Keishiro Niu

Effect of Nonuniform Implosion of Target on Fusion Parameters

The effect of the nonuniform implosion of the ICF target on the fusion parameters is investigated numerically. The numerical analysis is carried out by using a three-dimensional particle in cell code with sliding grids. The numerical results show that the nonuniformity of the implosion acceleration is required to be less than a few percent for a pellet of reactor size.

Spontaneous Generation of Electromagnetic Waves in Plasmas with Electron Thermal Flux

Spontaneous generation of propagating electromagnetic fields due to a microinstability is investigated for plasmas which convey electron thermal fluxes. The following two cases are examined: 1) Electromagnetic fields spontaneously excited by electrons in a velocity distribution of skewed Maxwellian type. 2) Electromagnetic waves generated by electrons in a velocity distribution which consists of a main part and a high energy part. In this case, the electron thermal flux can be very high. In both cases, induced electromagnetic waves with relatively low frequencies propagate parallel to the direction of Thermal flux

Proposal of Power Plant by Light Ion Beam Fusion

Twelve Marx generators, with a total stored energy of 26.4 MJ and a diode voltage of 10 or 5 MV, supply the energy to diodes to extract proton beams. A combination of two types of diodes is used. The proton beam pinches to a small radius by the azimuthal magnetic field, and its propagation is stabilized by the axial magnetic field. The cryogenic 6-mm-radius hollow shell target consists of three layers of lead, aluminum, and deuterium-tritium fuel. The target is imposed by a biased voltage of -1 MV in order to focus the proton beams on the target surface. The net plant efficiency is expected to be 33%, and the 800-MW (electric) net power can be supplied from one reactor with a 1-Hz operation frequency.

Filamentation and Two-Stream Instabilities of Light Ion Beams in Fusion Target Chambers

Filamentation and two-stream instabilities for a light ion beam (LIB) fusion system are investigated. Stability conditions for these two types of instabilities are derived for propagation through a background plasma. The results are illustrated by plotting stability boundaries for a proton beam propagating in a plasma.

Induced Magnetic Fields in Pellet Plasma Accompanied by Strongly Accelerated Motion

In the laser-driven pellet, the magnetic fields can be induced due to the unbalance between the fluid motion and the pressure change of the free-falling along the acceleration. Numerical computations cleary supports the theory.

Analysis for high compressible supersonic flow in a converging nozzle

In a converging nozzle, fluid is shown to be compressed to a very high density, especially in the supersonic region, if the initial Mach number of the fluid is large. Thus it is shown that spherical implosion can be used as a method to make high density materials.

DT-DD Hybrid Pellet for Inertial Confinement Fusion

A proposal here for inertial confinement fusion is to make use of a hybrid pellet with DT and DD. The spherical pellet consists of two layers of an inner DT and an outer DD. Alpha particles released from the inner layer due to DT reactions heat the DD fuel and induce reactions in the outer DD layer. Numerical simulations by using a hydrodynamic code make clear the following two facts: 1) The output fusion energy due to DD reactions can exceed the stored energy in the compressed pellet. 2) The critical value of ρ R is about 50 for the enough output fusion energy to a reactor.

Electromagnetic instability and stopping power of plasma for relativistic electron beams

The stopping power of a plasma for a relativistic electron beam (REB) is derived by taking a Weibel-type electromagnetic instability into account in a collisionless plasma. A quasi-linear theory is developed to derive the stopping power of the plasma due to the electromagnetic instability. The wave–particle interaction by use of the renormalization theory leads to a saturation level of instability. Thus the purely growing electromagnetic instability, including the effect of the beam temperature, decides an effective stopping length of the REB in the plasma.

High Absorption of Laser Light in Target Plasma with Plateau-Ramp Type Density Profile

The enhancement of resonance absorption in a laser-irradiated target plasma is ascertained by a numerical integration method for the fixed density profile which has a density plateau in front of the steep density gradient at the critical surface. It is shown that the interference between the laser light and the plasma wave excited near the critical surface in the target plasma plays an essential role in the enhancement of absorption. Conditions for enhancement are derived analytically with respect to the density gradient in the resonance region and the number density of plateau formed at the target surface. The results suggest that large absorption rates are retained during the laser irradiation to the target whose density profile is being modified.

Kinetic analysis of propagating ion beam with leading and trailing edges as ICF energy driver

Analysis is given for nonstationary propagation of rotating ion beam which has a finite length on the basis of Vlasov–Maxwell equations. The beam velocity distribution function is assumed to have a form of product of a modification function g which depends on time and axial coordinate multiplied by a steady solution f b 0 which is a known function of particle velocity and radial coordinate. Unknown function g is solved as the solution of Vlasov equation through electromagnetic fields induced by leading and trailing edges. These electromagnetic fields can be solved from the Maxwell equations by using beam distribution function and motion of electrons in background plasma.