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ID Date Author Type Category Subjectup
  11984   Tue Feb 9 19:15:36 2016 gautamUpdateGreen LockingLaser swap - updates

Some updates on the laser swap situation:

  1. Mode-matching calculation: 
  • I should have caught this earlier, but it was an oversight - the 35um waist that Andres used in his calculation is the waist size of the green beam. So I've been off by a factor of sqrt(2) all this while, and it works out that the desired waist size is indeed 50um, consistent with Kiwamu's elogs. Furthermore, as he has detailed in that elog, we actually want the free-space waist of the input beam to the doubling crystal to be ~6.7mm from the geometric center of the PPKPT crystal. 
  • I redid the calculation using these updated numbers. Attachment #1 shows the results (optimized for the X-waist, Y-profile plotted for comparison and to see what mode-matching efficiency we get). The way I've set up the code is for a la mode to rank the solutions in order of increasing sensitivity to the positions of the lenses. It turns out the least sensitive solution doesn't actually achieve the desired waist size of 50um - moreover, it requires us to change both lenses currently in the path. The next lease sensitive solution, however, achieves the desired waist (i.e. 100% theoretical mode-matching efficiency for the X mode) and only requires us to swap the 125mm lens we put in yesterday for a 150mm lens (and the positions of the lenses change slightly compared to what we had yesterday as well). The sensitivity in a la mode is parametrized by the amount of power remaining in the TEM00 mode while displacing one or more components. It turns out that this figure of merit is only ~1% smaller for the 2nd least sensitive solution compared to the first. So I've chosen to use that solution. Code used to calculate the mode matching is Attachment #2.
  • I've also plotted in Attachment #1 what the beam profile would have looked like before our modificatons last night, using the numbers from Zach's elog - as I have already mentioned in the previous elog, it suggests that the waist size would have been 39um, at a location 1.0821m in my coordinate system (desired position according to considerations in the previous 2 bullets is 1.0713). This seems to have been a sub-optimal configuration, but is also subject to errors I made in measuring the positions of the mirrors/lenses (I don't think I had 1cm resolution).

       2. Implementing the new solution:

  • I've switched out the 125mm efl lens for a 150mm efl lens from the same Thorlabs lens kit. I've also moved both the lenses to their new appropriate positions.
  • Unfortunately, I had put in some irides in the beampath before calculating this new (more appropriate solution). As a result, both the lenses are off from their optimal positions by a few mm because the irides get in the way. I guess we just have to live with this for now, and can adjust the positions of the lenses once we actually get some green light and are happy with all the other alignments...
  • As noted in the previous elog, I suspect that we saw no green light yesterday because we were missing the doubling crystal altogether (given that we have only a 1mm x 1mm area to aim for - the Faraday serves as a coarse constraint, though its aperture has ~25times this area!). I tried playing around with the two steering mirrors immediately after the NPRO to see if I could get some green light out, but have not been successful yet. I may make some further trials later in the evening/tomorrow...

As I check the manual of the Innolight (pg17) and the datasheet of the Lightwave, I wonder if the Quarter Wave Plate that was placed immediately after the Innolight laser head is even necessary now - I assume the purpose of the combination of QWP+HWP was to turn the elliptically polarized light from the Innolight into linearly polarized light before the Faraday. But the Lightwave already produces linearly polarized light. I will check out what is the configuration on the Y-end table...


Attachment 1: Modematch_X.pdf
Attachment 2: XendModeMatch.m.zip
  11985   Wed Feb 10 17:57:15 2016 gautamUpdateGreen LockingLaser swap - updates

After the discussion at the meeting, I decided to go ahead and open the top of the oven so that I could get a visual on where the crystal was located - this helped in the alignment, and I was able to get some green light out of the oven. I had to tweak the position of the Doubling oven a little (with the top open) in order to align the crystal to the beam axis. However - I was only able to get ~140uW of green light going into the Faraday. I had measured the power at various points along the beam path recently with the old setup. We used to have ~860uW of green going into the Faraday there. To see if I could improve the situation a little, I checked that the beam was reasonably centered on both apertures of the IR Faraday, and then removed the irides upstream of the doubling oven. These were preventing me from placing the lenses exactly as per the a la mode solution. Once the irides were removed, I moved the lenses to their optimal positions as best as I could with a tape measure to mark out distances. I then further tweaked the position of the doubling oven using the 4 axis stage, monitoring the green power while doing so. The best I could get was ~200uW. Perhaps the positions of the lenses need to be optimized further. I also checked the IR power before and after the IR Faraday - these numbers are ~260mW and ~230mW respectively (I maximized the transmitted power through the Faraday by rotating the HWP, the QWP that was in the beam path has now been removed as the Lightwave outputs linearly polarized light), and compare favourably to the numbers in the old setup. Doing a naive scaling accounting for the fact that we have less power going into the doubling crystal, I would expect ~700uW of green light coming out, so it looks like the mode matching into the doubling crystal is indeed sub-optimal. However, now that things are roughly aligned, I hope the optimization will go faster...

