Monitoring X-ray Tube Output with Ionization Chamber

The intensity of X-ray beam can be stabilized by using an ionization chamber as a monitor which is placed between an X-ray tube and a specimen. Namely, the filament current of the X-ray tube is controlled so as to keep the output potential of the ionization chamber constant. The ionization chamber was designed in consideration of the response for wavelengths and the statistical fluctuation of the output voltage. Thus, high stability of a demountable X-ray tube as well as of a sealed-off one was obtained without rigorous regulation of tube voltage. If an X-ray tube is operated at 40 kVp and tnbe voltage is stabilized within ±1%, the fluctuation of intensity can be limited to ±0.1%. Then, the fluctuation of intensity in a broad diffraction line of a polycrystalline specimen which was measured for five hours could not be distinguished from the statistical fluctuation. But the fluctuation of intensity in a diffraction line of a single crystal was ±0.2% for the sealed-off tube and ±0.5% for the demountable one.