LINEAR ACCELERATOR ACCELERATING MODULE TO SUPPRESS BACK-ACCELERATION OF FIELD-EMITTED PARTICLES

摘要

A method for the suppression of upstream-directed field emission in RF accelerators. The method is not restricted to a certain number of cavity cells, but requires similar operating field levels in all cavities to efficiently annihilate the once accumulated energy. Such a field balance is desirable to minimize dynamic RF losses, but not necessarily achievable in reality depending on individual cavity performance, such as early Q0-drop or quench field. The method enables a significant energy reduction for upstream-directed electrons within a relatively short distance. As a result of the suppression of upstream-directed field emission, electrons will impact surfaces at rather low energies leading to reduction of dark current and less issues with heating and damage of accelerator components as well as radiation levels including neutron generation and thus radio-activation.

主权项

1. A method for suppressing prevalent field emission in the upstream direction in a radio frequency (RF) accelerator, comprising:
providing an accelerator structure including plurality of cavities, a plurality of cells in each cavity, and an intermediate beam tube between the cavities; adjusting the beam length of the intermediate beam tube between the cavities according to the following equationLtube=(N+12)·Lcell≈(N+12)·βλ2. wherein Ltube is the beam length between cavities, Lcell is the length of the cell cavity, β is the particle velocity relative to the speed of light, λ is the wavelength of the accelerating mode, and N is an integer number; injecting a stream of electrons into said accelerator structure; and applying an accelerating field of at least 3 MV/m to accelerate the electrons to a relativistic speed.