Sun, 27 Jan 2002
W. Traub

New IONIC-3T Alignment Procedure
================================

We have found a new, faster alignment method for the integrated optics
(IO), which seems to work well, and for which I invite comments.  The
bottom line is that I have found a way to rig a small mirror and
retro, to replace the beamsplitters that the Grenoble folks originally
provided on the IO table.  The beamsplitters have been a source of
difficulty because they seem not to be optically flat, and the images
seen through them are often quite faint.  Now all alignment can be
done from the end of the 10-foot (large) table, and most adjustments
are within reach.  The trick is to use a mirror which is small enough
that it deflects only one-half of the full 45-mm beam.

                      /-----------------------------\----- to telescopes  
to ccd-------   retro \-------\ small     dich/-----/ retro
                              | mirror         \
                              |                 \
                             eye                to fiber

We also set up a nice bright light source to back-illuminate the IO.
This uses a high-intensity desk lamp, a lens, and a small mirror to
deflect the image of the lamp onto the IO end.  This give much more
light than the non-focused previous version, and it is a snap to
align.  You can see the fiber output in a bright room even through the
dichroics.  With this method, the whole alignment can be done in the
afternoon within an hour, and when a star is acquired the only step
left is to fine-tune the star image on the fiber end.  The procedure
follows.
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align020126.txt 26 January 2002 W.A. Traub

                    IOTA Alignment with Integrated Optic Combiner:
                               New Quick Method

      (Repeat cycle for each beam.  Steps 1-6 before dark; step 7 with
star.)  (All visual adjustments are via alignment telescope at end of
long table.)
         
1. Align optics toward telescope.

  Use alignment telescope and 45-degree large mirror aimed toward
  telescope.
  
  Vacuum in tank.
  
  ST tip-tilt electronics on, switched to the null state.
  
  LD at home.
  
  Adjust mirror to view center of exit mirror, SD, and LD mirror.
  
  LD to 5-10 m, to improve centering on the LD mirror; skip if OK from
  day before.
  
  Yaw, corner, LEDs, feed, and piezo.
  
  End on secondary cross-hairs.

2.  Set up two-way mirror.  
  
  Use alignment telescope and small offset 45-degree mirror aimed
  toward CCD.
  
  Insert 4-inch high retro near two-way mirror (on CCD side), biased 1
  cm south.
  
  Focus on secondary target, tilt mirror to center on cross-hairs.
  
3.  Align fiber.
  
  Turn on fiber x-y piezo, center the 10-turn pots at 5 turns.
  
  Use hi-intensity lamp, lens, and loose mirror to shine 4-mm spot on
  IO.
  
  Insert 6.5-inch high retro centered in path between dichroic and
  telescope.
  
  View bright fiber output spot, center on crosshairs by tilting dichroic.

4.  Align CCD: coarse.
  
  Remove 4-inch high retro, keep 6.5-inch retro.
  
  Illuminate CCD with bright desk lamp.
  
  View CCD, center coarsely by tilting CCD mirrors (a helper is
  useful).
  
  Remove 4-inch retro; remove two-way mirror.

5.  Align CCD: fine.
  
Set up laptop near CCDs, to monitor CCD output image.

  Insert 6.5 inch mirror in path between dichroic and telescope.

  Fiber x-y piezo still on.

  Turn loose mirror so halo of 4-mm spot is off IO, to reduce light
  level.

  Turn CCD mirror screws to center fiber image in quadrant, to 0.5
  arcsec.
  
6.  Align Picnic (3 beams).

  Illuminate parabolas with light from secondary covers.

  Adjust x-y screws on lens mount to center 6-spot IO image on pixels.

  Adjust z-screw to focus spots.

7.  Acquire star.

  Find star on acquisition TV.

  Spiral search, lock star on CCD.

  Set up laptop on table near parabolas.

  Adjust pots to peak star signal on Picnic pixel; FWHM is 1 full
  turn.