Development of a Wolter mirror soft X-ray phase contrast microscope for the observation of biological fine structure

研制用于观察生物样品微观结构的软x射线相衬显微镜。(1)高分辨率、高倍率光学系统的建设。我们进行了高倍率光学系统的设计和生产，以获得高分辨率图像的实时图像。为了在大倍率下缩短光学系统，我们提出了一种新的光学系统。我们用一个中继光学系统布置了两个Wolter反射镜。两个光轴不在同一轴上。虽然光学系统的长度为2倍，但获得了32倍的放大倍率。由于这种改进，在实验室规模上提供了1,024倍的放大倍率。由于x射线CCD相机的像素尺寸为24μm，因此提供了优于50nm的分辨能力。(2)湿样的观察。真空室和湿样室的窗采用厚度为0.1 μm的SiN膜窗（约500 μm²）。湿标本被夹在两片SiN膜之间。我们将这个样品室设置在大约2mm厚度的空气层中。利用波长在3nm左右的连续光谱Ta靶，我们成功地拍摄了鸡湿红细胞的软x射线显微图像。(3)软x射线相衬显微镜的构建。我们建立了软x射线相衬显微镜来观察低吸收对比物。制备了两种相板，一种是环形相板，另一种是带状相板。我们获得了直径为2.8 μ m的乳胶球的软x射线相衬显微图像。所使用的软x射线是从铝靶发射的约5nm的几条谱线。

Development of a soft X-ray phase contrast microscope to observe microstructure of a biological sample.(1) Construction of a high-resolution and a high-magnification optical system.We performed design and production of a high-magnification optical system to get an image of a high-resolution image in real time. In order to shorten the optical system in large magnification we propose a new optics. We arranged two Wolter mirrors by a relay optical system. Two optical axes are not on the same axis. Although the length of the optical system was 2 times, 32 times magnification was obtained. As a result of this improvement, 1,024 times magnification was provided in a laboratory scale. Because the pixel size of an X-ray CCD camera was 24μm, the resolving power of better than 50nm were provided.(2) Observation of a wet sample.SiN film windows (about 500 μ m square) of 0.1,μm thickness were used for the windows of vacuum chambers and wet sample chambers. Wet specimens were sandwiched between two pieces of SiN membranes. We set this sample chamber in the stratum of air of about 2mm thickness. Using the Ta target which emit a continuous spectrum around 3nm in wavelength, we succeeded in taking soft X-ray microscopic images of wet red blood cells of chicken..(3) Construction of a soft X-ray phase contrast microscope.We built a soft X-ray phase contrast microscope to observe a low absorption contrast object. Two kinds of phase plates were prepared, one is a ring plate and the other is a ribbon one. We obtained soft X-ray phase contrast microscopic images of latex spheres(2.8 μ m in diameter). Soft X-rays used were several line spectra around 5nm emitted from Al target.