Chongqing Jiao

Linear theory of the electron cyclotron maser based on TM circular waveguide mode

A linear theory of the electron cyclotron maser, which is applicable to any TM circular waveguide mode, is developed by using Laplace transforms. This theory can be used to analyze the linear behaviors of both the TM mode gyrotron traveling wave tube (gyro-TWT) and the TM mode gyrotron backward wave oscillator (gyro-BWO). Numerical results show that, although the TM mode is less effective than the TE mode for the gyro-TWT interaction, the TM mode may be as effective as the TE mode for the gyro-BWO interaction, even in the case of weak relativistic electron energy.

Linear and nonlinear analysis of a gyrotron traveling wave amplifier with misaligned electron beam

This paper presents linear and self-consistent nonlinear theories to describe the beam-wave interaction in a gyrotron traveling wave amplifier (gyro-TWA) with a misaligned electron beam. A linear theory based on the linearized Vlasov equations is developed by using Laplace transforms. By setting appropriate initial values of the electron guiding center, the nonlinear theory without misalignment can be used to study the misalignment effect. The two theories are in good agreement in the small-signal region for the gyro-TWA. The effects of beam misalignment on the TE01 mode gyro-TWA operating at the fundamental are discussed and the corresponding physical mechanism is analyzed.

Effect of the lossy layer thickness of metal cylindrical waveguide wall on the propagation constant of electromagnetic modes

Based on the dispersion equation of electromagnetic mode, the propagation problem in a lossy cylindrical waveguide is studied. The analytic formula of propagation constant for any mode in the waveguide is presented, which includes the effect of the lossy layer thickness on the waveguide wall. The analysis with the analytic formula shows that the lossy layer thickness has great effect on the propagation constant when the thickness is 1.5 times smaller than the skin depth of good conductor (δ).

Operation of a Ka-band Harmonic-Multiplying Gyrotron Traveling-Wave Tube

Amplification studies of a Ka-band harmonic-multiplying gyrotron traveling-wave tube (gyro-TWT) are reported. A coupled cavity with inner- and outer-intersecting couplings and precise control of the focusing magnetic field are used to improve the coupling between the fundamental and the harmonic and to adapt the sensitivity of the effect of focusing magnetic field on the beam-wave interaction in the gyro-TWT to high-order mode operation. Experimental results show that 75 kW of peak output power with a bandwidth of 1.06% and a gain of more than 25 dB can be reached at a pulse voltage of 67.2 kV and a pulse current of 15.8 A.

Experimental Study of a Ku-Band Gyrotron Backward-Wave Oscillator With a Single Stage Depressed Collector

The experiment on a Ku-band gyrotron backward- wave oscillator (gyro-BWO) with a single depressed collector and linear polarization mode output has been performed successfully. Stable magnetic tuning bandwidth of 5% and maximum power of 48 kW under a 40-kV 11.5-A electron beam were achieved. The overall efficiency of the gyro-BWO with a single stage depressed collector has been enhanced from 10.5% to 21%. The measured performance has demonstrated a strong potential of the gyro-BWO for new application requiring high-power tunable wave source.

First Experiment and Design of a Harmonic Multiplying Gyrotron Traveling Wave Amplifier with the TE02 Mode Output

A harmonic multiplying gyrotron traveling wave amplifier with the TE02 mode output has been designed in Institute of Electronics, Chinese Academy of Science (ECAS). First experimental results showed that the tube could stably amplify input signal, the output frequency bandwidth of more 500 MHz (33.02-33.524 GHz) had been reached at output pulse power of 10.07~12.88 kW, beam voltage of 60 kV, beam current of 11 A.

A Harmonic Multiplying Gyrotron Traveling Wave Amplifier with the TE02 Mode Output

For a gyro-amplifier, harmonic multiplying can lower the applied magnet field and more easily get RF driver. Theoretical studies and numerical simulation had been made in the references (G.S. Nusinovich et al., 2001), (K.R. Chu et al., 1997), (A.T. Lin et al., 2002) for the amplifier. Experimental results ever reported for a third-harmonic multiplying gyrotron travel wave amplifier (Chan-Wook Baik et al., 2005). In this paper, the simulations, designs and experimental results of a second-harmonic multiplying gyrotron traveling wave amplifier with the TE02 mode output was discussed.

Research progress of the harmonic multiplying gyrotron traveling wave amplifier at Ka band in IECAS

In this article, a new method is utilized for enhacing output power and improving bandwidth. The works related to harmonic multiplying gyrotron traveling wave amplifier were ever reported by us in IRMMW2006 and IVEC2007, which showed that there were some contradictions between output power and band-width. The output frequency bandwidth of more 500 MHz can be reached at output pulse power of only 10.07~12.88kW. Output pulse power can be increased to 25 kW with very narrow bandwidth. Because of using harmonic multiplying, the resonant circuit is usually used to increase the coupling between fundamental and harmonic. However, it will decrease operating bandwidth.

Linear and nonlinear theories of a large-orbit gyrotron traveling wave amplifier

The linear and nonlinear theories of large-orbit gyrotron traveling wave amplifiers (gyro-TWAs) have been developed based on the corresponding theories of small-orbit gyro-TWAs. The linear theory is in good agreement with the nonlinear theory in the small signal region of large-orbit gyro-TWAs. The phenomenon that most electrons move toward the axis of interaction circuit during the beam-wave interaction is observed and its potential effect on the design of large-orbit coaxial gyro-TWAs is emphasized.

A harmonic multiplying gyrotron traveling wave amplifier at Ka band developed in IECAS

The works related to harmonic multiplying gyrotron traveling wave amplifier were ever reported by us in IRMMW2006 and IVEC2007, which showed that there were some contradictions between output power and band-width.[1, 2] In [1], the output frequency bandwidth of more 500 MHz can be reached at output pulse power of only 10.07~12.88kW. In [2], output pulse power can be increased to 25kW with very narrow bandwidth. Because of using harmonic multiplying, the resonant circuit is usually used to increase the coupling between fundamental and harmonic. However, it will decrease operating bandwidth. In this article, a new method is utilized for enhacing output power and improving bandwidth.