40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  ATF eLog, Page 2 of 56  Not logged in ELOG logo
ID Date Author Type Category Subjectup
  1060   Wed Sep 15 23:23:30 2010 FrankLaserGeneral35W Laser ON

THE 35W LASER IS RUNNING

so plz be careful if working on that table.

Output beam is dumped into the power meter head using one turning mirror. Transmitted beam is used for beam analysis using the WinCam.
Current output power is 31W with rough alignment trough everything.

 

  391   Fri Oct 16 20:51:06 2009 FrankLaserGeneral35W laser & DAQ up and running

35W laser & DAQ system are up and running again. i have no access to the data on FB1 right now but FB0 is working. I have to ask Alex on monday. Services are up and running on FB1, port is open but i can't connect...

  301   Fri Sep 4 15:49:11 2009 FrankLaserGeneral35W laser - bad beam profile

while checking the data channels i had a quick look at the laser beam - it looks terrible and both the waveplate and the PBS scatter a lot of light! why didn't you use one of those high-power air-spaced polarizers instead of the cube? i will re-allign the laser next week - aside of this, why is there no beam dump for the beam reflected towards the edge of the optical table (dumped on the wall at the moment)? any reason or just forgotten? i placed a dump there so if someone needs this port for diagnostics or so feel free to remove it ...

  303   Fri Sep 4 20:36:55 2009 DmassLaserGeneral35W laser - bad beam profile

Quote:

while checking the data channels i had a quick look at the laser beam - it looks terrible and both the waveplate and the PBS scatter a lot of light! why didn't you use one of those high-power air-spaced polarizers instead of the cube? i will re-allign the laser next week - aside of this, why is there no beam dump for the beam reflected towards the edge of the optical table (dumped on the wall at the moment)? any reason or just forgotten? i placed a dump there so if someone needs this port for diagnostics or so feel free to remove it ...

 I assume you are talking about the reflection from the prism? If so, I thought I *had* put a razor blade there. If not, thanks for adding

  317   Wed Sep 16 12:09:21 2009 FrankLaserGeneral35W laser - laser update

here a short list of things happened the last couple of days:

  • l/2-waveplate right after the laser was broken - it already changed it's color - removed all that shit in order to measure the output power and beam profile
  • laser power was down to 22W(!) - readjusted the laser back to 27W, more is not possible at the moment - laser profile still not good
  • measured the pump power of each pump diode, all at 44A :
  1. LD1: 29.6W
  2. LD2: 30.3W
  3. LD3: 29.4W
  4. LD4: 30.0W
  • adjusted the polarization of each fiber - maximum output power 27.4W
  • identified the first polarizer of the isolator in the 35W laser as the source of the problem - a lot of the seed power is reflected there - changed the waveplate in front of it - no change, so it's the polarizer itself - loosing ~600mW there. Measured seed power after EOM: 1.9W, at the input of the 35W laser: 1.3W - typical total losses in the isolator are 3% to 5%, so 100mW or so max - no spare parts available
  • recabled the whole laser, cleaned up everything below and on the table, removed all unused cables (about 90% of all cables to the DAQ)
  • added a new cable tie based system mounted to the aluminum profiles of the enclosure - now we have easy access to all cables without throwing them all over the other equipment
  8   Thu Nov 8 18:54:41 2007 StefanLaserPSL35W laser ISS loop closed with LIGO ISS electronics
I closed the ISS loop using a iLIGO type ISS board, with an additional 2kHz pole at the last stage.

I haven't carefully measured noise or OLG yet, but it is not famous yet:
Looking at the in-loop diode I get a RIN of ~3e-7/rtHz at 100Hz, and ~1e-8 at 10kHz.

The gain is limited by two sharp resonances that rise at ~40kHz when the gain is increased.

TBD:
- Fix the ISS test point wiring - these cables have 800Ohm resistance!
(No not impedance... shield to core measures 800Ohms at DC...)
This brought back painful mamories from ~3years ago when we installed
the H1 ISS... apparently the known problem wasn't fixed on all versions.
- Measure OLG, in particular check whether weird AOM transfer function still
exists - it could be killing our gain.
- Measure sensing noise in-situ
- Install sensitive OL PD
  1124   Mon Nov 1 22:25:48 2010 FrankLaserGeneral35W laser ON

The 35W laser is on again.

Moved all equipment from EE lab back to the ATF and currently doing some tests. 
All the equipment next to the 35W laser table (near lab corner)  is in use  (automated measurements). 

Plz don't touch those things

  1484   Tue Aug 2 20:41:35 2011 FrankLaserPSL35W laser ready to ship

finished packing the laser and all accessories into two boxes. Had to re-arrange everything as i couldn't use the second wooden crate (wrong wood, not allowed to import into EU).
Below the serial numbers of the individual parts and the contents of the boxes:

Box 1 (wooden crate)

  • Control box (#CB-0507-001)
  • Diode box (#DB-0507-001)
  • Laser head (#EP-0507-001) (includes NPRO #1639D)
  • 2x network switch
  • 1x optical network fiber
  • 4x interlock cables
  • several D-Sub cables to connect everything
  • 2x water distribution block
  • 1x chiller adapter

Box 2:

  • NPRO power supply (#1639D)
  • 4x SMA pump fiber
  • 4x water hose
  • 1x NPRO cable

Pictures:

P1030890.JPGP1030901.JPG

P1040006.JPGP1040106.JPG

P1040105.JPGP1040098.JPG

P1040102.JPG

  28   Tue Feb 12 16:54:13 2008 DmassLaserPSL35W profile/waist
The beam output by the 35W in 058 was significantly elliptical (up to a 10% difference in the waist measurements). I used the profile given by the "more gaussian" axis, and found a waist 9.7 cm inside the front of the enclosure, 250 microns in radius. We ended up using this axis to mode match to, but this ellipticity will probably need to be addressed as we try to maximize the power output through the PMC.

[plots to be added]
  1333   Wed Mar 2 15:44:36 2011 FrankLaserMOPA35W-laser SOP (LIGO-M070352)

35W-SOP.pdf

35W-SOP.doc

  1472   Sat Jul 30 01:17:52 2011 FrankLaserPSL35W-laser almost ready to ship

The laser is almost ready to ship. I reorganized the stuff so that i don't need a second wooden crate for the heavy diode box. Now the diode box, control box and the laser head itself fits into the single one we had.
I only need one final top layer of 1" thick  Styrofoam which i don't have at the moment. I only have 1.5" and 2". Will organize that on the WE and then we can finally ship everything on Monday when Rod Luna is back.

  1540   Fri Sep 16 01:38:25 2011 ZachLaserGYRO3f demod and other tests

I found out that the issue I was having with the distorted error signal was mainly user error. I have been feeding the output of the mixer for the primary loop through parallel summed SR560s so that I can add low frequency gain, and I had forgotten to remove the extra integration before sweeping the cavity. So, the error signal as measured at the input monitor of the PDH box looked like junk. It looked fine once I removed the extra LF gain.

Before I figured this out, I did some more poking around to find the root of the AM I was getting when sweeping the laser frequency, and it looks like Alastair was correct about the laser output polarization rotation theory. To recap, I traced the AM all the way back to the initial PBS, where I saw it at the transmitted end but not in the reflection. Of course, it WAS there in the reflection, only at a much smaller relative level since we are dumping the majority of the power (i.e., cos(dtheta) vs. sin(dtheta) ).

