Design and commissioning of a windowless gas-target system for high-current beams at JUNA

Xuyang Wang; Fuqiang Cao; Weike Nan; Gang Lian; Wei Nan; Hongwei Huang; Yuchen Jiang; Jingyu Dong; Minghao Zhu; Yuwen Chen; Yihui Liu; Jinlong Ma; Yueran Wang; Jie Chen; Yunju Li; Shengquan Yan; Youbao Wang; Xiao Fang; Luohuan Wang; Yangping Shen; Bing Guo; Weiping Liu; JUNA collaboration

arXiv · 2609.08782

Design and commissioning of a windowless gas-target system for high-current beams at JUNA

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Abstract

Windowless gas targets avoid the beam-energy loss and straggling introduced by entrance foils and are therefore well suited for direct measurements of low-energy nuclear reactions. A windowless gas-target system designed for operation with milliampere beams has been developed for the Jinping Underground Nuclear Astrophysics facility (JUNA). The system combines three-stage differential pumping, closed-loop gas recovery and purification, a constant-temperature power-compensation calorimeter, and a position-resolved target-thickness monitor based on secondary elastic scattering. Stable operation was achieved over a target-pressure range of 1-3 mbar, with pressure fluctuations below 1% during 8 h of continuous circulation, while the accelerator-side pressure was maintained at approximately $10^{-4}$ Pa. The closed-loop gas-circulation system maintained stable target conditions, while gas-transport calculations indicated that the axial pressure nonuniformity remained within approximately 1.6% under representative operating conditions. Calorimeter measurements were consistent with the thermal calculations, supporting the sensitivity correction used for beam-power determination. Beam commissioning with $^{14}\mathrm{N}(p,\gamma)^{15}\mathrm{O}$ and $^{12}\mathrm{C}(p,\gamma)^{13}\mathrm{N}$ at the 600 kV Cockcroft-Walton accelerator of the China Institute of Atomic Energy (CIAE) demonstrated stable operation of the gas-target and $\gamma$-ray detection systems and provided information on the influences of reaction position and beam heating. These results demonstrate the operating stability and diagnostic capability of the system for future high-current, low-energy nuclear-reaction measurements at JUNA.

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Xuyang Wang, Fuqiang Cao, Weike Nan, Gang Lian, Wei Nan, Hongwei Huang, Yuchen Jiang, Jingyu Dong, Minghao Zhu, Yuwen Chen, Yihui Liu, Jinlong Ma, Yueran Wang, Jie Chen, Yunju Li, Shengquan Yan, Youbao Wang, Xiao Fang, Luohuan Wang, Yangping Shen, Bing Guo, Weiping Liu, JUNA collaboration. 2026-09-08. Design and commissioning of a windowless gas-target system for high-current beams at JUNA. https://arxiv.org/abs/2609.08782

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