thicknesses of aluminum absorbers Calibration of the pressurized were placed over an array of dosimeters ion chamber against a point at three sites on Bikini Island. source, feather analysis of A the beta attenua-— Opa the method used with the instrument in this study, leads to tion curves gave a maximum beta about a 3% overestimate in the energy between 1.5 and 2.2 MeV. measurement of "typical'' environmen- Given the known predominance of tal fields in this country. 70, r- 90 YY beta activities in the soil, If a similar correction were made to this energy range is consistent with 90 these data, The analysis also revealed that the determinations (ion chamber and LiF average beta contribution to the TLD) would be within 10%. total LiF exposure rates was 274% -- considered to be satisfactory a vather significant contribution. apreement between the two reference Therefore, techniques used in this work. the 2.27 MeV Y beta radiation. it was necessary to reduce the agreement of the twa independent exposure-rate This is the LiF results by this amount to Hence, obtain the free-air gamma-ray the Nal scintillation readings were exposure rates. normalized to the output of the The comparison between the ion on the basis of these results, pressurized ion chamber. chamber results and the LiF gamma— Fig. 3. <A linear regression of the two data sets gives agreement of about 13% between the two methods. One also finds that the correlation of points in Fig. 3 is not as good as that in Fig. 2. This difference is most likely due to the beta contribution to the LiF results, which may vary throughout the islands, causing spread in the data. oy 0 Departure from the 1:1 relationship in Fig. lon chamber response — uR/h ray exposure rates is presented in O response or to insufficient consideration of the ion chamber 30 Fig. 3. 40 50 4 60 | 7 80 Comparison of responses of the pressurized ion chamber with LiF TLD's. The contribution due to cosmic radiation has been weducd ~—, ane a ‘Senet data for energy dependence. 20 yy LiF response — uR/h 3 may be due to an over- correction of the TLD data for beta 10 to} subtracted.