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chara:climb_lab_alignment

CLIMB Lab Alignment

This set of instructions is intended to help recover a lost beam on the CLIMB table.

First, use the green laser to check the usual CHARA alignment check up to the CLIMB table target (visbeams, dichroics, IR mirrors). Set one telescope on each beam.

When all IR mirror alignments are good, then the idea is to trace the laser through each path separately to the small aperture behind NIRO's window. When the green spot is in the hole, it is barely shining at the perimeter of the hole, otherwise you see a bright spot when you look NIRO “in the eye” from the opposite side of the table.

It is important to look at one path at a time, and correctly identify which adjustment needs to be done. Using the CLIMB layout diagram (printed on the desk at ctrscrut) you can decide what to cover and what to adjust. To block paths there are business cards folded at one side to hang on two of the fold mirrors that are in a row behind the table cover, middle of the table at MIRC side. Remove that table cover first.

For completeness here are all the steps checking all beams:

The best lighting for this is incandescent light in the lab, not too dim, when you can easily move around and see all parts on the table. Green laser at ND=0, just like for the IR mirror alignment check. The steps are listed for Beams 123, but can be replaced with 456. It is best to do a visual check with the green laser in the lab AND with the white light source on the camera to figure out what is misaligned BEFORE adjusting the picos.

  1. Open IR beam 1 shutter only. Cover the fold mirror labeled IR23, and IR123B. Adjust pico7 motors labeled IR123A if necessary.
  2. Open IR beam 2 shutter only. Cover the fold mirror labeled IR123A, and IR123B. Adjust pico7 motors labeled IR23 if necessary. «This is one mirror on the rosetta, better to use larger steps with the picomotors rather than manually adjusting it.
  3. Open IR beam 3 shutter only. Cover the fold mirror labeled IR23, and IR123A. Adjust pico7 motors labeled IR123B if necessary.
  4. Keep IR beam 3 shutter only. Cover the fold mirror labeled IR123A, and IR123B. Adjust pico7 motors labeled IRBC23 if necessary. «This is the 23 beam combiner, a flex mount which could be not so flexible after it was driven too far. This may require a manual move of the picomotor and pushing the flex part manually against the picomotor, to make sure that it is actually controlling the mirror tilt.
  5. Keep IR beam 3 shutter only. Cover the fold mirror labeled IR23, and IR123B. Adjust pico7 motors labeled IRBC123 if necessary.

The next part is to verify with the WL source, repeating the same steps, but this time using the CLIMB server and GUI and look at the spots in NIRO. Make sure that no covers are left on the fold mirrors. When looking at the spots with NIRO GUI tab: Pixel Area, when adjusting, you just watch only that spot which was left open in the laser procedure. See the diagram of spots in NIRO on the printed diagram.

Example of How to Recover the Alignment of IRBC23:

Diagnosing Problem: Follow the steps above using the green laser on the CLIMB table and the white light source with the pixel area of the NIRO detector. When looking at the light from Beam 3 only, light appeared on pixel 123A and 123B, but not on 23. Light from Beam 2 only appeared in pixel 23, but not in 123A and 123B. Comparing with the CLIMB layout diagram, this indicated a problem with IRBC23.

To recover IRBC23, use the green laser first

  1. Open only IR3.
  2. Block IR123A and IR123B fold mirrors with the business cards.
  3. Put onto the fold mirror labeled IR23 the round paper target (lying around the table nearby) to see how badly the beam splitter is misaligned. The laser beam does not have to be perfectly centered on that loose target. If it is way off, perhaps partially missing the fold mirror, then move the IRBC23 actuators by hand to roughly center on the fold mirror. At this point when you remove the paper target from the fold mirror, you should be able to see a green spot shining on the cold stop behind NIRO window. Then all that needs to be done is to get that spot into the hole in the middle of the cold stop. Make sure that the picomotors on IRBC23 are controlling the beam, in other words, the actuators are pressed against the flex mount.

After that you should be able to see all three WL spots in NIRO from Beam 2 and also from Beam 3. Use the pixel area of the detector and the alignment readouts from the CLIMB GTK to align the light into the correct pixels using the original 5 steps listed above.

TIPS

If moving IRBC23 using the pico7 gui does not change the alignment, then the flex mount is not touching the actuator. Push on the mount and then turn the knob by hand. Confirm that the picomotor can control the motion again.

If you have trouble figuring out whether the laser is going through the hole in the middle of the cold stop, you can place the cover on NIRO. Looking at Beam 3, compare the location of the spot coming from the fold mirrors IR123A, IR123B, and IR23. Move the misaligned optic (e.g., IRBC23 in the example above) until it overlaps with the other beams. This could bring the light close enough so that it appears on the pixel area of the detector. Then the remainder of the alignment can be done by aligning to the spots on the dectector using the 5 Steps listed above.

chara/climb_lab_alignment.txt · Last modified: 2020/07/16 23:34 by gail_stargazer