Numerical Model of the DARHT Accelerating Cell

The DARHT-2 facility at Los Alamos National Laboratory accelerates a 2μsec electron beam using a series of inductive accelerating cells. The cell inductance is provided by large Metglas cores, which are driven by a pulse-forming network. The original cell design was susceptible to electrical breakdown near the outer radius of the cores. We developed a numerical model for the cell, including the magnetic properties of Metglas 2605SC tape over the range of Ḃ (magnetization rate) relevant to DARHT. The model was implemented in the LSP electromagnetic code. LSP simulations showed that the field stress distribution across the outer radius of the cores was highly nonuniform. This was subsequently confirmed in experiments at LBNL. The calculated temporal evolution of the electric field stress inside the cores approximately matches experimental measurements, and shows the importance of rate-dependent hysteresis. The cells have been redesigned to greatly reduce the field stresses along the outer radius.