High energy electron beams shaped with applied magnetic fields could provide a competitive and cost‐effective alternative to proton and heavy‐ion radiotherapy

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135099/1/mp0453.pd

Quantifying the diffusion kinetics and spatial distributions of radiogenic ^4He in minerals containing proton-induced ^3He

Apatite, titanite and olivine samples were bombarded with a ~ 150 MeV proton beam to produce ~ 10^8 atoms/mg of spallation ^3He. High-precision stepped-heating experiments were then performed in which the artificial ^3He and, for apatite and titanite, the natural radiogenic ^4He were measured to characterize the diffusive behavior of each isotope. Helium-3 diffusion coefficients are in excellent agreement with concurrently and/or previously determined He diffusion coefficients for each mineral. Our results indicate that proton-induced ^3He is uniformly distributed and that radiation damage associated with a proton fluence of ~ 5 x 10^(14) protons/cm^2 does not cause noticeable changes in ^4He diffusion behavior in at least apatite and titanite. Proton-induced ^3He can therefore be used to establish He diffusion coefficients in minerals with insufficient natural helium for analysis or those in which the natural ^4He distribution is inhomogeneous. In addition,step-heating ^4He/^3He analysis of a mineral with a uniform synthetic ^3He concentration provides a means by which a natural ^4He distribution can be determined