Gyrotron Beam Generation with Helical Magnetic Fields

摘要

This report presents the results of an investigation into the basic properties of a new type of electron gun for generating high transverse velocity beams, the bifilar helix - Pierce gun or H-gun. The H-gun differs significantly from presently used magnetron injection guns (MIGs) in that first a laminar, low transverse velocity beam is formed and then transverse velocity is imparted by propagating the beam through the magnetic field of a bifilar helix. In order to evaluate the H-gun, an analytic and computational study was conducted to examine the relationships between the magnetic fields (axial and helical), and the beam properties after existing the helical field. The effects of the helix field entrance profile, the helix-axial field gyroresonance, and helix field gradients have been taken into account in the investigation. Based on the results of this research, conditions have been specified which will produce a high transverse velocity beam with low axial velocity spread. In particular, it has been found that an adiabatic helix entrance profile can provide a flexible means of generating high quality beams for gyro-devices. (Author)