Experimental Study of the Accelerator of a Pulsed High-Current Radially Converging Electron Beam

A new cylindrical electron accelerator with a revised design (1-m long cathode, new plasma cathode concept) was built and a first experimental study of its operation was performed. The cathode plasma is generated by uniformly distributed vacuum-arc discharge gaps and its expansion is limited by a stabilizing grid. From the timescale of cathode plasma formation, a plasma temperature of about 40 eV is estimated. Electrons are emitted from the cylindrical cathode and radially accelerated toward the tube anode located along the accelerator axis. Due to the small anode radius of only 0.5 cm and the rather large azimuthal velocities of the electrons at emission, about 20% of the beam electrons miss the anode and circulate in the accelerator volume. This process significantly increases the current to the control grid of the triode-type accelerator at the expense of a reduced current delivered to the anode. The effect of circulating electrons is much less pronounced for an anode with radius 1 cm.