An Engineering Approach to Increasing Proton Radiography Sensitivity to Material Shock Front Detection

The proton radiography facility at the Los Alamos Neutron Science Center (pRad) is used to probe shocked materials from ~1 g cm-2 to 50 g cm-2 with temporal resolution down to 100 ns. Its sensitivity is adjusted by installing a collimator specific to the areal density range under interrogation. This presents a problem because collimators change often, and such changes are labor intensive and time consuming. This work has seen the development of a push-button actuated collimator capable of remotely installing available collimator settings within seconds. The suite of collimators imposes an angular acceptance of 5, 7.5, 10 and 20 mrad, and inverse (dark field) collimators, which block the beam not scattered, with an angular acceptance of 2, 3, 4 and 5 mrad. The addition of the dark field collimation settings, combined with an upstream pre-collimator, allows for the investigation and implementation of the Dark Field Proton Radiographic technique, which has been demonstrated to increase sensitivity to areal density changes by a factor of two, and visualize thinner materials. This system will be implemented at the LANSCE proton radiography facility in 2022 to validate the forward model of the dark field concept and visualize shock fronts and the turbulent mixing regions in noble gases.