The spherical inertial electrostatic confinement (SIEC) is a concept for electrostatically confining high-energy fuel ions in potential well. In ideal SIEC plasmas, the ions converge toward the center of the device, and their space charge forms a virtual anode. The cold electrons emitted from the cathode also converge toward the virtual anode, and are thought to create a virtual cathode inside the virtual anode. So far, neutrons (protons) more than 10⁸ n/s produced by D(d,n)³He (³He(d,p)⁴He) reactions have been observed on several devices. In parallel with the neutron/proton production, in some devices, the double peak in radial profile of the neutron/proton production rate was measured. On the other hand, in recent experiment using a spherical glow discharge as ion source, an operation mode in which the neutron production rate increases in proportion to 1.3-2.0th power of the discharged current was observed. To improve further the device performance, it is important to understand the physics of the SIEC plasmas. We have previously developed an analysis model for deuterium-gas system[1,2], and have explained the above phenomena[3].

In this paper, we consider deuterium-helium-3 gas system and investigate the dependence of proton production rate by ³He(d,p)⁴He reaction on discharged current for various ion/electron distribution functions. The ³He(d,p)⁴He fusion cross section more rapidly increases with increasing relative speed between beam ion and background gas compared with the D(d,n)³He one. It is revealed that in deuterium-helium-3 gas systems the proton production rate increases in proportion to more than a power of the discharged current more easily for lower discharged current than that in the deuterium-gas systems.

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