TOTAL-ABSORPTION GAMMA-RAY SPECTROSCOPY 189 x a ee ee ee 1 Oo ZN RAIN & gol NS 70h 4 UV 6.0 4 z am a 30- O Z 4.0F 4 =_ 3.07 4 “ 2 2.0 4 0 _ 15 Z > } 3 z Zu25- rea 1.0 KA 4 B D f + i Poe a 18 19 20 21 22 23 24 2526 27 2829301 2 34 5 6 7 8 9 10111213 1415 16 1718 SEPTEMBER OCTOBER DATE Fig. 7—Bismuth-214 effective surface amounts as a function of time, L963, ent in September and October 1963. The similar period for 1964 is shown in Fig. 8. The modulation of some of the measured radionuclides by an 8-in. snow cover in January 1964 is seen in Fig. 9. Initially, '°Sb and “Mn were not observed to be in the gamma-ray spectrum, but as the amount of *Zr—**Nb diminished, these nuclides were observed in the residual amounts left after the attempt to account for all the gamma Spectrum. If it is assumed that all gamma-ray inputs have been aceounted for and that proper calibrations for each source in the field geometry are available, then, by multiplication of each calibration Spectrum by the amounts of each determined to exist and addition of all these amounts channel by channel, the original field spectrum should be obtained. How well the reduction technique accounted for the initial field spectrum is determined by subtracting the created spectrum from the original field spectrum. The residual spectrum should be zero. A residual spectrum for current data is shown in Fig. 10. The nuclides 2087] M4py CMRI M07 9 0K MM, %zr—%Np, %Cs, 1%sb, and '41, and the 0.5 Mev radiation have been accounted for. However, neither “°La nor '!] existed. The reduction should provide '*°La and ‘*"I to be zero if the accounting is proper, Near-zero residual spectral amounts remain when an 11 by 11 inverted matrixis used for reduction. If only the amounts of all gamma emitters creating energy lines, including the 'Cs, are removed, the residue of Fig, 11 exists. Here the 0.48- and