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ID Date Author Type Category Subjectup
  7255   Thu Aug 23 10:38:12 2012 SteveUpdateGeneralvent prepartion for fast-track vent

Quote:

We are discussing venting first thing next week, with the goal of
diagnosing what's going on in the PRC.

Reminder of the overall vent plan:

https://wiki-40m.ligo.caltech.edu/vent

Since we won't be prepared for tip-tilt installation (item 2), we should
focus most of the effort on diagnosing what's going on in the PRC.  Of
the other planned activities:

(1) dichroic mirror replacement for PR3 and SR3

  Given that we'll be working on the PRC, we might consider going ahead
  with this replacement, especially if the folding mirror becomes
  suspect for whatever reason.  In any case we should have the new
  mirrors ready to install, which means we should get the phase map
  measurements asap.

(3) black glass beam dumps:

  Install as time and manpower permits.  We need to make sure all needed
  components are baked and ready to install.

(4) OSEM mount screws:

  Delay until next vent.

(5) new periscope plate:

  Delay until next vent.

(6) cavity scattering measurement setup

  Delay until next vent.

 Bob is back. Cleaning and baking all our posts and clamps. They will be ready for use Tuesday next week. Therefore beam dumps will be available for installation.

  7558   Tue Oct 16 16:46:20 2012 Vent Czar and CzarinaSummaryGeneralvent stuff

We're discussing the plan for the next vent.  Now that we have all the tip-tilt stuff in hand, we should get ready for the big TT installation vent ASAP.  The question is what remains to be done, and when can we be ready

Stuff that needs doing:

* characterize TTs, check electrical connection of quadrupus cables, bake cables and base plates - a week or so (not including baking)

* phase map of LaserOptik mirrors (decide on needed resolution) - a week or so?

* get ready to swap G&H mirrors with LaserOptik mirrors (PR2, PR3, SR2, SR3)

* assembly of black glass beam dumps - one afternoon

* green periscope moving - day or so to make sure greens are resonant in arms, so we have something to align to

* redraw of REFL path?? (rotate 2nd refl mirror to reflect beam to the east, then add mirror to get beam out of IOO chamber viewport), cut hole in BS oplev table's box, install black beam tube

* FI camera mount - make sure it's here, baked

* active TT pitch damping plan

* passive TT weight addition and pitch alignment plan

* camera plan for taking in-chamber photos without touching the tables

* look at layout of ITMY table.  POY pick-off too close to main beam.  Can we move POY pick-off to BS table?

* remount black glass baffles on SOS cages.

 

Stuff to bake:

* Quadrupus cables

* TT base plates

* FI mirror mount for FI camera

* stuff to add to active TTs

* stuff to add to passive TTs

 

  7560   Tue Oct 16 17:13:23 2012 CzarinaSummaryGeneralvent stuff - 4 paths

I see 4+ possible paths for us to take, in terms of a possible vent in the next few weeks:

No Vent - Just do FPPRMI, using AS55

Mini Vent - Fix REFL path, nothing else.  ~1 day at atmosphere

Medium Vent - Fix REFL path, swap G&H mirrors for LaserOptik mirrors (so also resuspend passive TTs, maybe add pitch adjustment option). ~1 week or so at atmosphere - do this rather than Mini if Jan's Finesse calc says the G&H mirrors are too rough

Mega Vent - Fix all the things, do all the things.  Long time at atmosphere

The "+" is to take into account all the possible variations on "medium vent".  The No, Mini and Medium options assume we'll do the Mega option later, just not immediately.

  66   Tue Nov 6 09:45:22 2007 steveSummarySUSvent sus trend
The mc optics dragwippings were done by locking optics by eq stops and rotating-moving
cages so access were good. This technic worked well with mc1 & mc2
MC3 osems were reoriented only.
Attachment 1: ventsustrend.jpg
ventsustrend.jpg
  2631   Tue Feb 23 13:37:04 2010 kiwamu and steveConfigurationVACventing the 40m vac envelope

Kiwamu and Steve have started venting the 40m vacuum envelope.

Preparation:

centered oplevs at resonating cavities,

ITM references were set by green pointer from the ends by Koji,

closed  PSL shutter and placed manual block into beam path,

checked  jamnuts in locked positions on bellows,

turned  HV off at PZT-Jena "steering mirror" power supply and OMC HV ps

checked  particle counts,

switched oplev servos off,

set up N2 cylinder to start vent from 1e-6 Torr to 25 Torr,

have ~ 6 cylinders of instrument grade compressed air to bring envelope from 25 Torr to 760 Torr

 

All three cranes were wiped off today.

