GB997673A - Termination for high energy particle linear accelerators - Google Patents

Abstract

997,673. Linear particle accelerators. VARIAN ASSOCIATES. June 25, 1962 [June 29, 1961], No. 24355/62. Drawings to Specification. Heading H1D. A travelling-wave linear particle accelerator has a terminating section of waveguide in which all the residual wave energy is absorbed completely. The usual output feeder is not then required and the beam focusing solenoid can be readily slipped over the accelerating structure; also the accelerating structure is free to expand. The terminating section of a disc-loaded waveguide is itself disc-loaded and to provide the attenuation the walls may be of magnetic stainless steel, or coated, e.g. in strips of gradually increasing thickness and by spraying on previously sand-blasted surfaces, highly resistive metal powder, e.g. of stainless steel, iron or aluminium-iron-chromium or cobaltiron-nickel alloy materials. In other methods the loading discs made of or coated with highly resistive material or they may be grooved or they may have smaller apertures than the discs of the main accelerating section of waveguide to reduce the group velocity of wave propagation. In further methods mentioned, the terminating section may include a ferrite isolator or may be loaded with resistively coated ceramic members or the thickness of the discs increased over that in the accelerating section. A plate may be provided at the end of the terminating section to reflect residual wave energy, but the section is designed to absorb the reflected wave before it can enter the main accelerating section. Cooling is provided for the terminating section and cooling channels may be provided in the discs. The waveguide structure may be within a separate vacuum envelope or the walls of the guide may constitute the vacuum envelope. The accelerated beam may be passed through a continuation of the envelope or through a particlepermeable vacuum window.