  12002   Mon Feb 22 13:56:52 2016 gautamUpdateGreen LockingLaser swap -reflected beam from ETM aligned

I tried aligning the green beam, elliptical as it is, to the arm by using the various steering mirrors after the doubling oven. The following was done:

  1. Eric and I aligned the beam through the green Faraday - we levelled the beam using an iris to check the beam height immediately after the Faraday and a little further along the beam propagation direction.
  2. We checked that the beam is reasonably centered on all the lenses. We changed the lens holder for one of the lenses from a Thorlabs model to a Newport model, so as to get the lens to the correct height such that the green beam was roughly centered on it. 
  3. I then tweaked the alignment of the steering mirrors until the reflected beam from the ETM roughly coincided with the input beam. The return beam is getting clipped slightly on the way back through the green Faraday, so some more alignment needs to be done. However, given the ITMX situation, I can't align the arm to IR, so I'm holding off on further alignment for now...
  11982   Tue Feb 9 04:37:10 2016 ericqUpdateGreen LockingLaser swap initiated

[ericq, Gautam]

Tonight we embarked on the laser swap. In short, we have gotten ~210mW through the faraday doubler, but no green light is apparent. The laser outputs ~300mW, so it's not exactly a work of art, but I still expected some green. More work remains to be done...

Gautam took numerous photos of the table before anything was touched. One lens was swapped, as per Gautam's plan. The innolight laser and controller are on the work bench by the end table. The lightwave is on the table and on standby, and is not hooked up to the interlock mounted on the table frame, but instead one below the table directly next to the controller. The ETMX oplev laser is turned off. 

  11983   Tue Feb 9 11:49:47 2016 gautamUpdateGreen LockingLaser swap initiated

Steve pointed me to an old elog by Zach where he had measured the waist of the 1W Innolight NPRO. I ran a la mode with these parameters (and the original optics in their original positions prior to last night's activities), and the result is in reasonably good agreement (see Attachment #1) with my initial target waist of 35 um at the center of the doubling oven (which I presume coincides with the center of the doubling crystal). The small discrepancy could be due to errors in position measurement (which I did by eye with a tape measure) or because I did not consider the Faraday in the a la mode calculation. However, I wonder why this value of 35 um was chosen? In this elog, Kiwamu has determined the optimal waist size to be 50um at the center of the doubling crystal. Nevertheless, as per his calculations, the doubling efficiency should be non-zero (about 1% lower than the optimum conversion efficiency) at 35um or 70um, so we should be able to see some green light as long as we are in this fairly large range. So perhaps the fact that we aren't seeing any green light is down to sub-optimal alignment? I don't think there is a threshold power for SHG as such, its just that with lower input power we expect less green light - in any case, 200mW should be producing some green light... From what I could gather from a bunch of old elogs by Aidan, the Raicol PPKPT crystals have dimension 1mm x 1mm x 30mm (long axis along beam propagation), so there isn't a whole lot of room for error perpendicular to the direction of propagation... I wonder if it is possible, for the initial alignment, to have the top cover of the doubling oven open so that we can be sure we are hitting the crystal?

Attachment 1: Innolight_beamProfile.pdf
  6429   Tue Mar 20 09:59:01 2012 steveUpdateIOOLaser tripped off

Today is janitor day. It still does not explain why the 2W Innolight tripped off about an hour ago. All back to normal.

.......................................................I asked Keven later, he admitted hitting the emergency shut off next to the chemical storage cabinet.

  10508   Tue Sep 16 10:47:52 2014 SteveUpdatePSLLaser turned on

 Our janitor turned off the laser accidentally. 

  10509   Tue Sep 16 14:26:45 2014 ericqUpdatePSLLaser turned on


 Our janitor turned off the laser accidentally. 

 The PMC wasn't locking very happily after this. I tweaked the pointing onto the PMC REFL diode, to make sure it was centered, and touched the alignment into the PMC. I also reset the FSS Slow output to zero. It took a little while for the laser to settle in, for some reason, but the transmission is up at 0.80 now. 

Tweaked MC2 pointing to get the MC transmission high enough to let WFS kick in, which nicely got the rest of the MC alignment done. After that, I offloaded the WFS into the MC suspensions. 

Lastly, I ran the command that Rana posted in ELOG 10391, to set the FSS input offset (From -0.18 to -0.06)

  10510   Tue Sep 16 16:03:36 2014 KojiUpdatePSLLaser turned on


 Our janitor turned off the laser accidentally. 

 Didn't you take this opportunity to replace the cooling fan of the innolight controller?

  8023   Thu Feb 7 14:10:25 2013 ManasaUpdateOpticsLaserOptik - AR Reflectivity - Bad data

Reflectivity of AR surface of LaserOptik (SN6)


The first step measurements of R for AR surface. I am not convinced with the data....because the power meter is a lame detector for this measurement.

I'm repeating the measurements again with PDs. But below is the log R plot for AR surface.

R percentage

6000ppm @ 42 deg
3560ppm @ 44 deg
7880ppm @ 46 deg
4690ppm @ 48 deg



  6907   Tue Jul 3 17:56:35 2012 JamieUpdateGreen LockingLaseroptik dichroic optics received

We have received the dichroic optics from Laseroptik.  The coatings are:


  • 532nm: T(s+p) > 97%
  • 1064nm:  R(p) > 99.9%


  • 532nm: R(s+p) < 1%
  • 1064nm: R(p) < 2%

We got two sets with these coatings:

  • 6x: 50 x 9.5mm, 2 degree wedge
  • 8x: 25 x 6.35mm, 2 degree wedge
  • 1x: 25 x 3mm, witness
  6909   Tue Jul 3 19:04:59 2012 JamieUpdateGreen LockingLaseroptik dichroic optics received

I put them in the "visible optics" drawer of the newish, metal optics cabinet with the thin drawers down the Y arm.

