RIBLL1终端实验装置

描述了一套HIRFL的放射性核次级束流引起反应测量的实验装置,它由RIB鉴别、测量系统、次级靶控制系统和次级反应产物鉴别、测量系统组成.高增益分组延迟线读出、重心定位PPAC,横向场IC,椭球面镜聚焦、PMT读出、闪烁薄膜时间拾取器,双叠层纵向场阳极分条读出IC,PMT矩阵读出x—y位置灵敏Phoswich闪烁探测器,康普顿抑制HpGeγ探测器等单元是这套装置的基本部件.目前,该装置已安装在兰州重离子加速器RIBLL1终端.性能测试和实验研究正在进行.     

一种基于SiPM的新型起始时间探测器研制

本文介绍了一种新型起始时间探测器的研制。该探测器的灵敏面积为60 mm×60 mm,利用120根直径为1 mm的塑料闪烁光纤分成两层错位紧致排布,且上下相邻的3根光纤作为一个探测单元,每个探测单元均采用硅光电倍增管从双端读出信号。采用90Sr放射源对单根光纤进行了性能测试,结果表明,闪烁光沿着光纤方向的有效传播速度约为17 cm/ns,对应的时间分辨优于600 ps。此外,利用中国科学院近代物理研究所第二条放射性束流线（RIBLL2）提供的240 MeV/u的15N次级束研究了该探测器的性能。束流测试结果表明:该探测器的时间分辨为（150±15）ps,纵向位置分辨为（1.8±0.2）cm,并且结合该探测器以及RIBLL2束流线外靶实验终端上的其他探测器,可以对实验中产生的5 ≤ Z ≤ 8的各种同位素进行非常好的粒子鉴别。     

双维位置灵敏CsI(Tl)探测器

描述了一种双维位置灵敏CsI(Tl)探测器.用3组分α源测量该探测器得到的位置分辨为0.81mm(FWHM),对于69MeV/u ³⁶Ar能量分辨为0.9％(FWHM).在RIBLL的ΔE-E粒子鉴别望远镜中常常作为E探测器.由于CsI(Tl)晶体对不同的粒子的能损-光输出的非线性,需要针对不同离子对CsI探测器作能量-光输出校正曲线.     

拟定中的RIBLL实验装置

建议在兰州放射性束流线（ Ｒ Ｉ Ｂ Ｌ Ｌ）上建设３ 套装置: 直接反应精细测量装置, 用来对放射性束的粒子的运动轨迹逐一进行跟踪, 以及对粒子的电荷态、核电荷数、质量数和能量进行精确跟踪, 从而得到核反应和核结构的准确信息; 磁谱探测系统, 它是由一个二极磁铁和相关真空室组成, 一方面它是一个谱仪系统, 用来分离原始放射性主束和次级反应产物, 进行粒子种类和能量的测量, 另一方面, 还可以用来研究放射性核的电磁矩和基态组态; 奇异衰变的４π探测装置是由５套大面积位置灵敏薄片硅探测器和 Ｃｓ Ｉ（ Ｔｌ）组成的望远镜组, 可覆盖整个探测空间的６０％ ～７０％ ,外加多个塑料中子探测器或 γ探测器, 用来测量奇异核和蒸发余核的关联粒子发射, 寻找和测量奇异的放射性衰变．Radioactive Ion Beam Line in Lanzhou (RIBLL) is able to produce hundreds of radioactive ion beams, by mean of projectile fragmentation. A high performance setup for nuclear direct reaction was promoted to track the radioactive ion, and to measure its charge states, nuclear charge, mass, energy. It benefits precise experiment of both nuclear reaction and nuclear structure. An experimental magnet, composing by dipole magnet and vacuum chamber, should be used as magnetic spectrometer to ...     

TOFr在STAR实验中的标定方法

基于多气隙电阻板室(MRPC)的STAR飞行时间探测器的一个板条的原型(TOFr)参加了2003年STAR实验的质子–质子对撞和氘–金对撞的物理运行.利用STAR实验中原有的赝顶点位置探测器(pVPD)和时间投影室(TPC),结合TOFr的时间及幅度信号,并考虑TOFr每个探测单元的尺寸,对影响时间分辨的各种因素进行了修正,实现了对TOFr的标定.实验数据给出的TOFr的本征时间分辨为85ps,在两倍标准方差下,其对π/K及K/p分辨的动量分别达到了1.6GeV/c和3.0GeV/c,大大提高了STAR探测器的粒子鉴别能力.     

