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ID Date Author Type Categorydown Subject
  6837   Wed Jun 20 01:02:20 2012 JamieUpdateGreen LockingRF amp removed from X arm ALS setup

I very badly forgot to log about this in the crush of surfs.

I removed Koji's proto-beatbox RF comparator amp from the X arm ALS setup.  I was investigating hacking it onto one of the discriminator channels in the new beatbox, now that Yuta/Koji's Yuta/Koji's phase tracker is making the coarse beatbox path obsolete.  Upon further reflection we decided to just go ahead and stuff the beatbox board for the X arm, and use the proto-beatbox to test some faster ECL comparators.  This will be done first thing in the morning.

In the meantime the old amp is in my cymac mess on the far left of the electronics bench.

  6842   Thu Jun 21 01:58:29 2012 JenneUpdateGreen LockingXgreen preparations

[Yuta, Koji, Jenne]

Lots of small things happened tonight, in preparation for having both arms' ALS working simultaneously.

1. Xarm aligned in IR

     1.1 ETMX oplev centered

2. Xgreen coarsely aligned to Xarm

3. X beat setup on PSL table resurrected. 

     3.1 Steering optics for both X and Y green (before PBS) were touched to fix clipping Xgreen on some of the first mirrors after the light exits the chambers.

     3.2 Xgreen aligned to beat PD

     3.3 PSL green waveplate rotated so ~half of the light goes to X beat, other ~half goes to Y beat (recall we had rotated the polarization so we had max light on the Y beat PD a few weeks ago).

          3.3.1 Now we have ~80uW of PSL green going to each beat PD.

     3.4 PSL green aligned to X beat PD

          3.4.1 Replaced mount for mirror between PBS (which splits PSL green light) and BS (which combines PSL green and X green) so that I could get the alignment correct without having to use the full range of the knobs on the mount.

     3.5 Realigned (coarsely) Ygreen to Y beat PD - the mirrors just after the chambers had been touched, so Y green was no longer directly on the PD.  This will need to be done more finely when we're ready to lock the Yarm again.

     3.6 Dedicated cables for the DC of each beat PD were put in place, so we have those in addition to the DC transmission PDs which we are putting in temporarily each time we align the green to the cavities.  Some mystery unused cables that were running under the PSL table were removed.  The power for the X beat PD was rerouted so that it's much closer to the actual diode, and out of the way. 

4. Better alignment of X green to X arm.

     4.1 Put Green Transmission camera into place

     4.2 Noticed that the X green spot on the transmission camera is not nearly as steady as the Y green.  Increased the gain of the X green refl PD on the end table to see if it helped the spot be more steady, but it's still very wiggly.  We reverted the gain to what it was.  We need to fix this!!!!

    4.3 Removed camera, looked at X transmission DC (PD is temporarily in front of the beat PD), tried to increase the transmission.

     4.4 Aligning the green to the X arm has been really tough - there were a few more iterations of camera then DC PD.

     4.5 Measured X green power on the PSL table - 02 mode was ~150uW.  The 00 mode is still not very stable, which is frustrating, although we have a reasonable amount of power transmitted.   

     4.6 The X end green shutter was moved out of the beam path since the green beam was clipping while going through the shutter.  We need to put it back now that the beam is pretty much aligned.  The beam size and the aperture are roughly the same, so we should look to see if there is a different place on the table where the beam is a little smaller, where we can put the shutter.

5. Whitening filters (Pomona box-style) made for the Xarm I and Q channels - these are the same as the whitening for the Y arm.

6. 30m SMA cable made to be used for 2nd delay line.

     6.1 Steve reminded me this morning that we returned one of the fancy spools of cable that was purchased for the delay lines, since it was defective.  We didn't get it replaced because there was debate as to what is the best kind of cable to use.  We need to come to a conclusion, but for now we have a regular RG-405 cable.

7.  Jamie has started work on modifying the beatbox so that we can have 2-arm ALS.  Hopefully that will be done soon-ish, because we're otherwise pretty close to being ready.

  6850   Thu Jun 21 20:07:18 2012 JamieUpdateGreen LockingImproved beatbox returns

I've reinstalled the beatbox in the 1X2 rack.  This improved version has the X and Y arm channels stuffed, but just one of the DFD channels (fine) each.

I hooked up the beat PD signals for X and Y to the RF inputs, and used the following two delay lines:

  • X: 140' light-colored cable on spool
  • Y: 30m black cable

The following channel --> c1ioo ADC --> c1gcv model connections were made:

  • X I  --> SR560 whitening --> ADC 22 -->  X fine I
  • X Q --> SR560 whitening --> ADC 23 --> X fine Q
  • Y I --> SR560 whitening --> ADC 24 --> Y fine I
  • Y Q --> SR560 whitening --> ADC 25 --> Y fine Q

The connections to the course inputs on the ALS block were grounded.  I then recompiled, reinstalled, and restarted c1gcv.  Functioning fine so far.

 

  6851   Fri Jun 22 02:21:57 2012 JenneUpdateGreen Locking2 arm ALS - Success!!!!

[Yuta, Jenne]

We locked both arms using the ALS system simultaneously!  Hooray!

Video of spectrum analyzer during lock acquisition of both beats is attached.

Jamie is super awesome, since he fixed us up a beatbox speedy-quick.  Thanks Jamie!!  speedy_gonzales-5257.jpg

 Details:

1:  Aligned PSL green optics

     1.1:  We added an amplifier of ~20dB after the X beat PD (more Xgreen power on the PSL table so the signal was ~3dB higher than Y, so required less amplification).  The ~24dB amplifier is still in place after the Y beat PD.  Both beat signals go to a splitter after their amplifiers.  One side of each splitter goes to one of the channels on the beatbox.  The other side of each splitter goes to a 3rd splitter, which we're using backwards to combine the 2 signals so we can see both peaks on the spectrum analyzer at the same time.

