Speaker
Carmine Castaldo
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1066.pdf
Alpha channeling by inverse nonlinear damping of ion Bernstein waves
C. Castaldo1, A. Cardinali1
1
ENEA, C.R. Frascati, Via E. Fermi 45, I-00044 Frascati, Italy
Second harmonic cyclotron damping of mode-converted ion Bernstein waves on
minority Tritium ions in D-H(T) tokamak plasma has been proposed as an efficient method to
improve the fusion yield expected in thermal equilibrium [1]. Despite the dilution due to the
presence of the Hydrogen, which is necessary to allow the mode conversion of the fast
magnetosonic waves, the acceleration of T ions in the energy range of 50-100 keV, i.e. near
the peak of DT fusion cross section, produces higher reactivity than the ideal isotopic blend
DT at thermal equilibrium for the same kinetic profiles. In this scenario, IBW nonlinear
inverse Landau damping on the fusion alpha particles might be observed at Doppler-shifted
half-integer resonant layer 𝜔 = (3/2)Ω! + 𝑘∥ v∥ (Fig. 1). The nonlinear RF-induced diffusion
tensors in velocity and physical space are here derived in the frame of single-particle
dynamics. We then discuss numerical solutions of the relevant Fokker-Planck equation,
taking into account the collisions of the alpha particles with the plasma background as well as
the source and sink terms. During the time evolution of the alpha particle distribution
function towards the steady state, inverse nonlinear Landau damping might channel a fraction
of the alpha power into the ion Bernstein wave power. This will provide a method for
implementing the concept of alpha channeling [2].
1
IBW region ω = 3/2Ω
α
0,9
-1
k = 2.0 m
0,8 ||
DH hybrid DH cut-off
resonance
0,7
o
/v
0,6
||res
FW region
v
0,5
-1
k = 3.3 m
||
0,4
0,3
ω=2Ω
Τ
0,9 0,95 1 1,05 1,1
R/R
o
Fig. 1. Scheme of alpha power channeling in tokamak plasma with isotopic composition such that 𝑛! 𝑛! = 0.9
and 𝑛 ! 𝑛! = 0.05 and magnetic field on axis is 𝐵! = 2.8 𝑇. The FW are coupled from the low field side, at the
operating frequency 𝑓! = 32 𝑀𝐻𝑧. The resonant parallel velocities v∥,!"# , normalized to the velocity vo at the
peak (3.5 MeV) of the a source energy spectrum, are shown for parallel wavenumber 𝑘∥ = 3.3 𝑚 !! (red, dashed
line) and 𝑘∥ = 2.0 𝑚 !! (blue, continuous line). Here R is the major radius coordinate and Ro is the position of
the magnetic axis.
[1] C. Castaldo, A. Cardinali, Phys. Plasmas 17 072513 (2010)
[2] N. J. Fish and M. H. Hermann, Nucl. Fusion 35, 1753 (1995)
