为研究快点火预压缩过程中导引锥对压缩靶丸芯部辐射对称性的影响，在神光Ⅲ原型上开展了快点火预压缩的自发光测量实验。采集了相同长度黑腔中不同类型靶丸的内爆自发光图像和不同长度黑腔中同类靶丸的内爆自发光图像，利用最小二乘椭圆拟合方法对芯部的自发光半峰值强度等高线进行椭圆拟合，通过椭圆特征来分析靶丸在最强发光时刻的压缩对称性。分析结果表明: 导引锥的存在会使发光区域沿着赤道方向拉长，降低了压缩对称性;有锥靶丸在1600 μm黑腔内的形变小于在1500 μm和1700 μm黑腔内的形变，压缩对称性可以通过调整黑腔长度来控制。

In order to study the influence of guiding cone on radiation symmetry of compressed core, X-ray emission measurements in fast ignition pre-compression were tested on Shenguang Ⅲ prototype facility. Emission images of different targets in hohlraums with the same length and that of the same target in hohlraums with different lengths were recorded. Least-square ellipse fitting was applied to 50% peak intensity contour, thus the ellipse characters could be used to numerically analyze the core compression symmetry at peak emission time. The results validate that the compression symmetry is reduced, as the emission region is stretched in equatorial direction, if the target is attached to a gold cone. The compression symmetry can be adjusted by hohlraum length, as the shape deformations of cone-guide target in hohlraum with 1600 μm length is less than that in hohlraums with 1500 μm and 1700 μm length.