pletely absord all the moisture within the Instrument case after it had been sealed, High Sach RE « The frequent use of several large sources by peraonnel from other projects in the vicinity of the radsafe buliding, where the HASL instruments were serviced on Parry, prr- vented calibration of the low end of the TH-3-8 and TH-3-¢ scales. An increase in background of as mich as ten tines over the normal of 6M to .015 mr/nr was noted at such times. Fallout from BPAY raised the background at Eniwetok so that low end scale calibration was impossible at any time; in order to continue the program, a1] low level SCINTAMETERS were soved to Kwajalein for servicinge On occasion, the fallout even on Kwajalein was sufficlont to prevent low end calibration, although these periods were of relatively short duration. Background radiation rarely interferred with the calibration of the wien level SCINTAMETERS, the minisum scale reading being 1 arfhe. the vibrator-transfermer (vitran) reed adjustment. cauging erratic behavior. To correct this, foam rubber pads wece provided tc cushion the instrument within the survey aircraft. osming Ditficultiege Ninor circuit difficulties be ame sevice ant shortly after arriva, at the forward area “ut these were easily corrected. Circuit component failures vere infrequent. Faulty components were replaced from a stock of spare parts aaliae tained in the forward ares. Battery replacement was necessary on the average after 20 houre of meter operation. Replacement necessitated opening the instrument case. fach tine this was done where an air conditioned room was unayatiabdle the ustramert remined out sf service for up te 2h houre until tha celsture hed drted, The vitran in the power supply was the souree of tue. Leoubles which were corrected sfter they were discovered. Tene vere: (1) failure of the vitran to start when the instrument wee tumed on, (2) noise causing erratic meter fluctuations. The first dirrti- culty was casily eliminated by a simple adjustment of the vitran reed. The latter problew required # more critical reat adjust~ ment or cleaning of the conta:*. It wae found that much of thia noise was being coupled inte we circuit through & common ground from the vitran and filament batteries, Running separates ground leade from Uieee two sete of batteries directly ts the connector - Joining the battery section to the cirmuit section eliminated the necessity of a fine adjustment of the vitran ceed and also stabil- ised severel. instruments for which « noise free operating point B. Field Operation. In field use, the SCIN"AMETERS were found to be most satisfactory by task force personnel who used the instruments. Those characteristics wiich wems commented about moet frequently are: dependable operation, stable calibration, simle controls, single scale, wide range, and sealed circuit. The last chareeteristic was particularly helpful for cloud tracking service since the instruments were inaensitive to altitude FP. Position in Aircraft. Our experience has sicow that the position of the instrument within the aircraft must be selected so that the radiation from radium dials on navigational instruments is negligible and the ahsorbing material underneath is sininal and moisture seal of ths eircuit cases Greatest utility could be. realized if batteries could be integrated in a case that could be Plugged into the circuit case such that a spare battery set coul! be easily interchanged in the field by a non-trained Operator. If repetitive surveys are planned, the same position within the aircraft should be used each tine. (3) The vitran should cz modified, possibly by shock mounting or changes. conatant. (A position over 2 gasoline tank is unders-rable). Fhe could not be found by adjusting the reed. Recommended Modificationgs (1) Float point and gain controle should be accessible fron cut~ side the sealed circuit cases. (2) Battery clngee should ve pusaible without deatroying the eliminated in favor of a more stable power supply if one could b. ° found with comparable high efficiency. 65- Fe napetT RI Te tine an inatrument was resealed to allow the tesicant to beonme effective. Cecagionally, calibration of sne instrument would require several days because of the waiting periods. Frequently the mmidity was so high the package of dealcant could not com At times either aircraft vibration or rough handling affectoa ce ee ME the instrument case so that a waiting period was required every pocpersaite, ot eine oe Calibration waa Likewise a tedious procedure because of high tunidity., Calibration controls were accessible only by oponing