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The design of double anodes magnetron injection gun (MIG) for 3mm gyrotron is described in the paper. Based on the beam-wave interaction parameters in the gyrotron cavity, some structure parameters of the MIG are primarily designed by theory calculation. The simulation calculation using PIC code is done to verify the structure design of the MIG and to obtain some physical parameters of the electron movement. By the simulation, the electron parameters include 45kV voltage and 2.5A current and 1.6 velocity ratio for satisfy the beam-wave interaction.

The design for a 0.3 THz 400 W CW gyro-monotron is done and TE06 operating mode is chosen in the paper. The RF cavity mode field distribution and the diffraction Q value is optimized using HFSS software, so the starting current and operating magnetic field is chosen to restrain the mode competition. The simulation results including the peak output power 400 W and the electron efficiency 20% in the frequency spetrum 301.1 GHz are obtained by the beam-wave interaction simulation software.

The magnetic field solenoid is designed to satisfy for the positive-negative cusp magnetic field's distribution by the experiment and simulation. The cusp magnetic field makes electron doing the axis-encircling large-orbit movement. The current is measured in the thermionic cathode electric gun. An experiment method of measuring the electron velocity ratio is put forward by catching light spot when electron holding some energy shock at a fluorescence glass. By measuring the radius of the light spot, the velocity ratio is calculated in experiment. The error is about 15% compared with experiment and theory result. The experiment is accumulated for optimizing X-band second harmonic gyro-TWT using helical waveguide later.

The eigenwave dispersion of 8 mm 3-folded helical corrugation waveguide is simulated using CSL software. The electron beam 80 kV and main magnetic field 0.67 L are given by the eigenwave dispersion for Ka-band Gyro-LWL using helical waveguide. The beam-wave interaction procedure is simulated using a PIC code, in which LE11 and LE21 coupling mode transform and a right-rotating large-orbit electron bunch are obtained. The maximal output power is about 42.5 kW and the maximal gain is about 29.3 dB in 35 GHz. The 3 dB bandwidth is about 8.7% from 33 GHz to 35.8 GHz.

This paper investigates the effect of different distributions of magnetic fields on the magnetron performance, using the 3D version of the MAGIC code. The computer model of a ten-vane strapped magnetron used in microwave oven was set up, incorporating all the structure details, such as the helical cathode, output coupling circuit and magnetic pole pieces. The simulation of the magnetron performance was carried out using three different distributions of magnetic fields, i.e. the uniform distributed one (axial component only), the step distributed one and the real distribution obtained from computer modelling with the verification in measurement. The simulations show that with the uniform magnetic field, the performance of the magnetron in terms of oscillation start up time, frequency spectrum and stability is inferior compared with those using the non-uniformed magnetic fields. In fact the non-uniform magnetic field can substantially reduce the start up time and improve the frequency spectrum and stability. This observation suggests that non-uniformed magnetic field is a better choice for the magnetron operation, which challenges the conventional approach in magnetron design, in which a uniform magnetic field is always perused. Further experimental studies will be carried out to verify this result. (4 pages)

An experimental airborne laser bathymetry system has been developed and field trial has been conducted. The Q-switched and frequency-doubled Nd:YAG laser output is of 100 HZ pulse repetition rate, 2 MW peak power, 8 ns pulse width. The green light receiving telescope is transmissive with 1400 mm focal length and 200 mm aperture. The varying-gain control of PMT and logarithmic amplifier are used to compress the 105 dynamic range of received signals. The main features of data real-time processing subsystem are of 200 Ms/s sampling rate, 8 bit resolution, adjacent average treatment of return waveforms with high noise, and pseudo-color display of sea depth.