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.     

放射性核束(RIB)的物理前沿

介绍了世界上主要的放射性核束装置,并对当前放射性核束物理研究的前沿方向作了评述．同时,也展望了放射性核束装置的发展趋势．Several Radioactive Ion Beam (RIB) lines are briefly introduced in this paper, and the main frontier fields of RIB physics are reviewed.In the last section,the developing trends of RIB setup are prospected.      

非束缚核9He的实验研究

简要介绍了目前有关非稳定核^9He的实验和理论研究现状．现代壳模型理论计算表明。He的基态自旋宇称为1／2^+，而不是1／2^-，即存在自旋宇称翻转现象．到目前为止，实验上虽然观测到了^9He的几个共振态，但还不能确认其基态的能量和自旋宇称值．利用新的实验技术——逆运动学弹性共振散射，对^9He核进行研究，给出了共振态的自旋宇称可能的取值范围．在ISOL型次级束装置上的实验有望能给出^9He核能级的精确测量．The status of theoretical and experimental investigations on unbound nucleus()~(9)He is briefly introduced. The results of modern shell model suggest that the ground state of~(9)He should be 1/2~(+) instead of 1/2~(- )as expected by the normal shell ordering. Therefore, it means that the parity inversion which was well known in~(11)Be occurs also in~(9)He ground state. Recently, some resonance states were observed in transfer reactions and final-state reaction, but their spin-parities cannot be exact...     

串列加速器放射性次级束流线上的核天体物理反应研究

通过在串列加速器次级束流线上开展反应等的研究,导出天体物理S因子;通过反应的研究,探索核的内部结构.初步得出反应的渐进归一化常数平方为3.5±1.5,表明直接反应的贡献不可忽略.     

放射性次级束流分离器的分离性能

放射性次级束流分离器(HFRS)是强流重离子加速器装置(HIAF)上开展放射性次级物理研究的重要装置。HFRS是飞行时间型(PF)碎片分离器,具有大磁刚度、大接受度、大孔径磁铁以及高动量分辨的特点。HFRS采用B-E-B方法纯化弹核碎裂或裂变反应产生的放射性核素,是开展高精度储存环内实验及环外实验研究的重要工具。主要介绍HFRS分离纯化奇异核的能力,采用MOCADI程序模拟单降能器与双降能器下典型弹核碎裂反应和裂变反应中粒子的鉴别和纯化。模拟结果表明:HFRS具有很好的消色散和聚焦特性,对于弹核碎裂反应中轻核的分离采用单降能器系统即可得到很好的纯化效果;而弹核碎裂反应中重核的分离则需采用双降能器系统才可得到很好的纯化效果;对于裂变反应,由于裂变反应的能散较大,则在采用双降能器系统时也仅仅能得到一定的纯化效果。     

基于HIAF的物理研究(英文)

在2010年,中国科学院近代物理研究所向国家发展和改革委员会建议了重大科技基础设施--强流重离子加速器装置（High Intensity Heavy-ion Accelerator Facility,简称HIAF）。经过一系列评估和论证,HIAF于2015年12月被国家发展改革委立项。HIAF建设地址位于广东省惠州市,计划于2018年年底正式开工建造。HIAF由超导直线加速器、同步增强器、高能放射性束流线、储存环谱仪以及若干实验测量装置构成,总投资约为25亿人民币。依托HIAF,我们将拓展核素存在版图,研发先进实验技术和方法,开展前沿物理研究;同时,开展重离子束应用研究,服务国家经济社会发展。简要介绍拟建的加速器系统、实验测量装置以及相关的物理研究计划。The Institute of Modern Physics, Chinese Academy of Sciences, proposed the Major National Science and Technology Infrastructure Facility named as High Intensity Heavy-ion Accelerator Facility (HIAF) in 2010. After a series of assessments charged by the National Development and Reform Commission of China, HIAF was officially approved by China government in December, 2015. HIAF will be constructed in Huizhou, Guangdong Province, and the groundbreaking ceremony of construction is scheduled around the end in the year of 2018. HIAF is composed of a superconducting Linac, a booster ring, a high-energy radioactive beam line, a storage ring, and a number of experiment setups. The total investment of HIAF is about 2.5 billion Chinese Yuan. The major goals for HIAF are to explore the hitherto unknown territories in nuclear chart, to approach the experimental limits, to open new domains of physics researches in experiments, and to develop new ideas and heavy-ion applications beneficial to the societies. In this paper, the accelerator complex of HIAF is briefly introduced, and the experimental setups and associated physics research program are presented.     

