Sounding experiments of high pressure gas discharge

A high pressure discharge experiment (200 MPa, 5.10(21) molecules/cm(3), 3000 K) has been set up to study electrically induced shock waves. The apparatus consists of the combustion chamber (4.2 cm(3)) to produce high pressure gas by burning solid propellant grains to fill the electrical pump chamber (2.5 cm(3)) containing an insulated coaxial electrode. Electrical pump energy up to 7.8 kJ at 10 kV, which is roughly three times of the gas energy in the pump chamber, was delivered by a capacitor bank. From the current-voltage relationship the discharge develops at rapidly decreasing voltage. Pressure at the combustion chamber indicating significant underpressure as well as overpressure peaks is followed by an increase of static pressure level. These data are not yet completely understood. However, Lorentz forces are believed to generate pinching with subsequent pinch heating, resulting in fast pressure variations to be propagated as rarefaction and shock waves, respectively. Utilizing pure axisymmetric electrode initiation rather than often used exploding wire technology in the pump chamber, repeatable experiments were achieved.