The ignitron is a high power triggered switch that turns on faster than a thyratron but using considerably more power. The BK178, like most high power ignitrons, is mercury vapour operated and water cooled. The cooling is designed to ensure the correct operating pressure of the mercury vapour.
The BK178 has a peak anode voltage of 25 kV and an average forward current of 40 A. The peak current can reach 100 kA. The rate of change per pulse is 200 A per second. The BK178 is designed for capacitor discharge pulse service.
The cathode end of the steel case with water connection. The wires are for the igniter.
The anode connection bar.
The wide metal tube envelope is 140 mm in diameter, and 10cluding the base is 510 mm tall.
Reference: Jeremy Harmer.
Updated April 25, 2019.