Calculations pertaining to the design of a prebuncher for a 150-MeV electron linear accelerator

Abstract

Results derived from calculations based on a one-dimensional ballistic model are presented to indicate the extent to which a current pulse of 150-keY electrons containing 1 j.1C of charge and having a duration of 15 nsec (FWHM) can be bunched or compressed into a single smaller pulse by a combination of accelerating and decelerating voltage gaps followed by a drift space. To be useful, the bunched current must be accelerated by an existing accelerator (ORELA), so the calculated results include estimates (upper and lower limits) of the fraction of the bunched beam that will be accelerated. It is found that with 8 voltage gaps the 15-nsec (FWH M) pulse can be reduced to a pulse of "" 4 nsec (FWHM) in a length"" 400 cm and that"" 50 %of this bunched pulse will be accelerated by ORELA. The fraction of the bunched pulse that will be accelerated is approximately the same as that for an unbunched pulse.

Calculations Pertaining to the Design of a Prebuncher for a 150-MeV Electron Linear Accelerator: II Radial Motion

“…(1) and (2) Here the assumption is made that Br is small so that the terms involving Br in Eqs. (1) and (2) may be neglected. This.being the case one may proceed exactly as in l, i.e., the 11 disk 11 approximation may be introduced, and obtain for the z-motion of the charge Q. t~e equations…”

“…If now Eq. (17) is applied to a peripheral electron in disk i and if the disk approximation is used (see 1) for the radial electric and azimuthal magnetic fields one obtains 1 dp . Equations (18)- (20) are still the radial equations for a single electron.…”