This AmScope microscope would have 3.5x-180x magnification, calibratable measurement function, 5MP picture and good working distance to work on printed circuit boards.

I don't know if anyone looked at the time series (not trend) or spectrum of the Microphone after installation, but it looks bad and featureless to me. Is the Microphone broken?

This shows the spectrum from early this morning and again from tonight. You can see that it is bi-stable in its noise properties. This thing is busted; we're now removing it from the PSL so that it doesn' light it self on fire.

I had noticed something wonky with the microphone, but neglected to elog it. I had tested it after installation by playing a sine wave from my laptop and looking at the signal on the PSL table, it worked fine. But you can see in the attached minute trend plot that the signal characteristics changed abruptly ~half a day after installation, and never quite recovered.\

and the song remains the same...

the version of SVN on these workstations is ahead of the one on the other workstations so now we can't do 'svn up' on any of the Ubuntu12 machines. One allegra and optimus I get this error:

controls@allegra|GWsummaries> svn up
Updating '.':
svn: E180001: Unable to connect to a repository at URL 'file:///cvs/cds/caltech/svn/trunk/GWsummaries'
svn: E180001: Unable to open an ra_local session to URL
svn: E180001: Unable to open repository 'file:///cvs/cds/caltech/svn/trunk/GWsummaries'

I'm not sure if its possible to downgrade our chans repo back to the old one, but I highly recommend that no one do 'svn upgrade' in any of our repos until we remove all of the Debian installs in the 40m lab or hire a full-time sysadmin.

Re-aligned the beam going into the PMC today around 5 PM. I noticed that its all in pitch and since I moved both of the mirrors by the same amount it is essentially a vertical translation.

I wonder if the PMC is just moving up and down due to thermal expansion in the mount? How else would we get a pure vertical translation? Need to remember next time if the beam goes up or down, and by how many knob turns, and see how it correlates to the lab temperature.

Rana motivated me to take a step back and reframe the objectives and approach for this project, so I am collecting some thoughts here on my understanding of it. As I write this, some things still remain unclear to me, so I am leaving these as questions here for me to think about...

Objectives: 

1. The PSL is locked to the IMC cavity - but at frequencies near 1 Hz, the laser frequency is forced to follow the IMC cavity length fluctuations, even though the free-running PSL frequency noise at those frequencies is lower. This excess is also imprinted on the arms when locked to the IR. We would like to improve the situation by feeding back a portion of the MC PDH error signal to the cavity length actuator to stabilize the MC cavity length at low frequencies. Moreover, we would like this loop to not imprint additional control noise in the arm control signals, which is a problem we have observed with the existing MCL loop. 
    
2. The borader goal here is to use this project as a case study for designing the optimal loop and adaptive feedback. Can we come up with an algorithm, which takes
   • A model of our system (made with measured data where possible)
   • A list of our requirements (e.g. in this case, frequency noise requirements in various frequency bands, smooth crossovers between the various loops that enable locking the PSL to the IMC cavity and avoid injecting excess control noise into the plant)

and come up with the best loop that meets all our rquirements? What constitutes the "best" loop? How do we weight the relative importance of our various requirements? 

Proposed approach:

For the specific problem of making the MCL feedback loop better, the approach I have in mind right now is the following:

1. Build a model of the 40m IMC loop. Ultimately the performance of the loop we implement will depend on the transfer function from various additive noise sources and disturbances in the feedback loop (e.g. electronics noise) to the output (i.e. laser frequency). Building an accurate model will allow us to quantify the performance of the proposed control loop, and hence, optimize it with some algorithm. I did some work on a simplistic, purely analytical model of the two MC loops (MCF and MCL), but Rana pointed out that it is better to have something more realistic for this purpose. I have inherited his Simulink models, which I will now adapt to reflect the 40m topology. 
2. Come up with a list of requirements for the MCL controller. Some things that come to mind:
   • Reduce the arm control signal spectral amplitude below 20 Hz
   • Not increase the arm control signal spectral amplitude above 20 Hz
   • Crossover smoothly with the FSS slow temperature control loop and the MCF loop. 
   • What factor of suppression are we looking for? What is achievable? Once I build the model, it should shed some light on these..
   • Is the PMC a more stable frequency reference than the NPRO crystal at low frequencies? This measurement by Koji seems to suggest that it isn't (assuming the 1e4 product for the NPRO free-running frequency noise)..
3. Once we have a model and a satisfactory list of requirements, design a control loop that meets these using traditional techniques, i.e. desired tracking error in the control band of 0.1-20 Hz (is this possible? The model will tell us...), gain and phase margin requirements etc. But this need not necessarily be the optimal controller that meets all of our requirements
4. Optimize the controller - how? Can we define an objective function that, for example, rewards arm control signal suppression and penalizes injection of control noise, and just fminsearch in the [z,p,k] parameter space of the controller? Is there a smarter way to do this?
5. Can this algorithm be adaptive, and optimize the controller to adapt to prevailing seismic conditions for example? Is this the same as saying we have a model that is accurate enough for us to predict the response of the plant to environmental disturbances? 

My immediate goal is to have the Simulink model updated.

Thoughts/comments on the above will be appreciated...

More testing of fb1 today.  DAQ DOWN UNTIL FURTHER NOTICE.

Testing Wednesday did not resolve anything, but Jonathan Hanks is helping.

