Abstract
1098-4402= The classical electrostatic Harris instability is generalized to the case of a one-component intense charged particle beam with anisotropic temperature including the important effects of finite transverse geometry and beam space charge. For a long, coasting beam, the eigenmode code bEASt have been used to determine detailed 3D stability properties over a wide range of temperature anisotropy and beam intensity. A simple theoretical model is developed which describes the essential features of the linear stage of the instability. Both the simulations and the analytical theory clearly show that moderately intense beams are linearly unstable to short-wavelength perturbations provided the ratio of the longitudinal temperature to the transverse temperature is smaller than some threshold value. The delta-f particle-in-cell code BEST has been used to study the detailed nonlinear evolution and saturation of the instability.
Highlights
Periodic focusing accelerators, transport systems and storage rings [1,2,3] have a wide range of applications ranging from basic scientific research in high energy and nuclear physics, to applications such as heavy ion fusion, spallation neutron sources, tritium production and nuclear waste transmutation, to mention a few examples
Of particular importance at the high beam currents and charge densities of practical interest, are the effects of the intense self fields produced by the beam space charge and current on determining the detailed equilibrium, stability and transport properties
A characteristic feature of such plasmas is the nonuniformity of the equilibrium density profiles and the nonlinearity of the self fields, which makes detailed analytical investigation very difficult
Summary
Transport systems and storage rings [1,2,3] have a wide range of applications ranging from basic scientific research in high energy and nuclear physics, to applications such as heavy ion fusion, spallation neutron sources, tritium production and nuclear waste transmutation, to mention a few examples. It is important to develop simplified models of different instabilities familiar in electrically neutral plasmas which include the important effects of strong space-charge and finite geometry, and which may cause a degradation in beam quality One such instability is the electrostatic Harris instability [12]. In both cases the electric field of the density perturbation couples to the transverse oscillatory particle motion. The instability may lead to a deterioration of the beam quality and an increase in the longitudinal velocity spread, which would make focusing the beam difficult and impose a limit on the minimum spot size achievable in focusing the intense beam onto a target
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