40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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ID Date Authorup Type Category Subject
  2236   Mon Aug 13 01:53:21 2018 ranaDailyProgressWOPOzero-span spec OR RF bandpass

I know the squeezing people often use the zero-span feature of a spectrum analyzer to produce their McDonalds plots, but why not just use a LC bandpass (e.g. a 1 MHz wide mini-circuit filter)?

The transimpedance amp could drive a mini-circuits amp which then drives the bandpass into a RMS->DC circuit (some diodes). Then you can plot it on a scope easily. Maybe not worth it for this first measurement.

  2308   Wed Mar 20 19:17:50 2019 ranaNoise Budget2micronLasersNoise budget for the frequency discriminator

I think the dark noise should be very close to the shot noise and also have the same transfer function.

Also, the room temperature fluctuations are probably large at low frequencies. What PSD for room temperature did you use?

 

  2325   Wed Apr 10 18:58:48 2019 ranaUpdate2micronLasersIntensity noise stabilization of 2 micron source

OK...but how will the amplitude stabilization be done? How about a diagram showing the feedback loop and electronics?

  1. what is the feedback circuit?
  2. Can it drive the low impedance of an AOM driver?
  3. What is the photodiode?
  4. It has to be an AC coupled feedback (DC coupled is always terrible).
  5. What is the requirement on the intensity noise as a function of frequency?
Quote:

[Aidan, Anjali]

  • Attachment #1 shows the cleaned up setup for  2 micron experiment
  2326   Thu Apr 11 20:50:17 2019 ranaHowtoGeneralhow to learn quickly

https://maglab.caltech.edu/human-magnetic-reception-laboratory/

  2330   Wed Apr 24 19:30:55 2019 ranaLab InfrastructureHVAChowto get temperature trends

We need to get the temperature data from the sensors that Aidan setup. I have got it by downloading a sketchy HOBO app onto my phone. In order for this to work you have to go stand next to the sensors and download via bluetooth. There is no "pairing" required - the app seems to recognize the sensors nearly immediately.

and please, Aidan and everyone else, please do not use double-sticky tape or glue or bubble gum to attach sensors in a clean optical setup. We're going to have to make a mess to remove these.

I've just downloaded more data (attached). The lab seemed sort of cold and the south HEPA output was blowing colder air than the north HEPA output.

I've changed the temperature from 70F to 73F at 7:45 PM today. Lets see how it goes.

Attachment 1: QIL_temperature_190424.tgz
  2334   Sun May 5 20:52:16 2019 ranaNoise Budget2micronLasersFrequency noise measurement of 2 micron source

Looks good! A few comments:

  1. The LPF should be a 1.9 MHz LP from Mini-circuits
  2. The SR560 should be set with a 1 MHz low pass only
  3. No Rubidium needed. We just want to use two IFR/Marconi synthesizers so that they can share the same time standard.
  4. We will need a RF Amp to drive the AOM hard enough - check the manual and see what level is required to get the max diffraction.
  2335   Sun May 5 20:58:20 2019 ranaLab InfrastructureHVAChowto get temperature trends

the temperature has stabilized, although the fact that there is a sign error in one of the HVAC actuators means that there is a big delta T in the lab. I will contact facilities again.

the change on April 24 is me adjusting the setpoint on the south wall from 70 to 73F.

Quote:

We need to get the temperature data from the sensors that Aidan setup. I have got it by downloading a sketchy HOBO app onto my phone. In order for this to work you have to go stand next to the sensors and download via bluetooth. There is no "pairing" required - the app seems to recognize the sensors nearly immediately.

and please, Aidan and everyone else, please do not use double-sticky tape or glue or bubble gum to attach sensors in a clean optical setup. We're going to have to make a mess to remove these.

I've just downloaded more data (attached). The lab seemed sort of cold and the south HEPA output was blowing colder air than the north HEPA output.