In working on automatic DARM loop design, we have this code:

https://git.ligo.org/rana-adhikari/ModernControls/tree/master/OptimalFeedback/GlobalCost

the things in there like mkCost*, etc. have examples of the cost functions that are used. It may be useful to look at those and then make a similar cost function calculation for the MCL/MCF loop.

I was able to bring back svn 1.6 formatting to /cvs/cds/caltech/chans by doing the following on nodus:

Note that I used the http address for the repository. The svn repository doesn't live at file:///cvs/cds/caltech/svn anymore; all of our checkouts (e.g. in the scripts directory) use http to get the one true repo location, regardless of where it lives on nodus' filesystem. (I suppose we could also use https://nodus.martian:30889/svn to stick to the local network, but I don't think we're that limited by the caltech network speed)

Presumably, at some point we will want to introduce a newer operating system into the 40m, as ubuntu 12.04 hits end-of-life in April 2017. Ubuntu 16.04 includes svn 1.8, so we'll also hit this issue if we choose that OS. 

Aside from the svn issues, this directory (/cvs/cds/caltech/chans) only contains pre-2010 channels. Filters and DAQ ini files currently live in /opt/rtcds/caltech/c1/chans, which is not under version control. It's also not clear to me why summary page configurations should be kept in this /cvs/cds place.

True - its an issue. Koji and I are updating zita into Ubuntu16 LTS. If it looks like its OK with various tools we'll swap over the others into it. Until then I figure we're best off turning allegra back into Ubuntu12 to avoid a repeat of this kind of conflict. Once the workstations in the LLO control room are running smoothly on a new OS for a year, we can transfer into that. I don't think any of us wants to be the CDS beta tester for DV or DTT.

Just to be clear, since there seems to be some confusion, the SVN issue has nothing to do with Debian vs. Ubuntu.  SVN made non-backwards compatible changes to their working copy data format that breaks newer checkouts with older clients.  You will run into the exact same problem with newer Ubuntu versions.

I recommend the 40m start moving towards the reference operating systems (Debian 8 or SL7) as that's where CDS is moving.  By moving to newer Ubuntu versions you're moving away from CDS support, not towards it.

No, not confused on that point. We just will not be testing OS versions at the 40m or running multiple OS's on our workstations. As I've said before, we will only move to so-called 'reference' systems once they've been in use for a long time.

Ubuntu16 is not to my knowledge used for any CDS system anywhere.  I'm not sure how you expect to have better support for that.  There are no pre-compiled packages of any kind available for Ubuntu16.  Good luck, you big smelly doofuses. Nyah, nyah, nyah.

Since the "stablizer box" doesn't really need to stabilize, it just needs to amplify, I decided to replace it with an off the shelf amplifier we already had, ZHL-2. I worked on getting it set up today, but didn't connect anything so that people have a chance to give some feedback. 

• The gain we expect is 18 dB, and the maximum output with 1dB of compression is 29 dBm. To avoid compression, I'm aiming for ~26 dBm output, so ~8 dBm input. We measured the output of the source to be 12.8 dBm before, so I attached a 5dB attenuator to the input side of the amplifier. 
• Across the 24V power input and the ground pin, I soldered a 100 uF, 50V electrolytic capacitor and a .27 uF, 50V metal film capacitor. Note that unlike the other similar amplifiers we have, the ground and +24 pins are separated (see image on datasheet). I wasn't sure if that changed what to do so I just found comparable caps to the ones that were there on another model. 
• I twisted and soldered wires to the +24 and ground, making sure they were long enough to reach the clips where the power from the Sorensens gets split up. I placed the amplifer in the rack on top of the RF distribution box and ziptied the power cable in place. 
• I connected a splitter to the output of the amplifier. Should I use a 10dB coupler instead, to maximize the power to the EOM?

So, I think the remaining thing to do is to connect the splitter to ASC out and to the line to the EOM, the +24V supply to the amplifier, and the 29.5 MHz input to the attenuator. I wanted to wait on this to get confiration that the setup is OK. Eventually we can put all of this in a box. 

Also, I noticed that in the clear cabinet with the Sorensens next to this rack, the +24 V unit is not supplying any voltage and has a red light that says "OVP." 

The bottom 5 cable connections from Sat-Amp to Whittering Filter at 1X5 were clamped today.

Had to reboot c1psl, c1susaux, c1auxex, c1auxey and c1iscaux today. PMC has been relocked. ITMX didn't get stuck. According to this thread, there have been two instances in the last 10 days in which c1psl and c1susaux have failed. Since we seem to be doing this often lately, I've made a little script that uses the netcat utility to check which slow machines respond to telnet, it is located at /opt/rtcds/caltech/c1/scripts/cds/testSlowMachines.bash.

The script can be executed by ./testSlowMachines.bash.

I've edited Rana's Simulink model to reflect the current IMC servo topology (to the best of my understanding). I've tried to use Transfer Function blocks wherever possible so that we can just put in the appropriate zpk model in the script that will linearize the whole loop. I've also omitted the FSS SLOW loop for now.

I've been looking through some old elogs and it looks like there have been several modifications to both the MC servo board (D040180) and the TT FSS Box (D040105). I think it is easiest just to measure these TFs since the IMC is still down, so I will set about doing that today. There is also a Pomona Box between the broadband EOM and the output of the TT FSS box, which is meant to sum in the modulation for PMC locking, about which I have not yet found anything on the elog.

