[en] TEM and ordered Cu₃Au were employed to measure the probability of dislocation loop formation as functions of irradiating ion mass (Ar⁺, Cu⁺ and Kr⁺), energy (50 and 100 keV), and irradiation temperature (30 and 300⁰K). Disordered zones were produced at every defect cascade site and imaged in dark-field superlattice reflections. Dislocation loops were imaged in fundamental reflections in the same sample areas to produce an accurate measurement of the probability of the collapse of each cascade to a dislocation loop, within a large set (approx.200) of defect cascades for each irradiation condition. The size distributions of dislocation loops and disordered zones were also measured. Defect cascades collapse to dislocation loops with significant probability (approx.0.5) even at 30⁰K. Other observations include an increasing collapse probability with increasing cascade energy density (increasing ion mass) and with increasing sample irradiation temperature. However, no additional collapse was observed upon annealing from 30 to 300⁰K, and no increase in collapse probability was observed upon increasing the bombarding ion energy from 50 to 100 keV. Disordered zone sizes also increased with increasing ion mass and with increasing sample irradiation temperature (30 to 300⁰K)