Experiments with a prototype titanium hot cavity surface ionization source intended for electromagnetic separation of radioactive samarium and other lanthanide elements.

This paper reports experimental results of a prototype titanium surface ionization source. For the first time, a lanthanide ion beam has been produced with a surface ionizer composed completely of titanium metal. Titanium does not readily activate with neutron irradiation. This offers the potential for inserting an ion source made of titanium directly into a reactor with a pre-loaded non-radioactive lanthanide target. This seamlessly integrates target irradiation with isotope separation, eliminating post irradiation sample manipulation. Samarium ion beam currents up to 960 nA have been produced in an off-line test bench equipped with rudimentary beam optics. This is a crucial step toward the development of an ionization source adopted for the electromagnetic isotope separator (EMIS) facility, which has been designed for high throughput separations of radioactive 153Sm and other lanthanides of interest in the field of nuclear medicine. The ion current and important factors affecting the performance of the ion source, such as the ionizer temperature and thermal gradient, are discussed. The experimental results are presented together with a discussion of future modifications to optimize the overall surface ionization source performance.

Characterization of the neutron flux during production of 18F at a medical cyclotron and evaluation of the incidental neutron spectrum for neutron damage studies.

The fast neutron spectrum was measured in an irradiation position adjacent to two 18F (fluorine-18) production targets at a medical cyclotron. The neutron spectrum was modeled using MCNP6 and experimentally determined using activation foils. A three-group neutron spectrum was determined using an over-determined least squares fitting method. The MCNP6 model results and measurements of the activation foils were used as input to unfold the neutron spectrum using the STAYSL PNNL code. The neutron spectrum adjacent to the 18F production target was evaluated for use in incidental experiments to evaluate neutron-induced radiolysis of polyurethane and radiation hardness testing of electronics. The fast neutron flux near the 18F target between the energies of 0.4 - 16.5 MeV was 1.8 - 3.0x109 n cm-2s-1. The neutron dose rate in polyurethane at the irradiation position was 2.8 cGy s-1- 5.8 cGys-1. The 1 MeV equivalent neutron flux was 2.4x109 n cm-2s-1 - 4.0x109 n cm-2s-1.