The switching element used as a linear modulator should have the characteristics of stable ignition time, fast deionization speed, and bottom pressure of the tube. Currently, there are only two devices with this feature: hydrogen thyratron and thyristor. Compared with thyristors, hydrogen thyratrons have characteristics such as large power capacity, high forward blocking voltage, and high allowable value of current and voltage rise rates, so hydrogen thyratron
are generally used as switching elements of linear pulse modulators.
A brief description of the structure of a hydrogen thyratron
A common hydrogen thyratron
is a gas-filled triode: anode, grid, and cathode. The anode is a flat disc, separated by a fine mesh made of fine tungsten wire or nickel wire; 2~3 cm below the anode is a control grid, which is similar to a lining, and the round hole on the top is formed by a grid. Covered with a large fine grid; the cathode is a side-heated oxide, which is a hollow cylinder with an oxide coating on the inner working surface and a double-helix filament on the outside. In addition, the thyratron is also equipped with a hydrogen generator, which is a small tube filled with titanium hydride powder and wrapped with a hot wire to release hydrogen when heated. Usually, the hot wire for heating the hydrogen generator is connected with the filament for heating the thermal oxide cathode, so the pressure in the tube is related to the voltage of the filament, and a warm-up time of 3 to 5 minutes is required; of course, some hydrogen generators are powered independently.