  We consider a technique to determine the initial beam conditions of the DARHT
II Accelerator by measuring the beam size under three different magnetic
transport settings. This may be time gated to resolve the parameters as a
function of time within the 2000 nsec pulse. This technique leads to three
equations in three unknowns with solution giving the accelerator exit beam
radius, tilt and emittance. We find that systematic errors cancel and so are
not a problem in unfolding the initial beam conditions. Random uncorrelated
shot to shot errors can be managed by one of three strategies: 1) make the
transport system optically de-magnifying; 2) average over many individual
shots; or 3) make the random uncorrelated shot to shot errors sufficiently
small. The high power of the DARHT II beam requires that the beam transport
system leading to a radius measuring apparatus be optically magnifying. This
means that the shot to shot random errors must either be made small (less than
about 1%) or that we average each of the three beam radius determinations over
many individual shots.
