Y. Hirata

Theory and experiment of a 94 GHz gyrotron traveling-wave amplifier

Experimental results are presented on the first W-band gyrotron Traveling-Wave Tube (gyro-TWT) developed to exploit the 94 GHz atmospheric window for long-range, high-resolution radar applications. The gyro-TWT is designed to operate in the higher order TE01 mode and is driven by a 100 kV, 5 A electron beam with a pitch angle of v⊥/vz=1 and velocity spread of Δvz/vz=5%. Large-signal simulations predict 140 kW output power at 92 GHz with 28% efficiency, 50 dB saturated gain, and 5% bandwidth. The stability of the amplifier against spurious oscillations has been checked with linear codes. To suppress the potential gyro-BWO interactions involving the TE02, TE11, and TE21 modes, the interaction circuit with a cutoff frequency of 91 GHz has been loaded with loss so that the single-path, cold-circuit attenuation is 90 dB at 93 GHz. A coaxial input coupler with 3% bandwidth is employed with a predicted and measured coupling of 1 dB and 2 dB, respectively. The operating voltage is limited to below 75 kV because o...

Efficient Ka-band second-harmonic slotted peniotron

A harmonic peniotron has been designed for high efficiency and relative immunity to mode competition from gyrotron interactions. The device employs a 70-kV, 3.5-A, axis-encircling electron beam. To ensure stability from competing gyrotron interactions, the peniotron will operates in the lowest-order mode of a slotted four-vane circuit, the /spl pi//2-mode. The cavity is strongly diffraction coupled for a high circuit efficiency. The 33-GHz, slotted second-harmonic peniotron is predicted to yield 125 kW with an electron efficiency of 58% and a device efficiency of 52%. The device is being constructed at the University of California at Davis and is driven by a recently developed Northrop Grumman (Rolling Meadows, IL) cusp electron gun.

High power harmonic gyro-TWT amplifiers in mode-selective circuits

A second-harmonic gyro-TWT amplifier operating in the circular TE31 mode is described that is predicted to generate 400 kW at 35 GHz with 20% efficiency, 35 dB large-signal gain and 4.5% saturated bandwidth. The mode-selective interaction circuit is sliced to suppress electromagnetic modes without m=3 symmetry.

Slotted W-band sixth-harmonic gyrotron with axis-encircling electrons

A high-harmonic slotted gyrotron is under construction at UCD that will be driven by a 70 kV, 3.5 A, axis-encircling electron beam from a Northrop Grumman Cusp gun. The 94 GHz, slotted sixth-harmonic gyrotron is predicted to generate 40 kW with a device efficiency of 16%.

Highly efficient 34 GHz peniotron

While high conversion efficiency has been demonstrated in peniotrons, practical application of the device requires that power be efficiently extracted from the cavity. The UCD peniotron is designed to achieve high overall device efficiency and power output (130 kW peak) by employing an over-coupled cavity driven by a Northrop Grumman Cusp gun. Stability is insured through the use of a fundamental-mode interaction with the second cyclotron harmonic of the axis-encircling electron beam.

Design of a heavily-loaded W-band TE/sub 01/ gyro-TWT

A high average power gyro-TWT operating in the low-loss TE/sub 01/ mode is being constructed at UCD that will be driven by a 100 kV, 5 A, v/sub /spl perp///v/sub z/=1.0 MIG electron beam with /spl Delta/v/sub z//v/sub z/=5%. The single-stage amplifier is predicted by a large-signal simulation code to generate 145 kW at 94 GHz with 29% efficiency, 54 dB saturated gain and 5% bandwidth.

Highly efficient Ka-band second-harmonic slotted peniotron

A harmonic peniotron has been designed for high efficiency and relative immunity to mode competition from gyrotron interactions. The device employs a 70 kV, 3.5 A, axis-encircling electron beam. To ensure stability from competing gyrotron interactions, the peniotron will operate in the lowest order mode of a slotted four-vane circuit, the /spl pi//2 mode. The 33 GHz, slotted second-harmonic peniotron is predicted to yield 125 kW with an electron efficiency of 58% and a device efficiency of 52%. The device is being constructed at UCD and will be driven by a recently developed Northrop Grumman Cusp electron gun.

W-band TE/sub 01/ gyro-TWT with heavy wall loss

A high average power gyro-TWT operating in the low-loss TE/sub 01/ mode is being constructed that will be driven by a 100 kV, 5 A, v/sub /spl perp///v/sub z/=1.0 MIG electron beam with /spl Delta/v/sub z//v/sub z/=5%. The single-stage amplifier is predicted by a large-signal simulation code to generate 145 kW at 94 GHz with 29% efficiency, 54 dB saturated gain and 5% bandwidth.

Cusp gun driven peniotron

The UCD peniotron has been designed for optimum device efficiency and output power in second-harmonic operation at a 34 GHz fundamental-mode resonance. Key to the design is interaction with the axis-encircling electron beam. The UCD device incorporates over-coupling of the cavity to achieve the desired increased device efficiency. The predicted efficiency and power have been calculated from our large signal code.

34 GHz cusp gun driven peniotron

Summary form only given. A peniotron designed for optimum device efficiency is currently being assembled at UC Davis. The peniotron incorporates a four-vane slotted (magnetron-like) cavity operating in the fundamental waveguide mode, the /spl pi//2 mode. Interaction is at approximately 34 GHz with the second-harmonic beam mode. This interaction provides good separation from possible competing gyrotron modes. The cavity incorporates an output coupling iris which is required to achieve the desired loaded Q of 375 necessary for overcoupling of the device and optimum power output. The predicted output power is approximately 125 kW (at 47% device efficiency as predicted with our large-signal code). Cold test of the cavity/iris combination shows good agreement with predictions from simulation with HFSS. The interaction is powered by a Northrop-Grumman cusp gun which provides the high quality axis-encircling electron beam required for efficient interaction. For the device to operate as predicted, the gun will supply 3.5 amps at 70 kV. The spent beam should be suitable for recovery with a single-stage depressed collector, raising the total device efficiency to 57%.