FOOTE e ” ae fr es re ee ee ee ee me ee ee ee ee ee ee ee ee ee e COUNTS/ CHANNEL Cae 186 CHANNEL NUMBER Fig. 3—Method of locating photopeak positions. k’', maximum count channel; k”, photopeak center, even-channel location; and k, computed bhotopeak, center location. solution for their intersection is assumed to be the peak location. This manner of peak locating has proved to require little computer time and is consistent to about +0.2 channelat channel 185. The lower energyline selected has varied, depending upon the intensity of energy lines that might overlap others. The 0.751-Mev line from *Zr—*Nb was used initially because of the superposition of the “’Laline at 1.60 Mev overlapping the “°K line at 1.46 Mev. After calibration using two photopeaks, the total spectrum is corrected, channel by channel, to be even-channel-corrected for precise energy calibration. If noncorrected field data were utilized, errors would result for */‘Bi, as shown in Fig. 4. This figure shows the loca-