[en] The average concentration of SF6 in the atmosphere of the Northern Hemisphere has been rising since the 1970s. By comparing the SF6 concentration of groundwater and the historical record of atmospheric concentration, groundwater can be dated from about the 1970s to the present. We therefore need to collect samples using an SF6-free pump or similar device, which prevents contact of the sample with the atmosphere, thus ensuring that atmospheric SF6 does not mix with the sample. Reduction of both the time and effort for water sampling caused by this constraint will result in more efficient investigation. We have proposed a simple manually operated water sampling method using a well water sampler (well bailer bucket) for SF6-based dating of groundwater. During the process of groundwater sampling using a well bailer bucket, the sample comes into contact with the atmosphere. The calculation of SF6 transfer from gas to liquid phase indicates that during this process, the theoretical increase in the SF6 concentration of groundwater is less than 1%, which corresponds to a residence time of 0.2 years and is within the range of analysis accuracy of 3%. This simplified method using a well bailer bucket (the simple method) can obtain the same results as th e ordinarily used sampling method (the conventional method) in which water samples are collected without contact with the atmosphere. The difference between the SF6 concentration of the conventional method and that of the simple method is about 2% of the average value of both, which corresponds to about 0.5 years of apparent residence time. Even if sampled water comes into contact with the atmosphere during the sampling process by using the simple method, the dissolution of atmospheric SF6 into the sampled water is extremely small. Depending on the sampling depth and survey equipment, the simple method can reduce the sampling time (for example, a reduction of 60 to 70%, including preparation for sampling). The simple method, which does not use a pump, has no sampling depth restriction due to the pump head. Furthermore, the simple method can lessen the weight of equipment, reducing the burden on survey participants

[en] Full text: The dipole plasma exhibits strong heterogeneities in field strength, density, temperature, etc., while maintaining the holistic balance. Enquiring into the internal structures, we reveal the fundamental self-organizing mechanisms operating in their simplest realization (as commonly observed in astronomical systems). Three new findings are reported from the RT-1 experiment: i) Creation of a high-energy electron core (similar to the radiation belts in planetary magnetospheres) is observed for the first time in a laboratory system. Highenergy electrons, 3-15 keV, produced by an electron cyclotron heating (ECH), accumulate in a “belt” located in the low density region (high-β value ∼ 1 is obtained by increasing the high-energy component up to 70% of the total electrons). ii) The dynamical process of the “inward diffusion” (a spontaneous mechanism of creating density gradient) has been analyzed by perturbing the density by gas injection. iii) By a system of coherence-imaging spectroscopy, the profiles of the ion temperature and flow velocity have been measured. The effect of the ion cyclotron resonance frequency (ICRF) heating has been visualized. These results advance our understanding of transport and self-organization not only in dipole plasmas, but also in general magnetic confinement systems relevant to fusion plasmas. (author)

[en] Dipole plasma exhibits strong heterogeneities in field strength, density, temperature and other parameters, while maintaining a holistic balance. Our study of the internal structures reveals the fundamental self-organizing mechanisms operating in their simplest realization (as commonly observed in astronomical systems). Three new findings are reported from the RT-1 experiment. The creation of a high-energy electron core (similar to the radiation belts in planetary magnetospheres) is observed for the first time in a laboratory system. High-energy electrons (3–15 keV), produced by electron cyclotron heating, accumulate in a ‘belt’ located in the low-density region (high-beta value ∼1 is obtained by increasing the high-energy component up to 70% of the total electrons). The dynamical process of the ‘up-hill diffusion’ (a spontaneous mechanism of creating density gradient) has been analyzed by perturbing the density by gas injection. The spontaneous density formation in the laboratory magnetosphere elucidates the self-organized plasma transport relevant to a planetary magnetosphere. The coherence-imaging spectroscopy visualized the two-dimensional profiles of ion temperature and flow velocity in the ion cyclotron resonance frequency heating. The ion temperature and flow were enhanced globally, and particularly along the magnetic field lines near the levitation magnet. These results advance our understanding of transport and self-organization not only in dipole plasmas, but in general magnetic confinement systems relevant to fusion plasmas. (paper)

[en] In order to clarify the difference between the local structures of Fe³⁺ and those of Fe²⁺ ions in a semiconductive phosphate (10V₂O₅-30Fe₂O₃-60P₂O₅) glass, the temperature dependencies of the isomer shift (IS), quadrupole splitting (QS) and absorption area (AR) for Fe³⁺ and Fe²⁺ ions were measured. Debye temperatures (θ_D) for Fe³⁺ and Fe²⁺ ions were determined to be 318 ± 29 K and 223 ± 18 K, respectively, from the temperature dependence of the absorption area (AR). From the temperature dependence of the quadrupole splitting (QS), B strength parameters for Fe³⁺ and Fe²⁺ ions, which are the coefficients for the T^3/2 term, were deduced. It was found that in this phosphate glass, Debye temperatures θ_D(AR) were consistent with those obtained using the relation of the B parameter to Debye temperature described in the literature. Also from the temperature dependence of the isomer shift, the difference between the thermal effects except the second-order Doppler shift for Fe³⁺ ions and those for Fe²⁺ ions was compared. (orig.)