Weight growth due to resonant simulation particles and a modified δf algorithm with smooth switching between δf and total-f methods

Qin, Hong; Davidson, Ronald C.; Startsev, Edward A.

doi:doi:10.1063/1.2920201

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Errors in ram velocity and temperature measurements inferred from satellite-borne retarding potential analyzers

Retarding potential analyzers (RPAs) [ Heelis and Hanson, Measurement Techniques in Space Plasmas, in Geophys. Monogr. Ser., Vol. 102 (AGU, Washington, D.C., 1998), p. 61 ] have been used extensively in space science over the past five decades to provide in situ estimates of ion velocities and temperatures. It has been shown previously that the use of biased grids in such instruments creates a nonuniform potential in the grid plane, which leads to errors in inferred parameters. A simulation of ...

Betatron radiation from density tailored plasmas

In laser wakefield accelerators, electron motion is driven by intense forces that depend on the plasma density. Transverse oscillations in the accelerated electron orbits produce betatron radiation. The electron motion and the resulting betatron radiation spectrum can therefore be controlled by shaping the plasma density along the orbit of the electrons. Here, a method based on the use of a plasma with a longitudinal density variation (density depression or step) is proposed to increase the tra...

When applying the standard δf particle-in-cell simulation method to simulate linear and nonlinear collective instabilities with coherent structures, wave-particle interaction may result in large weight growth for resonant or nearly resonant simulation particles. In this paper, we demonstrate that the large noise associated with the large weight of nearly resonant simulation particles can produce significant error fields at the nonlinear stage of the instability. To overcome this deleterious effect, we have developed a modified δf method that contains a smooth switching algorithm between the δf and total-f methods. Before the switch, the simulation effectively makes use of the desirable low-noise feature of the δf method for small weight to accurately follow unstable mode structures. When the weight function becomes large during the nonlinear phase, the low-noise advantage of the δf method ceases to be significant and the simulation is switched to the total-f method to avoid the large noise induced by nearly resonant simulation particles. This algorithm has been successfully applied to simulation studies of the electrostatic Harris instability driven by large temperature anisotropy in high-intensity charged particle beams typical of applications in high current accelerators, including high-energy density physics and heavy ion fusion.

Article Outline

INTRODUCTION
LARGE WEIGHT GROWTH DUE TO RESONANT AND NEARLY RESONANT SIMULATION PARTICLES
MODIFIED δf ALGORITHM WITH SWITCH BETWEEN δf AND TOTAL- f METHODS
NUMERICAL EXAMPLE OF ELECTROSTATIC HARRIS INSTABILITY DRIVEN BY STRONG TEMPERATURE ANISOTROPY
CONCLUSIONS AND FUTURE WORK

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KEYWORDS and PACS

Keywords

plasma instability, plasma simulation

PACS

52.65.Rr

Particle-in-cell method
52.65.Vv

Perturbative methods
52.25.Dg

Plasma kinetic equations

ARTICLE DATA

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http://dx.doi.org/10.1063/1.2920201

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1070-664X (print)

1089-7674 (online)

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$abstract.society.value is a Member of CrossRef

American Institute of Physics

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