  Previous measurements have shown large cross sections for the
11B(p,$\alpha$)8Be reaction and K-shell ionization of boron from H+ ions. Past
publications have shown that this reaction will likely increase the efficacy of
proton therapy. This study investigates the size of boron particles for optimum
treatment enhancement in proton therapy. Simulations of protons passing through
varying sized boron particles were developed to compare energy outputs for
alpha particles and low energy electrons. The results for the boron particle
radius that produced the largest radiation output are presented in graphical
form in this paper. The radius that produced the largest Auger output was
determined to be 1.3 nm. The results indicate that maximum dose enhancement
will depend on the limiting factors of the biological system in regards to the
appropriately sized particle. Studying different reactions that may be applied
in hadron therapies allows researchers and physicians to target tumor sites
more selectively.
