Title :
Long-pulse, high-power, large-orbit, coaxial gyrotron oscillator experiments
Author :
Jaynes, Reginald Lamar ; Gilgenbach, Ronald M. ; Peters, C.W. ; Cohen, W.E. ; Lopez, M.R. ; Lau, Y.Y. ; Williams, W.J. ; Spencer, Thomas A.
Author_Institution :
Intense Energy Beam Interactions Lab., Michigan Univ., Ann Arbor, MI, USA
fDate :
6/1/2000 12:00:00 AM
Abstract :
Long-pulse, large-orbit, coaxial gyrotrons are currently under investigation. The electron beam is generated by the Michigan Electron Long Beam Accelerator (MELBA) with parameters: V=-0.8 MV, Ianode ⩽~4 kA, Itube=0.2-2 kA, and pulse length=0.5-1 μs. Large-orbit, axis-encircling electron beams are generated by a magnetic cusp. Experimental gyrotron performance with coaxial cavities (unslotted and slotted) is compared to a noncoaxial cavity. The coaxial gyrotron demonstrated superior current transport and microwave production over the noncoaxial gyrotron. The coaxial rod apparently raises the limiting electron beam current in the diode, allowing higher currents to be extracted. The unslotted, coaxial gyrotron showed microwave power levels of 20-40 MW with pulse lengths of 10-40 ns, This coaxial gyrotron operated in two main modes: TE111 and TE112 with frequencies of 2.34 and 2.5 GHz, respectively. The gyrotron frequency is tunable between the respective modes by changing the magnetic field. The slotted, coaxial gyrotron showed the highest power of 60-90 MW and extremely short pulse lengths of 10-15 ns. For all three gyrotrons, the microwave pulse-shortening mechanisms of mode hopping and mode competition are definitively identified by time-frequency analysis of heterodyned microwave data
Keywords :
electron accelerators; gyrotrons; microwave oscillators; -0.8 MV; 0.2 to 2 kA; 0.5 to 1 mus; 10 to 40 ns; 2.34 GHz; 2.5 GHz; 20 to 40 MW; 4 kA; Michigan Electron Long Beam Accelerator; TE111 mode; TE112 mode; coaxial gyrotron; coaxial rod; current transport; electron beam generation; gyrotron performance; heterodyned microwave data; large-orbit axis-encircling electron beams; limiting electron beam current; long-pulse high-power large-orbit coaxial gyrotron oscillator experiments; magnetic cusp; microwave power levels; microwave production; microwave pulse-shortening mechanisms; mode competition; mode hopping; noncoaxial cavity; noncoaxial gyrotron; pulse length; pulse lengths; slotted coaxial cavities; time-frequency analysis; unslotted coaxial cavities; unslotted coaxial gyrotron; Anodes; Coaxial components; Electron accelerators; Electron beams; Frequency; Gyrotrons; Oscillators; Particle beams; Pulse generation; Tellurium;
Journal_Title :
Plasma Science, IEEE Transactions on
