[EricQ, Manasa, Koji]

We measured the spot positions on the MC mirrors and redid the MC alignment by only touching the MC mirror sliders. Now all the MC spots are <1mm away from the center.

We opened the ITMY and ETMY chambers to align the green to the arm. The green was already centered on the ITMY. We went back and forth to recenter the green on the ETMY and ITMY (This was done by moving the test masses in pitch and yaw only without touching the green pointing) until we saw green flashes in higher order modes. At this point we found the IR was also centered on the ETMY and a little low in pitch on ITMY. But we could see IR flashes on the ITMYF camera. We put back the light doors and did the rest of the alignment using the pitch and yaw sliders.

When the flashes were as high as 0.05, we started seeing small lock stretches. Playing around with the gain and tweaking the alignment, we could lock the Y arm in TEM00 for IR and also run the ASS. The green also locked to the arm in 00 mode at this point. We aligned the BS to get a good AS view on the camera. ITMX was tweaked to get good michelson.

The X arm was also aligned for the IR by hand and ASS. Also the X end green PZT was aligned to make the TEM00 mode reasonably locked.

What I did:

- Looked at the ITMXF camera. It seemed that the green beam was hitting the mirror.

- Went to the end. Looked at the X end green REFL. Tuned coarse alignment of the ETMX so that the beam was (retro-)reflected to the Faraday and the REFL PD.

- Looked at the ETMX face from the view port. Tried to locate the spot from the ITMX by shaking the ITMX alignment with 0.1 and then 0.01 increments.

- After some struggle with the ETMX and ITMX alignment, resonant fringes were found on the ETMY face while I still looked at the ETMX.

- Once the ITMX/ETMX were aligned, the BS needed to be aligned. But of course there was no IR fringe.

- Returned to the original alignment of the ITMX to find the ITMX spot on the AS camera.
Then gradually moved the ITMX to the aligned value for the green while tracking the michelson alignment with the BS.
This made the AS spots at the upper left edge of the AS video image.

- This was enough to find the IR spikes at TRX. Then the ETMX was touched to maximize the transmission.

- Lock the cavity. Use the ASS to optimize the alignement.

- Once the arm mirrors were aligned, the Xend PZT was also adjusted to have TEM00 for the green beam.

Now I leave the IFO with ITMX/Y, ETMX/Y and BS aligned. As I wrote above, the AS spot is very high at the AS camera.
We need to revisit the AS steering (SR TTs?) to ensure the AS beam unclipped.

[EricQ, Manasa]

We are close to the end of the vent except for a couple of issues.

* POP is not visible on the IR card. But we see POP flashes unclipped on the camera and also spikes in POP DC. So  we are assuming that the POP path hasn't gone far off. If anybody has suggestions for a better method to check this, we could give it a try.

* PRM suspension has not been behaving well. PRM is being kicked around every 5-10 seconds when the PRC is aligned (as seen on REFL camera). We are not sure where this is coming from. The first time we saw this happening was when we were trying to lock PRC at low power even before we took the heavy doors off. So we are pretty sure this is not caused by the foil cover on the OSEMs. We tried turning ON/OFF the oplev servo, turning ON/OFF the damping loops and also checked the connections in the feedthrough and satellite box for the PRM. The OSEM sensor values for the suspension also seem to match the ones on the wiki.

Closeup checklist

• Center beam on all AS optics

• GET CAMERA IMAGES OF EVERYTHING

  • We must get images right before closing, right after closing, etc.
• Make sure REFL is clear
  • dither PRM, see motion on AP tables
• Make sure AS is clear
  • dither BS/ITM, see motion on AP tables
• Using IPANG/POS pick-off mirrors, center beams on:
  • IPPOS
  • IPANG (IPANG aligned to be low in pitch. The beam comes out of vacuum unclipped and hits the first steering mirror outside vacuum at its lower edge)
• Check green alignment in the arms and make sure the transmitted green reaches the PSL table.

• Check all OpLevs centered, in and out of vacuum

• Close PSL shutter & green shutters at the ends

• Check jam nuts

This is solved.

The ASC for PRC for left turned ON. Turning it OFF solved the problem.

If there is no feedback regarding the POP alignment or anything to check with modified PRC length, we will close tomorrow morning.

 This sounds great! The only suggestion that I have is for checking POP. If you have the beam on the camera, you can hold a card in front of each mirror, and find out where the edge of the beam is. Introduce the card from the side, and watch for the point where you just start to see the beam on the camera be obstructed. Repeat for the other side, and you have an idea of the centering of the beam. 

