Gridded crossed-field tube

Claim 1

A crossed-field switch device comprising: a tubular anode electrode and a tubular cathode electrode spaced from said anode electrode the active areas thereof defining and facing a main discharge gap having therebetween a continuous closed path and means for making electrical connections to said anode and said cathode electrodes and means for providing a gas at sub-atmospheric pressure in said main discharge gap and a magnetic field above the critical value in said main discharge gap so that a glow mode plasma discharge can take place between said anode and said cathode electrodes for conduction of said switch device, the improvement comprising: a tubular control electrode positioned adjacent to one of said anode and cathode electrodes to form a continuous closed path ignition discharge gap adjacent to, substantially over the whole active area of and in communication with said main discharge gap, the electrode between said main gap and said ignition discharge gap being an intermediate electrode, said intermediate electrode having openings therethrough so that there is a line of sight between said main gap and said ignition gap so that plasma can pass from said ignition gap to said main gap; and means for electrically pulsing said control electrode with respect to its adjacent electrode on the other side of said ignition discharge gap for bringing conditions in said ignition discharge gap into conductive conditions so that glow mode plasma discharge begins in said ignition discharge gap and enters into substantially the entire active area of said main discharge gap through said intermediate electrode to cause conductive condition of said main discharge gap so that said crossed-field switch device can be turned on with voltage applied thereto without magnetic field pulsing and with uniform wear of said anode and cathode electrodes over their entire active areas.