兰州320kV高压平台低能核天体物理实验研究进展(英文)

在低温核天体物理环境下,如静态核稳定燃烧阶段的核反应都发生较低的能区,其伽莫夫窗口内的核反应截面非常小,这就需要加速器提供较强束流才能完成核反应截面的直接测量。最近在中国科学院近代物理的320 kV高压平台上建立了低能核天体物理实验室以及相应的研究平台。驱动该平台的是一个14.5 GHz的永磁铁型ECR离子源,它能够提供非常强的束流离子。对于质子和氦离子,离子源出口的最大流强可以达到100 eμA,在实验终端上可以获得大约30 eμA的流强。基于此强流加速器装置,我们建立了核天体物理实验测量装置,包括靶室以及带电粒子和伽玛射线探测器等设备。利用已知的核反应对探测器性能和实验方法进行了一系列测试。同时,展示了近年来取得的一些主要实验结果。最后,对该平台上开展工作的前景进行了展望,并指出基于该地面装置的低能核反应研究所积累的技术及经验对于我国锦屏深地核天体物理JUNA项目的重要意义。For the hydrostatic stable burning in stars, the Gamow window is well below the Coulomb barriers for the charged-particle-induced nuclear reaction involved. Such nuclear reaction occurs through the quantum-mechanics tunneling effect, and its cross section drops rapidly approaching the Gamow window. An accelerator which can provide intense beam current is thus required to directly measure the reactions at low energies. An experimental setup for low-energy nuclear astrophysics studies has been recently established at a 320 kV high-voltage platform of the Institute of Modern Physics (IMP), Lanzhou, China. The driver machine of this platform is a very strong ECR ion source employing all-permanent magnets, which can typically supply up to about 100 eμA proton, alpha and many other heavy ions, and ultimately about 30 eμA currents can be achieved at the experimental terminal. The experimental setup includes a target chamber, and the charged-particle and γ-ray HPGe detectors. This work describes the setup established, characteristics of detectors, methodologies, and test results of several reactions with known cross sections. Furthermore, some important results published are shown briefly. We believe that the experimental technologies developed and experiences accumulated at this above-ground platform will be extremely helpful for the Jinping Underground Nuclear Astrophysics laboratory (JUNA) project in China.     

在深地仰望星空——锦屏深地核天体物理实验

人类自诞生以来,对穹顶之上星空的探索从未停止。在古代社会,好奇心便开始驱使着人们去观察和记录星空中的天文事件。然而受认知水平的局限,这个时期的天文观测更多伴随着浓厚的神秘主义色彩。     

我国核天体物理前沿研究进展

核天体物理是研究微观世界的核物理与研究宏观世界的天体物理融合形成的交叉学科,其主要研究目标是:宇宙中各种化学元素核合成的过程、时间、物理环境、天体场所及丰度分布;核反应（包括带电粒子、中子、光子及中微子引起的反应、β衰变及电子俘获）如何控制恒星的演化过程和结局。近十多年来获得的大量实验和理论研究使核天体物理研究进入了一个蓬勃发展的新阶段。文章总结了以兰州重离子加速器、北京串列加速器和国家天文台为基础,结合国际合作,在核天体物理研究领域对直接测量、间接测量、衰变测量、质量测量、理论计算、网络计算、天文观测等关键科学问题进行的研究进展。也展望了核天体物理的关键科学问题,这些关键问题包括:（1）在地面实验室、尤其是地下实验室开展天体物理能区重要热核反应截面的直接测量;（2）高能区带电粒子反应截面向天体物理能区的合理外推;（3）恒星平稳核燃烧阶段和爆发性天体事件中关键核反应截面的间接测量;（4）爆发性天体事件中所涉及的大量远离稳定线核素的质量、衰变特性和共振态性质的研究;（5）建立并不断完善核天体物理数据库,发展网络模拟程序,系统研究元素核合成的天体场所、丰度分布;（6）宇宙中铁以上元素的来源之谜。Nuclear astrophysics is an interdisciplinary research field. It composes of nuclear physics, which studies micro phenomena, and astrophysics which studies macroscopic phenomena in our world. The main research goals of nuclear astrophysics are:(1) how, when and where chemical elements are synthesized and what is their final abundance distribution in the universe; (2) how nuclear processes (reactions induced by charged particles, neutrons, photons and neutrinos, beta decays and electron capture processes) determine the evolution and the ultimate fate of stars. At present, nuclear astrophysics has been developed into a new prosperous stage with a huge number of experimental and theoretical progresses. This paper summarized the current progress of nuclear astrophysics in China, in the subfiels of direct and indirect measurement of key reactions, measurement of mass and decay, as well as the theoretical calculation and network simulation. In present paper, the prospects to solve the key scientific nuclear astrophysics problems are represented. These key problems include (1) direct measurement of important reactions at astrophysical energies in the laboratory on the earth surface and in the underground laboratory; (2)extrapolation of cross sections at higher energies for the reactions induced by charged particles; (3) indirect measurement of key reactions in the hydrostatic and explosive nuclear processes; (4) study of the mass, the properties of decay and resonant states for the nuclides far from the stability line in explosive astrophysical events; (5) establish and improve the database for nuclear astrophysics, and develop network simulation codes, and systematically study astrophysical sites and abundance distribution of nucleosynthesis; (6) origin of the elements heavier than iron in the universe.     

