Propagation of focused proton beam

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 electrostatic force induced 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 electron beam is proposed to be launched simultaneously with the launch of 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. (author)