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O.H.W. Siegmund Experimental Astrophysics Group,

Window Transmission and Reflection Considerations for LAPD Detectors. O.H.W. Siegmund Experimental Astrophysics Group, Space Sciences Laboratory, U. California at Berkeley. GALEX M31. Window/Photocathode Configuration. Windows for large area devices need to perform several functions

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O.H.W. Siegmund Experimental Astrophysics Group,

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  1. Window Transmission and Reflection Considerations for LAPD Detectors O.H.W. Siegmund Experimental Astrophysics Group, Space Sciences Laboratory, U. California at Berkeley GALEX M31

  2. Window/Photocathode Configuration • Windows for large area devices need to perform several functions • Support vacuum • Have high transmittance/ low reflection in the required bandpass • Be a good substrate for photocathodes AR coating ITO coating

  3. Standard Windows Acceptable cutoff range

  4. Standard Night Vision Windows A. Smith NIM 2002

  5. Borofloat 33 General Parameters Composition Refractive index @400nm Borofloat 33 1.47 Air ~1.0 Water ~1.32

  6. Transmittance and Reflectance of Borofloat 33 Standard AR coating is bad for LAPD - need re-optimization or don’t use AR coating?? Transmittance is typical for borosilicate glasses

  7. Graded Film, Porous Borosilicate, AR Minot, JOSA 1977

  8. Anti-Reflectance Coatings Si

  9. Anti-Reflectance Coatings Sample AR optimization for NaI(Tl) scintillator

  10. Conductive Layer Properties for Windows ITO is a good choice for the conductive underlayer Braem, NIMA 2003

  11. Photocathode Reflectance GaAs Red cathode S20 photocathodes Blue cathode

  12. Window Treatment Summary Prospects for large windows - borofloat 33 looks good AR coatings can be very important, but may be unnecessary? Photocathode reflectivity is potentially a big issue Have to have a conductive underlayer, ITO good candidate

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