Study of a modified betatron with stellarator windings

An experimental study of injection, trapping, and acceleration of a high current electron beam in a modified betatron and and in a stellatron was conducted. An electron beam was generated in a betatron by continuous injection of electrons from a thermionic emitter into an evacuated toroidal vessel, while a strong toroidal magnetic field and a rising vertical field are applied. The beam is accelerated, as in conventional betatron by an induced toroidal electric field. Beam current of more than 200 A has been achieved. The acceleration continues until the vertical magnetic field reaches a certain value, then the beam is lost abruptly and hits the walls of the torus. When this happens a large x-ray burst is generated. The beam is accelerated even when the betatron flux condition is violated. It also was found that there is a large mismatch between the electron's energy and the vertical field. This field was controlled and changed after trapping in order to correct the mismatch; then, the beam's life is extended so that an electron energy of ∼1 MeV is reached. The stellatron utilizes a strong focusing field produced by four helical coils in a quadrupole configuration which were added to the modified betatron. It facilitates the use of short injection pulses and extends significantly the beam's lifetime so that electrons are accelerated longer and energies of up to ∼4 MeV are achieved