2:  Found both beat notes

     2.1:  Y beat was easy since we knew the temps that have been working for the past several days

     2.2:  X beat was more tricky - the last time it was locked was the end of February (elog 6342)

         2.2.1:  We found it by adjusting the PSL laser temp nearly the full range - DC Adjust slider was at 8.8V or so (Y beat was found with the slider at ~1.1V tonight)

          2.2.2:  We then walked the beat around to get the PSL temp back to "normal" by moving the PSL temp, then compensating with the Xend laser temp, keeping the beatnote within the range of the spectrum analyzer.

          2.2.3:  Fine tuned the temps of all 3 lasers until we had 2 peaks on the analyzer at the same time!!

               2.2.3.1:  Yend - measured Temp=34.14 C, thermal Out of Slow servo=29820

               2.2.3.2:  Xend - displayed temp=39.33 C, thermal Out of Slow servo=5070

               2.2.3.3: PSL - displayed temp=31.49 C, Slow actuator Adjust=1.100V

3:  Locked both arms using ALS!!

     3.1:  We were a little concerned that the Xarm wasn't locking.  We tried switching the cables on the beatbox so that we used the old channels for the Xarm, since the old channels had been working for Y.  Eventually we discovered that the input of the filter module for ETMX's POS-ALS input was OFF, so we weren't really sending any signals to ETMX.  We reverted the cabling to how it was this evening when Jamie reinstalled the beatbox.

          3.1.1:  We need to sort out our SUS screens - Not all buttons in medm-land link to the same versions of the SUS screens!  It looks like the ALS screen was modified to point the ETMY button to a custom ETMY SUS screen which has the ALS path in the POS screen, along with LSC and SUSPOS.  There is no such screen (that I have found) for ETMX.  The regular IFO_ALIGN screen points to the generic SUS screens for both ETMY and ETMX, so we didn't know until Yuta searched around for the filter bank that the ALS input for ETMX was off.  We just need to make sure that all of the screens reflect what's going on in the models.

     3.2:  See the video attached - it shows the beat peaks during locking!!! (how do I embed it? right now you have to download it)

          3.2.1:  First you will see both peaks moving around freely

          3.2.2:  Then X arm is locked briefly, then unlocked

          3.2.3: Y arm is locked, steadily increasing gain

          3.2.4:  X arm is locked, so both arms locked simultaneously

          3.2.5:  Yuta clicked a button, accidentally unlocking the Xarm

4:  The transmission of the X arm was not so great, and both of our green beams (although X green especially) were no longer nicely aligned with the cavities.  Yuta tried to align the X arm to the X green, but it's bad enough that we really need to start over with the whole IFO alignment - we leave this until tomorrow.  Since we didn't have any good IR transmission, we didn't bother to try to find and hold the Xarm on IR resonance using ALS, so we didn't measure a POX out of loop residual cavity motion spectrum.  Again, tomorrow. 

Attachment 1: P6210140.AVI
  6852   Fri Jun 22 03:37:42 2012 KojiUpdateGreen Locking2 arm ALS - Success!!!!

Are these correct?

1. It is a nice work.

2. This is not locking, but stabilization of the both arms by ALS.

3. We now have the phase trackers for both arms.

4. There is no coarse (i.e. short) delay line any more.

5. The splitters after the PDs are reducing the RF power to Beat-box.
Actually there are RF monitors on Beat-box for this purpose, but you did not notice them.

6. c1ioo channel list
https://wiki-40m.ligo.caltech.edu/CDS/C1IOO%20channel%20list
has to be updated.

7. Video can be uploaded to Youtube as Mike did at http://nodus.ligo.caltech.edu:8080/40m/6513

  6853   Fri Jun 22 10:52:18 2012 yutaUpdateGreen Locking2 arm ALS - Success!!!!

Answers to questions from Koji.

Are these correct?

1. It is a nice work.

Correct, of course!

2. This is not locking, but stabilization of the both arms by ALS.

Correct.

3. We now have the phase trackers for both arms.

Correct.

4. There is no coarse (i.e. short) delay line any more.

Correct. No coarse, only fine delay line (30m) with the phase tracker.

5. The splitters after the PDs are reducing the RF power to Beat-box.
Actually there are RF monitors on Beat-box for this purpose, but you did not notice them.

Oh, yes. But distance between beatbox and spectrum analyzer in the control room is longer than distance between BBPD on PSL table and the spectrum analyzer. We were too lazy to do cabling, but maybe we should.

6. c1ioo channel list 
https://wiki-40m.ligo.caltech.edu/CDS/C1IOO%20channel%20list
has to be updated.

Yes, we will.

7. Video can be uploaded to Youtube as Mike did at http://nodus.ligo.caltech.edu:8080/40m/6513

We didn't, but we can.

  6858   Fri Jun 22 20:58:15 2012 JenneUpdateGreen LockingCalibrated POX spectra - Xarm stabilized by ALS

[Yuta, Jenne, Koji]

We stabilized the Xarm using the ALS and took a spectrum of POX as our out of loop sensor.  We used the calibration from elog 6841 to go from counts to meters.

We find (see attached pdf) that the RMS is around 60pm, dominated by 1Hz motion.

 

In other, related, news, I took out the beam pipe connecting the AP and PSL tables and covered the holes with foil.  This makes it much easier and faster to get to the X beat setup for alignment.  Eventually we'll have to put it back, but while the AUX laser on the AP table is not being used for beating against the PSL it'll be nice to have it out of the way.

Attachment 1: POX11_I_ERR_calib_residualCavityMotion_better.pdf
POX11_I_ERR_calib_residualCavityMotion_better.pdf
  6859   Sat Jun 23 02:29:18 2012 yutaUpdateGreen LockingX arm mode scan results

X arm finesse is 416 +/- 6, mode-matching ratio is 91.2 +/- 0.3%

I did mode scan for X arm just like we did for Y arm (see elog #6832)

Servo design:
  Servo filters are as same as Y arm.
  UGF and phase margin of X arm ALS are 100 Hz and 14 deg.
  For phase tracking loop, they are 1.5 kHz and 56 deg.

