TABLE OF CONTENTS (Cont'd) Page TABLES TABLE I. CALIBRATION OF 4" x 4" NaI(T1l) DETECTOR......... 35 TABLE II. DOSE RATE CALIBRATION OF 4" x 4" DETECTOR NATURAL EMITTERS........- ccc eeec cree eee eeeteeeee 36 TABLE III. DOSE RATE CALIBRATION OF 4" x 4" DETECTOR FALLOUT. 0... 0. cee ee wee ee eee ee eee eres 37 TABLE IV. TERRESTRIAL GAMMA MEASUREMENTS TABLE V. COSMIC RAY IONIZATION AND ULTRA LOW BACKGROUND FIELD MEASUREMENTS (ur/hr)..... cc eee eee eee 44 TABLE VI. VARIATION IN NATURAL GAMMA DOSE RATES (ur/hr) AT PELHAM, N. Y. AND MAMARONECK, N. Y., 1963 LOG. cc ee et eee te eee eee eee tee eens 45 (ur/hr)........5. 38 ILLUS TRATIONS Figure l. Typical field spectrum. Shaded areas indicate our estimates of the peak area used to determine the total dose rate due to indicated isotope and daughters. E,, E5, and E3 are the 3 bands used for determining natural gamma dose rates...46 Figure 2. Examples of spectra taken at low gamma activity SLICES... ce ee ee ee ee eee ee eee 47 Figure 3. Total spectrum “energy" and E], Es, and E3 energy band responses to cosmic ray secondaries.48 Figure 4, Pressurized argon-filled ionization chamber with electrometer readout UNit.... eee ewe ee eee ee ee 49 -~ vi -