I thought it might be worthwhile to check and see if this was causing any measurable effect on the gyro performance, so I ran a quick test. First, I locked the gyro as usual and measured the noise---first just using the PDH box (RED) and then with the extra SR560 boost (GREEN). Then, I placed a strong ND filter in the beam path before the EOM and increased the input power via the first HWP to compensate, thus reducing the relative AM effect (BLUE). The only obvious difference seems to be that the peak between 30-40 Hz goes away. I'm not exactly sure what this means, but the unfortunate important result is that it makes no difference to the LF spectrum. Sad.

config_tests_9_15_11.pdf

 

I then gave up with the power adjustment stuff and did a rather hasty 3f demod test. As background, it is claimed by the mystics of frequency stabilization that demodulating at the third harmonic of the modulation frequency somehow reduces the influence of things like RAM and scattered light. At least as far as RAM is concerned, I can see no reason why this could be true, since in the best case signal goes down at the same rate as noise, but people report data showing that this works.

We are using a 2-channel Tektronix FG as the local oscillator for the gyro, so all I had to do was use the second channel at 3x the frequency (3 x 29.489 MHz = 88.467 MHz) and adjust the relative phase, taking into account the proper amplitudes for each signal. I found that the phase shifters in the PDH boxes did not behave correctly at such high frequencies, so I bypassed them and the ERA amps and plugged the LO directly into the mixers at 13 dBm. Below is a plot of the gyro noise in three cases: 1) standard 1f for both loops, 2) 3f for the primary loop and 1f for the secondary loop, and 3) 3f for both loops. 

3f_demod_9_15_11.pdf

It's not definitive, since achieving the same loop gain for the two frequencies requires totally redistributing the gain ratio between the optical response and the servo (e.g., the floor of the green curve above 10 Hz is most likely just the dark noise of the secondary PD), but it doesn't seem that going to 3f makes things better in any band. It doesn't seem to hurt that badly, so maybe this means we should do a more thorough test where we use the gyro RFPDs (which can handle much more power) tuned to 3f as would actually be the case if we chose this option.

 

 

  748   Tue May 4 12:06:37 2010 ZachLaserGYRO6-m mirrors are OK--back to the drawing board

 Before doing the full T vs. angle test on the 6-m mirrors we have been using (so that we could send them back to CVI), I figured I would just test them at 45°, outside of the cavity, using the same simple configuration I used to measure the new 9-m mirror. What I found was that---for both 6-m mirrors---the transmission was in the range of 50 - 100 ppm, roughly independent of angular tuning away from 45° on the order of +/- 5°. This is pretty much consistent with the part specifications from CVI for Y1S, especially considering that they have been on our table for a couple months.

So.. why did we observe a disproportionate amount of light escaping these mirrors with the cavity locked? Good question. We suspect that it might have something to do with polarization issues, as a macroscopic polarization shift in the cavity would certainly account for the spurious transmission.

I don't know much about what could cause this, but I am reading. The good news is that our mirrors are all what they are supposed to be (yippidy doo da).

  749   Wed May 5 15:09:35 2010 ZachLaserGYRO6-m mirrors are OK--back to the drawing board

Haven't found anything in the literature supporting a polarization rotation in a planar cavity, with the exception of one article discussing the effect in rotating ring cavities(!). I highly doubt that the earth's rotation would cause such a major effect via this pathway (if it did, then we could build a pretty sensitive gyro just by measuring the polarization angle shift!).

It also seems unlikely that the plane of the high-extinction PBS we used to isolate the S beam for the input should be misaligned with respect to the cavity plane by enough to account for this effect. I was going to crunch some numbers (i.e., calculate the P-finesse of the cavity and thereby determine the expected transmission through the cavity mirrors of some residual P input light), but it is difficult to find data for Y1(S)-S transmission of P. Not to fear, as we can just measure this.

It appears there was a momentary lapse of experimental reason when we all first measured the excess transmission, as there is no record of the measured output in the elog, nor did we measure the polarization of the escaping light. I suppose it was just easier to say "damn those CVI bastards and their crappy crap".

Troubleshooting scheme:

  • Measure TP for Y1, Y1S cavity mirrors, and calculate expected cavity P-belching for a conceivable residual P in the input beam.

If the result seems consistent with observation, then we simply use the cavity itself as a polarization reference for the input beam (as we perhaps should have done in the first place). If this doesn't account for the effect:

  • When we get the cavity set up again (after moving it down the table), and inevitably observe the same problem, GET NUMBERS FOR THE TRANSMISSION AND DETERMINE THE POLARIZATION
  • Use the aforementioned information to figure out WTF is going on.

Quote:

 Before doing the full T vs. angle test on the 6-m mirrors we have been using (so that we could send them back to CVI), I figured I would just test them at 45°, outside of the cavity, using the same simple configuration I used to measure the new 9-m mirror. What I found was that---for both 6-m mirrors---the transmission was in the range of 50 - 100 ppm, roughly independent of angular tuning away from 45° on the order of +/- 5°. This is pretty much consistent with the part specifications from CVI for Y1S, especially considering that they have been on our table for a couple months.

So.. why did we observe a disproportionate amount of light escaping these mirrors with the cavity locked? Good question. We suspect that it might have something to do with polarization issues, as a macroscopic polarization shift in the cavity would certainly account for the spurious transmission.

I don't know much about what could cause this, but I am reading. The good news is that our mirrors are all what they are supposed to be (yippidy doo da).

 

  1589   Wed Jan 18 01:16:56 2012 ZachLaserIodine700-mW SOP written

I modified the old gyro NPRO SOP into one for the 700-mW NPRO that we will use as part of the iodine setup. It is on the DCC. I informed Peter King, whose signature it awaits.