Raw data from the mode scan:
XarmScan20120623.png


Fitted peaks and finesse:

fine8FSRscanXarm.png

By taking the average,

F = 416 +/- 6 (error in 1 sigma)
(For Y arm, it was 421 +/- 6. See elog #6832)


Mode matching ratio:
 From X arm 8FSR measurement using phase tracker, peak heights are

TEM00 0.834, 0.851, 0.854, 0.852, 0.876, 0.850, 0.855, 0.878
TEM01 0.031, 0.031, 0.017, 0.017, 0.009, 0.014, 0.009, 0.011
TEM02 0.053, 0.052, 0.057, 0.058, 0.061, 0.060, 0.061, 0.059
TEM03 0.011, 0.010, 0.010, 0.007, 0.006, 0.005, 0.006, 0.005

 So, the mode-matching ratio is

MMR = 89.7%, 90.1%, 91.0%, 91.2%, 92.0%, 91.4%, 91.8%, 92.1%

 By taking the average,

MMR =  91.2 +/- 0.3 (error in 1 sigma)
(for Y arm, it was 86.7 +/- 0.3 %. See elog #6828)


Discussion:
 - Mode matching ratio for both X and Y arm is ~90%, which is not so great, but OK. It seems like there's no huge clipping or mode-mismatch from MC to ITMs. I think we should go next for PRMI investigation.

 - Measured finesse seems too low compared with the design value 450. If we believe power transmission of ITM and ETM are 0.0138 and 1.37e-5, the measured finesse tells you that there's ~0.1% loss(F = 2*pi/(T_{ITM}+T_{ETM}+T_{loss})). We need some evaluation for the linearity of the sweep, before concluding that there's 0.1% loss for each arm. Using FINE_I/Q signal for calibration, or installing frequency divider for monitoring actual beat frequency would help.


Things to do for the beat setup:

 - Amplifiers after beat PDs shouldn't be on the PSL table. Move them near the beatbox.
 - Install DC PD (and camera?) at un-used port of the beat BS for monitoring green transmission power.
 - Make nice MEDM screens for our new phase tracking ALS.
 - Make a script to sweep arm length with ALS and find IR resonance.
 - Look into X end table. Beam spot of the X green transmission is wiggly when X end table is opened and there's air flow.

  6862   Sun Jun 24 00:10:45 2012 yutaUpdateGreen Lockingcurrent beat electronics

I moved amplifiers for beat PD at PSL table to 1X2 rack. Current beat setup from PD to ADC is shown below. Setup for X beat and Y beat are almost the same except for minor difference like cable kind for the delay line.

Currently, DC power for amplifiers ZHL-1000LN+ is supplied by Aligent E3620A.
I tried to use power supply from the side of 1X1 rack, but fuse plug(Phoenix Contact ST-SI-UK-4) showed red LED, so I couldn't use it.
Measured amplification was +25 dB for 10-100 MHz.

Measured gain from RF input to monitor output of the beat box was ~ -1 db for 10-100 MHz.

beatsetup20120623.png

  6874   Tue Jun 26 01:30:13 2012 yutaSummaryGreen Lockingsimultaneous hold and release of the arm (aka two arm ALS)

To get the feeling of the master of IFO, I;

1. Stabilized both arm length using ALS.

2. Ran findIRresonance.py for both arms and find what offset gives me IR resonances.

3. Holded X arm to IR resonance, holded Y arm to IR resonance, and released both arms.

Below is the time series data of what I did.
ALSboth20120625_2withAS.png


Issues:
 - Currently ALS is not stable enough. It only stays for about few minutes. I think it is because of the bad alignment of green from each end.
 - We can't tell end green frequency is higher or PSL green frequency is higher. So, the sign of the servo filter sometimes flips.
 - Wobbliness of X end green transmission beam spot was from the ETMX oplev. When the oplev servo is on, it got more wobbly when X end table is opened. But when the oplev servo was off, wobbliness was same even if the presence of air flow.
 - MICH contrast in plot above seems like it somehow got better when two arms are at resonance by ALS. I think this is not real because reflection from both arms at AS port was not well aligned and beam was clipped. Koji and I measured contrast of FPMI and MI(ETMs misalined), and they were 99.6 % and 99.9 % respectively. Beam clipping seems like it comes from some where between BS to AS port. We need to figure out where and fix this.

Things need to be done to make ALS more concrete:
 - Align Y end green beam!
 - Look into Y end green frequency servo
 - How do we hand-off servo using ALS to IR lock?
 - Noise budgeting for new phase tracker scheme
 - Linearity check of the beat box and phase tracker

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

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

HR:

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

AR:

  • 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.

  6942   Mon Jul 9 05:15:46 2012 yutaUpdateGreen Lockinglocked MI while ALS using ASDC

I locked MI while both arm length are stabilized at IR resonance. This could be done using DC READOUT, in other words, use AS_DC as MICH error signal.
Lock using RF signals are still not successful.

FPMIALStrial20120709.png

  6966   Thu Jul 12 11:55:00 2012 JenneUpdateGreen LockingNew BS mounts for PSL beats - Y is finished

Yuta and I bought some new BS mounts so that we could use the 4th port of the beamsplitters which are combining the PSL green and the arm transmitted beam, just before the Beat PD for each arm.  I just placed the Yarm one, and have aligned the light onto both the Beat PD and the Trans DC PD. 

I'll do the Xarm after lunch.

  7002   Mon Jul 23 13:30:06 2012 JenneUpdateGreen LockingYarm ALS laser is funny / dying

Jamie and I were doing some locking, and we found that the Yarm green wasn't locking.  It would flash, but not really stay locked for more than a few seconds, and sometimes the green light would totally disappear.  If the end shutter is open, you can always see some green light on the arm transmission cameras.  So if the shutter is open but there is nothing on the camera, that means something is wrong.

I went down to the end, and indeed, sometimes the green light completely disappears from the end table.  At those times, the LED on the front of the laser goes off, then it comes back on, and the green light is back.  This also corresponds to the POWER display on the lcd on the laser driver going to ~0 (usually it reads ~680mW, but then it goes to ~40mW).  The laser stays off for 1-2 seconds, then comes back and stays on for 1-2 minutes, before turning off for a few seconds again.

