Beam-plasma type ion source for high-intensity ion beam

In a beam-plasma type ion source, the gas is effectively ionized by the microwave power (2 to 20 GHz) transferred from an electron beam through beam-plasma interactions, which are the interactions between the magnetically focused electron beam injection from the ion extractor and the plasma in the drift tube. A high-density and stable plasma is obtained in the drift tube by this beam-plasma discharge because of the microwave heating ionization and the feedback phenomenon which keeps the plasma density constant. When ions are extracted from the high-density plasma produced in the drift tube, they are accelerated in the opposite direction of the electron beam by the same electric field that accelerates the electron beam, and the space charge of the ion beam is highly neutralized by the injected electron beam near the ion extractor. Therefore, a high-intensity and well-confined ion beam is obtained. Moreover, although the extracted ion current increases, the emittance of the ion beam is kept low because of ions trapped in the negative-potential well induced by the electron beam near the ion extractor