40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log, Page 299 of 341  Not logged in ELOG logo
ID Date Authorup Type Category Subject
  12503   Sun Sep 18 16:18:05 2016 ranaUpdateSUSAlignment status

susaux is responsible for turning on/off the inputs to the coil driver, but not the actual damping loops. So rebooting susaux only does the same as turning the watchdogs on/off so it shouldn't be a big issue.

Both before and after would be good. We want to see how much bias and how much voltage from the front ends were applied. l1susaux could have put in a huge bias, but NOT a huge force from the damping loops. But I've never seen it put in a huge bias and there's no way to prevent this anyway without disconnecting cables.

I think its much more likely that its a little stuck due to static charge on the rubber EQ stop tips and that we can shake it lose with the damping loops.

  12506   Mon Sep 19 13:57:21 2016 ranaUpdateGeneralnever post EPS files in the ELOG. Ever.

http://tex.stackexchange.com/questions/2092/which-figure-type-to-use-pdf-or-eps

  12508   Tue Sep 20 10:45:06 2016 ranaUpdateGeneralFurther recovery progress

Rana suspicious. We had arms locked before pumpdown with beams on Transmon PDs. If they're off now, must be beams are far off on the mirrors. Try A2L to estimate spot positions before walkin the beams too far.

  12522   Thu Sep 29 09:49:53 2016 ranaUpdateGeneralmucking about

With the WFS and OL, we never have figured out a good way to separate pit and yaw. Need to figure out a reference for up/down and then align everything to it: quad matrix + SUS output matrix

  12543   Mon Oct 10 17:27:29 2016 ranaUpdateDMFsummar pages dead again

Been non-functional for 3 weeks. Anyone else notice this? images missing since ~Sep 21.

  12562   Fri Oct 14 15:47:00 2016 ranaUpdateTreasurefilters + clip

I say just fix the clipping. Don't worry about the PRM OSEM filters. We can do that next time when we put in the ITM baffles. No need for them on this round.

  12572   Wed Oct 19 17:02:34 2016 ranaUpdateGeneral Viewports & coating of 2016

These old specs are not so bad. But we now want to get replacements for the TRX and TRY and PSL viewports that are R <0.1% at 532 and 1064 nm.

I don't know of any issues with keeping BK-7 as the substrate.

  12588   Fri Oct 28 19:13:57 2016 ranaUpdateGeneralPR gain

I don't think the loss of 25 ppm is outrageous. Its just surprisingly good. The SIS model predicted numbers more like 1 ppm / mirror taking into account just the phase map and not the coating defects.

However, we should take into account the lossed in the DRMI to be more accurate: AR coating reflectivities, scatter loss on those surfaces, as well as possible clipping around BS or some other optics.

https://chat.ligo.org/ligo/channels/40m

  12600   Sat Nov 5 15:45:44 2016 ranaUpdateCDSc1auxex channels/pins for Acromag

We don't need to record any of the AIOut channels, the OL channels (since we record them fast), or the _MEAN channels (I think they must be CALC records or just bogus).

  12615   Mon Nov 14 19:32:51 2016 ranaSummaryCDSReplacing DIMM on Optimus

I did apt-get update and then apt-get upgrade on optimus. All systems are nominal.

  12622   Thu Nov 17 12:14:21 2016 ranaUpdateCamerasBasler GigE-Camera on Optimus (+Mafalda dead)

Indeed. I suggest discussing with Joe B. I believe we should use a dedicated cam network to get the camera signals from the ends and corner all into one machine. Do not use the main CDS FE network for this since it might produce weird collissions. How about make a diagram, post it to elog, and send link to Joe?

It may be a good idea to leave the gigecam interfacing up to a dedicated machine.

  12637   Wed Nov 23 15:08:56 2016 ranaUpdateIMCMCL Feedback

In the Generic Pentek interface board, which is used to take in the analog 2-pin LEMO cable from the MC Servo board, there is some analog whitening before the signal is sent into the ADC.

