An experiment for knockout reaction induced by SHe beam at 82.5 MeV/nucleon on CH2 and C targets was carried out. The 6He and 4He core fragments at forward angles and the recoiled protons at large angles were detected...An experiment for knockout reaction induced by SHe beam at 82.5 MeV/nucleon on CH2 and C targets was carried out. The 6He and 4He core fragments at forward angles and the recoiled protons at large angles were detected coincidently. From this exclusive measurement the valence nucleon knockout mechanism and the core knockout mechanism are separated, which can be applied to the exclusive spectroscopic study on the structure of exotic nuclei.展开更多
A neutron detector array was used in a breakup reaction experiment at RIKEN with an 82.5 MeV/u SHe beam impinging on the CH2 and C targets. The array was calibrated using the cosmic ray, the 7 ray from the 6He＋Pb rea...A neutron detector array was used in a breakup reaction experiment at RIKEN with an 82.5 MeV/u SHe beam impinging on the CH2 and C targets. The array was calibrated using the cosmic ray, the 7 ray from the 6He＋Pb reaction and the mono-energetic neutrons from the 7Li（p, n）TBe（g.s.＋0.43 MeV） reaction. The position resolution, timing resolution and neutron de- tection efficiency were obtained accordingly. Cross-talk rejection conditions were developed based on analysis of the data taken from the 7Li（p, n）TBe（g.s.＋0.43 MeV） test experiment, and finally a preliminary two-neutron correlation function for the SHe breakup reaction was investigated.展开更多
The β-delayed neutron and γ energy spectra taken from the decay of neutron-rich nucleus ^21N were measured by using the β - γ and β - n coincidence detection method. Thirteen new neutron groups ranging from 0.28 ...The β-delayed neutron and γ energy spectra taken from the decay of neutron-rich nucleus ^21N were measured by using the β - γ and β - n coincidence detection method. Thirteen new neutron groups ranging from 0.28 MeV to 4.98 MeV and with a total branching ratio of 88.7±4.2% were observed and presented. One γ transition with an energy of 1222 keV emitted from the excited state of ^21O and four γ transitions with energies of 1674, 2397, 2780, and 3175keV emitted from the excited states of ^20O were identified in the β decay chain of ^21N. The β decay half-life for ^21N is determined to be 82.9±1.9ms. The uncertainty of half-life is much smaller than the previous result.展开更多
Breakup reactions of the double borromean nucleus ^(8)He were measured at 82.3 MeV/u on CH2 and C targets.The coincident detection of two decaying neutrons and the high performance for neutron cross talk rejection are...Breakup reactions of the double borromean nucleus ^(8)He were measured at 82.3 MeV/u on CH2 and C targets.The coincident detection of two decaying neutrons and the high performance for neutron cross talk rejection are realized in this experiment.The relative energy spectrum for ^(8)He was reconstructed with good statistics.The spectrum exhibits a structure of two resonant peaks,one at an excitation energy of about 3.0 and the other at about 4.14 MeV,respectively.Substantially larger cross section for the first resonance is observed in comparison to the results reported previously.展开更多
A knockout reaction experiment was carried out by using the 6He beam at 82.5 MeV/nucleon impinging on CH2 and C targets. The a core fragments at forward angles were detected in coincidence with the recoiled protons at...A knockout reaction experiment was carried out by using the 6He beam at 82.5 MeV/nucleon impinging on CH2 and C targets. The a core fragments at forward angles were detected in coincidence with the recoiled protons at larger angles. From this exclusive measure- ment the valence nucleon knockout mechanism and the core knockout mechanism are separated. This study provides a basis for the exclusive spectroscopic investigation of the exotic nuclei.展开更多
Differential cross sections for the elastic scattering of halo nucleus 6He on proton target were measured at 82.3 MeV/u. The experimental results axe well reproduced by optical model calculations using global potentia...Differential cross sections for the elastic scattering of halo nucleus 6He on proton target were measured at 82.3 MeV/u. The experimental results axe well reproduced by optical model calculations using global potential KD02 with a reduction of the depth of real volume part by a factor of 0.7. A systematic analysis shows that this behavior might be related to the weakly bound property of unstable nuclei.展开更多
Differential cross sections for the quasi-elastic scattering of^16 C at 47.5 MeV/nucleon from ^12 C target are measured.Coupled-channels calculations are carried out and the optical potential parameters are obtained b...Differential cross sections for the quasi-elastic scattering of^16 C at 47.5 MeV/nucleon from ^12 C target are measured.Coupled-channels calculations are carried out and the optical potential parameters are obtained by fitting the experimental angular distribution.展开更多