低能加速器质子束流性质的测量(英文)

中国锦屏地下实验室（CJPL）坐落于四川省锦屏山中,利用水电站修建的隧道建成。由于其本底环境极低,非常适合开展低本底实验测量。一台基于ECR源的400 kV强流加速器将安装在CJPL中,其可以为核天体物理实验提供流强为12 emA的质子束流,6 emA的He+束流和2.5 emA的He2+束流。拟通过非共振反应12C（p,γ）13N以及一系列的共振反应27Al（p,γ）28Si等,对加速器的束流能量进行精确刻度,对束流的能量展宽以及长期稳定性进行测量。由于该加速器正在中国原子能科学研究院进行地面调试,我们利用中国科学院近代物理研究所的320 kV研究平台,进行了12C（p,γ）13N和27Al（p,γ）28Si反应的测试实验。测量结果表明,在质子束流能量为224 keV时,束流的能量展宽约为1.0 keV,束流能量在连续4小时的测量期间,其晃动幅度远小于±200 eV。China JinPing underground Laboratory (CJPL) was established inside the tunnels piercing Jinping Mountain in Sichuan Province, China, which can provide an ideal environment for low background experiment. A new 400 kV accelerator, with high current based on an ECR source, will be placed at this underground laboratory for nuclear astrophysics experiment. The beam characteristics of this accelerator, like absolute energy, energy spread, and long-term energy stability, will be determined by several wellknown resonance and non-resonance reactions. Due to the new accelerator still being under construction, the resonance reaction of 27Al(p, γ)28Si and non-resonance 12C(p, γ)13N were studied at the 320 kV highvoltage platform in Institute Modern Physics of CAS in Lanzhou. The energy spread of proton beam is about 1.0 keV at proton energy E_p=224 keV and the long-term energy stability of proton beam is much better than 200 eV during 4 hours measurement.     

高能天体物理前沿鸟瞰 (上)

 很容易确定天体物理诞生的日子,也很容易确定现代宇宙学诞生的日子.前者由基尔霍夫的太阳光谱观测确定,后者由爱因斯坦发表第一个宇宙解确定。但是,很难确定高能天体物理诞生的日子.也许可以作为高能天体物理诞生标志的是巴德和兹威基于1934年发表的一篇论文,题目为《超新星和宇宙线》.     

高能天体物理前沿鸟瞰(下)

 中子星的质量有一个上限,其值大约在3个太阳质量左右.质量大于上限的星,引力坍缩后不能形成稳定的中子星,而将形成黑洞.黑洞是引力非常强的空间范围,其中的光也不能逃离黑洞.黑洞的可能存在,象中子星一样,也是三十年代就预言了.同样,它也是直到六十年代才受到重视,成为天体物理中最常见的名词之一.     