  7930   Wed Jan 23 18:16:11 2013 ManasaUpdateGeneralLaseroptik mirror - SN6

 I repeated the transmittance measurements of LaserOptik SN6 @1064nm.

Transmittance for s-polarization 

0 deg - 0.524
45 deg - 0.055

Transmittance for p-polarization

0 deg - 0.515
45 deg - 0.1047 0.01047

Raji's measurements are here.

Attachment 1: sn6_trans.png
  7932   Wed Jan 23 20:24:05 2013 KojiUpdateGeneralLaseroptik mirror - SN6

Got confused (even after I talked with Manasa).

The plot shows the number ~0.01 or less at 45deg. But the number is the text does not match with the plot.

Please use the logarithmic scale for the vertical axis.
And more points between 35 to 50 deg please (like ~1deg spacing)

Don't we have the data sheet from the coater? Can we request it?

  7935   Wed Jan 23 22:02:25 2013 ManasaUpdateGeneralLaseroptik mirror - SN6


Got confused (even after I talked with Manasa).

The plot shows the number ~0.01 or less at 45deg. But the number is the text does not match with the plot.

Please use the logarithmic scale for the vertical axis.
And more points between 35 to 50 deg please (like ~1deg spacing)

Don't we have the data sheet from the coater? Can we request it?

I corrected the typo in the text...however, I agree the plot was lame...Will get the data sheet made tomorrow! 

  7940   Thu Jan 24 15:16:50 2013 ManasaUpdateGeneralLaseroptik mirror - SN6

I repeated the transmittance measurements of Laseroptik SN6 at 1064nm. The rotation stage could only resolve 2 deg rotation (We should consider buying a better rotation stage).


Percentage transmittance

       0.177% 42 deg
       0.806% 44 deg
       0.57%   46 deg
       54.8%    0 deg


Percentage transmittance

       1.039% 42deg
       1.155% 44 deg
       1.159% 46 deg
        65.6%   0 deg


  7941   Thu Jan 24 16:23:24 2013 KojiUpdateGeneralLaseroptik mirror - SN6

The mirror T is completely out of spec. We should find or request the data sheet of the mirror.

> We should consider buying a better rotation stage

I'm already on it

  7943   Thu Jan 24 16:34:56 2013 ranaUpdateGeneralLaseroptik mirror - SN6

  I have two questions:

1) Are we sure that the T measurement is not being compromised by some systematic? i.e. some leakage is making the apparent T appear too high.

2) IF the T is really so high, how should we decide whether or not to use this one rather than the G&H? Is the 532 nm property more important than the high recycling gain?

  7944   Fri Jan 25 08:10:42 2013 SteveUpdateGeneralLaseroptik mirrors

 Here are the German plots. Unfortunately they are not logarithmic.

 Ed: Proprietary data removed. Use wiki (Koji)

Steve uploaded data to the 40m wiki  / Aux_Optics on 02-07-2013



  14400   Tue Jan 15 15:27:36 2019 gautamUpdateGeneralLasers and other stuff turned back on

VEA is now a laser hazard area as usual, several 1064nm lasers in the lab have been turned back on. Apart from this

  • the IFR was reset to the nominal modulation settings of +13dBm output at 11.066209 MHz (this has to be done manually following each power failure).
  • The temeprature control unit for the EY doubling oven PID control was turned back on.
  • The EY Oplev HeNe was turned back on.
  • EY green PZT HV Kepco was turned back on.
  7192   Wed Aug 15 13:23:34 2012 LizSummaryComputer Scripts / ProgramsLast Weekly Update

Over the past week I have been continuing to finalize the daily summary pages, attempting to keep the total run time under half an hour so that they can be run frequently.  I have had many hang ups with the spectrograms and am currently using second trends (with this method, the entire script takes 15 minutes to run).  I also have a backup method that takes 3 minutes of data for every 12 minutes, but could not implement any interpolation correctly.  This might be a future focus, or the summary pages could be configured to run in parallel and full data for the spectrograms can be used.  I configured Steve's tab to include one page of images and one page of plots and fixed the scripts so that it corrects for daylight savings time (at the beginning of the running, the program prints 'DST' or 'Not DST').

Right now, I am focusing on making coherence plots in a spectrogram style (similar to the matlab 'coh_carpet' function) and a spectrogram depicting Gaussianity (similar to the plots made by the RayleighMonitor).  I have also been working on my  final paper and presentation.

  11584   Wed Sep 9 11:00:49 2015 IgnacioUpdateIOOLast Wiener MCL subtractions

On Thursday night (sorry for the late elog) I decided to give the MCL FF one more try. 

I first remeasured the actuator transfer function because previous measurements had poor coherence ~0.5 - 0.7  at 3 Hz. I did a sine swept to measure the TF. 

Raw transfer function:

The data is attached here: TF.zip

Then I made Wiener filters by fitting the transfer function data with coherence > 0.95 (on the left). Fitting all the data (on the right). Here are the filters:


The offline subtractions (high coh fit on left, all data fit on right). Notice the better IIR performance when all the TF data was fitted.


The online results: (these were aquired by taking five DTT measurements with 15 averages each and then taking the mean of these measurements)


And the subtraction performance:


Attachment 3: TF.zip
  11592   Sun Sep 13 13:26:00 2015 ranaUpdateIOOLast Wiener MCL subtractions

When making the Wiener filter OFF/ON comparisons, we want to use the median PSD estimates, not the mean (which is what pwelch gives you).

cf. Sujan's note and Evan's follow-up

The median will be less sensitive to the transients / gltiches and will show more improvement I think.

