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

氦-3是更常见的元素氦(氦-4)的一种同位素，氦-4是从氚的核衰变产物中提取的。由于氦-3的核子数是奇数，所以它的原子核具有磁矩，其气体的极化程度可以达到几十%(超极化)。氦-3原子的基态气体具有高度的核极化，在核物理、材料科学、纳米技术、量子存储、生物物理和医学等领域具有重要的应用价值。在热平衡中，仅通过施加磁场引起的氦-3的核极化太弱，不适用于其中的许多应用。然而，通过使用连续激光的光学泵浦，可以在等离子体放电中高度极化氦-3。在所谓的“亚稳态交换光学泵浦过程”(MEOP)中，可以获得接近100%的核偏振。然而，目前的技术工作在很低的气压(Mbar)下，而大多数应用需要在大气压附近使用致密和高度极化的氦-3样品，该项目的目标是在中等磁场下通过大气压附近的MEOP实现氦-3的最佳极化。这项研究将同时在三个方面进行，利用我们团队的互补优势：(I)用于产生光抽运的氦-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)结合等离子体诊断对等离子体中发生的激发和极化过程的数值模拟。该项目是两所大学(INRS和蒙特利尔大学)、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(泰勒研究公司)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.