I've changed the temperature from 70F to 73F at 7:45 PM today. Lets see how it goes.

the python script in the attachment will now scrub the data file for bad lines and make this kind of plot. IT works on .csv files, but none of the other HOBO formats.

Attachment 1: HVAC-B265B.pdf
HVAC-B265B.pdf
Attachment 2: plotTemp.tgz
  2339   Fri May 10 18:39:10 2019 ranaLab InfrastructureHVAChowto get temperature trends

Modesto came back this morning. We were still getting 1 hot blower and 1 cold blower.

As it turned out, although hot water was reaching the south heating coils input, it was not getting into the actual heating duct (as we could tell from touching those coils).

Modesto tapped the actuation valve with a hammer and it seemed to loosen it up. We will record temperature over the weekend.

Also we noted that the damper valve near the south-east vent was adjustable, but had no effect on the output air velocity so we assume its busted inside - Modesto will crack it open to investigate.

We also reduced the flow of hot water to the north blowers since they always seemed to be hotter. This may balance the actuators somewhat.

Modesto also replaced the thermostat on the west wall, but no real effect. I have adjusted the setpoint from 74 to 71F around 1800 today.

  2341   Tue May 14 13:10:36 2019 ranaLab InfrastructureHVACHVAC debuggin

fixed (?) HVAC problems (~1700 Monday) by better attaching a pneumatic hose that actuates the hot water flow for the south blowers

update on Tuesday: problem not fixed. Bumping the actuator there makes the thing work for a few minutes, but then it freezed again.

Attachment 1: HVAC-B265B.pdf
HVAC-B265B.pdf
  2365   Tue Jun 25 19:56:23 2019 ranaElectronicsCleanlinessMoku Out

I've removed the Moku and its iPad from the lab to see what its up to noise-wise.

  2380   Tue Jul 30 20:42:06 2019 ranaDailyProgress2micronLasersNoise Analysis of Circuit using SR785 Spectrum Analyser and Zero Simulation

Oh no! We've lost all of the low frequency data (which is the whole point of this experiment) and all of the contributing noise sources to the circuit!

  2382   Thu Aug 1 13:01:15 2019 ranaDailyProgress2micronLasersNoise Analysis of Circuit using SR785 Spectrum Analyser and Zero Simulation

always keep the start frequency at 0 Hz no matter what the span, as I was showing you yesterday in the lab. Otherwise, the bin centers end up in weird places.

  2401   Thu Aug 15 08:03:13 2019 ranaNoise Budget2micronLasersNoise Analysis of Voltage Regulator Circuit using SR785 Spectrum Analyzer
I'm glad to see that the voltage regulators can give good noise performance. I wish I understood what the gain peaking features came from - maybe the choice of capacitors?
  2415   Wed Sep 4 22:14:12 2019 ranaLab Infrastructure QIL lab floor plan

what about attaching a crane to the ceiling on one of the supporting beams?

 

  2417   Thu Sep 5 15:40:22 2019 ranaNoise BudgetPD noiseNoise Analysis of transimpedance amplifier

I'm pretty sure that the OP27 data is still not right. You should use the small binwidth and larger # of averages as we talked about earlier this week. In the elog, you should give the PSD parameters.

  2418   Sun Sep 8 16:08:04 2019 ranaElectronicsGeneralSolder: what kind of solder to use and why?

This is a summary of some information on types of solder and their usefulness.

Summary: use the 63/37 Sn/Pb solder from Kester. It is eutectic and has a low melting point so that your opamps won't get damaged.

Eutectic:

We want our solders to be "eutectic" so that it goes from the liquid phase directly to solid with no intermediate slurry. This makes a reliable (and nice looking!) solder joint.

Lead:

The tin-lead solder is a good combo.

