Dispersion, spatial growth rate, and start current of a Cherenkov free-electron laser with negative-index material

2015 ◽  
Vol 22 (8) ◽  
pp. 083111 ◽  
Author(s):  
Yuanyuan Wang ◽  
Yanyu Wei ◽  
Dazhi Li ◽  
Keisuke Takano ◽  
Makoto Nakajima ◽  
...  
Keyword(s):  
Growth Rate ◽  
Free Electron ◽  
Free Electron Laser ◽  
Negative Index ◽  
Negative Index Material ◽  
Spatial Growth ◽  
Spatial Growth Rate

Numerical investigations on the effects of geometrical parameters on free electron laser instability

2008 ◽  
Vol 74 (6) ◽  
pp. 741-747
Author(s):  
B. S. SHARMA ◽  
N. K. JAIMAN
Keyword(s):  
Growth Rate ◽  
Electron Beam ◽  
Free Electron ◽  
Free Electron Laser ◽  
Instability Growth Rate ◽  
Magnetized Plasma ◽  
Geometrical Parameters ◽  
Uniform Density ◽  
Backward Wave Oscillator ◽  
Instability Growth

AbstractIn this paper we numerically investigate the effects of various geometrical parameters of a backward wave oscillator (BWO), filled with a magnetized plasma of uniform density and driven by a mild relativistic solid electron beam, on the instability growth rate (Γ) of a free electron laser (FEL). The FEL instability is numerically calculated and the result is compared with the instability growth rate of an annular electron beam for the same set of parameters. The instability growth for a solid electron beam scales inversely to the seventh power of relativistic gamma factor γ0 and directly proportional to the corrugation amplitude.

A local theory of effect of beam pre-modulation on gain and efficiency in a surface wave pumped free electron laser

2014 ◽  
Vol 32 ◽  
pp. 1460351
Author(s):  
Jyotsna Sharma ◽  
Suresh C. Sharma ◽  
Anuradha Bhasin ◽  
V. K. Jain
Keyword(s):  
Growth Rate ◽  
Surface Wave ◽  
Free Electron ◽  
High Frequency ◽  
Free Electron Laser ◽  
Millimeter Waves ◽  
Local Theory ◽  
Vacuum Region ◽  
Laser Instability ◽  
Frequency Radiation

A pre-modulated relativistic electron beam (REB) counter propagating to the surface wave in the vacuum region Compton backscatters the surface wave into a high frequency radiation. The surface wave extends into the vacuum region and can be employed as a wiggler for the generation of sub-millimeter waves. The growth rate and gain were evaluated for a typical FEL (Free Electron Laser) parameters and It is found that the growth rate and gain of the surface wave pumped free electron laser increases with the modulation index. Moreover, the growth rate of the FEL (Free electron Laser) instability scales as one-third power of the beam density in the Compton regime.

scholarly journals Electron Cyclotron Maser Emission near the Cutoff Frequencies

1983 ◽  
Vol 36 (5) ◽  
pp. 725 ◽  
Author(s):  
RG Hewitt ◽  
DB Melrose
Keyword(s):  
Growth Rate ◽  
Cutoff Frequency ◽  
Solar Radio Emission ◽  
Type I ◽  
Loss Cone ◽  
Spatial Growth ◽  
Lower Band ◽  
Wide Range ◽  
Narrow Frequency Band ◽  
Spatial Growth Rate

An earlier discussion of loss-cone driven cyclotron masers is extended to cover the case where the emission occurs close to the cutoff frequency of the 0 mode or the x mode. In general, wave growth may occur in one or two bands, and when two bands are allowed the lower band is close to the cutoff frequency. With the exception of the x mode at 8 = 1, growth in the lower band is allowed only for OJp/D. > 8 and cos28 > t for the 0 mode and for OJp/Q. > {s(s-I)}-!- and cos28 > (s-I)/8 for the x mode, and growth in the lower band has no particularly favourable features when allowed. For the X mode at 8 = 1 both bands are allowed for all OJp/D. $ 1 and growth in the lower band is possible over a wide range of angles in a very narrow frequency band. The spatial growth rate can be quite large due to the small group speed. However, the large spatial growth rate is offset by the short pathlengths for growth in a slowly spatially varying magnetic field due to the very narrow bandwidth of the growing waves. It is found that growth in the lower band is at best no more effective than growth in the upper band. We discuss the relative merits of growth in the two bands in a suggested application to terrestrial kilometric radiation. We also discuss cyclotron theories for type I solar radio emission, pointing out that our results do not favour such theories, and for solar microwave spike bursts.

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