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ID Date Author Typeup Category Subject
  14890   Tue Sep 17 14:43:59 2019 gautamHowToCDSFinal bit bug of the BIO CDS module

Came across this while looking up the BIO situation at 1Y2. For reference, the fix Koji mentions can be seen in the attached screenshot (one example, the other BIO cards also have a similar fix). The 16th bit of the BIO is grounded, and some bit-shifting magic is used to implement the desired output.


Yutaro talked about the BIO bug in KAGRA elog. http://klog.icrr.u-tokyo.ac.jp/osl/?r=9536

I think I made the similar change for the 40m model somewhere (don't remember), but be aware of the presense of this bug.

  14900   Thu Sep 19 15:59:29 2019 aaronHowToCDSHow to save c1ioo

New DIMM cards have arrived. I stored them in the digital cabinet along y arm.

  15462   Thu Jul 9 16:02:33 2020 JonHowToCDSProcedure for setting up BHD front-ends

Here is the procedure for setting up the three new BHD front-ends (c1bhd, c1sus2, c1ioo - replacement). This plan is based on technical advice from Rolf Bork and Keith Thorne.

The overall topology for each machine is shown here. As all our existing front-ends use (obsolete) Dolphin PCIe Gen1 cards for IPC, we have elected to re-use Dolphin Gen1 cards removed from the sites. Different PCIe generations of Dolphin cards cannot be mixed, so the only alternative would be to upgrade every 40m machine. However the drivers for these Gen1 Dolphin cards were last updated in 2016. Consequently, they do not support the latest Linux kernel (4.x) which forces us to install a near-obsolete OS for compatibility (Debian 8).



  • OS: Debian 8.11 (Linux kernel 3.16)
  • IPC card driver: Dolphin DX 4.4.5 [works only with Linux kernel 2.6 to 3.x]
  • I/O card driver: None required, per the manual

Install Procedure

  1. Follow Keith Thorne's procedure for setting up Debian 8 front-ends
  2. Apply the real-time kernel patches developed for Debian 9, but modified for kernel 3.16 [these are UNTESTED against Debian 8; Keith thinks they may work, but they weren't discovered until after the Debian 9 upgrade]
  3. Install the PCIe expansion cards and Dolphin DX driver (driver installation procedure)
  15760   Tue Jan 12 08:21:47 2021 anchalHowToCDSAcromag wiring investigation

I used an Acromag XT1221 in CTN to play around with different wiring and see what works.  Following are my findings:

Referenced Single Ended Source (Attachment 1):

  • If the source signal is referenced single ended, i.e. the signal is only on the positive output and the negative side is tied to GND on the source side AND this GND is also shared by the power supply powering the Acromag, then no additional wiring is required.
  • The GND common to the power supply and the source is not required to be Earth GND but if done so, it should be at one point only.
  • RTN terminal on Acromag can be left floating or tied to IN- terminal.

Floating Single Ended Source (Attachment 2):

  • If the source signal is floating single-ended i.e. the signal is only on the positive output and the negative output is a floating GND on the source, the the IN- should be connected to RTN.
  • This is the case for handheld calibrators or battery powered devices.
  • Note that there is no need to connect GND of power supply to the floating GND on the source.

Differential Source (Attachment 3):

  • If the source is differential output i.e. the signal is on both the positive output and the negative output, then connect one of the RTN terminals on Acromag to Earth GND. It has to be Earth GND for this to work.
  • Note that you can no longer tie the IN- of different signals to RTN as they are all carrying different negative output from the source.
  • Earth GND at RTN gives acromag a stable voltage reference to measure against the signals coming in IN+ and IN-. And the most stable voltage reference is of course Earth GND.


  • We might have a mix of these three types of signals coming to a single Acromag box. In that case, we have to make sure we are not connecting the different IN- to each other (maybe through RTN) as the differential negative inputs carry signal, not a constant voltage value.
  • In this case, I think it would be fine to always use differential signal wiring diagram with the RTN  connected to Earth GND.
  • There's no difference in software configuration for the two types of inputs, differential or single-ended.
  • For cases in which we install the acromag box inside a rack mount chasis with an associated board (example: CTN/2248), it is ok and maybe the best to use the Attachment 1 wiring diagram.

Comments and suggestions are welcome.

Related elog posts:

40m/14841    40m/15134

Edit Tue Jan 26 12:44:19 2021 :

Note that the third wiring diagram mentioned actually does not work. It is an error in judgement. See 40m/15762 for seeing what happens during this.

  15761   Tue Jan 12 11:42:38 2021 gautamHowToCDSAcromag wiring investigation

Thanks for the systematic effort.

