Preliminary results from a scaled Final Focus Experiment for heavy ion inertial fusion

Vacuum ballistic focusing may be a straightforward method to obtain the heavy ion beam spot size necessary to drive an inertial confinement fusion target. Proper scaling of particle energy, mass, beam current, beam emittance, and magnetic field replicates the dynamics of a full driver beam in a small laboratory experiment. By expanding the beam and then focusing to a very small spot, the effects of aberrations and space charge on this method of final focus can be studied. To date, 200 μA of 120 keV K⁺ has been focused to test the matching and focusing elements. A recently designed high brightness contact ionization source is being tested for upcoming focusing measurements with an 87 μA Cs beam that will duplicate the dynamics of a proposed driver design at one-tenth scale. Transverse phase space and beam current density at various stages of the focus will be presented. Follow-on measurements studying electron neutralization of space charge and its effect on the focus will be explored