I think this is most important for the in-vac mirrors, since the beam is large-ish, and we have to hit both steering mirrors at ~45 degrees.

 [EricQ, Manasa]

This check was done and we had to move one of the steering mirrors in pitch. Else, everything was just fine.

In-vacuum pictures of PR2 and PR3 new positions were taken. MC spot positions measured to be < 1mm and oplevs were centered.

[Steve, Manasa]

I checked the alignment one last time. The arms locked, PRM aligned, oplevs centered.

We went ahead and put the heavy doors ON. Steve is pumping down now!

[Manasa, ericq]

Both arms have been aligned via ASS. PRC locked on carrier.

SB locking hasn't happened yet...

Details:

• Aligned MC at low power, measured spots
• Found ITMX AS, REFL spots on cameras. Couldn't find ITMY spot. Found x-arm flashes with PRM aligned.
• MC Refl Y1 mirror was replaced with the 90:10 BS; blocked WFS path until MC was aligned
• PMC power was increased (~1.4W directly before PSL shutter)
• Touched up MC alignment, reactivated high power autolocker, measured spots.
• Locked x-arm on IR, ran ASS
• Found ITMY spot on AS camera, locked y-arm, ran ASS on both arms
• Checked green beams. Y-arm locks at around .6, X-arm at around .2 (input steering needs adjustment)
• Centered beams on WFS, reset filter bank offsets, turned on WFS
• Aligned PRM, locked PRC on carrier.
• Tried locking PRC on sideband, had troubles. Looks like there is some increased seismic activity; might be the culprit.

[ericq]

PRC Locked on Sidebands

Jenne reminded me that if we change a cavity, phases can change... So, first, I locked the PRC on the carrier, and then gave it MICH and PRCL excitations to optimize the AS55 and REFL55 phase rotation angles by looking at the excitation demodulated outputs of the unused quadrature (i.e. we want all of MICH to be in AS55 Q, so I rotated the phase until C1:CAL-SENSMAT_MICH_AS55_I_I_OUTPUT was zero on average).

This resulted in:

• AS55: 7 -> -5.5
• REFL55: 73 -> 86.9

I then used the same settings as in ELOG 9554, except I used -1s instead of +1s for the POP110I trigger matrix elements. (I'm not sure why this is different, but I noticed that the PRC would lock on carrier with positive entries here, so I figured we wanted the peaks with opposite sign).

So far, it seems more stable than when we were doing the demodulation phase measurements, it's been locked for >15 minutes without me having to tweak the gains or the alignment from the carrier locked case.

 Nice work!!  As with all the other RF PDs, POP110's phase likely needs tuning.  You want POP110 (and POP22) I-quadratures to be maximally positive when you're locked on sidebands, and maximally negative when locked on carrier.  What you can do to get close is lock PRC on carrier, then rotate the POP phases until you get maximally negative numbers.  Then, when locked on sideband, you can tweak the phases a little, if need be.

 Very good news! We should have a look at the POP110 sideband peak splitting, to see if we really got the right PRC length... 

Adjusted the angles as Jenne suggested:

• POP22: 105 -> 163
• POP110: 150 -> -83

• Adjusted the PMC alignment
• Adjusted the IMC length offsets for the MC servo and the FSS servo
• Adjusted the MC alignment. Ran /opt/rtcds/caltech/c1/scripts/MC/WFS/WFS_FilterBank_offsets
 
• The Yarm servo was oscillating. Reduced the servo gain from 0.2 to 0.08.
 
• AS Camera & AS port alignment was adjusted. Now the spot is at the center of the AS camera.
• Cleaned up the ASC offsets on the suspensions (i.e. C1:SUS-***_(PIT|YAW)_OFFSET) by replacing them by the BIAS adjustment.
• Saved the alignment values
• Locked the PRMI with SB with REFL55I for PRCL and AS55Q for MICH
• Aligned the PRM, then checked the alignment of the REFL PDs
• The best POP110I was 500cnt.
• Found REFL165 output was disconnected. It is now restored.
   
• Used the LSC lockins to figure out the demod phases and the signal amplitudes (relative)

PRCL: 100cnt -> PRM 567.01Hz

Signal in demod Q ch were minimized

REFL11I -19.2deg demod I, Lockin I out (C1:CAL-SENSMAT_PRCL_REFL11_I_I_OUTPUT) 12.6 cnt
REFL33I +130.4deg 1.70cnt
REFL55I +17.0deg 2.30cnt
REFL165I -160.5deg 27.8cnt

MICH: 1000cnt -> ITMX(-1) & (ITMY +1.015 => Minimized the signal in REFL11I to obtain pure MICH)

REFL11I   +0.0     REFL11Q   +0.119
REFL33I   +0.023 REFL33Q   -0.012
REFL55I   +0.023 REFL55Q   -0.113
REFL165I +0.68   REFL165Q +0.038

It seems that REFL165 has almost completely degenerated PRCL and MICH.

• Try to replace ITMX/Y with BS (+0.16) / PRM (-0.084)

 ITMX(-1)/ITMY(+1.015) actuation was cancelled by BS (+0.16). This introduces PRCL in REFL11I. This was cancelled by PRM (-0.084)

REFL11I   +0.0     REFL11Q   +0.13
REFL33I   -0.012  REFL33Q   0.025
REFL55I   +0.041 REFL55Q   -0.45
REFL165I +0.69   REFL165Q +/-0.02

Again, It seems that REFL165 has almost completely degenerated PRCL and MICH.

Locking info:

PRCL:
[Signal source] REFL11I (-19.2deg) x 0.16, OR REFL33I (+130.4deg) x 2.0, OR REFL55I (+17.0deg) x1.0, OR REFL165I (-160.5deg) x0.05
[Trigger] POP110I(-81deg) 100/10, FM trigger 35/2, delay 0.5sec FM2/3/6/9
[Servo] FM4/5 always on. G=-0.02, Limitter ON
[Output] PRM x+1.00

MICH:
[Signal source] AS55Q (-5.5deg) x 1, OR REFL11Q x 0.25, OR REFL55Q x-0.06
[Trigger] POP110I 100/10, FM trigger 35/2, delay 5sec FM2/3/9
[Servo] FM4/5 always on. G=-10, Limitter ON
[Output] ITMX -1.0 / ITMY +1.0 (or +1.015), OR PRM -0.084 / BS +0.16

The PRC (locked on carrier so far today), is pretty wobbly.  It'll stay locked on carrier, but it's wobbling.  The ASC was over-ridden during the vent.  While I was looking around for that, I noticed that the PRM oplev sum is very low. 

I went into the lab, and turned off / blocked all oplev beams except the PRM beam.  I can't tell what it's clipping on, but there is definitely some red glow in the BS chamber (not as much as the stuff that's coming from the ITMY or SRM oplev hitting a tip tilt suspension - that giant spot went away when I turned off the ITMY/SRM oplev laser).  The beam going into the vacuum is nice and strong, but the beam coming out is very weak, and has a horizontal line of scatter through it, like it's clipped somewhere in pitch.  The PRM oplev sum is currently ~150 cts, when it should be closer to 2,000.

So far, this seems to be livable, but it's definitely disappointing. 

In an effort to stop the PRC from wiggling around so much, I recentered the POP QPD after maximizing the POPDC power when locked on carrier.  The beam was basically off the QPD in yaw, and at half-range in pitch.

MC tuning

Although the morning MC tuning looked stable, Koji pointed out that the MC_REFL_OFFSET was changed from its nominal value.

The offset was reset and this caused drift in the MC_TRANS_SUM.

To fix this:

- disabled the WFS servo

- aligned MC using MC1 and MC3

- centered beam on the MC_REFL

- reset WFS offsets

- locked MC

MC looks happy now.

__________________________________________________________________________________________________________________

ALS locking

ALS is in a very different state from a couple of days ago when we could successfully lock the arms and scan.

The green alignment to the arms had drifted.

PSL green alignment on the PSL table was off. The PSL green was not even on the steering mirror. Did anyone work around the PSL table in the last couple of days?

After aligning and finding the beat note, I found the ALS servo very noisy. The error signal had 10 times more rms noise than what was achieved earlier this week and there were some new 60Hz peaks as well.

Overall, we could not do any PRMI+ALS arms today

As I didn't have the green laser PZT feedback for the laser temp control, I went to the yend to check out what's the situation.

I found horrible and disgusting "remnants".

WHAT ARE THESE BSs AT THE Y END?

- The table enclosure was left open

- A (hacky) DB25 cable with clips was blocking the corridor and I was about to trip with the cable.

- This DB25 cable went to the table without going through the air tight feedthrough that is designed for this purpose.

- An SR560 (presumably for the openloop TF measurement) was left inserted in the loop with entangled cables connected to the servo box.

- Of course the laser PZT out mon was left unplugged.

