X-ray generation device and cathode thereof

An x-ray generation device, comprising:

• a cathode having a base and a side wall about 5 mm to 10 mm in height forming a trench shaped container, a plurality of metal bars mounted in said trench and on said base and each of said metal bars having a diameter between about 0.1 mm to 3 mm, wherein each of said metal bars have a carbon layer grown thereupon including an interlayer and an emission layer, said emission layer having a multiwall morphology multiwall;
• a hollow focusing cap as an electromagnetic lens disposed in front of said cathode so as to focus an electron beam emitted from said emission layer and emergent out through a hollow of said focusing cap;
• an anode target;
• a glass chamber for housing said cathode, said focusing device, and said anode target in sequence;
• wherein said x-ray generation device has a feature that under conditions of a constant emission current density 1 mA/cm2, and a distance between said anode target and said metal bars varied from 7 mm to 60 mm, an operating voltage is kept at a range between about 12 keV-13 keV.