So the next steps are:

1. Measure/estimate all the unknown TFs and gains in this schematic
2. Linearize the model, get the OLG, see if the model matches previously measured OLGs (with the MCL part disabled)
3. Once the model is verified to be correct, look at couplings of various noise sources in the MCL part of the loop, and come up with a suitable controller.

If anyone sees something wrong with this topology, please let me know so that I can make the required changes.

It is more accurate to model the physical frequency noises at various places.

cf. See also 40m ALS paper or Shigeo Nagano PDH thesis on https://wiki-40m.ligo.caltech.edu/40m_Library

- The output 4 should be "Laser frequency"

- Seismic path should be excluded from the summing node

- The output after the PMC: "Laser frequency after the PMC"

- "Laser frequency after the PMC" is compared (diffed) with the output 1 "mirror motion in Hz"

- The comparator output goes to the cav pole, the PD, and the PDH gain: This is the output named "PDH Error"

- Tap a new path from "Laser frequency after the PMC" and multiply with the cav pole (C_IMC)
- Tap a new path from "Mirror motion" and multiply with the cavity high pass  (s C_IMC/omega)
- Add these two: This is the output named "Frequency noise transmitted by IMC"

A few minutes back, I glanced up at the control room StripTool and noticed that the MCREFL PD DC level had gone up from ~0 to ~0.7, even though the PSL shutter was closed. This seemed bizzare to me. Strangely, simply cycling the shutter returned the value to the expected value of 0. I wonder if this is just a CDS problem to do with c1iool0 or c1psl? (both seem to be responding to telnet though...)

Since things look to be back to normal, I am going to start with my characterization of the various TFs in the IMC FSS loop...

I tested the amplifier with the Agilent network analyzer and measured 19.5 dB of gain between 29 and 30 mHz. The phase only changed by 1 degree over this same 1 MHz span. Since everything seems to be in order I'll hook it up this afternoon, unless there are any objections. 

                                                                                                                                   received this note: at 4:11pm Tuesday, Feb 7, 2017

**PLEASE POST**

Building:         Campus

Date:             Wednesday, February 8, 2017

Time:             7:30 AM – 8:30 AM  

Contact:          Rick Rodriguez x-2576

Pasadena Water and Power (PWP) will be performing a switching operation of the

Caltech Electrical Distribution System that is expected to be transparent to Caltech,

but could result in a minor power anomaly that might affect very sensitive equipment.

IMPACT: Negligible impact......?

There may be temporary  power interruption tomorrow!

PS:we did not see any effect   

I set everything up and connected it as shown on the block diagram attached to the previous entry, with the exception of the DC power. This is becuase there is no place open to connect to on the DIN rail where the DC power is distributed, so the +24V power will have to be shut off to the other equipment in 1X1 before we can connect the amplifier. (The amplifier is in 1X2, but the DC power distribution was more accessible in 1X1.) I also added 3 new +24 V clips with fuses despite needing only one, so next time we need to connect something new it's not such a hassle. 

The RF distribution box where the 29.5 MHz signal originates should not be turned on until the amplifer has DC power. Since we may have a power interruption tomorrow, the plan is to wait until things are shut down in preparation, and then shut off anyhting else necessary before connecting the new clips on the rail to the existing ones. 

After fighting with Altium for what seems like an eternity I have finished putting my vision of the vme crate backplane adapter board into an electronic format. It is dimensioned to fill the back space of the crate exactly. The connectors are panel mount and the PCB attaches to the connectors with screws, such that the whole thing will be mechanically much more stable than the current configuration. A mounting bracket will attach to horizontal struts that need to be installed in the crates, mechanical drawings to follow.

The ITMX oplev beam is clipping. It will be corected with locked arm

Quick summary elog, details to follow. I did the following:

• Updated the Simulink model based on Koji's feedback. 
• Today morning, I measured the (electronic) open-loop TFs of
  • MC Servo Board
  • FSS Fast path (PZT)
  • FSS PC Drive path
• The summing amplifiers in the latter two paths are assumed to be broadband for the purposes of this model.

The measurements I have look reasonable. But I had a hard time trying to look at the schematic and determine what is the appropriate number and locations of poles/zeros with which to fit the measured transfer function. Koji and I spent some time trying to go through the MC Servo board schematic, but looks like the version uploaded on the 40m DCC tree doesn't have changes made to it reflected (we compared to pictures on the 40m google photos page and saw a number of component values were different). Since the deviation between fit and measurement only occurs above 1MHz (while using poles/zeros inferred from the schematic), we decided against pulling out the servo board and investigating further - but this should be done at the next opportunity. I've marked the changes we caught on a schematic and will upload it to the 40m DCC page, and we can update this when we get the chance.

So it remains to fit the other two measured TFs, and add them to the Simulink model. Then the only unknown will be the PDH discriminant, which we anyway want to characterize given that we will soon have much more modulation.  

Data + plots + fits + updated schematics to follow...

http://www.amscope.com/3-5x-180x-boom-stand-trinocular-zoom-stereo-microscope-with-144-led-ring-light-and-10mp-camera.html will be ordered today.

The actual unit we are getting has lockable zoom for better repeatability after calibration: SM-3NTPZZ-144

Quote: CWQ6-020817

I'd like to fix a few things at 1X1 when we plug in the new amplifier for the 29.5MHz modulation signal. 

