Ignition Condition for p-11B Reactor with LHD type Magnetic Field Configuration

T.Watanabe, Y.Matsumoto1), M.Hishiki1), S.Oikawa1), H.Hojo2)

National Institute for Fusion Science, Toki, Gifu 509-5292, Japan
1) Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
2) Plasma Research Center, University of Tsukuba, Tsukuba, 305-8577, Japan

Proton-Boron fusion reactor (p-11B Reactor)
p + 11 B → 3 α + 8.7 MeV
probably offers the ultimate energy resource on the earth, because, 1) the fuels (Proton and Boron) are ubiquitous on the earth , and 2) fast neutrons are not generated. The side-reaction
p + 11B → n + 11C - 2.8 MeV
is an endothermal reaction and produces only slow neutrons when energy of proton exceed about 3MeV or more.

It has been, however, considered, in the Proton-Boron fusion reactor that bremsstrahlung power loss is too large to satisfy the ignition condition[1], because the atomic number of boron is so large (ZB=5 ). But, the progress of LHD experimental and theoretical studies have brought a new prospect for the Proton-Boron fusion reactor, i.e., (1)Production and confinement of high-energy particles by ICRF heating in the LHD and (2)Possibility of high β plasma confinement in LHD[2].

Particle orbits under ICRF heating in LHD is solved numerically. This study shows the following results. (1)The high-energy ion is heated further more by preferentially absorbing the RF energy, i.e., the runaway ion heating mode progresses. (2) LHD can confine fusion relevant high-energy ( MeV range) protons. (3)The LHD magnetic field can confine high-energy ions in the almost entire magnetic surface region[3]. Runaway ion heating process is analyzed by Langevin equation. It is shown that the steady state proton distribution function becomes a quasilinear plateau distribution function (QPDF). Nuclear fusion reaction rate < σ v > is derived assuming a QPDF for protons, and an ignition condition of p-11B reactor is analyzed and are shown to be possible to be satisfied.


[1] J.M.Dawson, "Advanced Fusion Reactors", {Fusion edited by E.Teller (1980) vol. 1 part B } Academic Press, New York, 1980) 453-501.
[2] T.Watanabe and H.Hojo, J. Plasma Fusion Res. SERIES, 5 (2002) 487-490.
[3] Y.Matsumoto, et.al., JJAP (2003) in printing.