Development and Investigation of a Modification to Extend the Dynamic Range of Electrostatic Analyzers

Abstract Plasma populations within the solar system are distributed over a substantial range of densities, kinetic temperatures, and bulk velocities, from the solar wind to Earth's ionosphere. Measuring the full range of plasma conditions for some of these populations is difficult for current top‐hat electrostatic analyzers, let alone for multiple populations. A modification to the standard top‐hat electrostatic analyzer (ESA) design is developed and explored that extends the differential energy flux dynamic range of the instrument. The modification uses a secondary electrode placed on the outer portion of the analyzer optics to electrically control and vary the instrument's geometric factor (GF) by up to three orders of magnitude. The design space of the modification, such as its size and position within the analyzer channel, is investigated through ion optics simulations. As the GF is reduced, the energy and angular passbands of the analyzer narrow. The modification's impact on other instrument parameters and its advantages over other variable geometric factor systems (VGFS) are discussed. A prototype ESA with the presented modification was developed and tested. Laboratory results are consistent with the behavior of the modification from simulation predictions, verify the extension of the analyzer's dynamic range, and show the feasibility of the modification for future instrument designs.