Mirror prototype test plan

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Testing of existing mirror box

After the mirror box removal, the following tests should be performed to study the damage to the mirrors

  • Water/food dye leak check
    • Initial spot check with food dye for clear leak sources: nothing observed
    • Submerge full mirror piece in water tank with fluorescent dyed water to identify possible leak sources: done
  • Relative reflectivity mirror measurement
    • Compare reflectivity of know sample mirror and those from mirror box similar to [1]
    • Further studies could be done in detector group's Big Blue Box, etc.

Planned prototypes

Small samples ~(2x2 in) should be made for testing under water and reflectivity measurements. Below are the suggested fabrication steps to produce test pieces. For reproducibility we could make 3 of each sample. All these should be tested with standard glass pieces prior to using borosilicate and UVE mirror.

Supplies needed:

  • Clear DP270 and applicators
  • Epotek301-2 and 301-2FL epoxy (ships on 12/8)
  • Hostility slury polish (ordered by Mark)
  • Wipe-on screen protector
  • Glass/mirror pieces (cut at Danny's glass)
    • 20 pieces of 2x2 in standard glass samples for testing epoxy application processes
    • 20 pieces of 2x2 in borosilicate glass for prototypes
    • 23 pieces of 2x2 in UVE mirrors for prototypes
  • Bell jar from detector group
  • "Bag" for pumping on glass/mirror sandwich (Keith re-assemble in Hall)

Wider epoxy seal

Follow similar procedure as existing mirror box, but use wider strip to provide better water seal

  • Borosilicate + UVE mirror with DP270 1-2 cm wide strip around edge


  • Some mirrors were successfully sealed in existing mirror box, what is unique about them?
  • Concern about how we get such a thick ring of epoxy around the edge with the previous "wicking" approach of putting a bead on the outside and let it seep between the two layers. Could bevel the edge of the protective glass to provide larger sealing surface to apply epoxy.
  • Results from the dye test show that a the corners are particularly likely to fail with small strip of epoxy

Full epoxy sandwich

Setup small "bag" with blue film to sandwich protective glass against mirror surface using pump. Keith previously setup something like this in the Hall last year

  • Borosilicate + UVE mirror sandwich with DP270 entirely between surfaces
  • Borosilicate + UVE mirror with Epotek301-2 entirely between surfaces

Poured epoxy layer

Use bell jar from detector group to pump out bubbles

  • UVE mirror with Epotek301-2 poured on and cured over ~days under bell jar to investigate procedure
  • UVE mirror with Epotek301-2FL poured on and cured over ~days under bell jar to investigate procedure


  • Requires level surface for even curing of "flat" coating of Epotek
  • Requires clean room or to cure without contamination
  • Consider solutions for "dam" around mirror to keep fixed thickness of epoxy
  • Could we consider a spray-on application if the epoxy has low enough viscosity?

Molded epoxy layer

Bobby and Keith made some silicone molds that could be used to maintain a thin epoxy layer on the mirror surface [2]

  • UVE mirror with Epotek301-2 poured on and cured over ~days under bell jar to investigate procedure


  • This requires level surface for even curing of "flat" coating of Epotek and custom sized mold

Screen protector (liquid glass)

Stephanie suggested an off the shelf wipe-on screen protector.

  • UVE mirror with screen protector applied

Rear surface mirror

Keith identified a possible vendor for high reflectivity rear-surface mirror of large size

  • Considering 5 mm thickness, will need samples to measure reflectivity
  • Seal rear surface of mirror with 3M strips and silicone(?) against aluminum strongback

Test plan

After prototypes are produced (by early December), make the following tests:

  1. measure reflectivity relative to control UVE mirror
  2. for one control sample of each prototype, measure the wavelength dependence in the Big Blue Box
  3. use laser to evaluate impact of any non-uniformity of epoxy layers (speckling)
  4. place one sample in water bath and one sample under UV lamp to test stability
  5. each week, take samples out of water/lamp setups and measure relative reflectivity

Goal: decide on full scale prototypes to produce by the end of 2020 for testing in December/January