Observation of cavitation bubble cloud using a stroboscopic x-ray generator

The radiographic characteristics of the condenser-discharge stroboscopic x-ray generator and its application to high-speed radiography are described. This generator employs a condenser- discharge medical x-ray generator in conjunction with a new grid-control unit and consists of the following major components: a high-voltage control unit, a condenser unit having a Cockcroft circuit, a grid-control unit, a high- voltage grid-control unit, and a rotating-anode x-ray tube unit. The main condenser of about 500 nF in the unit is charged up to 120 kV by the circuit, and the electric charges in the condenser are discharged to the triode by the grid control unit in conjunction with a high-voltage grid-control unit. The high-voltage grid-control unit is employed in order to insulate the negative high-voltage grid and cathode electrodes from the high-speed grid control unit with almost the ground potential. In this generator the anode and cathode electrodes are applied to high-voltages with maximum values of +60 kV and -60 kV, respectively. Although the tube voltage decreased during the discharging for generating x- rays, the maximum value was equivalent to the initial charging voltage of the main condenser. The maximum values of the tube current and the repetition rate were about 0.5 A and 32 kHz, respectively. The pulse width of the x-rays ranged from 0.01 to 1.0 ms, and the maximum shot number had a value of 32. At a constant filament (cathode) temperature, the x-ray intensity increased according to increases in the charging voltage and to increases in the duration, and the maximum intensity with a duration of 1.0 ms and a charging voltage of 100 kV was 0.66 (mu) C/kg at 1.0 m from the x-ray source. The dimensions of the focal spot had values of about 1 X 1 mm, and both the inner and outer triggering for producing pulse x-rays can be employed. The high-speed radiography was primarily performed by the multiple-shot radiography using a new computed radiography (CR) system in conjunction with the computer- display system with an operation system of Windows NT Workstation 4.0.