  11713   Mon Oct 26 18:10:38 2015 IgnacioUpdateIOOLast Wiener MCL subtractions

As per Eric's request, here is the code and TF measurement that was used to calculate the MC2 FF filter that is loaded in FM5. This filter module has the filter with the best subtraction performance that was achieved for MCL.


Attachment 1: code_TF.zip
  3620   Wed Sep 29 12:08:28 2010 josephb, alexSummaryCDSLast burt save of old controls

This is being recorded for posterity so we know where to look for the old controls settings.

The last good burt restore that was saved before turning off scipe25 aka c1dcuepics was on September 29, 11:07.

  7399   Mon Sep 17 20:23:31 2012 JenneUpdateGeneralLast of In-vac mirror photos taken

[Manasa, Jenne]

We took the last of the in-vac photos of mirrors today.  I'll post in the morning.

Tomorrow, I'll align the DRMI once more to check, and get IPPOS and IPANG out of the vacuum.  I'll  take a look at POX, POY and POP, but we may just have to cross our fingers and hope for the best on those ones.  They were pretty hard to get out of the vac during their initial alignment, since they're so weak.

Also, tomorrow morning Steve is going to try out our new light access connector!!!!  I'm so excited!

The goal is to put heavy doors on, on Wed, and start pumping Wed afternoon / Thurs evening.

  7400   Mon Sep 17 23:58:01 2012 ranaUpdateGeneralLast of In-vac mirror photos taken

 My hope is that the DRMI flashes will be bright enough to see on the PO beams. IF we get 10 mW through the Faraday, you should get some buildup when the carrier resonates in the DRMI.

If the recycling gain is 10 and the pickoff fraction is 100 ppm you ought to get ~10 uW on PO. How much of the recycling cavity power gets out of POP?

  7401   Tue Sep 18 11:53:12 2012 JenneUpdateGeneralLast of In-vac mirror photos taken


[Manasa, Jenne]

We took the last of the in-vac photos of mirrors today.  I'll post in the morning.

Tomorrow, I'll align the DRMI once more to check, and get IPPOS and IPANG out of the vacuum.  I'll  take a look at POX, POY and POP, but we may just have to cross our fingers and hope for the best on those ones.  They were pretty hard to get out of the vac during their initial alignment, since they're so weak.

Also, tomorrow morning Steve is going to try out our new light access connector!!!!  I'm so excited!

The goal is to put heavy doors on, on Wed, and start pumping Wed afternoon / Thurs evening.

 The photos on the OMC table are particularly tricky, since the camera plus the 'bathroom' mirror add a lot of weight....even if the MC locked, the input beam would be completely different, so all of the beams would be wrong.

During some of the work on the BS table, ITMY was realigned to have its beam retro-reflect, since the weight of the camera plus mirror was shifting all of the suspended optics on the BS table.  ITMY was restored after that, for subsequent photos.

Attachment 1: AllPhotos_Sept2012.pdf
AllPhotos_Sept2012.pdf AllPhotos_Sept2012.pdf AllPhotos_Sept2012.pdf AllPhotos_Sept2012.pdf AllPhotos_Sept2012.pdf AllPhotos_Sept2012.pdf AllPhotos_Sept2012.pdf AllPhotos_Sept2012.pdf
  7406   Wed Sep 19 01:15:15 2012 JenneUpdateGeneralLast of In-vac mirror photos taken - NOT!

I'm making a separate entry to go along with this thread of photos...

Putting the camera and 'bathroom' mirror on any table pretty significantly changes the leveling of any table.  The mirror especially is very heavy, although the camera is not feather light.  We need to come up with a new plan for taking alignment-confirming photos without adding anything to the tables.  That, or we have to level the table between each camera shot.  Anyone who has ever leveled one of our in-vac tables should shudder in horror at idea #2, so we need to put some thought into idea #1 before our next vent.  Vent Czar - can you put this on the list, in addition to the REFL rearrangement stuff?

As a result of this, PZT2 needed to be reverted to the place it was before work began on Saturday (so that the beam goes through the 45 degree target without any extra stuff on the table).  This means, unfortunately, that all of the photos / still captures of optics after PZT2 are invalid.

  14893   Tue Sep 17 23:46:21 2019 KojiUpdateCDSLatch Enable Logic

[Koji Gautam]

We continued to check the latch logic. Today we found that latch.py didn't catch the change of LSB but did for MSB. We determined that this happens when the slider value is chaged between the polling for LSB and MSB.
SInce these two should always be related to a single gain value, latch.py was modified so.

Now we don't observe any logic error for ~100 gain transisitions (see attached).