  1. Can you please post some time domain plots (ndscope perferably or StripTool) to clearly show the different failure modes?
  2. The majority of our AI channels are "Referenced Single Ended Source" in your terminology. At least on the c1psl Acromag crate, there are no channels that are truly differential drive (case #3 in your terminology). I think the point is that we saw noisy inputs when the IN- wasn't connected to RTN. e.g. the thorlabs photodiode has a BNC output with the shield connected to GND and the central conductor carrying a signal, and that channel was noisy when the RTN was unconnected. Is that consistent with your findings?
  3. What is the prescription when we have multiple power supplies (mixture of Sorensens in multiple racks, Thorlabs photodiodes and other devices powered by an AC/DC converter) involved?
  4. I'm still not entirely convinced of what the solution is, or that this is the whole picture. On 8 Jan, I disconnected (and then re-connected) the FSS RMTEMP sensor from the Acromag box, to check if the sensor output was noisy or if it was the Acromag. The problem surfaced on Dec 15, when I installed some new electronics in the rack (though none of them were connected to the Acromag directly, the only common point was the Sorensen DCPS. And between 8 Jan and today, the noise RMS has decreased back to the nominal level, without me doing anything to the grounding. How to reconcile this?
  15762   Wed Jan 13 16:09:29 2021 AnchalHowToCDSAcromag wiring investigation

I'm working on a better wiring diagram that takes into account multiple power supplies, how their GND is passed forward to the circuits or sensors using those power supplies and what possible wiring configurations on Acromag would give low noise. I think I have two configurations in mind which I will test and update here with data and better diagrams.

I took some striptool images earlier yesterday. So I'm dumping them here for further comments or inferences.

  15778   Tue Jan 26 12:59:51 2021 AnchalHowToCDSAcromag wiring investigation

Taking inspiration from SR785 on how it reads differential signal, I figured that acromag too always need a way to return current through RTN ports always. That must be the reason why everything goes haywire when RTN is not connected to IN-. Now for single ended signals, we can always short RTN to IN- and keep same GND but then we need to be careful in avoiding ground loops. I'm gonna post a wiring diagram in next post to show how if two signal sources connect to each other separately, a GND loop can be formed if we tie each IN- port to RTN on an acromag.
Coming to the issue of reading a differential signal, what SR785 does is that it connects 50 Ohm resistance between Earth GND and differential signal shields (which are supposed to signal GND). In a floating GND setting, SR785 connects a 1 MOhm resistor between input shield and Earth GND. This can be used to read a differential signal through a single BNC cable since the shiled can take arbitrary voltages thanks ti the 1 MOhm resistor.

We can do the same in acromag. Instead of shorting RTN to IN- ports, we can connect them through a large resistor which would let IN- float but will give a path for current to return through RTN ports. Attached here are few scenarios where I connected IN- to RTN throguh wire, 820 Ohms, 10kOhms and 1MOhms in two sub cases where RTN was left open or was shorted to Earth GND. In all cases, the signal was produced by a 9V battery outputing roughly 8.16V. It seems that 10kOhm resistor between RTN and IN- with RTN connected to Earth GND is the best scenario noise wise. I'll post more results and a wiring diagram soon.

  15779   Tue Jan 26 15:37:25 2021 AnchalHowToCDSAcromag wiring investigation

Here I present few wiring diagrams when using Acromag to avoid noisy behavior and ground loops.

Case 1: Only single-ended sources

  • Attachment 1 gives a functioning wiring diagram when all sources are single ended.
  • One should always short the RTN to IN- pin if the particular GND carried by that signal has not been shorted before to RTN for some other signal.
  • So care is required to mark different GNDs of different powersupply separately and follow where they inadvertently get shorted, for example when a photodiode output is connected to FSS Box.
  • Acromag should serve as the node of all GNDs concerned and all these grounds must not be connected to Earth GND at power supply ends or in any of the signal sources.
  • I think this is a bit complicated thing to do.

Case 2: Some single and some differential sources

  • Connect all single ended sources same as above keeping care of not building any ground loops.
  • The differential source can be connected to IN+ and IN- pins, but there should be a high resistance path between IN- and RTN. See Attachment 2.
  • Why this is the case, I'm not sure since I could not get access to internal wiring of Acromag (no response from them). But I have empirically found this.
  • This helps IN- to float with respect to RTN according to the negative signal value. I've found that 10kOhm resistance works good. See 40m/15778.
  • If RTN is shorted to nearby Earth GND (assuming none of the other power supply GNDs have been shorted to Earth GND) shows a reduction in noise for differential input. So this is recommended.
  • This wiring diagram carries all complexity of previous case along with the fact that RTN and anything connected to it is at Earth GND now.

Case 3: Signal agnostic wiring

  • Attachment 3 gives a wiring diagram which mimics the high resistance shorting of RTN to IN- in all ports regardless of the kind of signal it is used for reading.
  • In this case, instead of being the node of the star configuration for GND, acromag gets detached from any ground loops.
  • All differences in various GNDs would be kept by the power supplies driving small amounts of current through the 10 kOhm resistors.
  • This is a much simpler wiring diagram as it avoids shorting various signal sources or their GNDs with each other, avoiding some of the ground loops.

Edit Wed Jan 27 13:38:19 2021 :

This solution is not acceptable as well. Even if it is successfull in reading the value, connecting resistor between IN- and RTN will not break the ground loops and the issue of ground loops will persist. Further, IN- connection to RTN breaks the symmetry between IN-  and IN+, and hence reduces the common mode rejection which is the intended purpose of differential signal anyways. I'll work more on this to find a way to read differential signals without connecitng IN- and RTN. My first guess is that it would need the GND on the source end to be connected to EarthGND and RTN on acromag end to be connected to EarthGND as well.


  15785   Fri Jan 29 17:57:17 2021 AnchalHowToCDSAcromag wiring investigation

I found a white paper  from Acromag which discusses how to read differential signal using Acromag units. The document categorically says that differential signals are always supposed to be transmitted in three wires. I provides the two options of either using the RTN to connect to the signal ground (as done in Attachment 3) or locally place 10k-100k resistors between return and IN+ and IN- both (Attachment 2).

