The following jate are abstracted from experinental results, wherein a thin pse soure@e prepared by soaking « fiver paper in a solution ef phosphates, allowing it to dry, and then ~weasuring surface dose rates with e surface ionisation chanber. * Thiekness of source 9.6 ng/ex* Activity of source 77.49 pe/ent Surfnoce dose rate Dosage rate at tertr of « cert seter+ 0.127 repsee 457 repe/hr e770 5x Sabet ituting abowe data: a . $14 Roe 6 215) (92907) gy, = 0.0 C repe,hr Let © S77 p20, ox Thm Re yx. 7 | #539 repa/ho at “ mg or OA