 

  3616   Tue Sep 28 14:12:14 2010 steveUpdateGeneralvertex crane drive is out of order

The vertex crane drive is overheating, it stopped functioning. Service man will be here tomorrow morning.

I crane was just turned  on for for may be  about 5 minutes. The vertical drive was fine for a while, but the horizontal did not worked at all.

The crane is tagged out again and the controller box is cooling down.

  9146   Fri Sep 20 16:37:30 2013 SteveUpdateVACvertex crane folding arm is back on

Quote:

 The folding beam removed as shown. Two man supporting it while I hammering it out. Pin was dry and it gulled into supporting hinges.

The rotating hinge will be machined and bushing will be added with Zerk fitting or similar. This will allow lubrication in the future.

 see elog #9111

Atm1,  The folding arm is back on with 0.1" misalignment at no load in the trolly's way. The other side of the I beam is 0.02" higher than the main beam.. New bushing and pin were greased up  with Krytox before installation.

The axial Zerk 1/8" pipe in the pin upper end can not take any fitting. There is no room. It is taped off.

This gap comes down to ~ 1/16" at fully extended arm with 225 lbs load at the end of it.

The present plan is to grind down the  the misalignment of 0.1"  for a slow-loaded trolly.

Steve Baker of Konacranes will be back to grind down this ridge and load test at 500 lbs on Tuesday,  OCT  1, 2013

 

 

 

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  9139   Wed Sep 18 14:57:12 2013 SteveUpdateVACvertex crane folding arm removed

 The folding beam removed as shown. Two man supporting it while I hammering it out. Pin was dry and it gulled into supporting hinges.

The rotating hinge will be machined and bushing will be added with Zerk fitting or similar. This will allow lubrication in the future.

 see elog #9111

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  9111   Thu Sep 5 10:47:58 2013 SteveUpdateVACvertex crane folding issue

 

 [Fred Goldbar, Mike Gerfen, Dennis Coyne and Steve]

We inspected the hinge, 1.25" cross pin and I-beams. It is hard to explain what is  causing the folding I-beam corner to jam against the main I-beam.

To limit the motion of the folding I-beam  cross pin bushing will be added. This will take a week to complete.

 

 

 

 

 

Attachment 1: 5mmLess.jpg
5mmLess.jpg
  9185   Wed Oct 2 14:25:39 2013 SteveUpdateVACvertex crane is still out of order

 

The smoke alarms were turned off and surrounding areas were covered with plastic.

The folding I-beam was ground down to be in level with the main beam.

Load bearing cable moved into correct position. New folding spring installed.

Crane calibration was done at 500 lbs at the end of the fully extended jib.

Than we realized that the rotating wheel limit switch stopped working.

This means that the crane is still out of order.

 

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Attachment 3: 500lbs@end.jpg
500lbs@end.jpg
  9372   Wed Nov 13 08:46:03 2013 SteveUpdateVACvertex crane repair completed

nullQuote:

 

The smoke alarms were turned off and surrounding areas were covered with plastic.

The folding I-beam was ground down to be in level with the main beam.

Load bearing cable moved into correct position. New folding spring installed.

Crane calibration was done at 500 lbs at the end of the fully extended jib.

Than we realized that the rotating wheel limit switch stopped working.

This means that the crane is still out of order.

 

New limit switch installed and tested. The crane is back in full operational mode. Two spare limit switches on hand.

  9117   Mon Sep 9 15:33:06 2013 SteveUpdateVACvertex crane repair is scheduled

Quote:

 

 [Fred Goldbar, Mike Gerfen, Dennis Coyne and Steve]

We inspected the hinge, 1.25" cross pin and I-beams. It is hard to explain what is  causing the folding I-beam corner to jam against the main I-beam.

To limit the motion of the folding I-beam  cross pin bushing will be added. This will take a week to complete.

 

 

 

 

 

 KoneCrane contact John McDaniel (562) 903 - 1371,

Wednesday, September 18,  folding I-beam will be removed.  KoneCrane will start working at 7:30am and they should be out by 12:30pm

 Friday,  September 20, reinstalling machined hinge on the I-beam. Same timing schedule as Wednesday.