  2137   Tue Jul 11 12:25:29 2017 awadeHowtoGeneralA Note On Plotting

There is no universally perfect plot and some details are a matter of taste.  However, bad plots often miss a few important features.
This is a checklist of features a plot should have. Hopefully this is useful to SURFs and new students.
If you have anything to add please edit this post and leave a note at the bottom.
Plots should have: 
  • large 16-20 point font on ticks and labels (bigger for titles);
  • always include units in axis labels (e.g. axislabel = 'Photo detector signal [V]'), if units are arbitrary then be explicit use 'a.u.';
  • axes need tick marks;
  • Scale data to cover most of the area. It probably should hit the very edge of the plot, but squashed up data is imposible to read. Matlab leaves a small gap at the edges, you need to set axis range manually.
  • thicken data lines (unless doing so obscures details of the data);
  • data points should usually be discreet points and not connected lines. It is ok to have lines for PSDs and time series. However, for most measurements with distinct measurement events those points usually should not be connected to distinguish data from fitted lines;
  • include a legend (almost always);
  • use pleasant harmonious colors, this is no-longer the 1990's and computers can do other colors now;
  • grid lines are good, especially for log plots, set the gamma to 0.2-0.4 or black-grey 0.3 so they sit in the background;
  • error bars (always);
  • if you include a fitted function put the equation on the plot along with fitted parameters and their uncertainties;
  • when making a Bode check use tick marks that are round numbers of 5s or 10s of dB (smaller gradations are ok as long as they sensibly spaced graduations around 0 dB and the grid lines match up); ticks of 2.314 dB, 2.317 dB , 2.320 dB are not ok.  Phase is often expressed in degrees and should be centered around zero on the y-axis with sensible graduations spanning ±180 degrees.  Never plot angle and magnitude on the same axis, it should be a two panel plot;
  • choose a standard aspect ratio (unless it makes sense to do otherwise): 16:9, 4:3 or the golden ratio (google it)
  • NEVER POST PLOTS AS JPEG OR BITMAP TO ELOG, if this were ancient Roman times this would be a crucifixion offense, always produce vector graphics. PDF IS HIGHLY PREFERABLE TO EPS (see 40m:12506);
  • Do not post plots of size greater than 1 MB, there is rarely a reason for a plot to be this big, you are a bad person if you force 1 MB plots on other peoples servers and computers. It could be you have plotted all million points in your dataset or it has rendered wrong. To fix this maybe try use: Imagemagick "convert -layers Optimize input.pdf output.pdf" .
  • title the plot and name file descriptively with date included (i.e. filename = 'plotyyyymmdd_ThisImportantThingIMeasured.pdf', title = 'This Important Thing I Measured (yyyymmdd)'). Remember, people from Mother England and Her colonies can't read dates properly (they do dd/mm/yyyy) so find a date convention that is explicit and minimizes confusion.
  • package the data and plotting code in a .zip or .tar attached to the same elog post (unless it is very large, >4 Mb), parcels of data stored in your personal directories are not useful to other people; and
  • step back and contemplate, does this plot convey information quickly and efficiently

 

Note that on the LIGO Caltech nodus elog it is possible to embed plots but you need double check to see if it is attached at the bottom.  Some embedded graphics can’t be clicked on to expand which is a a problem.  Sometimes it is easiest to just attach it at the bottom.

Edit Tue Jul 11 16:03:52 2017: Plot file size suggestion from Criag
Edit Thu Jul 13 10:29:31 2017: bode plots suggestion Gautam
​Edit Mon Mon Jul 17 15:30:12 2017: more on bode plots
Edit Wed Apr 25 12:41:41 2018: Added note about plotting data points as discrete seperate elements instead of connected lines
  2610   Tue Jul 20 11:33:52 2021 KojiSummaryCryo vacuum chamberA cooling model (Temp Log 210716_2255)

A naive cooling model was applied to the cooling curve.
A wild guess:

- The table temp is the same as the test piece temp as measured on 2021/7/9
- The inner shield temp is well represented by the table temp
- The specific heat of Si is almost constant (0.71 [J/(g K)] between 300K~200K

Radiative cooling:
The curve was hand-fitted by changing the emissivity of the inner shield and the silicon mass. I ended up having the same values for these to be 0.15.
Surprisingly well fitted!

Conductive cooling:
The conductive cooling through the wire does not fit the cooling curve, although the quantitative evaluation of the wire conductivity needs to be checked carefully.

Appendix:
Stephen shared attachments 2 and 3, which contain insights on the wire used to hang the Si mass. .017" diameter Music Wire from California Fine Wire, 2004 vintage, borrowed from Downs High Bay.

Attachment 1: cooling_model.pdf
cooling_model.pdf
Attachment 2: IMG_9390.JPG
IMG_9390.JPG
Attachment 3: IMG_9391.JPG
IMG_9391.JPG
  2611   Tue Jul 20 17:28:30 2021 KojiSummaryCryo vacuum chamberA cooling model (Temp Log 210716_2255)

Updated the model the latest log data with cooling prediction

  • The radiative cooling is expected to be the dominant cooling mode.
  • It will take ~3 more days to reach 123K. We don't need to wait for it.
  • For more informative temp data, we need the temperature of the inner shield and the table.

  • We know the cold head temp from the measurement. For the prediction, the constant cold head temp of 65K was assumed.
  • The table temp was estimated using conductive cooling model + linear empirical dependence of the conductivity on the temp
  • The constant specific heat of the silicon mass (0.71 J/K/g) was assumed. This may need to be updated.
  • The radiative cooling is given from Stefan–Boltzmann law with the emissivity of 0.15 for both the shield and the mass.
     
  • The conductive cooling of the test mass was estimated using: Wire diameter 0.017" (=0.43mm), 4 wires, length of ~10cm (guess), no thermal resistance at the clamps (-> upper limit of the conductive cooling)

Radiative cooling already gives us a good agreement with the measured temp evolution for the test mass. The conductive cooling is not significant and does not change the prediction.


Updated the plot with the new data (2021/7/21 12:30PM)

Attachment 1: cooling_model.pdf
cooling_model.pdf
  1779   Fri Oct 19 18:07:10 2012 KojiLab InfrastructurePEMA huge current driver and coil magnet actuators are missing

I found some lab infrastructure like a huge current driver and coil magnet actuators went somewhere.

And a floppy disk drive too.

  666   Thu Mar 11 14:52:28 2010 ZachLaserGYROA tale of two PDs

Sitting by the fireside alone in his study, scratching his head between puffs of fine Turkish tobacco drawn from his handcrafted rich mahogany pipe, Alastair realized that one of our PDs didn't even have an amp in it. We now have two PDA10CSs for the REFL PDs and the cavity is locking in one direction again, though we had to reduce the modulation frequency to ~16 MHz to accommodate the crapy G-BW of the new diodes.

There is some strange ~100-150 kHz noise in our AOM-passed REFL light which is preventing us from locking the other direction. I think it is back-action from the Tilt Sensor Boson. I am on poster duty but Alastair is hard at work on this.

  667   Fri Mar 12 09:18:44 2010 AlastairLaserGYROA tale of two PDs

Quote:

Sitting by the fireside alone in his study, scratching his head between puffs of fine Turkish tobacco drawn from his handcrafted rich mahogany pipe, Alastair realized that one of our PDs didn't even have an amp in it. We now have two PDA10CSs for the REFL PDs and the cavity is locking in one direction again, though we had to reduce the modulation frequency to ~16 MHz to accommodate the crapy G-BW of the new diodes.

There is some strange ~100-150 kHz noise in our AOM-passed REFL light which is preventing us from locking the other direction. I think it is back-action from the Tilt Sensor Boson. I am on poster duty but Alastair is hard at work on this.

I believe they were actually fine Cuban cigars, but I'll let that one slide.

Frank gave us a hand yesterday to track down the noise.  It turns out to be our Isomet oscillator.  Rana has asked me to recreate the measurement, so I'll get that done and post it up here.  We replaced the Isomet with the Tektronix and the noise is now gone.

Rana came past and spent some time aligning things (the EOM is showing some RF-AM, rather than purely phase modulation (this is a bad thing), but we weren't able to improve this significantly) and messing with the locking scheme.  The second PDH box is also displaying the same DC offset that scales with gain.  Once we swap the current PDH with the one Rana modified before, he'll take a look at this one too.  There was some discussion about making up a switch to turn the LF feedback on and off so that we can leave the DAQ running and switch it in and out from the bench without causing the DAQ to rail.

