AVS 47th International Symposium
    Thin Films Thursday Sessions
       Session TF-ThM

Paper TF-ThM6
A Near-grazing-incidence, Antireflective Coating for 121.6 nm for a Mars-bound Neutral Particle Detector.

Thursday, October 5, 2000, 10:00 am, Room 203

Session: Optical Films
Presenter: S. Olson, Brigham Young University
Authors: S. Olson, Brigham Young University
D.D. Allred, Brigham Young University
M.B. Squires, Brigham Young University
D. Markos, Brigham Young University
C.E. Mills, Brigham Young University
R.T. Turley, Brigham Young University
Correspondent: Click to Email
A neutral particle detector is being planned to orbit Mars as part of the ASPERA mission. It is designed to detect and classify atoms in the exosphere of Mars by their identity and velocity using a time-of-flight mass spectrometer. An electron released on collision with the first surface in the spectrometer (the start surface) initiates a start pulse for the spectrometer. The most significant source of noise is thought to be UV photons- particularly hydrogen Lyman alpha (121.6 nm), which are capable of generating false start and stop pulses. We have design using a genetic algorithm and fabricated a coating for the START surface which absorbs UV photons at 121.6 nm thus preventing their reaching the stop surface. The particular optical challenge was the fact that the particles and incident light arrives at an angle of 10 to 20 degrees from grazing. We will discuss the use of a genetic algorithm in designing the coating, its fabrication, AFM measurements of sample and at-wavelength measurements of their reflectivity.