Influence of cathode geometry on discharge characteristics of magnetron-type discharge cells

Discharge characteristics of magnetron cells with different geometry of the central cathode rod are presented. The cathode rod had one of the following cross-section shapes: circular, rectangular, square, star-like or 4-triangular. The discharge characteristics of the cells were measured systematically at different anode voltages between 1 and 8 kV and pressures between 5×10−9 and 1×10−6 mbar. The magnetic field density was constant at 0.13 T. The experimental results showed that the current at first slowly increased with increasing voltage, reached a maximum at a certain voltage and then decreased with further increase of the anode voltage. The highest currents were observed in the cell with the triangular cathode rod, while the lowest currents were observed in the cell having the cathode rod with the circular cross-section, where the currents were lower by about 50%.