电荷半径是原子核最基本的观测量之一，反映了原子核内部的质子分布和核子间的相互作用。目前，高精度的电荷半径数据已广泛应用于探索奇特原子核的结构和性质，对"中子晕"等的发现起了关键作用。电荷改变截面(CCCS)的实验测量是最近发展起来的一种研究电荷半径的新方法，这种方法尤其适于探索产额很低的奇特原子核。然而，目前CCCS方法主要应用于Z≤9的原子核。对于较重的原子核体系，CCCS方法的适用性有待实验进一步检验。基于近代物理物理研究所放射性束流线RIBLL2和外靶终端，我们提议在相对论能区测量29-31Si的CCCS，研究CCCS对入射能量和反应靶的依赖性，探索较重原子核体系的CCCS变化规律，提出适用于较重核区的Glauber模型，最终利用29-30Si定标，提取出31Si的电荷半径以及电荷密度分布。

Charge radius is one of the most fundamental observables of atomic nuclides, which reflects the proton distribution and thus the nuclear forces inside atomic nuclei. So far, high-precision nuclear charge radii have been an important probe for studying nuclear ground state properties, searching for new exotic phenomena, examining various nuclear models and exploring the equation of state at low temperature, and has contributed significantly to many discoveries such as "neutron halo". In the last three years, nuclear charge-changing cross section (CCCS) measurements have been developed well and provided a new and powerful tools to determine nuclear charge radii. This method is especially suitable for mapping those exotic nuclei with low yield, and can be used as a complementary method to the isotopic shift. The CCCS method was used mainly in light nuclei with Z≤9 in previous studies, and thus the universal scaling law found in the CCCS method needs further investigation when applying to heavier systems. In this project, we propose to measure the CCCS of 29-31Si, typical nuclides in the sd shell, at relativistic energies at the radioactive beam line RIBLL2 and the external target facility (ETF) at IMP. By studying the dependence of CCCS on the reaction energies and targets, we are aiming to establish a better way to extract charge radii based on the Glauber-type model, and eventually to determine the charge radius of the unstable nuclide 31Si using 29,30Si as calibrator for the CCCS method.