Plasma behaviour near a separatrix magnetic surface in the JFT-2a tokamak

Maeda, Hideaki; Shimomura, Y.; Kitsunezaki, A.; Ohtsuka, H.; Nagami, M.; Funahashi, A.; Matoba, T.; Kasai, S.; Takeuchi, Hiroshi; Takahashi, Koki; Kumagai, K.; Tokutake, T.; Nagashima, Takashi; Ueda, N.; Yoshikawa, Masayuki

doi:10.1088/0029-5515/16/1/018

Cited by 7 publications

(12 citation statements)

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“…The procedure of the present experiment is to measure the local values of q, I s and T e , with pertinent probes scanned in the divertor region, and to calculate 7. As noted in previous experiments [3,5], heat fluxes in the divertor are highly asymmetric about the median plane, and high-energy electrons escaping from the main plasma cause this asymmetry since they can exist on one side of the divertor until they are annihilated at the neutralizer plate. Hereafter, we shall distinguish the two sides of the divertor -with respect to the median plane -as the electron side and the ion side of the divertor.…”

Section: Introductionmentioning

confidence: 57%

“…The transient heat flux as a function of the bias voltage 0 is given by substituting 0 instead of 0 O in Eq. (5). It is with this equation that the timeintegrated heat flux shown in Fig.…”

Section: Ne = 2_ "Ek ( Exp I -mentioning

confidence: 86%

“…This paper describes an experimental study on the thermal interaction between plasma and walls in the divertor tokamak, DIVA [1][2][3][4][5]. The other interactions relevant to the release of the metal impurity, such as ion sputtering and arcing, are discussed in Ref.…”

Section: Introductionmentioning

confidence: 99%

“…It is well known that a sheath potential built up in front of an electrically insulated conducting plate plays an important role as a thermal barrier. The heat flux q (Wcm~2) towards an electrically insulated conducting plate in a plasma is written as follows [7]: Q = 7 Is T e (1) where I s (A cm 2 ) is the ion saturation current density, T e (eV) is the electron temperature and y is called a heat transmission rate; 7 = 7.8 for hydrogen plasma of T e = Ti, where Ti is the proton temperature.…”

Section: Introductionmentioning

confidence: 99%

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Heat flux to the material surfaces in a tokamak

Kimura¹,

Maeda²,

Ueda³

et al. 1978

Nucl. Fusion

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Section: Introductionmentioning

confidence: 57%

“…The transient heat flux as a function of the bias voltage 0 is given by substituting 0 instead of 0 O in Eq. (5). It is with this equation that the timeintegrated heat flux shown in Fig.…”

Section: Ne = 2_ "Ek ( Exp I -mentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Heat flux to the material surfaces in a tokamak

Kimura¹,

Maeda²,

Ueda³

et al. 1978

Nucl. Fusion

Self Cite

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“…In divertor tokamak experiments, a many-fold difference is always observed in the values of power flux flowing to the target plates and consequently in corresponding divertor plasma conditions in the inner and outer legs of the divertor (inout asymmetry; see, for example, Ref. [1]) or in the legs geometrically symmetric about the torus midplane [2,3] (updown, or vertical, asymmetry). Reversal of the direction of the toroidal magnetic field alters the characteristics of these asymmetries [4].…”

Section: Introductionmentioning

confidence: 99%

Plasma flow asymmetries in the natural helical divertor of anl= 3 torsatron and their relation to particle losses

et al. 2002

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In the l = 3/m = 9 Uragan-3M (U-3M) torsatron (R 0 = 1 m, ā ≈ 0.12 m, B φ = 0.72 T, ι( ā)/2π ≈ 0.4), an open helical divertor is realized. A hydrogen plasma with ne ≈ 2 × 10 18 m −3 , T e ≈ 0.3 keV, T i ≈ 0.1 keV is produced and heated by RF fields (ω ≈ ω ci ). The flows of diverted plasma are detected by 78 plane Langmuir probes aligned poloidally in the spacings between the helical coils in two geometrically symmetric poloidal cross-sections of the torus. In measurements of the distributions of ambipolar (e.g. the ion saturation current I s ) and non-ambipolar (e.g. the current to a grounded probe I p ) plasma flows, a strong vertical asymmetry of these distributions is observed, its main characteristics being a many-fold difference in the values of I s in the outgoing flows in the upper and lower parts of the torus and the opposite signs of I p in these flows, with the positive current corresponding to the larger ambipolar flow of the diverted plasma. Reversal of the direction of the toroidal magnetic field results in the reversal of the asymmetry, with the larger flux (and I p > 0) always flowing in the ion B × ∇B drift direction. On this basis, it is concluded that the asymmetry is related to direct (non-diffusive) losses of charged particles from the confinement volume. This conclusion is validated by numerical modelling of thermal and fast particle orbits in U-3M, where qualitative agreement has been revealed between the calculated distribution of the angular co-ordinates of lost particles and the measured poloidal distributions of the flows of diverted plasma.

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