电子和原子核散射研究原子核结构

本文综述了近年来我们组利用电子散射结合相对论平均场模型对奇特核结构的研究.我们发展了相对论平均场框架下的磁电子散射方法,并用其研究一些中子晕及质子晕核的基态组态,例如,23O,17,29C和23Al.研究发现,原子核不同组态的弹性磁形状因子彼此差别很大.其次,我们发展了相对论平均场框架下的弹性库伦电子散射方法,并用该方法研究了奇特核的电荷分布.研究发现,丰质子核中扩展的电荷密度分布可以通过库伦电子散射来测量.这种方法还被进一步推广用于计算弹性宇称不守恒电子散射,研究了一些典型原子核的中子密度分布,例如,Ca同位素链,N=50同中子素链以及N=Z的双幻核.结果表明,宇称不守恒非对称度的振幅主要由质子和中子形状因子极小值之间的距离决定.这些结果为下一代电子-核对撞机上的电子散射实验提供了有用的参考.     

负载等离子体扰动对Z箍缩动态黑腔辐射温度的影响

通过二维辐射流体力学模拟研究了Z箍缩动态黑腔负载等离子体撞击泡沫柱的动力学过程,探索了带扰动负载等离子体形状对黑腔内辐射温度的影响。结果表明,带有扰动的负载等离子体撞击泡沫后会产生Rayleigh-Taylor(RT)流体不稳定性,导致动态黑腔内的辐射在负载等离子体光薄区域发生漏失,使黑腔内辐射温度降低;负载等离子体扰动振幅越大、波长越大,辐射漏失越严重,同等动能加载条件下黑腔内辐射温度也越低。     

电磁驱动超高速机械快门性能分析

高温高密度等离子体辐射源产生脉冲X射线的同时还产生等离子体碎片,飞散速度分布在0.1~10km/s。研制电磁驱动超高速机械快门,有效通光孔径为40mm×50mm,利用45mm×60mm×100μm的铝膜作为快门叶片,在放电电压20kV、驱动电流80kA、放电周期18μs条件下,获得的快门关门时间小于180μs。将快门放置在距离等离子体X射线源2m处,X射线通过后在180μs时间内关闭光学通道,以阻挡高温高密度等离子体产生的碎片,保护X射线精密探测系统和样品,同时实现等离子体参数的精密测量。     

双层丝阵Z箍缩电流分配实验研究

负载内外层电流分配是决定双层丝阵Z箍缩内爆动力学模式的关键因素. 在"强光一号"装置上, 利用微型磁探针系统定量测量了双层钨丝阵三个重要径向位置点的电流, 获得了其在驱动电流开始上升至驱动电流达到峰值之前20ns这一阶段内的时间演化行为. 实验使用的双层钨丝阵负载高度为20mm、单丝直径为3.8μm、内/外层丝阵直径分别为8mm/16mm. 对比了内/外层丝根数分别为42/21和21/42时电流分配的差异. 结果表明: 驱动电流上升过程中, 内外层丝阵的电流均逐步增大, 外层丝阵电流份额逐渐减小, 而内层丝阵电流份额逐渐增大; 内层丝阵最大电流份额未超过50%; 内/外层丝根数为21/42的负载外层电流较大. 关键词： Z箍缩 双层丝阵 电流分配     

Three-body model for neutron-halo nuclei

The neutron-halo nuclei, ¹¹Li, ¹⁴Be, and ¹⁷B, are studied in the three-body model. The Yukawa interaction is used to describe the interaction of the two-body subsystem. For given parameters of the two-body interaction, the properties of these neutron-halo nuclei are calculated with the Faddeev equations and the results are compared with those in the variational method. It is shown that the method of the Faddeev equations is more accurate. Then the dependencies of the two- and three-body energies on the parameters are studied. We find numerically that two- and three-body correlations differ greatly from each other with the variation of the intrinsic force range.     