1. Split off separate +24 and ground wires to the green BBPD RF amplifiers and the AOM driver (they are sharing a single fuse at the moment)
2. Tap a new +24 GND -24V set for the FSS Fast summing box - this is currently running with a bench power supply underneath the PSL table set to +/-18V, but I checked the 7815/7915 datasheets and they accept up to 35V input for a 15V output, so it should be fine to use 24V
3. Hook up the ZHL-2A for the IMC modulation.

Steve has ordered rolls of pre-twisted wire to run from 1X1 to the PSL table, so that part can be handled later.

But at 1X1, we need to tap new paths from +/- 24V to the DIN connectors. I think it's probably fine to turn off the two Sorensens, do the wiring, and then turn them back on, but is there any procedure for how this should be done? 

Here are the details as promised.

Attachment #1: Updated simulink model. Since I haven't actually run this model, all the TF blocks are annotated "???", but I will post an updated version once I have run the model (and fix some of the questionable aesthetic choices)

Attachment #2: Measured and fitted transfer functions from the "IN1" input (where the demodulated MC REFL goes) to the "SERVO" output of the MC servo board (to FSS box). As mentioned in my previous elog, I had to put in a pole (fitted to be at ~2MHz, called pole 9 in the plot) in order to get good agreement between fit an measurement up to 10MHz. I didn't bother fitting all the high frequency features. Both gain sliders on the MEDM screen ("IN1 Gain" and "VCO gain") were set to 0dB for this measurement, while the super boosts were all OFF.

Attachment #3: Measured and fitted transfer function from "TEST 1 IN" to "FAST OUT" of the FSS box. Both gains on the FSS MEDM screen ("Common gain adjust" and "fast gain adjust") were set to 0dB for this measurement. I didn't need any ad-hoc poles and zeros for this fit (i.e. I can map all the fitted poles and zeros to the schematic), but the fit starts to deviate from the measurement just below 1 MHz.. perhaps I need to add a zero above 1MHz, but I can't see why from the schematic...

Attachment #4: Measured TF from "TEST 1 IN" to "PC OUT" on the FSS box. MEDM gains were once again 0dB. I can't get a good fit to this, mainly because I can't decipher the poles and zeros for this path from the schematic (there are actually deviations from the schematic posted on the 40m DCC page in terms of component values, I will try and correct whatever I notice) . I'll work on this...

Attachment #5: Data files + .fil files used to fit the data with LISO

Most of the model has come together, I am not too far from matching the modelled OLG to the measured OLG. So I will now start thinking about designing the controller for the MCL part (there are a couple of TFs that have to be measured for this path).

Lydia finished up installing the new RF amplifier, and will elog the details of the installation.

I wanted to try and measure the IMC OLG to compare against my Simulink model. So I went about performing a few checks. Summary of my findings:

1. The amplifier seems to be working fine. I checked powers at the input, output to EOM and output to distribution box (that serves the various LOs) first with a 30dB attenuator at the input, and subsequently with the design choice of 5dB attenuator at the input. Everything seemed in order.
2. I installed a 30 dB attenuator at the MC REFL PD input to the demod board since my (rough) calculations suggested that our modifications would have resulted in the RF beat power between carrier and sideband increasing in power by ~27dB.
3. I then opened the PSL shutter and tried locking the IMC - with manual tweaking of the various gains, I was able to lock.
4. But getting to this point took me a while so I couldn't get an OLG measurement in.

TBC tomorrow, I'm leaving the PSL shutter closed and the RF source off for tonight...

To install the replacement amplifier, I did the following:

• Mounted the amplifier in a 2U chassis, with a metal plate between the amplifier and the bottom of the box. The plate is separated from the box and the amplifier with 2 sets of Nylon screws. I did it this way to make use of the holes that were already in the chassis bottom and just drill holes into a plate instead. 
• Cannibalized mounting brackets and back panel from old ALS Beatbox. The back panel has an on/off switch and a 3W3 feedthrough for power. 
• Made a power cable to reach from the 1X1 fuse blocks to the back panel of my box. Goes up through the top of the rack and then back down. 
• Installed the chassis in the rack. The lid is currently off and there is no front panel yet. 
• Changed the +5dB attenuator to +30 to be able to check things first before supplying a way stronger signal. 
• Installed 4 new +24 V fuse blocks on the adjacent rack (1X1). 
  • Put the new fuses on the DIN rail and wired them together. Connected the new power cable to one of them. 
  • Blocked PMC transmission and made sure all RF sources in 1X1 and 1X2 were turned off
  • Turned off the + 24 V and -24 V Sorensens, trying to keep them fairly balanced as I turned them to 0. 
  • At this point Rana suggested I turn off the other DC power supplies in the rack, which I did.
  • Connected the new fuse blocks to the existing +24 V ones. Note that they are not contiguous but they follow the color code and will be labeled. 
  • I'm only using one of the new +24 outputs, but I made more for future use to minimize the number of times we have to turn the power off. 
• Connected the output of the amplifier to the EOM, and the coupled signal to the distribution box (which splits it and sends it to the demod boards). 
• Turned on the power switch and checked that the amplifier was in fact getting 24 V. 
• Connected the input from the 29.5 MHz source and measured the power coming from the amplifier. I measured -12 dBm instead of the expected ~0 dBm, but Gautam was able to see the expected power later, so maybe something just wasn't connected right.
• Double checked the power coming into the amplifier, which was consistent with earlier measurements at about 12.8 dBm. 