I have provided possible scenarios for these.

Using two wires to carry differential signal (Attachment 1):

  • I assume this is our preferential way to connect.
  • We can also assume all single-ended inputs as differential and do a signal condition agnostic wiring.
  • Attachment 3 show what were the results for different values of resistors when a 2Hz 0.5V amplitude signal from SR785 which as converted to differential signal using D1900068 was measured by acromag.
  • The connection to RTN is symmetrical for both inputs.

Using three wires to carry differential signal (Attachment 2):

  • This is recommended method by the document in which it asks to carry the GND from signal source and connect it to RTN.
  • If we use this, we'll have to be very cautious on what GND has been shorted through the acromag RTN terminals.
  • This would probably create a lot of opportunities for ground loops to form.

Using an acromag card without making any connection with RTN is basically not allowed as per this document.

  15857   Wed Mar 3 12:00:58 2021 Paco, AnchalHowToIMCMC_F ASD

[Paco, Anchal]

- Saved BURT backup in /users/anchal/BURTsnaps/
- Copied existing code for mode cleaner noise budget from /users/rana/mat/mc. Will work on this from home to convert it inot new pynb way.

Get baseline IMC measurements (passive):
- MC_F:
  - What is MC_F? Let's find out.
  - On MC_F Cal window titled 'C1IOO-MC_FREQ', we turned off ON/OFF and back on again.
  - Using diaggui, we measured ASD of MC_F channel in units of counts/rtHz.

[Rana, Paco]

- Using diaggui, measured ASD from a template (under /users/Templates) and overlay the 1/f noise of the NPRO (Attachment 1)

[Anchal, Paco]

- WFS Master
  - Went through the schematic and tried to understand what is happening.
  - Accidentally switched on MC WF relief (python 3). Bunch of things were displayed on a terminal for a while and then we Ctrl-C it.
  - The only thing we noticed that change is a slight increase in WFS1 Yaw, and a corresponding decrease in WFS1 Pitch, WFS2 Pitch, and WFS2 Yaw.
  - We need to find out what this script does.

Future work:

  • Create an automated script for taking MC_F_DQ spectrum and refer it against reference trace.
  • Use pynb to create a noise budget for mode cleaner.
  • Identify excess noise between 10-40 Hz.
  • Configure output matrix in WFS Master to reduce the noise. Automate this process as well.
  16085   Mon Apr 26 18:52:52 2021 Anchal, PacoHowToComputer Scripts / Programsawg free slot

Today we had some trouble launching an excitation on C1:IOO-MC_LSC_EXC from awggui. The error read:

awgSetChannel: failed getIndexAWG C1:SUS-MC2_LSC_EXC ret=-3

What solved this was the following :

  1. launch the dtt command line interface
  2. Anchal remembers a slot number 37008
  3. We issue >> awg free 37008
  4. Slot freed, launch a new instance of awggui
  16441   Sun Oct 31 14:21:31 2021 ranaHowToTreasureIFOCad

IFOcad model/video of the AEI 10m interferometer:


  16467   Tue Nov 16 11:37:26 2021 HangHowToSUSFitting suspension model--large systematic errors

One goal of our sysID study is to improve the aLIGO L2A feedforward. Our algorithm currently improves only the statistical uncertainty and assumes the systematic errors are negligible. However, I am currently baffled by how to fit a (nearly) realistic suspension model...

My test study uses the damped aLIGO QUAD suspension model. From the Matlab model I extract the L2 drive in [N] to L3 pitch in [rad] transfer function (given by a SS model with the A matrix having a shape of 103x103). I then tried to use VectFIT to fit the noiseless TF. After removing nearby z-p pairs (defined by less than 0.2 times the lowest pole frequency) and high-frequency zeros, I got a model with 6 complex pole pairs and 4 complex zero pairs (21 free parameters in total). I also tried to fit the TF (again, noiseless) with an MCMC algorithm assuming the underlying model has the same number of parameters as the VectFIT results. 

Please see the first attached plots for a comparison between the fitted models and the true one. In the second plot, we show the fractional residual

    | TF_true - TF_fit | / | TF_true |,

and the inverse of this number gives the saturating SNR at each frequency. I.e., when the statistical SNR is more than the saturating value, we are then limited by systematic errors in the fitting. And so far, disappointingly I can only get an SNR of 10ish for the main resonances...

I wonder if people know better ways to reduce this fitting systematic... Help is greatly appreciated!

  16486   Mon Nov 29 15:24:53 2021 HangHowToGeneralFisher matrix vs length of each FFT segment

We have been discussing how does the parameter estimation depends on the length per FFT segment. In other words, after we collected a series of data, would it be better for us to divide it into many segments so that we have many averages, or should we use long FFT segments so that we have more frequency bins?

My conclusions are that:

1). We need to make sure that the segment length is long enough with T_seg > min[ Q_i / f_i ], where f_i is the resonant frequency of the i'th resonant peak and the Q_i its quality factor. 

2). Once 1) is satisfied, the result depends weakly on the FFT length. There might be a weak hint preferring a longer segment length (i.e., want more freq bins than more averages) though. 


To reach the conclusion, I performed the following numerical experiment.

