Betatron

The betatron is inductive accelerator of electrons. The betatron is used for the treatment of malignant tumors (betatron therapy). Electron beams used for irradiation of tumors with shallow groundwater occurrences (3-5 cm) (see E-therapy); hard bremsstrahlung betatron is used for deep therapy.

The betatron - electronic accelerator, intended to generate a beam of high-energy electrons or hard x-show (bremsstrahlung). Most of the latter are concentrated in a relatively small solid angle, the higher the radiation energy, the deeper is maximum dose. In the USSR for honey. objectives developed betatrons 25 MeV (type B-4E) and 15 MeV (type B-15/4,5).
The betatron consists of an electromagnet with annular gap, fed by alternating current. In the annular gap is set accelerator chamber, inside of which created a deep vacuum (10-6 mm RT. Art.). Injector, mounted in one of the pipes accelerator camera, injects into her electrons at a voltage of 40% to 50 kV at the moment when the magnetic field corresponds to this tension. The electrons are captured by the magnetic field and begin to move on the equilibrium of a closed orbit inside the accelerator camera. For one revolution every electron in its orbit takes the energy equal to the voltage of the electric field (voltage bypass). If this voltage is equal to, for example, 25 eV, and the speed of 1 million, then the energy acquired by an electron during acceleration, will be 25 MeV. After the acceleration in special coil serves a current pulse that shifts the accelerated electrons from orbit and sends them to the target, where they inhibit, giving energy in the form of x (gamma) radiation. If the current pulse to file in the other coils, accelerated electrons, beating the target will come out of betatron through a special window in accelerator chamber (beta-radiation). Side betatron, facing up to the patient to be fitted with a lead shield, absorbing unused radiation. In protection there Kallimarmaro hole, the size of which corresponds to the back field exposure.
The betatron type B-4E can be installed so that the axis of the beam is separated from the floor to 1650 and 1050 mm Betatron can be rotated around an axis to any angle within 30 degrees up and 90 degrees downward from the horizontal.
There are collimators, creating different fields of radiation. The intensity of x-radiation at a distance of 1 m from the target is 30 rubles for 1 min. (at 25 MeV). The intensity of the electron radiation respectively 130 R a 1 minutes (18-23 MeV).