Spectroscopy of Dense Positronium

稠密正电子的光谱学

• 批准号: 2011836
• 负责人: Allen Mills
• 金额: $ 57.94万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2011836&HistoricalAwards=false
• 关键词: Spectroscopy; Dense; Positronium

Positronium is an exotic hydrogen-like atom composed of one ordinary electron (the light mass negatively charged components of all ordinary matter) bound to one positively charged electron, the antimatter twin of the electron, called a positron. Positronium has a brief existence which terminates in its annihilation into a burst of two or three gamma ray photons (very high energy particles of light). The primary goal of the project is to produce a high density positronium gas and cool it to produce the first positronium "superfluid", known as a Bose-Einstein condensate. This substance is predicted to exhibit stimulated annihilation, in which one annihilation gamma ray photon induces the emission of others of exactly the same direction and energy, the essential activity required for all types of laser action. The second goal of the project is to obtain evidence for this stimulated annihilation to open the way for the first highly penetrating annihilation gamma ray lasers. Besides the scientific interest in the phenomena, the possible eventual benefits include medical applications to radiography and radiation therapy, defense and other uses of high-power gamma ray beams, and the possibility of gamma ray laser ignition of fusion for clean, low-cost electric power generating plants. The principle goals of the project are to (1) produce and observe a Bose-Einstein condensate of positronium and (2) to obtain evidence for the stimulated emission of its two-photon annihilation radiation. The project will use an existing slow positron beam and magnetic trap system that produces nanosecond pulses of about 100 million 30% spin-polarized positrons. The positrons will be extracted from the confining magnetic field of the trap and focused in a 200 micron diameter spot on a thin metal film that efficiently emits slow positrons. These will be accelerated and focused to a 5 micron spot onto a target containing cavities within which high density positronium will be formed and thermalized to low temperatures. The positronium temperature will be measured as a function of time by the angular correlation of the annihilation photon pairs using an existing detector. The presence of a condensate will be inferred from its sub-thermal apparent temperature. Various cavity geometries will be used to achieve the required high positronium densities and sufficiently cold positronium temperatures around 10 K. Having made the first positronium Bose-Einstein condensate, a search will be made for the stimulated emission of its annihilation gamma rays. Besides enabling the production of the first gamma ray lasers, this work will open the way for other topics involving high density positrons, including the first production and studies of the positronium positive ion (the bound state of two positrons and one electron), formation of a positronium atom laser beam, and production of Bose-Einstein condensed positronium bubbles in superfluid helium-4.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

正电子是一种异国氢原子，由一个普通电子（所有普通物质的光质量负电荷的成分）组成，结合到一个带正电荷的电子，即电子的抗药物双胞胎，称为正电子，称为正电子。正电子的短暂存在，它在其an灭中终止于两到三个伽玛射线光子（光能颗粒非常高）的爆发。该项目的主要目的是产生高密度的阳性气体并冷却以产生第一个阳性“超氟”，称为Bose-Einstein冷凝物。预计该物质会表现出刺激的歼灭，其中一种an灭伽玛射线光子诱导了其他完全相同的方向和能量的发射，这是所有类型的激光作用所需的基本活动。该项目的第二个目标是获得这种刺激的歼灭的证据，以为第一个高度穿透性歼灭伽玛射线激光打开道路。除了对该现象的科学兴趣外，最终可能的好处还包括射线照相和放射疗法的医学应用，高功率伽马射线光束的防御和其他用途，以及对清洁，低成本电力发电厂融合的伽马射线激光点火的可能性。该项目的主要目标是（1）产生和观察正电子的玻色网凝结物和（2）获得刺激其两光子歼灭辐射的刺激发射的证据。该项目将使用现有的慢速束和磁性陷阱系统，该系统产生约1亿个30％自旋偏振正极的纳秒脉冲。正电子将从陷阱的狭窄磁场中提取，并在薄金属膜上聚焦于200微米的斑点，该薄膜有效地发出缓慢的正音量。这些将被加速并聚焦到5微米的斑点上，上面含有腔的目标，其中将形成高密度的正电子并热到低温。正电子温度将通过使用现有检测器的an灭光子对的角相关性来测量时间的函数。凝结物的存在将从其亚热的表观温度中推断出来。各种空腔几何形状将用于实现所需的高正环密度和10 K左右的足够冷正环温度。在制造了第一个阳性Bose-Einstein冷凝物后，将进行搜索，以搜索其刺激其an灭伽玛射线的刺激发射。 Besides enabling the production of the first gamma ray lasers, this work will open the way for other topics involving high density positrons, including the first production and studies of the positronium positive ion (the bound state of two positrons and one electron), formation of a positronium atom laser beam, and production of Bose-Einstein condensed positronium bubbles in superfluid helium-4.This award reflects NSF的法定使命，并使用基金会的知识分子优点和更广泛的影响审查标准来评估值得支持。

项目成果

Early-time behavior of quantum subharmonic generation

量子次谐波产生的早期行为

• DOI: 10.1103/physreva.103.043518
• 发表时间: 2021
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Choi, Yunjin;Hemmerling, Boerge;Tsai, Shan-Wen;Mills, Allen P.
• 通讯作者: Mills, Allen P.

Conservation of longitudinal spin polarization of positrons emitted from a thin Ni(100) foil

薄 Ni(100) 箔发射的正电子的纵向自旋极化守恒

• DOI: 10.1103/physreva.107.062809
• 发表时间: 2023
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Cecchini, G. G.;Greaves, R. G.;Mills, A. P.
• 通讯作者: Mills, A. P.

Positron pair interactions in a nearly free-electron metal

近自由电子金属中的正电子对相互作用

• DOI: 10.1140/epjd/s10053-022-00406-6
• 发表时间: 2022
• 期刊: The European Physical Journal D
• 作者: Mills, Jr., Allen Paine;Fuentes-Garcia, Melina
• 通讯作者: Fuentes-Garcia, Melina

Conditions for obtaining positronium Bose–Einstein condensation in a micron-sized cavity

在微米级空腔中获得正电子玻色爱因斯坦凝聚的条件

• DOI: 10.1140/epjd/s10053-022-00427-1
• 发表时间: 2022
• 期刊: The European Physical Journal D
• 作者: Asaro, Marcus X.;Herrera, Steven;Fuentes-Garcia, Melina;Cecchini, Gabriel G.;Membreno, Erick E.;Greaves, Rod G.;Mills, Jr., Allen P.
• 通讯作者: Mills, Jr., Allen P.