Comparison of H-mode plasmas in JET-ILW and JET-C with and without nitrogen seeding

TY - JOUR

T1 - Comparison of H-mode plasmas in JET-ILW and JET-C with and without nitrogen seeding

AU - Jaervinen, A. E.

AU - Giroud, C.

AU - Groth, M.

AU - Belo, P.

AU - Brezinsek, S.

AU - Beurskens, M.

AU - Corrigan, G.

AU - Devaux, S.

AU - Drewelow, P.

AU - Harting, D.

AU - Huber, A.

AU - Jachmich, S.

AU - Lawson, K.

AU - Lipschultz, B.

AU - Maddison, G.

AU - Maggi, C.

AU - Marchetto, C.

AU - Marsen, S.

AU - Matthews, G. F.

AU - Meigs, A. G.

AU - Moulton, D.

AU - Sieglin, B.

AU - Stamp, M. F.

AU - Wiesen, S.

N1 - © 2016 EURATOM. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details

PY - 2016/3/16

Y1 - 2016/3/16

N2 - In high confinement mode, highly shaped plasmas with edge localized modes in JET, and for heating power of 15-17 MW, the edge fluid code EDGE2D-EIRENE predicts transition to detachment assisted by nitrogen at the low field side (LFS) target when more than 50% of the power crossing the separatrix between ELMs is radiated in the divertor chamber, i.e. ∼4 MW. This is observed both in the ITER-like wall (JET-ILW) and in the carbon wall (JET-C) configurations and is consistent with experimental observations within their uncertainty. In these conditions, peak heat fluxes below 1 MW m-2 are measured at the LFS target and predicted for both wall configurations. When the JET-C configuration is replaced with the JET-ILW, a factor of two reduction in the divertor radiated power and 25-50% increase in the peak and total power deposited to the LFS divertor plate is predicted by EDGE2D-EIRENE for unseeded plasmas similar to experimental observations. At the detachment threshold, EDGE2D-EIRENE shows that nitrogen radiates more than 80% of the total divertor radiation in JET-ILW with beryllium contributing less than a few %. With JET-C, nitrogen radiates more than 70% with carbon providing less than 20% of the total radiation. Therefore, the lower intrinsic divertor radiation with JET-ILW is compensated by stronger nitrogen radiation contribution in simulations leading to detachment at similar total divertor radiation fractions. 20-100% higher deuterium molecular fraction in the divertor recycling fluxes is predicted with light JET-C materials when compared to heavy tungsten. EDGE2D-EIRENE simulations indicate that the stronger molecular contribution can reduce the divertor peak power deposition in high recycling conditions by 10-20% due to enhanced power dissipation by molecular interaction.

AB - In high confinement mode, highly shaped plasmas with edge localized modes in JET, and for heating power of 15-17 MW, the edge fluid code EDGE2D-EIRENE predicts transition to detachment assisted by nitrogen at the low field side (LFS) target when more than 50% of the power crossing the separatrix between ELMs is radiated in the divertor chamber, i.e. ∼4 MW. This is observed both in the ITER-like wall (JET-ILW) and in the carbon wall (JET-C) configurations and is consistent with experimental observations within their uncertainty. In these conditions, peak heat fluxes below 1 MW m-2 are measured at the LFS target and predicted for both wall configurations. When the JET-C configuration is replaced with the JET-ILW, a factor of two reduction in the divertor radiated power and 25-50% increase in the peak and total power deposited to the LFS divertor plate is predicted by EDGE2D-EIRENE for unseeded plasmas similar to experimental observations. At the detachment threshold, EDGE2D-EIRENE shows that nitrogen radiates more than 80% of the total divertor radiation in JET-ILW with beryllium contributing less than a few %. With JET-C, nitrogen radiates more than 70% with carbon providing less than 20% of the total radiation. Therefore, the lower intrinsic divertor radiation with JET-ILW is compensated by stronger nitrogen radiation contribution in simulations leading to detachment at similar total divertor radiation fractions. 20-100% higher deuterium molecular fraction in the divertor recycling fluxes is predicted with light JET-C materials when compared to heavy tungsten. EDGE2D-EIRENE simulations indicate that the stronger molecular contribution can reduce the divertor peak power deposition in high recycling conditions by 10-20% due to enhanced power dissipation by molecular interaction.

KW - divertor

KW - impurity seeding

KW - ITER-like wall

KW - JET

KW - power exhaust

UR - http://www.scopus.com/inward/record.url?scp=84963983978&partnerID=8YFLogxK

U2 - 10.1088/0029-5515/56/4/046012

DO - 10.1088/0029-5515/56/4/046012

M3 - Article

AN - SCOPUS:84963983978

SN - 0029-5515

VL - 56

JO - Nuclear Fusion

JF - Nuclear Fusion

IS - 4

M1 - 046012

ER -