I used to operate a Cryogenic nitrogen Plasma gantry ..big scale..50 ton remote control cranes..underwater cut.
Our shielding was basically solid alloy metals..solenids sequencing by compuetr...the tolerances were severe..any divergence in tolerances and the Plasma stream would errupt..
Ceramic/Alloy insulators can take you just so far as application goes.
Boeing Zenon Ion drive thrusters work similar to my Plasma machine..their shielding is mechanical.
The new power applications require pure Magnetic fields..with the harmonics balanced.
We had some massive detonations....I can image the risk when trying to play with Terra Watts.