关键天体反应18Ne(α, p)21Na的实验研究

在X 射线暴高温高密度的环境中,18Ne( α, p)21Na 很可能是由热CNO 循环突破到rp 过程的一个重要反应。到目前为止,人们测得的反应率还存在很大的不确定性。实验中用CRIB(CNS RadioactiveIon Beam separator) 提供的21Na 放射性束轰击8.8 mg/cm2 的聚乙烯厚靶,利用放置在θlab = 14°,0°,14° 处的3 套硅条探测器望远镜阵列对反冲轻粒子进行鉴别和测量,测得在一段能区(Ex = 5:5  9:2MeV) 内21Na(p, p)21Na 的激发函数。通过对21Na(p, p) 共振弹性散射截面进行R矩阵拟合,得到了22Mg共振能级的自旋宇称以及质子宽度等信息,从而为计算18Ne( α,, p)21Na 反应率提供了实验参数。The 18Ne(α ,p)21Na reaction is thought to be one of the key breakout reaction from the hot CNO cycle to the rp-process in X-ray bursts. Over stellartemperatures achieved in XRBs, this rate has not been sufficiently determined.The experiment was performed using CRIB (CNS Radioactive Ion Beam separator) at the Center for Nuclear Study (CNS) of the University of Tokyo. An 89 MeV 21Na radioactive ion beam was produced and bombarded an 8.8 mg/cm2 thick polyethylene target. The recoiled light particles were detected with three Micron silicon ΔE-E telescopes centered at angles of θlab = 0°; +14° and 14°with respect to the beam direction, respectively. The 21Na+p elastic-scattering excitation functions were reconstructed with a thick-target method over energies Ex = 5:5  9:2 MeV. The resonance parameters have been determined through an R-matrix analysis,which will be used to evaluate the 18Ne( α, p)21Na reaction rate.     

原子能院的核天体物理研究和串列升级工程进展(英文)

在北京串列实验室建立了次级束流实验装置 ,用于放射性核束物理和核天体物理研究 .先后开展了7Be(d ,n) 8B ,11C(d ,n) 12 N ,8Li(d ,p) 9Li和6 He(p ,n) 6 Li核天体物理重要反应的研究 .介绍了串列加速器升级工程的进展情况 .该工程在现有串列加速器的基础上 ,将建立 10 0MeV/ 2 0 0 μA的质子回旋加速器、在线同位素分离器和超导加速段 .在此装置上 ,将可以产生质量数最高为 12 0 ,强度最高为 10 9particles/s的放射性束流 . A secondary beam line (GIRAFFE) at the Beijing Tandem accelerator lab was constructed for yielding low energy secondary beams. The current progress on the study of nuclear astrophysics and nuclear structure is presented. Up to now, We have carried out measurement of~(7)Be(d, n)~( 8)B,~(11)C(d, n)~(12)N,~(8)Li(d, p)~(9)Li, and~(6)He(p, n)~(6)Li reactions. The proposed Beijing radioactive nuclear beam facility (BRIF ) and its current R&D progress are briefly introduced. This facility is based on...     

25Mg(p, γ)26Al实验研究进展

长寿命放射性核素26Al是星际介质、$\gamma$射线天文学和太阳系形成研究中最重要的核素之一。最可能合成26Al的三种天体场所都与25Mg(${\rm p},\,{\rm{\gamma }}$)26Al反应相关,因此精确测量其近阈能级的共振强度和天体物理反应率对人们认识宇宙26Al的来源具有重要意义。本文回顾了25Mg(${\rm p},\,{\rm{\gamma }}$)26Al反应的实验研究方法和最新研究进展,特别是介绍了我国对该反应的间接测量实验以及直接实验测量计划。当前的间接测量结果提升了25Mg(${\rm p},\,{\rm{\gamma }}$)26Al天体物理反应率的精度,也可以帮助我们估算直接测量的产额,并优化深地直接测量的实验设计。高能点的直接测量结果与国际上其它实验结果在误差范围内符合很好,表明本项目研制的探测装置工作状态良好,能够胜任锦屏深地核天体物理实验研究。     

Progress of Jinping Underground laboratory for Nuclear Astrophysics (JUNA)

Jinping Underground laboratory for Nuclear Astrophysics(JUNA) will take the advantage of the ultra-low background of CJPL lab and high current accelerator based on an ECR source and a highly sensitive detector to directly study for the first time a number of crucial reactions occurring at their relevant stellar energies during the evolution of hydrostatic stars. In its first phase, JUNA aims at the direct measurements of~(25)Mg(p,γ)~(26)Al,~(19)F(p,α)~(16)O,~(13)C(α,n)~(16)O and ~(12)C(α,γ)~(16)O reactions. The experimental setup,which includes an accelerator system with high stability and high intensity, a detector system, and a shielding material with low background, will be established during the above research. The current progress of JUNA will be given.     

