SGER: In-Situ Measurements of Small Angle Neutron Scattering and AC Magnetic Susceptibility of Vortex Matter

0075838 Ling这是一个探索性研究（SGER）在布朗大学的年轻教师的小补助金。他将研究涡旋相位的制度，在该制度中，由材料中的缺陷引起的随机势与涡旋-涡旋相互作用和热波动竞争，从而引起II型超导体中的“峰值效应”。 在此制度下的涡旋物理将研究在一个单晶的Nb使用线圈直接缠绕在样品上测量的涡旋动力学，同时使用小角中子散射（SANS）来测量的中子衍射图案的涡旋阵列。 该实验是高度探索性的，因为来自涡旋阵列的中子衍射信号在峰值效应区非常弱。 如果成功，该项目将产生实验结果，揭示涡旋晶格的微观性质与磁场中II型超导体的宏观性质之间的直接相关性。 涡流钉扎-脱钉问题是一个重要的技术问题，因此这项研究将有很高的回报。一名研究生将参与这项研究，从而获得在国家设施（NIST高分辨率中子散射中心）工作的经验，以及从事高风险，高回报的项目。 这应该为学生将来在学术界，工业界或政府工作做好准备。%在没有耗散的情况下携带电流的能力使得超导体在许多应用中有用，例如MRI磁体、电力传输等。大多数技术上有用的超导材料允许强磁场穿透到材料中以形成量子化的磁涡旋。 在理想的、无缺陷的II型超导体中，这些涡旋线将在电流的驱动力下移动并导致耗散。 幸运的是，原子晶格中的不完美、缺陷和杂质可以钉扎涡旋线，使超导导线能够承载大的无损电流。 因此，很好地理解随机杂质对涡旋晶格的钉扎作用对许多应用是有益的。这个探索性研究（SGER）的小额赠款将资助一个项目，该项目将使用中子束来研究涡旋晶格的微观结构，从而产生所谓的异常峰效应。 这种效应使超导体在更高的磁场和温度下携带更多的电流。 如果成功，该项目将揭示涡旋晶格的微观结构与磁场中II型超导体的宏观性质之间的直接相关性，从而帮助科学家制造更好的超导体。 参与该项目的研究生将有机会在国家设施（NIST高分辨率中子散射中心）与来自全国各地的研究人员一起工作。 这应该为学生将来在学术界，工业界或政府工作做好准备。

0075838LingThis is a Small Grant for Exploratory Research (SGER) to a young faculty member at Brown University. He will study vortex phases in the regime where the random potential caused by defects in the material competes with vortex-vortex interactions and thermal fluctuations giving rise to the "peak effect" in type-II superconductors. The vortex physics in this regime will be studied in a single crystal of Nb using a coil wound directly on the sample to measure the vortex dynamics and simultaneously using Small Angle Neutron Scattering (SANS) to measure the neutron diffraction pattern of the vortex array. This experiment is highly exploratory since the neutron diffraction signal from a vortex array is very weak in the peak effect regime. If successful, this project will generate experimental results that will reveal the direct correlation between the microscopic properties of the vortex lattice and the macroscopic properties of a type-II superconductor in a magnetic field. The question of vortex pinning-depinning is one of technological importance and thus this research could have a high payoff. A graduate student will participate in this research, thereby gaining the experience of working at a National Facility (the Center for High-Resolution Neutron Scattering at NIST) as well as working on a high-risk, high payoff project. This should prepare the student for future work in academia, industry, or government.%%%The capability to carry an electric current without dissipation makes superconductors useful in many applications such as MRI magnets, power transmission, etc. Most technologically useful superconducting materials allow a strong magnetic field to penetrate into the material to form quantized magnetic vortices. In an ideal, defect-free type-II superconductor these vortex lines will move and cause dissipation under the driving force of a current. Fortunately, imperfections, defects, and impurities, in the atomic lattice can pin the vortex lines, allowing a superconducting wire to carry a large lossless current. Therefore a good understanding of the pining of the vortex lattice by random impurities is beneficial to many applications. This Small Grant for Exploratory Research (SGER) will fund a project that will use a neutron beam to study the microscopic structure of the vortex lattice that gives rise to what is known as the anomalous peak effect. This effect allows a superconductor to carry more current at a higher magnetic field and temperature. If successful this project will reveal the direct correlation between the microscopic structure of the vortex lattice and the macroscopic properties of a type-II superconductor in a magnetic field, and thus help scientists make better superconductors. The graduate student participating in this project will have the opportunity to work at a National Facility (the Center for High-Resolution Neutron Scattering at NIST) with researches from around the country. This should prepare the student for future work in academia, industry, or government.***