Abstract

Electrostatic storage rings operate at very low energies in the keV range and have proven to be invaluable tools for atomic and molecular physics. Because of the mass independence of electric rigidity, these machines are able to store a wide range of different particles, from light ions to heavy singly charged biomolecules, opening up unique research opportunities. However, earlier measurements have shown strong limitations in maximum beam intensity, fast decay of the stored ion current, and reduced beam lifetime. The nature of these effects has not been fully understood and an improved understanding of the physical processes influencing beam motion and stability in such rings is needed. In this paper, a comprehensive study into nonlinear and long-term beam dynamics studies is presented on the examples of a number of existing and planned electrostatic storage rings using the BETACOOL, OPERA-3D, and MAD-X simulation software. A detailed investigation into ion kinetics, under consideration of effects from electron cooling and multiple scattering of the beam on a supersonic gas jet target, is carried out and yields a consistent explanation of the physical effects in a whole class of storage rings. The lifetime, equilibrium momentum spread, and equilibrium lateral spread during collisions with the target are estimated. In addition, the results from experiments at the Test Storage Ring, where a low-intensity beam of ${\mathrm{CF}}^{+}$ ions at $93\text{ }\text{ }\mathrm{keV}/\mathrm{u}$ has been shrunk to extremely small dimensions, are reproduced. Based on these simulations, the conditions for stable ring operation with an extremely low-emittance beam are presented. Finally, results from studies into the interaction of 3--30 keV ions with a gas jet target are summarized.

Highlights

  • Electrostatic storage rings are able to store beams of charge particles at very low energies between some eV Á q and a few hundreds of eV Á q, where q denotes their charge state

  • Electrostatic storage rings operate at very low energies in the keV range and have proven to be invaluable tools for atomic and molecular physics

  • The lifetime, equilibrium momentum spread, and equilibrium lateral spread during collisions with the target are estimated

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Summary

INTRODUCTION

Electrostatic storage rings are able to store beams of charge particles at very low energies between some eV Á q and a few hundreds of eV Á q, where q denotes their charge state These storage devices have been developed alongside ion traps in response to the needs of the astrophysics, atomic physics, and molecular physics communities [1,2]. Strong limitations on beam intensity and reduced lifetime have been indicated and ion losses have been shown to be highly dependent on the lattice structure of the storage ring and beam current [15]. The nature of these effects has not been fully understood yet. On this basis we propose a consistent explanation of effects previously observed in electrostatic storage rings

R3eq xy
Hexapole
ION KINETICS AND LONG-TERM BEAM DYNAMICS
Kinetic equations
Multiple scattering of ions and rms emittance growth
BENCHMARKING OF ELISA EXPERIMENTS
OPERATION WITH INTERNAL TARGET
SIMULATIONS OF BEAM SHRINKING IN THE TSR ELECTRON COOLING EXPERIMENT
Application of a photocathode gun for electron cooling of low-energy ions
 1011 1
Collapse of beam emittance at low beam intensities
Findings
VIII. SUMMARY AND OUTLOOK
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