LASER-HEATED WIRE TIP AS HIGH-CURRENT DENSITY EMITTER

Electron beams with high current density are of great interest in Elec tron Beam Ion Sources (EBIS and EBIT). The conventional way to yield c urrent densities in the 10(3) A/cm(2) range uses high beam compression in an increasing magnetic field. Temperature-and-field emission (TF-e mission) first theoretically treated by Dolan and Dyke [1, Phys. Rev. 95, 327 (1954)], describes the electron emission from small heated met al tips. Here, the emission current densities are by orders of magnitu de higher than in LaB6-cathodes depending on the dimension and work fu nction of the tip, temperature and electric field on the surface of th e tip. A project was started to provide high electron beam current den sities by TF-emission. The present cathode is the tip of a 100 mu m ta ntalum wire. The tip is heated by a CO2 laser. The anode is a paraboli c copper mirror that focuses the laser beam to the tip. The present pa per presents first measurements and results.