 

Links:

  1. Basics of solder choice from Hackaday
  2.  NASA's Tin Whiskers homepage
  3. "Tin Whiskers are Real & Complex" Maxim
  2431   Fri Oct 11 17:33:47 2019 ranaDailyProgressCryo vacuum chamberClosing the vacuum chamber

we'll suffer if we use a oil based pump long term - please find and order a dry pump to back this turbo. Not only is it bad for the vac chamber, its bad for other optics in the lab,

  2477   Wed Dec 11 19:50:25 2019 ranaHowtoCryo vacuum chamberProcedure to record photodiode output vs temperature

don't we also want to record the dark noise spectrum as a function of T and V_Bias ? I would guess that the dark noise doesn't always scale with dark current at low frequencies since its probably more like a random walk than shot noise.

  2511   Wed Oct 28 14:05:19 2020 ranaSummaryECDLEffects of chosen AUX finesse and source on Calibration requirements
Quote:
 

would be easier to achieve there with higher laser powers and higher cavity finesse.


But I haven't attempted that here as we do not know our NPRO PZT's resonance features yet.

I don't know why it would be easier to have higher finesse with longer arms. Something about beam size???

The NPRO PZT TF's are all in the 40m elog - there are many measurements of TF made over the past 10 years. Its like Raiders of the Lost Ark - you have to believe its there while searching.

  2525   Tue Dec 22 10:42:17 2020 ranaSummaryGeneralInstrument loan

I was thinking about getting this new current pre-amp from NF:

http://www.nfcorp.co.jp/english/pro/mi/loc/pre/ca5351/index.html

It seems to have a good noise performance and has a built in low pass filter and also a remote interface.

The FEMTO seems less fancy, but their noise performance is actually 2-3x better.

Quote:

FEMTO DLPCA200 low noise preamp (brand new)

Keithley Source Meter 2450 (brand new) => Returned 11/23/2020

were brought to the OMC lab for temporary use.

 

  2527   Tue Dec 29 17:53:21 2020 ranaSummaryGeneralInstrument loan

doesn't seem so, but they sell this one:

http://www.nfcorp.co.jp/english/pro/mi/loc/m_lp/p_lp/lp_6016_01/index.html

which has a USB interface and pretty good voltage noise spectrum

 

  2532   Fri Feb 5 14:13:08 2021 ranaDailyProgressCryo vacuum chamberSuccessful cooldown in

is the x-axis in units of seconds? I think if we are clever, we should be able to look at a couple of the thermal time constants and figure out where the heat leaks are.

 

  2553   Fri Apr 9 16:23:22 2021 ranaDailyProgress2um PhotodiodesOpened cryo chamber and removed old PD

To aid in taking photos of these diodes, I put a USB microscope on Anchal's desk - you can grab it from there. I use it with mac Photo Booth, but it should be easy to use with any camera application.

Also, I recommend buying a macro lens(es) for cell phones from Amazon or B&H.  Label them with the QIL lab sticker so they don't disappear.

  2564   Wed May 5 00:34:14 2021 ranaSummary2um PhotodiodesUpdated PD testing schematic / measurement table

Looks very clear, thanks. I guess the next thing to do is

  1. ask if this will work for all the various PDs we want to test,
  2. is it good enough for all our requirements, and then we
  3. draw a new diagram for the new setup, incorporating what to keep and what circuit to make ourselves
  2566   Mon May 10 15:38:36 2021 ranaSummary2um PhotodiodesKeithley connections

Note that the back panel connectors are Triax, not the usual Coax.

  2575   Mon May 24 16:49:17 2021 ranaDailyProgressCryo vacuum chamberWeekend cryo chamber cooling

exp plot tip: If you use the "grid" feature of matplotlib and plt.semilogy(), the exponentials will look like straight lines, so we can just read off the time constants with a ruler.cool


Also, as we talked about earlier today, we should make some analytical estimates for the various heat loads, and also put them into the model.

For protecting from radiation, all of the surfaces which are NOT shiny-polished should get wrapped in something shiny (UHV Al foil, with the shiny side out).

