MRI: Development of a Rubidium Spin Filter as a Source of Polarized Electrons

MRI：开发铷旋转滤波器作为极化电子源

• 批准号: 0821385
• 负责人: Timothy Gay
• 金额: $ 28.5万
• 依托单位: University of Nebraska-Lincoln
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0821385&HistoricalAwards=false
• 关键词: MRI; Development; Rubidium; Spin; Filter

A team of University of Nebraska-Lincoln physicists will develop a novel, "turn-key" polarized electron beam source. The use of polarized electrons is widespread in physics, from probing the spin-structure of nucleons and nuclei to studies of magnetic domain structure and the spin-dependence of atomic collisions. State-of-the-art polarized electron sources are based on GaAs photocathode technology. While this source has significant advantages over other available methods, it is very difficult to operate. In university settings, the learning curve for reliable operation by a graduate student of these sources is routinely measured in months or years, not weeks. At accelerator facilities such as CEBAF or MAMI, dedicated staffs of technicians and Ph.D.s maintain and operate these sources. The polarized electron source to be developed is based on new technology: the optically-pumped rubidium spin filter. In this scheme, unpolarized electrons diffuse under the action of an electric field through a target of optically-pumped Rb and a buffer gas. As the electrons collide with the spin-polarized Rb, they become polarized via exchange collisions. They are then extracted and formed into a beam. A proof-of-principle experiment has already demonstrated this technique. Such a source is expected make many current experiments easier, and it would also extend the range and quality of the data they produce. More importantly, it may lead groups with no current expertise in polarized electron technology to consider new types of experiments. As an example, spin-polarized low-energy microscopy (SPLEEM), a powerful technology for the study of magnetic surfaces, is currently used in only a few labs around the world due to the operational complexity of the GaAs sources it employs. A spin filter would make such technology much more accessible to the general condensed matter community. Students and postdocs working on the development of the Rb spin filter will receive training in state-of-the-art optical instrumentation and technology. The key element of this source is optical pumping, which is an enabling technology for other fields, such as nuclear physics and medicine. The faculty involved with this project have been very effective at integrating undergraduate students into their research programs. They have made a particularly strong effort to hire and mentor women and underrepresented minorities early in the academic "pipeline." The results of this instrument development effort will be broadly disseminated through refereed scientific publications, and the potential for commercialization will be evaluated.

内布拉斯加大学林肯分校的一个物理学家小组将开发一种新型的“交钥匙”极化电子束源。极化电子在物理学中的应用很广泛，从探测核子和原子核的自旋结构到研究磁畴结构和原子碰撞的自旋依赖性。最先进的极化电子源基于GaAs光电阴极技术。虽然这种来源比其他可用的方法具有显着的优势，但它非常难以操作。在大学环境中，研究生对这些源进行可靠操作的学习曲线通常以月或年为单位，而不是以周为单位。在加速器设施，如CEBAF或MAMI，专门的技术人员和博士工作人员维护和操作这些源。 将开发的极化电子源基于新技术：光泵铷自旋过滤器。在该方案中，未极化的电子在电场的作用下扩散通过光泵Rb和缓冲气体的目标。当电子与自旋极化的Rb碰撞时，它们通过交换碰撞而极化。然后将它们提取并形成梁。一个原理验证实验已经证明了这种技术。这样的来源预计将使目前的许多实验变得更容易，并且还将扩展它们产生的数据的范围和质量。更重要的是，它可能会导致目前在极化电子技术方面没有专业知识的团体考虑新类型的实验。例如，自旋极化低能显微镜（SPLEEM）是一种用于研究磁性表面的强大技术，由于其采用的GaAs源的操作复杂性，目前仅在世界各地的少数实验室中使用。自旋过滤器将使这种技术更容易为一般凝聚态社区所用。 从事Rb自旋过滤器开发的学生和博士后将接受最先进的光学仪器和技术的培训。这种光源的关键元件是光泵浦，这是一种使核物理和医学等其他领域成为可能的技术。参与该项目的教师在将本科生融入他们的研究项目方面非常有效。 他们特别努力在学术“管道”的早期雇用和指导妇女和代表性不足的少数民族。“这一仪器开发工作的结果将通过参考科学出版物广泛传播，并将评估商业化的潜力。