ACKNOW LEDGMENTS Fhe author wishes to acknowledge the assjgtance of Dr. R. L. Mather and Dr. C.S. Cook whose suggestiong and critical re- wiew of the report were greatly appreciated, The assistance of Dr. D.L. Love and Mr. Jj, L. Mackin of f#nalytical and Standards Branch of Chemijca} Technology Division in preparing the calibrated standards is gratefully acknowledged. The excellent liaison both in regard tq samples and information between Radiological Capabilities Branch ef Ghemical Technolog: Pivisigqn and this Section was provided by Mr. W. Williamson, Ji The Gaussian curve generator was constructed by Mr. P.S. Applebaum. Members of the Electronics Section were cooperative at all times.