I suggest wrapping with foil:

  1. Baseplate (to keep it from radiating into the cold plate (the tapped work surface))
  2. Copper strap (after first wrapping it with a sheet of Mylar to block conduction to the foil). Al foil should be wrapped with shiny side out.
  3. Plastic spacers. wrap around the length, but not the ends.
  4. Holes in the shields where the thermal strap enters. Edge the holes with a G-10 ring/grommet to prevent touching the straps.

I attach here a photo of the radiative shielding of a Purple Pepper Plant (PPP), to reduce the radiative coupling to the environment. This prevents the soil from drying out in the sun so fast.

Attachment 1: PPP.jpg
PPP.jpg
  2581   Wed Jun 2 20:06:07 2021 ranaDailyProgressCryo vacuum chamberWeekend cryo chamber cooling

I'll be curious to see the results of Radhika's thermal model - I am suspicious of this thermal strap contact to the base plate. It would be good if we could instead make a copper mating plate:

  1. groovy milled out loop holder for the strap to go into such that the contact surface is larger
  2. flat base to get smushed into the colde plate
  3. thru holes so that it can be directly screwed down with some washers
  4. screwed down with a torque wrench so that we know that its really tight (i.e. "I think its pretty tight" doesn't really work when we want a good thermal contact)
  5. someone with a MechE degree calculates the proper torque such that we plasticly deform the copper and get it to sit more flush to the cold plate
  6. a cap for the copper plate that really smooshes the copper strap into the bottom part of the mating plate.
  2648   Fri Aug 20 13:44:58 2021 ranaDailyProgressCryo vacuum chamberCooldown model fitting for MS

I think the asymptotic temperature in the model is missing the data. i.e. the steady state temperature should match up, but the recorded data terminates too soon. Probably should figure out what the missing term is.

Can you post the covariance matrix of your fit so that we can see what the fractional errors are on the physical parameters? (i.e. construct the fit function so that physical parameters which are unknown are the fit parameters.)

  2660   Tue Sep 7 11:52:40 2021 ranaComputingCymacs+/-18V power supply to AI/AA chassis was actually +18V, -14.5V

We should not have a bench power supply installed permanently. Can you install a Sorensen in that rack or use one of the nearby ones?

  2670   Mon Sep 20 14:26:38 2021 ranaComputing2um PhotodiodesAutomation and analysis scripts for 2um data taking

you can put these in the GIT repo for the QIL Cryo tests that Radhika set up. Otherwise, they'll get lost. And we should probably change autorun to a .py script and document these in the README on the repo.

Quote:

The attached files are the scripts used to take data during the PD temperature cycling/testing and to retrieve and analyze data after the fact.

  • ~/JPL_PD/scripts/autorun2021.sh
    • ~/JPL_PD/scripts/piezo_mirror/maximize_output_power.py
  • ~/JPL_PD/data/A1_analysis/A1_analysis.py

 

  2681   Thu Oct 21 16:52:26 2021 ranaLaser2um PhotodiodesImproved measurement of QE on photodiodes ~89% at 140K

its worth looking into how fiber optic mode cleaning actually works:

https://doi.org/10.1201/9780203739662

In order to get a lot of cleaning you have to have a clean beam to begin with. There's a way to pre-clean by putting the laser output into a pinhole before coupling int othe single-mode fiber. Also, use a ~40-50m fiber to make sure the mod-mistanatched beam actually goes into the cladding rather than recombine into the Gaussian beam.

  2684   Fri Oct 22 12:04:13 2021 ranaLaser2um PhotodiodesImproved measurement of QE on photodiodes ~89% at 140K

agreed. You should put into Voyager chat and cryo/ET slack questins about 2 um beam profiling. We'll want it for anything 1.8-2.1 um.

Quote:

Definitely. I think the lack of beam profiling/imaging equipment is something we want to address too. We will waste a lot of time in Mariner if we can't profile our beams.

