Design and Recent Progress of High Intensity Accelerator for Jinping Underground Nuclear Astrophysics Experiment (JUNA)

Direct measurement of the cross sections for the key nuclear reactions is crucial for obtaining benchmark data for stellar model, verifying extrapolation model, constraining theoretical calculations, and solving key scientific questions in nuclear astrophysics. However, cross sections of the astrophysical reactions are extremely small. Tiny reaction rates in laboratories at the earth surface are hampered by the cosmic-ray background. With the ultra-low background, underground lab becomes a promising solution of experimental nuclear astrophysics. China Jinping Underground Laboratory (CJPL) is currently deepest underground site in the world. For such experiments, a 400 kV and 10 mA accelerator specially designed for Jinping Underground Nuclear Astrophysics Experiment (JUNA) will be placed in CJPL. In this paper, JUNA high intensity accelerator was introduced. Its layout, design considerations, beam optics and recent progress in ground laboratory were presented.