  9173   Mon Sep 30 08:53:22 2013 SteveUpdateVACvertex crane repair schedule has changed

Quote:

Quote:

 The folding beam removed as shown. Two man supporting it while I hammering it out. Pin was dry and it gulled into supporting hinges.

The rotating hinge will be machined and bushing will be added with Zerk fitting or similar. This will allow lubrication in the future.

 see elog #9111

Atm1,  The folding arm is back on with 0.1" misalignment at no load in the trolly's way. The other side of the I beam is 0.02" higher than the main beam.. New bushing and pin were greased up  with Krytox before installation.

The axial Zerk 1/8" pipe in the pin upper end can not take any fitting. There is no room. It is taped off.

This gap comes down to ~ 1/16" at fully extended arm with 225 lbs load at the end of it.

The present plan is to grind down the  the misalignment of 0.1"  for a slow-loaded trolly.

Steve Baker of Konecranes will be back to grind down this ridge and load test at 500 lbs on Tuesday,  OCT  1, 2013

 

 

 

 Konecranes rescheduled the completion of the Vertex crane to Wednesday, Oct. 2

  3624   Thu Sep 30 09:34:58 2010 steveUpdateGeneralvertex crane trolly drive fixed

Quote:

The vertex crane drive is overheating, it stopped functioning. Service man will be here tomorrow morning.

I crane was just turned  on for for may be  about 5 minutes. The vertical drive was fine for a while, but the horizontal did not worked at all.

The crane is tagged out again and the controller box is cooling down.

 Atm1, Vertex crane controller unit on horizontal I-beam.

            Module CCES-407 1HP 2.3A 460V/3 phase on the right was replaced. Speed was increased  to 30 Hz

Atm2, See burned insulation on black wire that was shorting to the large suppressor resistor on Atm3 One can see the pit marks on the right end of it.

        This large power dissipater resistor got hot as the malfunctioning controller 407 broke down.   Touching black power wire insulation melted and made a short.

          So the heat was created and finally the fuses were blown. The unnecessary large fuses were replaced by small ones.

Fortunately we had one spare controller on hand that made this repair to be done fast.

We used the new Crane Safety Check list  from LIGO-E1000379-v1 the first time yesterday before doors were removed.

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  4165   Tue Jan 18 10:25:23 2011 steveUpdatePEMvertex crane work this week

The crane people are here. The Vertex chambers are covered with plastic. The PSL HEPAs will be running on high during the day.

It is going to be disturbingly noisy and dirty during the day. Please try start working in the evening if it can not wait till next week.

  3492   Tue Aug 31 02:50:45 2010 kiwamuUpdateCDSvertex suspensions controlled by the new CDS

I plugged the new CDS to the vertex suspensions. 

Now PRM, SRM, ITMs, MCs and BS are under the control of the new CDS. 

From now on we will never go back to the old system.

 

Though,  the watchdogs are still running on the old system.

So if you need to turn on/off the watchdogs, you can simply enable/disable them from the usual medm screens.

  3699   Tue Oct 12 17:42:57 2010 yutaUpdateSUSvery first measurement of Q-values for MC1

Background:
 Data aquisition system is fixed, and now we can use the Dataviewer to measure Q-values of the ringdowns for each DOF, each optics.
 First of all, I measured MC1 suspention damping servo for a test.

What I did:
1. Used DAQ channels activated in this entry(#3690) to see and compare the ringdowns when the damping servo is on and off with the Dataviewer.

2. Plotted the data and fitted the ringdown using this formula;
  p[0]*exp(-p[1]*t)*sin(p[2]*t+p[3])+p[4]
 I used python's scipy.optimize.leastsq for the fitting.

3. Calculated the resonant frequency f0 and Q-value using following formulas;
  f0=2*pi*sqrt(p[1]**2+p[2]**2)
  Q=f0/(2*pi)/(2*p[1])

4. For plotting, I subtracted the offset(=p[4]).

All parameters I used for this measurement are automatically saved here;
  /cvs/cds/caltech/burt/autoburt/snapshots/2010/Oct/12/13:07/c1mcs.epics
(-1,0,1 for all matrix elements, GAIN=3,3,3,150 for POS,PIT,YAW,SIDE)

Result:
 Attached is the plot of each 4 DOF ringdown when servo is off and on.
 "servo off" means off for that DOF. Servo for the other 3 DOFs are on.

 As you can see clearly, the damping servo is working.

