The CV100 basket covered glass valve is designated as a triggered spark gap or trigatron. The varnished basket was provided as a means of containing the glass if the enveloped splintered in use.
Use was as a pulse modulator for a magnetron. The data-sheet gives the performance at 16 kV; a 2μs pulse with a repetition of 400 pulses per second.
A television program about the first UK atomic bomb seemed to show a CV100 used to obtain simultaneous firing of the explosive lenses used to generate implosion. The HV pulse would vaporise the wire in the trigger.
Internally there are two opposing domed surfaces plus the trigger electrode.