How do cations striking the cathode produce detectable current in a Penning gauge?

[terryphi]

Hello,

So, I'm reading up on penning gauges, and wikipedia (reliable source I know :P) says that the collector current depends on the number of cations which strike it.

So, the question I have is, how can you detect when a cation strikes a cathode? is there some sort of change in current? Why? I have some ideas, but I would really like to know your guys thoughts on this.

Edit: In the patent they talk about an 'ion discharge'. Does anyone have any insight as to what that is?
:S

 

[DrClaude]

So, the question I have is, how can you detect when a cation strikes a cathode? is there some sort of change in current? Why?

What happens to the electrons in the cathode when a cation strikes?