Yi-Nong Su

Initial experimental results of a new triplet harmonic-multiplying gyrotron amplifier (Gyrotriotron)

A new triplet gyrotron amplifier, which we call gyrotriotron, has recently been developed. The device consists of a gyroTWT input stage to modulate the beam at S/sub 1/=1 cyclotron harmonic, a four-unit clustered-cavity as intermediate stage to bunch the beam at S/sub 2/=2 cyclotron harmonic and a gyro-TWT output stage to extract energy from the bunched beam at S/sub 3/=2 cyclotron harmonic. Electronic coupling between neighboring stages is realized through ballistic beam bunching in the radiation-free drift space similar to what happens in a gyroklystron. Because S/sub 3/ = S/sub 2/ = 2S/sub 1/, the device is a harmonic multiplying gyrotron amplifier with a scheme of 1-2-2. The clustered-cavity employed in the gyrotriotron is a group of TE/sub 03/ mode-selected cavities, which are closely adjacent and without any coupling between them.

A new triplet gyrotron amplifier, the gyrotriotron

Summary form only given. A new triplet gyrotron amplifier, which we call gyrotriotron, has recently been developed. The device consists of a gyro-TWT input stage to modulate the beam at S/sub 1/=1 cyclotron harmonic, a four-unit clustered-cavity as intermediate stage to bunch the beam at S/sub 2/=2 cyclotron harmonic and a gyro-TWT output stage to extract energy from the bunched beam at S/sub 3/=2 cyclotron harmonic. Electronic coupling between neighboring stages is realized through ballistic beam bunching in the radiation-free drift space similar to what happens in a gyroklystron. Since S/sub 3/=S/sub 2/=2S/sub 1/, the device is a harmonic multiplying gyrotron amplifier with a scheme of 1-2-2. The clustered-cavity employed in the gyrotriotron is a group of TE/sub 03/ mode-selected cavities, which are closely adjacent and without any coupling between them. HFSS simulation of a sub-unit of such a mode selective clustered-cavity is given. This is a first use of cluster cavity in a gyrotron. The proof-of-principle gyrotriotron with Ku-band input, Ka-band TE/sub 04/ mode output, predicted peak output power of 500 kW and 5% bandwidth, has been fabricated and is being tested in the Harmonic Gyrotron Lab at University of Maryland.

Particle simulation of a ka-band gyrotron traveling wave amplifier

The design of a ka-band gyrotron traveling wave (gyro-TWT) amplifier is presented. The gyro-TWT amplifier with a severed structure operates in the fundamental harmonic TE01 circular electric mode. The beam-wave interaction is studied by using a particle-in-cell (PIC) code. The simulations predict that the amplifier can produce an output peak power of over 155 kW, 22% efficiency, 23 dB gain, and a 3 dB bandwidth of 2 GHz for a 70 kV, 10 A electron beam with an axial velocity spread Δvz/vz=5%.

Recent Results in the Development of a Ka-Band Second Harmonic Gyroklystron Amplifier

High-power coherent millimeter-wave sources have been extensively studied for many applications including high-resolution radars, millimeter-wave electronic counters measures, material processing, and high- energy particle accelerators. This paper presents some recent experiment results in the development of this gyroklystron at IECAS.

Study of a Quasi-Optical Mode Converter for W-band Gyrotron Oscillator

A quasi-optical mode converter for a W-band TE02 mode gyrotron is designed, fabricated, and tested. The system consists of a step-cut waveguide launcher (cut-in-half circular waveguide) and a doubly curved reflector (an elliptical reflector and a parabolic reflector). Based on the geometric optics principle and the vector diffraction theory, the mode converter is optimized and simulated by using numerical calculations. The simulation results show that the good Gaussian mode is converted from the circular waveguide TE02 mode, and the conversion efficiency is 77.9%. Experimental measurements are performed on a quasi-continuous wave gyrotron operating in the TE02 mode at W-band and show a good agreement with theoretical predictions.

A Ka-Band Second Harmonic Gyroklystron Amplifier

The design and experiment of a ka-band second harmonic gyroklytron amplifier are reported. The three-cavity 35-GHz second harmonic gyroklystron operates in the TE021 circular electric mode. Based on the numerical simulation, a three-cavity, second harmonic gyroklystron amplifier prototype has been fabricated. Experiments show a peak output power of 212 kW at 35 GHz with a 3-dB bandwidth of 155 MHz (0.44%) when utilizing a 58 kV, 23 A, v⊥/vP = 1.45 electron beam from a magnetron injection gun. The efficiency is approximately 16%, and the gain is about 24 dB.

Experimental studies of a Ka-band second harmonic gyroklystron amplifier

The recent experimental results of a Ka-band second harmonic gyroklystron amplifier are presented. The peak output power of 212kW at 35GHz has been measured with a 3dB bandwidth of 155MHz. The tube is operated at electron beam voltage and current of 58 kV and 23 A, respectively. The efficiency is approximately 16% and the gain is about 24 dB.

Design and simulation of the interaction circuit for a W-band quasi-optical gyrotron oscillator

In this paper, the design and simulation of a high-frequency structure for a W-band quasi-optical gyrotron oscillator, which operates at the TE62 mode, has been presented. According to the self-consistent nonlinear theory, the parameters of the high-frequency resonator has been designed and optimized. The effects of electron beam voltage, current, velocity spread, magnetic field and electron beam guiding center on the output power and efficiency have been analyzed. The maximum output power and efficiency of the designed gyrotron oscillator is about 39.7kW and 44.1%, respectively.

Design of the magnetron injection gun for W-band gyrotron oscillator

In this paper, the design of a magnetron injection gun (MIG) with a single-anode built for W-band gyrotron oscillator is presented. The simulation of the MIG is finished with the help of a trajectory program EGUN. The simulation results indicate that the velocity ratio with velocity spread of less than 4% is 1.41.

Design and experiment of the conventional collector for W-band gyrotron oscillator

In this paper, the design and experiment of the conventional electron beam spreading system for W-band gyrotron oscillator collector is presented. The conventional spread system consists of a magnetic shade and two pairs of coils. The particle-in-cell (PIC) simulation of the collector under the conventional spreading system has been finished. The power density distribution of the electron beam on the collector wall has been measured in the hot test of the gyrotron oscillator.