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

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

Formation of F

Formation conditions, optical nonlinear properties and applications of F2− color centers in LiF monocrystals are investigated. The efficiency of F2− centers generation depending of irradiation conditions and content of OH− impurities of the LiF monocrystal are also presented. Thermal stability of the centers generated by electron irradiation was studied. It was measured the variation of absorption factor of the LiF: F2− crystal in the −40 °C to 60 °C temperature range. The LiF: F2− crystals obtained by an efficient method of irradiation with electrons generated by a linear accelerator were employed in Q-switching a Nd: YAG laser cavity with output energies of 18 mJ and fluctuations less than 5% in the −40 °C to 60 °C temperature range