| abstract |
An X-ray generator includes a cathode having an emitter made of carbon nanotubes which emits electrons by field emission and thus becomes a cold cathode electron emission source. In the invention using the carbon nanotubes, any one of the following three forms is adopted to control the tube current apart from the electron-focusing control. The first form is that a takeoff electrode is disposed near the cathode and the Wehnelt potential and the takeoff electrode potential are controlled independently. The second form is that an electron emission source is disposed behind the cathode and the electron emission source emits electrons which collide against the back of the cathode so that the cathode temperature is controlled in a range of the room temperature to about 100 degrees Celsius to regulate an amount of electron emission from the cathode. The third form is that the cathode has a heater so that the cathode temperature is controlled in a range of the room temperature to about 100 degrees Celsius to regulate an amount of electron emission from the cathode. |