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Cold Cathode X-ray Tube with MgO Composite Gate Structure

In a triode field emission structure, the anode current is reduced due to the trapping of the field emission electrons by the metal gate mesh. We propose a composite structure with the MgO film evaporated on the surface of metal gate. The effect of the composite gate on the field emission of the CNTs cold cathode was studied. The cold cathode X-ray tube based on the composite gate was designed. Compared with the metal gate structure, the X-ray tube using the composite gate is stable, the anode current is greatly improved, and the electron transmittance is increased by more than 30%, which can reach 80%. It can be considered that the secondary electrons emitted from the MgO film, not only compensate the intercepted current, but also become part of the emission current, thereby improving the anode current.