MRI: Development of a Free-Electron Laser for Ultrafast Pulsed Electron Paramagnetic Resonance

MRI：开发用于超快脉冲电子顺磁共振的自由电子激光器

• 批准号: 1126894
• 负责人: Mark Sherwin
• 金额: $ 99.23万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-10-01 至 2015-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1126894&HistoricalAwards=false
• 关键词: MRI; Development; Free; Electron; Laser

Development of a Free-Electron Laser for Ultrafast Electron Magnetic ResonanceTechnical abstract: Like nuclear magnetic resonance (NMR), EPR becomes much more powerful at high magnetic fields and frequencies, and in a pulsed rather than continuous wave (cw) modality. The major bottleneck for high-field, high-frequency pulsed EPR has been the absence of electromagnetic sources capable of high frequency (100 GHz), high power (1 kW), high long-term frequency-stability, and pulse-programmability. Supported by a previous MRI grant and an award from the W. M. Keck Foundation, the world's first FEL-powered pulsed EPR spectrometer has been demonstrated at UC Santa Barbara. The most dramatic achievement is extremely rapid spin manipulation-spin ½ electrons have been rotated by 90 degrees in 6 ns at 240 GHz, two orders of magnitude faster than the next fastest 240 GHz spectrometer in the world, which is based on a solid-state source. The major research instrumentation to be developed is a free-electron laser (FEL) that is optimized for electron paramagnetic resonance (EPR) at frequencies between 240 and 500 GHz (corresponding to magnetic fields between 8.5 and 18 T). This development heavily leverages 25 years of infrastructure, investment, institutional commitment, and expertise at UC Santa Barbara. The existing 6 MV electrostatic accelerator will be upgraded and a new free-electron laser (undulator + cavity) will be built. Together, these improvements will increase the peak power available at 240 GHz from 300 W to 10 kW, the repetition rate from 1 Hz to 10 Hz, and also greatly improve the long-term stability and reliability of the system. The new FEL will bring times for 90-degree rotations of spin ½ electrons below 1 ns, enabling resolution of extremely rapid spin relaxation processes. Data acquisition times for pulsed EPR will be reduced by at least a factor of 1000. The new FEL and associated EPR spectrometer will be made available to a national and international user community, and enable transformative studies in materials science, physics, chemistry and molecular biology.Non-technical abstract: The world's brightest source of tunable terahertz radiation will be developed to manipulate electron spins faster than has ever been possible. This ultrafast spin manipulation will enable pathbreaking studies with applications ranging from development of inexpensive solar cells to understanding how protein molecules fit together and move to regulate the flow of energy, information and matter in living organisms.Electrons and atomic nuclei both have a property called spin, which makes them behave like (very tiny) magnets. In nuclear magnetic resonance (NMR), which is the basis for magnetic resonance imaging (MRI), a strong external magnetic field aligns nuclear spins, while powerful pulses of radio-frequency electromagnetic radiation manipulate nuclei to discover otherwise invisible information about neighboring atoms. Electron paramagnetic resonance (EPR), in a fashion similar to NMR, uses an external magnetic field to align electron spins (rather than nuclear spins). Typically, pulses of microwave-frequency electromagnetic radiation manipulate these electrons to learn about local environments over larger neighborhoods. EPR becomes even more powerful when extremely high-frequency terahertz radiation is used.The free-electron lasers (FELs) at the University of California at Santa Barbara (UCSB) are famous as the world's brightest sources of tunable terahertz radiation. Recently, researchers at UCSB demonstrated that one of the UCSB FELs could be used to rotate electron spins 50 times faster than ever before at .25 terahertz. This project will fund the construction of an even more powerful FEL. The new FEL, which will be used by scientists from all over the nation and world, will be 100 times more powerful than the existing one, and will pulse ten times faster, enabling at least 1000 times more rapid acquisition of experimental data. The EPR spectrometer powered by this new FEL will create an unprecedented capability to observe the structure and ultrafast dynamics of molecules, materials and devices at nanometer length scales.

