Theory and simulations of current drive via injection of an electron beam in the ACT-1 device
One- and two-dimensional particle simulations of beam-plasma interaction have been carried out in order to understand current drive experiments that use an electron beam injected into the ACT-1 device. Typically, the beam velocity along the magnetic field is V = 10/sup 9/ cm/sec while the thermal velocity of the background electrons is v/sub t/ = 10/sup 8//cm. The ratio of the beam density to the background density is about 10% so that a strong beam-plasma instability develops causing rapid diffusion of beam particles. For both one- and two- dimensional simulations, it is found that a significant amount of beam and background electrons is accelerated considerably beyond the initial beam velocity when the beam density is more than a few percent of the background plasma density. In addition, electron distribution along the magnetic field has a smooth negative slope, f' (v/sub parallel/) < 0, for v/ sub parallel/ > 0 extending v/sub parallel/ = 1.5 V approx. 2 V, which is in sharp contrast to the predictions from quasilinear theory. An estimate of the mean-free path for beam electrons due to Coulomb collisions reveals that the beam electrons can propagate a much longer distance than is predicted from a quasilinear theory, due to the presence of a high energy tail. These simulation results agree well with the experimental observations from the ACT-1 device.
- Research Organization:
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- DOE Contract Number:
- AC02-76CH03073
- OSTI ID:
- 6117352
- Report Number(s):
- PPPL-2197; ON: DE85008717
- Country of Publication:
- United States
- Language:
- English
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CURRENT-DRIVE HEATING
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JOULE HEATING
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700101* - Fusion Energy- Plasma Research- Confinement
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