Conventionally, the quantitative determination of atoms contained in soil or sewage is required in terms of the environmental pollution. In this case, in general, soil or sewage must be subjected to pretreatment, such as drying or being dissolved in a chemical. Furthermore, the apparatuses used are large and are impossible to carry. It is therefore difficult to perform a component analysis at the site of pollution. The component analysis requires atomization of elements composing a substance. It is known that the atomization is performed by chemical methods or physical methods using a laser or plasma. In the chemical methods, because different elements require different treatments, it is difficult to measure multiple elements simultaneously. Furthermore, when a laser is miniaturized for convenience of carrying, the laser has a reduced power and low analytical sensitivity. Furthermore, a solid containing a liquid (or a solid in a liquid) requires complete vaporization of the liquid and vaporization of the solid. Direct use of a solid containing a liquid requires a higher-power laser, which is difficult to miniaturize. In particular, it is desired that the atomic analysis of a solid contained in a waste fluid be performed directly with the waste fluid. However, a portable laser cannot be used in such an analysis of a solid contained in a waste fluid.
On the other hand, a plasma generator for use in the atomic analysis using plasma is known by Patent Document 1. Patent Document 1 discloses an apparatus that generates helium plasma, which has the highest atomization capability. Since a helium gas has a very high excitation temperature, surrounding walls that generate plasma must be cooled. A helium gas may be used to cool the surrounding walls. However, helium has a high thermal conductivity and exhibits extensive thermal diffusion. If a helium gas is fed in the axial direction for cooling, therefore, the energy of helium is dissipated into the atmosphere.
According to Patent Document 1, to solve this problem, a helium gas is fed spirally into an outer discharge tube to reduce the flow rate in the axial direction, thus forming ring-shaped plasma around the axis. A gas to be analyzed is supplied into the ring-shaped plasma.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 9-147790