Even after cleaning these cables (a bit), the end setups (including the X end too) are too amature.
Everything is so hacky. We should not allow ourselves to construct this level of setup everytime
we work on any system. This just adds more and more mysteries and eventually we can't handle
the complexity.

1) Fixup REFL165: remove ND filters, get box for PD, dump diode reflections, put less light on diode, change DC transimpedance (?), max power dissipation on BBPD < 0.5 W w/ 25 V bias. Perhaps replace OP27 with TLE2027.

2) Make plan for fixing fiber layout up and down the arms. Need tubing for the whole run. Don't make it cheesy. Two fibers per arm.

3) Fix LSC model to allow user switching of whitening. Get back to working on AutoLock scripts (not Guardian).

4) Manasa, Q, Jenne, tune Oplev servos Tuesday morning/afternoon.

5) Reconnect the other seismometers (Steve, Jenne). For real.

6) Balance PRMI coils at high frequency.

CMG-40T handheld controller unit is missing its power supply. In order to zero the instrument one has to apply plus and minus DC voltage.

The wiring on this 10 pin Amphenol PT02E-12-10P is shown.

I confirmed that we need to vent the chambers.

All of the mirrors have been aligned except for ETMX.

ETMX does not respond to the excitation by the UR and LR coils. Likely that the magnets are knocked off, or stuck in the coil.

PRM/SRM oplevs are too much off and can't be turned on. Need realignment of the beams on the QPDs.

- FB was down. FB restarted ("telnet fb 8087", then type shutdown)

- Aligned the MC mirrors.

- Aligned PRM. Look at the REFL. It was slightly mislisligned.

- AS has no beam. The Y arm was resonating with the green. So I determined that the TTs were the misaligned guys.

- Touched TT2 pitch with an increment of 0.1. Immediately the AS beam spot for ITMY was found. And the arm was resonating.

- The RM was further aligned. The bias sliders were saved and then the PRM was misaligned.

- Yarm was locked on TEM01. The ASS maximized the transmission for TEM01, and then the arm was locked on TEM00.
  The ASS aligned the arm and TTs. These values were saved.

- Yarm was aligned and I can see the AS spot. So I believe the BS is still well aligned.

- Aligned the PRM to reduce the ghost beams.

- Moved the ITMX to have Michelson fringes properly.

- Also aligned the SRM.

- Now ETMX was checked. Played with the alignment biases to see if the mirror was sticking on the coils. The mirror can rock a little, but it did not come back.

- Then, checked each magnets. 0.8Hz 1000cnt signals were injected to each coils (cf. C1:SUS-PRM_**COIL_EXC) to see how the mirror could react.
  The OSEM output and green spot on the ETMX cage were observed.

- Saw some response by actuating the UL, LL, SD coils.

- Saw no response from the UR and LR coils. They show the OSEM output of zero. Does this mean the magnets fell in the coils?

//Manasa// MC spot positions measured and they look alright with not much change from before the earthquake (attach)

I tried to take the photos of the magnets from outside. So far most suspicious was LL.
Otherwise, the magnets are OK.
(The SD magnet is the one with most reasonable response.)
Steve will try to take much more zoomed photo with Olympus. But the LL coil already showed some response in my observation in the morning.

[ Manasa, Ericq and Steve ]

 Vivitek D952HD with 186 hours installed.

I'm checking the status from home.

P1 is 8e-4 torr

nodus did not feel the power outage (is it APS supported?)

linux1 booted automatically

c1ioo booted automatically.

c1sus, c1lsc, c1iscex, c1iscey need manual power button push.

 9:11pm closed PSL shutter, turned Innolight 2W laser on,

         turned 3 IFO air cond on,

        CC1 5.1e-5 torr, V1 is closed, Maglev has failed, valve configuration is " Vacuum Normal "  with V1 & VM1 closed, RGA not running,   c1vac1 and c1vac2   were saved by UPS,

        (Maglev is not connected to the UPS because it is running on 220V)

        reset & started Maglev.........I can not open V1 without the 40mars running...........

        Rossa is the only computer running in the control room,

        Nodus and Linux1 was saved by UPS,

        turned on IR lasers at the ends, green shutters are closed

It is safe to leave the lab as is.

As far as I know the system is running as usual. I had the IMC locked and one of the arm flashing.
But the other arm had no flash and none of the arms were locked before kunch time.

This morning Steve and I went around the lab to turn on the realtime machines.

Also we took the advantage of this opportunity to shutdown linux1 and nodus
to replace the extension cables for their AC power.