  2693   Fri Nov 12 10:54:55 2021 ranaSummary2um PhotodiodesResults from JPL PD: A1-Test3

IT would also be good if you could plot the RMS noise around 10 Hz and 100 Hz as a function of the bias and temperature, so we can see what the trends are. And how about post the data and scripts to the elog so we can munge data later?

  2699   Sun Dec 5 17:33:50 2021 ranaDailyProgressCryo vacuum chamberTransitioning MS cooldown fitting to MCMC scheme

thats looking good

You should try to use either the corner or getdist packages to plot the 'corner' plots commonly used when showing correlated posteriors (cf. https://emcee.readthedocs.io/en/v2.2.1/user/line/) so that we can see what's up with the other uncertainties

Quote:

This week I have been working towards a Markov-chain Monte Carlo (MCMC) approach for fitting Megastat cooldown data and obtaining estimates on various emissivity values. I started with a simple model, only simulating the radiative cooling from the inner shield to the test mass. I supply the test mass and inner shield temperature data, and the emissivity of Aquadag (coating both the TM and inner surface of IS) as the only fit parameter. I am using Stan for the modeling, and Attachment 1 is a copy of my stan model.

The results of the simple model are in Attachment 2. The emissivity of Aquadag is estimated as a gaussian centered around 0.7. I am still determining whether this result is "real", or if the simulation is simply returning my prior. I will look into this more before adding complexity to the model.

 

  2710   Fri Jan 21 17:32:40 2022 ranaDailyProgressCryo vacuum chamberHeat transfer between grease joints and pressure joints

Is there a units issue? 50 kg is a mass, but not a force.

  2711   Tue Jan 25 10:24:14 2022 ranaDailyProgressCryo vacuum chamberHeat transfer between grease joints and pressure joints

For one surface resting on another, the force of the contact is the grativational force of the top surface. There's an implicit factor of g that cancels out from the ratio, so it becomes a ratio of masses. The heat conductance listed for a 50 kg Al-Al pressure joint is interpreted as the heat conductance for a force of 50g.

Quote:

Is there a units issue? 50 kg is a mass, but not a force.

 

  2712   Tue Jan 25 13:15:40 2022 ranaDailyProgressCryo vacuum chamberHeat transfer between grease joints and pressure joints

I think its least confusing to just replace 50 kg g with 500 N. Writing 50 g can be misleading, it seems like 50 grams.

 

  2714   Fri Jan 28 10:31:15 2022 ranaSummaryTutorial videooh no, stap the units madness, aaaaahhhh!!! noooooo!!!!

What if I told you SI-units is way harder to miscalculate with - Matrix  Morpheus | Make a Meme

 

  2719   Wed Feb 9 15:21:27 2022 ranaHowtoTempCtrlplots

In the plots comparing data and models, can you use the legend to indicate which is which? e.g. use dots for data and solid lines for models, and then label them as that in the legend. Also nice to include error bars on the temperautre measurements; I think there's a python way to plot this as a shaded region as well.

  2721   Tue Feb 15 16:54:27 2022 ranaDailyProgressCryo vacuum chamberDoubled Thermal Linkage Capacity run started 11 Feb 2022

I've been assuming that the inner shield can be treated as a point mass, but perhaps the thinness make a significant delay between the temperature of the cold plate and the inner shield during the initial cooldown.

Could you model the cold shield to estimate what the temperature gradient would look like during the rapid cooldown? Not full 3D, but something approximate that takes into account the conductivity, thinness, and heat capacity.

  2747   Tue Apr 5 12:20:09 2022 ranaThings to BuyPurchasesNew optical table legs for north table

we don't really need Pneumatic legs. How much for rigid legs?

 

  2750   Wed Apr 6 10:31:55 2022 ranaDailyProgress Rerun of cooldown with indium gaskets in copper bar joints

I think this is a nice debugging find. Its not very robust to use the workstations as 24/7 script machines (as we have found out over the years).