开发用于超快电子磁共振的自由电子激光器技术摘要：与核磁共振 (NMR) 一样，EPR 在高磁场和频率下变得更加强大，并且在脉冲而非连续波 (CW) 模式下是主要瓶颈。对于高场、高频脉冲 EPR 来说，一直缺乏能够高频 (100 GHz)、高功率 (1 kW)、高长期频率稳定性、在 MRI 资助和 W. M. Keck 基金会的资助下，世界上第一台 FEL 驱动的脉冲 EPR 光谱仪已在加州大学圣塔分校展示，最引人注目的成就是极快的自旋操纵——自旋 1/2 电子。在 240 GHz 下 6 ns 内旋转 90 度，比世界上第二快的 240 GHz 光谱仪快两个数量级，该光谱仪基于待开发的主要研究仪器是自由电子激光器 (FEL)，该激光器针对 240 至 500 GHz 频率（对应于 8.5 至 18 T 之间的磁场）的电子顺磁共振 (EPR) 进行了优化。这一开发很大程度上利用了加州大学圣巴巴拉分校 25 年的基础设施、投资、机构承诺和专业知识，将对现有的 6 MV 静电加速器进行升级，并安装新的自由电子激光器。这些改进将共同构建，将 240 GHz 下的峰值功率从 300 W 提高到 10 kW，重复频率从 1 Hz 提高到 10 Hz，并大大提高长期稳定性和可靠性。新的 FEL 将使自旋 1/2 电子的 90 度旋转时间低于 1 ns，从而实现极快速自旋弛豫过程的分辨率，从而将脉冲 EPR 的数据采集时间缩短。至少 1000 倍。新的 FEL 和相关的 EPR 光谱仪将提供给国内和国际用户社区，并实现材料科学、物理、化学和分子生物学领域的变革性研究。非技术摘要：世界上最亮的光源将开发可调谐太赫兹辐射来以前所未有的速度操纵电子自旋，这种超快自旋操纵将使开创性的研究成为可能，其应用范围包括开发廉价的太阳能电池，以及了解蛋白质分子如何组装和移动。调节生物体中能量、信息和物质的流动。电子和原子核都具有称为自旋的特性，这使得它们在核磁共振 (NMR) 中表现得像（非常小的）磁铁，这是磁的基础。磁共振成像 (MRI) 是一种强大的外部磁场，可调整核自旋，同时强大的射频电磁辐射脉冲可操纵原子核，以类似于 NMR 的方式发现有关相邻原子的其他不可见信息。一个通常，当使用极高频太赫兹辐射时，微波频率电磁辐射脉冲会操纵这些电子来了解更大范围内的局部环境。加州大学圣塔芭芭拉分校 (UCSB) 的自由电子激光器 (FEL) 被誉为世界上最明亮的可调谐太赫兹辐射源。最近，加州大学圣塔芭芭拉分校的研究人员证明了其中之一。 UCSB FEL 可用于以 0.25 太赫兹的速度旋转电子自旋速度，该速度比以前快 50 倍。该项目将资助建造更强大的 FEL，该新 FEL 将由全国各地的科学家使用。世界上，将比现有的强大 100 倍，脉冲速度加快 10 倍，从而使实验数据的采集速度至少提高 1000 倍。前所未有的能力在纳米尺度上观察分子、材料和器件的结构和超快动力学。

项目成果

Reconstruction of Bloch wavefunctions of holes in a semiconductor

半导体中空穴布洛赫波函数的重建

• DOI: 10.1038/s41586-021-03940-2
• 发表时间: 2021-11
• 期刊: Nature
• 影响因子: 64.8
• 作者: Costello, J. B.;O’Hara, S. D.;Wu, Q.;Valovcin, D. C.;Pfeiffer, L. N.;West, K. W.;Sherwin, M. S.
• 通讯作者: Sherwin, M. S.

Optical frequency combs from high-order sideband generation

高阶边带生成的光学频率梳

• DOI: 10.1364/oe.26.029807
• 发表时间: 2018-10
• 期刊: Optics Express
• 影响因子: 3.8
• 作者: Valovcin, Darren C.;Banks, Hunter B.;Mack, Shawn;Gossard, Arthur C.;West, Kenneth;Pfeiffer, Loren;Sherwin, Mark S.
• 通讯作者: Sherwin, Mark S.