Study of self-generated fields in strongly-shocked, low-density systems using broadband proton radiography

Abstract

We report results from experiments on the study of field generation at the shock front in low-density gas configured in quasi-planar geometry using broad-energy proton probing. Experiments were conducted using three long pulse laser beams with a total energy of 6.4 kJ in 2ns for shock generation and an 850 J, 10 ps short pulse laser to produce broadband protons for radiography. Observations of the deflection pattern of probe protons show the existence of self-generated electric fields at the shock front with electric potential on the order of 300 V. Analytical and particle tracking methods support this conclusion.

Kinetic physics in ICF: present understanding and future directions

“…Strong, persistent electric fields have been observed at spherically converging shock fronts [79]. Experiments have successfully imaged the electric field structure at shock fronts produced on the OMEGA-EP laser using proton radiography [22,23]. The low DT-vapor density (0.3 mg/cc) in the core of an ICF implosion is strongly shocked prior to the deceleration phase, producing plasma with Knudsen number in the range 0.2-0.8 where kinetic physics is likely to dominate.…”