2024 – Impurity and helium exhaust, and XPR control in high poloidal beta plasma with core-edge integration in ITER-similar shape

Impurity and helium exhaust, and XPR control in high poloidal beta plasma with core-edge integration in ITER-similar shape

2024 Research Campaign, Integrated High beta-p Scenarios

Purpose of Experiment

Purpose of Experiment: The goal of this experiment is to investigate the impurity and helium exhaust ability in high-𝛽p scenario, also integrate the X-point radiator (XPR) and compact radiative divertor (CRD) with impurity seeding. This experiment will be helpful to address two goals of the high-𝛽p scenario task force: 1) Increase core-edge integrated scenario performance in ITER-similar shape; 2) Understand high and low-Z impurity transport in plasmas with strong ITBs.

Background: The compatibility of full divertor detachment, small/no ELM and high plasma performance is an attractive path for the SSO of ITER. The high-𝛽p scenario developed on DIII-D in recent years is proved to have a good compatibility with divertor detachment, ELM suppression and high core plasma performance with a strong ITB, which is foreseen as a promising core-edge plasma solution for future fusion reactors. The edge heat flux control is achieved by strong neon seeding, which leads to high fraction of power inside the separatrix and thus forming XPR. In this experiment the XPR will be controlled to move the X-point to closer divertor target to achieve CRD, which would allow a reduced divertor size, an economically beneficial larger volume of the confined plasma. In addition, due to strong neon seeding, the neon concentration is serious and the line-averaged Zeff even reaches 6, which leads to very high core radiation power and limits the core performance. Therefore, it is necessary to exhaust the impurity to further improve the plasma performance Moreover, Helium (He) is an unavoidable impurity component in the burning plasma of future reactors, but too much He in the plasma can lead to dilution of D-T fuel and thus degrade the core plasma performance. The He exhaust experiment on multiple devices suggest that He exhaust is strongly affected by the existence of ITB and divertor neutral pressure. Therefore, it is also a good chance to study the He exhaust ability in high-𝛽p scenario with ITB and different divertor conditions

Experimental Approach

 In this experiment, after establishing the high-𝛽p plasma with a large radius ITB, neon injection rate will be scanned to get different dissipative divertor conditions, especially full detachment. The He will be also injected, the OSP scan will be performed to evaluate the He exhaust with different configurations and neutral pressure. Optimized ECH power will be injected to help neon exhaust. In addition, after XPR formation with neon injection, it is proposed to step by step move the X-point to shorten the leg to produce the CRD regime.

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