Best is to install a conda env on the main framebuilder machine, and run the perpetual scripts there in a tmux session.

Once its all sehup, update the ATF Wiki with a description of haw its done. Workstations crash when users do stuff, so its better if the data gettin script can run as a system service (e.g. systemctl, etc)

  2754   Mon Apr 11 14:50:45 2022 ranaDailyProgressCryo vacuum chamberSi wafer emissivity testing

that's good. Can you from these models estimate what the uncertainty will be on the emissivity? i.e. by MCMC or otherwise rather than eyeballing

Quote:

I've modeled the cooldown of a 2" diameter and 4" diameter Si wafer in Attachments 1 and 2, using the current Megastat model and previous cold head temperature data. The model includes heat leaking into the inner shield enclosure from an aperture, which we currently observe in Megastat cooldowns. (Note how the wafer cools down much faster than the current test mass, due to the very tiny volume.)

  2770   Wed May 18 21:53:31 2022 ranaDailyProgressEmissivity estimationMegastat Inner Shield for emissivity estimation

I'd recommend drilling a through hole and using a nut, rather than tapping as I suggested earlier. The shield is not thick enough to have many 4-40 threads.

Is it better to have the inner shield inner surface low or high emissivity? \Depending on the effect on the MCMC uncertainties, we may want to make everything black, including the cold plate. i.e. we could mount something like black aquadag tiles on the cold plate.

 

  2776   Tue May 31 17:53:07 2022 ranaDailyProgressEmissivity estimationSi wafer emissivity testing

that's a good start, but we want the cooldown to be fast, so what we would need from the model is for you to change some parameters and find out what kind of possible physical changes we can make to make the cooldown fast. i.e. change some parameters and see what configurations would give a fast cooldown, and then we can discuss which of those is the easiest.

Quote:

[WIP]

I modeled the cooldown of a 2" Si wafer in Megastat with cooling from a) the existing cryocooler and b) LN2. The only difference between the two models is the temperature that the cold end of the copper bar "sees" - in the cryo-cooler case, I've used cold head temperature data from a previous cooldown; in the LN2 case, I've used 77K. In Attachment 1, the cryo-cooler models are solid lines and the LN2 models are dashed. 

It is clear from the plot that the cold head gets ~30K colder than LN2 at 77K. This explains the discrepancy between the inner shield models for the two cases at steady state. While the initial temperature rates of change are greater in the LN2 case, the cold head crosses the 77K line in roughly 5 hours.

Does the true cold-head temperature follow the model? Or is it less good than the model?

  2785   Fri Jun 10 16:23:04 2022 ranaDailyProgressEmissivity estimationMegastat cooldown - repainted inner shield aquadag, added aquadag foil to cold plate

From the plot, it seems like the slop is ~50 Ohms / 120 K. So a difference of 5 K corresponds to ~2 Ohms.

It could be that your measurement of the resistance is off slightly due to the lead resistances, etc. Are you using a 3-wire or 4-wire probe?

You can get a higher accuracy relative calibration by dunking all the RTDs together in ice water and then in boiling water.

https://us.flukecal.com/literature/articles-and-education/temperature-calibration/application-notes/how-calibrate-rtd-or-pla

 

  795   Wed Jun 2 20:24:26 2010 rana, alastairMiscGYROOptics moved

Today we moved some of the optics away from the blue box to make room for the mode matching.

We also found a 1" diameter optic in one of the cabinets with a transmission of 0.81 % (S-pol). This makes a nice match with the 0.57% transmission of the 2" diameter output coupler and so its now installed. We'll later replace it with a good 2" diameter mirror.

We also moved all of the optics after the laser to align with the screw holes and are trying to make the beams go along the screw hole lines.

Alastair has remeasured the laser beam profile after the EOM and the PBSs using the WinCamD beam scanner. Results are being produced.

