Towards nuclear astrophysics measurements at the NEW Birmingham High-Flux Accelerator-Driven Neutron Facility (HF-ADNeF)

在新伯明翰高通量加速器驱动中子设施（HF-ADNeF）进行核天体物理测量

• 批准号: ST/W006073/1
• 负责人: Carl Wheldon
• 金额: $ 24.37万
• 依托单位: University of Birmingham
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FW006073%2F1
• 关键词: Towards; nuclear; astrophysics; measurements; NEW

Neutrons are uncharged particles that exist in the tightly bound nucleus at the core of atoms. Together with charged protons they make up most of the mass that we see around us. In the Universe, most of the elements that we find on earth have been produced in stars by a combination of neutron capture and subsequent beta decay. These processes convert light elements to heavier elements in giants stars - those many times the size of our sun. In such environments there can be billions of neutrons passing through every square centimetre every second. Although this sounds like a huge number, the probability of elements capturing neutrons, even in such an environment, is quite low and so it is referred to as the slow-neutron capture process - or s-process for short. There are many things we don't understand about the s-process, for example, details about where the process splits into several branches and the precise rates of the beta decay process etc. These gaps in our knowledge mean we don't have a full understanding of how the elements were made (nucleosynthesis) and what the abundances of each element in giant stars were - material from which the earth was formed. To find out, we can study the s-process in the laboratory to measure the missing information. However, because neutrons are uncharged, it is not possible to accelerate them using electric and magnetic fields. This makes beams of neutrons for research more difficult to produce. However, at Birmingham we are building a next-generation neutron source that generates neutrons by bombarding a lithium target with protons. This machine will come on line in early 2022. The energies of the neutrons produced will closely mimic those found in giant stars. Furthermore, the intensity of the new neutron beam will one of the highest of its kind in the world (capable of producing more than a 10 trillion neutrons per second). This unique combination of energy and intensity makes the study of the s-process possible. To facilitate these studies, this proposal is to test the feasibility of building a detector end-station that is sufficiently well shielded that the detectors won't be damaged by the neutron beam. The added complexity is that the neutron beam needs to be focused on to a reaction target without diminishing the intensity of the beam significantly. The reactions between the target and neutrons could then be observed and measured.To fully exploit this rare opportunity for exploring the potential of making a UK laboratory for astrophysics requires undertaking this feasibility study when the machine is installed.

中子是不带电的粒子，存在于原子核的紧密结合中。它们和带电的质子一起构成了我们周围看到的大部分质量。在宇宙中，我们在地球上发现的大多数元素都是通过中子捕获和随后的β衰变在恒星中产生的。这些过程将轻元素转化为巨星中的重元素-这些巨星的大小是我们太阳的许多倍。在这样的环境中，每秒每平方厘米可能有数十亿个中子通过。虽然这听起来是一个巨大的数字，但即使在这样的环境中，元素捕获中子的概率也很低，因此它被称为慢中子捕获过程-或简称为s过程。关于s过程，我们有很多不了解的地方，例如，关于过程在哪里分裂成几个分支的细节，以及β衰变过程的精确速率等，这些知识上的差距意味着我们对元素是如何形成的（核合成）以及巨恒星中每种元素的丰度是什么-地球形成的材料。为了找到答案，我们可以在实验室中研究s过程来测量缺失的信息。然而，由于中子是不带电的，因此不可能使用电场和磁场来加速它们。这使得用于研究的中子束更难产生。然而，在伯明翰，我们正在建造下一代中子源，它通过用质子轰击锂靶来产生中子。这台机器将于2022年初上线。产生的中子的能量将非常接近于在巨星中发现的能量。此外，新中子束的强度将是世界上同类中子束中最高的（每秒能够产生超过10万亿个中子）。这种能量和强度的独特组合使得研究s过程成为可能。为了促进这些研究，本建议是为了测试建造一个探测器终端站的可行性，该终端站具有足够好的屏蔽，使探测器不会被中子束损坏。增加的复杂性是中子束需要聚焦到反应靶上而不显著减小束的强度。为了充分利用这个难得的机会，探索在英国建立天体物理实验室的潜力，需要在机器安装时进行这项可行性研究。