Numeric modeling of focusing of heavy-ion beams on a target in a reactor

An alternative direction in pulsed thermonuclear fusion is pulsed heavy-ion fusion, in which multiple microexplosions of targets irradiated with heavy-ion beams occur in a manner so as not to damage the acceleration-storage complex of the system. in real designs the accelerator and the target are separated in space by a distance of ∼10 m, and the propagation of the ion beams in the reactor presupposes free flight of the beam particles. It is obvious that the parameters of the beams at the exit of the acceleration-storage system must have values such that the ions can be focused on the thermonuclear target; these parameters are achieved with the help of appropriate electromagnetic fields in the acceleration-storage system since such fields can no longer be produced in the reactor. The electromagnetic fields of neighboring beams also produce a well-known defocusing effect, in particular, in connection with the action of the charge of the target itself. As is well known, heavy ions in this subrelativistic energy range are retarded in the outer layers of the target material primarily by the classical mechanism of ionization losses. The initial electric charge passes into the target, giving rise to bremsstrahlung and sometimes to defocusing of the successive portions of the ion beams. Since the target charge increases in proportion to the number of beams, the effects of the neighboring beams simply add. Thus one of the important problems of pulsed heavy-ion fusion-achievement of a high percentage of beam ions reaching the target (without the use of complicated effects of neutralization of the ions)-is studied on the basis of a direct numerical experiment