Electron linear accelerator having an ideal beam loading characteristic

An electron linac with a traveling wave resonator in which the coupling is adjustable is presented. This linac has an ideal beam loading characteristic. When the beam current changes and so long as the coupler is adjusted to the optimal coupling its efficiency can be maintained. So its beam loading characteristic is a curve instead of a straight line. The curve has a steep slope in the range of small beam currents and has a slight slope in the range of large beam currents. This means that when the beam loading is light the energy of the electrons can rapidly increase with the beam loading decreasing; when the beam loading is heavy the energy will slowly descend with the beam current increasing