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Nov18-11, 12:55 PM
P: 628
Quote Quote by Evil Bunny View Post
Can you create an arc in a vaccum?
If you mean 'a vacuum' (as in low, medium, hard, scientific, etc..) then the answer is that not only can you get an arc, but it is easier to get an arc, down to around 10 Torr, below which it gets more difficult.

Interestingly, it is more difficult to get an arc from electrodes closer together, than further apart. This is because electron cascading doesn't work well over very short distances.

The other thing you need for an arc is an ionisation source. Normally, once a gap is at sufficient potential it will spontaneously undergo cascade breakdown because it is exposed to cosmic and background radiation, which will ionise some molecules in the gap, triggering the cascade.

This piece of information is relevant because although it is pretty difficult to create a totally radiation-free volume, the inverse can be used to more easily initiate an arc by exposing the volume to intense radiation. But in any case, you need to exceed the Paschen breakdown and have some ionisation source.