Low-energy beam experiment and beam-particle simulation for beam confinement fusion

We have studied confinement of hydrogen ions in a mirror field to estimate the feasibility of beam confinement fusion. A molecular-hydrogen beam of about 20 keV was injected in the mirror field to confine the dissociated hydrogen ions. In this MIGMA-like experiment, the number density of the ions was about 10¹¹ m⁻³ in a central region. A relaxation time of the confinement was measured by means of neutral-particle detection. The present energy range of 20 ke V results in the shortest relaxation time because of the largest cross section of the charge exchange process. The observed relaxation time of about 1 ms was governed by collision with residual hydrogen gas. We have also performed a computer simulation to estimate the highest ion density obtainable for a case of the ³HeD fusion. The behaviour of the ions and the associated electrons was calculated by means of particle-in-cell code. For this calculation, we assumed injection of high-energy intense pulsed ³He beam into a background plasma of D2. The confinement properties were examined as a function of the background plasma density.