  606   Thu Feb 18 00:45:53 2010 DmassLaserDoublingAA Noise, and slow channels added...

I started chasing my PD noise, and I found extra noise after the input to the AA box, on two channels, one of which I was using in my Mach Zehnder setup.

  • Channels 26 and 30 show extra noise by more than a factor of 3 below 1 Hz.
  • I will be using channels 23, 24, 28, and 29 for recording my data now.

I also added some slow channels to the DAQ.

  • I downsampled my data to 256 via the DAQ (I believe it uses these filters)
  •  
  • The elliptic filters used for downsampling have some high frequency flatenning
  • If I don't do a digital lowpassing of my signal, all my high frequency noise will be aliased into my measurement band many (256) times, which causes it to increase by a factor of 10, despite being filtered.
  • I added an 8th order Butterworth low pass filter at 256 Hz (sample rate, not Nyquist) via Foton to kill these aliased contributions without touching the downsampling filter shape too much.
  • I added the gain conversion to Volts, so my 256 Hz channels are now in V!

 These are name as follows in the DAQ:

Table Name Channel 4 kHz Name (Defunct for now) 256 Hz Name
Alpha (Green PD 1) 23 C2:ATF-MZ_DC1_IN C2:ATF-MZ_ALPHA256
Beta (Green PD 2) 24 C2:ATF-MZ_DC2_IN C2:ATF-MZ_BETA256
Gamme (IR PD 3) 28 C2:ATF-MZ_AC2_IN C2:ATF-MZ_GAMMA256
Delta (IR PD 4) 29 C2:ATF-MZ_AC3_IN C2:ATF-MZ_DELTA256

 

  607   Thu Feb 18 04:29:02 2010 DmassLaserDoublingAA Noise, and slow channels added...

Some Plots:

  1. The noise in the various channels (in counts) with 50 ohm terminators at the input to the AA box.
  2. The Spectra (in V) for each PD with alternate arms blocked, and measured AA noise plotted (lower curve).
  3. The coherence between same color PDs for the two different arms being blocked - Things look as expected based on the power levels.

More to come.

 I made analog measurements of the PD dark noise, and for the most part it seems below the noise downstream of the AA box.

BAFFLING BEHAVIOR SEE PLOT TITLED MZWTF:

When I block one arm, I have decent coherence above 1 Hz. When I block the other, the same is true. When I unblock both arms, and let the Mach Zehnder interfere, my Coherence takes a dive at 1-2 Hz. I DO NOT HAVE ANY IDEA HOW THIS IS POSSIBLE.

THE INDIVIDUAL TIME SERIES LOOK LIKE I EXPECT, AND THE MACH ZEHNDER IS STILL ALIGNED ENOUGH TO INTERFERE.

Attachment 1: AntiAliasNoiseALL.pdf
AntiAliasNoiseALL.pdf
Attachment 2: ArmBlockSpectra.pdf
ArmBlockSpectra.pdf
Attachment 3: ArmBlockedCoh.pdf
ArmBlockedCoh.pdf
Attachment 4: WTFMZ.pdf
WTFMZ.pdf
  648   Mon Mar 8 02:19:45 2010 DmassElectronicsDoublingAC Coupling...

I've added some AC coupling in the form of SR560s. Each 560 is at a gain of 100, in low noise mode, with the AC couple selection (which is a 0.03 Hz pole high pass), and a 300 Hz low pass.

As you can see from my Alpha/Beta plot, I gained loads by AC coupling. This is not true for my Gamma/Delta plot. I think I am loading my ISS PDs with the AA box! I need a buffer of some sort for the DC coupled channel.

When I plug in my AC and DC coup-led channel, there is a direct path from the ISS box to the AA box. The coherence of my AC coupled channel goes up to expected values when I UNPLUG my DC coupled channel. This will be simple to fix, though figuring it out this evening was not so fun.

Shown below is the coherence of both AC and DC channels when I have both plugged in.

 

Update: I tried to T a buffer off the ISS box, but my coherence dived. I will resume tomorrow. Below is what I used as a buffer: this is an LT1012. If I disconnect the buffer, my coherence goes up on the AC channel (a lot).

                  _______short_______

       |     |   \       |

       |-----| -    \ ___|_________output_________to DAQ

         |---| +    /

         |   |  /

                      |

ISS BOX--|--------------------SR560--------to DAQ

                  

                           

Attachment 1: ACCouple560.pdf
ACCouple560.pdf
  652   Mon Mar 8 21:25:22 2010 DmassElectronicsDoublingAC Coupling...

I solved this ridiculous problem after some headache. I am blaming unknown pickup in the 3m breadboard for making my buffer not work, and it is worth no more time. Now, the list:

  • I soldered together a buffer in a protoboard, and am using OP27's to buffer the output of the ISS box.
  • I T-ed this into the SR560s, and adjusted the signals so all four PDs had the same level.
  • I gained by AC coupling! (0.99 Coherence means a factor of 10 intensity cancellation, 0.999 means 30, etc) - See Plot
  • I recombined the signals by putting a 0.03 Hz low pass on the DC input, and adding it to the AC input - See Plot
  • Onwards!

I am done with the AC coupling (for now), and am moving on to calibrating and making the phase noise measurement.

Plot 1 compares the signal levels, and the two PD coherence for AC vs DC channels.

Plot 2 shows the transfer functions between my DC coupled channels and my AC+DC channel (ideally flat in magnitude, relative phase is somewhat unimportant).

Plot 2 also shows how much coherence I have gained by using the AC coupling. Note that below 0.9 coherence means less than a factor of 10 cancellation.

I do not know why my Green AC coupled  channel has such better noise, but then again I don't really know what the ISS box is putting out in terms of noise

 

Attachment 1: ACCoup560.pdf
ACCoup560.pdf
Attachment 2: ACCoupRecom.pdf
ACCoupRecom.pdf
Attachment 3: ACCoupl.png
ACCoupl.png
  655   Tue Mar 9 03:59:51 2010 DmassElectronicsDoublingAC Coupling...

Here are my DC  coupled PD Spectra in Volts. Shot noise is at around the 10^-7 V/rtHz level, so not shown here. DAQ Noise is around 6 uV (and goes up at low frequency, consistent with my dark noise).

And for my AC coupled channels (below the DC plots, same labels), You can see the dark noise seems to drop to the shot noise level, which seems like a good place to stop trying to suppress the noise. I may update these later with a black line at the shot noise.

Attachment 1: PD1Spec.pdf
PD1Spec.pdf
Attachment 2: PD2Spec.pdf
PD2Spec.pdf
Attachment 3: PD3Spec.pdf
PD3Spec.pdf
Attachment 4: PD4Spec.pdf
PD4Spec.pdf
Attachment 5: PD1SpecAC.pdf
PD1SpecAC.pdf
Attachment 6: PD2SpecAC.pdf
PD2SpecAC.pdf
Attachment 7: PD3SpecAC.pdf
PD3SpecAC.pdf
Attachment 8: PD4SpecAC.pdf
PD4SpecAC.pdf
  113   Fri Apr 17 20:04:17 2009 dmassComputingDAQADC no longer working!

I was trying to get the ATF.mdl or OMS.mdl system back up and running, but neither could see fb0.

