MRI: Acquisition of a Multipole Wiggler for the LSU Synchrotron for Protein Crystallography, Tomography, X-ray Absorption, Radiology, and Microfabrication

技术摘要：用多极摆动器取代目前的单极波长移频器将使x射线通量增加约10倍，并将有用强度的范围扩展到更高的能量。该摆动器将服务于CAMD同步加速器上的4条光束线，将极大地促进以下领域的研究。蛋白质晶体学：更高的亮度将允许涉及更小晶体和/或更高分辨率数据集的研究，这两者都需要目前无法获得的强度水平。减少数据收集时间将提高光束线的生产率。断层扫描：MPW的横向光束相干性增加，估计为0.2µm，将实现新的全场相衬成像，这是增强样品图像对比度的有力方法。此外，增加的通量将使实际的高分辨率断层扫描，约3 μ m，大视场样品。医学放射学：目前的研究目标是一种潜在的新型放射疗法，称为k -边缘捕获疗法，该疗法通过一种靶向癌细胞的药物来定位剂量。双能量k边缘成像和相衬成像在诊断成像，包括乳腺癌筛查中具有重要的潜力。x射线的强度和能量的增加将使研究扩展到Gd和其他高z造影剂。x射线光谱学：在4到24 keV范围内，x射线通量增加了10到14倍，这将提高XANES和EXAFS的信噪比，并将允许进行包括原位催化剂研究、稀释金属污染物的环境研究和完整蛋白质中的金属位点的实验。几乎所有过渡金属的K或L边都是可接近的。微加工：来自MPW的高能量光子将改善高纵横比微结构的制造，这是x射线光刻的独特优势。摘要：提出的多极摆动子产生的光子被称为？硬x射线?。它们的波长与原子之间的距离相当，可以穿过物质而不会造成重大损害。这种独特的性质组合使硬x射线成为确定结晶分子结构的理想选择，包括非常大的分子，如蛋白质，以及研究固体的内部结构。基于x射线的结构测定是现代药物发现的重要组成部分。硬x射线的其他应用利用了这样一个事实，即每种元素都吸收该元素特定波长的x射线。通过选择合适的波长，研究人员可以研究分子中单个原子的化学状态。这是研究环境污染的重要工具。同样的特性可以通过将辐射剂量定位到标记有肿瘤特异性药物的区域来增强放射治疗的有效性。所有这些应用都需要能产生所需波长辐射的强x射线源。当环内的电子束通过磁场时，同步加速器环可以成为强x射线源。我们建议在路易斯安那州立大学现有的同步加速器上安装11块超强超导磁体。这种被称为多极摆动器的装置将使实验人员可获得的x射线强度提高10倍以上，并且高强度输出将扩展到更宽的波长范围。上述所有应用都将受益于这种新型多极摆动器。

0923440NewcomerLA State U & A&M CollegeTechnical Summary: Replacing the current single-pole wavelength shifter with a multipole wiggler will increase the X-ray flux by about 10 fold and extend the range of useful intensities to higher energies. The wiggler will serve 4 beamlines on the CAMD synchrotron and will greatly benefit researchers in the following fields. Protein Crystallography: The higher brightness will allow studies involving smaller crys-tals and/or higher resolution data sets, both requiring intensity levels currently unavailable. Re-duced data collection times will increase the productivity of the beamline. Tomography: The increased transverse beam coherence of the MPW, estimated at 0.2 µm, will enable new full-field phase contrast imaging, a powerful method of enhancing image contrast in samples. Also, the increased flux will enable practical high resolution tomography, about 3 µm, for large field-of-view samples. Medical Radiology: Current research is aimed at a potentially new radiation therapy called K-edge capture therapy in which the dose is localized by means of a drug that targets can-cer cells. Dual energy K-edge imaging and phase contrast imaging have significant potential in diagnostic imaging, including breast cancer screening. The increased intensity and energy of X-rays will allow studies to be extended to Gd and other high-Z contrast agents. X-ray Spectroscopy: The 10 to 14-fold greater X-ray flux in the range of 4 to 24 keV will improve signal-to-noise ratio in XANES and EXAFS and will permit experiments that include in-situ catalyst studies, environmental studies of dilute metal pollutants and of metal sites in in-tact proteins. The K or L edges of almost all transition metals will be accessible. Microfabrication: Higher energy photons from the MPW will improve the fabrication of high aspect ratio microstructures, a unique advantage of X-ray lithography.Lay Summary: The photons produced by the proposed multipole wiggler are called ?hard X-rays?. They have wavelengths comparable to the distance between atoms and can pass through matter without causing significant damage. This unique combination of properties makes hard X-rays ideal for determining the structure of crystallized molecules, including very large mole-cules such as proteins, and for investigating the internal structures of solids. X-ray based struc-ture determination is an essential part of modern drug discovery. Other applications for hard X-rays exploit the fact that each element absorbs X-rays at certain wavelengths characteristic of that element. By selecting an appropriate wavelength, re-searchers can investigate the chemical state of individual atoms in a molecule. This is an impor-tant tool in studies of environmental contamination. The same property may be used to enhance the effectiveness of radiation therapy by localizing the radiation dose to regions labeled with tu-mor-specific drugs. All of these applications require an intense source of X-rays that can produce radiation of the desired wavelengths. Synchrotron rings can be strong sources of X-rays when the electron beam inside the ring is passed through a magnetic field. We are proposing to install a set of 11 very strong superconducting magnets on the existing synchrotron at Louisiana State University. This device, known as a Mulitpole Wiggler, will increase the intensity of the X-rays available to experimenters by more than 10 fold and the high-intensity output will extend over a wide range of wavelengths. All of the applications mentioned above will benefit greatly from the new mul-tipole wiggler.