Beam divergence and emittance of the neutral injector rf-plasma source RIG 10

One of the main problems in fusion torus-machines is the heating of the hydrogen plasma up to the temperature of thermonuclear burn. The effects leading to beam broadening were determined earlier. Beam divergence and emittance are discussed in this paper. The experimental set-up is presented. A typical computer plott of an emittance-diagram is given. In this special case (discharge power 1.3 kW, beam voltage 12 kW) emittance is 263 mm x mrad. In order to determine the minimum beam divergence, beam profiles at different operational conditions were registered. Optimum working conditions are between -250 V and -500 V. For further experiments a discharge pressure of 10 μbar (1 Pa) was chosen. The minimum divergence angle was found by asymptotic approach to be 1.1 deg. In this case the beam voltage and the rf-discharge power are proportional. (author)