 The resonant frequencies and Q-values calculated from the fitting are as follows;

  servo off servo on
f0 (Hz) Q f0 (Hz) Q
POS 0.97 large 0.97 16
PIT 0.71 96 0.73 6.9
YAW 0.80 100 0.82 8.9
SIDE 0.99 large 0.99 27


 Resonant frequencies and Q-values have about 1% and 10% error respectively.
 I estimated it from my 2-time measurement of the POS ringdown.

Next work:
 - Find and modify some scripts to optimize the matrix elements
 - Calibrate the displacement
 - Do the same thing for other optics

Attachment 1: MC1ringdown.png
MC1ringdown.png
  3347   Mon Aug 2 10:26:15 2010 steveConfigurationVACvery slow pumpdown completed

Quote:

Bob and Steve closed BS chamber with the help of the manual Genie lift and the pump down started. The PSL shutter was closed and manual block was placed in the beam path. High voltage power supplies were checked to be off.

Pumping speed ~ 1 Torr/min was achieved at  1/8 of a turn opened roughing valve RV1

 3 days pump down #69 completed. Thanks to Koji  and Kiwamu  who did more roughing on Saturday and Sunday.

Attachment 1: veryslowpd.jpg
veryslowpd.jpg
  7232   Mon Aug 20 09:49:01 2012 SteveUpdateCamerasvideo cameras in the DARK

Quote:

 The problem with the glow on the ETMY face is due to the red light being scattered off of the optical table from the HeNe laser for the OL. Why is the red light hitting the table?

One way to fix the problem for the camera image is to insert a long pass filter (if Steve can find one).

 Edmund Optics: NT62-874

 Edmund Optics: NT65-731

Edmund Optics: NT32-759 

 

 Atm1, condition: all oplev lasers are off or blocked, green shutters are closed at the ends, PSL out put shutter is closed, all outside LED illuminating are off, all room lights are off

                         Only the OSEMs are on. ETMY and ITMX are still look like illuminated.

Atm2, condition: open PSL shutter. ETMY at 11 o'clock  and ETMX 1 o'clock bright scattered spot of 1064 nm are visible

Atm3, condition: closed PSL shutter and restored all oplev He/Ne lasers, it is visible at ETMY

Next: I will disconnect power to OSEMs at ETMY

Attachment 1: onlyOSEMs.jpg
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OSEMsand_IR.jpg
Attachment 3: OSEMsandOplev633.jpg
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  7215   Fri Aug 17 08:33:46 2012 SteveUpdateCamerasvideo cameras in the dark

Quote:

 I optimized the TM views with illuminator light on quad1  It actually looks better there.

I'll post a dark-  OSEM light only in jpg tomorrow.  ETMY camera is malfunctioning in dark condition now.

 

ALL  illuminator lighting are off. ITMX and ETMY looks back lighted. I will check on their apertures.

In order to focus on 1064 resonant spots I tried to restore and align the arms  by script. I only got flashes.

Attachment 1: dark.jpg
dark.jpg
  7216   Fri Aug 17 09:34:27 2012 KojiUpdateCamerasvideo cameras in the dark
I used the LED illuminations at ETMX and BS yesterday for a tour.
I am afraid that I left them on.
  7217   Fri Aug 17 10:38:15 2012 SteveUpdateCamerasvideo cameras in the dark
> I used the LED illuminations at ETMX and BS yesterday for a tour.
> I am afraid that I left them on.

It was turned off before the picture was taken.
All LED illuminations were turned off. I checked them a few times.
  7219   Fri Aug 17 14:45:51 2012 ranaUpdateCamerasvideo cameras in the dark

 The problem with the glow on the ETMY face is due to the red light being scattered off of the optical table from the HeNe laser for the OL. Why is the red light hitting the table?

One way to fix the problem for the camera image is to insert a long pass filter (if Steve can find one).

 Edmund Optics: NT62-874

 Edmund Optics: NT65-731

Edmund Optics: NT32-759 

  7236   Mon Aug 20 18:10:44 2012 JenneUpdateCamerasvideo capture script copied over to real scripts directory

The videocapture.py script is now in ...../scripts/general/ , along with the videoswitch. 

Also, there's a button gui on the VIDEO medm screen to capture different camera views.

  10259   Wed Jul 23 10:39:18 2014 SteveUpdateCamerasvideo quad processors replaced

Quad processor 2 & 3 were replaced.