I also installed a 3TB hard disk on linux1. This was to provide a local daily copy of our
working are. But I could not make the disk recognized by the OS.
It seems that there is a "2TB" barrier that the disk bigger than 2.2TB can't be recognized
by the older machines. I'll wait for the upgrade of the machine.

Rebooting the realtime machines did not help FB to talk with them. I fixed them.
Basically what I did was:

- Stop all of the realtime codes by running rtcds kill all on c1lsc, c1ioo, c1sus, c1iscex, c1iscey

- run sudo ntpdate -b -s -u pool.ntp.org on c1lsc, c1ioo, c1sus, c1iscex, c1iscey, and fb

- restart realtime codes one by one. I checked which code makes FB unhappy. But in reality
  FB was happy with all of them running.

Then slow machines except for c1vac1 and c1vac2 were burtrestored.

-------

Zach reported that svn was down. I went to the 40m wiki and searched "apache".
There is an instruction how to restart apache.

Recovery work: now arms are locking as usual

- FB is failing very frequently. Everytime I see red signals in the CDS summary, I have to run "sudo ntpdate -b -s -u pool.ntp.org"

- PMC was aligned

- The main Marconi returned to initial state. Changed the frequency and amplitude to the nominal value labeled on the unit

- The SHG oven temp controllers were disabled. I visited all three units and pushed "enable" buttons.

- Y arm was immediately locked. It was aligned using ASS.

- X arm did not show any flash. I found that the scx model was not successfully burtrestored yesterday.
  The setting was restored using Mar 22 snapshot.

- After a little tweak of the ETMX alignment, a decent flash was achieved. But still it could not be locked.

- Run s/LSC/LSCoffset.py. This immediately made the X arm locked.

- Checked the green alignment. The X arm green is beating with the PSL at  ~100MHz but is misaligned beyond the PZT range.
  The Y arm green is locked on TEM00 and is beating with the PSL at ~100MHz.

The following that went unnoticed from yesterday were recovered today:

1. ETMX and ETMY 'misalign' scripts weren't running. Troubleshooting showed slow machines c1auxex and c1auxey weren't responding. The machines were reset.

2. PRM oplev gains were zero. Gain values were set looking back at the burt files.

3. X end PZT power supplies were turned ON and set to 100V.

4. X end doubler temperature was reset to the last optimal value on elog (36.35 deg).

Some hitches that should be looked into:

1. Check: ASS for X arm seems not quite doing its job. ETMX has to be moved using sliders to obtain maximum TRX and the arm alignment was seen to be drifting.

2. Check: Status of other slow machines and burt restore whichever needs one.

ETMX ASC output was turned off for whatever reason. Switched it on, ASS is fine.

[Koji Rana]

We are looking at NTP settings. I looked at nodus.

- xntpd is running

- We decided to start over the configuration file /etc/inet/ntp.conf

    - The old configuration was moved to ntp.conf.bak

    - The server configuration file was copied from ntp.server to ntp.conf

    - Caltech NTP servers 131.215.239.14 and 131.215.220.22 were selected as the servers we are reffering

    - Commented out the lines for "fudge" and "broadcast"

- xntpd was restarted

    - sudo /etc/init.d/xntpd stop
    - sudo /etc/init.d/xntpd start

- check how the daemon is running
      tail -50 /var/adm/messages

   Mar 28 23:00:49 nodus xntpd[27800]: [ID 702911 daemon.notice] xntpd 3-5.93e Mon Sep 20 15:47:11 PDT 1999 (1)
   Mar 28 23:00:49 nodus xntpd[27800]: [ID 301315 daemon.notice] tickadj = 5, tick = 10000, tvu_maxslew = 495, est. hz = 100
   Mar 28 23:00:49 nodus xntpd[27800]: [ID 798731 daemon.notice] using kernel phase-lock loop 0041
   Mar 28 23:00:49 nodus last message repeated 1 time
   Mar 28 23:00:49 nodus xntpd[27800]: [ID 132455 daemon.error] trusted key 0 unlikely
   Mar 28 23:00:49 nodus xntpd[27800]: [ID 581490 daemon.error] 0 makes a poor request keyid

- check the syncing staus by ntpq -p

        remote           refid      st t when poll reach   delay   offset    disp
   ==============================================================================
   *ntp-02.caltech. .CDMA.           1 u   37   64  377     0.56    3.010    0.08
   +ntp-03.caltech. ntp1.symmetrico  2 u   36   64  377     0.52    2.727    0.12
      this * means nodus is synced to ntp-02. "+" means it is stand by as a valid secondary server.  "when" increases every second.
      When "when" reaches "poll" the clock is synced to the server. These marks are not set at the beginning.
      It was necessary to wait for sometime to get synced to the server.

