Pulse thermionic emission performance of multi-crystal LaB_6 cathode

A flat-plate diode cathode was produced using multi-crystal lanthanum hexaboride(LaB6) material.The anode was molybdenum,and the cathode was heated by thermal conduction and radiated with a graphite heater.The pulse emission properties and the emission stabilities were investigated at different cathode temperature and under different vacuum level.When the LaB6 cathode with an emission area of 0.012 1 cm2 was operated at 1 600 ℃,1 650 ℃,1 700 ℃,respectively,the corresponding maximum of pulse thermionic emission current densities were 34.0 A/cm2,44.0 A/cm2,53.8 A/cm2,under 2×10-4 Pa,the pulse width of 40 μs,and repetition frequency of 107 Hz.The pulse thermionic emission density of LaB6 cathode was also measured under 2×10-4 Pa,5×10-4 Pa,2×10-3 Pa,respectively,and it was found that the pressure had little effect on the pulse thermionic emission density.Furthermore,it was found that the emission current density was not affected by the pulse width.