Abstract-Power enhancement via an ion-channel in a Raman free-electron laser

Xiaoli Huang,  Shi-Chang Zhang,

http://iopscience.iop.org/article/10.1088/1555-6611/aacb09/meta

As a high-power and high-efficiency coherent radiation source, the free-electron laser extends to two unique spectra: the region in the ultra-violet, x- and -rays, and the range in the millimeter- and terahertz-waves. Based on credible simulations, it is shown that the nonlinear power of a Raman free-electron laser in a millimeter wave range goes up and gets an increase of at least 9% when an ion-channel is applied to the beam-wave interaction chamber. A physical explanation is that the ion-channel weakens the velocities spread over the electron beam and, therefore, improves the electron-beam transportation quality and the beam-wave interaction.
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Abstract-An Ultrahigh-order-mode, Higher-harmonic Coaxial Gyrotron Oscillator in Sub-terahertz Wave Range

Hui-Bo Zhang,  Shi-Chang Zhang
http://link.springer.com/article/10.1007%2Fs10762-013-0026-z

A coaxial cavity gyrotron oscillator at a frequency of 0.34 THz is studied, which operates with a quite low magnetic field of 4.55 Tesla at the third cyclotron harmonic of the ultrahigh-order mode TE_43,4. Properly choosing the depth of the longitudinal corrugations on the inner rod and optimizing the electron-beam position significantly suppress the mode competition. Nonlinear multimode simulations show the feasibility of the single-mode operation with an output power of 163 kW by using an electron beam with a voltage of 70kV and a current of 30A, which corresponds to an interaction efficiency of 9.2 % with maxim density of ohmic losses 2.9 kW/cm².