- Once nodus became a synced server, the realtime systems starts syncing to nodus automatically.

   controls@c1sus ~ 0$ cat /var/log/ntpd
   25 Mar 01:41:00 ntpd[4443]: logging to file /var/log/ntpd
   (...)
   28 Mar 23:13:46 ntpd[4983]: synchronized to 192.168.113.200, stratum 2
   28 Mar 23:14:25 ntpd[4983]: time reset +39.298455 s
   28 Mar 23:14:25 ntpd[4983]: kernel time sync status change 2001
   28 Mar 23:25:19 ntpd[4983]: synchronized to 192.168.113.200, stratum 2
   controls@c1sus ~ 0$ ntpq -p
        remote           refid      st t when poll reach   delay   offset  jitter
   ==============================================================================
   *nodus.martian   131.215.239.14   2 u   42   64  377    0.140   42.222  11.373


FB: /etc/ntp.conf was updated as below such that it refers nodus and also caltech server when nodus is not available

server 192.168.113.200
server 131.215.239.14

ntpd was restarted and

diskless RT machines: they are booted from /diskless/root on fb.
Therefore /diskless/root/etc/ntp.conf was updated in the same way as above.
When the machines are rebooted, this setting will be active.

control machines:

now they are referring nodus and other external servers too.

Not working again. I tried the commands in Koji's elog as well as the ones from my notes, but the AG 4395 hooked up to the yellow box named crocetta doesn't work. It gets to the stage of opening the data files and hangs. I tried it with many variations on pianosa and rossa. Also tried power cycling the analyzer and the Prologix and the bridge.

While hooked up to the MC error point I set the modulation frequency from 137 to 133 Hz to minimize the 3 MHz peak as usual.

Started working tonight. Don't know if anyone did anything to the Martian network or not, so its a mystery...

I also modified the script and SVN'd it. It now correctly takes your plot wants and adjust the linear/log of the axes accordingly

./SPAG4395A.py -i crocetta -A -v 4 --att=0 --start=1kHz --end=10MHz --bw=1kHz --plot --semiy

and also saves the plot as out.pdf

In the attached image I show the MC board TP1A output. The two peaks around 3.7 Mhz are the sideband beats we speak of. The lower one is proportional to the MC length/frequency mistmatch.

I've moved the WB network analyzer to the OMC lab. The 40m network analyzer is not in service for the MC monitoring.
I setup the configuration so that the same command gives us the same spectrum measurement.

 Eric Q and I set up the optical configuration for razorblade beam analysis on SP table for future use.

It has been aligned, and will be in use on Monday.

The beam will be characterized for future characterization of optical fibers.

Harry will update this elog with details about his beam waist measurements for the old NPRO on the SP table.

 Attached is the weekly work plan / equipment requirement / lab expert's presence needed for the upcoming week.

Purpose

To use a razorblade to measure beam waist at multiple points along the optical axis, so as to later extrapolate the modal profile of the entire beam. This information will then be used to effectively couple AUX laser light to fibers for use in the frequency offset locking apparatus.

Data Acquisition

1) Step the micrometer-controlled razorblade across the beam at a given value of Z, along optical axis, in the plane orthogonal to it (arbitrarily called X).

2) At each value of X, record the corresponding output of a photodiode, (Thorlabs PD A55) here given in mV.

3) Repeat process at multiple points along Z

Analysis

Data from each iteration in the X were fitted to the error function shown below.

V(x) = A*(erf((x-m)/s)+c)

In the Y, they were fitted to:

V(x) = -A*(erf((x-m)/s)+c)

'A' corresponds to an amplitude, 'm' to a mean, 's' to a σ, and 'c' to an offset.

(Only because in Y measurements, the blade progressed toward eclipsing the beam, as opposed to in the X where it progressively revealed the beam.

These fits can be solved for x = (erf^-1((V/A)-c)*s)+m1  which can be calculated at the points (V_max/e²) and (V_max*(1-1/e²)). The difference between these points will yield beam waist, w(z).

