Constraining the divertor heat width in ITER

D. G. Whyte; B. LaBombard; J. W. Hughes; B. Lipschultz; J. Terry; D. Brunner; P. C. Stangeby; D. Elder; A. W. Leonard; J. Watkins

doi:10.1016/j.jnucmat.2013.01.088

Constraining the divertor heat width in ITER

D. G. Whyte^*, B. LaBombard, J. W. Hughes, B. Lipschultz, J. Terry, D. Brunner, P. C. Stangeby, D. Elder, A. W. Leonard, J. Watkins

^*Corresponding author for this work

Physics

Research output: Contribution to journal › Article › peer-review

Abstract

A model is developed which constrains heat width, k_r based on global power balance, momentum conservation, pedestal stability and sheath heat transmission. The model relies on measurements of the ratio of separatrix to pedestal pressure; a ratio ∼5% is found to be expected for ITER. Applying this model indicates a constraint that the allowed λ_r ∼ 10-30 mm for ITER if the divertor is in the high-recycling regime as expected (T< 20 eV) while a λ_r∼ 1-3 mm requires a separatrix pressure approximately equal to the top pedestal pressure in violation of physical reasoning and the concept of a pedestal. A weaker constraint is applied in the model that upstream separatrix temperature simultaneously satisfies power balance. The constrained model cannot satisfy power balance with λ_r < 3 mm, and in order to obtain λ_r ∼ 5 mm requires divertor plasma temperature >100 eV, a condition which would have very negative consequences for the divertor, but has never been observed experimentally.

Original language	English
Pages (from-to)	S435–S439
Journal	Journal of Nuclear Materials
Volume	438
Issue number	SUPPL
DOIs	https://doi.org/10.1016/j.jnucmat.2013.01.088
Publication status	Published - 11 Feb 2013

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title = "Constraining the divertor heat width in ITER",

abstract = "A model is developed which constrains heat width, kr based on global power balance, momentum conservation, pedestal stability and sheath heat transmission. The model relies on measurements of the ratio of separatrix to pedestal pressure; a ratio ∼5% is found to be expected for ITER. Applying this model indicates a constraint that the allowed λr ∼ 10-30 mm for ITER if the divertor is in the high-recycling regime as expected (T< 20 eV) while a λr∼ 1-3 mm requires a separatrix pressure approximately equal to the top pedestal pressure in violation of physical reasoning and the concept of a pedestal. A weaker constraint is applied in the model that upstream separatrix temperature simultaneously satisfies power balance. The constrained model cannot satisfy power balance with λr < 3 mm, and in order to obtain λr ∼ 5 mm requires divertor plasma temperature >100 eV, a condition which would have very negative consequences for the divertor, but has never been observed experimentally.",

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AU - Whyte, D. G.

AU - LaBombard, B.

AU - Hughes, J. W.

AU - Lipschultz, B.

AU - Terry, J.

AU - Brunner, D.

AU - Stangeby, P. C.

AU - Elder, D.

AU - Leonard, A. W.

AU - Watkins, J.

PY - 2013/2/11

Y1 - 2013/2/11

N2 - A model is developed which constrains heat width, kr based on global power balance, momentum conservation, pedestal stability and sheath heat transmission. The model relies on measurements of the ratio of separatrix to pedestal pressure; a ratio ∼5% is found to be expected for ITER. Applying this model indicates a constraint that the allowed λr ∼ 10-30 mm for ITER if the divertor is in the high-recycling regime as expected (T< 20 eV) while a λr∼ 1-3 mm requires a separatrix pressure approximately equal to the top pedestal pressure in violation of physical reasoning and the concept of a pedestal. A weaker constraint is applied in the model that upstream separatrix temperature simultaneously satisfies power balance. The constrained model cannot satisfy power balance with λr < 3 mm, and in order to obtain λr ∼ 5 mm requires divertor plasma temperature >100 eV, a condition which would have very negative consequences for the divertor, but has never been observed experimentally.

AB - A model is developed which constrains heat width, kr based on global power balance, momentum conservation, pedestal stability and sheath heat transmission. The model relies on measurements of the ratio of separatrix to pedestal pressure; a ratio ∼5% is found to be expected for ITER. Applying this model indicates a constraint that the allowed λr ∼ 10-30 mm for ITER if the divertor is in the high-recycling regime as expected (T< 20 eV) while a λr∼ 1-3 mm requires a separatrix pressure approximately equal to the top pedestal pressure in violation of physical reasoning and the concept of a pedestal. A weaker constraint is applied in the model that upstream separatrix temperature simultaneously satisfies power balance. The constrained model cannot satisfy power balance with λr < 3 mm, and in order to obtain λr ∼ 5 mm requires divertor plasma temperature >100 eV, a condition which would have very negative consequences for the divertor, but has never been observed experimentally.

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VL - 438

SP - S435–S439

JO - Journal of Nuclear Materials

JF - Journal of Nuclear Materials

IS - SUPPL

ER -

Constraining the divertor heat width in ITER

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