关键词: 
X射线管 /
电子枪 /
LaB6 热阴极 /
发射性能 /
热发射电流

摘要: 设计并制作了一种用于X射线管的电子枪。以具有优异电子发射能力的六硼化镧阴极代替传统钨阴极，采用石墨热子加热的夹持式阴极结构；电子光学系统采用静电自聚焦方式，设计了具有梯形聚焦槽的单圆筒电极聚焦结构，避免了聚焦电极的引出；完成了阴极罩、阴极筒以及陶瓷芯柱等阴极组件的设计与封接。测试结果表明，当六硼化镧阴极为4.5 mm0.8 mm的平面发射体结构时，在阴极温度1 500 ℃，阴阳极间距3.5 mm，阳极电压2 500 V条件下，热发射电流达到65 mA，且发射稳定性良好。在120 kV 阳极电压下，电子枪在X射线样管中的性能测试结果表明，样管具有良好的电压电流开关特性，验证了该电子枪用于X射线管的优越性。

An electron gun for X-ray tube is designed and produced. The clamping type lanthanum hexaboride cathode with graphite heater is used in replace of the traditional tungsten cathode owing to its excellent electron emission ability. To avoid the leads of focusing electrode, we design a single focusing electrode with a trapezoidal focusing groove and a rectangular hole. Finally, other cathode structures such as cathode cover, cathode support and insulating ceramics are designed and the assembling of electron emitting system is completed. Thermionic emission test shows that when the lanthanum hexaboride emitting area is 4.5 mm0.8 mm, the temperature of cathode is 1500 ℃, and the distance between anode and cathode is 3.5 mm, the anode current is 65 mA at
anode voltage of 2 500 V, and the emission stability is excellent. The test of the X-ray tube based on lanthanum hexaboride electron gun shows that favorable switching performance is obtained at anode voltage of 120 kV.