Development of an ultrafast X-ray computed tomography scanner system: Application for measurement of instantaneous void distribution of gas-liquid two-phase flow

An ultrafast X-ray computed tomography (CT) scanner has been developed. This scanner overcomes problems that occur in a transient or unsettled state, which make the conventional CT scanner inappropriate. To reduce the scanning time, this X-ray CT system uses electronic switching of electron beams for X-ray generation instead of the mechanical motion adopted by conventional CT scanners. The mechanical motion is a major obstacle to improving scanning speed. A prototype system with a scanning time of 3.6 ms was initially developed and confirmed to measure the dynamic events of two-phase flow. However, an increased scanning speed is generally required for practical use in the thermal hydraulics research field. Therefore, an advanced type which can operate under the scanning time of 0.5 ms and can measure two-phase flow with a velocity up to 4 to 5 m/s was developed.