高对称度光源的同步辐射X射线同轴相衬成像

发布时间：2018-07-10 00:02

本文选题：X射线同轴相位衬度成像 + 光源对称度　；参考：《科学通报》2017年22期

【摘要】：全球现有的同步辐射光源中,电子束团在垂直于运动方向的截面上其水平尺寸和垂直尺寸的差异都较大,即同步辐射X射线(SRX)源的尺寸在水平和垂直两方向上有较大差异(二者的比值为光源的对称度,与1的差别越大,则对称度越差).这使得利用同步辐射X射线开展同轴相衬成像实验时,水平和垂直两个方向上入射X射线的点扩展函数相差较大,造成两个方向上空间分辨率有很大差别,这种差异还会造成两个方向上相位衬度水平的明显差别,从而严重影响同轴相位衬度成像的质量.本文通过在北京同步辐射装置(BSRF)成像线站(4W1A)束线上加入白光光阑直接限制光源对样品的点扩展函数的方法,获得了一个对称度大大提高的同步辐射X射线源(光源对称度从2.7提高到接近1),并开展了模型样品(聚酰胺细丝)的同轴相位衬度成像实验.使4W1A的光源对称度从2.7提高到1,虽然会使总通量约减小为原来的0.0005,但通量密度只减小到原来的0.22.总通量的减小由光斑尺寸的减小和通量密度的减小共同决定,由于高分辨率同轴成像需要的光斑尺寸很小,因此本方法对高分辨率同轴成像的不利影响仅限于通量密度的减小.同时,研究结果表明,通过关小水平光阑尺寸,把对成像有贡献的水平方向光源尺寸从1.23 mm减小到约0.35 mm,使模型样品成像的最大相位衬度从0.057提高到了0.35,即通过关小光阑提高光源的对称度,使同轴相衬成像的密度灵敏度提高了5倍.光源对称度的提高,使空间分辨率和相位衬度这两方面在水平方向和垂直方向达到相同的水平,从而极大改善了BSRF 4W1A线站SRX同轴相位衬度成像的质量.我们分析了成像质量提升的原因,并讨论了未来进一步改进的方向.
[Abstract]:Among the existing synchrotron radiation sources in the world, the electron beam clusters differ greatly in horizontal and vertical dimensions in the cross sections perpendicular to the direction of motion. That is, the size of synchrotron radiation X-ray (SRX) source is different in horizontal and vertical directions (the ratio of the two is the symmetry of light source, the greater the difference between SRX and 1, the more symmetrical degree is). As a result, when the synchrotron radiation X-ray is used to carry out the experiment of coaxial phase contrast imaging, the point spread function of the incident X-ray in horizontal and vertical directions is quite different, resulting in a great difference in spatial resolution between the two directions. This difference will also result in a significant difference in phase contrast levels in two directions, thus seriously affecting the quality of coaxial phase contrast imaging. In this paper, a white aperture is added to the beam line of the Beijing Synchrotron radiation Facility (BSRF) imaging line station (4W1A) to limit the point spread function of the light source to the sample directly. A synchrotron radiation X-ray source (light source symmetry is increased from 2.7 to nearly 1) has been obtained, and the coaxial phase contrast imaging experiments of the model sample (polyamide filament) have been carried out. When the light source symmetry of 4W1A is increased from 2.7 to 1, the total flux is reduced to 0.0005, but the flux density is reduced to 0.22. The decrease of total flux is determined by the decrease of spot size and flux density. The negative effect of this method on high-resolution coaxial imaging is limited to the decrease of flux density due to the small size of spot size required for high-resolution coaxial imaging. At the same time, the results show that, by turning off the size of the horizontal diaphragm, The dimension of the horizontal light source, which contributes to the imaging, is reduced from 1.23 mm to about 0.35 mm, and the maximum phase contrast of the model sample is increased from 0.057 to 0.35, that is to say, the symmetry of the light source is improved by turning off a small aperture. The density sensitivity of coaxial phase contrast imaging is increased by 5 times. With the increase of light source symmetry, the spatial resolution and phase contrast reach the same level in both horizontal and vertical directions, thus greatly improving the quality of SRX coaxial phase contrast imaging in BSRF4W1A line station. We analyze the reasons for the improvement of imaging quality and discuss the direction of further improvement in the future.
【作者单位】：中国科学院高能物理研究所;中国科学院北京综合研究中心;
【基金】：中国科学院科研装备研制项目(YZ201211);中国科学院北京综合研究中心创新课题(2014-01);中国科学院北京综合研究中心自主部署课题(Y5Z003) 国家自然科学基金(11675208,11305200)资助
【分类号】：O434.1

【相似文献】