Metal-dielectric structures for high charge state ion production in ECR plasma.

Schaechter L.1), Dobrescu S.1), Badescu-Singureanu A.I.1), Stiebing K.2) and Baltateanu N.3)
1) National Institute for Physics and Nuclear Engineering, Bucharest, Romania
2) Institut fuer Kernphysik der J. W. Goethe Universitaet, Frankfurt/Main, Germany
3) National Institute for Laser, Plasma and Radiation Physics, Bucharest, Romania

Metal-dielectric (MD) structures of pure (99.999%) aluminum foils were previously studied [1, 2] in the National Institute for Physics and Nuclear Engineering (NIPNE), Bucharest, Romania showing high secondary electron emission properties. Consequently, 26 mm diameter disks of such structures (Al-Al2O3) were tested in the ECR ion source of the Institut fuer Kernphysik (IKF) der J. W. Goethe Universitat, Frankfurt/Main, Germany, allowing to demonstrate their ability to significantly increase the ECRIS performances in what concerns the production of high charge state ions [3].

New experiments carried on in Bucharest on a special facility [2] stressed out the possibility to develop high emissive MD structures starting from lower purity (99%) aluminum foils. This result allowed us to make a special cylinder of 1 mm wall thickness electrolytically treated so that only the inner face had a MD structure layer while the external surface remained metallic. Such a cylinder introduced in the plasma chamber of an ECR ion source provides a high rate of secondary electrons that enhance the ECR plasma electron density while its metallic external surface provides a good electric and thermal contact with the plasma chamber.

The tests performed with such a MD aluminum cylinder in the IKF 14 GHz ECR ion source, successfully demonstrated the possibility to shift the ECRIS output toward very high charge states (Ar16+) due to the strong secondary electron emission of the MD inner surface of the cylinder.

References 1. L. Schaechter, Al.I. Badescu-Singureanu, S. Dobrescu and N. Baltateanu, Rom. Journ. Phys. 41, 333 (1996).
2. L. Schaechter, S. Dobrescu and Al.I. Badescu-Singureanu, Rev. Sci. Instrum. 69, 706 (1998).
3. L. Schaechter, K. E. Stiebing, S. Dobrescu, Al. I. Badescu - Singureanu, L. Schmidt, O. Hohn and S. Runkel, Rev. Sci. Instrum. 70, 1367 (1999).

Presenting Author : Schaechter L.
Presentation : Poster
Tuesday Poster Session at 16:00