W-band sheet beam klystron simulation

Abstract

Abstract. With the development of ever higher energy particle accelerators comes the need for compactness and high gradient, which in turn require very high frequency high power rf sources. Recent development work in W-band accelerating techniques has spurred the development of a high-power W-band source. Axisymmetric sources suffer from fundamental power output limitations (P sat~λ 2 ) brought on by the conflicting requirements of small beam sizes and high beam current. The sheet beam klystron allows for an increase in beam current without substantial increase in the beam current density, allowing for reduced cathode current densities and focussing field strengths. Initial simulations of a 20:1 aspect ratio sheet beam/cavity interaction using the 3 dimensional particle-in-cell code Magic3D have demonstrated a 35% beam-power to RF power extraction efficiency. Calculational work and numerical simulations leading to a prototype W-band sheet beam klystron will be presented, together with preliminary cold test structure studies of a proposed RF cavity geometry.

Power Sources for Accelerators Beyond X-Band

“…This has the obvious additional requirement of requiring the circuits to accept a larger beam, and several tricks have been proposed to do this. The annular beam 3 , sheet beam 4 , and multi-beam 5 klystrons are geometric variations on this idea. For the sheet and annular beam klystrons, the beam transport and interaction circuit designs are quite challenging, with mode competition and field uniformity being difficulties for the circuits, and stable, matched transport being challenges for the focussing.…”

A Study of Beam-wave Interaction Parameters on an X-band Sheet Beam Klystron

“…The advantages of sheet beam are that it can increase beam current without increasing current density, provide more beam power without increasing space charge forces which degrade tube efficiency. A typical SBK configuration is shown in Fig.1 The concept of SBK was first proposed by Kovalenko in Russia in 1938 [1]. In the following more than 60 years, SBK has not been developed rapidly because of the following reasons: a) The research on axial asymmetric electron-optical systems and beam-wave interaction systems required 3D simulation codes which have not been possible until recent years; b) The microwave vacuum devices of that time have already met the demands of microwave application systems.…”

Confined focused sheet beam flow of a thermionic linear electron source

“…Magnetic deflection focusing are amenable to high field strengths. Beam transport will be stable so long as focusing strength exceeds the space charge forces pushing the beam apart [6]. The present work is about the design, development and transport of a sheet beam in confined focusing of the emitter using flat instead of Pierce electrode.…”