高性能PIN-硅探测器的研制及其在高能放射性核束实验中的应用测试

鉴于国内核物理实验对高性能硅探测器有大量需求,而国外对中国进行技术封锁,满足实验需求的高性能探测器不易获得.中国科学院近代物理研究所在原有制备工艺基础上首次采用套刻技术,有效减少了光刻及腐蚀过程造成的Si O2沾污,大幅提高了探测器性能和成品率.本文对采用该工艺研制的300μm厚,有效面积50 mm×50 mm硅探测器进行电学性能测试和在束探测性能测试.探测器在–45 V耗尽电压下,其漏电流小于40 n A,对5 Me V左右的a粒子的能量分辨(σ)约为45 ke V.将该探测器作为能量沉积(ΔE)探测器,利用250 Me V/u的¹¹C放射性束流及其在次级碳靶上的反应产物对探测器进行了探测性能测试.测试结果显示,该探测器对于C元素的电荷数Z的分辨为0.17,与文献中记录的国外生产的同类型探测器的实验数据(Z分辨0.19)相当,可以满足中高能放射性束实验对轻质量区粒子鉴别的要求.     

用于高能轻粒子探测的延迟线PPAC(英文)

气体探测器有成本低廉、制备简单、性能可靠和方便使用等特点。研制了一种5层板结构的延迟线平行板雪崩电离室（PPAC）,用于兰州放射性束流线（RIBLL）上开展的实验。在57.6 MeV/u的6He束流条件下测试了这种探测器对高能轻粒子的适用性,得到了位置分辨为1.8 mm (FWHM), 时间分辨为2.6 ns, 以及可靠的探测效率。The gas detectors have the characteristics of low cost, easy preparation, reliable capability and convenient for use etc. A delay line parallel plate avalanche counter(PPAC) with five plates has been developed for the experiments at Radioactive Ion Beam Line in Lanzhou(RIBLL). The applicability of counter for high energy light ion has been tested with 57.6 MeV/u 6He beam. A position resolution of ~1.8 mm(FWHM) and a timing resolution of ~2.6 ns are achieved. The detection efficiency is reasonable.     

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。     

CsI（Tl）+Si-APD探测器的性能测试

介绍了Si-APD的工作原理并对Si-APD中的暗电流进行了理论分析。基于RIBLL上产生的放射性核束流,使用CsI（Tl）+Si-APD探测器对中能重离子进行了能量测试。测试结果显示,CsI（Tl）+Si-APD探测器测量20 MeV/u的重离子时,可得到3%的能量分辨;同时还发现Si-APD中的暗电流大小以及入射粒子的能量大小都会对探测器的能量分辨产生影响。In this paper, the working principle of Si-APD was introduced and the dark current of Si-APD was analyzed theoretically. The intermediate energy heavy ions, which are produced on the RIBLL(Radioactive Ion Beam Line in Lanzhou), were measured with CsI(Tl)+Si-APD detector. The energy resolution of CsI(Tl)+Si-APD detector is about 3% for heavy ions with energy around 20 MeV/u. It is also found that the energy resolution of detector can be in uenced by the dark current of Si-APD and the energy of incident particles.     

GEM探测器与X射线成像实验

使用2个GEM探测器系统,分别用作增益测量和位置分辨测量.用GEM探测器测量铜靶X射线能谱,能量分辨率为21.5%.8keV的X射线入射双层GEM探测器,实验测量x方向位置分辨为64μm,y方向位置分辨为68μm.将科研成果经过精炼、核心提取,为核与粒子物理学科的本科生开设GEM探测器和X射线成像实验,使学生对高能粒子探测技术、数据获取和处理等有整体的理解.     

质子滴线区新核素25P的鉴别

在兰州放射性束流装置RIBLL上 ,利用磁刚度B_ρ、飞行时间t_TOF和多重望远镜ΔE- E联合探测方法测量了69Me V/u 36Ar轰击Be靶产生的 P同位素碎片的同位素分布,并与 EPAX经验公式的计算结果进行了比较 ,在质子滴线区首次鉴别出了新核素25PThe mass distribution of the phosphor fragments induced by projectile fragmentation reaction of 69 MeV/u 36Ar + 9Be was measured at the projectile fragment separator RIBLL at IMP. The fragment products were identified by determining the magnetic rigidity Bρ , the time of flight t_TOF and their energy loss ΔE . The experimental isotope distribution was compared to the result of the empirical parameterization EPAX. Three events for the new nuclide 25P in the...     

