Low-order-mode harmonic multiplying gyrotron traveling-wave amplifier in W band

Journal Article · Sat Sep 15 04:00:00 EDT 2012 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4751465· OSTI ID:22086156

Yeh, Y S; Chen, C H; Yang, S J; Lai, C H; Lin, T Y; Lo, Y C; Hong, J W ^[1]; Hung, C L ^[2]; Chang, T H ^[3]

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1. Department of Electro-Optical Engineering, Southern Taiwan University, Tainan, Taiwan (China)
2. Department of Communication Engineering, National Penghu University of Science and Technology, Penghu, Taiwan (China)
3. Department of Physics, National Tsing Hua University, Hsinchu, Taiwan (China)

Harmonic multiplying gyrotron traveling-wave amplifiers (gyro-TWAs) allow for magnetic field reduction and frequency multiplication. To avoid absolute instabilities, this work proposes a W-band harmonic multiplying gyro-TWA operating at low-order modes. By amplifying a fundamental harmonic TE{sub 11} drive wave, the second harmonic component of the beam current initiates a TE{sub 21} wave to be amplified. Absolute instabilities in the gyro-TWA are suppressed by shortening the interaction circuit and increasing wall losses. Simulation results reveal that compared with Ka-band gyro-TWTs, the lower wall losses effectively suppress absolute instabilities in the W-band gyro-TWA. However, a global reflective oscillation occurs as the wall losses decrease. Increasing the length or resistivity of the lossy section can reduce the feedback of the oscillation to stabilize the amplifier. The W-band harmonic multiplying gyro-TWA is predicted to yield a peak output power of 111 kW at 98 GHz with an efficiency of 25%, a saturated gain of 26 dB, and a bandwidth of 1.6 GHz for a 60 kV, 7.5 A electron beam with an axial velocity spread of 8%.

• OSTI ID: 22086156
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 9 Vol. 19; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ABSOLUTE INSTABILITIES
BEAM CURRENTS
EFFICIENCY
ELECTRON BEAMS
GHZ RANGE
GYROFREQUENCY
HARMONICS
MAGNETIC FIELDS
MICROWAVE AMPLIFIERS
PLASMA SIMULATION
TRAVELLING WAVES