15 research outputs found
Design of MW-Class Coaxial Gyrotron Cavities With Mode-Converting Corrugation Operating at the Second Cyclotron Harmonic
This article presents investigations on the design of coaxial gyrotron cavities with mode-converting corrugations, operating at the second harmonic of the electron cyclotron frequency with output power of the order of megawatts. The suppression of the competing modes interacting at the fundamental cyclotron frequency is achieved by the combination of a corrugated coaxial insert and mode-converting corrugation on the outer wall. The outer corrugation couples the key competing modes to lower order modes with reduced quality factor. The design steps, which form a generally applicable design procedure, are described in detail. As an illustrative example, the proposed procedure is used for the design of a cavity for a fusion-relevant, second-harmonic MW-class gyrotron, operating at 170 GHz with the TE 37,1837,18 mode. From the simulations, it is found that for the proposed design, this mode is excited with an output power of around/ ∼ 1.5 MW. Two additional paths for cavity optimization toward even higher output power are also presented
Recent experiments with the European 1MW, 170GHz industrial CW and short-pulse gyrotrons for ITER
The European Gyrotron Consortium (EGYC) is developing the European 1 MW, 170 GHz Continuous Wave (CW) industrial prototype gyrotron for ITER in cooperation with Thales Electron Devices (TED) and Fusion for Energy (F4E). This conventional, hollow-cavity gyrotron, is based on the 1 MW, 170 GHz Short-Pulse (SP) modular gyrotron that has been designed and manufactured by the Karlsruhe Institute of Technology (KIT) in collaboration with TED. Both gyrotrons have been tested successfully in multiple experiments. In this work we briefly report on the results with the CW gyrotron at KIT and we focus at the experiments at the Swiss Plasma Center (SPC). In addition, we present preliminary results from various upgrades of the SP tube that are currently tested at KIT
Eigenvalues and ohmic losses in coaxial gyrotron cavity
The authors present the mathematical analysis for the calculation of the
dispersion relation, the field distributions, and the ohmic losses for
TEm,p modes in an infinite coaxial waveguide with a longitudinally
corrugated insert. The method employed is based on an appropriate
eigenfunction expansion, and its main advantage is the very fast
convergence with a few spatial harmonics. The analysis is properly
extended to include tapered cavities with varying, in respect to the
z-coordinate, outer and/or inner radius. Numerical results are presented
for several tapered cavity geometries and compared with already
published methods
Investigation of Cylindrical Waveguides with Periodic Wedge-Shaped Azimuthal Corrugations Excited by TE Modes Using the FDTD Method
Modern gyrotron beam tunnels are rather complicated structures designed
to enhance the suppression of the parasitic oscillations, which may be
excited there. In some beam tunnel designs, azimuthal corrugations are
engraved on their walls to further improve the suppression of these
oscillations. In this work, we investigate the effect of the geometrical
properties of the corrugations on the propagation characteristics of TE
modes for the simplified model of a smooth waveguide with an azimuthally
corrugated region. For this structure, the scattering parameters are
calculated and the mode conversion is investigated with the in-house
FDTD code COCHLEA