REPETITIONAL TYPE OF FIELD EMISSION X-RAY SOURCE HAVING VARIABLE SPECTRA

Abstract
A repetitional (triple shot) type of field emission x-ray source having variable spectra is described. This source consisted of the following components : a high voltage generating unit having a voltage divider device, three high voltage pulsers with output voltages ranging from 50 to 200kV, a triple parallel type of high speed impulse switching system, a high power gas diode having three terminals using field emission, and two evacuated field emission x-ray tubes, each of a different type. The pulse condensers of the pulsers were charged to the same or different energies by using a high voltage generating unit and were connected to the single x-ray tube through a high power gas diode using high voltage coaxial cables and gas (SF₆) insulation connectors. The duration of each x-ray pulse was about 1us, and the minimum time interval between two pulses was about 100µs. The maximum intensity was about 10C/kg at 1m/pulse, and the effective focal spot size varied from 0.2 to 3.0mm in diameter. The triple exposure of pulsed x-rays having variable spectra and time intervals was obtained by controlling the condenser charging voltage, the tube impedance, the diode impedance, and others.