This paper compares the gyrokinetic instabilities and transport in two representative JET pedestals, one (pulse 78697) from the JET configuration with a carbon wall (C) and another (pulse 92432) from after the installation of JET's ITER-like Wall (ILW). The discharges were selected for a comparison of JET-ILW and JET-C discharges with good confinement at high current (3 MA, corresponding also to low ) and retain the distinguishing features of JET-C and JET-ILW, notably, decreased pedestal top temperature for JET-ILW. A comparison of the profiles and heating power reveals a stark qualitative difference between the discharges: the JET-ILW pulse (92432) requires twice the heating power, at a gas rate of e s−1, to sustain roughly half the temperature gradient of the JET-C pulse (78697), operated at zero gas rate. This points to heat transport as a central component of the dynamics limiting the JET-ILW pedestal and reinforces the following emerging JET-ILW pedestal transport paradigm, which is proposed for further examination by both theory and experiment. ILW conditions modify the density pedestal in ways that decrease the normalized pedestal density gradient a/Ln, often via an outward shift in relation to the temperature pedestal. This is attributable to some combination of direct metal wall effects and the need for increased fueling to mitigate tungsten contamination. The modification to the density profile increases , thereby producing more robust ion temperature gradient (ITG) and electron temperature gradient driven instability. The decreased pedestal gradients for JET-ILW (92432) also result in a strongly reduced shear rate, further enhancing the ion scale turbulence. Collectively, these effects limit the pedestal temperature and demand more heating power to achieve good pedestal performance. Our simulations, consistent with basic theoretical arguments, find higher ITG turbulence, stronger stiffness, and higher pedestal transport in the ILW plasma at lower .
本论文比较了JET两个代表性台基中的回旋动理学不稳定性和输运，一个（脉冲78697）来自具有碳壁（C）的JET构型，另一个（脉冲92432）来自安装JET类ITER壁（ILW）之后。选择这些放电是为了比较JET-ILW和JET-C在高等离子体电流（3 MA，也对应于低）下的良好约束，并保留JET-C和JET-ILW的显著特征，特别是JET-ILW的台基顶部温度降低。对剖面和加热功率的比较揭示了两次放电之间的显著定性差异：JET-ILW脉冲（92432）需要两倍的加热功率，在气体注入率为 e s⁻¹ 时，才能维持JET-C脉冲（78697）在零气体注入率下所维持的台基温度梯度的大约一半。这表明热输运是限制JET-ILW台基动力学的一个核心组成部分，并强化了以下新兴的JET-ILW台基输运范式，该范式有待理论和实验进一步检验。ILW条件改变了密度台基，使得归一化密度台基梯度 a/Lₙ 降低，通常通过密度台基相对于温度台基向外移动来实现。这可归因于直接金属壁效应与为缓解钨污染而增加燃料注入需求的某种组合。密度剖面的这种修改增加了 ，从而产生更强的离子温度梯度（ITG）和电子温度梯度驱动的不稳定性。JET-ILW（92432）中台基梯度的降低还导致 剪切显著减小，进一步增强了离子尺度湍流。综合来看，这些效应限制了台基温度，并要求更高的加热功率以实现良好的台基性能。我们的模拟与基本理论论证一致，发现在较低的 下，ILW等离子体具有更高的ITG湍流、更强的刚性和更高的台基输运。