  2120   Mon Oct 19 18:14:28 2009 robUpdateCamerasvideo switch broken

The Chameleon HB (by Knox) video switch that we use for routing video signals into the control room monitors is broken.  Well, either it's broken, or something is wrong with the mv162 EPICS IOC which communicates with it via RS-232.  Multiple reboots/resets of both machines has not yet worked.  The CHHB has two RS-232 inputs--I switched to the second one, and there is now one signal coming through to a monitor but no switching yet. I've been unable to further debug it because we don't have anything in the lab (other than the omega iserver formerly used for the RGA logger) which can communicate with RS-232 ports.  I've been trying to get this thing (the iserver) working again, but can't communicate with it yet.  For now I'm just going to bypass the video switch entirely and use up all the BNC barrel connectors in the lab, so we can at least have the useful video displays back.

  8036   Fri Feb 8 12:43:26 2013 yutaUpdateComputersvideocapture.py now supports movie capturing

I updated /opt/rtcds/caltech/c1/scripts/general/videoscripts.py so that it supports movie capturing. It saves captured images (bmp) and movies (mp4) in /users/sensoray/SensorayCaptures/ directory.
I also updated /opt/rtcds/caltech/c1/scripts/pylibs/pyndslib.py because /usr/bin/lalapps_tconvert is not working and now /usr/bin/tconvert works.
However, tconvert doesn't run on ottavia, so I need Jamie to fix it.

videocapture.py -h:
Usage:
    videocapture.py [cameraname] [options]

Example usage:
    videocapture.py MC2F -s 320x240 -t off
       (Camptures image of MC2F with the size of 320x240, without timestamp on the image. MUST RUN ON PIANOSA!)
    videocapture.py AS -m 10
       (Camptures 10 sec movie of AS with the size of 720x480. MUST RUN ON PIANOSA!)


Options:
  -h, --help          show this help message and exit
  -s SIZE             specify image size [default: 720x480]
  -t TIMESTAMP_ONOFF  timestamp on or off [default: on]
  -m MOVLENGTH        specity movie length (in sec; takes movie if specified) [default: 0]

  8612   Wed May 22 00:42:13 2013 KojiSummarySUSviolin Q

While looking at the decay of the violin mode of the PRM, I made a simple measurement of the decay rate.

Error signal: REFL33I

The peak @628Hz became 0.372 to 0.303 in 60 sec.

-> Half life of the amplitude T_{1/2} is 203sec.

Q = 4.53 f0 T_{1/2} = 5.8 x10^5

  1611   Wed May 20 01:53:48 2009 rob, peteUpdateLockingviolin mode filters in drstep_bang

Recently the watch script was having difficulty grabbing a lock for more than a few seconds.  Rob discovered that the violin notch filters which were activated in the script were causing the instability.  We're not sure why yet.  The script seems significantly more stable with that step commented out.

  3875   Sat Nov 6 01:54:15 2010 FrankSummaryComputersvirus definition file update on laptop for dinocam

i took some pictures with the dinocam this afternoon. I used the laptop computer next to it using wireless lan connection to the caltech network to send the pictures to me.

The installed anti virus software was bitching about the old database and wanted to update that. As the installed virus definition database was from mid last year i agreed and started downloading the update. As the file was huge (~100MB) it wasn't finished when i left. computer is still running and probably waiting for instructions.

Will come back on the weekend to finalize the new virus definition file database installation.

  4447   Mon Mar 28 16:19:23 2011 steveFrogsPhotosvisithing 5th graders

Suresh is captivating his audience with gravity waves on last Friday, March 25

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  3682   Fri Oct 8 17:36:16 2010 steveFrogsPhotosvisiting undergrads

Prof Alan Weistein guided the 24 student through the 40m. His performance was rated as  an enthusiastic 9.5

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  5434   Fri Sep 16 16:07:28 2011 steveUpdateSAFETYvisitors safety training

Paul, Mirko and Katrin visiting grad students received the 40m basic safety training.

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  12810   Tue Feb 7 19:14:59 2017 JohannesUpdateCDSvme crate backplane adapter board layout

After fighting with Altium for what seems like an eternity I have finished putting my vision of the vme crate backplane adapter board into an electronic format. It is dimensioned to fill the back space of the crate exactly. The connectors are panel mount and the PCB attaches to the connectors with screws, such that the whole thing will be mechanically much more stable than the current configuration. A mounting bracket will attach to horizontal struts that need to be installed in the crates, mechanical drawings to follow.

