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G Zwicknagel

Publications and source records attributed to G Zwicknagel.

4 recordsLinked to original sources
PubMed2002

Radiative recombination enhancement of bare ions in storage rings with electron cooling.

Experiments on ion-electron recombination in electron coolers show an enhancement of the recombination rate with respect to the standard theory. The theoretical explanation of this effect is an active field of research. Here a parameter-free model is presented in terms of the Vlasov equation. Its inherent scaling rests on two dimensionless variables and agrees with measurements. Additionally, numerical calculations yield the correct magnitude for the enhancement and trace its cause to the process of beam merging.

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PubMed2001

Dynamic structure factor for a two-component model plasma.

Analytical results for the structure factor of a two-component model plasma that describe an electron-ion plasma with modified interaction are derived from a Green function approach in different approximations. The random-phase approximation is improved by including the dynamic collision frequency, and results for the long-wavelength limit are extended to arbitrary wave numbers using the Mermin ansatz. After taking the classical limit of the resulting expressions, they are compared with molecular dynamics simulation results for the classical two-component model plasma.

Journal Article↗
PubMed2000

Stopping power of ions in a magnetized two-temperature plasma.

Using the dielectric theory for a weakly coupled plasma, we investigate the stopping power of an ion in an anisotropic two-temperature electron plasma in the presence of a magnetic field. The analysis is based on the assumption that the energy variation of the ion is much less than its kinetic energy. A general expression for the stopping power is analyzed for weak and strong magnetic fields (i.e., for the electron cyclotron frequency less than and greater than the plasma frequency), and for low and high ion velocities. It is found that the usually velocity independent friction coefficient contains an anomalous term which diverges logarithmically as the projectile velocity approaches zero. The physical origin of this anomalous term is the coupling between the cyclotron motion of the electrons and the long-wavelength, low-frequency fluctuations produced by the projectile ion.

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