Longitudinal compression of ion beams

Longitudinal compression of ion beams being necessary in some driver schemes intended for realizing heavy ion inertia fusion is under consideration. With account of Coulomb forces in beams two compression schemes are investigated: with conservation of longitudinal phase volume of beams and with phase volume increase. The results obtained are valid under ideal linearity of the groupping field. The number of high-frequency voltage harmonics required for ensuring sufficient field linearity can be determined only by means of numerical simulation. Preliminary calculations have shown that ion losses under beam groupping because of nonlinearity of the high-frequency field depend on beam current and number of used harmonics. At beam current < 10 A three harmonics ensure 95% of beam assembly; at higher current for obtaing the same efficiency of beam assembly the increased number of harmonics is required. The parameters of the compression system are optimized, taking as an example heavy ion inertial fusion plant, with 10 J beam energy and 25 ns target irradiation time