Shell Evolution Study for New Magic Number N =32 via Isochronous Mass Spectrometry

Recent results and progress of mass measurements of neutron-rich nuclei utilizing Isochronous Mass Spectrometry (IMS) based on the HIRFL-CSR complex at Lanzhou are reported. The nuclei of interest were produced through projectile fragmentation of primary 86Kr ions at a realistic energy of 460.65 MeV/u. After in-flight separation by the fragment separator RIBLL2, the fragments were injected and stored in the experimental storage ring CSRe, and their masses were determined from measurements of their revolution times. The re-determined masses were compared and evaluated with other mass measurements, and the impact of these evaluated masses on the shell evolution study is discussed.     

RIBLL终端大面积中子探测器阵列研制方案的理论计算

介绍了一种用于丰中子核研究的RIBLL终端大面积中子探测器阵列的研制.利用Geant4软件包对该探测系统的中子探测效率、时间分辨和位置分布等进行了蒙特卡罗模拟,同时对探测器的cross?talk进行了研究.给出了探测器的设计方案.     

等时性质量谱仪中N=Z核质量测量的方法探索

N=Z核的质量数据对于研究rp-和νp-过程至关重要。此外,N=Z原子核的质量数据将会帮助我们解决与核结构有关的许多关键问题。结合碎片分离器的等时性质谱仪（Isochronous mass spectrometry,IMS）是十分快速有效而且高分辨的质量测量工具。由于N=Z核的m/q值非常接近,目前国际上的储存环质量谱仪CSRe/IMP和ESR/GSI还无法实现对N=Z核运用飞行时间谱进行鉴别,因而无法对它们进行质量测量。在日本理化学研究所的仁科加速器中心新建了专用的等时性质谱仪（IMS）,即稀有放射性同位素储存环"Rare-RI Ring"（R3）,以确定短寿命的放射性原子核的质量,其目标质量相对精度为10-6。R3质谱仪与高分辨的碎片分离器BigRIPS的组合,运用束流线的高分辨的离子鉴别,使得R3上的IMS方法对N=Z核进行质量测量成为可能。本文设计了专用的等时性束流光学设置,模拟了124Xe的主束经过碎裂反应产生的N=Z核在束流线中穿过各焦平面的径迹、能量、速度等信息,同时检验了这些次级束在环内的飞行时间相对于动量的变化关系。模拟的结果表明:当储存环的等时性光学设置在某一个N=Z核时,所有其它N=Z核在环内的回旋时间也与动量弥散无关,说明了这些核也满足等时性条件。基于N=Z核的这种等时性的特点,本文对R3上刻度N=Z核的方法也进行了讨论。     

A pilot experiment for mass measurement at CSRe

A pilot experiment of mass measurement was performed at CSRe with the method of isochronous mass spectrometry. The secondary fragments produced via RIBLL2 with the primary beam of 400 MeV/u 36Ar delivered by CSRm were injected into CSRe. The revolution periods of the stored ions, which depend on the mass-to-charge ratios of the stored ions, were measured with a time-of-flight detector system. The results show that the mass resolution around 8×10-6 for Δm/m is achieved.     

基于RIBLL2的奇特原子核电荷改变截面实验测量进展

电荷半径是原子核最基本的物理观测量之一,反映了原子核内的质子分布。精确的电荷半径测量是研究奇特原子核结构的重要手段。在相对论能区,通过高精度测量原子核的电荷改变截面来提取电荷半径是近年来发展起来的一种新方法,这种方法尤其适于探索产额很低的奇特原子核。自2013年以来,北京航空航天大学-中国科学院近代物理研究所课题组基于兰州第二条次级束流线（RIBLL2）,提出并建成原子核电荷改变截面测量平台,研制了相关的TOF-△E探测器系统,开展了轻核区二十余个原子核的电荷改变截面的实验测量工作。介绍了实验平台研制情况、初步结果以及下一步计划。Charge radius is one of the most fundamental observables of atomic nuclei, reflecting the proton distributions in nuclei. Their precision measurements have severed as a key tool to study nuclear structure. Recently, a novel method to deduce charge radii has been developed via precise measurements of charge-changing cross sections(CCCS) of exotic nuclei at relativistic energies. This method is in particular suitable for investigation of exotic nuclei with low production yield. In 2013, we proposed to make such measurements for exotic nuclei lighter than oxygen based on the RIBLL2 beam line. Since then, the TOF-△E detector system for particleidentification(PID) and the CCCS platform have been constructed, continuously optimized and tested. So far CCCS measurements on a carbon target have been performed for more than 20 isotopes. In this contribution, we will introduce the progress of detector development, the progress in PID, and our experimental progress and plan.     

