bbot

Sure, he's just accelerating particles. You can buy an old x-ray machine on ebay and irradiate whatever you like. You can buy a fusion reactor off the shelf: http://phoenixnuclearlabs.com/product/high-yield-neutron-generator/

So, there's several problems with metal grid cathodes in IEC fusors:

1. They heat up pretty fast, and cooling them is hard.
2. They get in the way of fuel ions, reducing how many ion collisions can happen.

An arc wouldn't care if it got hit by energetic particles,[1] but it still would get in the way of fuel ions. Even if the arc was, to choose a nice round number, 100,000K, a 15KeV ion has a temperature of 174,000,000K. Hitting an arc would cool it down dramatically.

Plus, how are you going to form a spherical grid of arc discharges in a vacuum?

Polywell fusors try to solve the grid problem with magnetic shielding. Who knows how well it works, the EMC group hasn't been very talkative recently.

1: ...maybe? You'd imagine a high enough particle flux would "blow it out". You'd also run into weird convection issues in steady-state operation.

0.06 micropascal, unless I missed a zero? What vacuum pumps are you using?

Increasing the gas pressure would also introduce bad mean-free-path issues.