Attachment 1: vme_backplane.pdf
vme_backplane.pdf
  12781   Tue Jan 31 22:15:02 2017 JohannesUpdateCDSvme crate backplane adapter boards

I made a crude sketch for how Lydia and I envision the connector situation on the back of the vme crates to be solved. Essentially the side panels of each crate extend about 2" (52 mm) beyond the edge of the DIN connectors. This is plenty of space for a simple PCB board. The connector of choice is D-Sub. We can split the 64 used pins into 2x 37 D-Sub OR (2x25 pin + 1x15pin). The former has fewer cables, but a few excess unused leads. A quick google search showed me that it is much cheaper to get twisted pair cables for 15 and 25 pin D-Subs. From what I remember, the used pins on the DIN connectors are concentrated on the low numbers end and the high numbers end, so might not need the 'middle' connector in many cases if we decide to break it up into three. I have to check this with Lydia though.

The D-Sub connectors would be panel mounted, for which we need a narrow panel piece with dsub cutouts. We can run horizontal struts across the vme crate from side panel to side panel. This way the force upon cable (dis)connection is mostly on the panel which is attached to the struts which are attached to the crate. This will also prevent gravitational sag or cable strain from pulling on the DIN connection, and we can use twisted pair cables with backshell, screws, and strain reliefs.

I was lookng into getting started with the PCB when Altium complained that the license is expired and to renew it. This is a relatively simple board layout so some free software out there is probably enough.

Attachment 1: vme_backplane_conn_sketch.jpg
vme_backplane_conn_sketch.jpg
  6305   Wed Feb 22 16:55:16 2012 JamieUpdateSUSwacky state of SUS input matrices

While Kiwamu and I were trying to investigate the the vertex glitches we were noticing excess noise in ITMX, which Kiwamu blamed on some sort of bad diagonalization.  Sure enough, the ITMX input matrix is in the default state [0], not a properly diagonalized state.  Looking through the rest of the suspensions, I found PRM also in the default state, not diagonalized.

We should do another round of suspension diagonalization.

Kiwamu (or whoever is here last tonight): please run the free-swing/kick script (/opt/rtcds/caltech/c1/scripts/SUS/freeswing) before you leave, and I'll check the matrices and update the suspensions tomorrow morning.

[0]

0.25 0.25 0.25 0.25 0
1.66 1.66 -1.66 1.66 0
1.66 -1.66 -1.66 1.66 0
0 0 0 0 1

  6307   Thu Feb 23 02:20:07 2012 ZachUpdateSUSwacky state of SUS input matrices

This reminds me that the whole Dr. SUS situation never got taken care of. Where I left off, I was having issues pulling 40m data with NDS2 (which is what all the diagonalization scripts use).

What is the deal with 40m+NDS2? If it is till no-go, can we have a consensus on whether this is too important to wait for? If so, I will rewrite the scripts to use NDS and we can upgrade to NDS2 once we can prove we know how to use it.

 

Quote:

While Kiwamu and I were trying to investigate the the vertex glitches we were noticing excess noise in ITMX, which Kiwamu blamed on some sort of bad diagonalization.  Sure enough, the ITMX input matrix is in the default state [0], not a properly diagonalized state.  Looking through the rest of the suspensions, I found PRM also in the default state, not diagonalized.

We should do another round of suspension diagonalization.

Kiwamu (or whoever is here last tonight): please run the free-swing/kick script (/opt/rtcds/caltech/c1/scripts/SUS/freeswing) before you leave, and I'll check the matrices and update the suspensions tomorrow morning.

[0]

0.25 0.25 0.25 0.25 0
1.66 1.66 -1.66 1.66 0
1.66 -1.66 -1.66 1.66 0
0 0 0 0 1

 

  2823   Wed Apr 21 10:09:23 2010 kiwamuUpdateGreen Lockingwaist positon of Gaussian beam in PPKTP crystals

Theoretically the waist position of a Gaussian beam (1064) in our PPKTP crystal differs by ~6.7 mm from that of the incident Gaussian beam.

So far I have neglected such position change of the beam waist in optical layouts because it is tiny compared with the entire optical path.

But from the point of view of practical experiments, it is better to think about it.

In fact the result suggests the rough positioning of our PPKTP crystals;

we should put our PPKTP crystal so that the center of the crystal is 6.7 mm far from the waist of a Gaussian beam in free space.


