Superconducting current feeder system for the large helical device

Yamada, S.; Mito, T.; Chikaraishi, H.; Tanahashi, S.; Kitagawa, S.; Yamamoto, Junya; Motojima, O.; Uede, T.; Hiue, H.; Yasukawa, Y.; Itoh, I.

doi:10.1109/20.511362

Cited by 17 publications

(5 citation statements)

References 4 publications

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“…We constructed a 20 m long full scale mock-up. Performance tests were carried out, and we confirmed that the minimum propagating current is higher than 32.5 kA and that current of up to 40 kA can flow without quenching [11].…”

Section: Randd Of Superconducting Coilsmentioning

confidence: 64%

Overview of the Large Helical Device project

Iiyoshi¹,

Komori²,

Ejiri³

et al. 1999

Nucl. Fusion

268

105

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OVERVIEW OF THE LARGE HELICAL DEVICE PROJECT. The Large Helical Device (LHD) has successfully started running plasma confinement experiments after a long construction period of eight years. During the construction and machine commissioning phases, a variety of milestones were attained in fusion engineering which successfully led to the first operation, and the first plasma was ignited on 31 March 1998. Two experimental campaigns are planned in 1998. In the first campaign, the magnetic flux mapping clearly demonstrated a nested structure of magnetic surfaces. The first plasma experiments were conducted with second harmonic 84 and 82.6 GHz ECH at a heating power input of 0.35 MW. The magnetic field was set at 1.5 T in these campaigns so as to accumulate operational experience with the superconducting coils. In the second campaign, auxiliary heating with NBI at 3 MW has been carried out. Averaged electron densities of up to 6 × 10 19 m-3 , central temperatures ranging from 1.4 IAEA-F1-CN-69/OV1/4 2 to 1.5 keV and stored energies of up to 0.22 MJ have been attained despite the fact that the impurity level has not yet been minimized. The obtained scarling of energy confinement time has been found to be consistent with the ISS95 scaling law with some enhancement.

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Section: Randd Of Superconducting Coilsmentioning

confidence: 64%

Overview of the Large Helical Device project

Iiyoshi¹,

Komori²,

Ejiri³

et al. 1999

Nucl. Fusion

268

105

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“…The superconducting flexible bus-line was developed for the current feeding system [9]. The bus-line consists of a pair of aluminium-stabilized superconducting cables and five coaxial corrugated stainless-steel tubes.…”

Section: Superconducting Magnetsmentioning

confidence: 99%

Achievement of high availability in long-term operation and upgrading plan of the LHD superconducting system

et al. 2007

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The Large Helical Device (LHD) that has been demonstrating high performance of heliotron plasma is the world's largest superconducting system. Availability higher than 98% has been achieved in a long-term continuous operation both in the cryogenic system and in the power supply system. It will be owing not only to the robustness of the systems but also to efforts of maintenance and operation. One big problem is shortage of cryogenic stability of a pair of pool-cooled helical coils. Composite conductors had been developed to attain the sufficient stability at high current density. However, it was revealed that a normal-zone could propagate below the cold-end recovery current by additional heat generation due to the slow current diffusion into a thick pure aluminum stabilizer. Besides, a novel detection system with pick-up coils along the helical coils revealed that normal-zones were initiated near the bottom of the coil where the field is not the highest. Therefore, the cooling condition around the innermost layers, the high field area, will be deteriorated at the bottom of the coil by bubbles gathered by buoyancy. In order to raise the operating currents, methods for improving the cryogenic stability have been examined, and stability tests have been carried out with a model coil and small coil samples. The coil temperature is planned to be lowered from 4.4 K to 3.5 K, and the operating current is expected to be increased from 11.0 kA to 12.0 kA that corresponds to 3.0 T at the major radius of 3.6 m.

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“…It maintains a rated current carrying capacity for 30 minutes, even if the coolants supplied to the SC bus line are accidentally stopped [6]. The minimum bending radius is determined to be 1.5 m, because of the installation routes.…”

Section: Sc Current Feeder Systemmentioning

confidence: 99%

Stable long-term operation of superconducting current-feeder system for the LHD

Yamada

Mito

Maekawa

et al. 2002

IEEE Trans. Appl. Supercond.

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Abstract-A superconducting (SC) current-feeder system is used as the current transmission lines for the experimental fusion device, LHD. It consists of nine flexible SC bus lines with total length of 497 m, and nine pairs of gas-cooled current leads. To avoid the propagation of the ice on the leads, the temperature of the terminals had been kept in the range between 5 and 20 degrees Celsius by the heaters. The measured voltage drops of all leads were less than 20 mV. The liquid helium levels of the leads and the sub-cooler tank will equalize by the siphon method. The total time of the coil excitations exceeds 3000 hours. We have demonstrated successfully that the SC current-feeder system was stable and easy to handle, and is useful for the SC experimental fusion device.

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Superconducting current feeder system for the large helical device

Cited by 17 publications

References 4 publications

Overview of the Large Helical Device project

Overview of the Large Helical Device project

Achievement of high availability in long-term operation and upgrading plan of the LHD superconducting system

Stable long-term operation of superconducting current-feeder system for the LHD

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