| 摘要 |
PURPOSE:To compensate the fluctuation in the radiation quantity from a threshold X-ray tube by measuring first the quantity of the threshold X-rays radiated from the threshold X-ray tube in the radiation source thereof and comparing and calculating the measured value and the measured value of the X-rays transmitted through a material to be measured. CONSTITUTION:The flux from a threshold X-ray tube 1 is throttled with a mask 2 and is made into a flux 3 for measurement, which is projected to a material 5 to be measured. A primary ionization chamber 4 installed right under the mask 2 measures the quantity of the threshold X-rays in the flux 3 transmitted through the mask 3. On the other hand, a secondary ionization chamber 6 measures the quantity of the threshold X-rays transmitted through the material 5. Both measured values are compared and calculated by a comparator 7. Then even if the radiation quantity from the threshold X-ray tube fluctuates, the stable measured value is obtd. Since both measurements are accomplished in the same atmosphere, the atm. pressure, temp., humidity, etc. acts equally on these measured values and are not the factor for an error within the range of the comparison and calculation thereof.
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