Spectroscopy of Dense Positronium

稠密正电子的光谱学

基本信息

批准号：
2309363
负责人：
Allen Mills
金额：
$ 61.18万
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：
2023
资助国家：
美国
起止时间：
2023-09-01 至 2026-08-31
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2309363&HistoricalAwards=false
关键词：
Spectroscopy Dense Positronium

项目摘要

Positronium is a hydrogen-like atom where, instead of a proton, the positively charged particle is a positron, the anti-particle of the electron. Unlike ordinary hydrogen atoms, positronium atoms spontaneously decay – the electron and positron annihilate and the energy, originally in the form of mass, is converted into gamma rays. The primary work of this research team of faculty, students and a post-doc will be to produce a high-density gas of positronium and cool it to produce the first positronium superfluid, known as a Bose-Einstein condensate (BEC). Such condensates have been studied for other atoms and exhibit a rich range of behaviors, but new experimental techniques will be required to observe Bose condensation in positronium. Scientifically interesting in its own right, if a condensate of positronium can be produced, the fact that positronium atoms decay to gamma rays opens the possibility of creating a gamma ray laser. Positronium in sufficient quantities and at low temperatures 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 therefore to obtain evidence for this stimulated annihilation to open the way for the first highly penetrating annihilation gamma ray lasers. Students will be involved in all aspects of this research and will learn important laboratory techniques widely applicable in physics. Besides the scientific interest in the phenomena, long term possible benefits from a gamma ray laser 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 principal 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 thermalize 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.

正电子是一种类似氢的原子，带正电荷的粒子代替质子为正，是电子的抗颗粒。与普通的氢原子不同，阳性原子在赞助的衰减中 - 电子和阳性歼灭，最初以质量形式的能量转化为γ射线。该研究团队，教师，学生和演出后的主要工作将是产生高密度的阳性气体并冷却其以产生第一个阳性超氟，称为Bose-Einstein冷凝水（BEC）。已经研究了此类冷凝物的其他原子并暴露了丰富的行为，但是需要新的实验技术才能观察阳性中的Bose凝结。如果可以产生阳性的凝结，则在科学上很有趣，这一事实是，阳性原子向伽玛射线腐烂的事实打开了产生伽玛射线激光器的可能性。预计足够数量和低温下的正电子见证了刺激的歼灭，其中一种歼灭伽玛射线光子诱导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。因此，该项目的第二个目标是获得这种刺激的an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。学生将参与这项研究的各个方面，并将学习广泛适用于物理的重要实验室技术。除了对该现象的科学兴趣外，伽玛射线激光器的长期可能受益还包括对射线照相和辐射疗法的医疗应用，高功率伽马射线梁的防御和其他用途，以及熔融熔光激光点火的可能性，用于清洁，低成本的发电厂。该项目的主要目标是（1）产生和观察阳性阳性的Bose-Einstein冷凝物和（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极光束和磁陷阱系统，该系统产生约1亿个30％自旋偏振阳性的纳秒脉冲。这些阳性将从陷阱的狭窄磁场中提取，并在薄金属膜上聚焦在200微米的斑点上，该薄膜有效地发出缓慢的电势。这些将被加速并聚焦到5微米斑点上，上面含有腔的靶标，其中将形成高密度阳性并热温度下降到低温。正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达到所需的高正密度和10 K左右的足够冷的正温度。在制造了第一个正阳性bose-内施泰因冷凝物之后，将搜索其刺激其an灭伽玛射线的刺激发射。除了实现第一个伽马射线激光器的生产外，这项工作还将为涉及高密度正电子的其他主题开辟道路，包括首次生产和阳性的研究（两个阳性和一个电子的结合状态），形成正原子激光束的形成，以及在超级传统中造成的阳性型螺旋式构成型螺旋状的螺旋，并构成了超级构成的高度构成型号。使用基金会的智力优点和更广泛的影响标准，认为通过评估被认为是宝贵的支持。