Characterization of Optical Emission Mechanism Utilizing Traveling Electron Beam on a Waveguide

Yamada

2011

Physics of Plasmas

In this paper, the operation of the stimulated emission in Cerenkov free-electron laser (CFEL) is studied on the basis of the modulations of electron velocity and density by the electromagnetic (EM) field. The influence of the electron relaxation, due to mutual electrons collisions, on the electron dynamics is taken into account. We investigate the growth characteristics of Cerenkov laser operating in the small-signal and saturation regimes. In the saturation regime, the effect of velocity reduction of the electron beam on the gain dynamics is demonstrated. We also show that our results match with those of other well-known treatments in the small-signal gain limit.

Section: B Numerical Examples and Discussionmentioning

confidence: 99%

Section: àW=2mentioning

confidence: 99%

See 1 more Smart Citation

Analysis of saturation phenomena in Cerenkov free-electron lasers with a planar waveguide

Yamada

2011

Physics of Plasmas

“…We also estimated the spreading length of an electron wave in our experiment to be 20 to 40 m μ by comparing the experimentally obtained emission profile with theoretical analysis [18,19].…”

Section: Introductionmentioning

confidence: 97%

Criterion of applicable models for planar type Cherenkov laser based on quantum mechanical treatments

Yamada

Nuclear Instruments and Methods in Physics Research Section A:

2013

A generalized theoretical analysis for amplification mechanism in the planar-type Cherenkov laser is given. An electron is represented to be a material wave having temporal and spatial varying phases with finite spreading length. Interaction between the electrons and the electromagnetic (EM) wave is analyzed by counting the quantum statistical properties. The interaction mechanism is classified into the Velocity and Density Modulation (VDM) model and the Energy Level Transition (ELT) model basing on the relation between the wavelength of the EM wave and the electron spreading length. The VDM model is applicable when the wavelength of the EM wave is longer than the electron spreading length as in the micro-wave region. The dynamic equation of the electron, which is popularly used in the classical Newtonian mechanics, has been derived from the quantum mechanical Schrödinger equation.The amplification of the EM wave can be explained basing on the bunching effect of the electron density in the electron beam. The amplification gain and whose dispersion relation with respect to the electron velocity is given in this paper. On the other hand, the ELT model is applicable for the case that the wavelength of the EM wave is shorter than the electron spreading length as in the optical region. The dynamics of the electron is explained to be caused by the electron transition between different energy levels. The amplification gain and whose dispersion relation with respect to the electron acceleration voltage was derived on the basis of the quantum mechanical density matrix.

“…5 It is assumed that the EM wave can interact only with the space-charge wave when the phase velocities of these waves become equal, and the EM wave satisfies the dispersion relation for the waveguide. 5 On the basis of classical 9,10 and quantum [11][12][13] approaches, the authors have shown that due to the asymmetric separations between electrons accompanied with the beam bunching, the asymmetric Coulomb forces exerted on an electron by the neighboring electrons work to recover its initial position. Therefore, the unbalanced Coulomb forces work to weaken (relax) the bunching mechanism.…”

Section: Introductionmentioning

confidence: 99%

Unified analysis for calculating the amplification gain of Cerenkov laser in the single-particle and collective regimes

2012

Physics of Plasmas

In this paper, we introduce a unified analytical model to describe both the single-electron and the collective modes of interaction in the Cerenkov laser. Although the basic formulations of the model are based on the single-electron interaction with the electromagnetic wave, the characteristics of the wave-wave interaction associated with the collective model are also determined. The transition regime between the single-electron and the collective models is explored. The electron relaxation effect caused by the asymmetric Coulomb forces among the electrons is taken into account. The essential results of this paper agree with those predicted by previous theories at the limits of the single-electron and collective.