Velocity Map Imaging with No Spherical Aberrations

TL;DR

This paper derives an analytical method for velocity map imaging that eliminates spherical aberrations, enabling high-resolution ion and electron kinetic energy measurements over large volumes.

Contribution

It introduces a new analytical approach for VMI without spherical aberrations, improving resolution and acceptance volume in ion optical systems.

Findings

SIMION simulations confirm focusing of electrons over 8 cm volume to 0.1 mm spot

The formalism applies to position imaging and combined position-velocity imaging

Implementation in the Cryogenic storage ring enhances VMI capabilities

Abstract

Velocity map imaging (VMI) is a powerful technique that allows to infer the kinetic energy of ions or electrons that are produced from a large volume in space with good resolution. The size of the acceptance volume is determined by the spherical aberrations of the ion optical system. Here we present an analytical derivation for velocity map imaging with no spherical aberrations. We will discuss a particular example for the implementation of the technique that allows using the reaction microscope recently installed in the Cryogenic storage ring (CSR) in a VMI mode. SIMION simulations confirm that a beam of electrons produced almost over the entire volume of the source region, with width of 8 cm, can be focused to a spot of 0.1 mm on the detector. The use of the same formalism for position imaging, as well as an option of position imaging in one axis and velocity map imaging in a different axis, are also discussed.