Whilst the field of High Energy Density physics spans a history of more than a century, it lacks a reliable dynamic temperature diagnostic. This work presents computational and experimental work on developing such technique based on the principle of detailed balance. In molecular dynamics simulations, monocrystalline copper is shocked along [001] to pressures ranging between ambient and 70 GPa, and its synthetic elastic and inelastic diffraction signal is computed via the spatial and temporal Fourier transforms of the atomic coordinates. In the plastic regime beyond the Hugoniot elastic limit, the crystals slip faults and stacking faults arise, which cause certain Bragg spots to link up in reciprocal space. The compression facilitates the detection of the inelastic phonon modes through pressure hardening by increasing their spacing in energy space, yet the quasi-elastic signal linked to the stacking faults can dominate the spectra outside of the first Brillouin zone. Whilst these temperature measurements highly benefit from increased resolution, it is proposed that the shock compression setups can also determine a Doppler-induced energy shift on the order of meV, which could be used as a direct particle velocity diagnostic. As part of a collaboration in the European XFEL experiment p2191, the ambient and resistively elevated temperatures of monocrystalline diamond are determined. In order to expand this technique into the field of dynamic compression, more results of experiment p2191 and work of p2656 presented here recorded spectra for polycrystalline copper, cobalt, and nickel samples. Whilst no temperature could be determined, the photon levels for a seeded XFEL sufficed to generate high-resolution spectra of inelastic scattering that exhibit varying asymmetry, indicating the presence of microstructure-related quasi-elastic scattering. Whilst predictions about the inelastic signal strength through a photometrics code could be verified, diffraction data remained inconclusive due to poor grain statistics in the polycrystalline targets.