There are jumpers in there to set whether it is 0, 1, or 2 stages of 150:15 (z:p) whitening.

  12647   Tue Nov 29 18:35:32 2016 ranaUpdateIOOIMC WFS Demod board measurement & analysis

more U4 gain, lesssss U5 gain

  12675   Thu Dec 8 19:01:21 2016 ranaUpdateIMCPartial IMC ringdowns

Mach Zucker on howto do Ringdowns:  https://dcc.ligo.org/LIGO-T900007

  12678   Thu Dec 15 03:46:19 2016 ranaUpdateIOOIMC WFS whitening filter investigation

https://dcc.ligo.org/LIGO-D1400414

As it turns out, its not so old as I thought. Jenne and I reworked these in 2014-2015. The QPD whitening is the same as the IMC WFS whitening so we can just repeat those fixes here for the IMC.

Quote:

Rana pointed out that this modification (removal of 900Ohm) leave the input impedance as low as 100Ohm.
As OP284 can drive up to 10mA, the input can span only +/-1V with some nonlinearity.

Rather than reinstalling the 900Ohms, Rana will investigate the old-days fix for the whitening filter that may involve the removal of AD602s.
Until the solution is supplied, the IMC WFS project is suspended.

 

  12688   Thu Dec 29 13:22:21 2016 ranaSummaryIOOIMC WFS tuning
  • For the rough calibration below 10 Hz, we can use the SUS OSEM cal: the SUSPIT and SUSYAW error signals are in units of micro-radians.
  • It seems from the noise plots that the demod board is now dominating over the whitening board noise.
  • If the RF signals at the demod input are low enough, we can consider either increasing the light power on the WFS or increasing the IMC mod. depth.
  • We should look at the out-of-lock light power on the WFS and re-examine what the 'safe' level is. We used to do this based on the dissipated electrical power (bias voltage x photocurrent).

At Hanford, there is this issue with laser jitter turning into an IMC error point noise injection. I wonder if we can try out taking the acoustic band WFS signal and adding it to the MC error point as a digital FF. We could then look at the single arm error signal to see if this makes any improvement. There might be too much digital delay in the WFS signals if the clock rate in the model is too low.

  12690   Thu Dec 29 21:35:30 2016 ranaSummaryIOOIMC WFS tuning

The WFS gains are supposedly maximized already. If we remotely try to increase the gain, the two MAX4106 chips in the RF path will oscillate with each other.

We should insert a bi-directional coupler (if we can find some LEMO to SMA converters) and find out how much actual RF is getting into the demod board.

  12691   Thu Dec 29 21:48:32 2016 ranaUpdateIOOMC AutoLocker hung because c1iool0 asleep again

MC unlocked, Autolocker waiting for c1iool0 EPICS channels to respond. c1iool0 was responding to ping, but not to telnet. Keyed the crate and its coming back now.

There's many mentions of c1iool0 in the recent past, so it seems like its demise must be imminent. Good thing we have an Acromag team on top of things!

Also, the beam on WFS2 is too high and the autolocker is tickling the Input switch on the servo board too much: this is redundant / conflicting with the MC2 tickler.

  12692   Fri Dec 30 10:27:46 2016 ranaUpdateDetCharsummary pages dead again

Dead again. No outputs for the past month. We really need a cron job to check this out rather than wait for someone to look at the web page.

  12693   Thu Jan 5 21:43:16 2017 ranaUpdateDetCharsummary pages dead again

Max tells us that soem conf files were bad and that he did something and now some pages are being made. But the PEM and MEDM pages are bank. Also the ASC tab looks bogus to me.

  12694   Fri Jan 6 17:00:26 2017 ranaFrogsTreasureVideo of Lab Tour

In this video: https://youtu.be/iphcyNWFD10, the comments focus on the orange crocs, my wrinkled shirt, and the first aid kit.

