Design of proton deflectometry with in situ X-ray fiducial for magnetized HED systems

Abstract

We report a design and implementation of proton radiography with an in situ reference X-ray image of a mesh to precisely measure non-uniform magnetic fields in expanding plasmas at the OMEGA and OMEGA EP laser facilities. The technique has been developed with proton and x-ray sources generated from both directly-driven capsule implosions and short pulse laser-solid interactions. The accuracy of the measurement depends on the contrast of both the proton and x-ray images. We present numerical and analytic studies to optimize the image contrast using a variety of mesh materials and grid spacing. Our results show a clear enhancement of the image contrast by a factor of 4-6 using a high Z mesh with large grid spacing. This would lead to a further factor of two improvement in accuracy of the magnetic field measurement.