Is sodium hex what is used in medium voltage (up to 25 kV) breaker 'bottles"? If so, a static gap minght be a better approach in this. We used breakers at work up to 25 kV as breakers and switches, as it quenches arcing to protect the electrodes. The bottles can be purchased ready made, so no need for fabrication. They rarely see several operations per day, so I don't know how they'd perform at 120 bps.
________________________________
From: Phil Tuck <pip@xxxxxxxxxxx>
To: 'Tesla Coil Mailing List' <tesla@xxxxxxxxxx>
Sent: Wednesday, April 9, 2014 3:41 AM
Subject: Re: [TCML] fluid quenched rotary spark gap
Never tried, but I would imagine the drag from the fluid would be excessive
and the motor size needed would make things impracticable. When modifying to
synchronous, the motor looses quite a lot of power in the conversion. I can
see the motor burning out if you're not careful.
A better approach would be a gas filled box. Sulphur hexafluoride is an
excellent insulator and is heavier than air so if it leaks you know where it's gone.