Laboratory Tests of Low Density Astrophysical Equations of State

Clustering in low density nuclear matter has been investigated using the NIMROD multi-detector at Texas A{\&}M University. Thermal coalescence models were employed to extract densities, $\rho$, and temperatures, T, for evolving systems formed in collisions of 47A MeV $^{40}$Ar + $^{112}$Sn, $^{124}$Sn and $^{64}$Zn + $^{112}$Sn, $^{124}$Sn. The yields of d, t, $^{3}$He and $^{4}$He have been determined at $\rho$ = .002 to .032 nucleons/fm$^{3}$ and T= 5 to 10 MeV. Symmetry energy coefficients and equilibrium constants for alpha production have been derived from these data. The data provide an important constraint on astrophysoical equation of state models at low density.