HALF-MINUTE COUNTS FOR NEUTRON PROBES

NEUTRON SYSTEMS FOR MEASURING SOIL WATER BY NEUTRON SCATTERING HAVE BEEN IMPROVED AND COUNTS PER UNIT OF MOISTURE (SLOPES OF CALIBRATION CURVES) HAVE BEEN INCREASED SUFFICIENTLY TO REDUCE COUNTING INTERVALS TO 1/2 MINUTE FOR MOST PURPOSES. HIGH VOLTAGE APPLIED TO THE DETECTOR TUBE IS BETTER REGULATED, TIMERS ARE MORE ACCURATE, AND ELECTRONIC NOISE IS LOWER. AN IMPORTANT IMPROVEMENT WAS THE INTRODUCTION OF 80 TO 100 MC. AMERICIUM-BERYLLIUM SOURCES, WHICH EMIT NEUTRONS AT FOUR TIMES THE RATE OF THE OLD RADIUM-BERYLLIUM SOURCES. ONE MINUTE AND 1/2 MINUTE COUNTS WERE MADE IN TWO HOLES SIX FEET DEEP FOR FOUR SUCCESSIVE WEEKS. THE COUNTS WERE CONVERTED TO INCHES OF MOISTURE AND COMPARED BY A CHISQUARE TEST. RESULTS INDICATED THAT 1/2-MINUTE INTERVALS WOULD PROVIDE THE REQUIRED ACCURACY STANDARD DEVIATIONS WERE DETERMINED FOR GROUPS OF 1-MINUTE AND 1/2-MINUTE COUNTS IN THE SHIELD AND IN THE SOIL AT APPROXIMATELY 10, 20, 25, 30, 35, AND 40 PERCENT WATER BY VOLUME. RESULTS INDICATED THAT FOR PRACTICAL PURPOSES 1/2-MINUTE COUNTS WERE ADEQUATE FOR LATE-MODEL PROBE SYSTEMS WITH 100 MC. AMERICIUM-BERYLLIUM SOURCES.

  • Supplemental Notes:
    • Vol 110, No 5, PP 359-360, 2 TAB, 4 REF
  • Authors:
    • Rogerson, T L
  • Publication Date: 1970-11

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Filing Info

  • Accession Number: 00237931
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Dec 28 1970 12:00AM