Spiral line accelerator

Abstract

A casing has an entrance, an exit, linearly disposed, substantially parallel portions and curved portions joining the linear portions to define a spiral configuration. Electron pulses entering the casing are accelerated in the linear portions of the casings by pulsed electric fields applied across accelerating gaps in such linear portions. The gaps are aligned in common planes transverse to the linear portions and electrical power is applied by the same connector to the gaps to the gaps within each common transverse plane. Magnetic fields, constant in time over successive accelerating cycles, are created throughout the casing to confine electrons interior to the casing and to guide the electrons around the bends. A magnetic field perpendicular to the plane of each bend is created in the curved portions of the casing to guide the electrons around the bend, and its strength is adjusted to be appropriate for the average electron energy from previous accelerations. Another magnetic field parallel to the casing walls is applied over all portions of the spiral configuration where necessary to counteract the radially outward repulsive forces between the electrons of a high current pulse and to suppress growth of undesirable transverse motion of the electrons. A third magnetic field of the 'alternating gradient, strong focussing' type is applied over curved and linear portions of the spiral configuration as necessary to further confine the transverse motion of the beam within the casing and to direct electrons with deviations in energy from the average energy of the pulse to move substantially parallel to the casing walls.