The Ohmic heating of a spheromak to 100 eV

Jarboe, T.R.; Barnes, Cris W.; Henins, I.; Hoida, H.W.; Knox, S.O.; Linford, R.K.; Sherwood, A.R.

doi:10.1063/1.864495

Cited by 38 publications

(36 citation statements)

References 13 publications

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“…Heating due to magnetic energy dissipation has previously been observed by Jarboe et al 23 on the CTX spheromak. This effect was found to heat the plasma up to 100 eV.…”

Section: Relation To Magnetic Cloudsmentioning

confidence: 61%

Taylor relaxation and λ decay of unbounded, freely expanding spheromaks

Yee

Bellan

2000

Physics of Plasmas

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A magnetized coaxial gun is discharged into a much larger vacuum chamber and the subsequent evolution of the plasma is observed using high speed cameras and a magnetic probe array. Photographic results indicate four distinct regimes of operation, labeled I-IV, each possessing qualitatively different dynamics, with the parameter gun ϭ 0 I gun /⌽ bias determining the operative regime. Plasmas produced in Regime II are identified as detached spheromak configurations. Images depict a donut-like shape, while magnetic data demonstrate that a closed toroidal flux-surface topology is present. Poloidal flux amplification shows that Taylor relaxation mechanisms are at work. The spatial and temporal variation of plasma ϭ 0 J /B indicate that the spheromak is decaying and expanding in a manner analogous to a self-similar expansion model proposed for interplanetary magnetic clouds. In Regime III, the plasma is unable to detach from the gun due to excess bias flux. Analysis of toroidal and poloidal flux as well as the profile shows that magnetic flux and helicity are confined within the gun for this regime.

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“…Heating due to magnetic energy dissipation has previously been observed by Jarboe et al 23 on the CTX spheromak. This effect was found to heat the plasma up to 100 eV.…”

Section: Relation To Magnetic Cloudsmentioning

confidence: 61%

Taylor relaxation and λ decay of unbounded, freely expanding spheromaks

Yee

Bellan

2000

Physics of Plasmas

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“…As the sustaining bank current peaks at 200 kA (near 1.2 ms) the mode activity drops to its lowest level, and T e in the center of the plasma rises to its highest value of 120 6 15 eV. Previously, T e above 100 eV has been reported only for decaying spheromaks disconnected from the source [12,13]. The measured electron density n e drops below 1 3 10 20 m 23 and remains constant during this phase as does the edge magnetic field at ϳ0.2 T. The low fluctuation period lasts for about 0.5 ms, or about a quarter of the total discharge time.…”

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confidence: 87%

Suppression of MHD Fluctuations Leading to Improved Confinement in a Gun-Driven Spheromak

et al. 2002

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Magnetic fluctuations have been reduced to approximately 1% during discharges on the Sustained Spheromak Physics Experiment by shaping the spatial distribution of the bias magnetic flux in the device. In the resulting quiescent regime, the safety factor profile is nearly flat in the plasma and the dominant ideal and resistive MHD modes are greatly reduced. During this period, the temperature profile is peaked at the magnetic axis and maps onto magnetic flux contours. Energy confinement time is improved over previous reports in a driven spheromak.

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“…5, was referred to as the slow formation scheme and which uses both a metallic liner and figure-8 coils for n= 1 stabilization. For the results reported here typical parameters are IJ5I < 6 kG, n^ (l-5)x 10 15 cm" 3 , T e = 5 eV, and the separatrix radius in the midplane is about 10-11 cm. Since the Alfv&n transit time across the minor radius is less than f jusec there is good reason to expect that after about 5 jisec the configuration should be in mechanical equilibrium.…”

mentioning

confidence: 98%