|
The fundamental studies on the high-intensity single flash x-ray generator having
a low-vacuum diode for biomedical radiography are described. This generator
consisted of the following essential components: a high-voltage power supply, a
high-voltage pulser with a coaxial oil condenser of l5OnF, a low impedance
transmission line made from four coaxial cables with lengths of 5. 6m and a total
capacity of 292OpF, a mechanical booster pump, and a flash x-ray tube. The x-ray
tube was of the diode-type which was connected to the booster pump with a constant
pressure of 1. 7Pa and consisted of the following major devices: a long anode tip
made of tungsten with a diameter (D) of less than 3. 0mm and a length (L) of 50mm, a
long cathode tip made of tungsten with a D of 1. 0mm and a L of 40mm, a
polyoxymethylene insulator, lead diaphragms, and an x-ray window made of
polyethylene terephthalate. The coaxial oil condenser in the pulser was charged
from 50 to 90kV, and the electric charges in the condenser were discharged to the
flash x-ray tube through a transmission line by using a gas gap switch with a highcurrent
capacity. The peak voltage increased according to increases in the
condenser charged voltage and its value was more than the charged voltage. The peak
current primarily increased when the charged voltage was increased, and its value
was less than 4OkA. The pulse width of the flash x-rays ranged from 60 to 8Ons, and
the time integrated x-ray intensity with a charged voltage of 90kV and an anode
cathode (A-C) space of 3. 0mm was about 4pC/kg at 1. Om per pulse the source. The
effective focal spot size was primarily determined by the diameter of the anode
tip, and its value was about 3. 0mm when an anode diameter of 3. 0mm was employed.
|
