The linear electron accelerator is an accelerator of charged particles in which the trajectory of the accelerated particles (electrons) is straightforward. The acceleration of electrons is carried out using a high-frequency field in a circular waveguide. If the propagation velocity of the voltage wave and particles are equal, then the particles will accelerate all the time. Accelerators operating on this principle are called resonant.
Linear electron accelerators were created after the Second World War, when very powerful high-frequency oscillators appeared. All of them operate in a pulsed mode (see. Pulsed radiation). Compared with the betatron (see) and the synchrotron, the linear electron accelerator has several advantages: the simplicity of removing the electron beam from the accelerator chamber and changing the electron energy in the beam, high intensity. The disadvantages of the accelerator are higher cost and complexity of the design. A number of countries have 1000 MeV accelerators used for research in nuclear physics, and a large number of machines designed for lower energies.
In the USSR, linear electron accelerators for energy of 5 and 35 MeV, used for radiation therapy of deep-lying tumors, were developed for medical purposes. Both the electron beam and the bremsstrahlung of electrons incident on a target from a heavy element are used. Electrons due to the final mileage allow you to get the maximum dose at a certain depth. The position of the maximum dose can be easily changed by changing the energy of the electrons. Accelerators used in medicine are supplied with a special output device with a set of collimators for obtaining irradiation fields of certain sizes and filters that equalize the dose over the field.
In the literature, these devices are called X-ray heads. Due to the high power of the beam of accelerated electrons, accelerators have been used for sterilization of medical instruments and food products, for research in the field of radiation chemistry and for the production of isotopes.