This is the diagram taken right from your text, there are the two electrodes coming in and this is atomic hydrogen in the gas tube.

这是从教科书上复制下来的图表，这里有两个电极进来,这是气体管中的氢原子。

麻省理工公开课 - 固态化学导论课程节选

This is a glass tube. There are some feedthroughs here to allow electrodes to be potted.

这是个玻璃管，这里有些引线,可以使电极被射击。

麻省理工公开课 - 固态化学导论课程节选