(How to)

The calculation is very very simple.

The waist position of a Gaussian beam propagating in a dielectric material should change by a factor of n, where n is the refractive index of the material.

In our case, PPKTP has  n=1.8, so that the waist position from the surface of the crystal becomes longer by n.

Now remember the fact that the maximum conversion efficiency can be achieved if the waist locates at exact center of a crystal.

Therefore the waist position in the crystal should be satisfied this relation; z*n=15 mm, where z is the waist position of the incident beam from the surface and 15 mm is half length of our crystal.

Then we can find z must be ~8.3 mm, which is 6.7 mm shorter than the position in crystal.

The attached figure shows the relation clearly. Note that the waist radius doesn't change.

Attachment 1: focal_positin_edit.png
focal_positin_edit.png
  2850   Tue Apr 27 14:18:53 2010 kiwamuUpdateGreen Lockingwaist positon of Gaussian beam in PPKTP crystals

The mode profile of Gaussian beams in our PPKTP crystals was calculated.

I confirmed that the Rayleigh range of the incoming beam (1064 nm) and that of the outgoing beam (532 nm) is the same.

And it turned out that the waist postion for the incoming beam and the outgoing beam should be different by 13.4 mm toward the direction of propagation.

These facts will help us making optical layouts precisely for our green locking.


(detail)

The result is shown in the attached figure, which is essentially the same as the previous one (see the entry).

The horizontal axis is the length of the propagation direction, the vertical axis is the waist size of Gaussian beams.

Here I put x=0 as the entering surface of the crystal, and x=30 mm as the other surface.

The red and green solid curve represent the incoming beam and the outgoing beam respectively. They are supposed to  propagate in free space.

And the dashed curve represents the beams inside the crystal.

A trick in this calculation is that: we can assume that  the waist size of 532 nm is equal to that of 1064 nm divided by sqrt(2) . 

If you want to know about this treatment in detail,  you can find some descriptions in this paper;

"Third-harmonic generation by use of focused Gaussian beams in an optical super lattice" J.Opt.Soc.Am.B 20,360 (2003)"

Attachment 1: mode_in_PPKTP.png
mode_in_PPKTP.png
  3325   Thu Jul 29 21:13:39 2010 DmassUpdateGreen Lockingwaist positon of Gaussian beam in PPKTP crystals

Quote:

The mode profile of Gaussian beams in our PPKTP crystals was calculated.

I confirmed that the Rayleigh range of the incoming beam (1064 nm) and that of the outgoing beam (532 nm) is the same.

And it turned out that the waist postion for the incoming beam and the outgoing beam should be different by 13.4 mm toward the direction of propagation.

These facts will help us making optical layouts precisely for our green locking.


(detail)

The result is shown in the attached figure, which is essentially the same as the previous one (see the entry).

The horizontal axis is the length of the propagation direction, the vertical axis is the waist size of Gaussian beams.

Here I put x=0 as the entering surface of the crystal, and x=30 mm as the other surface.

The red and green solid curve represent the incoming beam and the outgoing beam respectively. They are supposed to  propagate in free space.

And the dashed curve represents the beams inside the crystal.

A trick in this calculation is that: we can assume that  the waist size of 532 nm is equal to that of 1064 nm divided by sqrt(2) . 

If you want to know about this treatment in detail,  you can find some descriptions in this paper;

"Third-harmonic generation by use of focused Gaussian beams in an optical super lattice" J.Opt.Soc.Am.B 20,360 (2003)"

If I understand your elog, you are just calculating the the offset in position space that you get by having a refractive index.

Did you end up changing the mode matching so that the rayleigh range (which changes with refractive index) was confocally focused inside the crystal (e.g. Zr = 15 mm?

 

  3327   Thu Jul 29 22:58:25 2010 kiwamuUpdateGreen Lockingwaist positon of Gaussian beam in PPKTP crystals

- As you said, I just calculated the waist position in the crystal because the speed of light changes in a medium and eventually the waist position also changes.

- Yes, I did. Once you get a beam with the right waist size, you just put your crystal at the waist position with the offset.

  In fact you don't have to think about the rayleigh range inside of the crystal because what we care is the waist size and it doesn't change.

Quote:

 If I understand your elog, you are just calculating the the offset in position space that you get by having a refractive index.

Did you end up changing the mode matching so that the rayleigh range (which changes with refractive index) was confocally focused inside the crystal (e.g. Zr = 15 mm?

