Beam dynamics in an ultra-low energy storage rings (review of existing facilities and feasibility studies for future exp
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eam Dynamics in an UltraLow Energy Storage Rings (Review of Existing Facilities and Feasibility Studies for Future Experiments)1 A. I. Papasha, b, c, *, A. V. Smirnova, b, and C. P. Welschd, e a
Joint Institute for Nuclear Research, Dubna, Russia Planck Institute for Nuclear Physics, Heidelberg, Germany (former) c Karlsruhe Institute of Technology, Karlsruhe, Germany d University of Liverpool, UK eThe Cockcroft Institute for Accelerator Science and Technology, UK *email: [email protected]
bMax
Abstract—Storage rings operating at ultralow energies and in particular electrostatic storage rings have proven to be invaluable tools for atomic and molecular physics. Due to the mass independence of the elec trostatic rigidity, these machines are able to store a wide range of different particles, from light ions to heavy singly charged biomolecules. However, earlier measurements showed strong limitations on beam intensity, fast decay of ion current, reduced life time etc. The nature of these effects was not fully understood. Also a large variety of experiments in future generation ultralow energy storage and decelerator facilities including inring collision studies with a reaction microscope require a comprehensive investigation of the physical pro cesses involved into the operation of such rings. In this paper, we present review of nonlinear and long term beam dynamics studies on example of the ELISA, AD Recycler, TSR and USR rings using the computer codes BETACOOL, OPERA3D and MADX. The results from simulations were benchmarked against experimental data of beam losses in the ELISA storage ring. We showed that decay of beam intensity in ultralow energy rings is mainly caused by ion losses on ring aperture due to multiple scattering on residual gas. Beam is lost on ring aperture due to small ring acceptance. Rate of beam losses increases at high intensities because of the intrabeam scattering effect adds to vacuum losses. Detailed investigations into the ion kinetics under consideration of the effects from electron cooling and mul tiple scattering of the beam on a supersonic gas jet target have been carried out as well. The life time, equilib rium momentum spread and equilibrium lateral spread during collisions with this internal gas jet target were estimated. In addition, the results from experiments at the TSR ring, where low intensity beam of CF+ ions at 93 keV/u has been shrunk to extremely small dimensions have been reproduced. Based on these simula tions, conditions for stable ring operation with extremely low emittance beam are presented. Finally, results from studies into the interaction of ions with a gas jet target at 3–30 keV energy range are summarized. DOI: 10.1134/S106377961402004X 1
CONTENT
1. Introduction 2. Nonlinear effects in electrostatic storage rings 2.1. Equations of motion in electrostatic deflector 2.2. Acceptance and betatron tune shift in the ELISA ring 3. Ion kinetics and long term beam dynamics 3.1. Kinetic equations 3.2. Multiple scattering of ions 3.2.1. Rate of r.m.
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