Acceleration of solid hydrogen pellet using augmented railgun for magnetic fusion reactor refueling

A 1.2 m long electromagnetic railgun with separate augmentation was designed, fabricated, and tested for the purpose of injecting hypervelocity hydrogen pellets into magnetic fusion devices for refueling. A compact configuration of two pairs of coaxial rails insulated by thin Kapton films was employed. Two pulse-forming networks were used to separately control the duration, amplitude, and overlap of the current pulses. Copper sulphate resistors were employed as impedance-matching resistors and bank short resistors. The magnetic field inside the gun bore boosted by the high current on the gun augmentation rails, which in turn increased the J/spl times/B force without increasing the armature current, resulting in less ablation of the gun bore and pellet. Higher acceleration was achieved due to reduced inertial and viscous drag. Using a 1.2 m augmented railgun, hydrogen pellet velocities in excess of 2.5 km/s were achieved. Hydrogen pellet accelerations as high as 4.4/spl times/10/sup 6/ m/s/sup 2/ were achieved at a railgun current of 13.5 kA while the acceleration obtained on a conventional railgun was 2.2/spl times/10/sup 6/ m/s/sup 2/ at 14.1 kA. Computer simulations have been performed using the finite element code MSC/EMES to analyze the current density, magnetic field, Lorentz force, and inductance gradient of the conventional and augmented railguns.>