First results of non-evaporable getter pump studies for the application in the EAST tokamak

Abstract

Enhanced particle exhaust is pivotal in optimizing fuel recycling and bolstering plasma performance within fusion reactors. Non-Evaporable Getter (NEG) pumps, renowned for their robust high-temperature tolerance, high pumping speeds and large adsorption capabilities, emerge as highly promising candidates for augmenting the particle exhaust efficiency of tokamaks. Rigorous evaluations have been undertaken to ascertain their pumping efficacy within a vacuum testing setup and the EAST tokamak environment. Experimental data have consistently demonstrated that NEG pumps maintain stable operation across a broad temperature range, from ambient conditions to 200 °C, with a notable direct correlation observed between the pumping speed and the ambient temperature. Their performance surpasses that of conventional cryopumps, especially at D2 gas pressures exceeding 0.1 Pa. Additionally, the application of nitrogen passivation has been validated as an effective method to modulate the pumping speed and to mitigate the risk of hydrogen embrittlement and oxygen and carbon contaminations. Despite exposure to the extreme operational demands, including 30 h of plasma exposure, and lithium processing, atmospheric conditions, and water leaks, the NEG pumps preserved approximately 70 % of their initial pumping capacity. These results underscore the compatibility of NEG pumps with the challenging environments of plasma operations, positioning them as a viable and promising solution for particle exhaust in the next-generation fusion reactors.