  12695   Sun Jan 8 12:47:06 2017 ranaUpdateGeneralOptical Layout in DCC

Manasa pointed me to the CAD drawings in the 40m SVN and I've now uploaded them to the 40m DCC Tree so that EricG and SteveV can convert them into SolidWorks.

  12700   Tue Jan 10 21:47:00 2017 ranaUpdateCDSpower glitch

Does "done" mean they are OK or they are somehow damaged? Do you mean the workstations or the front end machines?

The computers are all done.

megatron and optimus are not responding to ping commands or ssh -- please power them up if they are off; we need them to get data remotely

  12706   Thu Jan 12 13:43:02 2017 ranaHowTosafetyclosing a door

This is one of those unsolved door lock acquisition problems. Its been happening for years.

Please ask facilities to increase the strength of the door tensioner so that it closes with more force.

  12709   Thu Jan 12 23:22:34 2017 ranaUpdateSummary PagesDecember outage

Pages still not working: PEM and MEDM blank.

  • Committed existing MEDM grabbing scripts to SVN. Ran the cron job on megatron by hand. It grabs PNG files, but somehow its not getting into the summary pages.
  • Changed the MEDM grabbing scripts to use '/usr/bin/env'.
  • GW summary log files were numbering in the many thousands, so I moved everything over 320 days old into the OLD/ sub-directory using 'find . -type f -mtime +320 -exec mv {} OLD/ \;' (the semi-colon is needed)
  • Did apt-get upgrade on Megatron.
  • pinged Max
  • Stared at GWsumm docs to see if there's a clue about what (if anything) is wrong with the .ini file.
  12714   Fri Jan 13 21:32:49 2017 ranaHowToDAQGet 40m data using NDS2 and Python

The attached file is a python notebook that you can use to get data. Minimal syntax.

  12717   Sat Jan 14 00:53:05 2017 ranaHowToDAQGet 40m data using NDS2 and Python

Minute trend data seems not available using the NDS2 server. Its super slow using dataviewer from the control room.

Did some digging into the NDS2 config on megatron. It hasn't been updated in 2 years.

All of the stuff is run by the user 'nds2mgr'. The CronTab for this user was running all the channel name updates and server restarts at 3 AM each day; I've moved it to 5:05 AM. I don't know the password for this user, so I just did 'sudo su nds2mgr' to become him.

On megatron, in /home/nds2mgr/nds2-megatron/ there is a list of channels and configs. The file for the minute trend (C-M-ChanList.txt), hasn't been updated since Nov-2015. ???

  12718   Sat Jan 14 12:12:03 2017 ranaUpdateDAQminute trends missing

Did we turn off minute trend writing in one of the recent FrameBuilder debug sessions? Seems we only have second trends in 2016. Maybe this explains why its so slow to get minute trends? Dataviewer has to rebuild it from second trend.

controls@nodus|frames > l
total 64
drwx------   2 root     root     16384 Jun  8  2009 lost+found/
drwxr-xr-x   2 controls controls  4096 Jul 14  2015 tmp/
-rw-r--r--   1 controls controls     0 Jul 14  2015 test-file
drwxr-xr-x   5 controls controls  4096 Apr  7  2016 trend/
drwxr-xr-x   4 root     root      4096 Apr 11  2016 archive/
drwxr-xr-x 789 controls controls 36864 Jan 13 19:34 full/
controls@nodus|frames > cd trend
controls@nodus|trend > l
total 3340
drwxr-xr-x 258 controls controls 3342336 Jul  6  2015 minute_raw/
drwxr-xr-x 387 controls controls   36864 Nov  5  2015 minute/
drwxr-xr-x 969 controls controls   36864 Jan 13 19:49 second/

  12720   Sat Jan 14 22:39:30 2017 ranaSummarySUSITMY is drifting ?

https://nodus.ligo.caltech.edu:30889/detcharsummary/day/20170114/sus/susdrift/

ITMY is not like the others. Real or just OSEM madness?