用于核天体物理实验的活性靶时间投影室

发生在中子星壳层内的丰中子熔合反应对中子星演化以及X射线超级爆等现象均会产生影响。受限于放射性束流强度和反应机制的复杂性,实验数据极其缺乏,难以有效约束理论模型。基于活性靶技术的时间投影室(Time Projection Chamber,TPC)将工作气体作为反应靶,具备近4$pi$立体角接受度和三维径迹重建能力,能够实现对反应事件的全记录,显著提高了探测效率,大幅降低了熔合反应截面测量对束流强度的要求。我们研制了240路信号读出的TPC,并使用放射性束流16N对探测器进行了测试,探索了该实验方法的可行性和有效性。为了得到更加精确的反应产物径迹,对反应事件做出更好的筛选,进一步发展了1 024路信号读出TPC,并开展了12C+12C库仑位垒附近熔合反应截面测量实验,初步实验结果与已有实验数据符合较好。     

核天体物理实验研究概述

本文简要地评述了宇宙演化核素合成研究的新发展,介绍了核天体物理实验特征和目前及未来的实验装置与实验技术,最后讨论和展望了当前感兴趣的几个核天体物理实验研究的课题。 The current state of nuclear astrophysics has been briefly reviewed. Someexperimental features and some current and future experimental techniques in the field of nuclearastrophysics are introduced. Finally, a synopsis of some key topies with experimental interest isdescribed.     

Nuclear Astrophysics from View Point of Few-Body Problems

Few-body systems provide very useful tools to solve different problems for nuclear astrophysics. This is the case of indirect techniques, developed to overcome some of the limits of direct measurements at astrophysical energies. Here the Coulomb dissociation, the asymptotic normalization coefficient and the Trojan Horse method are discussed.     

The History and Impact of the CNO Cycles in Nuclear Astrophysics

The carbon cycle, or Bethe-Weizsäcker cycle, plays an important role in astrophysics as one of the most important energy sources for quiescent and explosive hydrogen burning in stars. This paper presents the intellectual and historical background of the idea of the correlation between stellar energy production and the synthesis of the chemical elements in stars on the example of this cycle. In particular, it addresses the contributions of Carl Friedrich von Weizsäcker and Hans Bethe, who provided the first predictions of the carbon cycle. Further, the experimental verification of the predicted process as it developed over the following decades is discussed, as well as the extension of the initial carbon cycle to the carbon-nitrogen-oxygen (CNO) multi-cycles and the hot CNO cycles. This development emerged from the detailed experimental studies of the associated nuclear reactions over more than seven decades. Finally, the impact of the experimental and theoretical results on our present understanding of hydrogen burning in different stellar environments is presented, as well as the impact on our understanding of the chemical evolution of our universe.     

Measurement of muon-induced neutron yield at the China Jinping Underground Laboratory

Solar, terrestrial, and supernova neutrino experiments are subject to muon-induced radioactive background. The China Jinping Underground Laboratory (CJPL), with its unique advantage of a 2400 m rock coverage and long distance from nuclear power plants, is ideal for MeV-scale neutrino experiments. Using a 1-ton prototype detector of the Jinping Neutrino Experiment (JNE), we detected 343 high-energy cosmic-ray muons and (7.86\begin{document}$ \pm $\end{document}3.97) muon-induced neutrons from an 820.28-day dataset at the first phase of CJPL (CJPL-I). Based on the muon-induced neutrons, we measured the corresponding muon-induced neutron yield in a liquid scintillator to be \begin{document}$(3.44 \pm 1.86_{\rm stat.}\pm $\end{document}\begin{document}$ 0.76_{\rm syst.})\times 10^{-4}$\end{document} μ^?1g^?1cm² at an average muon energy of 340 GeV. We provided the first study for such neutron background at CJPL. A global fit including this measurement shows a power-law coefficient of (0.75\begin{document}$ \pm $\end{document}0.02) for the dependence of the neutron yield at the liquid scintillator on muon energy.     

AMS在核物理与天体物理研究中的应用

加速器质谱学方法在核物理与天体物理研究中有重要应用.主要介绍了该方法在寻找泡利不相容原理的违背事例和超新星活动研究等工作中的应用. As an ultra high sensitive analyzing method, accelerator mass spectrometry is playing an important role in the studies of nuclear physics and astrophysics. In this article, accelerator mass spectrometry (AMS) applications in searching for violation of Pauli exclusion principle and study on supernovae are discussed as examples.