Rare earth doping of CaF2produces material which gives strong thermoluminescence signals. In an attempt to separate the influence of impurity and intrinsic defects CaF2has been implanted with ions of Ce, Dy, Mn, Ca and F. Comparisons are made with chemically doped samples and the effect of thermal treatments have been made in all cases. The cerium and dysprosium ions influence both the shallow charge trapping levels, which determine the temperature of the glow peaks, and the recombination sites which control the photon spectra.