Issues for high performance magnetic flux compression generators

High explosive driven magnetic flux compression generators (FCGs) provide pulsed power for a variety of applications. This paper discusses issues encountered by designers requiring fast high current pulses to accelerate z-pinch loads for high energy density experiments. There are two primary concerns. The first is generating large fast-rising currents with flux compression devices. In a simple sense, current is doubled every time the total inductance in the circuit is reduced by a factor of two. The final doubling time is the time it takes to remove the final inductance from the FCG, starting at the time when the FCG inductance is equal to the inductance residual in the load and transmission lines at peak current. The second issue is balancing the energy required against the total energy generated. Large currents require wide conductors for good generator performance. Increasing conductor width reduces inductance (L) per length in circuits, so higher current requirements dictate lower L and dL/dt for any generator design. The result is increased doubling time for a specific load. At the same time, the transfer efficiency from magnetic field to implosion kinetic energy plays a very important role. High efficiency transfer allows generating the minimum energy required. However, high efficiency dictates that the current be highly reduced by the increasing load inductance, which in turn reduces the load driving force. To maintain a strong driving pressure throughout the implosion requires that the current remain high, and hence a great deal of energy will remain in magnetic field at the end of the implosion. Tradeoffs are discussed between generator design and efficiency for high energy density experimental requirements.