Substantial power dissipation in the edge plasma is required for the safe operation of ITER and next-step fusion reactors, otherwise unmitigated heat fluxes at the divertor plasma-facing components (PFCs) would easily exceed their material limits. Traditionally, such heat flux mitigation is linked to the regime of detachment, which is characterised by a significant pressure gradient between upstream and downstream scrape-off layer (SOL). However, the physics phenomena responsible for power dissipation and pressure loss are distinctly different, especially when the power dissipation is achieved by impurity seeding. In principle, it is possible to achieve substantial mitigation of the heat fluxes while maintaining conservation of the pressure along the open field lines in the SOL. This regime can be accessed by injection of medium- or high-Z impurities, which mostly radiate inside the last closed flux surface. The critical question related to such an approach is the effect on confinement and perspective fusion power generation in future thermonuclear reactors. In this work, we report on experiments at COMPASS tokamak, where neon and argon impurities were injected in ohmic or NBI-heated low confinement plasmas. With appropriate seeding waveform, stable scenarios were achieved, avoiding the radiative collapse of plasmas. Significant reduction of heat fluxes at the outer target was observed, with heat flux pattern similar to the one previously achieved by nitrogen seeding. The reduction of downstream pressure was, however, accompanied by an equal reduction of upstream pressure, indicating that the power dissipation occurred inside the separatrix. Indeed, the impurity cooling is causing a significant drop of edge temperature; however, the effect in the plasma centre is much less pronounced.

为了安全地运行ITER和下一步聚变反应堆，需要在边缘等离子体中进行大量功耗，否则在偏滤器面向等离子体的部件（PFC）处未缓解的热通量很容易超过其材料极限。传统上，这种热通量的减少与分离状态有关，其特征是上游和下游刮除层（SOL）之间存在明显的压力梯度。但是，造成功耗和压力损失的物理现象截然不同，尤其是在通过杂质注入实现功耗的情况下。原则上，可以在保持SOL中沿开放电场线的压力保持不变的同时，实现热通量的显着缓解。可以通过注入中高ž杂质，主要在最后一个封闭的通量表面内辐射。与这种方法有关的关键问题是对未来热核反应堆中密闭和透视聚变发电的影响。在这项工作中，我们报告了COMPASS Tokamak的实验，该实验将氖气和氩气杂质注入欧姆或NBI加热的低限制等离子体中。通过适当的播种波形，可以获得稳定的场景，避免了等离子体的辐射塌陷。观察到外靶的热通量显着降低，其热通量模式与先前通过氮注入获得的热通量模式相似。然而，下游压力的降低伴随着上游压力的相等降低，这表明功率消耗发生在分离线内部。的确，杂质冷却导致边缘温度显着下降；但是，在等离子体中心的影响要小得多。