  3328   Fri Jul 30 00:02:15 2010 DmassUpdateGreen Lockingwaist positon of Gaussian beam in PPKTP crystals

Quote:

- As you said, I just calculated the waist position in the crystal because the speed of light changes in a medium and eventually the waist position also changes.

- Yes, I did. Once you get a beam with the right waist size, you just put your crystal at the waist position with the offset.

  In fact you don't have to think about the rayleigh range inside of the crystal because what we care is the waist size and it doesn't change.

Quote:

 If I understand your elog, you are just calculating the the offset in position space that you get by having a refractive index.

Did you end up changing the mode matching so that the rayleigh range (which changes with refractive index) was confocally focused inside the crystal (e.g. Zr = 15 mm?

 I thought we cared about satisfying the confocal focusing parameter, that is to say we want to set Zr = 2L_crystal. If Zr changes inside the crystal, this is the number we care about..isn't it NOT the waist size, but the rayleigh range we care about? I am not entirely sure what youre response is saying you did...

  1. Calculate Zr = pi * wo^2/(lamba/n)
  2. Do mode matching to get this wo in free space
  3. Calculate the offset you need to move the oven by using n
  4. Move hte ovens

OR

  1. Calculate Zr = pi*wo^2/(lamba)
  2. Do mode matching to get this in free space
  3. Calculate the offset you need to move your ovens using n
  4. Move your ovens

I guess the waist size would also let me know - are you using 69 um or 53 um waist size?

  15566   Wed Sep 9 20:52:45 2020 ranaSummaryIOOwandering line in IMC

since the summary pages are working again, I was clicking through and noticed that there's a wandering peak in the whitened IMC spectrogram that goes from 10-30 Hz over the course of a day.

https://nodus.ligo.caltech.edu:30889/detcharsummary/day/20200909/ioo/

anyone know what this is ?

  11487   Mon Aug 10 15:25:05 2015 SteveUpdatePEMwasp nest

The wasp nest will be removed tomorrow from from the out side of the east arm window.

The resonant frequency of the newly arrived gravity bee detector is not known.
 

Attachment 1: waspN.jpg
waspN.jpg
  2309   Fri Nov 20 16:18:56 2009 robConfigurationSUSwatchdog rampdown

I've changed the watchdog rampdown script so it brings the SUS watchdogs to 220, instead of the 150 it previously targeted.  This is to make tripping less likely with the jackhammering going on next door.  I've also turned off all the oplev damping.

  2372   Wed Dec 9 17:51:03 2009 kiwamuUpdateSUSwatchdogs

Please do not touch the watchdogs for all SUSs except for MCs,

because I am going to measure the free swinging spectra for ITMs, ETMs, BS, PRM, SRM tonight.

Today, it is good chance to summarize those data under atmospheric pressure.

thank you.

 

  6060   Thu Dec 1 17:33:18 2011 kiwamuUpdateSUSwatchdogs fixed

The watchdogs' issue has been solved and they are now working fine.

It was just because one of the Sorensens had been off.

The Sorensen is the one supplying +5 V in the 1X5 rack.
This +5 V is actually used as a pull-up-current to properly drive the MAX333As (CMOS analog switch) in the coil drivers (D010001).
So this was it.

Quote from #6010

Tonight we noticed that, in fact, the watchdogs don't work for any of the corner optics (I confirmed that they do work for the ETMs).

  3456   Mon Aug 23 15:24:24 2010 kiwamuConfigurationSUSwatchdogs off

For the new CDS test, I turned off the watchdogs for PRM, SRM, BS, ITMs and MCs.

I will restore these watchdogs after several hours from now.

 

  4024   Tue Dec 7 20:38:17 2010 kiwamuUpdateSUSwatchdogs off at ITMX and ETMX

I am leaving ITMX and ETMX freely swinging, so that later I can take the spectra and diagonalize the input matrices.

Please don't restore the watchdogs until tomorrow morning.

  4031   Wed Dec 8 22:47:09 2010 kiwamuUpdateSUSwatchdogs off at ITMX and ETMX

Tonight, swing again.

Please do not restore the watchdogs until tomorrow (Dec.9) morning.

Quote: #4024

I am leaving ITMX and ETMX freely swinging, so that later I can take the spectra and diagonalize the input matrices.

Please don't restore the watchdogs until tomorrow morning.

 

ELOG V3.1.3-