Study On Performance Of Impregnated Dispenser Cathode

As the core component of the gyrotron-- high-power microwave source, cathode provides high quality electron beam to interact with wave needed to amplify. The performance of cathode has a direct impact on the performance of gyrotron. Limited to the process conditions and the unmature cathode theory, factors affecting work stability and emission of the cathode are complex.This article is aimed to study the mechanism of the key technology and its impact on the performance of the cathode from the the aspects: porous tungsten matrix, active emitting material, cathode-assembly structure and electrophoretic deposition process. The main contents are as follows:1. We determined the optimum parameters for preparing porous tungsten matrix and the porous tungsten prepared by molding process meets the requirements. Besides, we have designed a taper CrWMn steel mold to release problem existed in process,including chipping, faults and other issues. The damage of tungsten matrix caused by stripping decreased to zero.2. We used chemical deposition methods to replace the traditional mechanical mixing process for preparing active emitter materials. Results of DC emission performance tests showed that the cathode current density of deviated point at 1000 degrees was 3.26 A / cm2, superior to the conventional B-type cathode’s 2 A / cm2.3. We determined the contact condition of the cathode-assembly model: emitter is ideal contacted with supportor, thermal conductivity between heaters and filler is 0.001 W /(mm2˙K) which is equal to thermal conductivity between supporter and filler. On this basis, we simulated the effect of heaters structure and filling height on the thermal field. At last we designed a new cathode-assembly structure. Simulation results show that the new cathode-assembly structure decreased the operating temperature of heater for more than 200 degrees and had more uniform temperature distribution, which is important to improve the working life of the heaters and cathode’s stability.4. Based on electrostatic field boundary conditions, we established electrophoretic deposition model and derived quadratic equation of deposition amount to voltage and deposition time. According to the equation, we obtained the same thickness of aluminum oxide insulating layer under different electrophoresis conditions. After the heat treatment, we found that aluminum oxide insulating layer deposited under 40 voltages for 6 seconds had the highest insulating performance. Aging results showed that the heaters can continuously work at 1100 degrees for more than 3000 hours.5. Respectly, we used the diode test systems and gyrotron to test the cathode emission. The results show that: the cathode current density of deviated point at 1000 degrees is greater than 5.05 A/cm2. When loaded power of 43.5W, pulse current emission density was 13.1 A/cm2 at 40 kV. Cathode performance met the requirements of gyrotron.