Developing Sheet Beam Klystron Simulation Capability in AJDISK

Abstract

AJDISK is a 1D large signal klystron simulator developed at SLAC. A brief discussion of AJDISK's simulation algorithm is given and [1] is fully developed to show how AJDISK was extended to enable sheet beam klystron simulations. The primary requirement for extending "disk" simulators to sheet beam simulators is a space charge equation. Therefore, the electric field due to an infinitely thin plate of charge (infinitely thin in the direction of propagation) in a rectangular drift tube is derived. The derivation is extended to a "2D" space charge equation in which the plate is split into a series of rods with varying positions in y. The derived equations are compared with numerical simulations and measurement.

A Millimeter-Wave Klystron Upconverter With a Higher Order Mode Output Cavity

“…The klystron interaction structures were designed and simulated using the disk modeler AJDisk [5], with three and six cavity designs presented. Particle-in-cell (PIC) simulations using CST Particle Studio [6] of the three-cavity design are presented.…”

MAGIC2-D simulations of high efficiency klystrons using the core oscillation method

“…Through optimization, the drift tube and electron beam radii, beam voltage and current, cavities gaps and impedances were kept constant, whist all the other parameters were set free within a few percent window. In the process over 20,000 cases were simulated, of which 10 tubes were selected for further analysis using the 1D code AJDISK [10] and the 2D PIC code MAGIC [11]. The performances of these tubes simulated by the various codes are summarized in Figure 1.…”

Optimization of Klystron Designs Using Deterministic Sampling Methods

“…Given a set of parameters, such as cavity frequencies and positions, AJDISK will predict klystron performance characteristics, such as output power and gain. The algorithm, as described in [8], breaks the electron beam into thin rectangular plates, then calculates the electric field in each cavity using the space charge field from the other plates to determine the force on each plate. The dynamics of the charges (plates) are determined by the Lorentz force (conservation of momentum) equations given by…”

“…The above equation is integrated to find the charge position as a function of the fields E cav and E spch . For the calculations of E cav and E spch , the readers are referred to [8].…”