The Large Helical Device (LHD) now under construction is a heliotron/torsatron device with a closed divertor system. The edge LHD magnetic structure has been studied in detail. A peculiar feature of the configuration is the existence of edge surface layers, a complicated three dimensional magnetic structure which does not, however, seem to hamper the expected divertor functions. Two divertor operational modes are being considered for the LHD experimenthigh density, cold radiative divertor operation as a safe heat removal scheme and high temperature divertor plasma operation. In the latter operation, a divertor plasma with a temperature of a few keV, generated by efficient pumping, is expected to lead to a significant improvement in core plasma confinement. Conceptual designs of the LHD divertor components are under way.
New design approaches are proposed for the LHD-type heliotron D-T demo-reactor FFHR2 to solve the key engineering issues of blanket space limitation and replacement difficulty. A major radius over 14 m is selected to permit a blanket-shield thickness of about 1 m and to reduce the neutron wall loading and toroidal field, while achieving an acceptable cost of electricity COE. Two sets of optimization are successfully carried out. One is to reduce the magnetic hoop force on the helical coil support structures by adjustment of the helical winding coil pitch parameter and the poloidal coils design, which facilitates expansion of the maintenance ports. The other is a long-life blanket concept using carbon armor tiles that soften the neutron energy spectrum incident on the self-cooled Flibe-RAF blanket. In this adaptation of the Spectral-shifter and Tritium breeder Blanket (STB) concept a local tritium breeding ratio TBR over 1.2 is feasible by optimized arrangement of the neutron multiplier Be in the carbon tiles, and the radiation shielding of the super-conducting magnet coils is also significantly improved. Using the constant cross sections of helically winding shape, the "screw coaster" concept is proposed to replace in-vessel components such as the STB armor tiles. The key R&D issues to develop the STB concept, such as radiation effects on carbon and enhanced heat transfer of Flibe, are elucidated.
Abstract. We propose a version of Type-Logical Categorial Grammar (TLCG) which combines the insights of standard TLCG (Morrill 1994, Moortgat 1997 in which directionality is handled in terms of forward and backward slashes, and more recent approaches in the CG literature which separate directionality-related reasoning from syntactic combinatorics by means of λ-binding in the phonological component (Oehrle 1994, de Groote 2001, Muskens 2003. The proposed calculus recognizes both the directionality-sensitive modes of implication (/ and \) of the former and the directionality-insensitive mode of implication tied to phonological λ-binding in the latter (which we notate here as |).Empirical support for the proposed system comes from the fact that it enables a straightforward treatment of Gapping, a phenomenon that has turned out to be extremely problematic in the syntactic literature including CG-based approaches.
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