Studies On ?-delayed?Two?Proton Emission From²²Al And²¹Mg

The first particle accelerator used in nuclear physics was invented in 1930s.Since then,nuclear physics developed rapidly and nuclear scientists have identified more than 2700 unstable isotopes until now due to the further development of accelerators and techniques in nuclear physics.The studies on these unstable isotopes can widely broaden and deepen our knowledge of nucleus.For the studies on those isotopes with extremely unbalanced numbers on neutrons and protons,scientists found some new phe-nomena such as halo or skin structures,rare decay modes and new magic numbers.To understand these new physics,it is necessary to improve theoretical models on nuclear structure and nuclear force,and it is can help us to better understand the substance and the interactions in our universe.The first confirmed ?-delayed proton emission isotope is 25Si in 1960s,and scien-tists have identified more than 160 ?-delayed proton decay precursors till now.The experimental data of ?-delayed proton decay have rich spectroscopic information on nuclear energy levels,spin,parity,level width and level density.Direct or ?-delayed two proton emission is a rare decay mode in some isotopes near the proton drip line.There are three decay mechanisms to describe this rare decay as follows:(A),sequen-tial emission,the two protons emitted from the mother nucleus sequentially,and there are no correlations between the two protons.(B),three-body simultaneous uncorrelated emission,the two protons emitted from the mother nucleus simultaneously,and there are no correlations between the two protons.(C),2He cluster emission,due to pair-ing interaction,the two protons could undergo a simultaneous emission with a strong correlation.More experimental data is needed to invest direct or ?-delayed two-proton emission from the proton rich isotopes.22Al(Z=13,N=9)is an isotope located near the proton drip line,and it was firstly studied experimentally in Lawrence Berkeley Laboratory by M.D.Cable et al.in 1982.22 Al was produced by the reaction 24Mg(3He,p4n)and then 22 Al was transported by a helium-jet system to a detection chamber.The beta-delayed protons from 22 Al were de-tected by silicon detectors.After that,Blank.B et al.in 1997 and L.Achouri et al.in 2006 performed another experiments on the decay of 22Al at GANIL with LISE3 spec-trometer.Projectile Fragmentation(PF)method was used to produce 22A1 with 36Ar primary beam impinged on a nickel and carbon target respectively.Silicon detectors and gas detectors was used to detect the decay of 22Al in their experiments.High-purity germanium(HPGe)detector was used to detect ?-rays in the experiment by Achouri et al.in 2006,which provided us more information about the decay of 22Al.Never-theless,the three mentioned experiments did not performed to invest the ?-delayed two proton decay of 22Al,and they can't give any information of the correlations between the two ?-delayed protons.21Mg(Z=12,N=9)is another proton rich unstable isotope.In 1973,R.G.Sextro et al.performed the first experiment to invest the ?-delayed proton decay of 21Mg at Lawrence Berkeley Laboratory.In that experiment 21Mg was produced by the reac-tion 20Ne(3He,p2n).Helium jet system was used to transport 21Mg to the detection chamber where silicon detectors was set to detect the ?-delayed protons from 21Mg.Half-life time of 21Mg and the energy spectrum of ?-delayed protons from 21Mg was obtained in their experiment.In 2015,M.V Lund et al.performed another experi-ment at the ISOLDE facility at CERN.The exotic 21Mg ions were produced by using a SiC target bombarded with proton beams,and then 21Mg ions were implanted into a detection chamber composed by silicon detectors and gas detector.In addition to ?-delayed proton decay of 21Mg,?-delayed ? and ?-delayed p? emission was identified in their experiment.However,the two mentioned experiments did not detect y-rays emitted during the decay of 21Mg,and no ?-proton coincidences information obtained from those experiments.In this dissertation,we will introduce an experiment for the study of ?-delayed(two)proton emission from 22Al and 21Mg performed at Radioactive Ion Beam Line in Lanzhou(RIBLL1)at the National Laboratory of Heavy Ion Research Facilities in Lanzhou(HIRFL),China.The 22Al and 21Mg ions were produced by using a Beryl-lium target bombarded with 76 MeV/nucleon 28Si.A new silicon detector array was designed to serve as the implantation detector and the ?-delayed charged particles de-tector.In addition,five High-purity germanium(HPGe)clover detectors were used to detect the y-rays radiated during the decay.We obtained the energy spectrums of ?-delayed charged particles from 22Al and 21Mg.The half-life values for 22Al and 21Mg were measured to be 90.8±1.3 ms and 121.9±0.6 ms respectively.The energy spec-trums of protons correlated with y-rays of 22A1 and 21Mg were also obtained in our experiment.Besides that,we also measured the relative angel and the relative momen-tum distributions between the two ?-delayed protons from 22Al.The result shows that there are 29(13)%2He emission existed in the ?-delayed two proton decay from 22Al.