Beam matching section in the INS heavy ion linac complex

The beam transport system between a 25.5-MHz split-coaxial RFQ and a 51-MHz interdigital-H linac has been designed. This transport system is composed of a charge stripper, a 25.5-MHz rebunching cavity and two quadrupole doublets. A 170-keV/u beam passes through the stripper and its charge state is increased up to a charge-to-mass ratio greater than 1/10. The rebuncher causes an aberration of the longitudinal beam profile due to its non-linear accelerating field. In order to contain the distorted beam profile by the aberration in the acceptance of the IH, the rebunching cavity must be operated at 25.5 MHz. We have carried out a beam trace by taking account of the aberration and the effects of the increase of the charge state, the energy-loss, the straggling and the scattering in the stripper, and compared its results with the design assuming a linear system