Beam Dynamics Studies on Low and Medium Energy Beam Transport With Intense H⁻ Ions for J-PARC Linac

Japan Proton Accelerator Research Complex (J-PARC) linac was intensity-upgraded up to pulse current of 50 mA of H⁻ beam by replacing the ion source and the Radio Frequency Quadrupole(RFQ). We measured beam properties at the end of low energy beam transport (LEBT) line test stand under several conditions to investigate the transverse halo and space charge effects of an intense H⁻ ions. The LEBT is composed of two solenoid magnets. Furthermore, space charge neutralization effects in the residual gas were considered into account to describe the behavior of the beam phase space evolution. LEBT transmission efficiency, beam losses were estimated and optimization for beam matching into acceptance of the RFQ is studied. Two-solenoid based LEBT section is connected to the RFQ which is followed by a medium energy beam transport (MEBT) line. In this paper, we discuss the outcomes of beam emittance measurements and the results from beam dynamics simulations throughout LEBT and the RFQ acceleration.