N-15 HYDROGEN DEPTH PROFILING MEASUREMENTS OF CANDIDATE SUPERCONDUCTING SUPERCOLLIDER BEAM PIPE MATERIALS

Photodesorption of gas, particularly H-2, by synchrotron radiation in the proposed next generation of superconducting proton colliders is a critical issue confronting the design of the vacuum system. As an initial step in understanding the source of this hydrogen, we report measurements of the surface and bulk concentrations of hydrogen in candidate beam tube materials and compare the surface concentration to the amount of H-2 desorbed in photodesorption experiments. Hydrogen profiling measurements using the 6.4 MeV H(N-15,alpha gamma)C-12 resonant nuclear reaction were performed on representative vacuum system materials including stainless steel, stainless steel electroplated with copper, and high purity bulk copper. All of the Cu samples examined had a hydrogen-rich surface layer <100 Angstrom thick containing 2-5X10(16) H atoms/cm(2) and a bulk concentration of approximately 1% atomic hydrogen. (C) 1995 American Vacuum Society.