中高能重离子弹核碎裂反应研究
Study of Heavy-ion Projectile Fragmentation in Intermediate Energy
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摘要: 通过CR-39 核径迹探测器对471 AMeV 56Fe 和400 AMeV 20Ne 诱发Al，C 和CH2 靶反应的弹核碎裂反应截面及出射角度进行了测量，并利用改进的量子分子动力学(ImQMD) 模型和描述统计衰变的GEMINI 模型对实验结果进行了分析和讨论。实验结果表明，总反应截面与弹核的能量无关，但随着靶核质量的增加而增加。这与其他的实验结果以及Bradt-Peters 的半经验理论公式所得结果一致。理论计算和实验测量结果中，分截面出现了明显的奇偶效应。理论计算结果表明，奇偶效应主要产生于受激碎块的衰变过程，其中对效应起着重要作用，而且，主要形成于擦边碰撞的反应中且多来自于同位旋为TZ = 0; ±0:5 的弹核碎块的贡献。产生碎块的同位素分布与弹核的种类有关，与入射能量和靶核的种类没有太大依赖性，其较小的偏转角大部分来自于擦边碰撞产生的较重的类弹碎块的贡献。We have measured the fragmentation cross sections and the emission angles for 471 AMeV 56Fe and 400AMeV 20Ne on Al, C and CH2 targets using CR-39 plastic nuclear track detector. The total charge changing cross sections agree well with other previous experimental results at different energies and the theoretical prediction of Bradt-Peters semiempirical formula, which are pproximately independent of the beam energy but increase with the increase of the target mass. The experimental results are compared with the prediction of the improved quantum molecular dynamical model (ImQMD) together with the GEMINI model. The odd-even effect of the partial cross sections observed in experiments is well produced. It is found that such effect is mainly formed in the grazing collisions and comes from the fragments with TZ = 0; ±0:5. The shape of the isotopic distribution is independent on the target mass and the incident energy but the projectile mass and charge, and the small angular distribution of all fragments comes from the heavier projectile-like fragments which produced in the peripheral collision.Abstract: We have measured the fragmentation cross sections and the emission angles for 471 AMeV 56Fe and 400AMeV 20Ne on Al, C and CH2 targets using CR-39 plastic nuclear track detector. The total charge changing cross sections agree well with other previous experimental results at different energies and the theoretical prediction of Bradt-Peters semiempirical formula, which are pproximately independent of the beam energy but increase with the increase of the target mass. The experimental results are compared with the prediction of the improved quantum molecular dynamical model (ImQMD) together with the GEMINI model. The odd-even effect of the partial cross sections observed in experiments is well produced. It is found that such effect is mainly formed in the grazing collisions and comes from the fragments with TZ = 0; ±0:5. The shape of the isotopic distribution is independent on the target mass and the incident energy but the projectile mass and charge, and the small angular distribution of all fragments comes from the heavier projectile-like fragments which produced in the peripheral collision.
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