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The Effect of Non‐Coulomb Scattering of Relativistic Electrons on the Generation of Runaways in Multicomponent Plasma
Author(s) -
Igitkhanov Yu. L.
Publication year - 2012
Publication title -
contributions to plasma physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.531
H-Index - 47
eISSN - 1521-3986
pISSN - 0863-1042
DOI - 10.1002/ctpp.201210034
Subject(s) - physics , atomic physics , plasma , electron , ionization , coulomb , ion , scattering , tokamak , effective nuclear charge , charge (physics) , nuclear physics , quantum mechanics
Highly energetic runaway electrons are able to penetrate the electron shell of partly ionized heavy ions during collisions, for which reason they may be scattered by a positive charge effectively larger than that of a shielded nucleus. This effect increases the Coulomb cross section and can be treated via an effective ion charge Z eff ( ε kin ) that depends on the energy of the incident electrons ε kin . The increase of effective charge number with increasing electron energy in multi‐component plasmas renders qualitatively the same result as high Z eff Coulomb plasmas. Since the generation rate of runaways depends on Z eff , its production during the mitigation of disruptions by massive gas injection could in some cases decrease owing to a heavy impurity concentration in the boundary tokamak plasma. This may explain why it has been observed that the runaway's avalanche is suppressed at electron densities below the so‐called “Rosenbluth density” (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)