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15O(α,γ)19Ne(p,γ)20Na反应链是高温CNO循环向快速质子俘获过程突破的一条关键路径,相关的反应率输入量可通过20Mg的β衰变可布居19Ne共振态并测量其衰变性质来获得。通过高效率高精度地测量20Mg β衰变中产生的质子与γ射线得到了20Mg衰变的详细信息,并构建了完整的衰变纲图,还进行了19Ne 4 033 keV共振态衰变性质的探索,获得了该态在20Mg β衰变中被布居的分支比上限。通过比20Mg和20O镜像能级跃迁的结果确认了同位旋非对称性,为检验相关理论模型提供了精确的实验数据。对于突破路径中有重要影响的19Ne 4 033 keV共振态的性质,有待更高统计的实验进一步研究。The breakout from the hot CNO cycle to the rapid proton capture process can occur via the 15O(α,γ)19Ne(p,γ)20Na reaction sequence, and the β decay of 20Mg can be used as an alternative method to characterize some specific resonances, which will provide detailed nuclear structure input for reaction rate calculations. The reliable information on the decay properties and structure of 20Mg was obtained by measuring the emitted particles and γ-rays in the β decay with high efficiency and high resolution. Attempt was also made to search for the decay channels associated with the 4 033 keV resonance in 19Ne. To test fundamental symmetries, the transitions in the mirror decays of 20Mg and 20O were compared. The precise experimental data presented here would be important to constrain the theoretical calculations. It is desirable to clarify the astrophysically relevant problem by further experiments with improved statistics on the basis of the present work.  相似文献   
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中国科学院近代物理研究所气体探测器组研制了一种大型位置灵敏的平行板雪崩计数器(PPAC)。它主要由中心阴极和XY位置阳极构成,灵敏面积为244 mm×284 mm,阴极为双面镀金1.5 μm厚的Mylar膜,阳极为直径20 μm,间距1 mm的镀金钨丝。位置读出选用延迟块读出法。这种探测器经测试在灵敏面积内位置分辨小于4 mm,时间分辨为0.42 ns,已在兰州放射性束流线(RIBLL)上清华大学的核反应实验中使用。该实验中使用了主束40Ar直接轰击Au靶,产生裂变碎片,使用了4个这种大型位置灵敏的PPAC,用来探测裂变碎片的飞行时间和速度,实验表明,PPAC对裂变碎片有90.3%的效率,给出了裂变碎片的位置分布,为理论分析工作提供了非常好的实验数据。A kind of large position sensitive parallel plate avalanche counter(PPAC) was developed at Gas Detector Research Group, Institute of Modern Physics of CAS. Each of the detector with large sensitive area of 244 mm×284 mm, consists of one central cathode, X anode and Y anode. The cathode plane in the middle of detector is a 1.5 μm thick Mylar foil coated with a thin Au-layer on both sides. The position resolution of the PPAC is better than 4 mm, and the time resolution is 0.42 ns. The detectors were used in the fission experiment with 30MeV/u 40Ar beam bombarding on a gold target to measure the velocity of the fission fragments at Radioactive Ion Beam Line In Lanzhou(RIBLL). Four PPACs were used and the experiment result showed that a rather high detection efficiency (90.3%) is achieved. The position distribution of fission fragments is given by PPACs, which provides very good experimental data for further theoretical analysis.  相似文献   
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