Graphitization of Carbon Stripper Foils

Abstract

Procedures for increasing the lifetime of carbon stripper foils are described. Four to eight μg/cm² self supporting carbon foils were treated by two different methods in order to change their amorphous composition into a more crystalline structure. One method is the bombardment with electrons of energies up to 5 keV. In the second method both sides of the carbon foils are bombarded simultaneously with He⁺ ions with energies up to 2 keV.

Both procedures result in a prolongation of the lifetime of the carbon foils used as terminal strippers in the Munich tandem accelerator. Results for S^- — beams of 9.0 and 10.6 MeV energy and intensities up to 2.5 µA are reported.

The improvement in lifetime can be explained by the crystal structure of the foils, which was investigated using the spectral dependence of transmitted light.