Study on beam current extraction and magnetic circuit design of microwave negative ion source for sealed neutron tube

Abstract

A new structure of microwave ion source was designed to improve the ion beam intensity of sealed neutron tube, and the beam extraction simulation of microwave negative ion source was carried out. In this paper, we studied the magnetic field of microwave ion source and designed a multiple magnetic pole configurations system by magnetic field trap the fast electrons to improve the plasma density in the ion source chamber. Compared with the traditional double magnetic ring, the microwave ion source with multiple pole magnetic structure is stronger in limiting ions, thus generating a higher negative ion current. Simultaneously the multiple magnetic pole configurations design has a certain inhibitory effect on electrons. To improve the quality of the extraction beam, a magnetic filter with an external magnet and a multihole filtration system were set up, which can effectively filter the electrons in the extraction beam. The multihole design improves the uniformity of thermal load of the target. Moreover, multihole extraction system can effectively reduce the interference of the target on the ion source and has good stability. The kind microwave ion source could be applied to make sealed neutron tubes with good properties.