MRI: Development of X-ray Diffraction in High Magnetic Fields

MRI：强磁场中 X 射线衍射的发展

• 批准号: 1625780
• 负责人: Theo Siegrist
• 金额: $ 123.36万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1625780&HistoricalAwards=false
• 关键词: MRI; Development; ray; Diffraction; Magnetic

A magnetic field, measured in Tesla, is a fundamental physical variable, similar to pressure. As a reference, the Earth's magnetic field is of the order of 0.5mT (milli Tesla). Although X-ray diffraction at high pressures is now a common technique, X-ray diffraction and scattering techniques at steady state magnetic fields above 15 Tesla are unavailable. The new 25 Tesla Florida Split Coil Magnet provides the opportunity to change this, increasing the accessible steady-state magnetic field for X-ray studies by nearly 66%. Adding a diffraction setup to the Florida Split Coil Magnet that is located at the National High Magnetic Field Laboratory in Tallahassee, will provide unique capabilities to probe the magnetic responses in crystalline materials. The instrument will facilitate structural studies in high magnetic fields for the broader research community. Examples of materials to be studied include superconductors, ferro- and antiferromagnetic materials, as well as engineering materials. An example of the latter is rolled steel, where a martensitic phase transition can be induced at low temperatures by magnetic fields in excess of 12 Tesla. The diffractometer will consist of an X-ray source, a beam delivery system, a sample holder, and an area detector. Due to the large fringe fields emanating from the magnet, it is imperative to include magnetic field mitigation in the design of the diffractometer. Electronic and mechanical components susceptible to magnetic fields need to be removed from the space where strong fringe fields are present, requiring custom built and custom modified devices and parts. To enhance the X-ray flux delivered to the sample, additional optical elements reflecting and focusing the X-ray beam, will be included. The diffractometer will become part of the user capabilities at the NHMFL, and will be available to the user community at large via the NHMFL proposal system. The instrument will be the only one of its kind, leveraging the investment of NSF in the NHMFL and the Florida Split Coil Magnet.The National High Magnetic Field Laboratory (NHMFL) is at the forefront of resistive magnet technology, and holds the world record in DC magnetic field strength. The recent addition of the world's strongest split coil magnet, with 25T field strength and visual access to the sample allows the development of a novel X-ray diffractometer to study the spin-lattice coupling of materials at high fields. Spin-lattice interactions in crystalline materials where spin order or orbital order elicits an elastic response of the lattice that can be studied. Diffraction techniques are well suited to detect this elastic response via unit cell changes, with high accuracy. Additionally, a magnetic field can also induce magnetic phase transitions and magnetic order, and order temperatures can be shifted. Magnetostrictive effects are observed in a number of ferro-, antiferro-, and helimagnetic materials, as well as multiferroic materials that couple ferroelectric and ferromagnetic order via the magneto-electric effect. The diffractometer will consist of an X-ray source, a beam delivery system, a sample holder, and an area detector. Due to the large fringe fields, in excess of 0.2T, emanating from the magnet, it is imperative to include magnetic field mitigation in the design of the diffractometer. Electronic and mechanical components susceptible to magnetic fields need to be removed from the space where strong fringe fields are present, requiring custom built and custom modified devices and parts, together with passive and active magnetic field shielding. The diffractometer includes a high power rotating anode X-ray source, optical elements such as X-ray mirrors, evacuated beam paths, beryllium windows, a custom sample holder, and a modified X-ray area detector adapted to perform in the strong fringe fields at the X-ray exit port. The diffractometer will become part of the measurement capabilities at the NHMFL for the 25T split coil magnet, and will be available to the user community at large. The instrument will be the only one of its kind, leveraging the investment of NSF in the NHMFL and the Florida Split Coil Magnet. This system will complement the pulsed magnets at national synchrotron light sources, and it increases the available DC field strength for diffraction experiments. Development of the instrument is an excellent opportunity to train a student and postdoc in the construction and integration of components, building an instrument with unique capabilities.

以特斯拉为单位测量的磁场是一个基本的物理变量，类似于压力。作为参考，地球磁场约为0.5mT（毫特斯拉）。虽然高压下的x射线衍射现在是一种常见的技术，但在15特斯拉以上的稳态磁场下的x射线衍射和散射技术是不可用的。新的25特斯拉佛罗里达分裂线圈磁铁提供了改变这种情况的机会，将x射线研究的可访问稳态磁场增加了近66%。在位于塔拉哈西的国家高磁场实验室的佛罗里达分裂线圈磁铁上增加一个衍射装置，将提供独特的能力来探测晶体材料的磁响应。该仪器将为更广泛的研究界促进高磁场中的结构研究。要研究的材料包括超导体、铁磁性和反铁磁性材料，以及工程材料。后者的一个例子是轧制钢，在超过12特斯拉的磁场下，低温下可以诱导马氏体相变。衍射仪将由一个x射线源、一个光束输送系统、一个样品夹和一个区域探测器组成。由于磁体产生较大的条纹场，因此在衍射仪的设计中考虑磁场抑制是必要的。易受磁场影响的电子和机械部件需要从存在强边缘场的空间中移除，这需要定制和定制修改的设备和部件。为了增强传递到样品的x射线通量，将包括反射和聚焦x射线束的附加光学元件。衍射仪将成为NHMFL用户能力的一部分，并将通过NHMFL提案系统向广大用户提供。该仪器将是同类中唯一的一个，利用国家科学基金会在NHMFL和佛罗里达分裂线圈磁铁的投资。国家强磁场实验室（NHMFL）走在电阻磁体技术的前沿，保持着直流磁场强度的世界纪录。最近增加的世界上最强的分裂线圈磁铁，具有25T的场强和对样品的视觉访问，允许开发一种新型x射线衍射仪来研究高场下材料的自旋-晶格耦合。晶体材料中的自旋-晶格相互作用，其中自旋顺序或轨道顺序引起晶格的弹性响应，可以研究。衍射技术非常适合通过单元胞的变化来检测这种弹性响应，具有很高的精度。此外，磁场还可以诱导磁相变和磁有序，并且有序温度可以移动。在许多铁磁、反铁磁和helmagnetic材料以及通过磁电效应耦合铁电和铁磁顺序的多铁磁材料中观察到磁致伸缩效应。衍射仪将由一个x射线源、一个光束输送系统、一个样品夹和一个区域探测器组成。由于磁体发出的条纹场较大，超过0.2T，因此在衍射仪的设计中必须考虑磁场减缓。易受磁场影响的电子和机械部件需要从存在强边缘场的空间中移除，这需要定制和定制修改的设备和部件，以及无源和有源磁场屏蔽。衍射仪包括一个高功率旋转阳极x射线源，光学元件，如x射线反射镜，真空光束路径，铍窗，定制样品支架，和一个改进的x射线区域探测器，适合在x射线出口端口的强条纹场中工作。衍射仪将成为NHMFL 25T分裂线圈磁铁测量能力的一部分，并将提供给广大用户社区。该仪器将是同类中唯一的一个，利用国家科学基金会在NHMFL和佛罗里达分裂线圈磁铁的投资。该系统将补充脉冲磁体在国家同步加速器光源中的作用，增加了衍射实验中可用的直流场强。该仪器的开发是培养学生和博士后在组件的构建和集成方面的绝佳机会，可以构建具有独特功能的仪器。