Koji suggested turning the laser off for an hour or so to see if letting it cool down helps (I just turned it off ~10min ago), otherwise we may have to ship it somewhere for repairs :( 

  7004   Mon Jul 23 18:01:30 2012 JenneUpdateGreen LockingYarm ALS laser is funny / dying

 I turned the Yend laser back on....it hasn't turned itself off yet, but I'm watching it.  As long as we leave the shutter open, we can watch the C1:ALS-Y_REFL_DC value to see if there's light on the diode.

  7007   Mon Jul 23 18:41:15 2012 JamieUpdateGreen LockingALS_END.mdl model added for end station green ALS channels

The end sus models (c1scx and c1scy) both contain some ALS stuff.  This stuff could maybe be moved to their own models, but whatever.

The stuff at X and Y were identical, but were code copies (BAD!).  I made a new library part for the ALS end controls: ${userapps}/isc/c1/model/ALS_END.mdl

It contains just some filter modules for the ALS end laser control, and a monitor of the ALS end REFL PD DC.  I also added a DQ block for the recorded channels (see screen shot).

When I added this new part to c1scx and c1scy I made it so the channel names would be more sensible.  Instead of "GCX" and "GCY", they are now "ALS-X" and "ALS-Y".  They will now all show up under the ALS subsystem.

 

 

Attachment 1: alsend.png
alsend.png
  7009   Mon Jul 23 19:00:26 2012 KojiUpdateGreen LockingALS_END.mdl model added for end station green ALS channels

This is a good modification. We just need to check how the ALS scripts are affected.

Quote:

The end sus models (c1scx and c1scy) both contain some ALS stuff.  This stuff could maybe be moved to their own models, but whatever.

The stuff at X and Y were identical, but were code copies (BAD!).  I made a new library part for the ALS end controls: ${userapps}/isc/c1/model/ALS_END.mdl

It contains just some filter modules for the ALS end laser control, and a monitor of the ALS end REFL PD DC.  I also added a DQ block for the recorded channels (see screen shot).

When I added this new part to c1scx and c1scy I made it so the channel names would be more sensible.  Instead of "GCX" and "GCY", they are now "ALS-X" and "ALS-Y".  They will now all show up under the ALS subsystem.

 

  7180   Tue Aug 14 16:19:12 2012 JenneUpdateGreen LockingXend doubling crystal heater unplugged, replugged

I went down to the Xend table to look at it to understand Steve's proposal, and I noticed that the doubling crystal's heater's cable is mushed between the table's edge and the black table cover wall.  This made me sad, so I disabled the heater, turned it off, then unplugged the cable from the back of the controller.  I tried to re-route the cable through the hole in the black table cover wall, but going that way the cable is ~1 foot too short.  So I put it back the way it was, but used a totally hacky solution to prevent the cable from being mushed.  I put a dog clamp right at the edge of the table so it is pushing on the table cover wall a little bit, to give the cable space to get out.  This is very mickey mouse, and kind of lame.  But we either need to make a cable extension, or somehow get the heater controller to sit much, much higher under the table.

I plugged the heater controller back in, and turned it back on to the same setpoint that it was at (I think 37.5C).  It's probably warm by now, but when I turned it back on, the heater's actual temp was 33C.

  7241   Tue Aug 21 01:59:33 2012 JenneUpdateGreen LockingGreen locking needs help!

The green beam for the Xarm is flashing a pretty nice 00 mode, but isn't catching lock.

The green beam for the Yarm isn't flashing at all that I can tell from just the camera views.  I don't have energy to start this sometimes monumental task tonight, so I leave it for Future Jenne to work on.

  7261   Thu Aug 23 21:53:06 2012 JenneUpdateGreen LockingXgreen still wouldn't lock

[Jenne, Jamie]

We took a look at the Xend green, and we weren't able to make it lock.  We improved the alignment a little bit, and when we looked at the error signal, it looked nice and PDH-y, but for whatever reason, the cavity won't catch lock.

While aligning the green to the arm, Jamie noticed that the reflection from the intracavity power (not the prompt reflection) was not overlapping with the input beam or prompt reflection.  This means that the cavity axis and the input green beam were not co-linear.  I adjusted the BS and ITMX to get the IR transmitted beam (which had been near clipping on the top edge of the first (2 inch) optic it sees out of the vacuum) back near the input green beam spot on the combining beam splitter.  Then we continued tweaking the green alignment until we saw nice TEM00 flashes in the cavity.  The SNR of the error signal increased significantly after this work, since the cavity buildup was much higher.  But alas, still no lock. 

  7266   Thu Aug 23 22:54:32 2012 JenneUpdateGreen LockingXgreen still wouldn't lock

Quote:

[Jenne, Jamie]

We took a look at the Xend green, and we weren't able to make it lock.  We improved the alignment a little bit, and when we looked at the error signal, it looked nice and PDH-y, but for whatever reason, the cavity won't catch lock.

While aligning the green to the arm, Jamie noticed that the reflection from the intracavity power (not the prompt reflection) was not overlapping with the input beam or prompt reflection.  This means that the cavity axis and the input green beam were not co-linear.  I adjusted the BS and ITMX to get the IR transmitted beam (which had been near clipping on the top edge of the first (2 inch) optic it sees out of the vacuum) back near the input green beam spot on the combining beam splitter.  Then we continued tweaking the green alignment until we saw nice TEM00 flashes in the cavity.  The SNR of the error signal increased significantly after this work, since the cavity buildup was much higher.  But alas, still no lock. 

 I tweaked the alignment of ITMX and ETMX a teeny bit to get the TEM00 flashes back (the work in the previous elog was pre-dinner, so it had been a few hours), then took a screenshot of the error signal and refl dc power on the photodiode for the green xend setup.

The error signal is certainly noisy, although I think when Jamie and I were looking at it earlier this evening, the SNR was a little better.

I need to look at the modulation depth, to see if it's correct, ... maybe lock the Xarm on IR and scan the green laser PZT to check the sideband heights.

