This page is intended to summarize the properties of the optics that are in LRIS and provide notes as to the scratches, repair work, cleaning methods, and history of the individual components.

GRISMS

All grisms are made of Fused Silica, Corning 7980 gr A and are AR coated on the unruled surface by JLM optics. The ruled surface is a resin with unknown properties as of 1 Aug 2007.

Notes:
• 300 : A cleaning test was performed on this grating. Opticoat was poured on a small section. After 1 day, the test piece would not pull away from the grism as well as it worked on the filters. After two days, the opticoat peeled from the grating ruled surface, but not as easily as the filters.
• 400 :
• 600 : There is a 3-4 mm gouge at one edge of the unruled surface. The gouge is out of the FOV. There is a scrape on the frame next to the gouge. The gouge was created when the red side I band filter broke and fell into the grism Carousel. Using polarizers, Tim Saloga observed stressing in glass that start from the gouge. Tim Saloga says that the stresses should not alter optical properties of glass. The gouge does not need to be fixed.
• 1200: Heaviest grism. Particular rotator positions while on the deck cause the grism transport to fail because it is not strong enough to lift the grism.

Cleaning Procedure:

1. Remove grisms from carousel
2. Clean the grisms by blowing nitrogen over the surface.
3. Complete a scratch/imperfection map of the grisms
4. Reinstall grisms in carousel

Cleaning Notes: We decided to follow the above procedure based on the following information:

• Caltech experts (Keith M. Rich G. Judy C.) suggest blowing off particles
• Lick optics expert, Dave Hillyard, suggests that "opticoat" should be safe to use on grisms.
• Sarah Curet at Richardson Labs recommended blowing dry nitrogen over the surface to clean it, and use a very low pressure flow. She sent a technical note regarding gratings, but says that this applies to grisms as well. I asked about using products like opticoat, and I got the impression that Sarah was unfamiliar with the product.
• Opticoat experts indicate that their product damages some grism surfaces depending on the chemical composition of the ruled surface.
• We know that grism surfaces have a resin on them, but we do not know the composition of the resin.
• Although the opticoat peeled the way we think it should from the 300 line grism, we may have damaged the microscopic groove profile.

Filters->Red Side

Notes:

Additional notes:
• V filter AR coating was damaged by turning the V filter over before the opticoat cleaning product had solidified. The V filter on the blue side, which is made from identical glass but perhaps a different AR coating, was not damaged in the cleaning process.
• Plater's tape is used to prevent the filters from rattling directly against the Al frame. The I filter may have broke when due to the direct metal-filter contact.
• Theory as to why the filters were chipped and the I filter broke -> There was a 6.? earthquake November 2006. Following the earthquake, all the optics were inspected. We did not, however, take them out of their holders and inspect the edges. We believe that during the quake, the filter was chipped along the edge. The filters were held in direct contact with the Al frame, and so direct metal contact may have contributed to the chipping. After the I filter broke, we removed all of our filters from their frames and checked edges. Other filters had chips.

Cleaning/Repair procedure

1. Remove the filters from the Juke box if necessary (some are stored in the filter cases).
2. Place filters flat on table protecting with Kim-wipes
3. Poor edges of opticoat surface trying not to opticoat any of the filter frame which would cause the opticoat to leak around the filter edge.
4. Opticoat the surface by pouring the opticoat so that it fills in between the defined edges.
5. Wait 1.5 to 2 days.
6. lift corner of opticoat trying not to scratch optic surface
7. peel opticoat from optical surface. Peel the opticoat by pulling it back over it self at a very acute angle. Do not peel by pulling perpendicular to the coated surface.
8. Coat the other side if necessary.
9. Examine filter for cracks along the filter edges and on the surface.
10. Repair any cracks by grinding them away.
11. Inspect plater's tape, and retape the edges of the filters if necessary. If a filter is not taped, along the edge, then it should be unless noted above (see V filter).
12. Using polarizers, inspect the glass for stresses. If stresses are detected, contact an optical technician for assistance.
13. Update and file scratch maps of optics.
14. Re-install the filters following normal installation procedures.

All Broad and Blocking filters were inspected, and if necessary, cleaned and repaired in July 2007. Narrow band filters were not cleaned in July 2007.

Lessons learned:

• Do not move the optic while the opticoat is solidifying. The V filter on the red side was flipped over to inspect the other side before the opticoat was set and the result was a damaged AR coating.
• Gold Coating are too soft to use with Opticoat. The 600/1000 line grating gold coating was damaged while following normal opticoat cleaning procedures.
• It is unknown whether opticoat is safe for grisms.
• know the composition of the coatings.

Filters->Blue Side

Notes

All filters were visually inspected in July 2007. U, B, and G were not removed from their frames.

Name	Work Completed/Notes
U	During inspection in July 2007, filter was not removed from frame. Chip visible at the edge of a frame and was noted in Nov. 2006 following earthquake inspections.
B	Two nicks ground out in
V	Loose in frame. installed side screws 6-32 1/4, 5/8, and 1/2 which secure filter holder to the filter cell in July 2007. They were missing previous to this. Bob Webber at Caltech informed MK that they should be installed. Has a metal edge to the filter Filter cell opening was enlarged to accommodate the filter July 2007, Niel Felton modified the V filter frame so that the filter cell retainer bars could be secured in place using 4-40 screws instead of double sticky tape. The drawings have not been modified to reflect either the enlarged filter cell opening done previous to this work, or the mods made by Niel F.
G
SP580	Loose in frame. installed side screws 6-32 1/4, 5/8, and 1/2 which secure filter holder to the filter cell in July 2007. They were missing previous to this. Bob Webber at Caltech informed MK that they should be installed. Chipped in three corners and in several places along the edge. The chips were ground away in July 2007.

Dichroics

Gratings