  The dual-axis radiography for hydrodynamic testing (DARHT) facility at Los
Alamos National Laboratory uses two electron linear-induction accelerators
(LIA) to produce the source spots for perpendicular flash radiographs of a
dynamic experiment.Manipulating the beam current is a means for adjusting the
dose, and one way to do this is to change the size of the cathode. This article
describes simulations undertaken to develop scaling laws for use as design
tools in changing the Axis-1 beam current by changing the cathode size.
