Novel Nuclear Reactions for Medical and Environmental Applications

Three novel accelerator-based reactions relevant to nuclear applications have been studied, one light-ion reaction, and two heavy-ion reactions. The two heavy-ion reactions share a methodology and motivation for investigating alternative approaches to light-ion isotope production for nuclear medicine. The light-ion reaction studied here is done with an environmental monitoring motivation using particle-induced gamma-ray emission (PIGE) spectroscopy that has been improved with a normalization methodology.

PIGE is used for the rapid analysis of ex vacuo samples. An indirect beam current measurement technique has been developed using an ion beam reaction on atmospheric argon, the only sample independent atmospheric component with sufficient abundance (~1%) that produces abundant gamma rays with low-energy proton beams. The ⁴⁰Ar(p,nγ)⁴⁰K reaction has been studied here, and the characteristic 770 keV gamma ray is observed to serve as a reliable monitor for proton flux. This method allows a real-time calibration of beam intensity on target to measured upstream currents for ion beam analysis at beam energies above 3.5 MeV.

Light-ion production of nuclear medicine isotopes is the standard methodology, but some highly desired proton-rich isotopes have difficult production hurdles including yield, purity, cost, and availability. Two heavy-ion approaches have been investigated for medically useful isotopes, ¹⁴⁹Tb and ^44mSc. The radionuclide ¹⁴⁹Tb (t_1/2= 4.1 h) is a potential theranostic isotope which can simultaneously be used for targeted-alpha-particle therapy and positron-emission tomography. Feasibility experiments were performed to test a near-symmetric heavy-ion reaction of ⁶³Cu bombardment on monoisotopic ⁸⁹Y. The indirect reaction was studied to avoid isomer production. There is modest agreement with the statistical model code, PACE4, for fusion-evaporation products. A near-symmetric fission yield is also observed.

Using a complimentary approach and the experimental observations from the terbium project, ^44mSc (58.6 h) was investigated from a less symmetrical ³⁵Cl bombardment of natural Boron, ^natB. The reverse kinematics reaction limited the number of open channels and reaction products. Only fusion-evaporation products were observed from boron and some contaminant oxygen. In both these heavy-ion approaches, offline gamma spectroscopy was used to identify the residuals and quantify the end of beam activities. A summary of what implications these heavy-ion experiments hold for the future development of novel radioisotopes is presented in the concluding chapter.