STUDY OF A TRANSAUGMENTED 2-STAGE SMALL CIRCULAR-BORE RAILGUN FOR INJECTION OF HYPERVELOCITY HYDROGEN PELLETS AS A FUSION-REACTOR REFUELINGMECHANISM

Injection of hypervelocity hydrogen pellets has become widely accepted as the most effective means of refueling magnetically confined fusion reactors, Pellet velocities on the order of 10 km/s are desired and h ydrogen pellet erosion during acceleration must be minimized. It is im portant to maintain uniform bore surfaces during repetitive shots, imp lying that, if a railgun is to be used to accelerate the pellets, dama ge to the sidewalls and rails of the railgun due to local heating must be limited, In order to reduce the amount of power dissipated within the bore and increase the propulsive force generated by the plasma-are armature while minimizing losses due to pellet, rail, and sidewall ab lation, we have employed a magnetic field transaugmentation mechanism consisting of a two-turn pulsed electromagnet, The two-stage gun consi sts of a light-gas gun which accelerates a 4- to 5-mg pellet to a spee d around 1.2 km/s and injects it into the plasma-are armature railgun. Currently, we have achieved a final output velocity for a hydrogen pe llet of 2.11 km/s with a time-averaged acceleration of 4850 km/s(2) us ing a 58-cm railgun pulsed with a peak rail current of 9.2 kA and 28.0 kA of transaugmentation current. This paper will present a descriptio n of our hydrogen-pellet-injector railgun system, a discussion of the data on hydrogen pellet acceleration, and projections for future syste ms.