Progress of Jinping underground nuclear astrophysics experiment (JUNA)

Jinping Underground Nuclear Astrophysics Experiment (JUNA) will take the advantage of the ultra-low background in China Jinping Underground Laboratory (CJPL). A number of nuclear reactions important to hydrostatic stellar evolution near their Gamow window energy such as ²⁵Mg (p, γ) ²⁶Al, ¹⁹F (p, α) ¹⁶O, ¹³C (α, n) ¹⁶O and ¹²C (α, γ) ¹⁶O will be directly measured. At present, 400 kV high current accelerator and ECR ion source were successfully developed, and the proton and He⁺ (400 keV, 10 mA) and He²⁺ beam (800 keV, 2 mA) were successfully obtained. The development of high-power solid targets and the establishment of experimental data acquisition systems were successfully completed. Ultra-low background fast neutron detectors, 4π BGO detector arrays and large solid angle particle detector arrays were developed and assembled, and the background levels of the ground and CJPL were measured. In general, JUNA project smoothly completed the objectives set in the medium term and passed the assessment of the fund committee (Grade A) and international assessment. (authors)