Attachment 1: Screenshot_from_2019-09-17_23-39-35.png
  3235   Fri Jul 16 13:05:48 2010 Kyung-haUpdateSUSLate update for 7/13 Tue (Tip Tilts)

[Jenne & Kyung-ha]

We suspended the mirror to one of the main frame with the ECD backplane we finished before. The hard task was to find the right balance for the mirror so that 1) it won't be tilted and 2) it'll be in the right position for the ECD backplanes so that the magnets attached to the mirror holder would be in the very center of each ECD holes. We used optical lever laser (red He/Ne) to check the balance of the mirror. We tried to use the jig for the mirror holder clamps but because of the size difference, we couldn't use it at all. (Since the magnets are very heavy, we thought the wire being not perfectly centered might work better. However, the jig dimension was way too different that the wire ended up in the middle of one of the holes.) Since there was no other clever way to attach the wire in the right position, we just tried to be as center/accurate as possible. After attaching wire to that mirror holder clamps, we hanged it to the frame. Again, we couldn't find any other accurate way to find the center so we held the wire and tried to adjust the mirror height as accurate as possible so that it can be in the right position in respect to ECD backplane and not be tilted at the same time. However, when we hanged the mirror, it was still tilted.. So we adjusted the mirror tilt using the mirror holder clamps. Since the holes on the clamps were ellipse shapes, we could adjust the position of the clamps a little bit. When we adjust the clamps, we started to tighten the screws when the mirror is NOT in the perfect position since the tightening up part changes the mirror angle anyways. Luckily, when we tightened up the last screw, the mirror was in the perfect position! After that, we poked the mirror several times to make sure that it comes back to the same place.

Amazingly, we could finish this whole hanging/adjusting process in about 30 mins! :D (Jan said it's because of his amazing moral support. :P Maybe he'll be there to support us everytime we work on the mirrors?)

  4893   Tue Jun 28 02:11:47 2011 JenneUpdateLockingLatest MICH noise budget

I have measured / calculated the latest MICH noise budget.  It doesn't really look all that stellar.


As you can see, we are nowhere near being shot noise limited, since there's a huge discrepancy between all of the measured spectra and the teal Shot Noise line. 

One possible suspect is that the analog whitening filters weren't on when I took my measurements.  I didn't actually check to ensure that they were on, so they might not have been.  Right now we're limited by electronics and other boring noises, so I need to make sure we're limited by the noise of the diode itself (we don't have enough light in the IFO to actually be shot noise limited since that takes 2.5mA for AS55 and I only have 1.1mA, but we should be ~within a factor of 2ish).

  5035   Tue Jul 26 03:15:52 2011 JenneUpdateLockingLatest MICH noise budget

[Jenne, Rana]

We had another look at the MICH noise budget tonight. Rana has verified that my techniques / math aren't too ridiculous. 

In the first attachment, you'll notice that the MICH noise is waay above the shot noise of 1mW on the beam splitter.  We don't know why.  One problem is that the modulation depth of the 55MHz is too low by ~a factor of 10.  Kiwamu and his magical resonant circuit are working on fixing this.  This will not, however, fix the huge discrepancy here.  More investigation and meditation is required!  For this measurement, the whitening gain of AS55 was set to 42dB for both I and Q.

In the 2nd attachment, the PSL shutter is closed, so all of these are dark measurements of AS55.  (The input matrix on the LSC screen is AS55Q * 1 -> MICH_IN1, so they're the same).  All we've done is change the whitening gain before the ADC.  For 0dB and 9dB, you can see that the low freq noise didn't change - here we're still limited by the ADC noise.  With 21dB and 42dB we're clear of the ADC, so either is fine.  Unfortunately, the high freq stuff when the loop is on matches up with the high freq part of the dark noise, so that's part of the problem....

Attachment 1: MICHnoise_shotNoise_25July2011.pdf
Attachment 2: MICH_darkNoise_whiteningGainChanging_25July2011.pdf
  10014   Mon Jun 9 20:07:53 2014 nicolasHowToComputer Scripts / ProgramsLatex (math) in the elog

\text{\LaTeX} in the elog

One feature that has been sorely missing in the elog has been the ability to easily add mathematical symbols. Here is an imperfect solution.

There is a browser plugin available for firefox, safari and chrome that allow you to add “markdown” formatting to any rich text input box in the browser. One feature of markdown is latex math formulae.


The way it works is you type some latex formatted math text in between dollar signs, click the button in your browser, and it converts them to rendered images.

So this


becomes this


Some drawbacks:

The images are actually rendered through a google service, so if that service changes or goes down, the images won’t render, however the HTML source still contains the source string.
The size of formulae are not really matched to the text.
Going back and forth between rendered and unrendered can lose changes (if you make changes after rendering).

Bonus features:

It also works in Gmail!
You can do code highlighting:

#!/bin/bash   ### this is a comment  PATH=$PATH:/home/user/path    echo "How cool is this?" 

EDIT: it looks like the code highlighting is sort of broken :-(.

  3027   Tue Jun 1 18:39:59 2010 NancyUpdate Lead spheres for the seismographs


the lead spheres that were placed below the granite slab have been flattened by hammering to have lesser degree of wobbling of the slab.

the height of each piece, and the flatness of their surfaces was checked by placing another slab over them and checking by the spirit level.





  16717   Wed Mar 9 10:23:28 2022 JordanUpdateVACLeak Testing of New Manual Gate Valve - Attempt #1

Jordan, Chub, Paco

Chub and I went into the lab this morning to leak check the new gate valve after pumping over the weekend. This would be done through the RGA and spraying helium around the newly installed flanges. The RGA is set to monitor the partial pressure of helium versus time and we visually watch for any spikes in pressure to indicate an air leak.

So, I mistakenly thought the gate valve was opened and both sides were being pumped on, this was not the case. The vavle was closed so there was a pressure differential whenI turned the handle it tripped the interlocks and closed V4. I closed VM3 to the RGA volume to prevent the filament from being damaged.

Then the medm screen for the vac controls started flashing rapidly, I closed the window and reopened the controls to find all the panels were white, but we could still see the read only vac screen. So Paco restarted c1vac and the controls were restored. V7 closed, but was then reopened.

