Noun
English Wikipedia has an article on:thyratronWikipedia
thyratron (plural thyratrons)
(electronics) Any of several types of thermoelectric valve once used as a high-speed switch
A cold-cathode version of the thyratron, which uses a pool of mercury for its cathode, is called an ignitron ; some can switch thousands of amperes. Source: Internet
The thyratron is a special-purpose tube filled with low-pressure gas or mercury vapor. Source: Internet