Study of bright water window x-ray sources for biological x-ray microscopy using two-layered thin foil targets

为了观察活的水合生物标本，需要一个特殊的x射线源。例如，为了以50 nm的空间分辨率观察水中的蛋白质，需要1 × 10^<16>光子/sr的x射线光子。然而，以前获得的x射线光子是lx10^<12>光子/sr。本研究的目的是弥补这一差距。用原子过程计算程序和一维水动力计算程序进行了理论研究。研究发现，结合(1)使用波长更短的激光产生等离子体，(2)优化激光强度以产生合适的电子温度，(3)利用铂配合物对生物细胞进行标记技术，可以使x射线光子数增加16倍，所需光子数减少到1/100。此外，我们还通过对焦光学的研究发现，我们可以将对焦效率提高12倍。通过将所有数字放在一起，可以以高空间分辨率观察活的水合生物标本。对理论结果进行了实验验证。研制了一种带菲涅耳带片的软x射线等离子体照相机。与传统的x射线针孔相机相比，软x射线等离子相机的灵敏度提高了1000倍，空间分辨率提高了10倍。用软x射线等离子体相机观察到氩、氮、氪、氦等气体射流等离子体。研究了x射线强度与气体压力、气体原子序数和激光脉冲持续时间的关系。所得结果与理论结果定性吻合较好。为了进行定量比较，需要进一步的研究。

In order to observe live hydrated biological specimens an extraordinary x-ray source is needed. For example in order to observe proteins in water with 50 nm spatial resolution x-ray photons of 1x10^<16>photons/sr are needed. However x-ray photons obtained before are lx10^<12>photons/sr. The purpose of this research is to cover this gap.Theoretical investigation is conducted with both of atomic process calculation code and 1D hydrodynamic calculation code. It is found that combination of (1) using shorter wavelength laser to generate plasmas, (2) optimization of laser intensity to create adequate electron temperature, and (3) labeling technique on biological cells with platinum complex can increase x-ray photon number 16 times and reduce required photon number to 1/100. hi addition we also found that we can increase focusing efficiency 12 times from our research about focusing optics. By putting all numbers together, it makes possible to observe live hydrated biological specimens with high spatial resolution.Experimental investigation is conducted to prove the theoretical results. A soft x-ray plasma camera with a Fresnel zone plate was developed. The soft x-ray plasma camera has 1000 times higher sensitivity and 10 times higher spatial resolution comparing to a conventional x-ray pinhole camera. Several gas species such as argon, nitrogen, krypton, and helium gas jet plasmas are observed with the soft x-ray plasma camera. Dependence of x-ray intensity on gas pressure, atomic number of gas species, and laser pulse duration were investigated. Those results show good agreements with theoretical results qualitatively. For quantitative comparison further investigations are needed.