Railgun type double stage acceleration device

Existent railgun type double stage acceleration devices for use in a thermonuclear device involved a problem so far that releasing amount of secondary electrons is reduced and destruction of electric insulation between rail electrodes is made unstable to increase a possibility of operation failure. In the present invention, there is disposed a means for accelerating plasmas to generate electric discharge between the rail electrodes by electric fields generated by a needle electrode disposed in the insulation material which supports the rail electrodes. Since ions of plasmas generated by laser beams are accelerated by high electric fields generated to the needle electrode, and collide against the rail electrodes at high energy, a large amount of secondary electrons are generated and the destruction of the electric insulation between a pair of rail electrodes is stabilized, to improve possibility of operation failure. (N.H.)