2018年 第35卷 第2期
The effect of deformation-dependent shell correction (DDSC) on the emission of prescission neutron (EPN) is studied within a dynamical and statistical model for three isotopes of 209,213,217Fr near the neutron 126 closure-shell. The results show that the fission barriers are enhanced with DDSC, and the increment of 213Fr is almost 2 times those of 209,217Fr, but those saddle points are not changed. Although the enhancement of fission barrier delays nuclear fission, the fission dynamics process is controlled by the competition between thermodynamic driving force (TDF) and nuclear damping, so the deformation-dependence of nuclear dissipation must be considered in order to extract the role of shell correction. The shell correction doesn't alter isotope effect of EPN with OBD nuclear dissipation in the first phase of nuclear fission, but the rule does not been exhibited because that there is abnormal enhancement of TDF using SPS nuclear dissipation. The increment of EPN caused by the rise of fission barrier is countered by the competition between TDF and nuclear damping in the second phase of nuclear fission, hence the effect of EPN cannot exhibit. The effect of DDSC on EPN near the neutron 126 closure-shell is dominated by the rules in the first phase of nuclear fission.
The statistical uncertainties of 15 model parameters in the Weizsäcker-Skyrme(WS4) mass model are investigated with an efficient approach, and the propagated errors in the predicted masses are estimated. The discrepancies between the predicted masses and the experimental data are almost all smaller than the model errors. The most sensitive model parameter which causes the largest statistical error is analyzed for all bound nuclei. We find that the two coefficients of symmetry energy term significantly influence the mass predictions of extremely neutron-rich nuclei. In addition, the parameter uncertainties and statistical errors of the WS4 mass model and the WS* mass model are compared. The uncertainties of model parameter in the WS4 mass model is reduced by 10% ~ 50% compared with the WS* mass model.
天体环境中丰中子核素熔合反应率对研究中子星表面超级暴现象的点火机制有重要意义。由于次级束流强过低，无法使用传统固体靶实验技术测量垒下熔合反应截面。活性靶技术的发展为垒下丰中子核素熔合反应截面的测量提供了可行的途径。基于Geant4模拟详细地分析了多重采样电离室（MUSIC）与时间投影室（TPC）两种活性靶探测器中熔合反应与弹性散射的运动学性质，给出了4种熔合反应鉴别判据，并且计算了由这些判据误判引起的熔合截面系统误差。在Ecm=13.6 MeV时，MUSIC与TPC的弹性散射误判截面分别为0.5 mb和2.9×10-3 mb，都远小于此时熔合截面（877 mb）。在垒下，MSUIC的熔合截面系统误差已经超出实验测量要求，而TPC能够进行实验测量的能量可以降低至Ecm=4.7 MeV。
Reaction rates of fusion reactions among neutron-rich nuclei in the astrophysical environment are of great significance to understand the ignition of superbursts on neutron stars. Since beam intensity is rather low for radioactive ion beams, it is extremely difficult to operate a direct measurement for cross sections of such fusion reactions below the Coulomb barrier using thick target technique. In this case, a novel technique, active target technique, has been developed recently. To study the energy limit for measurement below Coulomb barrier, the kinematics of elastic scattering and fusion reaction in MUSIC and TPC are discussed with Geant4 simulation. Four identification methods are used and uncertainties of cross sections resulted from misjudgments are calculated. With Ecm=13.6 MeV, the uncertainties of cross sections for MUSIC and TPC are 0.5 mb and 2.9×10-3 mb, respectively. The uncertainties for MUSIC become far beyond measurement when below coulomb barrier, while TPC remains to be a suitable detector for measuring fusion cross sections until Ecm=4.7 MeV.
In the framework of the relativistic mean field theory(RMFT) with GL91 cets, the momentum of inertia (I) of slowly rotating neutron stars is studied by perturbative approach. The scalar hyperon coupling should lie in the range of Xσ=0.59~1.0 to be compatible with massive neutron stars. As Xσ increases from 0.59 to 1.0, the maximum momentum of inertia(Imax) of neutron (protoneutron) stars increases by 89% (60%). According to the data of Crab, the maximum energy loss(dE/dt) of neutron (protoneutron) stars will increase by 44%(25%)and the maximum magnetic field (B) will increase by 48%(38%). I and dE/dt of PSR J0348+0432 both increase by 14%, while B decreases by 10% as Xσ increases from 0.59 to 1.0. So if the upper bound of I, or the accurate values of both the mass and I of neutron stars could be provided by the astronomical observations, the hyperon couplings should be further constrained in the future.
