GOALI: Resolving Outstanding Questions in Spin-Exchange Optical Pumping of 129Xe

GOALI：解决129Xe自旋交换光泵浦中的突出问题

• 批准号: 1708048
• 负责人: Brian Saam
• 金额: $ 42.23万
• 依托单位: Washington State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-15 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1708048&HistoricalAwards=false
• 关键词: GOALI; Resolving; Outstanding; Questions; Spin

Magnetic resonance imaging of gas inside the lungs or other similar spaces where gases can be admitted utilizes as the active medium noble gases that have had their magnetic nuclei aligned to point in the same direction, a process known as noble-gas MRI. Effective use of the process today is only possible if the sensitivity is enhanced by spin-exchange optical pumping (SEOP) for preparing the spin-polarized noble gas samples (helium-3 or xenon-129) to be used in the imaging procedure. This research focuses on the SEOP process itself, in which angular momentum is transferred first from light to alkali-metal atoms that absorb the light and then transfer the momentum to the noble-gas atoms through collisions. The collisions align (or polarize) the magnetic nuclei, bringing their north and south magnetic poles in mutual alignment, thereby rendering them useful for MRI studies. This project will address some open questions relating to how the efficiency of SEOP depends on the laser power, the laser bandwidth, the choice of alkali-metal atoms, and the pressure of the buffer gas in the gas mixtures. SEOP of xenon-129 (129Xe) is of particular interest because it is less well understood, and because it may supersede helium-3 as the atom of choice for noble-gas MRI. The industrial partner for this GOALI project, Polarean, Inc., is at the forefront of 129Xe-MRI technological development. This project will enable university researchers to collaborate with Polarean, Inc. to study physics issues related to SEOP of 129Xe, and to use the resulting knowledge to improve a commercial polarization device. The three main research aims are: (1) Pushing Rubidium-129Xe SEOP toward ultra-fast rates: The goal is to demonstrate and implement quantitative gains in the spin-exchange efficiency in the less-studied low-buffer-gas-density regime (~ 0.1 amagat). The ultra-narrow OptiGrate laser allows significant light deposition even for the much narrower rubidium D1 absorption line in this regime. (We note that Optigrate is a second industrial collaborator in this project.) (2) Direct comparison of rubidium to cesium for use in SEOP: The goal is to make quantitative measurements of Rb-129Xe and Cs-129Xe SEOP parameters using the common platform of the dual-head high-power Rb/Cs diode laser, in order to determine whether and to what degree Cs is advantageous. (3) The role of alkali-metal clusters in limiting SEOP efficiency: The goal is to obtain direct evidence for these potentially deleterious nanoclusters in a SEOP polarizer and incorporate their effects into the "standard model" for 129Xe SEOP. Meeting each of these goals has a direct impact on the efficiency of 129Xe SEOP, elucidating some interesting (and heretofore elusive) physics while also leading to improved production of HP 129Xe for applications such as lung MRI.

肺内气体或其他可吸入气体的类似空间的磁共振成像利用惰性气体作为活性介质，这些惰性气体的磁核排列指向同一方向，这一过程被称为惰性气体MRI。只有通过自旋交换光泵浦（SEOP）来提高灵敏度，以制备用于成像过程的自旋极化惰性气体样品（氦-3或氙-129），才能有效地利用这一过程。这项研究的重点是SEOP过程本身，在这个过程中，角动量首先从光转移到吸收光的碱金属原子，然后通过碰撞将动量转移到稀有气体原子。碰撞使磁核排列（或极化），使它们的南北磁极相互排列，从而使它们对MRI研究有用。该项目将解决一些悬而未决的问题，如SEOP的效率如何取决于激光功率、激光带宽、碱金属原子的选择以及气体混合物中缓冲气体的压力。氙-129 （129Xe）的SEOP之所以特别令人感兴趣，是因为人们对它知之甚少，而且它可能取代氦-3成为惰性气体核磁共振成像的首选原子。GOALI项目的工业合作伙伴Polarean公司是129x - mri技术发展的前沿。该项目将使大学研究人员能够与Polarean公司合作，研究129Xe的SEOP相关的物理问题，并利用由此产生的知识来改进商用偏振装置。三个主要的研究目标是：(1)推动铷- 129xe SEOP向超快速率发展：目标是证明和实现在研究较少的低缓冲气体密度（~ 0.1 amagat）下自旋交换效率的定量增益。超窄的OptiGrate激光器允许显著的光沉积，甚至更窄的铷D1吸收线在这个制度。（我们注意到，Optigrate是该项目的第二个工业合作伙伴。）(2)用于SEOP的铷与铯的直接比较：目的是利用双头大功率Rb/Cs二极管激光器的共同平台，对Rb- 129xe和Cs- 129xe SEOP参数进行定量测量，以确定Cs是否具有优势以及在多大程度上具有优势。(3)碱金属团簇在限制SEOP效率中的作用：目标是在SEOP偏振器中获得这些潜在有害的纳米团簇的直接证据，并将其影响纳入129Xe SEOP的“标准模型”。满足这些目标对129Xe SEOP的效率有直接影响，阐明了一些有趣的（迄今为止难以捉摸的）物理特性，同时也提高了用于肺部MRI等应用的HP 129Xe的产量。

项目成果

Collisional electron paramagnetic resonance frequency shifts in Cs-Rb-Xe mixtures

Cs-Rb-Xe 混合物中的碰撞电子顺磁共振频移

• DOI: 10.1103/physreva.106.012801
• 发表时间: 2022
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Zou, S.;Morin, D. J.;Weaver, C.;Armanfard, Z.;Muschell, J.;Nahlawi, A. I.;Saam, B.
• 通讯作者: Saam, B.

Electron and nuclear spin polarization in Rb-Xe spin-exchange optical hyperpolarization

Rb-Xe 自旋交换光学超极化中的电子和核自旋极化

• DOI: 10.1103/physreva.95.032509
• 发表时间: 2017
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Hanni, Matti;Lantto, Perttu;Repiský, Michal;Mareš, Jiří;Saam, Brian;Vaara, Juha
• 通讯作者: Vaara, Juha