This study particularly focuses on the dissipation processes of trapped ion beams such as deceleration and diffusion, which are caused by Coulomb binary collisions. It demonstrated that collisions in ions or low-temperature electrons have major influences on ion beams. Beam convergence was improved by applying a magnetic field. To assess the medical applicability of our neutron source, a combined Monte-Carlo simulation with Diffusion-Reaction model was employed to evaluate the available neutron yield for the Boron Neutron Capture Therapy (BNCT) neutron source under the beam diffusion conditions. The paper found that the proposed electrostatic trap of deuterium beam ions could provide sufficient neutron generation for the therapy.
We investigate instabilities of electron beam particles confined in a cylindrical chamber using a 3dimensional full particle simulation. The global structure of electron beam plasma changes within 1 µs, and deforms to those formed by the instabilities such and the sausage and kink instabilities. The azimuthal mode of the electron density on the midplane of beam plasma is analyzed and the amplitude of mode number of 1 or more increases at 0.2 µs. It was also found that the temporal change of the electron density on the geometric axis is caused by the plasma oscillation.
The Lyapunov exponent analysis is carried out for ion motions in a non-adiabatic trap where the axial magnetic field from a solenoid is partially cancelled by that from a Helmholtz coil. In particular, relation between the Lyapunov exponents and the trapped rate of ions injected in the axial direction is numerically studied. It is found that there exist energy minimizing the particle trapped rate, and the Lyapunov exponent for the axial velocity is found to be minimized with that energy.
The ion trajectory in a hollow cathode discharge plasma to which a magnetic field combined a solenoid and a Helmholtz coil is applied is analyzed, and the ion energy distribution at the cathode or the end of the device is examined. It was shown that the ratio of particles lost at the end of the device and those lost during collision with the cathode can be changed by varying the length of the cylindrical cathode.
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