The quark matter exhibits a rich phase structure at different temperatures and baryon number densities. At high baryon density and low temperature, the color-flavor locked phase is believed to be the ground state of the quark matter. We present an introduction to various vortices in the color-flavor locked quark matter, especially for the semi-superfluid vortices, and their research method (Ginzburg-Landau method). The influence of magnetic field and rotation on properties of these vortices is discussed. Due to the possibility of forming a semi-superfluid vortex in the core of the dense star, this result is of practical significance in the study of dense stars. If considering other factors, such as temperature and quark mass, study of the vortex structure properties in the quark matter could provide new perspectives for related fields, for instance dense star physics.
中国科学院近代物理研究所在CSR-LINAC项目中设计了一台108.48 MHz的IH型RFQ直线加速器。该RFQ可以将质荷比为3~7的离子从4 keV/u加速到300 keV/u。在完成束流动力学设计的基础上，主要针对RFQ腔体的高频电磁设计展开了研究，同时利用了电磁场仿真和束流动力学模拟来研究腔体的四极场不平整度和二极场及其动力学影响。未经调谐的情况下，腔体的谐振频率为108.15 MHz，腔体空载品质因子Q0为5 910，腔体功耗为123 kW。通过在支撑板两端增加底切的设计，将腔体的四极场不平整度由-21%~ 12%优化至±2.5%，满足了束流动力学要求。腔体的二极场为-3%~ -2.2%，使得束流在垂直方向小幅振荡，RFQ的垂直方向接受度减小5%。为了保证功率馈入时反射较小，将耦合器设置在临界耦合状态，耦合面积为940 mm2。为了补偿腔体的频率偏差和漂移，设计了调谐量分别为707和132 kHz的固定调谐器和可动调谐器。
The 108.48 MHz IH type RFQ for CSR-LINAC project is under design at Institute of Modern Physics, Chinese Academy of Sciences. This RFQ can accelerate heavy ions with mass to charge ratio of 3~7 from 4 keV/u to 300 keV/u. According to the beam dynamics requirement, the RF structure design has been finished. The quadrupole field unflatness and dipole field of the cavity were studied by electromagnetic simulation and beam dynamics simulation. The frequency of the cavity without tuning is 108.15 MHz, the Q0 of the cavity is 5910, and the RF power loss is 123 kW. The quadrupole field unflatness of ±2.5%,which was -21%~12% before optimizing, is achieved to meet dynamics requirement through the undercuts in cavity supporters. The dipole field of -3%~ -2.2% causes the oscillation of the beam center and acceptance reduction of 5%. The power coupler must be in critical coupling state with the coupling area of 940 mm2 for minimum reflection coefficient. The tuners, consist of coarse and fine tuners with frequency shift of 707 and 132 kHz respectively, is used for tuning of frequency deviation of the cavity.
The isochronous mode of the Spectrometer Ring at the High Intensity heavy-ion Accelerator Facility (HIAF) project in China offers the capacity of measuring the mass and half-life of short-lived nuclides. The transition energy settings of the SRing are 1.43 and 1.67, which have been calculated in the same injection scheme. The resolution of mass or revolution time is the most important parameter of the isochronous mode design of a storage ring. The nonlinear magnetic field errors, including high-order magnet field of dipole, fringe field of magnets, have strongly effect to the resolution of revolution time. High-order corrections are required to improve the resolution of revolution time and mass. In this paper, the SRing linear isochronous optical were shown. The influence of nonlinear magnetic field errors on the revolution time resolving power were investigated. With 3 sextupole families and 1 octupole family corrections, the relative variation of revolution time reaches 4.6×10-7 with the momentum spread of ±0.2%. The relation of the relative standard revolution time deviation σ(T)/T and revolution turns was researched. With corrections of high-order isochronous condition and emittance influence by 3 sextupole families and 1 octupole family, one can reach a resolution of up to σ(T)/T=3.5×10-7, which corresponds to the mass resolution of △m/m=1×106.
