412 SALTER | | “ 957 ,/ 905, RATIO 40 + Oo | | NO o 10 F— / ~_N, = —_ 4 | | 8 | w 8 | 8 | 905,, DIS/ MIN PER 10° SCF & 5 2 4Min/%Sr RATIO _ / \ 10 60 | 70 | 80 90 ALTITUDE, 1000 FT | 100 110 Fig. 1—Activity concentrations of 9Sr and activity ratios for *4Mn/ 9Sr and ™Zr/9Sr. 1961 debris, therefore, became increasingly difficult as material from the 1961 and 1962 tests mixed. The only other shot for which published information indicates unique tracers exist is Starfish, detonated July 9, 1962. In this 1.4-Mt detonation, an estimated 250 + 150 kc of !"°Cd (470-day half-life) and about 25% as much ‘!°"cqd (14-year half-life) were produced.’»® On the basis of an assumedfission to total yield of 50% and no fractionation, a 'cq/"Sr activity ratio of 3.5 + 2.0 may be calculated. If escape from the ionosphere occurred for neutron-activation products relative to the highly charged fission products, then the '°ca/*Sr activity ratio would be correspondingly smaller.