β-delayed neutron decay of 21N

The β-delayed neutron and γ spectra of neutron-rich nucleus ²¹N using β-γ and β-n coincidence measurements were presented in this paper. Thirteen new neutron groups ranging from 0.28 MeV to 4.98 MeV and with a total branching ratio 88.7±4.2% were observed. One γ transition among the excited states of ²¹O, and four γ transitions among the excited states of ²⁰O were identified in the β decay chain of ²¹N. The ungated half-life of 83.8±2.1 ms was also determined for ²¹N.     

β缓发中子探测阵列的性能优化及测试

讲述了用于β缓发中子发射测量的中子探测阵列的性能优化过程及测试结果. 对中子探测器包装用的几种反射材料、光导和光电倍增管之间用的几种耦合材料行了系统的对比和研究. 为了优化电子学和实时监测整个探测阵列的工作状态, 引入了LED光纤刻度监测系统.     

Structure change of 156Yb at high-spin states

High-spin states of ¹⁵⁶Yb have been studied via the ¹⁴⁴Sm(¹⁶O,4n)¹⁵⁶Yb fusion-evaporation reaction at beam energy 102~MeV. The positive-parity yrast band and negative-parity cascade have been extended up to higher-spin states, respectively. The characteristics of the negative-parity sequence above the 25^－ state may related to the excitation from the nucleon in the Z=64, N=82 core. The E-GOS curve for the positive-parity yrast sequence in ¹⁵⁶Yb indicate that this nucleus may undergo an evolution from quasivibrational to quasirotational structure with increasing angular momentum. The Cranked Woods-Saxon-Strutinsky calculations by means of Total-Routhian-Surface (TRS) methods has been made to understand this structure change.     

Study of the structure of borromean nucleus 17Ne

The ¹⁷Ne nucleus is a possible candidate with a two-proton borromean halo structure. Since the theoretical model is difficult to handle the three-body system, it is difficult to determine the two-proton halo structure in ¹⁷Ne. In the present research, we try to study the breakup reaction of ¹⁷Ne. For the Borromean nuclei, one-proton knockout results in an unstable nucleus which is decaying further by proton emission. This process will result in an angular correlation between the direction of the aligned recoiling unstable nucleus and its decay products. The angular correlations can give us information about the configuration of the valence proton in the ¹⁷Ne. Furthermore, theoretical calculations indicate that the momentum distributions of ¹⁶F c.m are sensitive to the structure of the halo in ¹⁷Ne. Thus the measurement of momentum distributions of ¹⁶F c.m may also give us conclusive information on the structure of ¹⁷Ne. The present experiment has been done at IMP in Lanzhou using the radioactive beam ¹⁷Ne at 30.8 MeV/u on a 43mg/cm^{2 12}C target. The data analysis is under procedure and the primary results are provided.     

Characteristics of a 4-fold segmented clover detectore

Four high-purity germanium 4-fold segmented Clover detectors have been     

A CsI(Tl) detector array used in the experiment of the proton-rich nucleus 17Ne

To investigate the configurations of the valence protons in Borromean nucleus ¹⁷Ne, a CsI(Tl) detector array, which consists of 9 CsI crystals (26×26×20mm³) coupled with photodiodes, has been successfully used in the ¹⁷Ne experiment to measure the energy of protons. In order to find the optimal working conditions and get the best energy resolutions, several technologies (including various wrapping materials, wrapping and coupling methods) have been used. The testing results showed that the best energy resolution of the CsI(Tl) is about 3.3% using the ²⁴¹Am α-source. The primary testing results with the proton beam were also provided.     

Characteristics of a 4-fold segmented clover detectore

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.