Design of a Beam Profile Monitor for Measurement of Direct Current Particle Beams at the Reactor Materials Testing Laboratory
Abstract
Queen’s University’s Reactor Materials Testing Laboratory operates a direct current linear particle accelerator to conduct irradiation experiments for the research of nuclear materials. The accelerator is currently capable of accelerating hydrogen and helium nuclei (protons and alpha particles, respectively) to a maximum energy of 8 MeV at a maximum current of 40 microamps. To ensure the delivery of consistent and high-uniformity ion beams, beam profile monitors are needed. The Scanning Wire Ion Profile Reconstructor is a design for a beam profile monitor that can independently measure and output the ion beam’s intensity in two spatial dimensions in an accessible and useful format. To achieve these goals, the instrument makes use of a mechanical subsystem, an electrical subsystem, LabVIEW control software, and Python computerized tomography software. The design of the instrument revolves around conducting wires that are held in electrical isolation within the accelerator beamline. The positively charged accelerated particles impart their charge directly onto the wires as an electrical current as they are actuated in and out of the ion beam. This current is directly proportional to the beam current and is conditioned with operational amplifiers for digital acquisition before post-processing. Once a measurement is made, it is processed to a graphical output for easy use by the accelerator operator in aligning and adjusting the beam. A prototype of the instrument has been tested in the beam at various conditions on three separate occasions. Results indicate that the instrument performs as theoretically predicted, and comprise measurements of the beam profile, depicting its intensity and position in space. Improvements are continually being made to all aspects of the instrument by iteration, informed by information gathered through ongoing testing. Semi-permanent installation of the instrument alongside other beam profile monitors is underway as part of a broader effort to improve the laboratory’s diagnostic equipment.