HIGH PERFORMANCE NEUTRON DETECTOR FOR PROTEIN CRYSTALLOGRAPHY

描述（由申请人提供）：最近，随着固定式和便携式的新中子源数量的增加，以类似的方式对中子的利用不断增加。与X相反-和？-射线，中子与物质相互作用的概率不取决于原子序数，但在整个周期表中是相当不规则的，并取决于吸收体的核结构。与X射线不同，中子可以很容易地穿透许多重元素，但很容易被各种轻同位素吸收或散射，如氢，氘或锂。因此，中子可以提供信息，否则将逃脱检测由传统的射线照相术。在生物医学和制药研究中，中子用于大分子晶体学，以研究分子和蛋白质的结构，其中主要由轻元素组成。中子散射实验不仅可以解决原子的位置（弹性散射），而且还可以解决它们的动力学（非弹性散射）。由于氢和氘的散射截面存在巨大差异，中子使得解决氢交换过程成为可能，这远远超出了X射线的能力。虽然中子研究在生物医学科学中的好处是显而易见的，但目前这种研究的范围受到现有中子探测器的限制。该项目的目标是探索一种基于明亮钆（Gd）化合物的中子成像研究的新探测器。Gd基探测器的优点是这种元素具有最高的热中子吸收截面。这意味着只需要非常薄的这种材料层（200微米或更小）就能吸收近100%的热中子。这一点很重要，原因有三。首先，它提高了中子束的利用率。其次，它将提供更好的空间分辨率（小于1 mm），从而提高仪器的分辨率。由于生物样品的尺寸通常为毫米量级，因此它是重要的参数。第三，薄层将具有用于伽马吸收的小横截面，减少伽马背景并提高信噪比。大分子（如蛋白质）的结构与其功能和性质密切相关。中子晶体学可以精确地确定氢原子的位置，并帮助确定分子的结构。中子探测器仪器的进步将提供更好的能力来定义这些结构，并帮助识别分子的目的。

DESCRIPTION (provided by applicant): Recently, with the increase in number of new neutron sources, stationary as well as portable, there has been growing utilization of neutrons in a similar manner. Contrary to X- and ?-rays, the probability of interaction of neutrons with matter does not depend on the atomic number but is rather irregular across the periodic table and depends on the nuclear structure of the absorber. Unlike X-rays, neutrons can easily penetrate many heavy elements, but are readily absorbed or scattered by various light isotopes, like hydrogen, deuterium, or lithium. Consequently, neutrons can provide information that would otherwise escape detection by conventional radiography. In biomedical and pharmaceutical research, neutrons are used in macromolecular crystallography to investigate the structure of molecules and proteins, which consist mostly of light elements. Neutron scattering experiments can resolve not only the atomic positions (elastic scattering) but also their dynamics (inelastic scattering). Due to the huge difference in scattering cross-section of hydrogen and deuterium, neutrons make it possible to resolve hydrogen exchange processes that are well beyond the capabilities of X-rays. While the benefits of neutron studies in biomedical sciences are obvious, the scope of such studies is limited at present by the available neutron detectors. The goal of the proposed project is to explore a new detector for neutron imaging studies based on a bright Gadolinium (Gd) compound. Advantage of Gd-based detectors is that this element has the highest cross-section for absorption of thermal neutrons. It means that only very thin layers of this material (200 microns or less) are required for nearly 100% absorption of thermal neutrons. This is important for three reasons. First, it improves utilization of the neutron beam. Second, it will provide better spatial resolution (less 1 mm) thus it will improve the resolving power of the instrumentation. Since the biological samples are usually on the order of millimeter in size it is important parameter. Third, thin layers will have small cross-section for gamma absorption, reducing gamma background and improving signal to noise ratio. The macromolecular (e.g. protein) structure strongly relates to its function and properties. Neutron crystallography can precisely pinpoint location of hydrogen atoms and help to define molecule's structure. Advancements in neutron detector instrumentation will provide better capabilities define these structures and help to recognize the molecule's purpose.