放射性次级束流分离器的分离性能北大核心CSCD

放射性次级束流分离器(HFRS)是强流重离子加速器装置(HIAF)上开展放射性次级物理研究的重要装置。HFRS是飞行时间型(PF)碎片分离器,具有大磁刚度、大接受度、大孔径磁铁以及高动量分辨的特点。HFRS采用Bρ-ΔE-Bρ方法纯化弹核碎裂或裂变反应产生的放射性核素,是开展高精度储存环内实验及环外实验研究的重要工具。主要介绍HFRS分离纯化奇异核的能力,采用MOCADI程序模拟单降能器与双降能器下典型弹核碎裂反应和裂变反应中粒子的鉴别和纯化。模拟结果表明:HFRS具有很好的消色散和聚焦特性,对于弹核碎裂反应中轻核的分离采用单降能器系统即可得到很好的纯化效果;而弹核碎裂反应中重核的分离则需采用双降能器系统才可得到很好的纯化效果;对于裂变反应,由于裂变反应的能散较大,则在采用双降能器系统时也仅仅能得到一定的纯化效果。     

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.     

声空化物理研究和核发射实验的近期进展

简要概述了20世纪20年代起多泡声空化的发现、研究和应用，随后重点介绍了20世纪90年代初实现的稳态单一气泡；由于它的实现，对声空化的实验研究和理论研究迅速取得进展，特别是在对气泡内部的极端条件（高温、高压、高密度）以及对气泡内声致发光的机理研究方面，同时还介绍了我国早在20世纪60年代实现的瞬态单一泡以及近期的一些实验结果。文章最后提到2002年3月美国报道的声空化核辐射实验，这个实验正在激发人们对声空化的更多关注。     

质子治疗的物理特性和工作原理(下)

 在“质子治疗的物理特性和工作原理(上)”中我们介绍了质子本身物理特性和形成治疗用质子流的物理方法。为实现这种质子治疗,必需有一套比常规X和电子直线加速器复杂,而且规模更大的质子治疗系统与装置。质子治疗系统是由许多分系统组使质子束射程再大一些,照射更深的病灶。每次增加一个ΔE,一直增加到E2能量(对应为SOBP的后峰时)才能照射到肿瘤的最深层。这种将质子束变为I(E,t),使能量由E1逐步增加能量步距ΔE直到E2能量的装置,叫能量调制器。由于在最深处肿瘤成,每一个分系统又由许多专用设备,都要涉及专门的技术与学科。     

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.     

放射性核束物理研究中的一些热点问题

文章介绍了放射性核束物理的现状和进展,给出了一些目前热点的研究问题和方向,比如垒下融合反应、费米能区和高能区直接核反应、滴线核性质、非稳定核区的新幻数和新的集体运动模式等.     

加速器质谱技术在核物理与天体物理中的应用

介绍了利用加速器质谱技术在核物理与核天体物理中的应用研究工作．包括放射性核素半衰期的测定、核反应截面的测量、超重元素的寻找、宇宙射线和太阳中微子性质等方面的研究工作.The application work which has been done and can be done in the nuclear physics and nuclear astrophysics using accelerator mass spectrometry is reviewed. The half-life measurement of long-lived radio isotopes, cross section measurement of nuclear reaction, searching for super heavy elements, cosmic study and solar neutrino detection are the main components which have been discussed     

25MeV/u 6He在9Be靶上引起的双中子转移

报道了经仔细设计的150MeV ⁶He+⁹Be实验,并在质心系大角度处测量¹⁰Be和¹¹Be同位素产物的实验数据.鉴别得到相应于单中子转移的371个¹⁰Be事件,同时观测到了相应于双中子转移的5个¹¹Be事件.由此得到相应微分截面分别为(0.11±0.02)mb/sr(θ_cm≈137.4°)和(1.0±0.7)μb/sr(θ_cm≈133.4°),结果表明在所研究的反应体系中,单中子转移截面要比双中子转移截面约大100倍.在⁶He由⁵He-n和α-2n组成的集团模型下,利用零力程扭曲波玻恩近似(DWBA)的计算程序,在数量级上重现了单、双中子转移反应的实验数据     

利用强流ISOL束研究20Na的奇异衰变模式(英文)