I should also check to make sure that the PD is powered, and the gain is high enough (currently the PD gain is set to 20dB).  Earlier today, when I set the gain to 30dB, Jamie said that it was saturating, so I put it back down to the 20dB where we found it.

Still no lock of the green though :(

 

Edit: realized I was bad and didn't label the traces on the plot:  green is refl dc power, blue is demodulated error signal.

Attachment 1: Xarm_Green_ErrorReflSignals_23Aug2012_LowRes.png
Xarm_Green_ErrorReflSignals_23Aug2012_LowRes.png
  7716   Thu Nov 15 21:52:48 2012 Den, AyakaUpdateGreen Lockingyarm locked

We aligned and locked Y arm for green:

  • installed camera on PSL to monitor green transmission
  • aligned green path on the ETMY table to see the beam on the PSL camera
  • misaligned ETMY and aligned ITMY to see reflected beam on REFL PD
  • installed green transmission PD on PSL
  • aligned ETMY and locked YARM to 00 mode

I've switched error channel cable to output monitor. Whitening filter is need for scattering measurements.

   etmyf.png  yarm.png

  7718   Fri Nov 16 03:12:39 2012 Ayaka, DenUpdateGreen Lockingxarm locked

We aligned and locked xarm for green.

etmxf.png

  7719   Fri Nov 16 09:57:57 2012 JenneUpdateGreen Lockingxarm locked

Quote:

We aligned and locked xarm for green.

 

 That's really, really awesome!

 

  7731   Tue Nov 20 11:40:19 2012 ranaConfigurationGreen LockingEnd table upgrade for auxiliary green laser : ETMX layout on new table

 

 Mounts:

  1. No more mounts using the 1" dia. pedestal / fork technology.
  2. No more mounts using the 1/2" post / post holder technology. Both of these are loose, weak, and cause noise.
  3. All steerable mirror mounts which carry the important sensing beams should use steel mounts (e.g. Polaris from Thorlabs). Aluminum mirror mounts are not to be used.
  4. The mounts must be mounted to a 3/4" steel post (these are the custom ones we used in the PSL; Steve should get some more of them made).
  5. The post is then mounted on an aluminum base (The BA2 or BA3 (2" x 3" aluminum) from Thorlabs is OK. The 1" x 3" ones are not). These must be fastened to the table using 2 screws, each with a SS washer.

 

  8259   Fri Mar 8 15:27:42 2013 yutaUpdateGreen LockingPSL green shutter installed

[Manasa, Yuta]

Mechanical shutter for PSL green is installed right in front of PSL doubling crystal.
This is for blocking PSL green when we want to measure the power of green beam from the arms.

The shutter was previously sitting on AS table un-used. Channel name to control this shutter was C1:AUX-SPS_Shutter. This should be renamed as C1:AUX-GREEN_PSL_Shutter.

Next:
  We are going to restore both arm green in parallel to PRMI work.

  - Coarsely align IR input pointing and arms using A2L
  - Align X green
  - Install green DC PDs and cameras on PSL table

  8290   Wed Mar 13 21:04:37 2013 JenneUpdateGreen LockingPSL green cleaned up

Both X and Y green are aligned such that the arm beams hit the broadband PD.  Also, the 4th port of the combining BS for each arm was used to put a camera and DC PD for each arm.  So, ALS-TRX and ALS-TRY are both active right now.  The camera currently labeled "GRNT" is the Ygreen transmission.  I have a camera installed for Xgreen transmission, but I have not run a cable to the video matrix.  For now, to speed things up, I'll just use the GRNT cable and move it back and forth between the cameras.

  8291   Thu Mar 14 04:20:54 2013 JenneUpdateGreen LockingYbeat attempt

I dedicated my evening to trying to get the Ygreen beatnote (the idea being to then get the Xgreen beatnote).

First up was tweaking up the green alignment.  Per Yuta's suggestion, elog 8283, I increased the refl PD gain by 2 clicks (20dB) to keep the lock super stable while improving the alignment.  After I finished, I turned it back to its nominal value.  I discovered that I need lenses in front of the DC PD (for Ygreen, and I'm sure Xgreen will be the same).  The beam is just barely taking up the whole 2mm diode, so beam jitter translates directly to DC power change measured by the diode.  I ended up going just by the green transmission camera for the night, and achieved 225uW of Ygreen on the PSL table.  This was ~2,000 counts, but some of the beam is always falling off the diode, so my actual counts value should be higher after installing a lens. 

I then opened up the PSL green shutter, which is controlled by the button labeled "SPS" on the shutter screen - I will fix the label during some coffee break tomorrow.  Using my convenient new PSL green setup, removing the DC PD allows the beam to reflect all the way to the fuse box on the wall, so you can check beam overlap between the PSL green and the arm green at a range of distances.  I did this for Ygreen, and overlapped the Ygreen and PSL green. 

I checked the situation of the beat cabling, since Jamie has the beatbox out for whitening filter modifications tonight.  In order to get some signal into the control room, I connected the output of the BBPD amplifier (mounted on the front of the 1X2 rack) directly to the cable that goes to the control room.  (As part of my cleanup, I put all the cables back the way I found them, so that Jamie can hook everything back up like normal when he finishes the beatbox.) 

I then started watching the signal on the 8591E analyzer, but didn't magically see a peak (one can always hope....).

I decided that I should put the offset in the Y AUX laser slow servo back to the value that we had been using for a long time, ~29,000 counts.  This is where things started going south.  After letting that go for a minute or two, I thought to go check the actual temperature of the laser head.  The "T+" temperature on the controller read something like 42C, but the voltmeter which reads a voltage proportional to the temp (10C/V) was reading 5.6V.  I immediately turned off the offset, but it's going to take a while for it to cool down, so I'll come back in the morning.  I want the AUX laser to be something like 34C, so I just have to wait.  Ooops.

Still to do (for the short-term FPMI):

* Find Y beatnote.

* Align Xgreen to the arm - it's still off in pitch.