I considered a simple pendulum with resonant frequency f_1 = 0.993 Hz and Q_1 = 6.23. The value of f_1 is chosen such that it is not too special to fall into a single freq bin. Additionally, I set an overall gain of k=20. I generated T_tot = 512 s of data in the time domain and then did the standard frequency domain TF estimation. I.e., I computed the CSD between excitation and response (with noise) over the PSD of the excitation. The spectra of excitation and noise in the readout channel are shown in the first plot. 

In the second plot, I showed the 1-sigma errors from the Fisher matrix calculation of the three parameters in this problem, as well as the determinant of the error matrix \Sigma = inv(Fisher matrix). All quantities are plotted as functions of the duration per FFT segment T_seg. The red dotted line is [Q_1/f_1], i.e., the time required to resolve the resonant peak. As one would expect, if T_seg <~ (Q_1/f_1), we cannot resolve the dynamics of the system and therefore we get nonsense PE results. However, once T_seg > (Q_1/f_1), the PE results seem to be just fluctuating (as f_1 does not fall exactly into a single bin). Maybe there is a small hint that longer T_seg is better. Potentially, this might be due to that we lose less information due to windowing? To be investigated further... 

I also showed the Fisher estimation vs. MCMC results in the last two plots. Here each dot is an MCMC posterior. The red crosses are the true values, and the purple contours are the results of the Fisher calculations (3-sigma contours). The MCMC results showed similar trends as the Fisher predictions and the results for T_seg = (32, 64, 128) s all have similar amounts of scattering << the scattering of the T_seg=8 s results. Though somehow it showed a biased result. In the third plot, I manually corrected the mean so that we could just compare the scattering. The fourth plot showed the original posterior distribution. 


  16980   Fri Jul 8 14:03:33 2022 JCHowToVACVacuum Preparation for Power Shutdown

[Koji, JC]

Koji and I have prepared the vacuum system for the power outage on Saturday.

  1. Closed V1 to isolate the main volume.
  3. Closed V6, then close VM3 to isolate RGA
  4. Turn off TP1 (You must check the RPMs on the TP1 Turbo Controller Module)
  5. Close V5
  6. Turn off TP3 (There is no way to check the RPMs, so be patient)
  7. Close V4 (System State changes to 'All pneumatic valves are closed)
  8. Turn off TP2 (There is no way to check the RPMs, so be patient)
  9. Close Vacuum Valves (on TP2 and TP3) which connect to the AUX Pump.
  10. Turn of AUX Pump with the breaker switch wall plug.

From here, we shutdown electronics.

  1. Run /sbin/shutdown -h now on c1vac to shut the host down.
  2. Manually turn off power to electronic modules on the rack.
    • GP316a
    • GP316b
    • Vacuum Acromags
    • PTP3
    • PTP2
    • TP1
    • TP2 (Unplugged)
    • TP3 (Unplugged)


  16985   Mon Jul 11 15:26:12 2022 JCHowToVACStartup after Power Outage

[Koji, Jc]

Koji and I began starting that Vacuum system up.

  1. Reverse order step 2 of shutting down electronics. Anthing after, turn on manually.
  2. If C1vac does not come back, then restart by holding the reset button.
  3. Open VA6
  5. Open V7
  6. Check P3 and P2, if they are at high pressure, approx. 1 Torr range, then you must use the roughing pumps.
  7. Connect Rotary pump tube. (Manually)
  8. Turn on AUX Pump
  9. Manually open TP2 and TP3 valves.
  10. Turn on TP2 and TP3, when the pumps finish startup, turn off Standby to bring to nominal speed.
  11. Turn on RP1 and RP3
  12. Open V6
  13. Once P3 reaches <<1 Torr, close V6 to isolate the Roughing pumps.
  14. When TP2 and TP3 are at nominal speed, open V5 and V4.
  15. Now TP1 is well backed, turn on TP1.
  16. When TP1 is at nominal speed, Open V1.
  16987   Mon Jul 11 17:41:52 2022 KojiHowToVACStartup after Power Outage

- Once the FRG gauge readings are back (see next elog by Tega), I could open V1 to pump down the main vacuum manifold.
- TP2/TP3 were brought back to stand-by mode (slower spinning)
- V7 was closed to separate the annuli side and TP1

During the vacuum recovery, I saw TPs were automatically turned on as soon as the backing pumps were engaged. I could not figure out what caused this automation.

Also, I saw some gate valve states changed while I was not touching them. e.g. V7 was close / VM3 was open / etc
I really had no idea what/who was handling these.

As of ~18:00 local, the main volume pressure is ~2e-5 torr and ready to open the PSL shutter.

  17104   Thu Aug 25 15:24:06 2022 PacoHowToElectronicsRFSoC 2x2 board -- fandango

[Paco, Chris Stoughton, Leo -- remote]

This morning Chris came over to the 40m lab to help us get the RFSoC board going. After checking out our setup, we decided to do a very basic series of checks to see if we can at least get the ADCs to run coherently (independent of the DACs). For this I borrowed the Marconi 2023B from inside the lab and set its output to 1.137 GHz, 0 dBm. Then, I plugged it into the ADC1 and just ran the usual spectrum analyzer notebook on the rfsoc jupyter lab server. Attachment #1 - 2 shows the screen captured PSDs for ADCs 0 and 1 respectively with the 1137 MHz peaks alright.

