10 KHZ MICROSECOND PULSED X-RAY GENERATOR UTILIZING A HOT-CATHODE TRIODE WITH VARIABLE DURATIONS FOR BIOMEDICAL RADIOGRAPHY

A 10 kHz pulsed X-ray generator utilising a hot-cathode triode in conjunction with a new type of grid control device for controlling X-ray duration is described. The energy-storage condenser was charged up to 70 kV by a power supply, and the electric charges in the condenser were discharged to the X-ray tube repetitively by the grid control device. The maximum values of the grid voltage (negative value), the tube voltage, and the tube current were -1.5 kV, 70 kV, and 0.4 A, respectively. The duration of the flash X-ray pulse was primarily determined by the time constant of the grid control device and the cut-off voltage of thermoelectrons. The X-ray duration was controlled within a region of less than 1 ms; the X-ray intensity with a pulse width of 0.27 ms, a charged voltage of 70 kV, and a peak tube current of 0.4 A was 0.92 mu C kg(-1) at 0.5 m per pulse. The maximum repetition rate was about 10 kHz, and the size of the focal spot was about 3.5 X 3.5 mm.