I telneted in with

>telnet fb0 8087

daqd> shutdown

to reboot fb0. It didn't fix the problem.

I also rebooted oms.

 

I discovered in the course of this that the oms.mdl file was overwritten with Alastair's model. I (saved and) replaced it with an old copy of the oms.mdl file from ws1, and did

make oms

make install-oms

make install-daq-oms

make install-screens-oms

startoms

but was no longer able to get a connection to fb0.

 

I then reinstalled Alastair's model, since it was the last thing I saw communicate with the fb succesfully. I am unsure what I am forgetting, possibly some command I need to run on oms after rebooting it. I was unable to get Alastair's model back up and talking to the framebuilder and I have thus left the DAQ slightly more broken than I found it.

Quote:

The output from the DAQ is now working, and the timing etc looks sensible, though still at 64khz.  I've only tested the four outputs I've setup in my model, but they all work when I use the output matrix to patch the signal to them.

 

 

  117   Mon Apr 20 18:03:44 2009 dmassComputingDAQADC no longer working!

This all started when I did a cvs update. I have forwarded my concerns, trials, and tribulations to the russian.

 

Quote:

I was trying to get the ATF.mdl or OMS.mdl system back up and running, but neither could see fb0.

I telneted in with

>telnet fb0 8087

daqd> shutdown

to reboot fb0. It didn't fix the problem.

I also rebooted oms.

 

I discovered in the course of this that the oms.mdl file was overwritten with Alastair's model. I (saved and) replaced it with an old copy of the oms.mdl file from ws1, and did

make oms

make install-oms

make install-daq-oms

make install-screens-oms

startoms

but was no longer able to get a connection to fb0.

 

I then reinstalled Alastair's model, since it was the last thing I saw communicate with the fb succesfully. I am unsure what I am forgetting, possibly some command I need to run on oms after rebooting it. I was unable to get Alastair's model back up and talking to the framebuilder and I have thus left the DAQ slightly more broken than I found it.

Quote:

The output from the DAQ is now working, and the timing etc looks sensible, though still at 64khz.  I've only tested the four outputs I've setup in my model, but they all work when I use the output matrix to patch the signal to them.

 

 

 

  1505   Wed Aug 10 01:27:16 2011 ZoeElectronicsGYROADC noise and temperature data

So I was doing something really stupid when I made the plot of rotation noise from temperature fluctuations: when I plotted the ADC noise I was subtracting the common mode signal. No wonder the ADC noise seemed so high, exactly as high as the noise in the temperature sensors!! When I correct the error it's clear that our data is well above the ADC noise, and WAS even before I increased the gain on the temperature sensor amplifiers. Here are the corrected plots showing rotation noise calculated from the temperature data taken on the nights of August 8, when we were getting 10 V/K, and August 1, when we were getting 1 V/K. Sorry it took me so long to notice the mistake!!

EDIT: corrected August 8 plot to show that ADC noise converted to rotation rate is lower when we have more V/K. And added plots of just temperature changes without converting to rotation signal.

 

Attachment 1: RotationNoiseAugust1.png
RotationNoiseAugust1.png
Attachment 2: RotationNoiseAugust8.png
RotationNoiseAugust8.png
Attachment 3: TemperatureChangesAugust8.png
TemperatureChangesAugust8.png
Attachment 4: TemperatureChangesAugust1.png
TemperatureChangesAugust1.png
  1502   Tue Aug 9 16:01:50 2011 AlastairElectronicsGYROADC noise floor for temp sensing

Just to verify the estimate for the ADC noise floor, here is a the noise measured on three separate channels with 50ohm terminators on the input.  The calibration was just multiplying by 6.103e-4 V/count  and then dividing by 10 (assuming we have 10V/K) to get to K.

This does agree with Zoe's previous graphs.  EDIT:  Actually that's not true.  I just realised that she had already converted into rotational sensitivity, so the ADC noise is lower.

Attachment 1: temp_sens.pdf
temp_sens.pdf
  2567   Tue May 11 19:23:51 2021 RadhikaDailyProgress2um PhotodiodesADC noise level spectrum

It is important to characterize the noise levels of all instruments used in the current PD testing setup. We generally expect ~5uV/rHz of ADC input noise. Verifying/correcting this value will be key to ensuring that our overall gain is enough to amplify various signals above the ADC noise floor.

I terminated the input to ADC channel 31 with a 50-ohm BNC terminator. I used diaggui to generate the resulting amplitude spectra, with 0.03 BW (attached). To convert counts to volts, I took a range of 20V divided by 2^16 counts, resulting in a scaling of 3e-4 V/count. I plan to conduct another test to confirm this value (feeding a known voltage and comparing to the output). In the meanwhile, the resulting noise level consistent with our expectation of a few uV/rHz.

Attachment 1: adcnoise_210511.xml.gz
Attachment 2: adcnoise.png
adcnoise.png
  1920   Sat May 9 13:30:58 2015 Stephanie, KateMiscSeismometerANSYS Videos and Building Update

I put together part of the rhomboid (the hanging pendulum) and added the top strut to the cage (Fig 1).

     

Figure 1. The rhomboid (without top board) and cage.

I've also atttached the ANSYS modal frequency simulation videos of the rhomboid with the top of the wires constrained in space (turn on repeat to play video continuously). The frequencies are as follows:

Mode 1: 38.44 mHz

Mode 2: 1.51 Hz

Mode 3: 10.15 Hz

Mode 4: 11.62 Hz

Mode 5: 12.69 Hz

Mode 6: 12.69 Hz

 

I've also attached the eDrawing file of the rhomboid.

Attachment 3: Rhomboid_Modes_Videos.zip
Attachment 4: Rhomboid.EASM
  1921   Mon May 11 18:38:14 2015 ranaMiscSeismometerANSYS Videos and Building Update

I would expect that there should be 2 more modes in here, with frequencies between 0.1 and 4 Hz. The lowest mode is the pitch mode and the 1.5 Hz one is the pendulum. There ought to be a transverse pendulum and also a yaw mode.

Maybe try again with more eigenfrequency resolution in the 0.1 - 5 Hz region ?

  195   Thu Jul 23 13:14:03 2009 Aidan, ConnorLaserFiberAOM Aligned, beam matched into fiber, pick off from beam splitter correct size

 

Connor and I have been assembling the FS experiment. The following diagram shows the layout of everything that is aligned at the moment.

We've got the AOM installed and have it aligned to give -1 order when driven at 80MHz (attached image shows main 0th order and -1 order to the right. Not sure what spot up the top is).

Attachment 1: FS_layout_2009_07_23.png
FS_layout_2009_07_23.png
Attachment 2: photo.jpg
photo.jpg
  903   Wed Aug 4 18:52:18 2010 JennaLaserGYROAOM Feedback Signal

Here's a plot of the AOM feedback signal. The SR560 is DC coupled with a gain of 10, and the calibration for the data is

6.1e-4 V/count / 10 x 700 kHz/V * lambda*S/4A * 2pi (rad/s)/Hz = 3.618e-4

6.1e-4 is the calibration from the DAQ, 10 is the gain from the SR560, 700kHz/V is the deviation set on the Techtronix function generator, S is the perimeter of the cavity, and A is the area. One side of the cavity is .7889m.

