The BT45 is a hot cathode mercury vapour thyratron for pulse modulator applications. The CV22 specification attached was based directly on the BT45.
Derived from BT45, the CV22 used a directly heated folded nickel ribbon cathode, with oxides filled into a welded nickel gauze; this design gave a huge increase in the emitting surface. 20KV, 50A pulses.
The CV22 was used from 1941 in radar Type 291, to drive NT99 micropup triodes. It was also used in 1942 in radar Type 271Q, to drive the CV56 magnetron; two were used in 1941 in the GL3 system to drive the CV120 magnetron.
The printing on the envelope says that this is a Thyratron made by BTH in England. The Type is BT45. Etched into the glass cylinder is SP7657.
The base: the filament wires have ceramic bead insulation and spade connectors. The grid connects to the frams and collar.
Thanks to Andy VK5AAQ for sending these images.
The wide glass tube envelope is mm in diameter, and excluding the base pins is mm tall.