Computational Study of Magnetic Dam Effects in a High Impedance Diode

摘要

Computer simulations have been conducted to test the 'magnetic dam' concept as a means for boosting the overall ion efficiency of high impedance diodes. The 'dam' consists of a cell located immediately behind the anode foil containing a wire along its central axis which carries a current flowing in a direction opposite to that in the diode gap. The azimuthal magnetic field generated by the wire current, I sub w, reflects the electrons crossing the foil back into the A-K gap at higher radii where their space charge can enhance ion emission over relatively large areas. Significant increases in the ion current were observed for several values of I sub w but a simultaneous increase in electron current prevented gains in overall ion efficiency. Instead, only decreased impedances were observed. The cause of this phenomenon is explained and indicates solutions which could benefit a wide range of future diode designs. (Author)