To perform a kinematically complete measurement of the dissociation reaction for neutron-rich nuclei, a multi-neutron correlation spectrometer is proposed at Peking University. A Monte Carlo simulation code based on G...To perform a kinematically complete measurement of the dissociation reaction for neutron-rich nuclei, a multi-neutron correlation spectrometer is proposed at Peking University. A Monte Carlo simulation code based on GEANT4 is developed for a single scintillation bar which processes not only the energy deposition but also the light propagation in the scintillator and the light collection and conversion to signal at the end of the bar in a realistic way. The simulating method is described in detail in this paper, and the timing and position resolutions and detector efficiency are studied based on the simulation and compared with the experimental results. A new method of crosstalk rejection has been demonstrated to be important for the design of the whole spectrometer.展开更多
The Halo and cluster structure at the ground state of unstable nuclei are among the most exciting phenomena of current nuclear physics. Probing these structures requires a careful selection of reaction tools. In the p...The Halo and cluster structure at the ground state of unstable nuclei are among the most exciting phenomena of current nuclear physics. Probing these structures requires a careful selection of reaction tools. In the past twenty years, knockout reactions have been used intensively to investigate spectroscopically the structure of unstable nuclei. In this report we have illustrated the latest development of the knockout reaction tool and have emphasized the recoiled proton tagging method. A quantitative criteria is developed to evaluate the quasi-free feature of the knockout process. The newly discovered ＂towing mode＂ reaction tool is also outlined and its applicability at transit energies is discussed.展开更多
A knockout reaction induced by ^6He at 61.2 MeV/u was carried out at the HIRFL-RIBLL ra- dioactive beam line. The α core fragments at forward angles were detected in coincidence with the recoiled protons at large ang...A knockout reaction induced by ^6He at 61.2 MeV/u was carried out at the HIRFL-RIBLL ra- dioactive beam line. The α core fragments at forward angles were detected in coincidence with the recoiled protons at large angles. From this coincident measurement the valence nucleon knockout mechanism and the core knockout mechanism can be separated according to the polar angle correlation between the core fragments and the recoiled protons. It is demonstrated that, when reconstructing the resonant state of a weakly bound nucleus, the contamination resulting from the core knockout mechanism should be eliminated in order to obtain the correct structure information.展开更多
Four high-purity germanium 4-fold segmented Clover detectors have been applied in the experiment of neutron-rich nucleus 21N. The performance of those four Clovers have been tested with radioactive sources and in-beam...Four high-purity germanium 4-fold segmented Clover detectors have been applied in the experiment of neutron-rich nucleus 21N. The performance of those four Clovers have been tested with radioactive sources and in-beam experiments, and the main results including energy resolution, peak-to-total ratios, the variation of the hit pattern distribution in different crystals of one Clover detector with the energy of γ ray, and absolute full energy peak detection effciency curve, were presented.展开更多
基金supported by the National Basic Research Program of China (No. 2007CB815002)National Natural Science Foundation of China(Nos. 11035001, 10775003, 10827505, 10821140159)
文摘An experiment for knockout reaction induced by SHe beam at 82.5 MeV/nucleon on CH2 and C targets was carried out. The 6He and 4He core fragments at forward angles and the recoiled protons at large angles were detected coincidently. From this exclusive measurement the valence nucleon knockout mechanism and the core knockout mechanism are separated, which can be applied to the exclusive spectroscopic study on the structure of exotic nuclei.
基金supported by the National Basic Research Program of China (No. 2007CB815002)National Natural Science Foundation of China(Nos. 11035001, 10775003, 10827505, 10821140159)
文摘A neutron detector array was used in a breakup reaction experiment at RIKEN with an 82.5 MeV/u SHe beam impinging on the CH2 and C targets. The array was calibrated using the cosmic ray, the 7 ray from the 6He＋Pb reaction and the mono-energetic neutrons from the 7Li（p, n）TBe（g.s.＋0.43 MeV） reaction. The position resolution, timing resolution and neutron de- tection efficiency were obtained accordingly. Cross-talk rejection conditions were developed based on analysis of the data taken from the 7Li（p, n）TBe（g.s.＋0.43 MeV） test experiment, and finally a preliminary two-neutron correlation function for the SHe breakup reaction was investigated.
基金Supported by the National Basic Research Programme of China under Grant Nos 2007CB815000 and 2005CB724800, the National Natural Science Foundation of China under Grant Nos 10775003,10475004, 10405001, 10221003 and J0730316.
文摘The β-delayed neutron and γ energy spectra taken from the decay of neutron-rich nucleus ^21N were measured by using the β - γ and β - n coincidence detection method. Thirteen new neutron groups ranging from 0.28 MeV to 4.98 MeV and with a total branching ratio of 88.7±4.2% were observed and presented. One γ transition with an energy of 1222 keV emitted from the excited state of ^21O and four γ transitions with energies of 1674, 2397, 2780, and 3175keV emitted from the excited states of ^20O were identified in the β decay chain of ^21N. The β decay half-life for ^21N is determined to be 82.9±1.9ms. The uncertainty of half-life is much smaller than the previous result.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11035001,10975006 and J1103206the National Basic Research Program of China under Grant No 2007CB815002.
