Impact of nitrogen molecular breakup on divertor conditions in JET L-mode plasmas using SOLPS-ITER

IF 2.3 2区物理与天体物理 Q1 NUCLEAR SCIENCE & TECHNOLOGY

Nuclear Materials and Energy Pub Date : 2025-04-12 DOI:10.1016/j.nme.2025.101929

R. Mäenpää , H. Kumpulainen , M. Groth , N. Horsten , D. Reiter , J. Romazanov , B. Lomanowski , S. Brezinsek , J. Karhunen , K.D. Lawson , A.G. Meigs , S. Menmuir , A. Shaw , JET Contributors , EUROfusion Tokamak Exploitation Team

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引用次数: 0

Abstract

SOLPS-ITER simulations of nitrogen-seeded, low-confinement mode plasmas in the Joint European Torus (JET) predict that the electron temperature in the low-field side (LFS) divertor leg is reduced locally by up to an order of magnitude when nitrogen is assumed to recycle as molecules (N₂) instead of atoms using a fixed nitrogen injection rate. The LFS divertor temperature reduction under the assumption of molecular recycling occurs due to a three-step mechanism: (1) the plasma penetration of nitrogen atoms is increased due to the strong triple bond of the N₂ molecule and the kinetic energy release in the dissociation event, both mechanisms contributing equally, (2) the abundance of (particularly multiply-charged) nitrogen ions in the divertor is increased and (3) the electron temperature is reduced due to the increase in radiation (by up to a factor of 4) from nitrogen ions.

Setting the volume-integrated nitrogen radiated power to a constant value (0.6 MW) instead of the nitrogen injection rate, SOLPS-ITER predicts under the molecular nitrogen recycling assumption that the peak line-integrated N II, N III and N IV intensities in the LFS divertor are approximately within 15%, 35% and 5%, respectively, of the reference atomic nitrogen recycling case. The predicted peak N II, N III and N IV intensities under either assumption are within 30%, 65% and 5%, respectively, of measurements using the vertically viewing mirror-link divertor spectrometer (Meigs et al., 2010) in nitrogen-seeded JET L-mode plasmas (Lomanowski et al., 2019). ERO2.0 simulations using a constant nitrogen seeding rate on static background plasma solutions from EDGE2D-EIRENE (previously presented in Mäenpää et al., (2022), revised here to include fast reflections) predict that N II to N IV line emission is increased by 20% to 30% when nitrogen is assumed to recycle as molecules, demonstrating the importance of considering the effect of molecular dissociation reactions on the divertor plasma in a self-consistent manner.

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SOLPS-ITER 模拟了欧洲联合环（JET）中的氮封低会聚模式等离子体，预测当使用固定氮气注入速率假设氮气以分子（N2）而非原子形式循环时，低场侧（LFS）岔流腿中的电子温度会局部降低一个数量级。在分子循环假设下，LFS 分流管温度的降低是由三步机制造成的：（1）由于 N2 分子的强三键和解离过程中释放的动能，氮原子的等离子体穿透力增加，这两种机制的作用相同；（2）分流管中（尤其是多电荷）氮离子的丰度增加；（3）由于氮离子的辐射增加（最多增加 4 倍），电子温度降低。将体积积分氮辐射功率设定为一个恒定值（0.6 兆瓦）而不是氮注入率，SOLPS-ITER 预测在分子氮循环假设下，LFS 分流器中的峰值线积分 NⅡ、NⅢ和 NⅣ强度分别约为参考原子氮循环情况的 15%、35% 和 5%。在这两种假设条件下预测的 NⅡ、NⅢ和 NⅣ峰值强度，与使用垂直观察镜-连线分流器光谱仪（Meigs 等人，2010 年）在氮植被 JET L 模式等离子体中的测量值（Lomanowski 等人，2019 年）相比，分别在 30%、65% 和 5%的范围内。在 EDGE2D-EIRENE 的静态背景等离子体溶液上使用恒定氮气播种率进行的 ERO2.0 模拟（之前在 Mäenpää 等人，（2022 年）中介绍过，此处进行了修订，以包括快速反射）预测，当假定氮气以分子形式循环时，N II 到 N IV 线发射会增加 20% 到 30%，这表明了以自洽方式考虑分子解离反应对分流器等离子体的影响的重要性。

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来源期刊

Nuclear Materials and Energy Materials Science-Materials Science (miscellaneous)

CiteScore

3.70

自引率

15.40%

发文量

175

审稿时长

20 weeks

期刊介绍： The open-access journal Nuclear Materials and Energy is devoted to the growing field of research for material application in the production of nuclear energy. Nuclear Materials and Energy publishes original research articles of up to 6 pages in length.