Extended Steady-State and High-Beta Regimes of Net-Current Free Heliotron Plasmas in the Large Helical Device

The performance of net-current free Heliotron plasmas has been developed by findings of innovative operational scenarios in conjunction with an upgrade of the heating power and the pumping/fueling capability in the Large Helical Device (LHD). Consequently, the operational regime has been extended, in particular, withregard to high density, long pulse length and high beta. Diversified studies in LHD have elucidated the advantages of net-current free heliotron plasmas. In particular, an Internal Diffusion Barrier (IDB) by combination of efficient pumping of the local island divertor function and core fueling by pellet injection has realized a super dense core as high as 5 10^20 m^-3, which stimulates an attractive super dense core reactor. Achievements of a volume averaged beta of 4.5 % and a discharge duration of 54-min. with a total input energy of 1.6 GJ (490 kW in average) are also highlighted. The progress of LHD experiments in these two years is overviewed with highlighting IDB, high beta and long pulse

National Institute for Fusion Science

"This annual report summarizes research activities at the National Institute for FusionScience (NIFS) between April 2007 and March 2008. The main objective of NIFS issymbolically expressed as the realization of a sun on the earth, generating a new, futuristicsource of energy. Human beings face a serious crisis concerning the change of the globalenvironment. It is obvious that the highest priority for us is to reduce the output of carbondioxide by developing a new energy source before a climate crisis occurs.

Feasibility of Artificial Geomagnetic Field Generation by a Superconducting Ring Network

The geomagnetic field shields the Earth from a large proportion of incoming radiation, andhas thus played a key role in sustaining life on Earth. Paleomagnetic measurements haveshown that the geomagnetic field undergoes many reversals of polarity. Continuousobservations of the field intensity have revealed a weakening of approximately 10% over thelast 150 years. If we assume that this trend indicates the onset of polarity reversal, thegeomagnetic field, particularly the dipole component, may weaken sufficiently over the nextthousand years to expose the atmosphere and nearby space to significantly increased levels ofcosmic and solar radiation. This may have a serious impact on vital infrastructure such assatellites, air traffic, and electricity networks, as well as on global climate changes, indicatingthat measures should better be taken in an attempt to support the limited protection providedby the remaining higher-order multipole fields and atmosphere. Here we show that a series ofplanet-encircling superconducting rings can provide an artificial geomagnetic field equivalentto 10% of the present-day field necessary to prevent adverse effects. A feasible systemconsists of 12 latitudinal high-temperature superconducting rings, each carrying 6.4 MAcurrent with a modest 1 GW of power requirement

Feasibility of Artificial Geomagnetic Field Generation by a Superconducting Ring Network

The geomagnetic field shields the Earth from a large proportion of incoming radiation, and has thus played a key role in sustaining life on Earth. Paleomagnetic measurements have shown that the geomagnetic field undergoes many reversals of polarity. Continuous observations of the field intensity have revealed a weakening of approximately 10% over the last 150 years. If we assume that this trend indicates the onset of polarity reversal, the geomagnetic field, particularly the dipole component, may weaken sufficiently over the next thousand years to expose the atmosphere and nearby space to significantly increased levels of cosmic and solar radiation. This may have a serious impact on vital infrastructure such as satellites, air traffic, and electricity networks, as well as on global climate changes, indicating that measures should better be taken in an attempt to support the limited protection provided by the remaining higher-order multipole fields and atmosphere. Here we show that a series of planet-encircling superconducting rings can provide an artificial geomagnetic field equivalent to 10% of the present-day field necessary to prevent adverse effects. A feasible system consists of 12 latitudinal high-temperature superconducting rings, each carrying 6.4 MA current with a modest 1 GW of power requirement

Design status of superconducting Large Helical Device

The Large Helical Device (LHD) is a superconducting heliotron/torsatron device. The SC coil system is composed of l=2 helical coils and three sets of poloidal coils with a total stored magnetic energy of 1.63 GJ. The m-number, l-number, major radius, coil minor radius magnetic field, plasma minor radius, and plasma volume are 10, 2, 3.9 m, 0.975 m, 4 T, 0.65 m, and 30 m^3, respectively. This is an alternative toroidal device which aims at producing plasmas extrapolatable to the reactor regime. The currentless steady operation is the final goal of the LHD program, and there is no danger from the major current disruptions. The material of the superconductor is NbTi, and the cooling systems are pool boiling for helical coils and forced flow for poloidal coils. Since the current density of the helical coils is as high as 53.3 A/mm^2 with a maximum experienced magnetic field strength of 9.6 T, refrigeration with superfluid helium is required. The LHD has a divertor to control the steady particle recycling and to improve the confinement potential. The vacuum vessel has a dumbbell-shaped poloidal cross section, which makes it possible to install the closed divertor chamber. The necessary R&D programs and detailed design are describe

Drain System Around the Underground Cavern

In recent years, construction or planning of large-scale underground structures, such as underground power plants, underground oil storage plants and nuclear power plants have been coming into consideration in Japan. To construct such as large-scale underground structures, one of the most important problems is to make clear beforehand the behavior of groundwater around these structures and the other is to carry out proper countermeasure of groundwater, so that these structures can be constructed safely and maintained stability over a long time period. This report describes the results of theoretical studies on the drain systems and at the same time, discusses the drain systems around the underground cavern for the practical underground power stations

A combination of hard and soft templating for the fabrication of silica hollow microcoils with nanostructured walls

Hollow silica microcoils have been prepared by using functionalized carbon microcoils as hard templates and surfactant or amphiphilic dye aggregates as soft templates. The obtained materials have been characterized by electron and optical microscopy, nitrogen sorption and small angle X-ray scattering. The obtained hollow microcoils resemble the original hard templates in shape and size. Moreover, they have mesoporous walls (pore size ≈ 3 nm) with some domains where pores are ordered in a hexagonal array, originated from surfactant micelles. The obtained silica microcoils also show preferential adsorption of cationic fluorescent dyes. A mechanism for the formation of silica microcoils is proposed