where K, U, and T are the dose rates in wr/hr for 40x, the 238y series, and the 232Th series, respectively, and E\', E7‘, and E3' are the total "energies" in BeV with cosmic ray contribution subtracted. The first constant in each of these equations was independently checked by calculation and/or laboratory calibration in a manner identical to that discussed in HASL-150 for the 5" x 3" detector. The regression analysis to determine the equation for U resulted in a much better correlation in the case of the 4" x 4" detector (r2 = .98) than was obtained for the 5" x 3" detector due most likely to the improved resolution enabling more precise 1.76 MeV peak area estimates. The correlation coefficients for the K and T equations were both r2>0. 98. Total Spectrum "Energy" Method In HASL-150 the total spectrum "energy" from 0.15 Mev to 3.4 MeV for the 5" x 3" detector was shown to be proportion: to the total dose rate from gamma radiation in the field. It was shown that in general the thicker the detector the less the dependence on incident y-ray energy when using total spectrum "energy" as a measure of dose rate. The 4" x 4" detectors should thus enjoy a flatter energy response than the 5" x 3" detector. In addition, its improved angular response compared to the 5" x 3" detector allows a better estimate of the conversion of field spectrum total "energy" to dose rate to be made from laboratory calibration results. The detectors were calibrated in the laboratory with our NBS standardized 226Ra source and shown to be proportional to dose rate for dose rates exceeding 50 ur/hr with a conversion factor of 38.8 BeV/(ur/hr). The measured angular response when integrated over the calculated incoming angular distribution of primary flux from a uniformly distributed source predicts a field angular correction factor of 1.11. The use of the angular distribution of primary flux (which is very insensitive to gamma-ray energy in the range 0.5 3.0 MeV, see Reference 3, Figure 7) rather than the unknown angular distribution of total energy flux should be adequate Since the angular response of the crystals is quite flat over the solid angle from which most y-rays are probably entering the detectors.