Attachment 1: AOM8-4.pdf
AOM8-4.pdf
  904   Wed Aug 4 20:26:30 2010 ranaLaserGYROAOM Feedback Signal

That's great! Only a factor of 1 million to go!!

The Tektronix generator is a horrible, horrible, monster and it should not be used as a VCO if at all possible. What's the loop gain for the CW and CCW loops? We need measurements. Also need to see the error point spectra of these loops out to high frequency. By looking at the error spectrum before and after a small increase in gain, one can infer the UGF.

Also, the 40m has one spare PDA255 which can be used to measure the beat frequency in transmission. Its in a plastic tub next to the RF stuff. Luckily Zach is working on a resonant RFPD and we can have something real very soon.

 

  906   Wed Aug 4 20:34:48 2010 AlastairLaserGYROAOM Feedback Signal

Quote:

That's great! Only a factor of 1 million to go!!

The Tektronix generator is a horrible, horrible, monster and it should not be used as a VCO if at all possible. What's the loop gain for the CW and CCW loops? We need measurements. Also need to see the error point spectra of these loops out to high frequency. By looking at the error spectrum before and after a small increase in gain, one can infer the UGF.

Also, the 40m has one spare PDA255 which can be used to measure the beat frequency in transmission. Its in a plastic tub next to the RF stuff. Luckily Zach is working on a resonant RFPD and we can have something real very soon.

 

 A million seems like a nice round number to start from.

We found one photodiode over here that we can use for the transmission readout.  I was putting it in.... then the stuff in that other elog post happened.

  1859   Thu Mar 27 23:18:54 2014 ZachLaserGYROAOM ISS

Today I redid the gyro ISS so that it uses an AOM as the actuator, as opposed the laser current via the controller as usual. Here are the reasons:

  1. As noted yesterday, the laser current couples reasonably strongly to the laser frequency. This is bad in itself, as it causes the frequency feedback to work much harder to maintain gyro lock when the ISS is on.
  2. Due to the above effect, the laser frequency slews when the ISS is engaged. Without slow feedback, the PZT range is not enough to hold the gyro lock during ISS turn-on. As also noted yesterday, it appears that we cannot beat the gyro and CTN lasers and still maintain slow feedback capability. So, this is a more pressing reason to move to a less-frequency-coupled intensity actuator.

I found a G&H 80 MHz AOM in the cabinet, so I grabbed it and started setting things up. To avoid jitter, the only good place to put it is before the PMC. When I put it between the lenses, it added a considerable path length shift (and misalignment), so I had to completely redo the PMC alignment. It's not great right now, and I might have to measure the beam and recalculate the MMT, but fine for testing.

ISS_layout.jpg

I aligned the AOM by hand and got a decent 1st order beam (the only mount that will fit in that place is a PBS platform with a spring arm, so there is no fine alignment to speak of). I drove it with the Tektronix FG and with max output (24 dBm) I could get ~5% diffraction. I then did some first locking attempts, but found that this range was not sufficient to lock the power at DC, surprisingly. This might be because the alignment is not great. In any case, I found a ZHL-1-2W with a heat sink attached, so I used it to increase the range to 0-30 dBm, which gave me around 0-15% diffraction. This was plenty, so I took some measurements:

ISS_v2_3_27_14.png

As usual, I used the leakage through the PMC end mirror for both PMC locking and as the ISS in-loop PD. To test the performance, I put a temporary PD in rejection of the PBS immediately after the PMC.

The above results show good out-of-loop suppression below the UGF of ~150 Hz, but the noise is sitting on something other than the in- or out-of-loop PD dark noise levels below ~2 Hz. Also interestingly, there is good coherence between both detectors in this low-frequency region. I don't claim to know what's going on there. I could imagine there is some excess noise in one of the PDs due to some resistor current noise or something, but I don't think that explains the coherence. Increasing or reducing the gain had no effect on the out-of-loop level, and I tried with and without the I/O enclosure lid on to see if it was some sort of differential environmental noise (but again, the coherence...).

Any ideas?

Anyway, this seems good to go for gyro testing.

  1726   Thu Aug 9 23:45:54 2012 ZachLaserGYROAOM actuation transfer function, etc.

EDIT: I tried using LISO's root mode to fit for the VCO pole from the actuator TF and OLTF below, but it seems to be too close to the cavity pole to get a reliable fit of both. I'm going to just put a zero somewhere near there and see how things look. 

We have discussed switching to using the AOM for the primary loop, since it ought not to have resonances as low as the NPRO PZT. I wanted to measure the frequency actuation transfer function of the VCO+AOM, to see if this is indeed the case.

Unlike the laser PZT, for which length changes correspond directly to frequency changes, the AOM crystal's resonances should only produce AM effects. This means that it is enough to ensure that the VCO frequency actuation has a flat transfer function. I began taking RF spectra of the VCO output, to fit the FM sideband peaks and find the modulation depth per unit input as a function of frequency (a kind of transfer function), when I realized there was a much easier and more direct way to do this: lock the primary loop, and use the quiet secondary direction around the cavity as a frequency reference. This way, I could just sweep the VCO within the linear range of the error signal and measure the Vctrl -> fmod just as it is in the real thing.

Setup

First, I locked the primary loop with the uPDH as I have done recently. Then, I powered the AOM, manually set the center frequency so that the secondary beam was resonant (fc ~ 50 MHz), and swept the VCO frequency across the resonance to measure the error signal. This is the result after aligning the REFL PD and optimizing the LO angle:

TEK00000.PNG TEK00003.PNG

As you can see on the right, the linear range extends to roughly 20 mVpp sweep drive.

Transfer function

  • I hooked the Agilent audio analyzer source to the VCO control input, referred it to channel 1 and monitored CW_ERR on channel 2.
    • Source: 10 mVpp
    • Span: 50 Hz - 50 kHz
    • 101 pts
    • Integration time: 234 cycles (max)
  • After this, I did the same with the RF analyzer to go to higher frequency. I used a BNC splitter that someone marked "0.1 - 500 MHz", so I guess there is a small frequency window between both measurements that could be suspect
    • Source: 10 mV (-27 dBm)
    • Span: 10 - 1 MHz
    • 201 pts
    • 16 avgs
    • -10 dB in signal path, compensated in data analysis

AOM_ACT_TF_8_9_12.png

Notes:

  • The TF looks nice and clean up to ~400 kHz, which is good. 
  • The measurements from both analyzers match up nicely at the low end of the RF trace , but then deviate somewhat. I wonder if this has to do with the splitter I used. 
  • The response is flat up to a few kHz, where it rolls off to 1/f2. This includes in it one pole from the cavity, so there is a pole in the actuator somewhere in the same range.

I wish I could trust the data above 50 kHz better. I might try this again with an SR785 to get to 100 kHz anyway. In any case, it looks like it should be straightforward to shape a servo properly and use this actuator to push the UGF up to >100 kHz, which will do wonders for the primary loop, since the OLG where the dominant noise is (10-1000 Hz) can be increasing steeply this far below the UGF.

