup> tail /opt/rtcds/caltech/c1/scripts/backup/localbackup.log
2021-12-19 07:00:01,146 INFO       Updating backup image of /cvs/cds
2021-12-19 07:00:01,146 ERROR      External drive not mounted!!!
2021-12-20 07:00:01,255 INFO       Updating backup image of /cvs/cds
2021-12-20 07:00:01,255 ERROR      External drive not mounted!!!
2021-12-21 07:00:01,361 INFO       Updating backup image of /cvs/cds
2021-12-21 07:00:01,361 ERROR      External drive not mounted!!!
2021-12-22 07:00:01,469 INFO       Updating backup image of /cvs/cds
2021-12-22 07:00:01,470 ERROR      External drive not mounted!!!
2021-12-23 07:00:01,594 INFO       Updating backup image of /cvs/cds
2021-12-23 07:19:55,560 INFO       Backup rsync job ran successfully, transferred 338425 files.

However, I noticed that the autoburt has been stalled since Dec 6 (I used to check how the backup is up-to-date using the autoburt snapshots)

Dec>pwd
/opt/rtcds/caltech/c1/burt/autoburt/snapshots/2021/Dec
Dec>ls -l
total 24
drwxr-xr-x 26 controls controls 4096 Dec  1 23:07 1
drwxr-xr-x 26 controls controls 4096 Dec  2 23:07 2
drwxr-xr-x 26 controls controls 4096 Dec  3 23:07 3
drwxr-xr-x 26 controls controls 4096 Dec  4 23:07 4
drwxr-xr-x 26 controls controls 4096 Dec  5 23:07 5
drwxr-xr-x 19 controls controls 4096 Dec  6 16:07 6

There are a bunch of errors in the log file as follows, but maybe this is not an issue

controls@nodus|burt> pwd
/opt/rtcds/caltech/c1/burt
controls@nodus|burt> tail burtcron.log
!!!  ERROR !!! Target c1supepics Snapshot file inconsistent with Request file
!!!  ERROR !!! Target c1tstepics Snapshot file inconsistent with Request file
!!!  ERROR !!! Target c1x10epics Snapshot file inconsistent with Request file
!!!  ERROR !!! Target c1aux Snapshot file inconsistent with Request file
!!!  ERROR !!! Target c1dcuepics Snapshot file inconsistent with Request file
!!!  ERROR !!! Target c1iscaux Snapshot file inconsistent with Request file
!!!  ERROR !!! Target c1iscepics Snapshot file inconsistent with Request file
!!!  ERROR !!! Target c1losepics Snapshot file inconsistent with Request file
!!!  ERROR !!! Target c1psl Snapshot file inconsistent with Request file
!!!  ERROR !!! Target c1susaux Snapshot file inconsistent with Request file

The real issue seems that megatron is down. It has a lot of house keeping jobs on corn including the N2 pressure alert.
https://wiki-40m.ligo.caltech.edu/Computers_and_Scripts/CRON
This needs to be fixed at the earliest chance.

It turned out that the UPS installed on Nov 22 failed (cf https://nodus.ligo.caltech.edu:8081/40m/16479 ). As a fact, it was alive just for 2 weeks!

The APC UPS unit indicated F06. According to the manual (https://www.apc.com/shop/us/en/products/APC-Power-Saving-Back-UPS-Pro-1000VA/P-BR1000G), F06 means "Relay Welding" and can not be fixed by a user. Resetting the UPS eliminated the error, but I didn't want to have the same issue while no one is in the lab, I moved the megatron power source from the UPS to the power strip on 1Y7. So, megatron is currently vulnerable to a power glitch.

After the power cords were restored, megatron eventually recovered ssh terminals. I manually ran autoburt.cron at 16:50 so that the latest snapshot is taken.

 Electronic components should be ISOLATED as they are installed on the optical tables.

This is essential to avoid ground loops, 60 Hz and harmonic peaks in the spectrum. We have just got some made.

Please only use it for this reason. Earlier black delrin base plates were used up in not needed places.

The anodized Aluminum base plates with magenets certainly will conduct.

Today I was working on RF distribution box.

So far I almost finished to electronically isolate voltage regulators from the box wall by inserting mica sheet, sleeve, and washers.

The problem I found is the resistance between wall and the voltage regulator is order of M ohms

I checked my isolation (mica sheet and sleeve and washer) but there is no problem there.

But I found that the power switch is not completely isolated from the wall.( around 800 kohm)

and that the resistance between the regulator and the wall is smaller for the regulator closer to the power switch

and greater for the regulator less closer to it.

So I think we need to put washer or sleeve to isolate the powersitch electronically from the box wall.

Suresh or I will fix this problem

[ To Suresh, I can finish the isolation when I come tomorrow. Or you can proceed to finish isolation.]

I figured out the problem with ALS from yesterday. While the model was just fine, the medm screens were not checked if they were reading the correct channel names. 

The channel names of the ALS input matrix elements had changed when the coarse channels were deleted from the c1als model. So the error signals were not reaching the servo modules as expected. This is why I was not able to make sense as to what the ALS was doing. 

All is fixed now and should be back to normal

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

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

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

Apr 16, 2019
Borrowed two laser goggles from the 40m. (Returned Apr 29, 2019)
Apr 19, 2019
Borrowed from the 40m:
- Universal camera mount
- 50mm CCD lens
- zoom CCD lens (Returned Apr 29, 2019)
- Olympus SP-570UZ (Returned Apr 29, 2019)
- Special Olympus USB Cable (Returned Apr 29, 2019)

Optical chopper borrowed from CryoLab to 40m

https://nodus.ligo.caltech.edu:8081/Cryo_Lab/2458

I characterized the black Ithaca 1201 pre-amp that we had sitting in the racks. It works fine and the input referred noise is < 10 nV/rHz. I also checked that the filter selection switches on the front panel did what they claim and that the gain knob gives us the correct gain.

For comparison I have also included the G=100, 1000 input referred noise of one of the best SR560 that we have (s/n 02763) in the lab. Above a few Hz, the SR560 is better, but for low frequency measurements it seems that the 1201 is our friend.

As with the SR560, you don't actually get low noise performance for G < 100, due to some fixed output noise level.

Steve:  sn48332 of Ithaca 1201

Jenne and I need our jackets. We removed them from the Rb clock.
Thanks for making them warm. Probably a Scotland sweater would fit.

 Thanks for the loan guys.  I do have a lot of warm weather clothing at home that is not so necessary in the California climate.  I will find some suitable attire for the Rb clocks there.

I finally made good on the LIFE TIME WARRANTY on the ancient, Jamie-made 1811 power supply with the faulty switch:

Back to fully working form.  Hopefully I'll still be around the next time it breaks in 16 years.