Axial magnetic field effects on redesigned ignitrons utilizing glass walls and cylindrical dielectrical inserts

The authors discuss test results for three special types of ignitrons; a small glass-walled ignitron, a demountable ignitron, and a commercial NL-2909 ignitron. The conduction experiments used a capacitor bank with 2.56 mF total capacitance and 128 kJ maximum energy at 10 kV. The ignitrons were in a critically damped configuration at peak currents of up to 100 kA. To study effects of axial magnetic fields on the switching characteristics, including self-breakdown voltage and arc voltage, the test specimens were mounted inside high-power, water-cooled electromagnets. The demountable tube was tested before and after the insertion of a dielectric cylindrical shield between the tube wall and the inner conducting structure of the tube. It is shown that axial magnetic fields stabilize and confine the discharge plasma to the interelectrode region, reduce the arc voltage and its ripple, and significantly reduce the self-breakdown voltage.<>