The fast ADCs are indeed reading our input signals.

Before this simple test, we actually reached out to Leo over at Fermilab for some remote assistance on building up our minimally working firmware. For this, Chris started a new vivado project on his laptop, and realized the rfsoc 2x2 board files are not included in it by default. In order to add them, we had to go into Tools, Settings and add the 2020.1 Vivado Xilinx shop board repository path to the rfsoc2x2 v1.1 files. After a little bit of struggling, uninstalling, reinstalling them, and restarting Vivado, we managed to get into the actual overlay design. In there, with Leo's assistance, we dropped the Zynq MPSoC core (this includes the main interface drivers for the rfsoc 2x2 board). We then dropped an rf converter IP block, which we customized to use the right PLL settings. The settings, from the System Clocking tab were changed to have a 409.6 MHz Reference Clock (default was 122.88 MHz). This was not straightforward, as the default sampling rate of 2.00 GSPS was not integer-related so we had to also update that to 4.096 GSPS. Then, we saw that the max available Clock Out option was 256 MHz (we need to be >= 409.6 MHz), so Leo suggested we dropped a Clocking Wizard block to provide a 512 MHz clock input for the rfdc. The final settings are captured in Attachment # 3. The Clocking Wizard was added, and configured on its Output Clocks tab to provide a Requested Output Freq of 512 MHz. The finall settings of the Clocking wizard are captured in Attachment #4. Finally, we connected the blocks as shown in Attachment #5.

We will continue with this design tomorrow.

  17194   Mon Oct 17 17:42:35 2022 JCHowToOPLEV TablesIMC Reflected beam sketch

I sketched up a quick drawing with estimated length for the IMC reflected beam. This includes the distances and focal length. Distances are from optic to optic. 

  17277   Thu Nov 17 11:24:39 2022 JCHowToLSCLocking MICH

[Yuta, JC]

Here is the Yuta's Alignment Scheme from elog 17056  with these slight adjustments:

Current alignment scheme:
Current alignment scheme I figured out is the following.
 - Check Y green. If it is transmitted at good spot on GTRY camera, Yarm is OK. If not, tweak ITMY/ETMY. alignment.
 - Mis-align AS4, align TT1, TT2, LO1 to have BHDC_A_OUT of ~115 and BHDC_B_OUT of ~95.
 - Align PR3, PR2 to maximize TRY_OUT to ~1.0
 - Tweak ITMY/ETMY if the beam spot on them are not good.
 - Align BS, ITMX to have good MICH fringe and TRX_OUT to ~1.0.
 - Tweak ITMX/ETMX if the beam spot on them are not good.
 - Misalign ETMY, ETMX, ITMY to have LO-ITMX fringe in BHD DCPDs. From Sitemap --> BHD --> Homodyne Phase Ctrl --> LO_PHASE --> Turn ON LO Phase Servo (This will lock LO and ITMX fringe) --> align AS beam with SR2 and AS4 differentially, with ratio of AS4/SR2=3.6 for YAW, with ratio of AS4/SR2= 4.5 for PITCH to have BHDC_A_OUT ~ 50.
 - Restore ITMY alignment, and lock MICH.

  131   Wed Nov 28 16:18:15 2007 AlbertoMetaphysicsEnvironmentso clean you can eat on it
I tidied up the desks in the lab, brought the Spectrum Analyzers back to the Salumeria (you don't want to know about that), sorted a lot of stuff and boxed up what I didn't know (you can find it in a couple of carton boxes on the table).
The blackmail with the pie might not work next time.
Please, preserve the common sort.

  180   Fri Dec 7 14:14:48 2007 robMetaphysicsComputer Scripts / Programstdsread problems on Solaris

tdsread has developed a strange new illness, whereby it cannot read EPICS values from two subsystems at once (e.g., getting an LSC and SUS value simultaneously). I thought this might have something to with the fact that both losepics and iscepics are running on the same box,
but the same thing happens with IOO EPICS records, so that's not the culprit.

This is new behaviour, and it's only happening on the solaris machines. I suspect some ENV/cshrc juju has caused it, as the tdsread executable is the same one from April, and I don't think our EPICS infrastructure has changed otherwise. In the near term we can either try running the scripts on linux, or modify the IFO scripts to not do these types of calls.
  277   Sun Jan 27 13:13:21 2008 tobinMetaphysicsGeneraldeparture
It's been grand. Thanks for having me!


Sugar napoleons may be forwarded to T. F., c/o LLO, P.O. Box 940, Livingston, LA 70754-0940.
  374   Thu Mar 13 03:07:19 2008 LisaMetaphysicsEnvironmentCoolness at the 40m
My first (and hopefully not last) week at the 40m lab is ending Frown
I found this lab really cool, the people working here really cool as well, and this e-log....
this e-log is not just cool, it is FANTASTIC!!!

  438   Tue Apr 22 22:19:02 2008 robMetaphysicslorejiggling sliders

In the interests of tacit communication of scientific knowledge, I here reveal a nugget of knowledge which may or may not prove useful to new LIGOites: sometimes when front-end machines are rebooted, the hardware they control can wind up in a state which is not accurately represented by the EPICS values you may see. This can be easily rectified by momentarily changing the EPICS settings in question. For reference, this came up tonight in the context of the whitening gain sliders for the TransMon QPDs.
  652   Wed Jul 9 15:04:22 2008 steveMetaphysicsPhotosSURFs helping hands
Surf students are helping out with baffle cleaning.
  657   Thu Jul 10 23:27:57 2008 JohnMetaphysicsCamerasSecret handshakes
Rob and I have joined the ranks of the illuminati and exercised our power.