  1287   Fri Feb 4 19:38:49 2011 rana, joeBComputingDAQfb0 problems fixed: daqd, nds, and atffe all now running

Summary:

  1. Frames were not being written. This was because of disk full conditions. We deleted old files and restarted everything.
  2. FB0 network setup wasn't good. Joe fixed this with ifconfig.

 


The script which cleans up the frame files (so that the disk doesn't become overful) was set to only delete files when the /frames/full directory was getting up to 99.7% of the full capacity. This is ridiculously close to the edge. We set it instead to be 95%. Here's the diff in the /target/fb/wiper.pl script:

fb0:fb>diff wiper.pl wiper.pl~
26c26
< $full_frames_percent_keep = 95;
---
> $full_frames_percent_keep = 99.7;
32c32
< $minute_frames_percent_keep = 0.2;
---
> $minute_frames_percent_keep = 0.005;

The DAQD process was spitting out core files and had also filled up the / partition on FB0. After deleting this the regular system processes were able to run. To check the disk space you can use 'df -h':

fb0:fb>df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                      224G   24G  189G  12% /
/dev/sda1              99M   28M   66M  30% /boot
tmpfs                1006M     0 1006M   0% /dev/shm
/dev/sdd1             1.4T  142G  1.3T  11% /frames/trend
/dev/sdc1             917G  707G  165G  82% /frames/full
fb1:/cvs              917G  104G  814G  12% /cvs

We found that although NTPD was running on FB0, it had been configured in some really screwy way. We used /sbin/ifconfig to remove the configuration for the other network devices (eth1, eth2, eth3) and set it so that FB0 only talks to the ATF martian network and the router. The router is now configured to NOT filter out the requests from FB0. Now the NTPD works and seems to be correctly fixing the computer's system time. There's still the issue that the ATF FE will change this time as long as the FE is running, but I guess the system clock will once in awhile get fixed when we restart the FE and NTP takes over.

 

Along the way, I also restored the Xinerama dual-head display on ws1. Alastair somehow believed that it had never been dual-head before, but in fact I elogged the procedure in September. Please don't do any auto-updates on any of these machines unless you know what you're doing. and are willing to fix things after breaking them.

I attached an image showing that I can, indeed, get real time data from one of the _DAQ channels of the gyro.

Attachment 1: Untitled.png
Untitled.png
  512   Sun Dec 27 23:47:34 2009 rana?LaserGYROSB frequency

Quote:

Quote:

That's a weird plot. I think we want to see the HOM of the SBs, not the carrier. Or rather, we want to see both but maybe not on the same plot. Are these the SB HOMs?

If so, I think its fine to have an 8th order HOM of a SB to have the same phase shift as the TEM00 SB.  I say that the frequency should be between 21 and 45 MHz.

 I had a rather lengthy discussion with Aidan, Frank and Koji about this the other day. The resonance peaks are resonances of the cavity for some higher order mode. They can be excited by either the carrier or the SBs impartially. This plot is equivalent to the ones that are in other elog entries (like John's from last year), but it is much less cluttered. Those plots show you exactly how far each higher order mode is from resonance for the carrier and each sideband, whereas this one shows you the resonance frequency of each cavity HOM, along with the frequency of the carrier and SBs, from which you can directly infer how far each one is from whichever mode peak. I think this is a clearer way of doing it, as it emphasizes that the resonances belong to the cavity, not to the light entering it. 

 No, I disagree. There should be a plot showing how the HOMs of the SBs show up in the cavity. A TEM01 of the +SB will be in a different place than the -SB TEM01 or the CR TEM01.

  45   Tue Apr 22 16:25:24 2008 robLaserPSLProfile of 35W PSL

Quote:
I scanned the beam on the 35W laser again (for the first time since it was fixed by our German friends during the LSC meeting).



What did they fix? And how?
ELOG V3.1.3-