How making the ions leave the cavity in a ion sources

[coquelicot]

TL;DR

Asking by what technical mean do the ions get out of the cavity in ion sources, whenever the ions are ejected in an environment at atmospheric pressure

Ion sources are devices that allow creating ion beams (e.g. argon ions) and to project them outside the device, for example to be further processed by a particle accelerator, or to irradiate materials or biological tissues etc.

The ions are usually created by a plasma inside a cavity filled with a noble gas maintained at very low pressure inside the cavity. Then the ions are projected outside the cavity, not necessarily inside vacuum, but also in the air at usual atmospheric pressure (e.g. for metal plating).

So, the cavity cannot have a hole to let the ions get out, otherwise the vacuum in the cavity would be destroyed. My question is by what technical mean do they make ions get out of the cavity?

 

[mfb]

I know metal plating options that work without vacuum and I know ion plating in vacuum but I haven't seen a combination of that. A plasma window would be an option. With a sufficiently large ion energy you can use a thin solid window, too.

 

[coquelicot]

I know metal plating options that work without vacuum and I know ion plating in vacuum but I haven't seen a combination of that. A plasma window would be an option. With a sufficiently large ion energy you can use a thin solid window, too.

Thanks for the link to plasma window technology I was unaware of.
Returning to more conventional technologies, could you please indicate me in what material is a solid window made of, and what should be its thickness (order of magnitude). thx.

 

[mfb]

That will depend too much on the specific application.