Dual Ion Species Plasma Expansion from Isotopically Layered Cryogenic Targets

A dual ion species plasma expansion scheme from a novel target structure is introduced, in which a nanometer--thick layer of pure deuterium exists as a buffer species at the target--vacuum interface of a hydrogen plasma. Modeling shows that by controlling the deuterium layer thickness, a composite H+ /D+ ion beam can be produced by target normal sheath acceleration (TNSA), with an adjustable ratio of ion densities, as high energy proton acceleration is suppressed by the acceleration of a spectrally peaked deuteron beam. Particle in cell modeling shows that a (4.3 +/- 0.7) MeV per nucleon deuteron beam is accelerated, in a directional cone of half angle 9 degrees. Experimentally, this was investigated using state of the art cryogenic targetry and a spectrally peaked deuteron beam of (3.4 +/- 0.7) MeV per nucleon was measured in a cone of half angle 7 degrees-9 degrees, while maintaining a significant TNSA proton component.