* Align Xgreen and PSL green to be overlapped, hitting the BBPD.

* Find the X beatnote.

* Reinstall the beatbox.

* Use ALS to stabilize both arms' lengths.

* Lock MICH with AS.

* Look at the noise spectrum of AS - is there more noise than we expect (Yuta and Koji saw extra noise last summer), and if so, where does it come from?  Yuta calculated (elog 6931) that the noise is much more than expected from just residual arm motion.

* Write a talk.

  8293   Thu Mar 14 13:38:29 2013 JenneUpdateGreen LockingPSL green cleaned up

I ran a cable to the GTRX camera.  It is now input #2.  The videoswitch script input naming is modified to match this:  Input 2 used to be "IFOPO", and is now "GTRX".  Input 28 used to be "GRNT", and is now "GTRY".  Both green trans cameras are available from the video screen.

  8294   Thu Mar 14 16:41:48 2013 JenneUpdateGreen LockingYarm ALS laser is funny / dying

Quote (elog 7002, 23July2012):

Jamie and I were doing some locking, and we found that the Yarm green wasn't locking.  It would flash, but not really stay locked for more than a few seconds, and sometimes the green light would totally disappear.  If the end shutter is open, you can always see some green light on the arm transmission cameras.  So if the shutter is open but there is nothing on the camera, that means something is wrong.

I went down to the end, and indeed, sometimes the green light completely disappears from the end table.  At those times, the LED on the front of the laser goes off, then it comes back on, and the green light is back.  This also corresponds to the POWER display on the lcd on the laser driver going to ~0 (usually it reads ~680mW, but then it goes to ~40mW).  The laser stays off for 1-2 seconds, then comes back and stays on for 1-2 minutes, before turning off for a few seconds again.

Koji suggested turning the laser off for an hour or so to see if letting it cool down helps (I just turned it off ~10min ago), otherwise we may have to ship it somewhere for repairs :( 

 This is happening again to the Yend laser.  It's been fine for the afternoon, and I've been playing with the temperature.  First I have been making big sweeps, to figure out what offset values do to the actual temperature, and more recently was starting to do a finer sweep.  Using the 'max hold' function on the 8591, I have seen the beat appear during my big sweeps.  Currently, the laser temperature measurement is at the Yend, and the RF analyzer is here in the control room, so I don't know what temp it was at when the peaks appeared.

Anyhow, while trying to reaquire lock of the TEM00 mode after changing the temperature, I find that it is very difficult (the green seems misaligned in pitch), and every minute or so the light disappears, and I can no longer see the straight-through beam on the camera.  I went down to the end, and the same symptoms of LED on the laser head turning off, power out display goes to ~40mW, are happening.  I have turned off the laser as was the solution last time, in hopes that that will fix things.

Manasa has done some work to get the Xgreen aligned, so I'll switch to trying to find that beatnote for now.

  8296   Thu Mar 14 17:31:57 2013 ManasaUpdateGreen LockingX arm green locked in TEM00

Quote:

Manasa has done some work to get the Xgreen aligned, so I'll switch to trying to find that beatnote for now.

[Jenne, Manasa]

Aligned X-arm green in TEM00.

It was difficult to get the X-arm to lock in TEM00 earlier. Even when it locked, it was just a TEM00 flash. The green was mainly bad in pitch.

I started aligning with the arms flashing in IR and it was still not possible to lock. The second trial was with the arms locked in IR; I lost the green lock when the arms were aligned for IR. I aligned by overlapping the ingoing green with the reflected green visible on the steering mirror. This got the green to lock in TEM00; but still it would only stay that way for 30 sec. Jenne pointed me to Yuta's suggestion of increasing the green refl PD gain. Once I increased the PD gain, the mode stabilized.

I went ahead and centered ALS TRX on the PD and GTRX camera (on the PSL table). ALS_TRX reads 2000+ counts.

EDIT by Jenne:  This corresponds to a power of 550uW on the PSL table, measured before the first out-of-vac steering mirror.

  8297   Thu Mar 14 20:22:33 2013 JenneUpdateGreen LockingXbeat attempt

I aligned the Xgreen and PSL green to overlap on the X beat PD, and reconnected the splitter which combines the X and Y beat signals and sends them to the control room.

I've been stepping the Xend laser temperature offset in steps of 20 counts, making sure the cavity unlocks and relocks on TEM00.  So far I have not seen any beat signals for the Xarm.  I've gone from 0 to 840.

I'll be back in a few hours to keep trying, although interested parties are invited to give it a whirl. 

 

  8298   Fri Mar 15 01:57:02 2013 JenneUpdateGreen LockingX arm green locked in TEM00

This work earlier today had required moving the harmonic separator back closer to its original position, so that the green could get through without clipping.  I locked the Xarm (overriding the trigger) and realigned TRX to the PD and camera.

  8300   Fri Mar 15 02:19:01 2013 JenneUpdateGreen LockingYarm ALS laser is funny / dying

I turned the laser back on around 1am.  This is still happening, although right now it is turning off more often than before, maybe every 15 seconds or so.  I am going to turn off the laser for the night.

The measured laser temperature is about 45C (I have a 25,000 count offset in the Y ALS Slow control right now....higher offset, lower temp), although the measured laser temp drops to ~43.5C when the power goes down.

  8301   Fri Mar 15 15:26:13 2013 KojiUpdateGreen LockingYarm ALS laser is funny / dying

I took a look at the laser. It is probably the LD TEC (DTEC) failure.
As the temperature of the LD (DTMP) gradually deviated from 25degCish,
the DTEC voltage also went up from 2Vish to 2.1, 2.2... 

When DTEC reaches 3V, it stopped lasing. This cools the diode a bit, and
it start lasing but repeat the above process.

I am not sure which of the head and controller has the issue.

The situation did not improve much by reducing the pumping current (ADJ: -15).

BTW, Turning on/off the noise eater did not change the situation.

I think the head/controller set should be sent out to JDSU and find how they will say.

