CADMIUM-109 RESULTS FOR UP TO 20 KM M. I. KALKSTEIN, A. THOMASIAN, and J. V. NIKULA Air Force Cambridge Research Laboratories, Bedford, Massachusetts ABSTRACT About 0.25 Mc of '°°Cd was produced as a unique tracer in the U. S. Starfish test of July 9, 1962, detonated at 400 km above Johnston Island, Subsequent measurements of samples collected up to about 20 km revealed an increase in concentrations at high latitudes in the southern hemisphere in the spring of 1963. This increase was coincident in time with the usual warmings in the southern-hemisphere polar stratosphere. The increase in the northern hemisphere occurred late in the winter of 1963-1964 and did not reach the values measured in the southern hemisphere. Meteorological observations indicate that this winter was quite mild in terms of disturbances in the polar region, with the principal disturbances occurring late in the winter. Stratospheric concentrations measured thus far correspond to roughly one-half of what was expected on the basis of the }**Rh experiment, INTRODUCTION About 0.25 Mc of '®Cd was produced as a unique tracer during Operation Dominic I in the U. S. Starfish test of July 9, 1962, detonated at 400 km above Johnston Island, Cadmium-109 (470-day half-life) decays by electron capture to /°?™Ag (39 sec), which in turn decays by an 88-kev isomeric transition to the ground state. In addition to the 109Cq, about 0.13 Mc of the long-lived isomer '!°™Cd, a 0.58-Mev beta emitter, was calculated as having been produced.’ 405