  12721   Mon Jan 16 12:49:06 2017 ranaConfigurationComputersMegatron update

The "apt-get update" was failing on some machines because it couldn't find the 'Debian squeeze' repos, so I made some changes so that Megatron could be upgraded.

I think Jamie set this up for us a long time ago, but now the LSC has stopped supporting these versions of the software. We're running Ubuntu12 and 'squeeze' is meant to support Ubuntu10. Ubuntu12 (which is what LLO is running) corresponds to 'Debian-wheezy' and Ubuntu14 to 'Debian-Jessie' and Ubuntu16 to 'debian-stretch'.

We should consider upgrading a few of our workstations to Ubuntu 14 LTS to see how painful it is to run our scripts and DTT and DV. Better to upgrade a bit before we are forced to by circumstance.

I followed the instructions from software.ligo.org (https://wiki.ligo.org/DASWG/DebianWheezy) and put the recommended lines into the /etc/apt/sources.list.d/lsc-debian.list file.

but I still got 1 error (previously there were ~7 errors):

W: Failed to fetch http://software.ligo.org/lscsoft/debian/dists/wheezy/Release  Unable to find expected entry 'contrib/binary-i386/Packages' in Release file (Wrong sources.list entry or malformed file)

Restarting now to see if things work. If its OK, we ought to change our squeeze lines into wheezy for all workstations so that our LSC software can be upgraded.

  12722   Mon Jan 16 18:54:01 2017 ranaUpdateSUSBS: whitening re-engaged

Found that the BS whitening was off. Gautam says that "it has always been that way" and "there's nothing in the elog about this" and "I have no special relationship with Putin".

I looked at DV and DTT while turning the OSEM whitening back on. As expected, the sensor noise improved by 10x above 10 Hz. The time series shows no problems - its just less fuzzy now.

All OSEM spectra after the switch show on upper panel of plot. Lower panel shows comparison of BS UL before/after. To rotate the DTT PDF landscape output I typed this:

pdftk BS-white.pdf cat 1N output BSwhite.pdf

"if you see something, do something"

  12723   Mon Jan 16 21:03:47 2017 ranaSummaryIOOMCL / MCF / Calibration

Oot on the streets and in the chat rooms, people often ask, "What is up with the MC_F calibration?".

Not being sure of the wiring in the c1ioo model, I have formed this screencap of today's model and put it here. The MC_LENGTH and MC_FREQ are the filter banks which would calibrate these channels. In the filter banks there were various version of a 'dewhite' filter. They were all approximately z=150, p=15, g =1 @ DC, but with ~1% differences. I don't trust their provenance and so I've enforced symmetry and fixed their names to reflect what they are (150:15). I have also turned on one filter in MC_FREQ so that now the whitening of the Pentek Interface board is compensated.

Why is this TF 1/f? It should be -20 dB/decade if MC_F is in units of Hz* and MCL is a pendulum response. Perhaps its because the combination of the Koji summing box, the Thorlabs HV driver, and the Pomona box forms an additional 1/f ? IF so, this would explain the TF we see. Once we get confirmation from Koji, we can load the TF into the MC_FREQ filter bank and then MC_F will be in units of Hz (as will the summary pages).

(along the way I've also turned off the craaaazzzy servo input enable tickling that gets put in the MC AutoLocker every April Fool's leap year - resist the temptation)

Since we have a frequency counter system here and some oscillators, I wonder if we can just calibrate the MC_L and MC_F directly using a mixer lashed up to one of the counters. If so, and we can get the stabilized laser frequency noise down below 10 mHz/rHz, maybe this is a viable alternative method to the photon calibrators. Counting zero crossings is more honest than counting photons.

