X-ray diffraction diagnostic paired with gas gun driven compression of polyethylene

Abstract

Understanding the kinetics of phase transitions, including decomposition from reactants to products under extreme condition events is challenging. Capturing these processes require: 1) diagnostics that probe on the timescales and at energies capable of interacting with the dynamically evolving products, penetrating the opaqueness of the changing system; and 2) detectors sensitive enough to observe these events. Synchrotrons and free electron lasers provide ke-V-energy x-ray beams capable of penetrating the optical-opaqueness of the temporally evolving products. At the Dynamic Compression Sector at the Advanced Photon Source, the x-ray beam is coupled to single and two-stage gas guns capable of producing planar shocks at a range of projectile velocities while capturing in situ x-ray diffraction/scattering of the evolving material under dynamic compression. In this work, we demonstrate the utility of this approach in measuring the evolution of crystalline domains in shocked high-density polyethylene to P = 7.45 GPa, and have observed the compression and orientation of the polymer chains in real time.