Development Of The Experimental Techniques For The ¹³C??,n?¹⁶O Reaction Experiment In The Underground Laboratory

The origin of heavy elements from iron to uranium is one of the eleven great sci-ence questions connecting quarks with the cosmos.The 13C(?,n)160 reaction is a key neutron source in the slow neutron capture process(s-process).Because half of the el-ements from iron to bismuth are produced by the s-process,therefore the reaction rate of the 13C(?,n)160 reaction in the astrophysical energy region is very important.The cross section of the 13C(?,n)160 reaction in Gamow window is extremely low.It's im-possible to measure it on the ground and the experiments of direct measurement of the 13C(?,n)160 reaction can only be carried out in the energy region higher than the stellar energies.The only current way to get the cross section of the 13C(?,n)160 reaction in the astrophysical energy region is to extrapolate the cross sections measured in the higher energy region down to the stellar energies by R-matrix with a rather large uncertainty In order to obtain a more accurate reaction rate of the 13C(?,n)160 reaction,the Jinping Underground Laboratory Nuclear Astrophysics team plans to measure its reaction cross section directly in the Gamow window with a high-current accelerator in China Jinping Underground Laboratory(CJPL).This thesis includes the following parts1.Detector construction.A neutron detector consisting 24 3He tubes and a polyethy-lene moderator is developed for the direct measurement of the 13C(?,n)160 reaction in the higher energy region.The calibration experiment has been finished by a 3 MeV tandem accelerator of Sichuan university.Another fast neutron detector with 24 3He tubes and a plastic scintillator is developed to measure the cross section of 13C(?,n)160 reaction in the stellar energy region.This detector can reduce the background by the coincidence of the fast signal(produced by the scintillator)and the slow signal(produced by the 3He tubes)2.The investigation of the thermal neutron background in CJPL.In order to study the detection technology in the ultra-low neutron neutron background environment,a 3He tube has been used to measure the thermal neutron flux in the CJPL-? hall and the CJPL-? C2 hall.A improved method has been developed based on digital signal processing.The influence of a background from the wall of 3He tube can be reduced using this method.3.The study of neutron background produced by the deuterium impurity in the helium beam.A relative measurement method is proposed to measure the deuterium impurity in the helium beam.The deuterium impurity of He2+ beam from the 320 kV high voltage platform in the institute of modern physics has been measured and the influence of the neutron background produced the deuterium is discussed.Based on this result,a analyzing magnet has been installed before the terminal to control the deuterium impurity.4.Identification of the beam species produced by 2.45 GHz ECR source.The beam produced by a 2.45 GHz ECR ion source which mass-to-charge ratio is 2 is in-dentified to be H2+ rather than He2+by the 7Li(p,?)? reaction.These works build the foundation for the 13C(?,n)16O experiment to be carried out in CJPL.