Yasuyuki Nomura

Suppression of Tilting Instability of a Compact Torus by Energetic Particle Beams

It is shown that the tilting motion of a compact torus can be stabilized by toroidally circulating energetic particle beams. The required beam current relevant to tilt stability is estimated to be sufficiently small compared to the plasma current if the circulation frequency of beam particles is close to the betatron frequency. As an example, this stabilizing method is applied to a field reversed configuration. Effects of the plasma surface current and beam divergences are also examined.

D3He fuels in a field-reversed configuration

Favorable features of the D3He fuel cycle in a field-reversed configuration are described. Based on a theoretical analysis, we find that the estimated plant efficiency is more than 70% and the 14 MeV neutron power fraction is as small as 1%. To reach the D3He ignition temperature of 100 keV with a reasonable external power source, one can first ignite a DT configuration and then alter the fuel to D3He. Hesting of the plasma is attributed to energetic fusion of charged particles and no additional heating is necessary. The equilibrium of D3He ignited plasmas may be self-sustained due to the preferential trapping of fusion proton in a field-reversed configuration.

Stochasticity of Phase Trajectory of a Charged Particle in a Plasma Wave

Stochastic behavior of charged particles in finite amplitude plasma waves is studied by means of particle simulations under the condition that the perturbation scheme breaks down. The improved expression of resonances for the case of a large perturbation is introduced. Then the growing process of the stochastic region is examined and accordingly the width of the stochastic region is discussed. As a result, the origin of inapplicability of the perturbation scheme to this case is clarified. The validity of Chirikovs criterion is also ascertained. Discussions on the effects of higher order resonances are also presented.

Dissipative Effects on Stable RFP Configurations

Evolutions of RFP equilibria due to dissipative effects are studied theoretically. It is shown that the existence of stable RFP equilibria satisfying ideal and nonideal MHD stability criteria requires adequate hollow temperature profiles. If no profile control is applied to these RFP equilibria, the sufficient condition of stability for m =1 modes is first violated due to the disappearance of the toroidal current reversal near the surface within a short time.