Technical Improvements in the Experiment of Isochronous Mass Measurement of 58Ni Projectile Fragments

 The combination of in-flight fragment separator and the isochronous mass spectrometry(IMS) in storage rings have been proven to be a powerful tool for the precision mass measurements of shortlived exotic nuclei. In IMS, the mass-over-charge ratio is only related to the revolution period of stored ions, and the relative mass resolution can reach up to the order of 10−6. However, the instability of the magnetic field of storage ring deteriorates the resolution of revolution period, making it very difficult to distinguish the ions with very close mass-over-charge ratio via their revolution periods. To improve the resolution of revolution periods, a new method of weighted shift correction (WSC) has been developed to accurately correct the influence of the magnetic field instabilities in the isochronous mass measurements of 58Ni projectile fragments. By using the new method, the influence of unstable magnetic fields can be greatly reduced, and the mass resolution can be improved by a factor up to 1.7. Moreover, for the ions that still cannot be distinguished after correcting the magnetic field instabilities, we developed a new method of pulse height analysis for particle identification. By analyzing the mean pulse amplitude of each ion from the timing detector, the stored ions with close mass-over-charge ratios but different charge states such as 34Ar and 51Co can be identified, and thus the mass of 51Co can be determined. The charge-resolved IMS may be helpful in the future experiments of isochronous mass measurement even for N =Z nuclei.     

sd壳层极丰质子核的β延迟衰变谱学

远离β稳定线原子核的结构是当前核物理领域的一个前沿热点。β衰变谱学是研究核结构的重要方法，尤其适用于低产额的滴线核。本文回顾了近年来在RIBLL1装置上开展的sd壳区极丰质子核β延迟衰变谱学的实验研究。该工作获得了15个原子核精确的半衰期、衰变子核的质量、β延迟的质子和双质子发射以及$\gamma $跃迁的能谱、分支比和比较半衰期等数据，并重建了衰变纲图，大大丰富了此区域内质子滴线附近原子核的衰变谱学信息。还介绍了探测器阵列和实验方法，概括了所研究核的衰变性质和半衰期等。特别地，对几个典型核，20Mg和22Si以及26P和27S的衰变性质进行了阐述。此外，对相关话题，如三体力、镜像核衰变不对称性、与银河系中26Al超丰问题相关的热核反应率等问题进行了探讨。     

奇异核的实验研究

总结了兰州放射性束实验小组在兰州放射性次级束流线上近几年来利用产生的放射性束流,轰击Si或C等靶子,测量它的反应总截面.并利用经验公式将这些结果归一到相同的能量和靶子,与其相邻的核相比较,发现了⁹C,¹¹Be,¹⁴Be,⁸B,¹⁴B 和¹²N等核素的反应总截面值有奇异增大的现象.利用微观的Glauber模型进行了计算,对有奇异结构的核采用核芯加价核子的密度分布形式,理论计算和实验结果符合得很好,可以给出奇异核的弥散的密度分布.     

核物质中K介子有效质量与非线性效应

分析了核物质标量密度和矢量密度对K介子有效质量的影响．使用非线性σ-ω-ρ模型和相对论平均场理论，给出了核物质标量密度和矢量密度的近似关系曲线，并与线性σ-ω模型的情况进行了比较．利用这一关系，改进了K介子有效质量和核物质密度之间存在的依赖关系，比较不同模型对K介子有效质量的影响．同时也计算了纯中子物质中K介子在不同模型下的有效质量曲线，并与在对称核物质中的情况进行了比较．We investigate the effect of the nuclear vector density ρ_B and the scalar density ρ_S on in-medium kaon and antikaon effective masses. Based on nonlinear σ-ω-ρ model in the relativistic mean-field approximation, we obtained the relation between the two nuclear densities both σ-ω model and σ-ω-ρ model. By (using) the relation, we improve the dependence of in-medium kaon and antikaon effective masses. We also studied the differences of kaon and antikaon effective mass abtained by...