Magnetized Target Impact Fusion

Impact fusion has long been a dream of some fusion researchers. Early estimates for net gain required 200 km/s, but later estimates for strongly magnetized fusion targets were ~10 km/s. NearStar Fusion is developing a Magnetized Target Impact Fusion concept in which a 10 km/s 20-50 gm solid projectile impacts a stationary target containing DD fuel and an internal z-pinch similar to Winterberg[1]. Although harder to ignite, DD avoids DT supply chain issues and simplifies reactor construction. The z-pinch is energized at impact along with magnetic flux trapping and compression providing the required strong B fields. Bohm diffusion scaling suggests time scales for implosion and burn are short compared to ablation and mixing with impurities. Analytical modeling of batch burn cases including ohmic preheating, radiation, thermal conduction, and impurity mixing with the target first wall predict gains of 5-10 with impact speed as low as 5 km/s, and gains with burn of a secondary liner reaching >50 for DD fuel, possibly with a small DT trigger. A repetitively firing Self-Augmented Railgun[2] is described which will launch solid projectiles with impact kinetic energies of 1-2.5 MJ. We provide an overview of our efforts to identify a practical magnetized target impact fusion configuration, and also evaluate production of medical isotopes such as Ac-225 as a potential earlier intermediate step to net fusion gain for energy production. [1] Winterberg, IEEE Trans Mag, 1982, [2] Burton et al, J Appl Phys, 1991.