Osamu showed me the secret way to change the video labels for the quads and
so we fixed them. He made me swear not to divulge this art.

- Rana Adhikari
  658   Fri Jul 11 00:30:24 2008 robMetaphysicsComputersstrange SUS controllers

rob, johnnieM

We were hampered early tonight by the fact that someone sneakily turned off the HP RF Ampflier on the AS table.

After that, we were hampered further by mode cleaner strangeness. It would occasionally spontaneously unlock & blow its watchdogs. It never made it through the ontoMCL script (putting DC-CARM onto the MCL). After some investigation, we found that c1susvme1 and c1susvme2 were running stochastically late (SYNC_FE != 0), even though their computation times never got above 61. Also, the end SUS controllers were never late.


After rebooting the vertex SUS controllers and the c1lsc, things appear to be working again.
  716   Tue Jul 22 16:50:09 2008 steveMetaphysicsEnvironmentprofessorial clean up of work bench
Atm1: is showing the spiritual satisfaction after work bench clean up by the professor himself.

Atm2: some items are still waiting to be placed back to their location
  1025   Fri Oct 3 19:38:02 2008 robMetaphysicsEnvironmentThe Gatekeeper

Found this lady outside the door of the 40m lab a few nights ago.
  1026   Sat Oct 4 07:23:42 2008 KojiMetaphysicsEnvironmentThe Gatekeeper
Hi, this is Koji from Japan.

I am afraid that this is a poisonous spider, Latrodectus hasseltii.
In Japanese word "Seaka-goke-gumo" (red-backed widow spider)

I am not an expert of insects, but this type of spider is getting famous in Japan as they were accidentally imported from South-West asia and Austraria to Japan in recent years, and they settled in certain city areas.

It is said that its neurotoxic venom causes unpleasant results such as shock, pain, and inflammation, even it is not too strong to kill human.

Be careful.


Found this lady outside the door of the 40m lab a few nights ago.
  1076   Thu Oct 23 18:51:19 2008 AlbertoMetaphysicsComputerseLog
I checked it and the latest version of the elog software, the 2.7.5 (we have the 2.6.5) has, among new nice features, the very good ability to fit the entries into the screen width without showing kilometric lines like we see now. Should we upgrade it?
  2228   Tue Nov 10 17:49:20 2009 AlbertoMetaphysicsComputersTest Point Number Mapping

I found this interesting entry by Rana in the old (deprecated) elog : here

I wonder if Rolf has ever written the mentioned GUI that explained the rationale behind the test point number mapping.

I'm just trying to add the StochMon calibrated channels to the frames. Now I remember why I kept forgetting of doing it...

  2439   Mon Dec 21 08:16:54 2009 steveMetaphysicsPEMjackhammering next door

At ITMX, on the CES side, 5 Ft  from the wall the jackhammer is on. The susses are holding well.

  2489   Fri Jan 8 18:20:12 2010 steveMetaphysicsTreasureRob now can concentrate on his thesis

We are celebrating Rob's promotion to thesis poetry.  These pictures were taken on December 9, 2009

Rob has finished all his measurements in the lab and is officially well prepared to graduate.

rob1.JPGrob2.JPG rob3.JPG


  2667   Thu Mar 11 15:24:51 2010 steveMetaphysicsEnvironmentIFO was well protected


There is a planned power outage tomorrow, Saturday from 7am till midnight.

I vented all annulies and switched to ALL OFF configuration. The small region of the RGA is still under vacuum.

The vac-rack: gauges, c1vac1 and UPS turned off.

 It turns out that we perfecly timed the big one

In the process of finding the signal of the big chilean earthquake I just realized that we were all off

  2763   Sun Apr 4 17:32:07 2010 AlbertoMetaphysicsGeneralnew y-arm?


There's several more of the this vintage in one of the last cabinets down the new Y-arm.

 Hold on, did the arms get re-baptized?

  3592   Tue Sep 21 15:33:02 2010 steveMetaphysicsTreasureWagonga alart

John Miller has arrived from Australia with 3 bags of  Wagonga Coffee. Trade bargaining has started on

250 mgs of Sumatran Mandehling, Timur and Papua New Guine.

  3751   Thu Oct 21 10:44:56 2010 steveMetaphysicsTreasure1987 supernova tapes plus....?

I'm cleaning out to make room for our new optical cabinet. Are we keeping these? There are  ~20  pieces of 10" od 1" wide tapes and large number of cassettes.

AJW,  Zucker,  Stuart A and Koji were notified in this matter.

Alan suggested to save data of Bruce Allen paper of observation of binary neutron stars in the 40m on 1994 November 14-20 and save back up tapes of his period in the 40m.

Mike: reels are not readable any more, it is time to let go

  4257   Mon Feb 7 19:21:32 2011 Beard PapaMetaphysicsPhotosThe Adventures of Dr Stochino and Beard Papa

  4653   Fri May 6 15:42:55 2011 valeraMetaphysicsIOOInput mode cleaner length and 11 MHz modulation frequency

 After Kiwamu set the REFL11 phases in the PRMI configuration (maximized PRM->REFL11I reesponse) I tried to measure the MC length and the 11 MHz frequency missmatch by modulating the 11 MHz frequency and measuring the PM to AM conversion after the MC using the REFL11Q signal. The modulation appears in the REFL11Q with a good snr but the amplitude does not seem to go through a clear minimum as the 11 MHz goes through the MC resonance.