Conclusion

Calculations yielded waists of: X1=66.43um, X2=67.73um, X3=49.45um, Y1=61.20um, Y2=58.70, Y3=58.89

These data seem suspect, and shall be subjected to further analysis.

 see http://nodus.ligo.caltech.edu:8080/40m/10098 for the update

See attached weekly update

Reconfigured razorblade analysis setup on the PD table as per instructions. Used it to collect data to calculate beam waist with, analyses to follow.

See attached schematic for optical setup.

Purpose

To use a razorblade to measure beam waist at four points along the optical axis, so as to later extrapolate the waist. This information will then be used to effectively couple AUX laser light to fibers for use in the frequency offset locking apparatus.

Data Acquisition

1) Step the micrometer-controlled razorblade across the beam at a given value of Z, along optical axis, in the plane orthogonal to it (arbitrarily called X).

2) At each value of X, record the corresponding output of a photodiode, (Thorlabs PD A55) here given in mV.

3) Repeat in Y plane at the same value of Z

4) Repeat process at multiple points along Z

Analysis

Data from each iteration were fitted to the error function shown below.

y(x) = (.5*P)*(1-erf((sqrt(2)*(x-x0))/wz))

'P' corresponds to peak power, 'x0' to the corresponding value of x (or y, as the case may be), and 'wz' to the spot size at the Z value in question.

The spot sizes from the four Z values were then fit to:

y(x) = w0*sqrt(1+((x*x)/(zr*zr)))

Where 'w0' corresponds to beam waist, and 'zr' to Rayleigh Range.

Conclusion

This yielded a Y-Waist of 783.5 um, and an X-Waist of 915.2 um.

The respective Rayleigh ranges were 2.965e+05 um (Y) and 3.145e+05  um (X).

Next

I will do the same analysis with light from the optical cables, which information I will then use to design a telescope to effectively couple the beams.

The IR beam was found on the PRM surface, some CCDs, and in the X arm. The TTs are not aligned well yet.

I'm leaving the IFO with the following state.

Status:

ITMY/ETMY - aligned to the given green beam. GTRY (no PSL green) 1.0~1.1

ITMX/ETMX - aligned to the green beam. The end PZT for the green beam was steered to have maximum GTRX (0.76 without PSL green)

TT1/TT2 - unknown alignment, TT1/TT2 are related such that the spot is on the POP CCD

PRM - aligned to the given IR beam (i.e. PRM spot on the REFL CCD)

BS - aligned to the given IR beam (i.e. ITMX spot on the AS CCD, The X arm is flashing)

Notes:

- ITMX was stuck in the suspension. it was caused by the EQ.

- When the X arm was aligned to the green beam, there was no green hitting on the GTRX PD. That's why the end PZT was adjusted.

- In order to earn more range for TT1, C1:IOO-TT1_YAW_GAIN and C1:IOO-TT1_PIT_GAIN were increased to 300 (100 nominal) and the limiter (at 500) were removed.

- The HeNe laser for BS/PRM does not emit the beam even with the driver turned on. Is there a hidden shutter or something? ==> Jenne

TO DO:

- Find the Y arm fringe by moving TT1 and TT2 without loosing the PRM/AS/POP spots.

IR Alignment of the IFO is recovered! Green alignment could use some attention. 

Arms and PRC hold well, powers are within normal ranges. (TR[X,Y] >.9, POP110I > 400)

Details:

• Starting from where Koji had brought things (i.e. beams on REFL, AS), I gradually stepped the PRM back to where I had a PRC lock right before the bootfest, using SUSPIT_IN and SUSYAW IN, while stepping the TT pointing (arbitrarily shifting TT1 and TT2) to keep the REFL camera spot centered. 
• Green was locked fairly well to the Yarm (GTRY = 0.8), so I knew it supported a mode. I misaligned ITMX to keep the Xarm out of the way. 
• Adjusting TT1 and TT2, I was able to get some light on the POP camera, while keeping REFL spot visible with small adjustments to PRM
• I set up the PRM to set up some PRM-ITMY retroreflection, and saw tiny flashes in TRY. 
• From here, I wandered around with the tip-tilts to try and get better arm pointing, while tweaking PRM for the REFL spot and retroflection, and BS for the AS spot. I got this to TRY flashes of ~0.3

Then, Jenne took over, worked some alignment magic, and did the hard part of getting the Yarm locked and ASS'd. 

• I then took back over and got the Xarm locked and ASS'd.
• I saved relevant mirror positions, and set up the PRMI, got it locked, saved PRM position. 
• Jiggled the BS/PRM oplev HeNe power connector, it turns on now, oplevs are working. 
• Similar to TT1, TT2 gains for PIT and YAW are now 300. Strictly speaking, they don't have to be, but PIT would be very nearly railed, and I changed YAW so that all four gains would be consistent.

