Initial plasma start-up using partial solenoid coils in Versatile Experiment Spherical Torus (VEST)

Chung, Kyoung−Jae; An, Younghwa; Jung, Bokyung; Lee, H.Y.; Dang, Jeong-Jeung; Lee, J.W.; Yang, Jianhua; Jo, Junghyo; Choi, Donchan; Kim, Young-Gi; Na, Y.S.; Hwang, Y.S.

doi:10.1016/j.fusengdes.2013.02.006

Cited by 13 publications

(4 citation statements)

References 11 publications

(13 reference statements)

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“…Here we report on the effect of poloidal magnetic field configuration on ECH pre-ionization and the subsequent start-up in VEST (versatile experiment spherical torus) [19][20][21][22][23]. We then propose an alternative poloidal magnetic field configuration, i.e.…”

Section: Nuclear Fusionmentioning

confidence: 99%

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Efficient ECH-assisted plasma start-up using trapped particle configuration in the versatile experiment spherical torus

Lee

et al. 2016

Nucl. Fusion

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An efficient and robust ECH (electron cyclotron heating)-assisted plasma start-up scheme with a low loop voltage and low volt-second consumption utilizing the trapped particle configuration (TPC) has been developed in the versatile experiment spherical torus (VEST). The TPC is a mirror-like magnetic field configuration providing a vertical magnetic field in the same direction as the equilibrium field. It significantly enhances ECH pre-ionization with enhanced particle confinement due to its mirror effect, and intrinsically provides an equilibrium field with a stable decay index enabling prompt plasma current initiation. Consequently, the formation of TPC before the onset of the loop voltage allows the plasma to start up with a lower loop voltage and lower volt-second consumption as well as a wider operation range in terms of ECH pre-ionization power and H2 filling pressure. The TPC can improve the widely-used field null configuration significantly for more efficient start-up when ECH pre-ionization is used. This can then be utilized in superconducting tokamaks requiring a low loop voltage start-up, such as ITER, or in spherical tori with limited volt-seconds. The TPC can be particularly useful in superconducting tokamaks with a limited current slew-rate of superconducting PF coils, as it can save volt-second consumption before plasma current initiation by providing prompt initiation with an intrinsic stable equilibrium field.

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Section: Nuclear Fusionmentioning

confidence: 99%

“…The main device parameters of VEST are R 0 = 0.4 m, R 0 /a > 1.3 and B T = 0.1 T on the axis [19][20][21][22][23]. For ECH preionization, an ECH power of up to 6 kW with a frequency of 2.45 GHz and X-mode polarization was injected from the low field side.…”

Section: Experimental Set-up For Plasma Start-up Experiments In Vestmentioning

confidence: 99%

Efficient ECH-assisted plasma start-up using trapped particle configuration in the versatile experiment spherical torus

Lee

et al. 2016

Nucl. Fusion

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“…22) also uses similar merging-compression techniques with all external PF coils. 16,154 E. Inductive drive based start-up A number of scenarios utilizing magnetic induction that includes a conventional central ohmic solenoid have been also investigated by the ST community. One variation of inductive plasma start-up uses vertical field coils with currents initially in the negative direction.…”

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confidence: 99%

Recent progress on spherical torus research

Ono

Kaita

2015

Physics of Plasmas

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The spherical torus or spherical tokamak (ST) is a member of the tokamak family with its aspect ratio (A = R0/a) reduced to A ∼ 1.5, well below the normal tokamak operating range of A ≥ 2.5. As the aspect ratio is reduced, the ideal tokamak beta β (radio of plasma to magnetic pressure) stability limit increases rapidly, approximately as β ∼ 1/A. The plasma current it can sustain for a given edge safety factor q-95 also increases rapidly. Because of the above, as well as the natural elongation κ, which makes its plasma shape appear spherical, the ST configuration can yield exceptionally high tokamak performance in a compact geometry. Due to its compactness and high performance, the ST configuration has various near term applications, including a compact fusion neutron source with low tritium consumption, in addition to its longer term goal of an attractive fusion energy power source. Since the start of the two mega-ampere class ST facilities in 2000, the National Spherical Torus Experiment in the United States and Mega Ampere Spherical Tokamak in UK, active ST research has been conducted worldwide. More than 16 ST research facilities operating during this period have achieved remarkable advances in all fusion science areas, involving fundamental fusion energy science as well as innovation. These results suggest exciting future prospects for ST research both near term and longer term. The present paper reviews the scientific progress made by the worldwide ST research community during this new mega-ampere-ST era.

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“…UTST has utilized outer PF coils to provide the loop voltage for double plasma merging start-up but partial solenoids of VEST are expected to provide higher loop voltage with less stray field inside the vacuum vessel. Details of the device from key design concepts to commissioning results can be found in elsewhere [4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%