Simulation of propagating a proton beam in a reactor

One of the difficulties of light ion beam fusion is to propagate the beam in the reactor cavity and to focus the beam on the target. The light ion beam has some local divergence angle because there are several causes for divergence at the diode. The ion beam propagates with a speed of one tenth of light speed. With this high speed, the leading edge of the ion beam cannot be charge-neutralized due to the delay of neutralization by the inertia of thermal electrons in the background plasma. The electrostatic force induced by this mechanism at the leading edge causes the beam divergence during propagation. To confine the beam in a small radius during propagation, the magnetic field must play a role. Here the electron beam is proposed to be launched simultaneously with the launch of a proton beam. If the electron beam has the excess current, the beam induces the magnetic field in the negative azimuthal direction, which confines the ion beam in a small radius by the electrostatic field, as well as the electron beam by the Lorentz force. The metal guide around the beam path helps the beam confinement and reduces the total amount of magnetic field energy induced by the electron current. Simulation shows that the proton beam with the comoving electron beam propagates in a small radius confined in the metal guide.