CNO循环关键反应15N(p,g)16O的间接测量

15N(p,g)16O is one of the key reactions in the CNO cycle. Its astrophysical reaction rates directly affect the abundance of the 16O, 17O and 18O nuclei. So far, several direct measurements have only reached down to about 100 keV which is much higher than the stellar energies. The 15N(p,g)16O astrophysical S factors can be derived based on the proton spectroscopic factor of 16O, deduced from the angular distribution of proton transfer reactions. Several experiments have been performed to study the proton spectroscopic factor of 16O, however, their results clearly deviate from each other. In order to clarify the discrepancy, new measurement is highly needed. We plan to measure the precise angular distribution of 15N(7Li,6He)16O transfer reaction with the Q3D magnetic spectrometer of the HI-13 tandem accelerator, and then derive the proton spectroscopic factor of 16O and the reliable astrophysical S factors and reaction rates.

15N(p,g)16O反应是CNO循环中的关键反应，决定16O、17O和18O等重要核素的产生。迄今该反应直接测量达到的最低能量为100 keV左右，还远高于恒星能量(约23.4 keV)，而且直接测量结果之间也存在一定的差异。因此可以通过测量转移反应导出16O的质子谱因子，进而间接确定15N(p,g)16O天体物理反应率。目前国际上16O质子谱因子的研究结果存在相当大的差别，很有必要采用一个全新的实验方案来澄清该分歧。我们计划在串列加速器Q3D磁谱仪上精确测量15N(7Li,6He)16O反应角分布并用来提取16O的质子谱因子，进而导出更可靠的恒星能量下15N(p,g)16O天体物理S因子和反应率。本实验的束流申请已获得串列加速器束流评审委员会的批准。

15N(p,g)16O反应是CNO循环中的关键反应，直接测量达到的最低能量远高于恒星能量，而且直接测量结果之间也存在一定的差异。因此可以通过测量转移反应导出16O 的质子谱因子，进而间接确定15N(p,g)16O 天体物理反应率。目前国际上16O 质子谱因子的研究结果存在相当大的差别，很有必要采用一个全新的实验方案来澄清该分歧。我们在串列加速器Q3D 磁谱仪上精确测量了15N(7Li,6He)16O 反应角分布并提取16O 的质子谱因子，澄清了国际上的分歧，利用得到的谱因子导出了15N(p,g)16O 天体物理S 因子。