An automated process that can produce targets of any density gradient along an axial and a radial coordinate is explored. Such an approach is based on the observation that particles of different size, shape and density settle in fluid-filled columns differently. The invention presents models and procedures to automate the process so as to obtain any combination of density gradients.
 The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-48 between the United States Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory.