Abstract
A possible method for protecting beam ports and laser sources from alpha particles which are produced by a nuclear fusion in the fast ignition laser fusion power plant (KOYO-Fast) is proposed. Two simple dipolar magnetic fields generated by two coils installed at the tip of the beam port and at the side of the beam port are used for protecting the alpha particles coming into the inside of the beam port and colliding to the tip surface of the beam port. To calculate the behavior of alpha particles in the magnetic field, we use a 3D hybrid numerical simulation code. As a result, the intensity of 0.9 T of the magnetic flux density at the tip of the beam port is large enough for achieving the 10% reduction of the collision energy of the alpha particles to the tip surface of the beam port compared with the case without protection. Furthermore, the intensity of 1.35 T of the magnetic flux density at the center of the coil installed at the side of the beam port can guide the alpha particles coming into the inside of the beam port to the outside liquid wall perfectly.
