Conference Paper
Dynamics of Axial Mode Competition in the Gyrotron BackwardWave Oscillator
Dept. of Phys., Nat. Tsing Hua Univ., Hsinchu
DOI: 10.1109/PLASMA.2005.359068
Conference: Plasma Science, 2005. ICOPS '05. IEEE Conference Record  Abstracts. IEEE International Conference on
Source: IEEE Xplore
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TsunHsu Chang, Aug 18, 2014 Available from:
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ABSTRACT: We report the experimental operation of a voltage tunable gyrotron backward wave oscillator (gyroBWO) in the frequency range near 140 GHz. Voltage tunability is an important feature of the gyroBWO for application as a fast tuning source for driving high power free electron lasers or cyclotron autoresonance maser amplifiers. The gyroBWO operated in an overmoded cylindrical waveguide structure in the TE1,2 mode. The electron beam source was a Piercewiggler gun producing an 80 kV, 6.2 A beam. Frequency tuning with voltage between 134 and 147 GHz was achieved in the TE1,2 mode with constant magnetic field. However, this tuning was found to be discontinuous. Output powers of up to 2 kW and 2% efficiency were found, significantly below theoretical predictions for a cold beam. The theoretical beam velocity spread was modeled by a 3D beam transport code. The code results show that space charge forces, coupled with the wigglerinduced helical motion and the short cyclotron wavelength of the beam, produce large increases in velocity spread in the magnetic compression region. A beam with smaller velocity spread would be needed to make the gyroBWO operate at the desired efficiency.International Journal of Infrared and Millimeter Waves 01/1995; 16(5):889905. DOI:10.1007/BF02066664 · 0.67 Impact Factor 
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ABSTRACT: Operation of a continuous wave gyrotron backwardwave oscillator (gyroBWO) with a helically rippled operating waveguide has been experimentally studied. The gyroBWO exploits a dc oilcooled magnet with magnetic field up to 0.5 T and utilizes a weakly relativistic (20 keV) electron beam produced by a magnetron injection gun. Stable generation at the second cyclotron harmonic with a maximum power of 7 kW and an efficiency of 15% at a frequency of 24.7 GHz was achieved. Smooth oscillation frequency tuning by varying the magnetic field was measured to be as wide as 5% at the halfpower level. The first gyroBWO operation with a singlestage energy recovery system was realized. The use of a depressed collector provided an efficiency increase up to 23% and an opportunity for reduction of the main power supply voltage down to 10 kV.IEEE Transactions on Plasma Science 07/2004; DOI:10.1109/TPS.2004.828871 · 0.95 Impact Factor