北京放射性离子束装置（Beijing Radioactive Ion-beam Facility,BRIF）是基于在线同位素分离器技术的国家大科学平台。在BRIF装置上利用100 MeV的质子束轰击较厚的反应靶产生放射性核素;反应产物经离子源电离和在线分离,在线同位素分离段可引出100~300 keV的放射性核束,质量分辨率达20 000。在基金委科学仪器基础研究专项的支持下,建成了多用途的衰变实验终端,包括束流传输管道、通用靶室、带电粒子和γ探测器、集成电子学和数据获取系统等。利用100 MeV的质子束轰击MgO厚靶产生了流强高达1×105 pps的20Na放射性核束。通过高效率地同时测量β,γ和α,第一次直接观测到20Na非常稀有的β-γ-α衰变模式。Beijing Radioactive Ion-beam Facility(BRIF) has been commissioned as the national Radioactive Ion Beam(RIB) facility based on the Isotope Separator On Line(ISOL) technique since 2016. At BRIF, the radioactive nuclides are produced by the proton beam of 100 MeV bombarding a thick-target, the reaction products diffusing out of the target are ionized by an ion source and delivered to the online mass separator. In addition to the post-accelerated radioactive ion beams, BRIF can provide low-energy ISOL beams of 100 to 300 keV with a mass resolution of 20 000. A general-purpose decay station has been built including the ISOL beam transport line, a conventional reaction chamber, charge-particle and γ detectors with integrated electronics and data acquisition system. An intense 20Na ISOL beam up to 1×105 pps was produced by using the 100 MeV proton beam bombarding a MgO thick target. With high-efficiency measurements of β, γ and α simultaneously, very rare β-γ-α decay mode in 20Na has been directly observed for the first time in the present work.     

宇宙中元素的起源

宇宙中绝大部分锂以及所有比锂重的元素都是通过星体内部核过程产生。文章简要介绍这些核合成过程及其发生的天体物理场所以及重元素起源,深地核天体物理实验等相关前沿研究。     

一类生灭过程及其在核天体物理计算中的应用

研究一类生灭过程,利用矩阵分解技巧求出了生灭过程微分方程的解,并将之应用于核天体物理中太阳系慢中子俘获过程重元丰度计算问题研究,计算结果与天文观测值一致.     

放射性次级束流分离器真空系统的压力分布

放射性次级束流分离器是强流重离子加速器装置中,连接增强器和高精度环形谱仪的束流输运线,用于传输重离子束流以及放射性次级束流。为了满足束流传输的要求,并维持相连增强器和高精度环形谱仪的极高真空,放射性次级束流分离器真空系统的平均压强应低于5×10-7 Pa。因此,需要验证真空系统设计方案的可行性,以及设计方案能否满足要求的压强范围。通过现有的同步储存环CSRm中的真空计监测数据以及软件BOLIDE的模拟结果对比,对真空压力计算软件VAKTRAK的使用方法和计算结果进行验证;采用VAKTRAK模拟计算不同真空参数下（流导、出气率以及泵速）放射性次级束流分离器真空系统的压力分布。根据计算结果,放射性次级束流分离器真空系统的平均压强可以达到1.79×10-7 Pa （H₂）,满足物理实验和工程设计的要求。通过模拟计算结果,放射性次级束流分离器真空系统的设计方案的可行性得到验证,系统设计的真空度满足要求。HIAF Fragment Separator(HFRS) is connected with Booster Ring(BRing) and Spectrometer Ring (SRing) in the HIAF and used to transfer the ion beams and radioactive secondary beams. To satisfy the requirements of beam transmission and maintain the extremely high vacuum of BRing and SRing, the average pressure of HFRS vacuum system should be lower than 5×10-7 Pa. Therefore, the feasibility of the design scheme and whether the design scheme would fulfill the required vacuum range or not should be verified. Based on the measured data on the current sychrontron CSRm and the simulation results of BOLIDE, the calculation results of VAKTRAK are verified and then VAKTRAK is used to calculate the pressure profiles of different parameters(such as the conductance, out-gassing and pumping speed) for HFRS. According to the calculation results, the average pressure of HFRS vacuum system could be 1.79×10-7(H₂) which achieves the required pressure for physics experiments and engineering design. According the calculation results of this paper, the feasibility of the designed HFRS vacuum system has been verified and the design of system satisfies the vacuum requirements.