We now need to restart pumping with the odd pressure differentials between V4 and VM3.


- TP2 turned off along with the AUX pump

- VM3 opened to vent RGA volume (RGA turned off, filament cooled)

- Open the manual vent screw on TP1 to bring the RGA+TP1 volume back to atmosphere, now no pressure diff. on V4

- Open V4, restart AUX pump to rough out the volume

- Connect RP1/3 line to the pump scroll, turn on RP1/3 RGA+TP1 volume went to mtorr

- Slowly open the manual gate valve

- Connect AUX pump to TP2 and rough out

- Restart TP2, once at speed open V4, close V6 and turn off RP1/3

Now we are pumping on the RGA/TP1 volume with TP2, leak check attempt #2 will happen tomorrow morning

  16721   Thu Mar 10 09:39:59 2022 JordanUpdateVACLeak Testing of New Manual Gate Valve - Attempt #2

This morning Chub and I leak checked the manual gate valve with the RGA and helium. There was no change in the helium partial pressure while spraying helium around the flanges, all looks good.


I also took a 100 AMU analog scan, after the filament had warmed up overnight and the plot was quite noisy even with the lowest scan speed. I recommend this unit go back to SRS for a filament replacement/recalibration. I am worried yesterday's "vent" of the RGA volume may have burned the filament. See the comparison of yesterday's analog scan to today's below.

Attachment 1: 3-09-2022.PNG
Attachment 2: 3-10-2022.PNG
  14673   Thu Jun 13 22:46:41 2019 KojiUpdateIOOLeft IMC at the intermediate gains

SURFS want some locking of IMC for camera adjustment.

So I left the IMC with intermediate gains so that it keeps locking and unlocking.

VCO (overall) iMC gain of -32, FSS common gain 3, and the FAST gain 20. I believe MC2tickle is ON too.

  1799   Mon Jul 27 19:55:19 2009 KojiHowToIOOLens selection: plano-convex? or bi-convex?

Q. When should we use plano-convex lenses, and when should we use bi-convex?

As I had the same question from Jenne and Dmass in a month,
I just like to introduce a good summary about it.
Lens selection guide (Newport)

At a first order, they have the same function.
Abberation (= non-ideal behavior of the lens) is the matter.

  13000   Mon May 22 10:15:14 2017 jigyasaSummarytelescope designLens tubes and object distances

Since the f numbers of the lenses in the proposed design with biconvex lenses are a little less than 5 and the conjugate ratio(that is the ratio of object to image distance) is greater than 5, I explored the use of plano convex lenses, but with the same focal lengths, the accessible u-v range is restricted with the planoconvex rather than biconvex lenses.
On Friday, I had a discussion with Gautam and Steve about the hardware that is the cylindrical enclosures for the camera and the telescope and we examined two such aluminum cylindrical enclosures. One of them was the one being currently employed for the cameras. The dimensions were measured and the length was found to be 8’’ and an outer diameter of 26 cm within an error of 0.5 cm.
The other enclosure was longer with a length of 52 cm(±0.5 cm), outer diameter of 10”(±0.1”) and an inner diameter of 23.7cm(±0.1cm). Pictures of these enclosures are attached.
Both of these enclosures have internal optical rail to mount the camera and the telescope system. Depending on the weight of the telescope system(that includes the weight of the slotted lens tubes, the lenses), it might be more efficient to clamp the telescope system itself on the rails with the low weight camera mounted on the lens tube.
I also went around to get an idea of distance of the GigE from the test masses. This was just a step to verify if the object distances were really in the ranges being taken into consideration, that is between 1500 and 2500 mm. I also tried to cross check the measurements with the CAD drawing of the 40m. However, as I have been informed, the distances in the CAD version are not updated.

The distances from the optic to the CCD detector would range from around 75.1 cm for MC2, 94.01 cm for ITMX, 97.21 cm for ETMX, 117.19 cm for ITMY and 88.463 cm for ETMY. The illuminator for the ETMY was disconnected, so Gautam helped me access the manual lamp control to enable me to take measurements.
The values for ETMX, MC2 and ITMY are subject to an error of ±1’’. Due to a lot of obstructions, the values for ETMY and ITMX may be subject to a lot more error. Even so, these distances are clearly less than 2 meters, prompting me to run the simulations again and verify that the chosen combination is still useful.

As for the slotted lens tubes to mount the 2” lenses, the following options are available on the Thorlabs catalog. CVI and Edmunds do not seem to offer much of the stackable lens tubes.

SM2L30C is a lens tube onto which the optic can be mounted without the need of a spanner wrench. It also has a length of 3”. However, it has a rotatable slip shield which can be rotated open as and when the access to optic is required. However, there might be a slight compromise with rigidity here.

SM2L30 is a lens tube with internal thread depth of 3”, the optic can be mounted using spanner wrench and a retainer ring. The optic cannot be accessed from both ends of the tube here.
SM2M30 is a lens tube with no external threads, therefore lens tube couplers would be required to stack the tubes. The optic is accessible from both ends here though.

Considering the merits and demerits of all these available options, the use of SM2L30 might be considered as it provides a quick and efficient way of stacking multiple lens tubes. As for accessing the optic from both sides, using multiple tubes helps overcome the problem and still ensures that we are able to access a number of separation distances as per requirement.
Thorlabs also offers an internal C to external SM2 adapter so that the lens tube could be fixed onto the C mount of the camera. 

