The voltage at which a sphere or torroid with a minimum diameter will breakout

MaxVoltage =  1.5 kV * Diameter(mm)

Minimum diameter	Voltage
10 mm	15.0 kV
20 mm	30.0kV
40 mm	60.0 kV
100 mm	150.0 kV
200 mm	300.0kV
400 mm	600.0 kV
1 m	1500 kV
10 m	15000 kV