PIC MC SIMULATION OF A STRONGLY ASYMMETRIC LOW-PRESSURE RF DISCHARGE

A PIC/MC simulation is performed on a cylindrical low-pressure gas discharge between two coaxial electrodes in an axial magnetic field. This case study employs an asymmetry ratio of 1:7 between inner and outer electrodes. It is based on natural mass argon gas with experimentally given cross sections for elastic, excitation and ionization electron collisions, as well as elastic and charge exchange ion collisions. The simulation shows that ionization occurs mostly at the inner sheath edge. Negative space charge regions build up in front of the momentary anode sheath. These lower the plasma potential with respect to the electrode and induce electron leakage currents to the anode. The ionization degree is 3 x 10(-4) , and 10% of the dissipated power goes into ionization in this particular case. The improvement of these features for the design of an ion source is discussed.