Charged Particle Stopping Power Experiments on Orion

The Orion laser facility provides a platform for performing direct drive capsule implosions. The predicted level of capsule performance for this type of experiment is uncertain, largely due to the reduced number of laser beams (10), compared to facilities such as OMEGA (60), which limits the drive symmetry. To this end, following a one-dimensional (1D) design study of capsule phase space, experiments have been performed to evaluate the performance of deuterium (DD)filled targets. A thin shell "exploding pusher" (EP) design is desirable both for robustness and for future charged-particle stopping power experiments to validate current stopping power theories, important in high-energy-density physics (HEDP). Stopping power experiments require a well-known source of particles (a proton source, the EP target), a well-characterized plasma (secondary target), and an accurate measurement of the energy loss (downshift in energy of the particle traversing the plasma). DD implosions generate 3MeV protons, which will then interact with the secondary target heated isochorically by a short pulse laser to similar to 200-300 eV at solid density (eta(e) similar to 2 x 10(23) g/cc). The optimum EP capsule selected from the study, taking into account facility and target fabrication constraints, satisfies design criteria on the 1D clean fusion yield, capsule dynamics, and implosion time. The nominal target was a silica glass shell of radius 250 +/- 10 mu m and thickness 2.3 +/- 0.5 mu m, filled with 10 atm of DD gas. The preliminary secondary target was a plastic cuboid of similar to 70 x 70 x 50 mu m dimensions. The work presented here focuses on the design of an optimum EP capsule and includes experimental results for comparison.