  12726   Tue Jan 17 20:39:30 2017 ranaUpdateComputer Scripts / Programsnodus web apache simlinks too soft

I tried to follow these instructions today to make the Simulink Webview accessible:

controls@nodus|public_html > ln -sfn /users/public_html/FE /export/home/

Quote:

The story is: we currently don't expose the whole /users/public_html folder. Instead, we are symlinking the folders from public_html to /export/home/ on nodus, which is where apache looks for things

So, I fixed the links on the Core Optics page by running:

controls@nodus|~ > ln -sfn /users/public_html/40m_phasemap /export/home/

But...I got a "403 Forbidden" message. What is the secret handshake to get this to work? And why have we added this extra step of security?

  12727   Tue Jan 17 20:47:23 2017 ranaUpdateCDSSimulink Webview updated

Seems like this stops working every ~2 years. Its been busted since early 2016 according to cron, so I fixed up the paths and restored some missing files and committed things to the SVN (with comments!) and now its working and grabbing the Web viewable versions of the front end models. Just need to restore its viewability and then the world can watch our models any time.

Quote:

Back in 2011, JoeB wrote some entries on how to automatically update the Simulink webview stuff.

Somehow, the cron broke down over the years. I reran the matlab file by hand today and it worked fine, so now you can see the up to date models using the internet.

https://nodus.ligo.caltech.edu:30889/FE/

 

  12735   Wed Jan 18 15:17:38 2017 ranaUpdateComputer Scripts / Programsnodus web apache simlinks too soft

I suppose before directory listings were turned off we should have fixed the script to make an index.html, but that's how it goes with "up"-grades. How about re-allow directory listing so that our old links for webview work again?


EQ: https://nodus.ligo.caltech.edu:30889/FE is live

  12741   Thu Jan 19 19:56:09 2017 ranaUpdateSUSMC1 SUS electronics investigation

Might be. Or it might be in the satellite box cabling. Hard to tell without a tester. I recommend you squish the cables on there and lock the MC and get back to the usual business. I'll check on sat. box with Ben.

Quote:

 

Is this sufficient evidence to conclude that the Satellite boxes are to blame? It's hard to explain why the glitches come and go in this fashion, and also the apparent difference in the length of time for which the glitches persist. Here, in almost 24 hours, there is one incidence of glitching, but in yesterday's trend plot, the glitching remains present over several hours... The amplitude of the glitches, and their coincidence in all 5 channels, seems consistent with what we have been seeing though...

 

  12764   Fri Jan 27 19:40:03 2017 ranaMetaphysicselogword wrapping & large images

"Why does the word wrapping not work in our browsers with ELOG?" I sometimes wonder. Some of the elogs are fine, but often the 40m one has the text run off the page.

I found that this is due to people uploading HUGE images. If you need to do this, just use the shrink feature in the elog compose window so that we only have to see the thumbnail at first. Otherwise your 12 MP images will make it hard to read everyone else's entries.

  12773   Tue Jan 31 13:46:34 2017 ranaUpdateIMCRF AM stabilization box pulled out
  1. What is the probe situation? Ought to use a high impedance FET probe to measure this or else the scope would load the circuit.
  2. The ERA amplifiers are known to slowly die over ~10 year times scales. Search our ELOG for ERA-5. We'll have to replace some; ask Steve to order if we don't have many in the Plateau Tournant.
  3. What kind of HELA are the HELA amplifiers? Please a link to the data sheet if you can find it. I wonder what the gain and NF are at 30 MHz. I think the HELA-10D should be a good variant.
  12774   Tue Jan 31 14:14:29 2017 ranaUpdateVACPressure watch script

I think this cron job is running on NODUS (our gateway) instead of our scripts machine:

*/1 * * * * /opt/rtcds/caltech/c1/scripts/Admin/n2Check.sh >> /opt/rtcds/caltech/c1/scripts/Admin/n2Check.log 2>&1

Quote:

Based on Jenne's chiara disk usage monitoring script, I made a script that checks the N2 pressure, which will send an email to myself, Jenne, Rana, Koji, and Steve, should the pressure fall below 60psi. I also updated the chiara disk checking script to work on the new Nodus setup. I tested the two, only emailing myself, and they appear to work as expected. 

