  The photon Doppler velocimetry (PDV) spectrum is investigated in an attempt
to reveal the particle parameters of ejecta from shock-loaded samples in a
vacuum. A GPU-accelerated Monte-Carlo algorithm, which considers the
multiple-scattering effects of light, is applied to reconstruct the light field
of the ejecta and simulate the corresponding PDV spectrum. The influence of the
velocity profile, total area mass, and particle size of the ejecta on the
simulated spectra is discussed qualitatively. To facilitate a quantitative
discussion, a novel theoretical optical model is proposed in which the
single-scattering assumption is applied. With this model, the relationships
between the particle parameters of ejecta and the peak information of the PDV
spectrum are derived, enabling direct extraction of the particle parameters
from the PDV spectrum. The values of the ejecta parameters estimated from the
experimental spectrum are in good agreement with those measured by a
piezoelectric probe.