Still to be done:

• Label/relabel several things (fuse blocks, back panel, etc) 
• Current label on +24 Sorensen needs to be updated
• Order front panel and install
• Install power indicator lights on front and back 
• Readjust gains (analog and digital) to use full signal output and measure (hopefully) improved WFS performance
• Insert bi-directional coupler and measure modulation depth and reflections from EOM

c1iool0 was down again. Rather than key the crate, this time I just pushed the reset button on the front and it came back.

As move towards the wonderfulness of AcroMag, we also have to buy a computer  to handle all of these IOCs. Let's install the new c1iool0 over by the SUS computer.

To remind myself about how to put filter caps on the mini-circuits RF Amps, I looked at Koji's recent elog. Its mostly about op-amps, but the idea holds for us.

We want a big (~100 uF) electrolytic with a 50V rating for the +24V RF Amp. And then a 50V ceramic capacitor of ~0.1 uF close to the pins. Remember that the power feed through on the Mini-circuits case is itsself a capacitive feedthrough (although I guess its a ~100 pF).

Later, we should install in this box an active EMI filter (e.g. Vicor)

Rana and I spent some time looking at the IMC demod board earlier today. I will post the details shortly, but there was a label on the front panel which said that the nominal LO level to the input should be -8dBm. The new 29.5MHz routing scheme meant that the LO board was actually being driven at 0dBm (that too when the input to the RF distribution box was attenuated by 5dB).

An elog search revealed this thread, where Koji made some changes to the demod board input attenuators. Rana commented that it isn't a good idea to have the LO input be below 0dBm, so after consulting with Koji, we decided that we will

• Remove the 5dB attenuator to the input of the distribution box such that the LO is driven at ~5dBm
• Remove the input 10dB attenuator, first ERA-5SM amplifier, and the mini circuits power splitter from the demod board (schematic to follow).

After implementing these changes, and testing the board with a Marconi on the workbench, I found that the measured power levels (measured with an active FET probe) behave as expected, up till the ERA-5SM immediately prior to the LO (U4 and U6 on the schematic). However, the power after this amplifier (i.e. the input to the on-circuit LO, Minicircuits JMS-1H, which we want to be +17dBm), is only +16dBm. The input to these ERA-5SMs, which are only ~2years old, is -2dBm, so with the typical gain of +20dB, I should have 18dBm at their output. Moreover, increasing the input power to the board from the Marconi doesn't linearly increase the output from the ERA-5SM. Just in case, I replaced one of the ERA-5SMs, but observed the same behaviour, even though the amplifier shouldn't be near saturation (the power upstream of the ERA-5SM does scale linearly).

This needs to be investigated further, so I am leaving the demod board pulled out for now...

The input impedance of the mixer is not constant. As the diode switches, it changes dynamically. Because of this, the waveform of the LO at the mixer input (i.e. the amplifier output) is not sinusoidal. Some of the power goes away to harmonic frequencies. Also, your active probe is calibrated to measure the power across the exact 50Ohm load, which is not in this case. The real confirmation can be done by swapping the mixer with a 50Ohm resistor. But it is too much. Just confirm the power BEFORE the amp is fine. +/-1dB does not change the mixer function much.

Instead, we should measure
- Orthogonality
- Gain imbalance
of the I/Q output. This can be checked by supplying an RF signal that is 100~1kHz away from the LO frequency and observe I&Q outputs.

29.5 MHz RF Modulation Source

• The +13dBm from the Wenzel oscillator gets amplified to +27dBm by a ZHL-2-S. There is a 5dB attenuator on the input to the amplifier to avoid compression/saturation.
• The amplified output goes to the EOM (+26dBm measured at the rack, no measurement done at the input to the triple-resonant circuit box yet), while a 10dB coupled part goes to the RF distribution box which splits the input into 16 equal parts. The outputs were measured to spit out +5dBm.
• 2 of these go to the WFS demod boards - it was verified that this level of drive is okay for the comparator chips on the demod board.
• A third output goes to the IMC Demod board. The demod board was modified so that the nominal LO input level is now +5dBm (details below).
• The remaining outputs are all terminated with 50ohms.

IMC Demodulation Board

• The input attenuator, amplifier and power splitter were removed.
• Schematic with changes marked and power levels measured, along with a high-res photograph (taken with our fancy new Macro lens + LED light ring) has been uploaded to a page I made to track changes for this part on the DCC (linked to 40m document tree).
• After making the changes, it was verified that the power levels in the signal chain were appropriate up till the input to the ERA-5SM amplifier directly before the LO. These levels were deemed appropriate, and also scaled in a predictable manner with the input power. As Koji mentions in the previous elog, the dynamically changing input impedance of the mixer makes it difficult to measure the LO level at this point, but I am satisfied that it is within ~1dBm of the nominal +17dBm the mixer wants.
• The board was further checked for gain imbalance and orthogonality of the I and Q outputs. The graphic below show that there is negligible gain imbalance, but the relative phase between the I and Q channels is ~78 degrees (they should be 90 degrees). Of course this doesn't matter for the IMC locking as we only use the I phase signal, but presumably, we want to understand this effect and compensate for it. 
  