The scripts are committed to the svn. Nodus' crontab now includes these two scripts, as well as the crontab backup script. (It occurs to me that the crontab backup script could be a little smarter, only backing it up if a change is made, but the archive is only a few MB, so it's probably not so important...)

moreover this script has a 90MB log file full of not finding its channel

I wish this script was in python instead of BASH and I wish it would run on megatron instead of nodus (why can't megatron send us email too?) and I wish that this log file would get wiped out once in awhile. Currently its been spitting out errors since at least a month ago:

Tue Jan 31 14:10:02 PST 2017 : N2 Pressure:

Channel connect timed out: 'C1:Vac-N2pres' not found.

(standard_in) 1: syntax error

  12777   Tue Jan 31 17:28:36 2017 ranaSummaryCDSMinute Trend Koan

Someone installed "Debian" on allegra. Why? Dataviewer doesn't work on there. Is there some advantage to making this thing have a different OS than the others? Any objections to going back to Ubuntu12?

  12785   Wed Feb 1 20:49:34 2017 ranaUpdateIMCRF AM stabilizer box Modification Plan

I suggest:

  1. Disable the path which goes to the two spare outputs. Replace the ERA-5 with a 50 Ohm resistor to terminate that path. Make sure the ERA bias voltage is not shorting into something.
  2. Remove the ERA amps from the ASC path and remove the switch. Make it fixed gain such that we get +27 dBm out of the front.
  3. Put the ASC output into the 1U multi-splitter box and attenuate those outputs so that they supply ~0 dBm to the 2 WFS and the LSC Demod board.

I think this then allows us to have the low noise OCXO signals everywhere with enough oomph.

 

  12789   Thu Feb 2 17:34:25 2017 ranaUpdatePEMEM172 mic is hooked up in the PSL

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.

http://i.dailymail.co.uk/i/pix/2017/01/23/22/3C6BB70900000578-0-image-a-1_1485211840229.jpg

  12791   Thu Feb 2 18:28:29 2017 ranaSummaryCDSMinute Trend Koan

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'

Quote:
Quote:

Someone installed "Debian" on allegra. Why? Dataviewer doesn't work on there. Is there some advantage to making this thing have a different OS than the others? Any objections to going back to Ubuntu12?

My elog negligence punchcard is getting pretty full... It's pretty much for the same reason as using Debian for optimus; much of the workstation software is getting packaged for Debian, which could offload our need for setting things up in a custom 40m way. Hacking the debian-focused software.ligo.org repos into Ubuntu has caused me headaches in the past. Allegra wasn't being used often, so I figured it was a good test bed for trying things out.

The dataviewer issue was dataviewer's inability to pull the `fb` out of `fb:8088` in the NDSSERVER env variable. I made a quick fix for it in the dataviewer launching script, but there is probably a better way to do it.

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.

  12792   Thu Feb 2 18:32:51 2017 ranaSummaryPSLPMC alignment

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.

  12795   Fri Feb 3 11:40:09 2017 ranaUpdateIMCMCL Feedback - framing the problem

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.

  12797   Sat Feb 4 12:00:59 2017 ranaSummaryCDS/cvs/cds/caltech/chans back on svn1.6

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.

  12818   Fri Feb 10 13:04:32 2017 ranaUpdateIOOMC AutoLocker hung because c1iool0 asleep again

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.

  12819   Fri Feb 10 13:24:28 2017 ranaUpdateIMC29.5 MHz stabilizer box replacement

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)

  12823   Mon Feb 13 11:55:14 2017 ranaUpdateIMCIMC length loop - summary of changes

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.frown

Quote:

Of course this doesn't matter for the IMC locking as we only use the I phase signal, but

 

  12835   Thu Feb 16 21:55:47 2017 ranaSummaryGeneralAlternative Calibration Scheme

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?

ELOG V3.1.3-