0.20 0.30 0.50 0.70 1.00 1.50 2.00 3.00 4.00 61.5 54.0 43.3 37.5 33.4 29.5 27.1 25.3 24.4 A.2.8 Single-Channel Analyzer (Nuclear Radiation Branch) (Reference 57) i, Crystal dimensions and type: 4-inch diameter x 4 inches thick, Nal(T1) Photomultiplier tube type: 6364 DuMont Pulse-height analyzer type: Model 510-SC Atomic Instruments Pb shield thickness: 244 inches Collimator dimensions: ‘4-inch diameter x 6 incheg long Sample container type and size: glass vial, Yrtooy diameter x 2% inchea long Distance from bottom of sample to collimator opey. Minimum count rate requiring coincidence loss correction: 1.0 x 10° counts/min Counting procedure: ordinarily 3- to 1-minute intervals for each sample; trays decontaminated and ing: 2 inches counted with 14-inch aluminum cover in place Calibration standards: Na™, and Hg? A.2.7 Dip Counter. Crystal dimensions and type: 1'4-inch diameter X 1 inch thick, NalI(T1) Photomultiplier tube type: 6292 DuMont Sealer type: Same as doghouse counter Shield thickness and counting chamber dimensions: Same as doghouse counter Sample volume: 2,000 ml (constant geometry) Counting efficiency for several nuclides: (Private communication from J. O’Connor, ‘NRDL) Nuclide Celt Heg”*3 Aul®s * Cpgi8? Nb*5 Se Co Na A.2.9 ergy and standard bers (A, . Gamma Time-Intensity Recorder. The en. directional response characteristics of the TIR detector, consisting of four ion chamAm, Bm, and Cm) with a protective dome, were determined at NRDL. (Measurements and cal- culations were carried out by G. Hitchcock, T. Shirasawa, and R. Caputi.) A special jig permitted both horizontal and vertica) Totation about the center of the chamber under study, Directional response was measured and recorded con- tinuously for 360 degrees in planes at 30-degree increments through the longitudinal axis of the Cm chamber. Relative response data was obtained by effectively exposing the chamber to a constant ioniza~ tion rate at six different energies— four X-ray energies: 35 kev, 70 kev, 120 kev and 180 kev; and two counts/dis x 107? 1.20 1.72 1.28 0.916 0.870 1.76 1.56 1.29 source energies: Cs!*’ (0.663 Mev) and Co™ (1.2 Mey), The results for three mutually perpendicular planar responses have been illustrated graphically to show: (1) shadowing interference by other chambers in the horizontal plane (Figure A.2), (2) maximum shadowing interference by other chambersin the vertical plane (Figure A.3), and (3) minimum shadowing interference by other chambersin the vertical plane (Figure A.4). Minimum count rate requiring coincidence loss correction: 2 x 10° counts/min Counting procedure: 2,000-ml samples at constant geometry; counting intervals selected to maintain a statistical error <1.0 percent 164