  
• The label on the front panel has been updated to reflect the fact that the nominal LO input is now +5dBm
• The demodulation phase had changed since the RF signal change was modified - Rana and I investigated this effect on Monday morning, and found that a new ~1.5m long cable was needed to route the signal from the RF distribution box to the LO input of the demod board, which I made. Subsequent modifications on the demod board meant that an extra ~10cm length was needed, so I just tacked on a short length of cable. All of the demodulated signal is now in the I output of the demod board (whereas we had been using the Q output).
• The graphics below confirms that claim above. Note the cool feature on the digital scopes that the display persistence can be set to "infinity"!
      

I wanted to do a quick check to see if the observed signal levels were in agreement with tests done on the workbench with the Marconi. The mixers used, JMS-1H, have an advertised conversion loss of ~7dB (may be a little higher if we are not driving the LO at +17dBm). The Lissajous ellipse above is consistent with these values. I didn't measure powers with the MC REFL PD plugged into the demod board, but the time series plot above suggest that I should have ~0dBm power in the MC REFL PD signal at 29.5MHz for the strongest flashes (~0.3Vpp IF signal for the strong flashes). 

MC Servo Board

• As mentioned above, we now use the I phase signal for lMC PDH locking.
• This has resulted in an overall sign change of the servo. I have updated the MEDM screen to reflect that "MINUS" is the correct polarity now..
• To set the various gains, I measured the OLTF for various configurations using the usual IN1/IN2 prescription on the MC Servo Board (using the Agilent analyzer). 
• I started at 0dBm "In1 Gain", and the nominal (old) values for "VCO gain", "FSS Common Gain" and "FSS FAST gain"  and found that though I could lock the MC, I couldn't reliably turn on the boosts.
• After some tweaking, I settled on +10dB "In1 Gain". Here, locking was much more reliable, and I was able to smoothly turn on the Super Boosts. The attached OLTF measurement suggests a UGF of ~118kHz and phase margin of a little more than 30 degrees. There is room for optimization here, since we have had UGFs closer to 200kHz in the recent past. 
  
• I didn't get around to measuring the actual PZT/EOM crossover yesterday. But I did measure the OLTF for various values of the FSS gains. At the current value of +20dBm, the PC drive signal is hovering around 1.5V. This bit of optimization needs to be done more systematically. 
• I've edited mcup and mcdown to reflect the new gains. 
  

Some general remarks

• The whole point of this exercise was to increase the modulation depth for the 29.5MHz signal. 
• By my estimate, assuming 8mrad/V modulation index for the EOM and a gain of 0.6 at 29.5 MHz in the triple resonant box, we should have 100mrad of modulation after installing the amplifier (compared to 4mrad before the change). 
• The actual RF power at 29.5 MHz at the input/output of the triple resonant box has not yet been measured. 
• The WFS input error signal levels have to be re-measured (so I've turned off the inputs to the digital WFS filters for now)

I would think that we want to fix the I/Q orthog inside the demod board by trimming the splitter. Mixing the Q phase signal to the I would otherwise allow coupling of low frequency Q phase junk from HOMs into the MC lock point.

I was a little confused why the In1 Gain had to be as high as +10dB - before the changes to the RF chain, we were using +27dB, and we expect the changes made to have increased the modulation depth by a factor of ~25, so I would have expected the new In1 Gain to be more like 0dB.

While walking by the PSL table, I chanced upon the scope monitoring PMC transmission, and I noticed that the RIN was unusually high (see the scope screenshot below). We don't have the projector on the wall anymore, but it doesn't look like this has shown up in the SLOW monitor channel anyways. Disabling the MC autolocker / closing the PSL shutter had no effect. I walked over to the amplifier setup in 1X2, and noticed that the SMA cable connecting the output of the amplifier to the EOM drive was flaky. By touching the cable a little, I noticed that the trace on the scope appeared normal again. Turning off the 29.5MHz modulation source completely returned the trace to normal.

So I just made a new cable of similar length (with the double heat shrink prescription). The PMC transmission looks normal on the scope now. I also re-aligned the PMC for good measure. So presumably, we were not driving the EOM with the full +27dBm of available power. Now, the In1 Gain on the MC servo board is set to +2dB, and I changed the nominal FSS FAST gain to +18dB. The IMC OLTF now has a UGF of ~165kHz, though the phase margin is only ~27 degrees.. 

Gautam and I were able to get the Raspberry Pi up and running today, including being able to ssh into it from the control room.

Below are some details about the setup/procedure that might be helpful to anyone trying to establish Ethernet connection for a new RPi, or a new operating system/SD card.

Here is the physical setup:

The changes that need to be made for a new Raspbian OS in order to communicate with it over ssh are as follows, with links to tutorials on how to do them:

1. Edit dhcpcd.conf file: https://www.modmypi.com/blog/how-to-give-your-raspberry-pi-a-static-ip-address-update

2. Edit interfaces file: https://www.mathworks.com/help/supportpkg/raspberrypi/ug/getting-the-raspberry_pi-ip-address.html

3. Enable ssh server: http://www.instructables.com/id/Use-ssh-to-talk-with-your-Raspberry-Pi/

The specific addresses for the RPi we set up today are:

IP Address: 192.168.113.107

Gateway/Routers/Domain Name Servers: 192.168.113.2

Netmask: 255.255.255.0

GV: I looked through /etc/var/bind/martian.hosts on chiara and decided to recycle the IP address for Domenica.martian as no RPis are plugged in right now... I'm also removing some of the attachments that seem to have been uploaded multiple times.

