Injector and Waveguide Design Parameters for a High Energy Electron-Positron Linear Accelerator

Abstract

This paper discusses the electron beam optics design of a six klystron, twelve section, 450 Mev electron 350 Mev positron linear accelerator which has been designed as an injector for a storage ring. The beam centerline comprises three zones; namely, the injection system, the high current waveguide sections and the high energy gain sections. The injection system is arranged such that the beam from a pulsed diode source is chopped and prebunched at 2856 Mc to provide well defined tightly focussed short bunches of electrons for injection into the first accelerator section. A nanosecond inflection system, located between the chopper and prebuncher cavities, provides variable short pulse capability as well as 9.5 Mc modulation of the beam to produce a train of short pulses during each gun pulse. The first four waveguide sections are designed for an unloaded beam energy of 107.5 Mev, and 500 ma peak current at 60 Mev with 10 MW peak r-f power at each input coupler. A positron converter is located at the end of these sections and immediately prior to the high energy gain portion of the machine which comprises eight waveguides each of which is 504 cm in length and designed for an unloaded beam energy of 45.4 Mev with 10 MW peak r-f input power. Details of the microwave design parameters and some electron beam characteristics are presented together with preliminary measurements of actual beam performance.