 

OLTF

Using the secondary beam is a perfect testbed for the primary loop, since I hope to use the same actuator and I can suppress the noise with the existing primary loop while testing. I locked the secondary loop with the PDH2 (easily) and measured this nice OLTF.

double_lock.png CW_OLTF_PDH2_8_9_12.png

I was actually able to get the UGF ~2x higher, but lowered it so that I could use a higher source and get a cleaner measurement. It is clear that the UGF can't be pushed higher because the loop goes to 1/f2 above ~6 kHz. The rollup below a few 100 Hz is from the PDH2 board, which also compensates the cavity pole, and so the VCO pole can be determined from this OLTF. I am figuring that out, after which we can put a zero in the TF there and get clean 1/f up to >100 kHz.

This is good!

  624   Mon Mar 1 19:41:25 2010 ZachLaserGYROAOM double-pass

 We were able to resolve the AOM double-pass issue by enlarging the beam going into it. We had originally tried using the smallest practical waist (~ 70 um) because the jitter suppression scheme only works perfectly--i.e. beam ROC = mirror ROC with the mirror exactly R away from the AOM--in the limit where zR --> 0, or w0 = 0. It appears that this caused the beam to diverge too quickly within the AOM, which is pretty long. We have changed the waist size to ~200 um at the expense of moving the mirror in to z = 15.5 cm from the AOM (as opposed to z = R = 30 cm as it was before). We are now able to isolate a decent-looking double-pass beam, which we verified by measuring its power. Hopefully the loss in jitter suppression will be insignificant as we only expect the AOM to shift by hundreds of Hz or so, corresponding to a very small angular displacement.

After this progress this morning, I tried to realign the cavity and get the original unmodulated direction to lock, but I am having quite some difficulty. I can align it and isolate the 00 mode pretty well, and there appears to be a decent amount of power emerging at the transmitted end on resonance (as seen on IR card), but the thing just doesn't want to lock. I have tried to adjust the RF phase to no avail. I suspect it has something to do with a polarization issue with the BS I am using to screen some power from the REFL beam before the PD, but I can't figure it out. I will try again tomorrow morning.

Once this direction locks again, we can feed in the modulated beam around the other direction, and we should have all the necessary equipment to set up the second loop. I spoke with Frank today, and I believe we will need a Marconi to set up a PLL at the output to do the frequency readout. We will figure this out when it comes up, I guess.

  1688   Tue Jun 12 00:44:32 2012 ZachLaserGYROAOM double-pass reoptimized, CW beam profiled

I am now confident that the primary loop is working properly with the PDH2 servo (with the exception of boost 4), so I am continuing with setting up the bidirectional lock.

I realigned and optimized the AOM double-pass setup, and recovered ~40% double-pass efficiency, which, although not great, is the best I was able to do before.

After that, I profiled the CW beam for mode matching. As with the CCW path, I have a pre-MMT lens in place so that there is a suitable focus for the faraday isolator to straddle close enough to the cavity. This is the profile after that lens.

CW_profile_6_11_12.png

The relatively large astigmatism is introduced by the AOM setup, but should still allow for decent cavity coupling. I forgot to measure the distance to the cavity, so I will compute the MMT solution tomorrow morning.

The second uPDH box (#1437) is now free, so I can immediately lock with it once the MMT and isolation/REFL setup is done.

  1648   Wed Mar 14 02:21:17 2012 ZachLaserGYROAOM double-pass set up, etc.

I realized that the beam I was using through the AOM was too small, and that's why the efficiency was suffering. There is always this compromise between jitter suppression (from the geometrical matching of the beam ROC to that of the retroreflector, which requires as small a beam as possible), and the interaction volume in the AOM crystal. I have used a beam of w ~ 135 um.

With this, I attained a double-pass efficiency of ~40% (single pass ~63%). This is close enough to the previous levels.

I profiled the beam emerging from the double-pass setup for use with designing the MMT to the gyro cavity. The AOM setup seems to really squeeze the beam into an astigmatic state, which is something we have noticed before. This is what makes it difficult to couple the CW beam efficiently to the cavity without cylindrical lenses.

CW_profile_3_13_12.png

For the CCW beam, I will just use the post-PMC/EOM profile I measured yesterday, since it goes through no other focusing elements.

The two beams are now ready to go through their respective MMTs and into the cavity. With any luck, I will get it locked up tomorrow.

 

AOM_redone_over_and_over_and_over.png

  365   Wed Oct 7 00:51:35 2009 AidanLaserFiberAOM installed and running on far side of fiber

I've installed an AOM on the far side of the fibre to shift the frequency of the transmitted beam by 70MHz. We're driving it with a +2dBm signal which is being amplified by ~33dB by a ZHL-1-2W amplifier from MiniCircuits. We're getting around 12% of the total optical power in the first order beam. It is also extremely elliptical.

In the image below: the output of the fiber coupler the beam is directed into an AOM where the first order beam is around 12% of the input. The first order beam passes through an iris which block the zeroth order beam. It goes through an f = 150mm lens to produce a waist which can be used with a flat for a retro-reflection. Unfortunately, when the beam is viewed after this lens with the beam scan, it is obvious that it is extremely elliptical. The retro-reflector, a flat partial reflector (R = 85% at normal incidence), is placed near the waist of the horizontal, which is about 305 um. The waist in the vertical appears to be at the lens and around 700-750um radius.

The beam, originally p-polarized, goes through a QWP which converts it to circular, it is "retro-reflected" and  goes back through the QWP to become s-polarized. It works it way back to the AOM where there is another zeroth order transmission and a first order transmission. The zeroth order is the faint beam that is dumped on the fiber coupler. The first order transmission is co-linear with the original beam and couples back in to the fiber.

Back at the input end of the fiber the double passed beam is extracted using a polarizing beam splitter. Rana and I optimized the transmission with the retro-reflector in it's current position but it's quite weak (we haven't yet determined how much power makes it back).

Attachment 1: 00001.jpg
00001.jpg
  366   Wed Oct 7 01:14:26 2009 AidanLaserFiberAOM installed and running on far side of fiber

Quote:

I've installed an AOM on the far side of the fibre to shift the frequency of the transmitted beam by 70MHz. We're driving it with a +2dBm signal which is being amplified by ~33dB by a ZHL-1-2W amplifier from MiniCircuits. We're getting around 12% of the total optical power in the first order beam. It is also extremely elliptical.

In the image below: the output of the fiber coupler the beam is directed into an AOM where the first order beam is around 12% of the input. The first order beam passes through an iris which block the zeroth order beam. It goes through an f = 150mm lens to produce a waist which can be used with a flat for a retro-reflection. Unfortunately, when the beam is viewed after this lens with the beam scan, it is obvious that it is extremely elliptical. The retro-reflector, a flat partial reflector (R = 85% at normal incidence), is placed near the waist of the horizontal, which is about 305 um. The waist in the vertical appears to be at the lens and around 700-750um radius.

The beam, originally p-polarized, goes through a QWP which converts it to circular, it is "retro-reflected" and  goes back through the QWP to become s-polarized. It works it way back to the AOM where there is another zeroth order transmission and a first order transmission. The zeroth order is the faint beam that is dumped on the fiber coupler. The first order transmission is co-linear with the original beam and couples back in to the fiber.

Back at the input end of the fiber the double passed beam is extracted using a polarizing beam splitter. Rana and I optimized the transmission with the retro-reflector in it's current position but it's quite weak (we haven't yet determined how much power makes it back).

