COMPARISON OF EXPOSURE STANDARDS IN 10-50 KV X-RAY REGION

Direct comparisons of the low-energy X-ray exposure standards of the Bureau International des Poids et Mesures (BIPM) and the National Research Council of Canada (NRC), and also of the BIPM and the National Bureau of Standards of the USA (NBS), were made, using X rays generated at 10, 30 and 50 kV. The half-value layers for these qualities of radiation were 0.036, 0.17 6, and 2.257 mm of aluminum respectively. The results indicate that measurements with two free-air chambers can be made in the low-energy X-ray region with a discrepancy of less than 0.3%. The uncertainties and errors in the geometric and correction factors used for the comparison measurements, as well as other systematic and statistical errors, were examined in detail and are reported. The results of preliminary work on air attenuation corrections, diaphragm comparisons and saturation corrections are included.