Study of a Focused Beam from the Duoplasmatron Proton Source

Abstract

Aberrations of the preaccelerator focusing electrodes were studied experimentally by obtaining emittance diagrams for a beam of 38 and 60 mA. Aberrations observed were similar to those obtained from previous ray-tracing calculations. According to the calculations, the cause of aberrations is improper distribution of the radial field in the exit portion of the lens. More distortion of the phase-space diagram was observed for the higher beam current than the lower one. The observed emittance area increased by more than a factor of two when the beam current was changed from 38 to 60 mA. Even if aberrations were entirely eliminated, this fact may raise a serious problem in beam matching for a large beam current. A technique for measuring the emittance of the beam at 200 kV was developed and the details are described.