Electrical properties of plasmas formed in explosive magnetic flux compression generator environments

Explosively driven shock tubes are used to study shock induced gas conductivity in explosive magnetic flux compression generators (FCG's). The shock tubes use 50 grams of composition C-4 explosive to propel aluminum flyer plates towards dense stainless steel plugs to simulate gas compression as the armature approaches the stator in an FCG. The 2.5 cm ID acrylic shock tubes are designed using the Gurney method to drive the flyer plates at velocities similar to FCG armatures (3-4 km/s). Experiments have been performed with argon, helium, synthetic air, and sulfur hexafluoride. Current and voltage measurements have been used to determine plasma bulk resistance as a function of time. Minimum resistances of 2.7 Ohms in argon and 6.5 Ohms in SF6 were measured. These measurements were used to calculate minimum plasma resistivities of 0.031 Ohm&middotcm for argon and 0.073 Ohm&middotcm for SF6. Calculations are based on experimental geometry and the assumption of a finite plasma disk between current and voltage probes.