  8307   Mon Mar 18 14:58:15 2013 SteveUpdateGreen Lockingrepair or replace dead NPRO

 

 JDSU can repair the Lightwave M126-1064-700 NPRO, sn 415  They do not need the Controller sn 516 

 Posted in the 40m Wiki_ PSL_ NPRO  cost repair and/or option to buy Innolight laser as replacement

  8365   Thu Mar 28 07:58:15 2013 SteveUpdateGreen LockingNPRO repair

Quote:

 

 JDSU can repair the Lightwave M126-1064-700 NPRO, sn 415  They do not need the Controller sn 516 

 Posted in the 40m Wiki_ PSL_ NPRO  cost repair and/or option to buy Innolight laser as replacement

 NPRO shipped out for evaluation yesterday under RMA 18022707

  8569   Tue May 14 01:56:20 2013 JenneUpdateGreen LockingXend Green tweaked

I locked the Xarm on green.  At the PSL table, I adjusted the steering mirror to get the beam centered on the GTRX DC PD.  We need a lens for this, and presumably for the GTRY as well. 

I then went down to the Xend, and adjusted the steering mirrors to maximize the transmitted green power.  I got as high as 2150 counts.

Either the alignment is particularly delicate, or something isn't quite right, but when I put the lid back on the optical table's box, the arm will no longer lock on the 00 mode.  It's pretty typical that the cavity will unlock while you put on the lid, but usually if you bang on the underside of the table, or toggle the green shutter, you'll get back to the 00 mode.  Tonight however, I can't get the 00 mode if the lid is on.  If I slide the lid off just enough to get my hand inside, then block the green beam with my hand, I immediately lock on the 00 mode.  Even if I gently slide the lid back on, I unlock the cavity, and with the lid on can't get better than a 01 mode in yaw.  I repeated this a few times, with the same result. 

A goal for the next few days:  Re-find the Xgreen beatnote.  Once we have the PRMI locking stably and reliably, we want to move on to PRFPMI.   

  8570   Tue May 14 02:19:13 2013 KojiUpdateGreen LockingXend Green tweaked

Note that I'm supposed to return one of the two green beat PDs and the power supply.
They are on the REFL path. I'll work on the restoration of the beat configuration.

  8607   Tue May 21 18:18:23 2013 ManasaUpdateGreen LockingXend Green aligned

X arm aligned to green.

Aligned the X arm to IR.
Used steering mirrors to align the X end green to the X arm while remaining locked for IR. X arm locks to green stably with GTRX at the PSL table measuring 235uW and corresponds to 2560counts in C!:ALS-TRX_OUT.

Next
1. PSL green alignment.
2. Search for beat note.
3. Resurrect ALS for X arm.

  8610   Tue May 21 23:29:57 2013 ManasaUpdateGreen LockingXend Green aligned

X-green and PSL green have been aligned so that they interfere at the beat PD for X.

I haven't scanned the X-end NPRO temperature to find the beat note. I found the earlier elog when this was done (elog 6851) and will use those temperatures to start with.

  8651   Tue May 28 19:35:17 2013 ManasaUpdateGreen LockingStill searching for the X green beat note

Procedure

1. Aligned X-arm to IR.
2. Aligned green to the X-arm.
3. PSL green and X-green aligned to the X-green beat PD.
4. Scanned X-green laser temperature (sweep X slow servo offset through the whole range)

I did not succeed in finding the beat note; but noticed something I cannot explain.
With green very stably aligned to the X-arm, GTRX reads 3000 counts. But when the laser temperature is changed and the green unlocks and locks to the X-arm, it locks with GTRX counts over 5000. GTRX stays at 5000 counts as long as the temperature is changing but settles down to 3000 (over a time lapse of tens of seconds) when let to stay at any specific temperature.

  8653   Thu May 30 01:02:41 2013 ManasaUpdateGreen LockingFound it!

X green beat note found!

Key points
1. Near-field and far-field alignment on the PSL table. The near-field alignment checked by looking at the camera and the far-field alignment checked by allowing the beams to propagate by removing the DC PD.
2. Check laser temperature and get a sense of how the offset translates to the actual laser temperature.
3. Get an idea of the expected temperature of laser using the plot in elog.

Data
PSL laser temperature = 31.45 deg C

X end laser temperature = 39.24 deg C
C1-ALS-X_SLOW_SEERVO2_OFFSET = 4810
Amplitude of beat note = -40dBm

I do not understand why
1. The amplitude of beatnote falls linearly with frequency (peak traced using 'hold' option of the spectrum analyzer).
2. I found the beat note at the RF output of the PD. Earlier, while I was trying to search for the beatnote from the RFmon output of the betabox, there was a strong peak at 29.6MHz that existed even when the green shutters were closed. It's source has to be traced.

Next
Solve beatbox puzzle and lock arm using ALS.

IMG_0598.JPGIMG_0599.JPG

  8666   Mon Jun 3 21:09:55 2013 ManasaUpdateGreen LockingX green beatnote through beatbox

I connected the X green beat PD output back to the beatbox, did the usual PSL alignment for green and searched for the beat note from the RFmon of the beatbox.

Yuta had used a power splitter which took Xbeat-RFmon and Ybeat-RFmon and used the SUM port to monitor the beat signals. I have removed this splitter and just used the X beat RFmon.

I found the beat note with:

Beat@58.7MHz : Amplitude -30dBm
C1:ALS-TRX_OUT16 = 3000 counts
C1:PSL-FSS_SLOWDC = 0.2250
PSL temperature = 31.52 degC
X- green temperature = 39.34 degC (OFFSET = 5140)

Next
Beatbox calibration

IMG_0608.JPG

  8691   Sat Jun 8 00:24:11 2013 AnnalisaUpdateGreen LockingY arm locked with green but bad mode matching

[Annalisa, Nic]

After connecting the PD with the reflection from the arm  to the PDH box, theY  arm has been locked on the 01 mode.  Maximizing the alignment, we obtained a 00 mode locking, but we couldn't maximize the power.

The size of the reflected beam was different with respect to the size of the incoming beam, so probably a bad mode matching was one of the issues.