 The double passed beam is extracted using a PBS and is incident on a photo-detector, as shown in this diagram. There is a, relatively, large amount of scatter (about 20-30% of PD signal) which appears to be coming from the AOM. Right now we're not doing anything about it, because it is a different frequency and polarization to the double-passed light, but we should look into clearing it up in the near future.

(I haven't shown the zeroth order beam from the AOM in this picture).

Attachment 1: PBS.jpg
PBS.jpg
  1307   Wed Feb 16 00:18:27 2011 ZachLaserGYROAOM set up, CCW and CW beams power-balanced @ ~80 mW

 This evening, I set up the AOM double-pass and balanced the two beams going to the injection/extraction optics. This wasn't as simple as last time because I had to re-profile the beam and come up with a modematching solution. I've updated my recent "status" post to reflect the current status.

Here is the profile after the mirror leading into the AOM:

aom_path_profile.png

The beam was slightly elliptical and somewhat astigmatic (|z0x - z0y| ~ 10 cm). Using the average of x and y, I came up with a simple matching solution using an f = 100mm lens and the R = 30cm mirror we were using before. It puts the mirror roughly 30cm from the AOM, and the waist of about 124um near the center of the crystal. Here is the ABCD screenshot:

AOM_mm_ABCD.png

I was able to isolate the double-passed 1st-order beam with an overall efficiency of ~45% (i.e. single-pass efficiency of ~67%). This is slightly worse than before, but the output beams are very close together so it is difficult to know whether we actually had it better before at all. In any case, I balanced the beams heading toward the injection optics at about 80 mW apiece, which is more than what we were counting on already. There is still some power dumped just after the laser, so there is still room to step up the power a bit more should we need it. Here's a picture of the setup as it stands---I am holding an IR card to show where the two beams are going:

gyro_as_of_2_15_11.png

 

 

  352   Mon Sep 28 16:53:07 2009 ZachMiscGeneralAOMs

 There are three AOMs in the cabinet downstairs, two of which are not labeled beyond their model numbers. I tracked down some information on them and am posting them here so that we have it in the future.

First, the one that was labeled with a center frequency:

  • Crystal Technologies
    • Model No.: 3200-1113
      • f_center = 200 MHz

Now, the party crashers:

  • IntraAction Corp.
    • Model No.: AFD-402
      • Flint glass (F7)
      • Deflector
      • f_center = 40 MHz
      • Aperture: 2 mm
      • Serial No.: 1002
    • Model No.: AOM703M
      • Flint glass (FF8)
      • Frequency modulator
      • f_center = 70 MHz
      • Aperture: 3 mm
      • Serial No.: 6805

I have attached pictures of the latter two for reference (the first one is still packaged, labeled, and located in its own marked compartment).

Attachment 1: AFD-402.png
AFD-402.png
Attachment 2: AOM703M.png
AOM703M.png
  353   Mon Sep 28 17:17:08 2009 KojiMiscGeneralAOMs

Hm. L_gyro = 3e8/(2*70e6) ~ 2m in a round trip. The 70MHz sounds nice for gyro. Do we have dedicated AOM drivers for them?

Quote:

 There are three AOMs in the cabinet downstairs, two of which are not labeled beyond their model numbers. I tracked down some information on them and am posting them here so that we have it in the future.

First, the one that was labeled with a center frequency:

  • Crystal Technologies
    • Model No.: 3200-1113
      • f_center = 200 MHz

Now, the party crashers:

  • IntraAction Corp.
    • Model No.: AFD-402
      • Flint glass (F7)
      • Deflector
      • f_center = 40 MHz
      • Aperture: 2 mm
      • Serial No.: 1002
    • Model No.: AOM703M
      • Flint glass (FF8)
      • Frequency modulator
      • f_center = 70 MHz
      • Aperture: 3 mm
      • Serial No.: 6805

I have attached pictures of the latter two for reference (the first one is still packaged, labeled, and located in its own marked compartment).

 

  355   Mon Sep 28 17:56:42 2009 ZachMiscGeneralAOMs

Not as far as I know, but I can try to find something. We just received a new driver from NEOS but it is for 80 MHz and is only rated for 75-85.

Quote:

Hm. L_gyro = 3e8/(2*70e6) ~ 2m in a round trip. The 70MHz sounds nice for gyro. Do we have dedicated AOM drivers for them?

Quote:

 There are three AOMs in the cabinet downstairs, two of which are not labeled beyond their model numbers. I tracked down some information on them and am posting them here so that we have it in the future.

First, the one that was labeled with a center frequency:

  • Crystal Technologies
    • Model No.: 3200-1113
      • f_center = 200 MHz

Now, the party crashers:

  • IntraAction Corp.
    • Model No.: AFD-402
      • Flint glass (F7)
      • Deflector
      • f_center = 40 MHz
      • Aperture: 2 mm
      • Serial No.: 1002
    • Model No.: AOM703M
      • Flint glass (FF8)
      • Frequency modulator
      • f_center = 70 MHz
      • Aperture: 3 mm
      • Serial No.: 6805

I have attached pictures of the latter two for reference (the first one is still packaged, labeled, and located in its own marked compartment).

 

 

  2098   Tue May 2 15:31:24 2017 AidanComputingCymacsATF Cymacs FB4 built - only OS and RTSCDS package right now

I've installed Debian 8 on the new ATF Cymacs and called the machine FB4.

Following the instructions on the ATF Wiki, I've installed the ADVLIGORTS-CYMAC package. However, I've not built the framebuilder, RTS or DAQD.

 

  1108   Wed Oct 20 18:43:48 2010 AlastairComputingComputingATF FB0 front-end rebuild

 I've started work on updating the model for our front-end code.  First I want to just rebuild as it is using the existing model.  I'm going to put up idiot-proof instructions on the wiki as I go along.

So far I've tried the method given on the 40m wiki here: http://lhocds.ligo-wa.caltech.edu:8000/40m/Simulink_to_Front-End_code  .  I can get pretty far through these instructions before hitting problems at the point where you copy the .ini file across - at this point I find that the file is not in the location given in the instructions.

The simpler instructions on page 17 of T080135-00-C do work however.  I can get all the way through to the point where i do the startatf command and using ps I can see there are processes with the atf name running.  If I open an MEDM screen there is no data coming in though.  Also the daqd process wasn't running, so I did a sudo reboot on FB0.  When I did this FB0 hung while rebooting.  I power-cycled it and it booted up the next time.  When I ssh into it daqd is now running.  I did startatf again.  When I open MEDM the channels still don't seem to be acquiring.

I wonder whether there is a problem that it is not loading epics BURT data because in the /cvs/cds/caltech/target/c2atf/log.txt the final line, repeated over and over again is "Waiting for EPICS BURT 0"

When I try opening the GDS_TP medm screen it comes up with the error "cannot open file /cvs/cds/caltech/scripts/utilities/nova_logo.gif".  When I check, the utilities folder does not exist.  I tried to see where in the MEDM screen this .gif is supposed to live, but in the end I opted for putting random small gif file in nova_logo.gif in the meantime.  Now the MEDM screen runs without complaining but the boxes are white.

 

ELOG V3.1.3-