Bochum 2002 – scientific programme

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P: Plasmaphysik

P 22: Poster: Magnetische Fusion, Plasmadiagnostik, Dichte Plasmen

P 22.3: Poster

Tuesday, March 19, 2002, 17:40–18:40, HZO Foyer

Simon short circuit effect in ECRIS — •D. Meyer¹, A. G. Drentje², A. Nadzeyka¹, U.T. Wolters¹, and K. Wiesemann¹ — ¹Ruhr-Universität Bochum — ²Kernfysisch Versneller Instituut, Groningen

In many ECR ion sources it has been found that negatively biasing the end plate improves the charge state distribution that means the confinement of the plasma. By biasing the overall balance between radial ion losses and axial electron losses will change, resulting in a different diffusional mode of the entire plasma. Hence, the plasma potential and the average charge state of ions in the plasma are significantly influenced. In metallic vessels in a magnetic field the usual approach of ambipolar diffusion does not hold. The ion flux dominates radial diffusion while the electron flux dominates axial losses. This is possible due to compensating wall currents in the plasma chamber wall (No-dqSimon short circuitNo-dq). By biasing the end plates the wall currents are intercepted. A similar effect takes place, if the plasma chamber is coated with electrically insulating materials. We examine the short circuit current as a measure for the diffusion mode and calculate approximately its influence on plasma potential and average ion charge state in the plasma.