Characteristics of the H-mode pedestal in improved confinement scenarios in ASDEX Upgrade, DIII-D, JET and JT-60U
Characteristics of the H-mode pedestal in improved confinement scenarios in ASDEX Upgrade, DIII-D, JET and JT-60U
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DOI：
10.1088/0029-5515/47/7/005
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发表时间：
2007-07
期刊：
影响因子：
3.3
通讯作者：
C. Maggi;R. Groebner;N. Oyama;R. Sartori;L. Horton;A. Sips;W. Suttrop;A. Leonard;T. Luce;M. Wade;DIII-D Team;Y. Kamada;H. Urano;Jt U Team;Y. Andrew;C. Giroud;E. Joffrin;E. L. Luna;E. Physics
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文献类型：
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作者：
C. Maggi;R. Groebner;N. Oyama;R. Sartori;L. Horton;A. Sips;W. Suttrop;A. Leonard;T. Luce;M. Wade;DIII-D Team;Y. Kamada;H. Urano;Jt U Team;Y. Andrew;C. Giroud;E. Joffrin;E. L. Luna;E. Physics
基座和全球等离子体参数进行了比较，在传统的ELMy H模式和改进的约束放电ASDEX升级（AUG），DIII-D，JET和JT-60 U与不同的净输入功率。电子和离子基座压力进行了研究。在所有托卡马克装置中，基座顶部压力pPED随功率适度增加，与IPB 98（y，2）标度的功率依赖性大致一致。在AUG改进的H模和JT-60 U高βpol放电中观察到较高的基座压力，q95 = 6.5，高三角形度。对于所有的机器和所有的情况下，观察到的总的和基座的热存储的能量之间的鲁棒的相关性，与两者的比率在0.3和0.5之间变化。然而，基座和堆芯约束的相对重要性因不同的状态而异。在AUG中，相对于IPB 98（y，2）缩放的约束改进是由于在具有早期加热的改进的H模式中的改进的基座约束以及在具有后期加热的改进的H模式中的改进的基座和芯约束。在DIII-D混合放电中，与常规H模式相比限制因子的增加是由于等离子体芯中的限制改善。JT-60 U反向剪切H模具有很强的内部输运势垒，从而改善了堆芯性能。在所有四个托卡马克装置中，改善的边缘稳定性与总βpol的增加相关，并且H 98（y，2）随着基座βpol的增加而增加。分析的多机数据集支持的基座存储的能量的比例表达式推导出的假设下，占主导地位的损失项的基座是由热传导的边缘传输势垒区域。
Pedestal and global plasma parameters are compared in conventional ELMy H-modes and improved confinement discharges from ASDEX Upgrade (AUG), DIII-D, JET and JT-60U with varying net input power. Both electron and ion pedestal pressures are studied. The pedestal top pressure pPED increases moderately with power in all tokamaks, in broad agreement with the power dependence of the IPB98(y, 2) scaling. Higher pedestal pressures are observed in AUG improved H-modes and in JT-60U high βpol discharges at q95 ∼ 6.5 and high triangularity. For all machines and all scenarios a robust correlation between the total and the pedestal thermal stored energy is observed, with the ratio of the two varying between ∼0.3 and 0.5. However the relative importance of pedestal and core confinement varies from regime to regime. In AUG the confinement improvement with respect to the IPB98(y, 2) scaling is due to improved pedestal confinement in improved H-modes with early heating and to both improved pedestal and core confinement in improved H-modes with late heating. In DIII-D hybrid discharges the increase in confinement factor compared with conventional H-modes is due to improved confinement in the plasma core. JT-60U reversed shear H-modes have strong internal transport barriers and thus improved core performance. In all four tokamaks improved edge stability is correlated with increasing total βpol and H98(y,2) increases with pedestal βpol. The analysed multimachine data set supports a scaling expression for the pedestal stored energy derived under the assumption that the dominant loss term for the pedestal is by thermal conduction in the edge transport barrier region.