Li Zhenghong

Efficient Operation of an Oversized Backward-Wave Oscillator

Effective generation of high microwave pulsed power has been experimentally realized in an X-band oversized backward-wave oscillator. Special methods are taken for the mode control in the structure, whose minimum radius is significantly more than the cutoff radius. At last, a 5.4-GW output power is obtained in repetitively pulsed condition, while a 6.0-GW output power is obtained in singly pulsed condition.

Development of the relativistic backward wave oscillator with a permanent magnet

Firstly, an X-band relativistic backward wave oscillator with a low guiding magnetic field is simulated, whose output microwave power is 520 MW. Then, an experiment is carried out on an accelerator to investigate a relativistic backward wave oscillator with a permanent magnetic field whose strength is 0.46 T. When the energy of the electron is 630 keV and the current of the electron beam is 6.7 kA, a 15 ns width pulsed microwave with 510 MW output power at 8.0 GHz microwave frequency is achieved.

Experimental study on X-band repetitively oversized backward wave oscillator

A new type of high power microwave device is developed based on bitron and backward wave oscillator. The device is composed of two parts: the modulation cavity and the extraction cavity (which is similar to slow wave structure). The modulation cavity acts as electron beam modulator and microwave reflector, which forms a microwave resonator in combination of the extraction cavity. The electron is modulated when it passes through the modulation cavity, and the high power microwave is generated when the modulated beam passes through the extraction cavity. An X-band high power microwave device is designed for a 20 GW accelerator, and the simulation results are frequency 8.25 GHz and output power 5.70 GW. Using superconducting magnet as guiding magnet, a microwave power of 5.20 GW at X-band (frequency (8.25±0.01)GHz) is obtained in single pulse mode. The radiation power is 5.06 GW when the repetition rate is 30 Hz, and the pulse length is 13.8 ns.

Bitron - a new high power microwave device

Bitron, as a new type of high power microwave device, is proposed in the paper. The parameters (such as microwave power and its efficiency) based on the theoretical analysis has been realized on 2.5D PEC (particle in cell) simulation code. This device composes of two parts: one modulation cavity and one output cavity. The couple exists between these two cavities, so the oscillation occurs under certain conditions. X band bitron is designed in the paper, and its theoretical efficiency is 29.4%. And the process is also realized by 2.5 PIC simulation code, and the efficiency is 28%, the microwave frequency 9.42 GHz, the power 2.25 GW.

Investigation of Photocathode

ABSTRACT The experimental studies of photocathode driven by laser are reported in the paper. The experimental systems including the D-C voltage vacuum chamber and measurement apparatus are given. Also we will present the experimental results and discussions of LaB 6 , pure metals (Cu,Sm) and semiconductor Cs 2 Te photocathodes. The quantum efficiencies of photocathodes are 6 × 10 −4 , 3.8 × 10 −4 , 11.6 × 10 −4 and 2 − 6 × 10 −2 respectively, the corresponding photocurrent densities are 70 A/cm 2 , 50 A/cm 2 , 102 A/cm 2 and 257 A/cm 2 are obtained. Using the pepper pot method, the normalized beam emittances for these materials are about 10 π.mm.mrad and the corresponding normalized brightness are about 10 10 A/m 2 rad 2