We could not relock the PRMI during the day so I resorted to a weaker method - measuring the amplitude of the 11 MHz sideband in the MC reflection (RF PD mon output on the demod board) with a RF spectrum analyzer. The minimum frequency on the IFR is 11.065650 MHz while the nominal setting was 11.065000 MHz. The sensitivity of this method is about 50 Hz.

  4978   Fri Jul 15 19:00:18 2011 dmassMetaphysicselogCrashes

Elog crashed a couple times, restarted it a couple times.

  5128   Fri Aug 5 20:44:26 2011 jamieMetaphysicsTreasureFilm crew here Monday morning

Just a reminder that a film crew will be here Monday morning, filming Christian Ott for some Discovery channel show.

They are slated to be here from 8am to 12:30pm or so.  They will take a couple of shots inside the lab, and the rest of the filming should be of Christian in the control room (which they will "clean up" and fit with "sexy lighting").  I will try to be here the whole time to oversee everything.

  5129   Fri Aug 5 22:54:29 2011 kiwamuMetaphysicsTreasureCrane crew here Monday morning

Also, according to Steve, there will be some crane guys for fixing the Y end crane issue (#5124) Monday morning.

Quote from #5128

 a film crew will be here Monday morning. They are slated to be here from 8am to 12:30pm or so. 

  5139   Mon Aug 8 13:24:00 2011 steveMetaphysicsTreasure Monday morning


Just a reminder that a film crew will be here Monday morning, filming Christian Ott for some Discovery channel show.

They are slated to be here from 8am to 12:30pm or so.  They will take a couple of shots inside the lab, and the rest of the filming should be of Christian in the control room (which they will "clean up" and fit with "sexy lighting").  I will try to be here the whole time to oversee everything.

Konecrane Fred was early this morning. He diagnosed the ETMY crane horizontal drive gear box dead and left just before the film crew showed up.

New gear box should be here by the end of this week for installation.

The lab air quality is high ~20,000 counts of particles of 0.5 micron.  Keep an eye on this before you open the chamber.

  5750   Fri Oct 28 02:41:18 2011 SureshMetaphysicselogelog unresponsive: restarted

Elog did not respond despite running the /cvs/cds/caltech/elog/start-elog.csh  script two times.  

It worked the after the third restart. 

  6059   Thu Dec 1 12:27:51 2011 ZachMetaphysicsRF SystemRAM diagnosis/suppression plan?

It seems like there is some confusion---or disagreement---amongst the lab about how to proceed with the RAM work (as Rana mentioned at the TAC meeting, we will henceforth refer to it only as "RAM" and never as "RFAM"; those who refuse to follow this protocol will be taken out back and shot).

I would like to provide a rough outline and then request that people reply with comments, so that we can get a collective picture of how this should work. I have divided this into two sections: 1) Methodology, which is concerned with the overall goal of the testing and the procedure for meeting them, and 2) General Issues, which are broadly important regardless of the chosen methodology.

1. Methodology

There are two broad goals:

  • Characterization of extant RAM
    • Measuring the RAM levels existing in an aLIGO-type interferometer without any suppression systems
    • Modeling to estimate the effect on IFO control and corroboration with measurements where possible
      • DC RAM levels contributing offsets to IFO operating point
      • Quasi-DC RAM levels affecting long term detector tuning (e.g., sensing matrix, MICH -> DARM feedforward, etc.)
      • Audio-frequency RAM contributing noise directly via error point modulation
    • Modeling to scale/adapt results from 40m -> aLIGO
  • Mitigation
    • Developing and assessing systems for suppressing RAM
      • Passive: thermal shielding and isolation
      • Active: EOM temperature control
        • Simple temperature stabilization
        • RAM error signal

The question is: which is our goal? The first, the second, or both? If both, what priority is given to which and can/should they be done in parallel? Also, task distribution.


2. General Issues

These are loosely related, so they are in random order:

