Beam dynamics studies in the driver LINAC pre-stripper section of the RIA facility

Abstract

The RIA facility driver LINAC consists of about 400 superconducting (SC) independently phased rf cavities. The LINAC is designed to accelerate simultaneously several charge-state beams to generate as much as 400 kW of uranium beam power. The LINAC beam dynamics is most sensitive to the focusing and accelerating structure parameters of the pre-stripper section, where the uranium beam is accelerated from 0.17 keV/u to 9.4 MeV/u. This section is designed to accept and accelerate two charge states (28 and 29) of uranium beam from an ECR ion source. The pre-stripper section must be designed to minimize the beam emittance distortion of this two-chargestate beam. In particular, the inter-cryostat spaces must be minimized and beam parameters near transitions of the accelerating and focusing lattices must be matched carefully. Several sources of possible effective emittance growth are considered in the design of the pre-stripper section and a tolerance budget is established. Numerical beam dynamics studies include realistic electric and magnetic three-dimensional field distributions in the SC rf cavities and SC solenoids. Error effects in the longitudinal beam parameters are studied.