Monte Carlo-based simulation of x-ray phase-contrast imaging for diagnosing cold fuel layer in cryogenic implosions

Diagnosing the layered cryogenic DT implosions with traditional absorption based x-ray backlight radiography in inertial confinement fusion is a challenge because of the low opacity of the cold fuel. Refraction enhanced x-ray phase-contrast imaging was proposed for diagnosing optically opaque material. In this paper, A Monte Carlo tool based on Geant4 is employed to model the x-ray phase-contrast imaging for diagnosing cold fuel layer in cryogenic implosions. This model can successfully explain the x-ray phase-contrast imaging experimental results on a micro focus x-ray tube with triple-layer ablator capsules. Furthermore, the radiographs of ignition-scale capsule target is calculated. The fuel layer of DT ice can be observed with the phase contrast imaging and the image is faded using absorption imaging only. Our simulations show that the shape of cold fuel and implosion velocity can be inferred directly with the phase contrast imaging in inertial confinement fusion(ICF).