V. G. Rabotkin

Processes in the prebreakdown stage of a low‐pressure discharge and the mechanism of discharge initiation in pseudospark switches

A time‐dependent model for the rapid current rise during initiation of the discharge in a pseudospark switch is presented. The following assumptions are made: (1) the gas is ionized only by electrons that originate at the cathode; (2) the cathode emissivity is infinite; (3) the average ionization cross section is constant; (4) the ion charge density is independent of gap position. The results are in qualitative agreement with a previous experimental study of a nitrogen‐filled switch operating between 6 and 20 kV for a range of gas pressures. The model provides a straightforward approach for estimating pseudospark breakdown times.

Implosion of Multilayer Liners

Experiments on the implosion of multilayer cascade light liners were carried out on the IMRI‐3 (0.3 MA, T/4 = 700 ns) and IMRI‐4 (0.24 MA, 900 ns) installations. It has been demonstrated that when using three sequantial cascades, owing to the suppression of the Rayleigh‐Taylor instability, the ratio r10/rf ∼ 70 (where r10 is the initial radius of the outer cascade) can be achieved. The input energy density and the X‐ray output therein h are observed to increase (respectively, up to 1 kJ and 200 J for Kr). Measurements performed with the use of a grating spectrograph for different gases have shown that the temperature in the plasma column formed in liner implosion increases with atomic number.

Nonmonotonic potential distribution and current quenching mechanism in plasma-filled diode

The phenomenon of current quenching in a plasma filled diode forms the basis for operation of the so called plasma erosion opening switch. In typical operation conditions of the switch, a vacuum gap is preliminarily filled with a plasma from an external source after which a voltage is applied to the gap and an external electric circuit provides for a current rise with a characteristic time of the order of 1 /spl mu/s. When the current reaches some critical value the resistance of the gap sharply increases so that the current quenching and the corresponding voltage kick occurs, i.e. the gap opens for a short time. A widely used approach for interpretation of the current quenching mechanism is based on the supposition that the gap conductivity is totally determined by the plasma generated by external source. In our opinion, this viewpoint is not exactly correct, especially for the microsecond time scale, and the current passage mechanism is mainly determined by the cathode spot plasma. A foundation of this approach is presented in this paper.

Investigation of prebreakdown currents flowing in pseudospark gaps

Currents flowing at the prebreakdown stage in a pseudospark-gap switch with an ignition unit based a steady-state glow discharge are studied. The mechanism of operation of the blocking electrodes is explained. An electrode construction that makes it possible to increase substantially the static breakdown voltage of the device is presented.