A Waveguide Resonant Ring Electron Accelerator

This paper analyses a proposed accelerator, less than 1 meter long, capable of accelerating bunched electrons with a peak current of 100 A for a period of 50 rf cycles (20 nsec). The accelerator consists of an S-band disk-loaded circular waveguide, similar in design to the SLAC machine, incorporated into a waveguide resonant ring. Analysis of this system indicates that significant power buildup can occur if the length of the accelerator part of the ring is less than 1 meter. Further analysis of the power buildup and energy storage is made for a variety of rings having an accelerator section which is three, four, and five wavelengths long. Following the initial buildup of ring energy a beam of current bunched into 1/6th wavelength (60°), having a peak value of 100 A and an initial energy of 100 kV, is injected into the first cavity of the accelerator. Such a beam would extract half of the energy within the ring in approximately 20 nsec and have a nominal output energy of 10 MeV. By operating at 100°K, five such accelerators could be pumped by the same power source, thus increasing the output energy level to 50 MeV. The problem of handling a 100-A beam at low velocities is also investigated and a method utilizing space-charge neutralization by ionized gas is discussed.