文摘Breakup reactions of the double borromean nucleus ^(8)He were measured at 82.3 MeV/u on CH2 and C targets.The coincident detection of two decaying neutrons and the high performance for neutron cross talk rejection are realized in this experiment.The relative energy spectrum for ^(8)He was reconstructed with good statistics.The spectrum exhibits a structure of two resonant peaks,one at an excitation energy of about 3.0 and the other at about 4.14 MeV,respectively.Substantially larger cross section for the first resonance is observed in comparison to the results reported previously.
基金supported by the National Basic Research Program of China (No. 2007CB815002)National Natural Science Foundation of China(Nos. 11035001, 10775003, 10827505, 10821140159)
文摘A knockout reaction experiment was carried out by using the 6He beam at 82.5 MeV/nucleon impinging on CH2 and C targets. The a core fragments at forward angles were detected in coincidence with the recoiled protons at larger angles. From this exclusive measure- ment the valence nucleon knockout mechanism and the core knockout mechanism are separated. This study provides a basis for the exclusive spectroscopic investigation of the exotic nuclei.
基金Supported by the National Basic Research Program of China （2007CB815002）, and the National Natural Science Foundation of China （10775003, 10905002 and 10827505）.
文摘Differential cross sections for the elastic scattering of halo nucleus 6He on proton target were measured at 82.3 MeV/u. The experimental results axe well reproduced by optical model calculations using global potential KD02 with a reduction of the depth of real volume part by a factor of 0.7. A systematic analysis shows that this behavior might be related to the weakly bound property of unstable nuclei.
基金Supported by the National Basic Research Program of China under Grant No 2007CB815002, the National Natural Science Foundation of China under Grant Nos 10405002, 10775003 and 10720003, the Found for Fostering Talents of Basic Science （NFFTBS） （J073316）.
文摘Differential cross sections for the quasi-elastic scattering of^16 C at 47.5 MeV/nucleon from ^12 C target are measured.Coupled-channels calculations are carried out and the optical potential parameters are obtained by fitting the experimental angular distribution.
基金Supported by National Basic Research Program (973 Program) of China (2007CB815002)National Natural Science Founda-tion of China (10827505, 10775003, 10475004, 10405001, J0730316)
文摘To perform a kinematically complete measurement of the dissociation reaction for neutron-rich nuclei, a multi-neutron correlation spectrometer is proposed at Peking University. A Monte Carlo simulation code based on GEANT4 is developed for a single scintillation bar which processes not only the energy deposition but also the light propagation in the scintillator and the light collection and conversion to signal at the end of the bar in a realistic way. The simulating method is described in detail in this paper, and the timing and position resolutions and detector efficiency are studied based on the simulation and compared with the experimental results. A new method of crosstalk rejection has been demonstrated to be important for the design of the whole spectrometer.
基金Supported by National Basic Research Program (973 Program) of China (2007CB815002)National Natural Science Foundation of China (11035001, 10775003, 10827505, J0730316)
文摘The Halo and cluster structure at the ground state of unstable nuclei are among the most exciting phenomena of current nuclear physics. Probing these structures requires a careful selection of reaction tools. In the past twenty years, knockout reactions have been used intensively to investigate spectroscopically the structure of unstable nuclei. In this report we have illustrated the latest development of the knockout reaction tool and have emphasized the recoiled proton tagging method. A quantitative criteria is developed to evaluate the quasi-free feature of the knockout process. The newly discovered ＂towing mode＂ reaction tool is also outlined and its applicability at transit energies is discussed.
基金Supported by National Basic Research Program (973 Program) of China (2007CB815002)National Natural ScienceFoundation of China (11035001,10775003,10827505,J0730316)
文摘A knockout reaction induced by ^6He at 61.2 MeV/u was carried out at the HIRFL-RIBLL ra- dioactive beam line. The α core fragments at forward angles were detected in coincidence with the recoiled protons at large angles. From this coincident measurement the valence nucleon knockout mechanism and the core knockout mechanism can be separated according to the polar angle correlation between the core fragments and the recoiled protons. It is demonstrated that, when reconstructing the resonant state of a weakly bound nucleus, the contamination resulting from the core knockout mechanism should be eliminated in order to obtain the correct structure information.
基金Supported by National Basic Research Program (973 program) of China (2007CB815000, 2005CB724800) National Natural Science Foundation of China (10775003,10475004, 10405001, 10221003, J0730316)
文摘Four high-purity germanium 4-fold segmented Clover detectors have been applied in the experiment of neutron-rich nucleus 21N. The performance of those four Clovers have been tested with radioactive sources and in-beam experiments, and the main results including energy resolution, peak-to-total ratios, the variation of the hit pattern distribution in different crystals of one Clover detector with the energy of γ ray, and absolute full energy peak detection effciency curve, were presented.
