Cathode assemblies, methods for adjusting focal points of x-rays, and methods for controlling focused electron beams

A method for adjusting a focal point of an X-ray using a cathode assembly, wherein

• the cathode assembly comprises:
• a cathode, including at least two emission portions each of which is configured to independently emit an electron beam, the at least two emission portions being arranged around a center of the cathode;
• and
• a focusing electrode, the focusing electrode being arranged around a periphery of the cathode, a first surface of the focusing electrode forming a first acute angle with an axial direction passing through the center of the cathode;
• the method comprises:
• obtaining an operating mode of an X-ray tube;
• applying a preset current to the cathode according to the operating mode, to selectively control one or more of the at least two emission portions of the cathode to emit the electron beams.

A method for controlling a focused electron beam using a cathode assembly, wherein

• the cathode assembly comprises:
• a cathode, including at least two emission portions each of which is configured to independently emit an electron beam, the at least two emission portions being arranged around a center of the cathode;
• and
• a focusing electrode, the focusing electrode being arranged around a periphery of the cathode, a first surface of the focusing electrode forming a first acute angle with an axial direction passing through the center of the cathode;
• the method comprises:
• determining at least one target emission portion of the cathode according to a desired position and a desired size of a target focal point;
• providing a first potential to the at least one target emission portion;
• and
• providing a second potential to the focusing electrode, so as to focus the electron beam emitted from the at least one target emission portion.