• Problems that have occurred since my last post: All of the sudden, I was getting very strange data that was very quiet and did not match the previous input range of my last locations (see attachment). After resoldering the custom bnc connection cables with Lydia, which were in disrepair, and checking almost everything we could think of, we found that the gain dial on the preamp was turned all the down. Immediately after it was fixed, the data returned to expected values (based on neighboring locations and data taken at the last location before the problem occurred). 
• Updates: Since my last post, I have created a normalized blrms color map in addition to the one I already have. Additionally, I have started working on plotting the color maps next to a labeled, to-scale drawing of the lab, but have yet to complete it. 
• Attachment 1: comparison of the psds
• Attachment 2: blrms color map
• Attachment 3: normalized color map

I made a tentative front panel design for the newly installed amplifier box. I used this chassis diagram to place the holes for attaching it. I just made the dimensions match the front of the chassis rather than extending out to the sides since the front panel doesn't need to screw into the rack; the chassis is mounted already with separate brackets. For the connector holes I used a caliper to measure the feedthroughs I'm planning to use and added ~.2 mm to every dimension for clearance, because the front panel designer didn't have their dimensions built in. Please let me know if I should do something else. 

The input and coupled output will be SMA connectors since they are only going to the units directly above and below this one. The main output to the EOM is the larger connector with better shielded cables. I also included a hole for a power indicator LED. 

EDIT: I added countersinks for 4-40 screws on all the screw clearance holes. 

Johannes, if you're going to be putting a front panel order in soon, please include this one. 

Also, Steve, I found a caliper in the drawer with a dead battery and the screws to access it were in bad shape- can this be fixed? 

PZT Buzzer Box (Thorlabs HV Supply + Manual + 2*PZT Buzzers) ---> Cryo Lab (Brittany + Aaron)

I finished designing the PCBs for the VME crate back sides (see attached). The project files live on the DCC now at https://dcc.ligo.org/LIGO-D1700058. I ordered a prototype quantity (9) of the PCB printed and bought the corresponding connectors, all will arrive within the next two weeks. See also attached the front panels for the Acromag DAQ chassis and Lydia's RF amplifier unit (the lone +24V slot confuses me: I don't see a ground connector?). On the Acromag panel, six (3x2) of the DB37 connectors are reserved for VME hardware, two are reserve, and I filled the remaining space with general purpose BNC connectors for whatever comes up.

The amplifier unit should use the three pin dsub connectors (3w3?) that we use on many of the other units for DC power, and preferably go through the back panel. You can leave out the negative pin, since you just need +24 and ground.

There has been a change in the default format for the output of the condor_q command at CIT clusters. This could be problematic for the summary page status monitor, so I have disabled the default behavior in favor of the old one. Specifically, I ran the following commands from the 40m shared account: mkdir -p ~/.condor echo "CONDOR_Q_DASH_BATCH_IS_DEFAULT=False" >> ~/.condor/user_config This should have no effect on the pages themselves.

This is already how it's hooked up. The hole on the from that says +24 V is for an indicator light.

Following the discussion at the meeting today, I wanted to finish up the WFS tuning and then hand over the IFO to Johannes for his loss stuff. So I did the following:

1. First I set the dark offsets on the WFS (with PSL shutter closed). Then I hand aligned the MC to maximize transmission, centered the beam on the WFS, and set the RF offsets with the MC unlocked.
2. Given that the demod phase for the IMC PDH demodulation board changed by |45 degrees|, I tried changing the digital demod phases in each of the WFS quadrant signals by +/- 45 degrees. Turns out +45 degrees put all the error signal into the I Phase, which is what we use for the WFS loops.
3. Then I attempted to check the WFS loops. I estimated that we have ~25 times the modulation depth now, so I reduced the WFS1/2 P/Y gains by this factor (but left the MC2 TRANS P/Y gains as is). The loop gain seemed overall too low, so I upped the gain till I saw instability in the loop (error signals ringing up). Then I set the loop gains to 1/3 of this value - it was 0.01 before, and I found the loop behaved well (no oscillations, MC TRANS stabilized) at a gain of 0.002.

At this point, I figured I would leave the WFS in this state and observe its behaviour overnight. But abruptly, the IMC behaviour changed dramatically. I saw first that the IMC had trouble re-acquiring lock. Moreover, the PC Drive seemed saturated at 10.0V, even when there was no error signal to the MC Servo board. Looking at the MEDM screen, I noticed that the "C1-IOO_MC_SUM_MON" channel had picked up a large (~3V) DC offset, even with In1 and In2 disabled. Moreover, this phenomenon seemed completely correlated with opening/closing the PSL shutter. Johannes and I did some debugging to make sure that this wasn't a sticky button/slider issue, by disconnecting all the cables from the front panel of the servo board - but the behaviour persisted, there seemed to be some integration of the above-mentioned channel as soon as I opened the PSL shutter.

Next, I blocked first the MC REFL PD, and then each of the WFS - turns out, if the light to WFS2 was blocked and the PSL shutter opened, there was no integrating behaviour. But still, locking the MC was impossible. So I suspected that something was wrong with the LO inputs to the WFS Demod Boards. Sure enough, when I disconnected and terminated those outputs of the RF distribution box, I was able to re-lock the MC fine.

