This work discusses the possible mechanisms that have led to the degradation of the pedestal pressure height and pedestal stability of low triangularity peeling-ballooning (PB) limited pla-smas from JET with the carbon wall (JET-C) to JET with the ITER-like wall (JET-ILW). The work shows that the lower pedestal stability of JET-ILW is not directly caused by the presence of a metal wall, but rather due to the operational constraints that require operation with high gas fuelling. Recent results have suggested the possible role of the distance between the density and temperature pedestal positions (n _e ^pos − T _e ^pos, also called the ‘relative shift’) with increasing gas fuelling rate on the PB stability of JET-ILW baseline plasmas (Stefanikova etal 2018 Nucl. Fusion 58 056010). The work further extends the analysis of the role of the relative shift, showing that it plays an important role in the difference between the pedestal performance of JET-C and JET-ILW. Moreover, the work also shows that the pedestal density n _e ^ped, Z _eff, and pedestal pressure width w _pe play an important role in this difference. The pedestal structure and stability have been studied both experimentally and by modelling. The modelling shows that the changes in n _e ^pos − T _e ^pos, n _e ^ped, Z _eff, and w _pe are sufficient to explain the differences in the pedestal performance between JET-C and JET-ILW PB limited discharges. A hypothesis describing the possible mechanisms leading to the degradation of the pedestal pressure and stability from JET-C to JET-ILW in PB limited plasmas is put forward.

这项工作讨论了导致低三角形剥离-气球膨胀（PB）有限等离子体从JET和碳壁（JET-C）到ITER-JET的基座压力高度降低和基座稳定性的可能机制。像墙（JET-ILW）。这项工作表明，JET-ILW的较低的基座稳定性不是直接由于金属壁的存在而引起的，而是由于操作上的限制要求在高气体燃料下运行。最近的结果表明，密度和温度基座位置之间的距离（n _e ^pos - T _e ^pos也被称为“相对移动”）上的PB稳定性增加气体燃料供应率JET-ILW基线等离子体（Stefanikova等人2018核酸研究，聚变 58 056010）。这项工作进一步扩展了相对位移的作用分析，表明它在JET-C和JET-ILW的基座性能之间的差异中起着重要作用。此外，工作也表明了底座密度ñ _é ^PED，ž _EFF和底座压力宽度w ^ _PE发挥这种差异具有重要作用。通过实验和建模研究了基座的结构和稳定性。建模表明，n的变化 _e ^pos - T _e ^pos，n _e ^ped，Z _eff和w _pe足以解释JET-C和JET-ILW PB极限放电之间的基座性能差异。提出了一个假设，该假设描述了在铅受限的血浆中导致基座压力下降和从JET-C到JET-ILW稳定性的可能机制的假设。