I would be examining the use of 1" diameter lenses for the eyepiece as suggested by Rana, as that might give us more flexibility. 

Attachment 1: Pictures1.pdf
Pictures1.pdf Pictures1.pdf Pictures1.pdf Pictures1.pdf
  1069   Wed Oct 22 17:48:58 2008 YoichiUpdateGeneralLenses for focusing the optical lever laser (Re:divergence of He Ne 1035P)
Steve had difficulty in finding lenses for focusing the HeNe laser for the ITM op-lev.
Following his measurement of the beam divergence, I did some calculation to find a suitable set of lenses and positions.

First, I fitted Steve's data to get the waist size and location of the new HeNe.
The first plot shows the fitting result.
The size of the waist is 0.3mm at -367mm from the laser output (i.e. inside the laser).
(I only used horizontal beam size data.)

Then using the obtained beam parameter, I calculated the propagation of the beam through two lenses.
After playing with the focal length and location of the lenses, I found that with parameters {f1=-0.125m, f2=0.2m, d1=0.2m, d2=0.1m} we get about 1mm beam at the QPD (about 4m away from the laser). f1 and f2 are the focal lengths of the lenses, d1 is the distance from the laser to the first lens and d2 is the distance between the two lenses.
The second plot shows the beam size as a function of the distance from the laser.

The Mathematica notebook used to plot the beam propagation is attached.
By running it on Mathematica 6, you can dynamically change the parameters (focal lengths and locations) by sliders, and the plot (like the one shown in the second attachment) updates in real time. It is cool. Please try it.

The ITM oplevs laser diodes are noisy.
They will be replaced by JDS 1035P
SN T8093307 was measured with the beamscanner.
This will able us to calculate the right lenses to get a small beam on the qpd.

The first column is distance from the front face of the laser in cm.
The second column is beam diameter in the horizontal direction in microns.
The third column is the beam diameter in the vertical direction in microns.
(edit by Rana)
Attachment 1: BeamProfile.png
Attachment 2: BeamPropagation.png
Attachment 3: BeamPropagation.zip
  12922   Fri Mar 31 16:10:33 2017 SteveUpdateTreasureLes Guthman

Les Guthman interviews  gradstudent Graig.

Main laser emergency shut off was acuated by accident during this fiming. The laser is turned on.

  4446   Mon Mar 28 15:49:18 2011 josephbUpdateCDSLessons from LST



Koji was unable to build his c1lst model first thing this morning.  Turns out there was  a bug with RCG parser that was introduced on Friday when we did the RCG updates.  We talked Alex who did a quick comment fix.  The diff is as follows:

Index: Parser3.pm

--- Parser3.pm  (revision 2328)
+++ Parser3.pm  (working copy)
@@ -1124,8 +1124,8 @@
  print "Flattening the model\n";
  print "Finished flattening the model\n";
-  CDS::Tree::do_on_nodes($root, \&remove_tags, 0, $root);
-  print "Removed Tags\n";
+  #CDS::Tree::do_on_nodes($root, \&remove_tags, 0, $root);
+  #print "Removed Tags\n";
  #print "TREE\n";
  CDS::Tree::do_on_nodes($root, \&remove_busses, 0, $root);

This was some code to remove TAGs from the .mdl file for some reason which I do not understand at this time.  I will ask tommorrow in person so I can understand the full story.


Koji then rebuilt and started the c1lst process.  This is his new test version of the LSC code.  We descovered (again) that when you activate too many DAQ channels (simply uncommenting them, not even recording them with activate=1 in the .ini file) that the frame builder crashes.  In addition, the c1lsc machine, which the code was running on, also hard crashed.

When a channel gets added to the .ini file (or uncommented) it is sent to the framebuilder, irregardless of whether its recorded or not by the frame builder.  There is only about 2 megabytes per second bandwidth per computer.  In this case we were trying to do something like 200 channels * 16384 Hz * 4 bytes = 13 megabytes per second.

The maximium number of 16384 channels is roughly 30, with little to no room for anything else.  In addition, test points use the same allocated memory structure, so that if you use up all the capacity with channels, you won't be able to use testpoints to that computer (or thats what Alex has led me to believe).

The daqd process then core dumped and was causing all sorts of martian network slowdowns.  At the same time, the c1lsc computer crashed hard, and all of the front end processes except for the IOP on c1sus crashed.

We rebooted c1lsc, and restarted the c1sus processes using the startc1SYS scripts.  However, the c1susfe.ko apparently got stuck in a wierd state.  We were completely unable to damp the optics and were in general ringing them up severely.  We tried debugging, including several burt restores and single path checks.

Eventually we decided to reboot the c1sus machine after a bit of debugging.  After doing a burt restore after the reboot, everything started to damp and work happily.  My best guess is the kernel module crashed in a bad way and remained in memory when we simply did the restart scripts.


  2870   Mon May 3 01:35:41 2010 KojiUpdateSUSLessons learned from MC spot centering

Lessons learned on the beam spot centering (so far)

Well-known fact:

The spot position on MC2 can be adjusted by the alignment of the mirror while maintaining the best overlapping between the beam and the cavity axes.

In general, there are two methods:

1) Use the cavity as a reference:
Move the MC mirrors such that the cavity eigenmode hits the centers of the mirrors.
-> Then adjust the incident beam to obtain the best overlapping to the cavity.

