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Title: Large-orbit coaxial-structure cyclotron autoresonance maser

Abstract

We present a conceptual proposal for a large-orbit coaxial-structure cyclotron autoresonance maser (CARM), wherein the rf structure is a coaxial waveguide or cavity and a large-orbit electron beam encircles the axis of the coaxial structure. Both dispersion analysis and nonlinear simulations demonstrate the feasibility of the proposal. The large-orbit coaxial-structure CARM could be expected to operate in millimeter and submillimeter wave ranges with high power, low operating magnetic field, and ultrahigh gain. It is found that electron-beam velocity spread substantially decreases the power of CARMs, but this adverse influence might be offset by a proper taper of the axial magnetic field.

Authors:
;  [1];  [2]
  1. China Center of Advanced Science and Technology (World Lab), P.O. Box 8730, Beijing 100080 (China) and Institute of Photoelectronics, Campus Mail Box 50, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China)
  2. (Germany) and Institute of High-Frequency Techniques and Electronics, University Karlsruhe, Kaiserstrasse 12, D-76128 Karlsruhe (Germany)
Publication Date:
OSTI Identifier:
20778630
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 88; Journal Issue: 3; Other Information: DOI: 10.1063/1.2166687; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CYCLOTRONS; DISPERSIONS; ELECTRON BEAMS; MAGNETIC FIELDS; MASERS; NONLINEAR PROBLEMS; ORBITS; SIMULATION; WAVEGUIDES

Citation Formats

Zhang Shichang, Thumm, Manfred, and Forschungszentrum Karlsruhe, Institute for Pulsed Power and Microwave Technology, Postfach 3640, D-76021 Karlsruhe. Large-orbit coaxial-structure cyclotron autoresonance maser. United States: N. p., 2006. Web. doi:10.1063/1.2166687.
Zhang Shichang, Thumm, Manfred, & Forschungszentrum Karlsruhe, Institute for Pulsed Power and Microwave Technology, Postfach 3640, D-76021 Karlsruhe. Large-orbit coaxial-structure cyclotron autoresonance maser. United States. doi:10.1063/1.2166687.
Zhang Shichang, Thumm, Manfred, and Forschungszentrum Karlsruhe, Institute for Pulsed Power and Microwave Technology, Postfach 3640, D-76021 Karlsruhe. Mon . "Large-orbit coaxial-structure cyclotron autoresonance maser". United States. doi:10.1063/1.2166687.
@article{osti_20778630,
title = {Large-orbit coaxial-structure cyclotron autoresonance maser},
author = {Zhang Shichang and Thumm, Manfred and Forschungszentrum Karlsruhe, Institute for Pulsed Power and Microwave Technology, Postfach 3640, D-76021 Karlsruhe},
abstractNote = {We present a conceptual proposal for a large-orbit coaxial-structure cyclotron autoresonance maser (CARM), wherein the rf structure is a coaxial waveguide or cavity and a large-orbit electron beam encircles the axis of the coaxial structure. Both dispersion analysis and nonlinear simulations demonstrate the feasibility of the proposal. The large-orbit coaxial-structure CARM could be expected to operate in millimeter and submillimeter wave ranges with high power, low operating magnetic field, and ultrahigh gain. It is found that electron-beam velocity spread substantially decreases the power of CARMs, but this adverse influence might be offset by a proper taper of the axial magnetic field.},
doi = {10.1063/1.2166687},
journal = {Applied Physics Letters},
number = 3,
volume = 88,
place = {United States},
year = {Mon Jan 16 00:00:00 EST 2006},
month = {Mon Jan 16 00:00:00 EST 2006}
}
  • Nonlinear simulations are presented to analyze the influences of the electron beam and the magnetic field parameters on the output power of a large-orbit coaxial-waveguide cyclotron autoresonance maser (CARM) amplifier. It is found that the guiding-center spread of the relativistic electrons has negligible impact on the output power due to the small field change felt by the large-orbit electrons. The electron-beam velocity spread and energy spread substantially decrease the output power, because these spreads directly affect the beam-wave interaction through the Doppler term and the relativistic cyclotron frequency term in the cyclotron resonance condition. However, this adverse effect may bemore » offset by properly tapering the operating magnetic field. The output power is sensitive to both the slope and the amplitude of the tapered magnetic field. Nonlinear simulation demonstrates the feasibility that a large-orbit coaxial-waveguide CARM amplifier can be expected to provide output power with several megawatts, ultrahigh gain, and good bandwidth in the millimeter and submillimeter wavelength ranges.« less
  • The interaction of transverse eigenmodes with a relativistic electron beam is analyzed in an overmoded cyclotron autoresonance maser amplifier, using a nonlinear self-consistent model and kinetic theory. It is shown that all of the coupled modes grow with the dominant unstable mode at the same growth rate, but suffer different launching losses. The phases of coupled modes are locked in the linear and nonlinear regimes. Simulations indicate that the rf power distribution among the interacting modes at saturation is {ital insensitive} to input power distribution but {ital sensitive} to detuning.
  • Studies of a cyclotron autoresonance maser are presented. The measurements are carried out at a frequency of 35 GHz using a mildly relativistic electron beam (1.5 MeV, 260 A) generated by a field emission electron gun followed by an emittance selector that removes the outer, hot electrons. Perpendicular energy is imparted to the electrons by means of a bifilar helical wiggler. Measurements give a small signal gain of 90 dB/m and a saturated power output of 10 MW. The corresponding electronic efficiency is 3%. Computer simulations are also presented.
  • The linear growth rate of an electron cyclotron autoresonance maser (CARM) with a phase filter, constructed by imposing a transverse magnetostatic wiggler, is derived from relativistic kinetic theory. The theoretical results confirm previous findings from computer simulation showing substantial enhancement of the growth rate near the autoresonance condition. This theory provides an additional, more readily accessible tool for designing a novel phase filter-assisted CARM. The mathematical formalism developed to treat the complex electron motion in this device is introduced.
  • A self-consistent, one-dimensional model of the cyclotron autoresonance maser (CARM) amplifier is developed, and numerical simulations based on this model are described. Detailed studies of the CARM gain and efficiency for a wide range of initial energy and velocity spreads are presented. The interaction efficiency is found to be substantially increased when the axial magnetic field is tapered. For example, efficiencies of greater than 41 percent are obtained for a 140-GHz CARM amplifier with a tapered axial magnetic field and a 700-kV 4.5-A electron beam with parallel velocity spreads of less than 1 percent. A discussion of the nonlinear bandwidthmore » and interaction sensitivity to axial field inhomogeneities is presented.« less