Measurement of the density of the neon atoms in the 3P2 and 3P1 state by means of optical fluorescence in a plasma produced by a proton beam

A beam of 20 MeV protons has been used as a well defined excitation source to produce metastable 3P2 and resonant 3P1 states of neon. The proton beam passes along the axis of a 300 mm long, 130 mm internal diameter metallic cylindrical cell, in which the neon gas density can be varied from 3x1021 to 6x1024 atoms/m3. Perpendicular to the axis a 100 mW beam (0.5 mm ) of a dye laser passes through the center of the cell. The laser has been tuned to 588.2 nm or 603.0 mm to excite 3P2 respectively 3P1 atoms. A portion of the fluorescence light from a small section (1mm), emitted perpendicular to the plane of laser and proton beam, has been synchronously detected by a lock in amplifier. The radial dependence of the density of the excited atoms was determined by scanning along the path of the laser beam. A numerical model describes the excited atom density in relation to the radius and the neon gas density. (Auth.)