  • Sensing
    • Temperature
      • What is the priority/urgency of a precision AC-bridge-readout temperature sensor?
      • If priority/urgency is low, what is the priority/urgency of upgrading breadboard controller to protoboard version? The common answer will be "make the protoboard version now", but if the urgency of the final AC sensing is high, it may make sense to focus on finalizing that design (after all, other experiments are waiting on a precision temperature controller, and it is not cost-effective to make many temporary controllers as I have done for the 40m).
      • Sensor noise issues
        • What is the sensor-noise-limited temperature stabilization level?
        • What is our willingness to tolerate the thermal low-passing of the EOM can itself (i.e., what is our sensitivity to gradients)?
        • To answer the above questions, we need to perform stabilization tests with several sensors on the same can, with some in loop (averaged) and some out of loop.
        • If we determine that gradients are a problem, we may need to:
          • Design a casing for outside the EOM (inside the foam box) to make the heating uniform, or
          • We may be able to get away with a more customized heater (instead of heating the can from one side as we do now).
    • Optical RAM
      • Stochmon is a nice diagnostic tool, but do we want something better? In particular, we want to have linear signals about a zero-DC-RAM point, which requires phase
        • Where will this sensor be located?
        • What kind of PD will it be? Broadband? Multi-resonant?
        • What sort of electronics will we need? If we are going to use this as an error signal for controlling the EOM temperature, it is just as important as any other IFO readout, since it may couple into all of them.
          • RF pickup is a BIG ISSUE HERE
          • How will the demodulation phases be selected? It should be possible to take TF measurements in certain misaligned (i.e., non-resonant) conditions and adjust the relative phase between the RAM readouts and standard IFO RF readouts such that they are in phase, but this will require some thinking.
          • Lots more, I'm sure
  • Control
    • Method (overlaps some with methodology portion)
      • What is better, simple temperature stabilization or RAM feeback? (More likely, "how much better is RAM feedback?")
      • If RAM feedback is difficult or impossible to implement effectively (see below), is temperature stabilization good enough?
    • Regime
      • Depending on extant RAM levels and on achievable sensing noise, it will be unwise and/or unnecessary to have a RAM control bandwidth above some relatively low frequency (~sub Hz)
        • Gain where RAM suppression is not needed only injects noise into the system
        • This cutoff frequency is largely determined by the thermal response of the system, but additional filtering will likely be necessary to reduce higher-frequency noise coupling (e.g., nonlinear downconversion of high-frequency signals into heater dissipation, etc.)
    • Efficacy
      • If we do RAM feedback, which signal (i.e. which frequency and quadrature) do we minimize?
        • Do we achieve large common-mode reduction across all RF signals, or is there some differential component?
        • In particular, do we make some or all other control signals noisier by stabilizing/minimizing RAM in one channel?
        • If the answer is yes, can we derive an effective control signal from a linear combination of some or all individual RAM signals?


There are probably many other issues I have neglected, so please comment on this rough draft as you see fit!

  6069   Mon Dec 5 09:46:21 2011 ZachMetaphysicsRF SystemRAM diagnosis/suppression plan?

Since no one has made any comments, I will assume that everyone is either 100% satisfied with the outline or they have no interest in the project. Under this assumption, I will make decisions on my own and begin planning the individual steps in more detail.

In particular, I will assume that our goal comprises BOTH characterization of RAM levels and mitigation, and I will try to find the best way that both can be achieved as simultaneously as possible. 

  6722   Thu May 31 00:56:13 2012 JamieMetaphysicsComputersPlease remember to check in code changes

I know it's really hard to remember, but our future selves will thank us dearly if we remember to commit all of our code changes to the svn with nice log messages.  At the moment there's a LOT of modified stuff in the userapps working directory that needs to be committed:

controls@pianosa:/opt/rtcds/userapps/release 0$ svn status | grep '^M'
M       cds/c1/models/c1rfm.mdl
M       sus/c1/medm/templates/SUS_SINGLE.adl
M       sus/c1/models/c1mcs.mdl
M       sus/c1/models/c1sus.mdl
M       sus/c1/models/c1scx.mdl
M       sus/c1/models/c1scy.mdl
M       isc/c1/models/c1pem.mdl
M       isc/c1/models/c1ioo.mdl
M       isc/c1/models/ADAPT_XFCODE_MCL.c
M       isc/c1/models/c1oaf.mdl
M       isc/c1/models/c1gcv.mdl
M       isc/common/medm/OAF_OVERVIEW.adl
M       isc/common/medm/OAF_DOF_BLRMS.adl
M       isc/common/medm/OAF_OVERVIEW_BAK.adl
M       isc/common/medm/OAF_ADAPTATION_MICH.adl
controls@pianosa:/opt/rtcds/userapps/release 0$ 

This doesn't even include things that haven't even been added yet.  It doesn't take much time.  Just copy and paste what you elog about the changes.

  7301   Tue Aug 28 18:28:21 2012 janoschMetaphysicsRingdownripples

Let's see if the ripples observed in the MC ringdown can be due to tilt motion of the mirrors.

The time it takes to produce a phase shift corresponding to N multiples of 2*pi is given by:

t = sqrt(2*N*lambda/(L*omega_T^2*(alpha_1+alpha_2)))

L is the length of the MC (something like 13m), and alpha_1, alpha_2 are the DC tilt angles of the two mirrors "shooting into the long arms of the MC" produced by the MC control with respect to the mechanical equilibrium position. omega_T is the tilt eigenfrequency of the three mirrors (assumed to be identical). lambda = 1.064e-6m;

The time it takes from N=1 to N=2 (the first observable ripple) is given by: tau1 = 0.6/omega_T*sqrt(lambda/L/(alpha_1+alpha_2))

The time it takes from N=2 to N=3 is given by: tau2 = 0.77*tau1


First, we also see in the measurement that later ripples are shorter than early ripples consistent with some accelerated effect. The predicted ripple durations tau seem to be a bit too high though. The measurements show something like a first 14us and a late 8us ripple. It depends somewhat on the initial tilt angles that I don't know really.

In any case, the short ripple times could also be explained if the tilt motions start a little earlier than the ringdown, or the tilt motion starts with some small initial velocity. The next step will be to program a little ringdown simulation that includes mirror tilts and see what kind of tilt motion would produce the ripples exactly as we observe them (or maybe tilt motion cannot produce ripples as observed).

ELOG V3.1.3-