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; 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技术摘要的自由电子激光器：像核磁共振（NMR）一样，EPR在高磁场和频率下，在脉冲而不是连续波（CW）模态下变得更强大。高场，高频脉冲EPR的主要瓶颈是缺乏能够具有高频（100 GHz），高功率（1 kW），高长期频率稳定性和脉冲效能的电磁源。在先前的MRI赠款和W. M. Keck基金会的奖励的支持下，全球第一个由FEL驱动的EPR光谱仪在UC Santa Barbara上得到了证明。最引人注目的成就是在240 GHz的6 ns中旋转了90度，这是非常快速的自旋操作旋转½电子，比世界上下一个最快的240 GHz光谱仪快两个数量级，基于固态源。要开发的主要研究仪器是一种自由电子激光器（FEL），该激光器（FEL）在240至500 GHz之间的频率（对应于8.5和18 t之间的磁场）中对电子顺磁共振（EPR）进行了优化。这一发展大大利用了加州大学圣塔芭芭拉分校的25年基础设施，投资，机构承诺和专业知识。现有的6 MV静电加速器将升级，并将建立新的自由电子激光器（Undunator +腔）。总之，这些改进将使240 GHz的峰值功率从300 W增加到10 kW，重复速率从1 Hz到10 Hz，也大大提高了系统的长期稳定性和可靠性。新的FEL将带来以下90度旋转的自旋½电子旋转的时间，从而可以解决极快的自旋松弛过程的分辨率。 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.这种超快的自旋操作将通过适用于廉价太阳能电池的开发到了解蛋白质分子如何融合在一起并进行调节活性生物中的能量，信息和物质的流动。电子和原子核具有称为旋转的特性，这使得它们的行为（非常微小）的磁铁。在磁共振成像（MRI）的基础（MRI）的核磁共振（NMR）中，强大的外部磁场对齐核自旋，而无线电电磁辐射的强大脉冲操纵核，以发现有关相邻原子的原本不可见信息。电子顺磁共振共振（EPR）以类似于NMR的方式使用外部磁场来对齐电子旋转（而不是核自旋）。通常，微波频率电磁辐射的脉冲操纵这些电子，以了解较大社区的本地环境。当使用极高的Terahertz辐射时，EPR变得更加强大。加利福尼亚大学圣塔芭芭拉分校（UCSB）的自由电子激光器（FELS）是世界上最明亮的Terahertz辐射的来源。最近，UCSB的研究人员表明，UCSB Fels之一可用于将电子旋转旋转比以往任何时候以0.25 Terahertz快50倍。该项目将资助更强大的FEL的建设。新的FEL将由来自全国和世界各地的科学家使用，将比现有的FEL强大100倍，并将更快地脉动10倍，从而使实验数据的快速获取至少1000倍。由该新FEL提供动力的EPR光谱仪将创建前所未有的能力，以观察纳米长度尺度下分子，材料和设备的结构和超快动力学。