Source of electrons in x-ray tube?

Question

What is the source of electrons in an x-ray tube and how is the number of electrons controlled?

Answer 1

To generate this stream of electrons inside the x-ray tube, a powerful x-ray generator first takes the regular alternating current (AC) electricity from the power line at about 120 to 480 volts and transforms it into power in the range of 35 to 150 kilo volts (kV or thousands of volts). When this very high voltage potential is applied to the x-ray tube, a tight beam of electrons is fired out of a small wire (called the cathode) and strikes a metal disk (called the anode). When this stream of electrons hits the special metal compound of the anode (often tungsten or alloys including tungsten), it causes x-ray energy to be released from the metal's atomic structure. These x-rays are often filtered and collimated (or focused) as they leave the x-ray tube. The rays pass through the body part of interest in a straight line and are then recorded onto film or captured by an image intensifier and TV system to make the final image.

Hope that helped.

Answer 2

The source would be the heating of a filament on the cathode end of the tube, and the mA would control how many are produced :)

Answer 3

the electrons are emitted by a filament called the cathode which is heated  accordingly to the intensity required