功率耦合器是粒子加速腔射频功率馈送的关键部件。耦合器在安装至加速腔之前，必须进行常温高功率测试和锻炼，以检验加工工艺和设计指标，提高其射频性能。详细介绍了中国科学院近代物理研究所ADS25 MeV加速器样机162.5 MHz耦合器测试平台的改进设计。针对原有接触式测试锻炼方式的不足，提出非接触式测试锻炼方案。对耦合器测试锻炼过程进行了物理抽象，采用理论模拟的方法分析测试腔体功率传输。基于分析结果设计了低损耗、宽通带、多用途的非接触式耦合器测试腔体。该腔体可实现20 kW测试功率下60 W左右的腔体损耗和15 MHz-3 dB带宽。
Fundamental power couplers (FPC) are crucial components for feeding RF power to the accelerating cavities. Before being installed on the accelerating cavity, a coupler must be tested and conditioned at room temperature to check its fabrication quality, to verify its design specifications, and improve its RF performance. This paper thoroughly introduced the design of a test stand for the 162.5 MHz coupler of ADS 25 MeV demo facility at IMP, CAS. In order to overcome the shortcomings of the original contacting test method, a noncontacting test scheme was proposed. A physical model was built for the the coupler test and the test cavity power transmission was analyzed theoretically. Based on the analysis results, a low-loss, wide-passband and multipurpose non-contacting coupler test cavity was designed. With the new test cavity, a power loss of around 60W and a -3 dB bandwidth of 15 MHz at a test power of 20 kW was achieved.
Back-n是中国散裂中子源（CSNS）的反角中子束线，适用于精密核数据的测量。该装置的谱仪读出电子学采用共性化设计方法，利用高速波形数字化技术精密采集探测器输出信号波形。为完成对两通道、1 GSps，12 bit采样数据的读出和板载外设的控制，可以使用一种基于FPGA的高速数据实时读出方法。该方法不仅实现了数据接收、缓存上传等通用需求，还通过软件配置满足了实时触发处理等针对特定物理实验的特性需求。此外，FPGA的灵活使通过固件更新支持新实验或添加新功能成为可能。测试结果表明，该方法能够适应Back-n波形数字化模块高速数据读出的需求，峰值处理能力可达24 Gbps，符合物理实验需求。目前，基于实时读出方法实现的波形数字化模块已完成中子源谱仪实验现场的安装，工作稳定。
Back-n is a back-streaming beam line at China Spallation Neutron Source, which is suitable for measure nuclear data precisely. The readout electronics of the spectrometers at this facility adopts general-propose design method, using high-speed waveform digitizing technology to record the detector output signal accurately. To read out two channels, 1 GSps, 12 bit sample data and control on-board devices, the real-time readout method of high-speed data based on FPGA technology can be considered. The method not only realizes the general requirements of the data upload, but also processes real-time triggers according to experiments via configuration. In addition, due to the flexibility of FPGAs, new experiments or new features can be supported through firmware updates. The test results show that the method is suitable for the high-speed data readout of field digitizing module at Back-n and peak capacity reaches up to 24 Gbps, which meets the requirements of the physical experiment. The field digitizing modules based on this method were installed at Back-n and work normally.