Caveats:

Green no longer locks to 00 on the Y-arm, and the X-arm green transmission isn't the best despite PZT fiddling (~.6). Also, when green is locked to the Xarm, I see a distinct circular spot on the GTRY camera, with Y green and PSL green shutters closed. 

While Jenne used Yarm ASS successfully, when I run it now, it slowly pushes things out of alignment, and two of the traces (YARM_ETM_YAW_L_DEMOD_I_OUTPUT, and the same for ITM) have a reasonable constant offset that doesn't move away. 

Ophir power meter gets new filter with calibration. This is not cheap. It was the second time we lost it.

Filter leash is attached.

 [Nichin, Eric Q]

We added a new LAN wire from Rack 1Y4 to 1Y1 to connect the RF switch at 1Y1 to the martian network. The wire is labelled "To RF Switch (1Y1)"

The wire was run along the Y arm in the tray right next to the vaccum chamber, not the one on top.

PMC was relocked.

MC did not need any fixing to its alignment. I had to lock it manually and autolocker is set running now. So that should take care of things

The arms were aligned and ASS'd for IR PDH.

Green light PDH locks to the arms alright.

I was finally able to get a reasonable measurement for the beam waist(s) of the spare NPRO.

Methods

I used a razorblade setup, pictured below, to characterize the beam waist of the spare 1064nm NPRO after a lens (PLCX-25.4-38.6-UV-1064) in order to subsequently calculate the overall waist of the beam. The setup is pictured below:

After many failed attempts, this was the apparatus we (Manasa, Eric Q, Koji, and I) arrived with. The first lens after the laser was installed to focus the laser, because it's true waist was at an inaccessible location. Using the lens as the origin for the Z axis, I was able to determine the waist of the beam after the lens, and then calculate the beam waist of the laser itself using the equation wf = (lambda*f)/(pi*wo) where wf is the waist after the lens, lambda the wavelength of the laser, f the focal legth of the lens (75.0 mm in this case) and wo the waist before the lens.

We put the razorblade, second lens (to focus the beam onto the photodiode (Thorlabs PDA255)), and the PD with two attenuating filters with optical density of 1.0 and 3.0, all on a stage, so that they could be moved as a unit, in order to avoid errors caused by fringing effects caused by the razorblade.

I took measurements at six different locations along the optical axis, in orthogonal cross sections (referred to as X and Y) in case the beam turned to be elliptical, instead of perfectly circular in cross section. These measurements were carried out in 1" increments, starting at 2" from the lens, as measured by the holes in the optical table.

Analysis

Once I had the data, each cross section was fit to V(x) = (.5*Vmax)*(1-erf((sqrt(2)*(x-x0))/wz))+c, which corresponds to the voltage supplied to the PD at a particular location in x (or y, as the case may be). Vmax is the maximum voltage supplied, x0 is an offset in x from zero, wz is the spot size at that location in z, and c is a DC offset (ie the voltage on the PD when the laser is fully eclipsed.) These fits may all be viewed in the attached .zip file.

The spot sizes, extracted as parameters of the previous fits, were then fit to the equation which describes the propagation of the spot radius, w(z) = wo*sqrt(1+((z-b)/zr)^2)+c, w(z) = w0*sqrt(1+((((z-b)*.000001064)^2)/((pi*w0^2)^2))) where wo corresponds to beam waist, b is an offset in the z. Examples of these fits can be viewed in the attached .zip file.

Finally, since the waists given by the fits were the waists after a lens, I used the equation wf = (lambda*f)/(pi*wo), described above, to determine the waist of the beam before the lens.

Plots

note: I was not able to open the first measurement in the X plane (Z = 2in). The rest of the plots have been included in the body of the elog, as per Manasa's request.

Conclusion

The X Waist after the lens (originally yielded from fit parameters) was 90.8 27.99 ± .14 um. The corresponding Y Waist was 106.2 30.22 ± .11 um.

After adjustment for the lens, the X Waist was 279.7 907.5 ± 4.5 um and the Y Waist was 239.2 840.5 ± 3.0 um.

edit: After making changes suggested by koji, these were the new results of the fits.

Attachments

Attached you should be able to find the razor blade schematic, all of the fits, along with code used to generate them, plus the matlab workspace containing all the necessary variables.

NOTE: Rana brought to my attention that my error bars need to be adjusted, which I will do as soon as possible.