2) Use the beam as a reference:
Move the incident beam such that the aligned cavity has the spots at the centers of the mirrors.
-> Then adjust the incident beam to obtain the best spot position while the cavity mirrors keep tracking
the incident beam.

Found the method 1) is not practical.

This is because we can move the eigenmode of the cavity only by very tiny amount if we try to keep the cavity locked.
How much we can move by mirror alignment is smaller than the waist radius or the divergence angle.
For the MC, the waist radius is ~2mm, the divergence angle is 0.2mrad. This means the axis
translation of ~1mm is OK, but the axis rotation of ~4mrad is impractical.

Also it turned out that adjustinig steering mirror to the 10-m class cavity is quite difficult.
A single (minimum) touch of the steering mirror knob is 0.1mrad. This already change the beam position ~0.1mm.
This is not an enough resolution.

Method 2) is also not so easy: Steering mirrors have singular matrix

Indeed! (Remember the discussion for the IMMT)

What we need is the pure angle change of 4mrad at the waist which is ~2m distant from the steering mirror.
This means that the spot at the steering mirror must be moved by 8mm (= 4mrad x 2m). This is the result of the
nearly-singular matrix of the steering mirrors.

We try to avoid this problem by moving the in-vac mirror (IM1), which has somewhat independent move.
The refl beam path also has the big beam shift.
But once the vacuum manifold is evacuated we can adjust very little angle.

This can also be a good news: once the angle is set, we hardly can change it at the PSL side.

  3233   Thu Jul 15 23:51:47 2010 Mr. MaricHowToSUSLevitate me if you can

You guys must work harder.


  11365   Fri Jun 19 03:00:56 2015 ericqUpdateCDSLibrary Model Parts examined

All simulink diagrams being used at the 40m are now under version control. I have compiled, installed, and restarted all current models to make sure that the files are all in a working state, which they seem to be. I have checked the latest version of the userapps svn repository to /opt/rtcds/userapps2.9, to compare the files therein with our current state. 

Surprisingly, only two files in the userapps svn have been changed since they were checked out here, and only one of these is a real change of any kind. 

LSC_TRIGGER.mdl was edited at some point simply to align some drawn lines; no functionality was changed. 

SCHMITTTRIGGER.mdl was edited to change the "INVERT" epics channel from an arbitrary EPICS input, to binary (true/false) input. This does not change the connectivity diagram, and in fact, I don't think we use this option in any of our scripts, nor is it exposed on our medm screens. 

Thus, I think that the only place for block changes can bite us is changes in the fundamental blocks in CDS_PARTS that are used in our custom 40m library parts. 

For posterity, these are the files used in compiling all of our running models. (Path base: /opt/rtcds/userapps/release)

  10670   Wed Nov 5 11:37:29 2014 manasaUpdateGeneralLight from Y end reaches PSL table

[Steve, Diego, Manasa]

Since the beatnotes have disappeared, I am taking this as a chance to put the FOL setup together hoping it might help us find them.

Two 70m long fibers now run along the length of the Y arm and reach the PSL table.

The fibers are running through armaflex insulating tubes on the cable racks. The excess length ~6m sits in its spool on the top of the PSL table enclosure.

Both the fibers were tested OK using the fiber fault locator. We had to remove the coupled end of the fiber from the mount and put it back in the process. So there is only 8mW of end laser power at the PSL table after this activity as opposed to ~13mW.  This will be recovered with some alignment tweaking.

After the activity I found that the ETMY wouldn't damp. I traced the problem to the ETMY SUS model not running in c1iscey. Restarting the models in c1iscey solved the problem.


  5313   Sat Aug 27 20:38:17 2011 SureshUpdateIOOLight is back on WFS

[Valera, Suresh]

   We wanted to continue the work with WFS servo loops.  As the current optical paths on the AP table do not send any light to the WFS, I changed a mirror to a 98% window and a window to a mirror to send about 0.25mW of light towards the WFS.   The MC locking is unaffected by this change.   The autolocker works fine.

   When the power to the MC is increased, these will have to be replaced or else the WFS will burn.

  4849   Tue Jun 21 19:54:33 2011 SureshUpdateGreen LockingLightWave NPRO power supply shifted to ETMY end table

The Lightwave NPRO power supply which is being shared between the AS table and the ETMY table has been shifted back to the ETMY table

The current to the laser is set at 1.5A.  The laser output is 200mW at this current level.

  4832   Fri Jun 17 16:05:07 2011 kiwamuUpdateABSLLightWave out of MOPA box

[Suresh / Kiwamu]

 We did the following things :

   - Took the LightWave NPRO out from the MOPA box

   - Temporarily took out the laser controller which has been connected to the Y end laser.

   - Put the LightWave on AP table and plugged the laser controller and confirmed that it still emits a beam



[Things to be done]

   - measure the beam profiles and power

   - get a laser controller, which will be dedicated for this laser, from Peter King


[Background and Motivation]

 The PRC and SRC length have to be precisely measured before the vent.

In order to measure those absolute length we are going to use the Stochino technique, which requires another laser to scan the cavity profiles.

The LightWave NPRO laser in the MOPA box was chosen for the Stochino laser because it has a large PZT range of 5 MHz/V and hence allows us to measure a wider frequency range.

The laser in the MOPA box had been connected to home-made circuits, which are not handy to play with. So we decided to use the laser with the usual laser controller.

Peter King said he has a LightWave laser controller and he can hand it to us.

Until we get the controller from him we do some preparations with temporary use of the Y end laser controller.

ELOG V3.1.3-