Plasma Physics (physics.plasm-ph)

Abstract: ITER-like tungsten Langmuir probes (W DLPs) have been installed and tested at the lower divertor horizontal target composed of flat-type components in EAST. Due to the non-active cooling, transient thermal and stress\strain analyses considering actual thermal loading and cooling conditions were thus conducted to evaluate the thermal performance and mechanical quality of W DLPs subjected to the long pulse & high plasma flux of EAST. The thermal analysis reveals that the inevitable leading edge induced thermal loading at surrounding area of W DLPs is not ignorable. The thermal performance of W DLPs are largely related to the plasma scenario (Qp: parallel heat flux along magnetic field line, {\alpha}: incline angle of magnetic field line). Under current plasma parameters, melting of W was not occurred in general, but recrystallization as well as the induced cracks may be still possible. And, the interval period (~1000 s) between neighboring shots is sufficient for nature cooling of W DLPs. The stress analysis also tells that the ceramic LLL may be general a crucial weak point of W DLPs, which is expected to not only limit the thermal affordability of long pulse but also cause possible crack problems. Such calculation results can provide important reference for current plasma operation and future improvement of the W DLPs.

Abstract: Plasma ignition is critical in various scientific and industrial applications, demanding an efficient and robust execution mechanism. In this work, we present an innovative approach to plasma ignition by incorporating the analysis of fundamental aspects of light scattering in the complex frequency plane. For the first time, we demonstrate the high-power virtual perfect absorption (VPA) regime, a groundbreaking method for perfectly capturing light within a resonator. By carefully designing the temporal profile of the incident wave, we effectively minimize reflections during the ignition stages, thereby significantly enhancing the efficiency and resilience of the process. Through comprehensive experimental investigations, we validate the viability of this approach, establishing VPA as a powerful tool for reflectionless excitation and optimal control of plasma discharge. By addressing the limitations of conventional plasma ignition methods, this research represents a pivotal step towards transformative advancements in plasma technology, with promising implications for improving the performance and sustainability of numerous applications.