Abstract: An electric-arc discharge device includes an annular gas-flow nozzle surrounding the discharge electrode, the nozzle being configured for discharging gas flows at trans-sonic to supersonic velocity, with circumferential uniformity of the gas flow around the axis of the electrode, and directed downstream to surround and radially inwardly confine and shape the arc. The trans-sonic speeds of gas discharge are the result of special annular gas-nozzle design and suitable pressure of gas supply thereto, whereby a region of criticality characterizes gas flow within the nozzle, i.e., prior to discharge at trans-sonic speeds, the discharge being around the electrode and with such thrusting momentum as to establish shaping confinement and directional stability of the region of electric-arc development.