| A transaugmented electromagnetic railgun has been designed, optimized, and tested as a cryogenic hydrogen pellet accelerator. The hydrogen pellet injector is being developed as a possible refueling scheme for the magnetically confined plasmas. The experimental system is comprised of a liquid-helium-cooled pellet generator, a pneumatic gun, a coupling stage, and a railgun accelerator. The railgun is driven by a plasma-arc armature and the coupling stage is necessary to vent excess propellant gas before the pellet reaches the railgun. Reducing the pressure behind the pellet improves the breakdown conditions for the source gas behind the pellet.;A magnetic field transaugmentation mechanism is utilized in the railgun to enhance the generation of Lorentz force while reducing bore material and pellet ablation. A two-dimensional magnetostatic finite element method model was used to optimize the augmentation mechanism configuration. The design was optimized to maximize coupling of magnetic flux between the main rail pair and the augmentation mechanism while remaining within mechanical design constraints. The result is a three-turn configuration with a mutual inductance gradient of 0.54 ;Experiments were conducted using 3-turn augmented railgun 1.2 m in length with a variety of rail current pulse shapes. Ramped pulse shapes between 350 and 600 ;Additional experiments were performed using 120-... |
