Table 1. Plutonium Source Exposures of LR-115/II Etch £6¢ Sample Degrader Net Time Etch Temp. Blank 59.7 + 0.6} 0.22 2461 3180 77 M (min.) (°C) (Tracks/mm*) Sample Tracks Incident* Alphas Efficiency (%) Method** x -0005" Mylar 92 XIV -0005" Mylar 90 ~ 60.0 0.04 2162 3180 68 M XVIII .0005" Mylar 90 ~ 60.0 0.12 2349 3180 74 M (XVIIT) .0005" Mylar 90 ~v 60.0 KKK 2689 . 3180 85 TA XXIX .0005" Mylar 90 59.8 + 0.4) 0.43 2880 3180 91 IA XXX .0005" Mylar 90 60.2 + 0.9 0.69 2317 3500 66 TA XXXITI .0005" Mylar} 90 61.7 + 0.4] 0.93 1944 3180 61 TA 90 60.1 + 0.4[ 0.13 5143 RKKK 90 57.0 + 0.41 0.03 1264 3500 XXXIV XXXV XXXVIII} none 1.8 cm air .0005" Mylar} 90 60.1 + 0.4 0.20 133. [1.4 x 10° <o.1 TA 36 NOTES: *Incident alphas calculated from source strength, exposure time, and geometric factors. **kM = visual count by microscope; IA = automatic scanning image analysis. *k*kNot determined; visually measured background used to calculate net tracks. *kKANOt calculated because of exposure area uncertainty. See Figure 3. TA IA