Study, design and thermal-hydraulic simulations of Vacuum Enhancement Module cooling circuit

The Source for Production of Ions of Deuterium Extracted from a Radiofrequency plasma (SPIDER) is the 100 keV full-size Ion Source prototype of the International Thermonuclear Experimental Reactor (ITER) Neutral Beam Injectors (NBI), currently in operation at Consorzio RFX in Padova, Italy. The SPIDER vacuum pumping system is designed to operate at a nominal gas pressure of 0.3 Pa inside the Beam Source (BS), and it consists of two primary pumping groups, four turbo-molecular pumps, and eight cryogenic pumps. However, during the first three years of SPIDER operations, it was found that increasing the BS pressure to 0.6 Pa was necessary to achieve nominal performance. Additionally, a specific experimental study conducted in 2019 revealed the existence of a pressure limit in the SPIDER Vacuum Vessel (VV) that must be respected to reduce the probability of Radio Frequency breakdown. These two factors have necessitated an upgrade to the current vacuum pumping system. To address the issue of limited space for installing new pumps, a Vacuum Enhancement Module (VEM) will be added to the existing SPIDER Vacuum Vessel (VV). The VEM will house up to 512 Non-Evaporable Getter (NEG) pump cartridges in 16 × 32 modules. The pumps will need to be regenerated at temperatures up to 600 °C for up to 72 h to extract the hydrogen isotopes absorbed during operation. To prevent the heating of surrounding parts, such as the SPIDER Beam Source (BS) and electrical connections, a dedicated cooling system is required to cool down the VEM components during the NEG regeneration process. This paper presents a thermal-hydraulic study, design, and analysis of the cooling system for the VEM using Computational Fluid Dynamics (CFD) analyses.