COUNTS / 455 MINUTES ror? OCTOBER — — | r / | C - —— 2-9-60 455 mint ----- 1-17-60 455 min 5"x 4" Nol crystal a r 1959 | | Difference i \ \_ \ ! i \ l \ | \ \- Ye / _ \ ~~ 7 7 / Nb?? \ \ 4 \ | \ | 17 Ny/ : : fzr3 \ } —_ \ ~ .—Be’ Standard FE | 4 O | 0.25 | i 0.5 Y-ENERGY 0.75 (Mev) Fig. 1 -- Gamma-ray spectrum of ashed air filters