A fast switch, combiner and narrow-band filter for high-power millimetre wave beams

A fast directional switch (FADIS) is described, which allows controlled switching of high-power microwaves between two outputs. A possible application could be synchronous stabilization of neoclassical tearing modes (NTMs). Generally, the device can be used to share the installed EC power between different types of launchers or different applications (e.g. in ITER, midplane/upper launcher). The switching is performed electronically without moving parts by a small frequency-shift keying of the gyrotron (some tens of megahertz), and a narrow-band diplexer. The device can be operated as a beam combiner also, which offers attractive transmission perspectives in multi-megawatt ECRH systems. In addition, these diplexers are useful for plasma diagnostic systems employing high-power sources due to their filter characteristics. The principle and the design of a four-port quasi-optical resonator diplexer is presented. Low-power measurements of switching contrast, mode purity and efficiency show good agreement with theory. Preliminary frequency modulation characteristics of gyrotrons are shown, and first results from high-power switching experiments using the ECRH system for W7-X are presented.

[1]  A. F. Krupnov,et al.  Gyrotron frequency control by a phase lock system , 2006 .

[2]  G. Gantenbein,et al.  High-power tests of a remote steering Launcher mock-up at 140 GHZ , 2004 .

[3]  A. Bruschi,et al.  Beam Combination and Routing at High Power with a Ring-Type Waveguide Millimeter-Wave Resonator , 2008 .

[5]  M. Thumm,et al.  Fast Switching and Power Combination of High-Power Electron Cyclotron Wave Beams: Principles, Numerical Results, and Experiments , 2007 .

[6]  I. Turchin,et al.  A diplexer based on an open resonator with corrugated mirrors , 2005 .

[7]  M. A. Shapiro,et al.  Study of combined transmission line for high power wave generated by a gyrotron in the millimetre wavelength range , 1992 .

[8]  W. Kasparek,et al.  FADIS: Project for Fast Directional Switching of Discrete High Power Millimeter Wave Beams , 2006, 2006 Joint 31st International Conference on Infrared Millimeter Waves and 14th International Conference on Teraherz Electronics.

[9]  T. Antonsen,et al.  Effect of window reflection on gyrotron operation , 1992 .

[10]  H. Zohm,et al.  Cross–machine benchmarking for ITER of neoclassical tearing mode stabilization by electron cyclotron current drive , 2006 .

[11]  P. Brand,et al.  Circuit design and simulation of a HV-supply controlling the power of 140 GHz 1 MW gyrotrons for ECRH on W7-X , 2003 .

[12]  Manfred Thumm,et al.  Passive high-power microwave components , 2002 .

[13]  G. Gantenbein,et al.  Electron Cyclotron Heating for W7-X: Physics and Technology , 2007 .

[14]  A. Chirkov,et al.  Minimization of Diffraction Losses in Big Gaps of Multi-Mode Waveguides , 2005 .

[15]  R. Ulrich,et al.  Self‐imaging in homogeneous planar optical waveguides , 1975 .

[16]  Sergey V. Kuzikov.  Wavebeam Multiplication Phenomena to RF Power Distribution Systems of High-Energy Linear Accelerators , 1998 .

[17]  G. Gantenbein,et al.  Experiments on neoclassical tearing mode stabilization by ECCD in ASDEX Upgrade , 1999 .

[18]  M. Schmid,et al.  EU Megawatt-Class 140-GHz CW Gyrotron , 2006, IEEE Transactions on Plasma Science.

[19]  H Melchior,et al.  General self-imaging properties in N × N multimode interference couplers including phase relations. , 1994, Applied optics.

[20]  Michael I. Petelin,et al.  Quasi‐Optics In High Power Millimeter Wave Systems , 2003 .