本工作是基于蒙特卡罗模拟软件FLUKA对高能强流重离子加速器（HIAF）高能辐照终端感生放射性进行初步研究。该终端可运行质子最高能量为9.3 GeV，最大流强是1.45×1012 pps（particle per second）。研究内容包括：（1）预测高能辐照终端内活化物质的放射性活度特性；（2）预测不同冷却时间高能辐照终端内残余剂量率分布。研究结果表明，HIAF正常运行时高能辐照终端内的感生放射性主要受束流垃圾桶活化产生的放射性核素影响。当加速器连续运行100天冷却4小时，垃圾桶表面残余剂量率为2.375 mSv·h-1。终端内空气中13N和15O动态饱和比浓度大于其对应的导出空气浓度。冷却水中13N和15O的活度大于对应的ALImin。该研究是HIAF辐射防护基础研究以及加速器环境影响评价的一项重要内容。
The Monte Carlo code FLUKA was used to predict the induced radioactivity of high-energy irradiation terminal of HIAF. The maximum energy of proton is 9.3 GeV, and the maximum current is 1.45×1012 pps (particle per second). In this study we were to predict:(1) the activity properties of activated substances in the experimental terminal; (2) the residual dose rate distribution in the experimental terminal at different cooling time. The results indicate that the induced radioactivity in the high energy irradiation terminal of the HIAF is mainly affected by the radionuclide induced in the beam dump. The residual dose rate on the surface of the beam dump is 2.375 mSv·h-1, after 100 d irradiation and 4 h cooling. The dynamic saturation ratio of 13N and 15O induced in the air inside the terminal is higher than its corresponding derived air concentration. The activity of 13 N and15O induced in cooling water is higher than its ALImin. This study is a part of radiation protection basic research and environmental impact assessment for HIAF.
随着脉冲强流中子源的发展，对高性能中子探测器提出了更大的挑战，3He气体资源严重短缺和高计数率中子探测器的迫切需求，已开始制约着中子源应用技术的发展。中国科学院高能物理研究所针对中子的特殊性，专门研发了一种陶瓷基材的nTHGEM（neutron Thick Gaseous Electron Multiplier）探测器用于中子探测。基于nTHGEM的中子探测器具有高计数率、高位置与时间分辨能力、增益大、制作工艺简单，且便于大面积制作的特点，是目前国际上发展替代3He探测技术的重要方向之一。为了详细研究nTHGEM探测器的本身性能，本工作使用55Fe放射源研究了nTHGEM探测器的增益、计数率稳定性、能量分辨率等关键参数与nTHGEM膜间电压、收集场强、漂移场强之间的关系，优化了nTHGEM探测器在不同工作气体中的工作参数，为后续进一步优化nTHGEM探测器设计和工艺奠定了基础。实验结果表明，单层nTHGEM探测器在Ar（90%）+CO2（10%）混合气体中增益能达到103，探测器计数率稳定性良好。另外，还在中国原子能科学研究院的CARR反应堆（China Advanced Research Reactor）上进行了中子束流实验，通过狭缝测量到探测器位置分辨率为（3.01±0.03）mm（FWHM），已经接近高气压3He MWPC中子探测器水平。
With the development of pulsed intense neutron source, the high-performance neutron detector poses more challenges. The severe shortage of 3He gas resources and the urgent need of neutron detector with high counting rate have begun to restrict the neutron source application technology development. In response to the particularity of neutrons, the Institute of High Energy Physics of CAS developed a nTHGEM(neutron Thick Gaseous Electron Multiplier)of ceramic substrate for neutron detection. The neutron detector based on nTHGEM is one of the most important directions for the development of alternative 3He detection technology in the world at present because of its high counting rate, high position and time resolution, large gain, simple fabrication process and large area production. In order to study the properties of nTHGEM detector in detail, this paper studied the relationship between nTHGEM detector's gain, counting rate stability, energy resolution and other key parameters and nTHGEM film voltage, collection field strength and drift field strength using 55Fe radioactive source, Optimized the working parameters of nTHGEM detector in different working gases, which laid the foundation for further optimization of nTHGEM detector design and process. The experimental results show that the single-layer nTHGEM detector has a gain of 103 in a Ar(90%)+CO2(10%) mixed gas with good counting rate stability. In addition, a neutron beam experiment was performed on the China Advanced Research Reactor at the China Institute of Atomic Energy, and the position resolution of the detector was (3.01±0.03) mm (FWHM) measured by slits. Its performance is close to the high pressure 3He MWPC neutron detector level.
