Saturation characteristics of ionization chambers for high-intensity continuous and pulsed x-ray beams

The relation between current and applied voltage of parallel-plate and free-air ionization chambers was investigated for high-intensity X rays from synchrotron radiation. To make pulsed X rays, synchrotron radiation was intercepted at 533 Hz with a rotating disk having slits. For continuous X rays, m decreased with applied voltage at parallel-plate ionization chamber. For pulsed X rays, VI was linear to 1/V at parallel- plate and free-air ionization chambers. At high-intensity, the applied voltage increases the ion velocity, and the transit time became almost comparable to the pulse width. At this condition, the X rays became "continuous" and 1/I approached linearity to 1/V² rather than 1/V.