Hyperpolarization of helium-3 through metastable exchange optical pumping at high pressure

氦-3是从氚的核衰变产物中提取的更常见的元素氦（氦-4）的同位素。由于氦-3的核子数为奇数，它的原子核具有磁矩，它的气体可以极化到几十%的程度（超极化）。具有高度核极化的基态氦-3原子气体在核物理学、材料科学、纳米技术、量子存储器、生物物理学和医学等不同领域的应用都非常有用。在热平衡状态下，仅通过施加磁场诱导的氦-3的核极化太弱，无法用于许多此类应用。然而，在等离子体放电中，利用连续激光器通过光泵浦使氦-3高度极化是可能的。在所谓的“亚稳交换光泵浦过程”（MEOP）中，可以获得接近100%的核极化。然而，目前的技术工作在一个非常低的压力（毫巴），而大多数应用需要使用高密度和高度极化的氦-3样品接近大气压。本课题的目标是在中等磁场条件下，通过MEOP在大气压附近实现氦-3的最优极化。这项研究将在三个方面同时进行，利用我们团队的互补优势：(i)用于产生光泵氦-3原子亚稳态的等离子体放电，（ii）相对较高的磁场（~ 1特斯拉），以及（iii）结合等离子体诊断的数值模拟，等离子体中发生的激发和极化过程。该项目是两所大学（INRS和universit<s:1> de montracimal）、一个政府组织（加拿大原子能有限公司）和一个专门从事高端医疗和科学仪器开发和商业化的工业合作伙伴（Tyler Research Corporation）之间的合作。

Helium-3 is an isotope of the more common element helium (helium-4) which is extracted from the nuclear decay products of tritium. Due to its odd number of nucleons, the nuclei of Helium-3 posses a magnetic moment and its gas can be polarized to a degree of several tens of % (hyper polarization). A gas of helium-3 atoms in the ground state with a high degree of nuclear polarization is highly useful for many applications in different fields such as nuclear physics, materials science, nanotechnology, quantum memory, and biophysics and medicine. In thermal equilibrium, the nuclear polarization of helium-3 induced by only applying a magnetic field is too weak to be useful for many of these applications. However, it is possible to polarize helium-3 to a high degree inside a plasma discharge through optical pumping using a continuous laser. In the so-called "metastability exchange optical pumping process" (MEOP) a nuclear polarization close to 100% can be obtained. However, the current technique operates at a very low pressure (mbar), while most applications require the use of samples of dense and highly polarized helium-3 near atmospheric pressures.The goal of this project is to achieve optimal polarization of helium-3 through MEOP near atmospheric pressure in a moderate magnetic field. This research will be done simultaneously on three fronts, taking advantage of the complementary strengths of our team: (i) the plasma discharge used to generate the helium-3 atomic metastable states that are optically pumped, (ii) relatively high magnetic fields (~ 1 Tesla), and (iii) the numerical modeling, combined with plasma diagnostics, of the excitation and polarization process taking place in the plasma. This project is a collaboration between two universities (INRS and Université de Montréal), a government organization (Atomic Energy of Canada Limited) and an industrial partner (Tyler Research Corporation) specialized in the development and commercialization of high-end medical and scientific instruments.