Experimental results and numerical simulations of a high power 140 GHz gyrotron

Journal Article · Sat Oct 01 04:00:00 EDT 1994 · IEEE Transactions on Plasma Science (Institute of Electrical and Electronics Engineers); (United States)

DOI:https://doi.org/10.1109/27.338301· OSTI ID:6478743

Gantenbein, G; Borie, E; Dammertz, G; Kuntze, M; Piosczyk, B ^[1]; Nickel, H U; Thumm, M ^[2]

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1. Kernforschungszentrum Karlsruhe GmbH (Germany). Inst. fuer Technische Physik
2. Kernforschungszentrum Karlsruhe GmbH (Germany). Inst. fuer Technische Physik Univ. Karlsruhe (Germany). Inst. fuer Hoechstfrequenztechnik und Elektronik

Gyrotrons have been used successfully for electron cyclotron resonance heating (ECRH) experiments of fusion plasmas for some time. Due to the localized energy deposition of ECR-waves the temperature profile can be modified and the stability of the plasma can be improved. ECRH has become an important additional heating technique combined with other methods which primarily heat ions, such as neutral beam injection (NBI) and ion cyclotron resonance heating (ICRH). One of the main problems which has hindered a wider application of ECRH is the availability of suitable sources at appropriate frequencies (100--300 GHz). The output power per unit source should be [approx gt]1 MW and the pulse length, which depends on the parameters of the special fusion machine, is in the range from several seconds to CW. Here, the design of a 0.5 MW 140 GHz gyrotron with axial RF output operating in the TE[sub 10,4] mode is presented. Experimental results and numerical simulations will be compared. In particular the effects of RF reflections at the output window, velocity spread of the helical electron beam and startup of oscillations by simultaneous increase of pitch factor [alpha] and relativistic factor [gamma] will be discussed. In short pulse operation ([le]5 ms) an output power of 690 kW has been obtained with an electronic efficiency of 31% and a mode purity of about 99%. The experiments have shown that it is possible to use for step frequency tuning the azimuthal neighbors of the TE[sub 10,4] mode, TE[sub 9,4] at 132.6 GHz (420 kW) and TE[sub 11,4] at 147.3 GHz (300 kW) as working modes by decreasing and increasing the magnetic field, respectively.

• OSTI ID: 6478743
• Journal Information: IEEE Transactions on Plasma Science (Institute of Electrical and Electronics Engineers); (United States), Journal Name: IEEE Transactions on Plasma Science (Institute of Electrical and Electronics Engineers); (United States) Vol. 22:5; ISSN ITPSBD; ISSN 0093-3813
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700460* -- Fusion Technology-- Heating & Fueling Systems
AMPLIFIERS
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
DATA
DESIGN
ECR HEATING
ELECTRONIC EQUIPMENT
EQUIPMENT
EVALUATION
EXPERIMENTAL DATA
Fu
Fuels-- (1992)
HEATING
HIGH-FREQUENCY HEATING
INFORMATION
MICROWAVE AMPLIFIERS
MICROWAVE EQUIPMENT
NUMERICAL DATA
OSCILLATION MODES
PERFORMANCE
PLASMA HEATING
RF SYSTEMS
SIMULATION
THEORETICAL DATA
THERMONUCLEAR DEVICES