Accelerator System for Producing Two-Component BEAMS for Studies of Interactive Surface Effects

摘要

For studies of interactive surface effects caused by the simultaneous bombardment of targets by both chemically active and inactive ion species (e.g., D exp + and He exp + , respectively) a two beam component accelerator facility was placed in operation. One component, consisting of light ions (e.g., H, D, He) is accelerated by a 2-MV Van de Graaff accelerator which provides a mass analyzed and focussed beam for the energy range from approximately 100-keV to 2-MeV (for singly charged ions). The other component is a beam of light ions in the energy range from approximately 10-keV to 100-keV. This is furnished by a 100-kV dc accelerator system which provides a mass analyzed focussed beam. This beam is guided into the beam line of the Van de Graaff accelerator electrostatically, and with the aid of beam steerers it is made to be co-axial with the Van de Graaff generated beam. The angle of incidence becomes hereby a free parameter for the interaction of the mixed beams with a surface. For each beam component, current densities of 650 mu A cm exp -2 on target can readily be obtained. In order to reduce carbon contamination of the irradiated targets significantly, stainless steel beam lines have been used together with a combination of turbomolecular pumps and ion-sublimation pumps.A total pressure of 2 to 3 x 10 exp -8 torr in the beam lines and of 2 x 10 exp -9 torr in the target chamber can be obtained readily. Experimental results on the surface damage of Ni bombarded simultaneously with He exp + and D exp + ions are presented. The importance of such studies of interactive surface effects for the controlled thermonuclear fusion program are discussed. (ERA citation 03:019599)