Using proton-induced ^3He to study He diffusion kinetics and rock thermal histories

We have investigated He release kinetics by step-heating of minerals in which we introduced artificial ^3He with a beam of ~150 MeV protons in a particle accelerator used primarily for cancer therapy. This process mimics cosmic-ray spallation, and produces He with a ^3He/^4He ratio of about unity. The induced helium is homogeneously distributed within the target crystals, and because it is emitted with few MeV energies, the ^3He should reside in sites indistinguishable from those of radiogenic ^4He.