collinear laser quantum control of nuclear spins

加拿大粒子加速器中心（TRIUMF）的激光核偏振装置由连续波窄带宽染料激光系统和偏振器光束线组成，利用“光泵浦”将各种核自旋极化放射性同位素输送到众多实验中。在光泵浦过程中，圆偏振激光作为特定方向角动量的载体，可以通过光子的吸收和发射将动量传递给感兴趣的原子/离子，并通过电子-核相互作用将动量传递给原子/离子的原子核。这种方法可以提供高达80%的核极化，这是核磁共振界非常期望的，被称为“超极化”。偏振器装置位于TRIUMF的同位素分离器和加速器设施内，是世界上为数不多的能够提供短寿命放射性原子核的高核自旋极化光束的装置之一。该设施为研究材料特性、生化过程、核结构和基本对称性开辟了独特的途径。随着用户群体日益增长的需求，作为TRIUMF 20年计划的一部分，正在准备大规模扩大用户站。该申请为HQP培训寻求资金支持，以开发用于新兴研究的各种同位素的核自旋控制方案和技术。短期目标是开发实用的方案，使核自旋极化230,232Ac和58,74cu，因为它们在阿尔茨海默病和癌症方面有很好的应用前景。由于不同同位素具有独特的原子性质，如同位素位移（IS）和超精细结构（HFS），因此必须对每种同位素进行彻底的研究，以建立合适的光泵浦方案。长期目标是发展一种通用极化技术。使用脉冲激光器的“腔辅助”光泵浦将被研究。脉冲激光器固有的宽带宽可以同时泵送所有HFS亚能级，从而实现极化，而无需区分不同同位素的IS和HFS。目前的光泵浦方法使用连续波激光器，因为足够的泵浦周期需要很长的相互作用时间，直到实现偏振。在脉冲拉伸光学腔的帮助下，可以克服脉冲激光器的这一限制。另一种途径是利用自旋极化碱蒸汽混合物作为自旋交换介质，将极化传递到原子/离子束，从而将激光系统简化为一般使用的一个设置。该项目将培养下一代研究人员在这一不断扩大的激光自旋操纵技术的跨学科应用中，使他们与偏振光的用户合作，并推动研发向高效和简化的核自旋控制系统，以提供不同科学界所需的各种核物种。

TRIUMF's (Canada's particle accelerator centre) laser nuclear-polarization facility, consisting of a continuous-wave, narrow-bandwidth dye laser system and a polarizer beam line, utilizes "optical pumping" to deliver various nuclear-spin-polarized radioactive isotopes to a multitude of experiments. In the optical pumping process, circularly polarized laser light, as a carrier of angular momentum in a specific direction, can transfer the momentum to the atoms/ions of interest via absorption and emission of photons, and further to the nuclei of the atoms/ions via electron-nucleus interactions. This method can provide nuclear polarization of up to 80%, which is highly desired and referred to as "hyperpolarization" by the Nuclear Magnetic Resonance community. Situated in the isotope separator and accelerator facility at TRIUMF, the polarizer facility is one of a few in the world which can provide access to highly nuclear-spin-polarized beams of short-lived radioactive nuclei. This facility has opened unique avenues to investigate material properties, biochemical processes, nuclear structures and fundamental symmetries. With growing demands from user communities, a major expansion of user stations is under preparation as part of TRIUMF's 20 year plan. This application seeks funding support for HQP training in developing nuclear-spin-control schemes and techniques for a variety of isotopes for emerging research. The short term goal is to develop practical schemes to nuclear-spin polarize 230,232Ac and 58,74Cu, due to their promising applications to Alzheimer's disease and cancers. Due to unique atomic properties such as isotope shifts (IS) and hyperfine structures (HFS) for different isotopes, a thorough investigation must be made for each isotope to establish a proper optical pumping scheme. The long term goal is to develop a universal polarization technique. "Cavity-assisted" optical pumping using pulsed lasers will be investigated. The broad bandwidth inherent to pulsed lasers can enable simultaneous pumping of all HFS sublevels, thus achieving polarization without distinguishing IS and HFS of different isotopes. The current optical pumping method uses continuous-wave lasers, due to the long interaction time needed for enough pumping cycles until polarization is achieved. With the assistance of a pulse-stretching optical cavity, this limitation of pulsed lasers can be overcome. Another avenue is to utilize a spin-polarized alkali-vapor mixture as a spin-exchange medium to transfer polarization to atom/ion beams, thus simplifying the laser system to one setup for general use. The program will train the next generation of researchers in this expanding interdisciplinary application of laser spin-manipulation techniques, expose them to collaborations with users of polarized beams, as well as drive R&D towards efficient and simplified nuclear spin control system to supply a variety of nuclear species demanded from different scientific communities.