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Recent 70-GHz, 0.4-MW ECH experiments in Heliotron J have revealed the existence of the spontaneous confinement transition, like that of the H-mode, at rather low threshold line-averaged densities of 1.2-1.6 × 10 19 m -3 . The transition was discovered in two edge-iota windows: one is 0.54 < ι (a)/ 2π < 0.56 at separatrix discharge plasmas and the other is 0.62 < ι (a)/2π < 0.63 at partial walllimiter discharge plasmas. The energy confinement time for the separatrix discharge plasmas was found to be enhanced beyond the normal ISS95 scaling in the transient H-mode phase, being 50% longer than that in the "before transition" phase. Keywords:heliotron, stellarator, H-mode, transition phenomena, confinement improvementThe research program regarding Heliotron J (a low shear helical-axis heliotron having four periods, ι /2π = 0.557, R = 1.2 m, and a < 0.2 m) is focused on the establishment, characterization, and improvement of plasma confinement in the next-generation heliotron line [1,2]. The characterization of 70-GHz, 0.4-MW ECH plasma confinement in Heliotron J was studied with special regard to its magnetic configuration effects [3]. The experiments revealed that the energy confinement characteristics in the normal confinement mode (T e < 1.5 keV, T i CX < 0.2 keV, -n e = (0.2 -3.0) × 10 19 m -3 , W p diam < 3 kJ, and B 0 < 1.5 T) indicate the existence of "good" confinement plasmas whose energy confinement time becomes 1.5-2 times longer than the ISS95 scaling [4]. At present, it is not clear whether these good confinement plasmas are essentially different from those of the traditional ISS95 scaling. Beside these good confinement plasmas, the spontaneous confinement improvement mode, like that of the H-mode, was author's e-mail: sano@iae.kyoto-u.ac.jp recently discovered during the ECH with strong gas puffing in two edge-iota windows. Figure 1 shows the time evolution of the observed H-mode behavior in which the sudden drops in both H α and SOL probe signals and the subsequent strong rises in both line-integrated density and diamagnetic energy content were observed at the H-mode transition. In the case of the vacuum edge iota ι (a)/2π = 0.542, the peak increment of the plasma energy content was about 70% while that in the case of ι(a)/2π = 0.623 was about 30%. These confinement improvements remained transient on an energy confinement timescale and the post-transition steady-state phase was not yet attained. ECE measurements revealed that, after the transition, the core electron temperature inside r/a < 2/3 slightly increased or was well maintained despite the strong increase in density. On the other hand, in the SOL region, Langmuir probe measurements revealed that, after the transition, the SOL density fluctuation also dropped in the fre-

Two new transitions in Re 188m were found which are responsible for the 18.7-min half-life of this isomer. The energies and branching ratios of these transitions which originate from a 6-state at 171.9 keV, are 2.4 keV (57%) and 15.9 keV (43%). Their multipole orders are M3. Each transition is followed by an Ml transition, of 105.9 and 92.4 keV, respectively, both terminating in the first excited (2-) state at 63.58 keV, which decays by an Ml transition to the ground state. The ground state and the first two excited states appear to be members of a rotational band with K-1 -, whereas the 3rd and 4th excited states can be interpreted as composed of the same proton orbit as that of the ground state, but of different neutron orbits. The thermal neutron activation cross section of Re

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