A traveling-wave ring resonator with Bragg deflectors in a two-stage terahertz free-electron laser

Abstract

We propose a scheme of a two stage terahertz free electron laser (FEL) based on a Bragg travel ing wave ring resonator and parallel ribbon relativistic electron beams. The first beam moves in the field of a planar undulator and generates a pumping wave in the millimeter range. At the second stage, this wave trans forms into terahertz radiation in the course of intraresonator backscattering on the second parallel electron beam. The ring resonator consists of four Bragg deflectors, each deflecting radiation by 90° in the vicinity of Bragg resonance, thus closing the feedback ring of the low frequency pumping generator and simultaneously providing effective transfer of the pumping wave to the scattering stage.

Quasilinear theory of terahertz free-electron lasers based on Compton scattering of incoherent pump wave by intense relativistic electron beam

“…Let us estimate (see Table II) the possibility of using the considered mechanism of backscattering for the generation of terahertz radiation by an intense relativistic beam with a current J ¼ 450A, a mean particle energy 0.75 MeV (γ ¼ 2.5), and an energy spread Δγ=γ ¼ 7% (δ ¼ 0.035). In the considered case we can take a 70 GHz free-electron maser that is being developed at the accelerator ELMI (Budker Institute, Novosibirsk) [38,39] as a pump wave source. We assume that the total power of the pump wave is 100 MW, the spectrum width is 7% and the cross section of the interaction space is 4 mm 2 .…”

High-current THz-band gyrotrons based on axial-slit cavities

“…For instance, in [1], a 330 GHz surface-wave oscillator was studied with output power exceeding 40 MW fed by an electron beam with an energy of 380 keV and a current of 2.2 кА. In [2], prospects for realization of 2 THz planar free electron lasers with a multi-MW power were discussed. Currently, gyrotrons are known to be the highest-power CW radiation sources in THz band, as they feature high mode selectivity allowing for use the highly oversized electrodynamical systems [3].…”

Electrodynamic system for two-stage THz-generator on the base of two-channel planar FEM

“…To produce high-power THz-radiation few schemes of two-stage generators basing on this mechanism were suggested and investigated [2,3]. Theory predictsMW-power levelin THz-radiation pulse [3].To get the first experience the simple two-stage scheme similar to our experiments on mm-wave generation in twochannel planar FEM [4] was chosen. The idea is to use single channel of this planar FEM driven by the first sheet beam as a low frequency (LF) section of THzgenerator in which the following parameters of the radiation pulses have been achieved: frequency ~75 GHz, spectrum width ~20 MHz, pulse duration ~200 ns and power from single channel ~20 MW.…”

“…We study such mechanism of spatial synchronization of electromagnetic oscillations for the case of a planar free electron maser (FEM) at the ELMI-device (BINP, Novosibirsk) [1]. To produce high-power THz-radiation few schemes of two-stage generators basing on this mechanism were suggested and investigated [2,3]. Theory predictsMW-power levelin THz-radiation pulse [3].To get the first experience the simple two-stage scheme similar to our experiments on mm-wave generation in twochannel planar FEM [4] was chosen.…”