Plasma heating with multi-MeV neutral atom beams Page: 4 of 48
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Incarporatinq these measures would greatly decrease the amount of current
required to yield a particular neutral injection power. In this paper, we
propose a novel heating method in which negative ions of atomic mass A > *-
AMU are accelerated to 1~2 MeV/AMU, neutralized, and injected into a plasma
(Fig. t). There they go through successive stages of ionization, heat the
plasma as they slow down, and under appropriate conditions drive current»
Negative deuterium beams might also be used for this scheme at energies of 1^2
MeV/AMU, although, as will be mentioned, using D- would sacrifice some of the
benefits associated with the heavier ions. These high energies were not a
viable option for the electrostatic injectors conventionally used for neutral
injection, where high energies required equally high voltages relative to
ground. However, this connection between energy and operating voltage ifa
severed if instead onp uses a p,F linear accelerator in which case one pays for
greater energy by lengthening the accelerator rather than by a higher
potential. Since length probably can be more easily achieved and tolerated
near a reactor than can multimegavolt potentials, we propose to use a RV
accelerator.
Dawson and McKenzie1 and Grand2 have proposed injection of positive ions
(B+, Ne+, etc.) as an alternative to neutral hydrogen injection* Ottawa3 and
Thompson4 considered neutral helium beams for current drive and heating. The
advantages of the positive ion injection schemes are that, in principle, there
is no inefficiency due to incomplete beam neutralization, and that high
current positive ion sources are straightforward to build for a number of
elements. The ions are accelerated to ~ 1 MeV/AMU, at which energy the
completely ionized nuclei will be as well confined In the plasma as the alpha
particles produced by D-T fusion. After reaching the edge of the tokamak, the
ions drift Into the plasma on unconfined orbits with pp « (A/q), where is
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Grisham, L. R.; Post, D. E.; Mikkelsen, D. R. & Eubank, H. P. Plasma heating with multi-MeV neutral atom beams, report, October 1, 1981; New Jersey. (https://digital.library.unt.edu/ark:/67531/metadc1100151/m1/4/: accessed March 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.