DISCLAIMER This report was prepared as an account of work spomored by an agency of the United States Government Neither the United States Government nor any agency thereof. nor any of their employees. make any warranty, exprra or implied, or assumes any legal liability or respom-biIity for the accuracy, completeness or usefulness of any information, apparatus, product, or process disdased, or represents that its use would not infringe privately owned rights. Reference herein to any spedfic

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... rdal product, proces. or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, mmmendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not n e c s a rily state or reflect those of the United States Government or any agency thereof. Portions of this document may be illegible in electmnic image produa fmnces are produced from the best available original doamlmt ABSTRACT This study resulted in the design, construction and testing of a gas flow proportional counter for in-situ determination of soil contamination. The uniqueness of this detector is the screened material used for the cathode. A Pu-239 source of 0.006 pCi was mounted to the outside of the cathode to simulate radioactive soil. The detector probe was placed into a laboratory mock-up and tested to determine operating voltage, efficiency and energy resolution. Two gas flow proportional counters were built and tested. The detectors are cylindrical, each with a radius of 1.905 cm, having an anode wire with a radius of 0.0038 cm. The length of the smaller detector's anode was 2.54 cm, and the length of the larger detector's anode was 7.64 cm. Therefore, the active volumes were 28.96 cm3 and 87.10 cm3, respectively, for the small and large detector. An operating voltage of 1975 volts was determined to be sufficient for both detectors. The average efficiency was 2.59 k 0.12% and 76.71 k 10.81% for the small volume and large volume detectors, respectively. The average energy resolution for the low-energy peak of the small detector was 4.24 & 1.28% and for the large-energy peak was 1.37 f 0.66%. The large detectors' energy resolution was 17.75 k 3.74%. The smaller detector, with better energy resolution, exhibited a bi-modal spectrum, whereas the larger detector's spectrum centered around a single broad peak.