Experimental studies of dust charging in laser-plasma experiments at the Orion facility*

In these experiments, carbon foam (CHO) targets with micron-scale copper dust granule fills were fielded on the ORION laser. Proton radiography (PRAD) and X-ray radiography images were taken at multiple times following laser drive on the target’s surface using ORION’s nanosecond pulse beams. The laser illumination drives shocks in the foam that sweep across the embedded dust particles. PRAD images were taken using radiochromic film (RCF) stacks at the pre-, during and post-shock stage with the aim of examining dust grain charging and density evolution as a function of the dust grain size. 

 

The presence of electric fields cause deflections in the PRAD protons’ paths, and the deflections due to electric fields can be separated by those induced by plasma magnetic fields owing to their different scaling with the proton energy. Results from X-ray radiography were also used to determine the size of the dust granules and compared against FLASH simulations to obtain a measurement of plasma conditions.