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Description
A microwave ion source is a long-life ion source because of few expendable items. Therefore, it is useful for various applications in industrial and medical fields such as ion implantations of semiconductors and particle therapies. We have previously reported on development of a microwave ion source for ion implantations. The magnetic field of the microwave ion source is generated by electromagnets which consist of two coils and iron yokes, and its magnetic field was a non-mirror magnetic field, what is called off-resonance. In addition, no magnets were installed to generate a cusp magnetic field. Therefore, the electron temperature in the plasma was low and it was hard to ionize molecules which have strong chemical bonds, e.g. BF$_{3}$. This ion source was suitable for production of high intensity beams of singly charged ions and ions of molecules whose chemical bonds are week. However, it was hard to produce highly charged ions and ions of strong chemical bond molecules. Thus, in order to produce high intensity ions beam of these molecules, we started to develop a new microwave ion source. In this paper, we report on development of a new plasma chamber and new electromagnets which consist of three coils and iron yokes. These electromagnets are capable of generating both a mirror magnetic field and a non-mirror magnetic field by tuning the current of each coil. The mirror magnetic field is expected to strengthen confinement of electrons in the plasma for production of highly charged ions or ions of gases whose chemical bonds are strong. In the case of the non-mirror magnetic field, the magnetic field in the plasma chamber is higher than the electron cyclotron resonance (ECR) magnetic field to produce intense beams singly charged ions. Furthermore, we also report on development of permanent magnets to generate a cusp magnetic field to generate a radial confinement effect.
