tisSCN EGIEAEATION +O tee eH approx:ating those en. Guat) He tere rhe ee ee Se mE go In this way most cases .. 7 Be PSO due to high humidity beta. - 20 2: ct and were remedied before fieid ue: 2 Gv Chavcuments. Care was taken to check and cy lhbhrete each instrument periodically whether it was used or not, and additional checks were rade before each shot. In the case of dosimeters and pocket chambers, a constant record of leakage was maintained, The eight men assigned to this work were more than was required. Although many of this group had little previous experience with the particular types of instruments used, their training in electronics permitted them to learn easily. At times some of these men were used for communications work but only to a limited degree. Experience gained during Operation Sandstone was responsible for a much more efficient operation than would otherwise have been possible. 2.9.1 Pocket Dosimeters and Chargers One hundred pocket dosimeters of 200-mr range were supplied by Beckman Instruments and 100 of a similar range by the Kelley-Koett Mig. Co. A total of two hundred 200-mr dosimeters proved inadequate for this operation, and, although 35 additional instruments were borrowed, a total of 300 could easily have been used. These 200-mr dosimeters were considerably more reliable and caused less trouble than those used in Operation Sandstone. This was doubtless due, in great measure, to the methods used in sealing the chamber from moisture. It was difficult to tell whether leakage was a result of moisture or of defective insulation. Of the 200 dosimeters, 24 were eventually set aside as having excessive leakage. Calibration, in general, was good when a radium source was used. It was observed, however, that calibration and leakage both changed with time as the dosimeters were used. Also at times considerable differences were noted in readings of film badges and dosimeters used by monitors in the field. This may have been due to any of several factors such as defective films, energy dependence, monitor’s technique, mete etc. A calibration test using radium as a source showed comparative readings to be within normal limits of accuracy. In the case of all dosimeters, the pocket clip was subject to rust in the aia testStea eTinttte. Provision should be made for rvst-proofing this clip. No other part showed a tendency to rust or corrode. Little burning of scales due to concentration of sunrays was observed, although this was a factor at Operation Sandstone. No recognizable difference was noted in Keleket or Beckman dosimeters. Two hundred 10-r Keleket dosimeters were supplied which proved adequate. Of this number, 17 were eventually set aside as having excessive leakage. In general, the foregoing remarks on 200-mr dosimeters apply to the 10-r instruments with perhaps one exception: A greater difference in film badge and dosimeter readings was observed occasionally after exposure in the field, although comparative checks with a radium source indicated results within normal limits of accuracy. In the case of the 200-mr and 10-r dosimeters, comparative checks were made with film badges, in the field, with fission product radiation as a source, and results were within normal limits of accuracy. In these tests a selected Victoreen model 300 Proteximeter was used as a standard ion chamber. One hundred forty-four 50-r Keleket dosimeters were supplied. This number was considerably more than was required. Of these dosimeters, 23 were eventually set aside as having excessive leakage. Calibration and leak- age tests were identical with other instruments, and, in general, the same remarks apply. Comparatively few of these instruments were used in the field by monitors, and none were actually required. One hundred twenty-five Keleket and eight Beckman chargers were supplied. Probably not more than 25 were used. No trouble of any kind was experienced with either Beckman or Keleket instruments, although construction is somewhat Gifferent. A feature incorporated in the Beckman charger of automatically disconnecting the batteries when the dosimeter is removed will no doubt result in increased battery life. No choice, however, was indicated by users. Two hundred 100-r and twenty-five 200-r Victoreen pocket chambers were supplied. Records were kept on leakage and calibration, but none of these instruments were used, hence, no information is available on their behavior in the field. Four minometer charger-readers were supplied by Victoreen and proved quite satis-