The purpose of this study is using different doses of carbon ion beam irradiation on oregano essential oil microcapsules, to investigate function of control release and anticoccidial activity in chickens. The results showed that the content of main components in oregano essential oil microcapsules after carbon ion beam irradiation, thymol and carvacrol, have little change. Moreover, it can obtain more object products and better bioactivity after the irradiation treatment. Among these different doses of irradiation, our findings showed that Microcapsule groups with 400 Gy dose irradiation showed the highest yield (68.44%) and the best anticoccidial activity. After feeding chickens infected with Eimeria tenella, the swelling of caecum and duodenum were significantly mitigated and blood contents were also significantly reduced. The bloody stool index of chickens was as low as zero on the seventh day of infection, and the anticoccidial index (ACI) is 179.39.
The objective of this research is to study and develop a proton spot scanning path optimization method using an improved genetic algorithm for proton therapy and to evaluate the scanning time under clinical conditions. An Improved Adaptive Genetic Algorithm (IAGA) based scanning path optimization module was developed and integrated into the home-grown treatment planning system. Four cases, including two AAPM TG-119 standard cases and two clinical cases, were selected to compare their scanning path length before and after scanning path optimization. For the two AAPM TG-119 cases, the optimized scanning path length dropped by 27.17% and 18.72%, and for the corresponding clinical cases, the optimized scanning path length dropped by 25.36% and 32.95% respectively. The performance of scanning path optimization was affected by the number of zero-weight spots and connected regions in the scanning map. IAGA based scanning path optimization can reduce the total scanning path length in intensity modulated proton therapy and, therefore, can be used in spot rescanning to accommodate organ motion.
配备电子冷却装置的重离子储存环为开展高电荷态离子的双电子复合（dielectronic recombination，DR）精密谱学研究提供了绝佳的实验平台。本工作在兰州重离子加速器冷却储存环主环（HIRFL-CSRm）上开展了类锂36，40Ar15+离子的双电子复合实验，实验观测了电子-离子质心系能量范围为0~35 eV的双电子复合速率系数谱。通过外推法获得了36，40Ar15+离子2s1/2→2p1/2和2s1/2→2p3/2的跃迁能量。同时利用GRASP2K程序理论计算了36，40Ar15+离子2s1/2→2p1/2和2s1/2→2p3/2跃迁的质量移动因子和场移动因子，进而得到双电子复合谱的同位素移动值。36，40Ar15+离子2s1/2→2p1/2和2s1/2→2p3/2同位素移动分别为0.861 meV和0.868 meV。它们均小于目前CSRm上双电子复合实验的实验分辨为~10 meV，进而解释了实验测量的DR谱上未能观察到同位素移动的原因。然而，高电荷态离子的同位素移动场效应与原子序数Z5成正比，因此，在重离子加速器冷却储存环实验环（HIRFL-CSRe）以及未来大型加速器——强流重离子加速器装置（HIAF）上有望通过DR精密谱学方法研究高电荷态重离子甚至放射性离子的同位素移动，进而获得相关原子核的核电荷半径等信息。
The cooler storage ring is equipped with an electron-cooler. It is an excellent experimental platform for dielectronic recombination (DR) experiment of highly-charged ions. In this paper, the dielectronic recombination experiments of lithium-like Ar15+ ions with mass number 36 and 40 are conducted at the HIRFL-CSRm(main ring of the Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou). The experimental electron-ion collision energy scale is from 0 eV to 35 eV. Extrapolation method is exploited to obtain the excitation energies of transitions 2s1/2→2p1/2 and 2s1/2→2p3/2 of the 36,40Ar15+ ions from experimental data. Meanwhile, GRASP2K program is utilized to calculate the mass shift factors and field shift factors of 36,40Ar15+ ions for 2s1/2→2p1/2 and 2s1/2→2p3/2 transitions to obtain isotope shifts in DR spectra. In theoretical calculation, isotope shifts of 36,40Ar15+ ions corresponding to 2s1/2→2p1/2 and 2s1/2→2p3/2 are 0.861 meV and 0.868 meV, respectively. They are both less than the experimental precision (~10 meV) of these dielectronic recombination experiments at the CSRm, which explains that isotope shifts cannot be distinguished from the experimental dielectronic recombination spectra. However, the field shift of highly-charged ions is proportional to Z5. In the future, the dielectronic recombination experiments of highly-charged heavy ions even radioactive ions will be conducted at the HIRFL-CSRe (experimental ring of the Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou) and the future large accelerator facility——HIAF(High intensity Heavy-ion Accelerator Facility) to measure isotope shifts to obtain the nuclear charge radius information.
