Technical Design of Normal Conducting Re-buncher in the MEBT for Rare Isotope Science Project

Abstract

The front-end system of RISP heavy-ion accelerator (RAON) consists of an electron cyclotron resonance(ECR) ion source, a low energy beam transport (LEBT) line, a radio frequency quadrupole(RFQ) accelerator and a medium energy beam transport (MEBT) line. The MEBT system, which consists of quadrupole magnets, three normalconducting re-bunchers and several diagnostic devices, is installed between the RFQ accelerator and the superconducting linac (SCL). The three normal-conducting rebunchers are used to minimize the growths of the longitudinal emittance and to manipulate the particle distribution on longitudinal phase space for beam transportation in SCL. Several combination of the number of cavities was examined, and the quarter wave resonator(QWR) type rebuncher was chosen for MEBT line in RAON. The QWR cavity has a frequency of 81.25 MHz, a maximum electric field of 2.53 MV/m on the cavity surface with an electric field of 1 MV/m on the beam axis, a geometric beta factor of 0.032 and an effective length of 24 cm. In this presentation, I will present the results of baseline design for electro-magnetic field analysis and mechanical design for stress analysis, thermal stress analysis and cooling channel.