collinear laser quantum control of nuclear spins

核自旋的共线激光量子控制

• 批准号: RGPIN-2021-02993
• 负责人: Li, Ruohong
• 金额: $ 2.4万
• 依托单位: University of Windsor
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=762519
• 关键词: collinear; laser; quantum; control; nuclear

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.

TRIUMF(加拿大粒子加速器中心)激光核偏振装置由一个连续波、窄带宽染料激光系统和一条偏振器光束线组成，利用“光学泵浦”将各种核自旋偏振的放射性同位素输送到多个实验中。在光泵浦过程中，圆偏振激光作为特定方向的角动量载体，可以通过吸收和发射光子将动量传递到感兴趣的原子/离子，进而通过电子-核相互作用传递到原子/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希望的，并被称为“超极化”。该偏振器设施位于TRIUMF的同位素分离器和加速器设施中，是世界上少数几个能够提供短寿命放射性原子核的高度核自旋极化光束的设施之一。这一设施为研究材料性质、生化过程、核结构和基本对称性开辟了独特的途径。随着用户群体的需求不断增长，作为TRIUMF 20年计划的一部分，用户站的重大扩建正在筹备中。这项申请寻求为HQP培训提供资金支持，以便为新出现的研究制定各种同位素的核自旋控制计划和技术。短期目标是开发实用的方案来极化230,232Ac和58，74Cu，因为它们在阿尔茨海默病和癌症中有很好的应用前景。由于不同同位素独特的原子性质，如同位素位移(IS)和超精细结构(HFS)，必须对每种同位素进行深入的研究，以建立合适的光泵浦方案。长期目标是开发一种普遍的偏振技术。使用脉冲激光的“腔辅助”光泵浦将被研究。脉冲激光固有的宽带宽可以同时泵浦所有HFS子能级，从而实现不区分不同同位素的IS和HFS的偏振。目前的光泵浦方法使用连续波激光器，因为需要很长的相互作用时间才能达到足够的泵浦周期，直到实现偏振。在脉冲展宽光学腔的辅助下，脉冲激光器的这一局限性得以克服。另一种方法是利用自旋极化的碱-蒸汽混合物作为自旋交换介质，将极化转移到原子/离子束，从而将激光系统简化为一个通用的装置。该计划将培训下一代研究人员在激光自旋操纵技术这一不断扩大的跨学科应用中，让他们接触到与偏振光束用户的合作，并推动研发高效和简化的核自旋控制系统，以满足不同科学界的各种核物种需求。