通过中子非弹性散射研究12C的Hoyle态及其附近激发态的α团簇性质

研究12C的Hoyle态及其附近激发态的α团簇性质，对恒星核合成、核结构、核力及有机生命起源等方面都有着重要意义。不同理论模型和实验研究对12C核内3α团簇能级分布及几何构型仍存有较大争议。非弹性散射是研究轻核激发态内核子集团结构的重要实验手段和方法。本项目计划利用中国原子能科学研究院400kV高压倍加器D-T中子源实验装置提供的14.8MeV中子轰击12C靶，通过非弹性散射过程使12C布居到不同的激发态。利用4块5×5cm2面积的正反面均16条的双面硅微条探测器测量末态α粒子的能量和位置，通过挑选3α关联事件，重建12C不变质量谱，确认激发能级。对特定的12C激发态，如Hoyle态，利用相对动量相关的超球面公式分析3α的超角分布，研究3α团簇结构的几何构型。这将有助于进一步理解12C核内可能存在的几何构型及物理机制，并为相关理论计算、中子核数据评价提供可靠的实验依据。

Study of the α clustering properties of Hoyle state and around its excited states in 12C is important for nucleosynthesis in stars, nuclear structure, nuclear force, and the origins of organic life, etc. There is still great controversy in both theoretical models and experimental studies for energy level distributions and geometrical configurations of 3α clustering structure in 12C. Inelastic scattering has been a powerful experimental tool and method for studying nucleon cluster structure in excited states of light nuclei. In this proposal, different excited states of 12C are populated by inelastic scattering process using 14.8MeV neutrons, which are produced by D-T neutron source of 400kV Cockroft-Walton accelerator in China Institute of Atomic Energy, bombarding on 12C target. The energy and position of the final state α particles are detected by four silicon strip detectors, which have surfaces of 5×5cm2 subdivided into 16 strips at both front and back side. The invariant mass spectra are reconstructed and energy levels are determined by selecting 3α correlation events. Geometrical configurations of 3α clustering structure in given excited states of 12C, e.g. Hoyle states, are investigated by analyzing 3α hyperangle distributions using relative momentum related hyperspherical formalism. It’s helpful for further understanding of possible geometrical configurations in 12C nuclei and its physical mechanism. It can also provide reliable experimental evidence for relevance theoretical calculations and neutron nuclear data evaluations.