Measurements of defect production rates during proton irradiations at 125 K have been used to probe the damage structure produced by protons or heavy ion irradiations. Electrical resistivity was used to monitor the probe damage rates. As the energy density of the displacement cascade increases, the probability of a probe interstitial annihilating with a vacancy within the cascade is reduced relative to its trapping at interstitial clusters. There is also a slight decrease in the average vacancy annihilation radius with increasing energy density in the cascades. During annealing, the relationship between annihilation and trapping probabilities remains constant throughout stage II, but in stage III, the annihilation probability decreases strongly. This annealing behavior was observed for all ion irradiations and is believed to be due to a reduction in the average vacancy annihilation radius associated with the formation of vacancy loops.