Abstract
The velocity distribution functions of newly born (t=0)
charged fusion
products (protons in DD and alpha particles in DT plasmas) of tokamak
discharges can be approximated by a monoenergetic ring distribution with
a
finite v∥ such that
v⊥≈v∥
≈Vj, where
½MjV2j
=Ej, the directed birth energy of
the charged fusion-product species j of mass
Mj. As the time t progresses, these
distribution functions will evolve into a Gaussian in velocity (i.e. a
drifting
Maxwellian type), with thermal spreads given by the perpendicular and parallel
temperatures T⊥j(t)
=T∥j(t), with
Tj(t) increasing as t
increases and finally reaching an isotropic saturation value offormula hereHere Td is the temperature of the
background deuterium plasma ions, M is the
mass of a triton or a neutron for j=protons and
alpha particles respectively, and
τj≈¼τsj
is the thermalization time of the fusion product species j in
the
background deuterium plasma, with τsj
the slowing-down time. For times t of
the order of τj, the distributions can be
approximated by a Gaussian in the total
energy (i.e. a Brysk type). Then, for times
t[ges ]τsj, the velocity distributions
of
the fusion products will relax towards their appropriate slowing-down
distributions. Here we shall examine the radiative stability of all these
(i.e. a
monoenergetic ring, a Gaussian in velocity, a Gaussian in energy, and the
slowing-down) distributions.
Publisher
Cambridge University Press (CUP)
Cited by
1 articles.
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