I can't explain this bizzare behaviour - why should an internal monitor channel of the MC Servo board integrate anything when the only input to it is the backplane connector (all front panel inputs physically disconnected, In1 and In2 MEDM switches off)? Also, I am not sure how my work on the WFS could have affected any hardware - I did not mess around at the 1X1 rack in the evening, and the light has been incident on the WFS heads for the past few days. The change in modulation depth shouldn't have resulted in the RF power in this chain crossing any sort of damage threshold since the measured power before the changes was at the level of -70dBm, and so should be at most -40dBm now (at the WFS demod board input). The only thing different today was that the digital inputs of the WFS servos were turned on...

So for tonight I am leaving the two outputs of the RF distribution box that serve as the LO for the WFS demod boards terminated, and have also blocked the light to both WFS with beam blocks. The IMC seems to be holding lock steady, PC drive levels look normal...

Unrelated to this work, but I have committed to the svn the updated versions of the mcup and mcdown scripts, to reflect the new gains for the autolocker...

Summary:

Craig and I have been trying to put together a Simulink diagram of the proposed alternative calibration scheme. Each time I talk the idea over with someone, I convince myself it makes sense, but then I try and explain it to someone else and get more confused. Probably I am not even thinking about this in the right way. So I am putting what I have here for comments/suggestions.

What's the general idea?

Suppose the PSL is locked to the MC cavity, and the AUX laser is locked to the arm cavity (with sufficiently high BW). Then by driving a line in the arm cavity length, and beating the PSL and AUX lasers, we can determine how much we are modulating the arm cavity length in metres by reading out the beat frequency between the two lasers, provided the arm cavity length is precisely known.

So we need:

1. Both lasers to be stabilized to be able to sense the line we are driving
2. A high bandwidth PDH loop for locking the AUX laser to the arm cavity such that the AUX laser frequency is able to track the line we are driving
3. An accurate and precise way to read out the beat frequency (the proposal here is to use an FPGA based readout)
4. An accurate measurement of the arm length (I think we know the arm lengths to <0.1% so this shouldn't dominate any systematic error).

To be able to sense a 1kHz line being driven at 1e-16 m amplitude, I estimate we need a beat note stability of ~1mHz/rtHz at 1kHz.

Requirements and what we have currently:

• The PSL is locked to the mode-cleaner, and the arm cavity is locked to the PSL. The former PDH loop is high BW, and so we expect the stabilized PSL to have frequency noise of ~1mHz/rtHz at about 1kHz (to be measured and confirmed)
• The AUX laser is locked to the arm cavity with a medium-BW (~10kHz UGF) PDH servo. From past out-of-loop ALS beat measurements, I estimate the expected frequency noise of the AUX laser at 1kHz to be ~1Hz/rtHz with the current PDH setup
• Rana suggested we "borrow" the stability of the PSL by locking the AUX laser and PSL in a high bandwidth PLL - if we want this loop to have ~300kHz BW, then we need to use an EOM as an actuator. The attached Simulink diagram (schematic representation only, though I think I have measurements of many of those transfer functions/gains anyways) shows the topology I had in mind. Perhaps I did not understand this correctly, but if we have such a loop with high gain at 1kHz, and the error signal being the beat between PSL and AUX, won't it squish the modulation we are applying @1kHz?
• Is it feasible to instead add a parallel path to the end PDH loop with an EOM as an actuator (similar to what we do for the IMC locking)? Ideally, what we want is an end PDH loop which squishes the free-running NPRO noise to ~1mHz/rtHz at 1kHz instead of the 1Hz/rtHz we have currently. This loop would then also have negligible tracking error at 1kHz. Then, we could have a low bandwidth PLL offloading onto the temperature of the crystal to keep the beat between the two lasers hovering around the PSL frequency.

Hardware:

On the hardware side of things, we need:

• Broadband EOM
• FSS box to drive the EOM (Rana mentioned there is a spare available in the Cryo lab)

Koji and I briefly looked through the fiber inventory we have yesterday. We have some couplers (one mounted) and short (5m) patch fibers. But I think the fiber infrastructure we have in place currently is adequate - we have the AUX light brought to the PSL table, and there is a spare fiber running the other way if we want to bring the PSL IR to the end as well.

I need to also think about where we can stick the EOM in given physical constraints on the EX table and the beam diameter/aperture of EOM...

Question for Craig: What does the SNR of our lines have to be? IF we're only trying to calibrate the actuator in the audio band over long time scales, it seems we could get by with more frequency noise. Assuming we want a 1% calibration at 50-500 Hz, what is the requirement on the frequency noise PSD curve?

The MET#1 particle counter was moved from CES wall at ITMX to PSL enclousure south west corner at 11am.

The HEPA filter speed at the Variac was turned down to 20V from 40

This counter pumps air for 1 minute in every 20 minutes. Soft foam in bags used to minimize this shaking as it is clamped.

Koji, Gautam, Johannes

We quickly checked the situation of the projector in the control room.

- We found that the proejctor was indicating "lamp error".
==> Steve, could you remove the projector from the ceiling and check if it still does not work?
If it still does not work, send it back to the vender. It should be covered by the previous service.

- Zita seemed happy with the DVI output. We tried the dual display configration and  VGA and DVI are active right now.
The DVI output (from RADEON something video card) is somewhat strange. We probably need to look into the video display situation.