Demonstrating the Effectiveness of a Cylindrical Top-Hat Electrostatic Analyzer in the Analysis of Ionized and Neutral Atoms in a Laboratory Ion Beam

Abstract

A new cylindrical top hat electrostatic analyzer (CTH-ESA) has been developed to study neutralatoms in a laboratory ion beam while simultaneously studying the energy distribution of ions. The CTH-ESA can divert ions from the particle beam while allowing the remaining neutrals to be largely undisturbed. SIMION simulation software was used to create a theoretical model which was then compared to a physical model built and tested at Princeton’s Space Physics Laboratory. The CTH-ESA was tested in conjunction with two absolute beam monitors (ABMs) which served as particle detectors. Due to time and manufacturing restrictions, only one ABM was used at a time, however, because the beam performance is consistent the data was unaffected by this restriction. The average energy resolution of the CTH-ESA was 4% which resulted in a precise description of the ion beam’s energy distribution at various energy levels. It was also found that the CTH-ESA was not able to fully remove ions from the neutral channel, however it is speculated that this is a result of ionized particles neutralizing before entering the instrument and masquerading as ionized particles. The results do demonstrate the effectiveness of an inversely polarized Helmholtz coil at pushing ions away from the beamline trajectory at high energies. Lastly, the neutral particle count rate as a function of beam energy was demonstrated thanks to a charge exchange cell at high beam energy. It is worth noting that neutral particles in all cases were not able to pass through the carbon foil mounted on the neutral ABM, resulting in a possible source of unaccounted noise in the readings; however, this could be accounted for with a particle detector better suited for studying neutral particles. Overall, the CTH-ESA is a great tool for beam studies of both ions and neutral laboratory-made particles.