SimIon optimization for ion collection in [formula omitted]Cs sterile neutrino search

Abstract

Reaction Ion Microscopes (RIMs) are axial-field electrostatic spectrometers extensively used in atomic physics to study few-body reactions. The high resolution and 4π solid angle acceptance achievable with these devices have made them essential tools for studies of atomic physics. The sources of reacting particles in such studies are often spatially extended (Magneto Optical Traps (MOT) or supersonic gas jets), requiring the spectrometers to focus in both the longitudinal and transverse directions without loss of resolution. The necessary design conditions for combining longitudinal (Wiley–McLaren) and transverse focusing have been described in the literature and employed by a number of chemical physics groups. However, a unified and systematic framework for optimizing the several competing requirements for such spectrometers has not been described.The present paper describes techniques developed to apply the MOTRIMs technique to an elementary particle physics experiment. The HUNTER experiment (Heavy Unseen Neutrinos from Total Energy–momentum Reconstruction) is a search for sterile neutrinos with masses in the range 20–280 keV/c2 produced in electron-capture decays of radioactive nuclei, using event-by-event missing-mass reconstruction.Methods developed to optimize HUNTER RIMs spectrometer design are reported in this paper. These methods are generally applicable to the design of high performance RIM systems.