Studies of beam dynamics in relativistic klystron two-beam accelerators

摘要

Two-beam accelerators (TBAs) based upon free-electron lasers (FELs) or211u001erelativistic klystrons (RK-TBAs) have been proposed as efficient power sources 211u001efor next generation high-energy linear colliders. Studies have demonstrated the 211u001epossibility of building TBAs from X-band ((approximately)8-12 GHz) through Ka 211u001eband ((approximately) 30-35 GHz) frequency regions. Provided that further 211u001eprototyping shows stable beam propagation with minimal current loss and 211u001eproduction of good quality, high-power rf fields, this technology is compatible 211u001ewith current schemes for electron-positron colliders in the multi-TeV center-of-211u001emass scale. A new method of simulating the beam dynamics in accelerators of this 211u001etype has been developed in this dissertation. There are three main components to 211u001ethis simulation. The first is a tracking algorithm to generate nonlinear transfer 211u001emaps for pushing noninteracting particles through the external fields. The second 211u001ecomponent is a 3D Particle-In-Cell (PIC) algorithm that solves a set of Helmholtz 211u001eequations for the self-fields, including the conducting boundary condition, and 211u001egenerates impulses that are interleaved with the nonlinear maps by means of a 211u001esplit-operation algorithm. The Helmholtz equations are solved by a multi-grid 211u001ealgorithm. The third component is an equivalent circuit equation solver that 211u001eadvances the modal rf cavity fields in time due to excitation by the modulated 211u001ebeam. The RTA project is described, and the simulation code is used to design the 211u001elatter portions of the experiment. Detailed calculations of the beam dynamics and 211u001eof the rf cavity output are presented and discussed. A beamline design is 211u001epresented that will generate nearly 1.2 GW of power from 40 input, gain, and 211u001eoutput rv cavities over a 10 m distance. The simulations show that beam current 211u001elosses are acceptable, and that longitudinal and transverse focusing techniques 211u001eare sufficient capable of maintaining a high degree of beam quality along the 211u001eentire beamline. Additional experimental efforts are also described.