Cyclotron radiation from a relativistic electron beam in a static magnetic field

1984 ◽  
Vol 32 (1) ◽  
pp. 55-80 ◽  
Author(s):  
Z. G. An ◽  
Y. C. Lee ◽  
T. T. Lee ◽  
H. H. Chen
Keyword(s):  
Magnetic Field ◽  
Electron Beam ◽  
Dispersion Relation ◽  
Relativistic Electron ◽  
Relativistic Electron Beam ◽  
Particle System ◽  
Critical Energy ◽  
Linear Dispersion ◽  
Linear Dispersion Relation ◽  
Ring Model

Electromagnetic cyclotron instabilities of a relativistic electron beam propagating in an external magnetic field are studied by considering electron motion inside a self-consistent electromagnetic field. When the number of electrons in a subgroup is greater than two, or when the phases are random, the linear dispersion relation obtained agrees with that of Chu et al. for a gyrotron in a ring model. When the number of electrons in a subgroup is limited to two only, the linear dispersion relation is different in that it has an instability threshold. Completely nonlinear motion is also studied using the method of Poincaré's return map, or by considering the departure rate of nearby trajectories. Stochasticity is observed in the nonlinear oscillation of the wave-particle system when a critical energy is exceeded. Physical implications for gyrotron operation are also discussed.

scholarly journals Compton and Raman free electron laser stability properties for a cold electron beam propagating through a helical magnetic wiggler

1985 ◽  
Vol 33 (3) ◽  
pp. 387-423 ◽  
Author(s):  
John A. Davies ◽  
Ronald C. Davidson ◽  
George L. Johnston
Keyword(s):  
Magnetic Field ◽  
Electron Beam ◽  
Dispersion Relation ◽  
Free Electron ◽  
Free Electron Laser ◽  
Relativistic Electron Beam ◽  
Cold Electron ◽  
Wiggler Magnetic Field ◽  
Laser Stability

This paper gives an extensive characterization of the range of validity of the Compton and Raman approximations to the exact free electron laser dispersion relation for a cold, relativistic electron beam propagating through a constantamplitude helical wiggler magnetic field. The electron beam is treated as infinite in transverse extent. Specific properties of the exact and approximate dispersion relations are investigated analytically and numerically. In particular, a detailed numerical analysis is carried out to determine the range of validity of the Compton approximation.

Fast-wave interaction with a relativistic electron beam

1974 ◽  
Vol 11 (2) ◽  
pp. 299-309 ◽  
Author(s):  
P. Sarangle
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Electron Beam ◽  
Relativistic Electron ◽  
Microwave Radiation ◽  
Relativistic Electron Beam ◽  
Parametric Instability ◽  
Travelling Wave ◽  
Fast Wave ◽  
Coupled Modes

The excitation of a relativistic electron beam, by means of a fast waveguide structure, is examined. Here the beam is injected into a modified waveguide, and interacts with the modes of the guide in such a way as to transform some of its energy into microwave radiation. This microwave generation device, called the Ubitron, is based upon a fast-wave excitation of a magnetically modulated relativistic electron beam. The beam is modulated by injecting it into a small spatially periodic magnetic field region within the guide. Analysis of this interaction shows that the slow space charge beam mode couples actively to the fast transverse electric guide mode. The result is parametric instability of the coupled modes. Synchronism between the doppler-shifted transverse travelling wave and the undulating electron beam results in a transfer of energy from the beam to the transverse field. The parametrically growing field can be a source of microwave radiation. The period magnetic field, together with the beam density, provide the coupling media between the unstable waves. The growth rate of the instability is shown to depend, in a nonlinear manner, on the product of the beam plasma frequency and the strength of the applied rippled magnetic field. The growth rate is obtained as a function of the system parameters.

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