Analysis of the normal transition event of the LHD helical coils

Yanagi, N.; Imagawa, S.; Mito, T.; Iwamoto, A.; Chikaraishi, H.; Hamaguchi, S.; Nishimura, A.; Satow, T.; Nakamura, Y.; Satoh, Shuichi; Motojima, O.; Gavrilin, A.V.

doi:10.1109/77.828308

Cited by 18 publications

(4 citation statements)

References 8 publications

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“…It is clearly seen that the propagation velocity is much faster in the downstream side of the transport current than that in the upstream side, and it hence reveals an asymmetry of normal-zone propagation, as was observed in the previous conductor tests. It should be particularly noted that in the current region of 10.7 to 11.4 kA, the normal-zone propagates only in the downstream side, which is also the same phenomenon as that was observed in short sample conductors [6], a small R&D coil [3] and the LHD helical coils [8]. Fig.…”

Section: Experimental Observations Of Asymmetrical Normal-zone Prmentioning

confidence: 81%

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Asymmetrical Normal-Zone Propagation Observed in the Aluminum-Stabilized Superconductor for the LHD Helical Coils

Yanagi

Imagawa

Hishinuma

et al. 2004

IEEE Trans. Appl. Supercond.

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Abstract-Transient normal-transitions have been observed in the superconducting helical coils of the Large Helical Device (LHD). Stability tests have been performed for an R&D coil as an upgrading program of LHD, and we observed asymmetrical propagation of an initiated normal-zone. In some conditions, a normal-zone propagates only in one direction along the conductor and it hence forms a traveling normal-zone. The Hall electric field generated in the longitudinal direction in the aluminum stabilizer is a plausible candidate to explain the observed asymmetrical normal-zone propagation.

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Section: Experimental Observations Of Asymmetrical Normal-zone Prmentioning

confidence: 81%

“…It has been observed that the pool-cooled helical coils (major radius 3.9 m, minor radius 1 m and toroidal pitch number 10) allow transient normal-transitions at a current and magnetic field slightly lower than the specified operation point (13 kA and 6.9 T at temperature 4.4 K) [2], [3].…”

mentioning

confidence: 99%

Asymmetrical Normal-Zone Propagation Observed in the Aluminum-Stabilized Superconductor for the LHD Helical Coils

Yanagi

Imagawa

Hishinuma

et al. 2004

IEEE Trans. Appl. Supercond.

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“…While the excitation tests of the LHD cooled by Liq. He I, the "dynamic one-side propagation" of a traveling normal zone initiated by a certain thermal disturbance was observed at a current and a magnetic field slightly lower than the designed operating point [1]. This "traveling normal zone" did not lead to the quench of the coil.…”

Section: Introductionmentioning

confidence: 96%

Transient Stability of Large Helical Device Conductor With and Without Aluminum Stabilizer (2)—Numerical Results

Ikuta

Ohya

Shirai

et al. 2007

IEEE Trans. Appl. Supercond.

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Numerical simulations were carried out on the transient stability of large-scale composite superconductors against a thermal disturbance, that is, a LHD conductor, which consists of a NbTi/Cu Rutherford cable, a pure aluminum stabilizer, and a copper sheath around the composite. The simulations were also performed on an Al-less test conductor, which is a LHD conductor without the Al stabilizer and a half of the copper sheath. The recovery and propagation characteristics of an initiated normal zone were simulated to know the effect of the Al stabilizer on the transient stability of the LHD conductor cooled by Liq.He II. The normal zone propagation initiating current at a certain magnetic flux density for the LHD conductor was compared with that for the Al-less test conductor. Asymmetrical propagation of the normal zone appears even in the LHD based conductor without the Al stabilizer. The range of the transport current, which lead to the one-side propagation, is narrower than those for the LHD conductor. It is confirmed that the Al stabilizer in LHD conductor plays main role in the asymmetrical normal zone propagation. The high performance of the He II cooling in the transient state for the Al-less test conductor makes the normal zone initiating current up to the same level of that for the super-stabilized LHD conductor. It is confirmed that only a slight area of the thick aluminum works as a stabilizer at the transient state because of its low magnetic diffusion factor.

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“…It had been confirmed in the past that the numerical calculation well simulates the voltage waveforms which are observed in short sample tests [5] as well as in small R&D coil tests [6]. Thus, we have tried to apply this code to analyze the normaltransition events observed in the helical coils.…”

Section: B Numerical Simulation Of Normal-zone Propagationmentioning

confidence: 99%

Analysis on the cryogenic stability and mechanical properties of the LHD helical coils

Yanagi

Imagawa

Mito

et al. 2002

IEEE Trans. Appl. Supercond.

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Analysis of the normal transition event of the LHD helical coils

Cited by 18 publications

References 8 publications

Asymmetrical Normal-Zone Propagation Observed in the Aluminum-Stabilized Superconductor for the LHD Helical Coils

Asymmetrical Normal-Zone Propagation Observed in the Aluminum-Stabilized Superconductor for the LHD Helical Coils

Transient Stability of Large Helical Device Conductor With and Without Aluminum Stabilizer (2)—Numerical Results

Analysis on the cryogenic stability and mechanical properties of the LHD helical coils

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