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关于场发射枪束流稳定性的问题,我们曾做过专门的实验。影响发射不稳的因素很多,其中真空条件是主要的,至少应优于10~(-9)托。此外,防止第一阳极出气也是十分重要而又困难的问题。因为这一部分即是已经很好除气,但在真空中仍不断吸附残余气体,作场发射后,直接受电子的轰击而被释放。这些气体又使发射器表面气体吸附更严重,离子腐蚀作用加剧,导致束流很不稳。这种现象在每当场发射之初尤为明显,真空度立即下降。为了减少这一影响,我们把场发射枪第一阳极设计成能直接通电加热,比用附加灯丝电子轰击法,除气快,效果好,几秒钟内温度即可升到500℃以上,对束流稳定度大有改善,如图1所示(两种情况的发射器均未做“闪电”处理)。
On the issue of field gun stability, we have done a special experiment. Many factors affect the launch instability, in which the vacuum conditions are the main, at least better than 10 ~ (-9) care. In addition, preventing the first anode from venting is also a very important and difficult issue. Because this part is already well degassing, but still in the vacuum adsorption of residual gas, as the field emission, the electron bombardment directly be released. These gases in turn make the emitter surface gas adsorption more serious, ion corrosion increased, resulting in beam instability. This phenomenon was particularly evident at the beginning of each scene, and the degree of vacuum immediately dropped. In order to reduce this effect, we design the first anode of the field emission gun to be directly energized and heated. Compared with the additional filament electron bombardment method, the degassing is quick and the effect is good. The temperature can rise above 500 ℃ in a few seconds. The stability of the beam greatly improved, as shown in Figure 1 (in both cases, the transmitter did not do “lightning”).