The use and Production of Suprathermal Atomic Beams for the Diagnostics of the Scrape Off Layer of Tokamaks

An experiment is described where beams with suitable parameters and elements were produced by ablating thin films of Zr (1000, 3000, 6000 and 10000 Å) and Li + Al (500 A Li, 800 Å Al) with the use of Q-switched ruby laser pulses (total energy density: 12, 5 J/cm²). The energy and density distribution of the evaporated atoms was measured by laser-induced fluorescence. Concerning the particle energy, values of several 10 eV were found with a variation dependent on the film thickness. The beam itself had a half width of about 14° with peak neutral densities between 10¹⁰ and 10¹² cm⁻³. In the presence of a hydrogen atmosphere of 10⁻⁴ mbar the Zr beam was attenuated by a factor of 2, whereas the density in the Li beam decreased by nearly one order of magnitude.