Piezoelectric transformer plasma ion source characterization for neutron production

Abstract

Neutron sources have applications in fields where the elemental composition of a material needs to be determined while retaining the integrity of the initial sample. While many different neutron sources are currently available, they face drawbacks such as size and radioactivity. The piezoelectric transformer plasma source (PTPS) has been developed as a compact source of ions. The PTPS consists of a 10 mm diameter by 2 mm thick lithium niobate (LiNbO3) disk which uses the piezoelectric effect to generate appropriate electric fields for plasma generation. The PTPS was characterized using multiple methods to determine the characteristics of the plasma being formed with consideration of possibilities for increased output. An ion current experiment was used to determine the impact of extraction voltage, input voltage to the PTPS, internal pressure of the plasma generating chamber, ionizing gas, and hollow anode size on the ion current produced by the PTPS and to demonstrate the scalability of the PTPS. The PTPS was integrated into a neutron generating system to show that the PTPS was capable of producing ion currents sufficient for neutron generation. Finally, the electron temperature and density of the plasma generated in the PTPS was measured through the use of a triple Langmuir probe system. The experiments showed that the PTPS is capable of producing ion currents in the 10 μA range with plasma electron temperature and densities in the 4 eV and 1015 m-3 range which, and when operated as a source of deuterium ions (and coupled with a deuterated target placed at a high voltage) was capable of producing neutron counts above background through the deuterium-deuterium (D-D) reaction.