采用不同材质的刻槽绝缘平行板，包括高纯度石英玻璃、聚四氟乙烯（Teflon）、酚醛树脂（电木）和聚甲醛板（赛钢板），并在15 pA/mm2 ~14.3 nA/mm2范围内改变入射流强，利用1 500 eV电子束入射上述绝缘平行板，实验研究了上述平行板对电子束的导向行为。实验发现，上述电子束通过上述平行板时存在明显的导向现象，其导向行为与束流流强和绝缘材质无关。据此，可排除绝缘平行板内表面沉积电荷自组织充放电过程中，以绝缘材料的面电阻和体电阻对地泄放的线性形式放电过程。
Adopting several grooved parallel plates made by different insulators, such as high-purity fused quartz, Teflon, Bakelite and POM (Polyformaldehyde), and further adjusting the electron beam current in a wide range (tens of pA~tens of nA), the discharging mechanism in the self-organizing charge and discharge processes of electron guiding was investigated and discussed by using 1 500 eV incident electron beam. The present results show that, the electron guiding behaviors are obviously existing when such electron beam is transmitted through the above grooved insulating parallel plates, which are independent on beam current and insulators. Our results suggest that, the possibilities of the accumulated charges on inner-surface of grooved parallel plates linearly discharging through surface and bulk resistances of plates into the ground should be excluded.
Neutron flux measurements were carried out at VENUS-Ⅱ lead-based zero power reactor by neutron activation method combined with solid-state nuclear track detectors (SSNTD). This experimental method was proposed based on the principle of nuclear number conservation when a foil was irradiated in an unsteady-state neutron field. By this method, thermal neutron flux distributions inside the He-3 duct were measured when VENUS-Ⅱ was operated under unsteady-state. The neutron flux distributions were also calculated with MCNPX code and were consistent with the experimental data. In addition, the neutron fluxes in the outer layer of VENUSⅡ were measured under steady-state. These results would benefit the further study of experimental methods for neutron flux measurement and provide important support for the design of CiADS.
燃料组件内冷却剂的横流对反应堆堆芯的换热有很大影响，为研究铅基反应堆燃料组件内冷却剂的横向速度分布，对CiADS反应堆燃料组件组件局部的7，19棒束的单螺距及多螺距多种几何进行建模和CFD（Computational Fluid Dynamics）模拟，并对其间隙内横向速度进行分析。研究表明： 19棒束组件内通道、角通道的相邻间隙内横向速度的分布在组件轴向和横向上有明显周期性，横向上根据两个内通道间隙平移旋转的位置关系由一个间隙的结果经过平移一定相位角度可以得到另一个间隙分布结果，沿轴向多螺距模型每个螺距长度内横向速度分布一致。7棒束组件在相同类型通道内横向速度分布大小及趋势与19棒束一致。少棒束单螺距组件结果进行横向及轴向的周期性延拓可以得到多棒束多螺距模型间隙内的横流分布。
Cross flow of a coolant in fuel assembly had a great impact on the heat transfer of a reactor core. In order to study the characteristics of the cross flow in lead-based fast reactor assemblies, the CiADS fuel assemblies were used as research object. Fine geometric models and CFD simulation of 7 and 19 pin bundle and multi-pitch length assemblies based on CiADS fuel assemblies were carried out. The distribution of the cross flow velocity in several geometric models was compared and analyzed. The results show that the distribution of the cross flow velocity in gaps of interior and corner channel in 19 pin bundle has obvious periodicity in both axial and horizontal direction. In the horizontal direction, the results of one gap can be translated by a certain phase angle to obtain another gap distribution result according to the positional relationship of the translational rotations of the two internal channel gaps. The distribution of cross flow velocity is uniform in each pitch length of multi-pitch model in the axial direction. And the distribution of transverse flow in gaps of 7 pin bundle is similar to the distribution in the same kind of gaps in 19 pin bundle. The results of fewer pin bundle with single pitch length can be periodically extended in axial and transverse direction to obtain the characteristics of cross flow in geometric models with multi-pitch length and more rods.