Charge Densities of Unstable Nuclei with Electron Scattering

Relativistic mean-field theory and phase-shift analysis are combined together to investigate the elastic Coulomb scattering between electrons and unstable nuclei. Electron scattering at several different energies is studied and compared, in order to see the energy dependence of electron-nucleus scattering. It is shown that electron scattering at 200 MeV or 300 MeV can be used to reveal electron-nucleus scattering information around the first diffraction minimum. Shifts in opposite directions are obtained for the first diffraction minima of the electron scattering off the ground and first excited states of ^17F with ^16O as reference, and similar effects are obtained for ^18Ne. Besides, some neutron-rich N = 8 isotones are also studied. Results show that electron scattering will be very useful and important in studying both proton- and neutron-rich nuclei in the future.     

Theoretical study of the central depression of nuclear charge density distribution by electron scattering

The charge form factors of elastic electron scattering for isotones with N=20 and N=28 are calculated using the phase-shift analysis method, with corresponding charge density distributions from relativistic mean-field theory. The results show that there are sharp variations at the inner parts of charge distributions with the proton number decreasing. The corresponding charge form factors are divided into two groups because of the unique properties of the s-states wave functions, though the proton numbers change uniformly in two isotonic chains. Meanwhile, the shift regularities of the minima are also discussed, and we give a clear relation between the minima of the charge form factors and the corresponding charge radii. This relation is caused by the diffraction effect of the electron. Under this conclusion, we calculate the charge density distributions and the charge form factors of the A=44 nuclei chain. The results are also useful for studying the central depression in light exotic nuclei.     

基于多质点模型的准球形丝阵参数优化研究

基于多质点薄壳模型对准球形丝阵负载参数进行优化,使得终态等离子体具有预期的内爆特性。通过对丝阵初始位形优化,可以获得期望的终态等离子体壳纵横比,并且终态纵横比对负载初始质量变化不敏感。对于固定电流波形(峰值1.2 MA、上升时间80ns),优化计算了初始丝长度15.4mm的丝阵线质量。结果表明,当丝阵初始线质量约为150μg/cm时,赤道半径为2mm、纵横比为1的终态等离子体壳具有最大动能1.5kJ。同时,还针对不同幅度及上升时间的电流进行优化计算,计算结果表明终态等离子体壳的优化的最高动能与电流峰值平方成正比,与最高动能相应的线质量与电流上升时间平方成正比。     

Z箍缩驱动聚变-裂变混合堆总体概念研究进展

Z箍缩驱动聚变-裂变混合能源堆(Z-FFR)在核安全、经济、持久和环境友好等方面具有优良的品质,有望成为有效应对未来能源危机和环境、气候问题的新能源。从Z箍缩驱动聚变方案与聚变靶设计、重复频率驱动器、次临界包层及产氚包层设计、燃料循环等关键问题方面,对Z-FFR工程概念总体研究情况进行了介绍。     

电子和原子核散射研究原子核结构(英文)

本文综述了近年来我们组利用电子散射结合相对论平均场模型对奇特核结构的研究。我们发展了相对论平均场框架下的磁电子散射方法,并用其研究一些中子晕及质子晕核的基态组态,例如,23O,17,19C和23Al。研究发现,原子核不同组态的弹性磁形状因子彼此差别很大。其次,我们发展了相对论平均场框架下的弹性库伦电子散射方法,并用该方法研究了奇特核的电荷分布。研究发现,丰质子核中扩展的电荷密度分布可以通过库伦电子散射来测量。这种方法还被进一步推广用于计算弹性宇称不守恒电子散射,研究了一些典型原子核的中子密度分布,例如,Ca同位素链,N=50同中子素链以及N=Z的双幻核。结果表明,宇称不守恒非对称度的振幅主要由质子和中子形状因子极小值之间的距离决定。这些结果为下一代电子-核对撞机上的电子散射实验提供了有用的参考。