Moreover, the reflected beam is very low power. We need to figure out why it is so (bad alignment? related to mode matching?)

 

After measuring better all the distances, I did a new mode matching calculation. I put the lenses after measuring the beam waist, so the size of the beam on the lenses was the same as expected from the calculation. Nevertheless, the beam size on the beam splitter looks bigger than expected, and also in this case green flashes into the cavity at some HOM (again 01).

I also tried to lock again the cavity and maximize the alignment, but I didn't get any improvement with respect to the previous mode matching.

 

  8692   Mon Jun 10 21:39:26 2013 AnnalisaUpdateGreen LockingY arm locked with green but bad mode matching

 

Still no good locking!

After making the reflected beam size closer to the injected one, I maximized alignment. I locked again in 00 mode, but I couldn't maximize the power. 

I just realized that maybe I'm not using the correct radius of curvature for the ETMY in the simulation. Tomorrow I will start checking from that.

  8693   Tue Jun 11 10:00:54 2013 nicolasUpdateGreen LockingY arm locked with green but bad mode matching

Quote:

 

Still no good locking!

After making the reflected beam size closer to the injected one, I maximized alignment. I locked again in 00 mode, but I couldn't maximize the power. 

I just realized that maybe I'm not using the correct radius of curvature for the ETMY in the simulation. Tomorrow I will start checking from that.

 Also make sure you are taking into account the substrate of the ETM.

  8694   Tue Jun 11 22:16:56 2013 ManasaSummaryGreen LockingALS for X arm

I discussed with Yuta about the ALS servo and phase tracker and found that there was a lot of information lying around from last year but there aren't any clear elogs on how to enable ALS and obtain IR resonance.

 

Guide to enabling the ALS servo and find IR resonance:

The steps will explain in detail how to ressurrect the ALS servo for green X-arm and find IR resonance using ALS. The medm screens are very confusing right now.

 

(i) Finding the beat note

1. Get the IR to flash in TEM00 for the arm and lock it by enabling LSC (Locking the arm to IR keeps the arm cavity mirrors stable so that you can scan the temperature of the X-end laser to find the beat note).

2. Steer the X-green into the arm cavity such that the arm cavity locks in TEM00 for green as well. At this point you should also have the X-green reaching the PSL table.

3. Align the PSL doubled green (PSL-green) and the X-green in near-field (at the camera) and far-field (letting the beams to propagate beyond the Green-TRX PD).

4. Check cabling of the RF beat PD.

5. Change the X-laser temperature by sweeping the offset (C1: ALS-SLOW_SERVO2_OFFSET) in steps of 10.

6. Find the beat note and tune the alignment at the beat PD to maximize the beatnote amplitude. Disable LSC for X arm.

 

(ii) The GREEN HORNET explained

'Input signal conditioning' block takes I and Q signals after the delay frequency discriminator (DFD) in the beat box and these signals pass through C1ALS_BEATX_FINE filter banks. The output signal then enters the phase rotation matrix of the phase tracker. The phase tracker gives 'PHASE_OUT' which is the error signal that is fed to the ETM servo filter module (DOF filters)  through the 'Input matrix' in the medm. 

An offset can also be fed to the phase tracker which will scan the beat frequency (used to find IR resonance).

 

(iii) Scripts

1. easyALS.py - This runs from 'ON plus' or 'ON minus' buttons in the C1ALS_COMPACT. 

The script clears history of 'fine_phase' filter module and increases gain of the servo in steps ('ON plus' for positive gain and 'ON minus' for negative gain).

2. findIRresonance.py - This runs from 'IRres' button in the C1ALS_COMPACT.

It adds offset to the phase tracker in steps which scans the beat frequency to find IR resonance.

P.S. Check the scripts before enabling the servo so that the right filter modules are being turned ON. Using the wrong set of filter modules can kick the ETM.

____________________________________________________________________________________________________________________________________________________

X arm ALS progress:

I found the beat note and got ALS to work reasonably for the Xarm without kicking the ETM. I did this by manually toggling buttons and changing gains. The scripts need editing.

To do:

Modify the scripts to work as we want them to.

The ALS medm is SSSOOOO confusing. It definitely needs to be fixed (remove all unwanted parts of the screen that existed 'pre-phase tracker').

Find IR resonance.

 
  8695   Wed Jun 12 01:56:58 2013 AnnalisaUpdateGreen LockingY arm locked with green but bad mode matching

 

 For the mode matching calculation I was using the ETMY focal length that I found on Kiwamu's plot on the wiki page. 

Taking into account also the substrate, the focal length turns out to be

fl = ((n-1)*(1/R1 - 1/R2 + (n-1)d/(nR1R2)))^(-1) = -125.81 m

with n = 1.46071 (refraction index of fused silica at 532nm)

R1 = 5625 m (radius of curvature of the first surface)

R2 = 57.37 m (radius of curvature of the second surface)

d = 25mm (thickness)

 

The value of the focal length is sligthly different from the one I was using before in the calculation, but maybe it is enough to change the coupling.

The mode matching solution I found is very sensitive to the lenses position. 

The beam waist position can vary up to 20m varying by 1cm the first lens position, while it is slightly less sensitive to the second lens displacement.

As shown in the picture, along the green beam path there is also a 1m focal length lens. It's position is fixed, because it is along the IR transmetted beam path also. I tried to get a better solution without it, but I found that the waist position was still strongly dependent on one of the two lenses position, so it would not solve the problem to remove this lens.

I think that the main issue of this mode matching is related to the "space contraints", because the two lenses' positions can vary in a very small space, even though the green beam path on the table is quite long.

Eventually, I put the MM lenses found from this last simulation on the table, and it seems to work, since I've seen very strong 00 flashes. Unfortunately, while trying to maximize the alignment I broke it  and I have to do it again, but I feel confident! 

Attachment 1: waistVaryingLensPos.pdf
waistVaryingLensPos.pdf
Attachment 2: green.JPG
green.JPG
Attachment 3: ModeMatchingY.pdf
ModeMatchingY.pdf
ELOG V3.1.3-