Trigatron

A trigatron is a triggered spark gap which is typically used in radar modulators to feed the large pulse necessary to a magnetron. Trigatrons operate either in air or are sealed.

It consists of three electrodes, two of similar size, one of which has a third electrode held in a hole drilled through its middle. The undrilled electrode is negative with respect to the other two. The other two are normally at the same potential. When a trigger pulse is applied to the trigger electrode it causes the main electrodes to conduct.

Open air trigatrons could not be used at the low pressures encountered at high altitudes. After experiments with construction techniques and gas mixes a filling of a pressurised argon/oxygen mixture was selected with approximately 93% argon and 7% oxygen.

Type	CV85	CV100	CV125
Pulse energy (kW)	170	250	500
Pulse duration (µs)	1	2	1
Network voltage (kV)	7.2	16	12
Pulses/sec	1200	400	800
Gap length (cm)	4	6	6
Argon pressure (PSI)	45	65	55
Trigger voltage on-load (kV)	3	5	3.5
Starting voltage (kV)	2.5	5	5.5
Operating range (kV)	5 to 13	8 to 24	8 to 22
Life (hours)	400	2000	800

The woven protective 'sock' protects from explosion due to the pressure of gas inside these devices, though the bursting pressure of the bulbs is quoted at 300 PSI.