Effects of tapering on gyrotron backward-wave oscillators

Journal Article · Sat Jun 01 00:00:00 EDT 1996 · IEEE Transactions on Plasma Science

DOI:https://doi.org/10.1109/27.532947· OSTI ID:377822

Walter, M T; Gilgenbach, R M; Luginsland, J W; Hochman, J M; Rintamaki, J I; Jaynes, R L; Lau, Y Y; Spencer, T A ^[1]

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1. Univ. of Michigan, Ann Arbor, MI (United States). Intense Energy Beam Interaction Lab.

Computer modeling has been utilized to guide gyrotron backward-wave oscillator (gyro-BWO) experiments at the University of Michigan over a wide range of tapered interaction regions and tapered magnetic fields. E-GUN code is used to examine beam and diode characteristics, while MAGIC is used to analyze the dynamics of the problem, such as particle kinematics and microwave power production. Several innovative techniques are used to create matching boundary conditions for a backward propagating wave. MAGIC simulations predict optimum performance of the gyro-BWO operating in a TE{sub 01} mode within a combination of uniform interaction region and a tapered axial magnetic field which increases 7.5% in the direction of beam propagation. Experiments have been performed to investigate the effects of tapering magnetic fields and tapered interaction region radii on the high-power microwave emission from the gyro-BWO over the frequency range from 4.0 to 6.0 GHz. These experiments were performed on the Michigan Electron Long-Pulse Accelerator (MELBA). Tapered interaction regions of 37%, 23%, 9.4%, and 6.4% were built and tested to determine their effect on microwave power, pulselength, and inferred energy compared to the uniform interaction region. Magnetic tapering trim coils with a range of {minus}10.6% < {Delta}B/B{sub o} < +15.0% were constructed which allow the orientation of the field taper to be changed without breaking the vacuum. The peak microwave power from individual shots was from 30 to 55 MW. Experiments on magnetic field tapering indicate that positive tapered fields improve microwave power and energy output.

• OSTI ID: 377822
• Journal Information: IEEE Transactions on Plasma Science, Vol. 24, Issue 3; Other Information: PBD: Jun 1996
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING NOT INCLUDED IN OTHER CATEGORIES
BACKWARD WAVE TUBES
PERFORMANCE
MAGNETIC FIELD CONFIGURATIONS
MICROWAVE AMPLIFIERS
COMPUTERIZED SIMULATION
BEAM DYNAMICS
OSCILLATION MODES