Article title: Development of a low-background neutron detector array

低本底中子探测器阵列研制

DOI： 10.1007/s41365-022-01030-0

One sentence summary:

一句话概要：

A neutron detector array with exceptionally low background was developed to be used at the China Jinping Underground Laboratory.

用于中国锦屏地下实验室的低本底中子探测器阵列研制。

http://www.nst.sinap.ac.cn/newsDetails/112/26554/en/

The Novelty (What)

创新性（主要内容）

This study has successfully developed a high-efficiency neutron detector array with an exceptionally low background to measure the cross-section of the ¹³C(α,n)¹⁶O reaction at the China Jinping Underground Laboratory (CJPL). Comprising 24 ³He proportional counters embedded in a polyethylene moderator, and shielded with 7% borated polyethylene layer, the neutron background at CJPL was as low as 4.5 counts/h, whereby 1.94 counts/h was attributed to the internal α radioactivity. Remarkably, the angular distribution of the ¹³C(α,n)¹⁶O reaction was proven to be a primary variable affecting the detection efficiency. The detection efficiency of the array for neutrons in the range of 0.1MeV to 4.5 MeV was determined using the ⁵¹V(p, n)⁵¹Cr reaction carried out with the 3 MV tandem accelerator at Sichuan University and Monte Carlo simulations. Future studies can be planned to focus on further improvement of the efficiency accuracy by measuring the angular distribution of ¹³C(α,n)¹⁶O reaction.

本研究成功地研制了一种高效率的低本底中子探测器阵列，用于在中国锦屏地下实验室(CJPL)测量¹³C(α,n)¹⁶O的反应截面。探测器阵列将24 个³He正比计数器嵌入聚乙烯慢化体中，并用7%含硼聚乙烯层屏蔽，在CJPL测量的中子本底低至4.5 counts/h，其中1.94 counts/h是由内部α放射性引起的。¹³C(α,n)¹⁶O反应的角分布是影响中子探测效率的主要因素。利用四川大学的3MV串列加速器开展的⁵¹V(p, n)⁵¹Cr实验和Monte Carlo模拟，测定了该阵列对在0.1～4.5MeV能量范围内中子的探测效率。 通过测量¹³C(α,n)¹⁶O反应的角分布，可以进一步提高探测效率精度。

The Background (Why)

研究背景（主要原因）

Gamow window is the range of energies which defines the optimal energy for reactions at a given temperature in stars. The nuclear cross-section of a nucleus is used to describe the probability that a nuclear reaction will occur. The ¹³C(α,n)¹⁶O reaction is the main neutron source for the slow neutron capture process (s-process) in asymptotic giant branch (AGB) stars, in which the ¹³C(α,n)¹⁶O reaction occurs at the Gamow window spanning from 150 to 230 keV. Hence, it is necessary to precisely measure the cross-section of ¹³C(α,n)¹⁶O reaction in this energy range. A low-background and high detection efficiency neutron detector is the essential equipment to carry out such measurements. This study developed a low-background neutron detector array that exhibited high detection efficiency to address the demands. With such development, advanced studies, including direct cross-section measurements of the key neutron source reactions in stars, can be conducted in the near future.

Gamow窗是一个能量范围，它定义了恒星在给定温度下反应的最佳能量。 原子核的截面用来描述核反应发生的概率。 ¹³C(α,n)¹⁶O反应是渐近巨分支(AGB)星慢中子俘获过程（S过程）的主要中子源，其中¹³C(α,n)¹⁶O反应发生在150~230keV的Gamow窗口。 因此，在此能量范围内精确测量¹³C(α,n)¹⁶O反应的截面是十分必要的。 低本底、高探测效率的中子探测器是进行此类测量的必要设备。 为了满足这一要求，本研究开发了一种低本底中子探测器阵列，该阵列具有较高的探测效率。 有了这种发展，在不久的将来就可以进行更进一步的研究，包括直接测量恒星中关键中子源反应的截面。

The SDG impact (Big Why)

SDG影响力（研究意义）

Low-background neutron detectors play a crucial role in facilitating research related to nuclear astrophysics, neutrino physics, and dark matter. By improving the efficiency and upgrading the technological capability of low background neutron detectors, this study indirectly contributes to the enhancement of scientific research. Additionally, fields involving material science and nuclear reactor technology would also benefit from the perfection of neutron detector technology. Taking into consideration the potential application and expansion of these findings, such innovative attempt aligns well with UNSDG9: Industry, Innovation & Infrastructure.

低本底中子探测器在促进与核天体物理、中微子物理和暗物质有关的研究方面起着至关重要的作用。 通过提高低本底中子探测器的工作效率和技术能力，间接地促进了科学研究的发展。 此外，涉及材料科学和核反应堆技术的领域也将受益于中子探测器技术的完善。 考虑到这些发现的潜在应用和扩展，这种创新尝试与联合国可持续发展大会第九届会议：工业、创新和基础设施非常吻合。

研究课题组

中国科学院近代物理研究所-核天体物理研究室的主要研究方向为依托兰州重离子加速器HIRFL装置、低能强流加速器LEAF，锦屏深地核天体物理实验平台JUNA和北京放射性核素装置BRIF等，开展核天体物理前沿研究工作，包括恒星关键核反应的测量、恒星中弱相互作用衰变率的研究、元素核合成的理论研究以及利用时间投影室开展放射性束物理研究。