Stacked-Ring Ion Guide for Cooling and Bunching Rare Isotopes

TL;DR

This paper introduces a novel stacked-ring ion guide design as an alternative to traditional RFQ systems for cooling and bunching rare isotopes, aiming to improve ion transmission and focusing.

Contribution

The paper presents a new stacked-ring ion guide with optimized parameters for enhanced ion cooling, bunching, and transmission, using analytical and simulation methods.

Findings

High ion transmission efficiency demonstrated

Produces well-focused ion bunches

Optimized design parameters improve performance

Abstract

In modern rare isotope facilities, ion cooling and bunching lies at the heart of the ion transfer along a low-energy beam line that consists of several differential pumping stages. We present a conceptual design of an ion guide as an alternative to the conventional linear Radio-Frequency Quadrupole (RFQ) for cooling and bunching rare isotopes. The ion guide is composed of stacked ring electrodes of varying apertures, to which a confining RF potential following a rectangular waveform is applied. The thicknesses of the rings and the gaps in between are varied accordingly to maximize the confining volume and to reduce ion losses. Ion transport within the ion guide is facilitated by a lower-frequency wave traveling on top of the higher-frequency confining field. The former is induced by locally adjusting the duty cycle of the rectangular waveform of the confining potential. Design parameters are first calculated by analytical studies and then optimized by ion trajectory simulations with SIMION. The results show that the ion guide enables high ion transmission and produces well focused ion bunches. It will be used in the NEXT project, an experimental study of atomic masses of Neutron-rich EXotic nuclei produced in multi-nucleon Transfer reactions.