2018年 第35卷 第1期
There is a puzzle in the Λc+ family, i.e., one member with JP=3/2+ is missing in a L=2 multiplet which the heavy quark effective theory predicts, and JP's of Λc(2765)+ and Λc(2940)+ are unknown. Using a light diquark picture to calculate baryon masses, we study possible assignments of two Λc's with unknown JP and the missing Λc+ with 3/2+ for L=2, and we find the most probable possibility that the peak corresponding to Λc(2880)+ actually includes a missing member with spin 3/2+ for L=2 and that quantum numbers of Λc(2765)+ and Λc(2940)+ are 2S(1/2+) and 2P (1/2-), respectively.
Recently, with the help of auxiliary field method, Ref. obtains an analytical mass formula for nonstrange light mesons in quasi-relativistic quark model. In this work, we generalize this method to the case of strange light mesons, and obtain a mesonic mass formula which is flavor-dependent. The results show that the mass of low excitations given by the mass formula are in good agreement with the experimental data and the average error is around 30 MeV. Our mass predictions for the high states also agree well with the other calculations in the literatures, particularly, the string model calculations.
Recently, we have carried out systematically studies on the structural properties of proton number Z=38, neutron number N=63 and 64 neutron-rich isotopes 101,102Sr by using the projected shell model (PSM) with consideration of cross shell excitation. The rotation spectra, the moment of inertia and the electromagnetic transition properties (such as B(E2) and g-factor) are calculated and compared with the corresponding experimental data in this paper. Furthermore, more high spin states are predicted in the calculation and expected to be confirmed experimentally. The results show that the PSM can not only well analyze the structural properties of yrast bands in 101,102Sr but also interpret the variation of the moment of inertia, electromagnetic transition with spins in terms with the theoretical band diagram. The good agreement with the experimental data suggests that the PSM with the adopted effective interactions can be generalized to study the nuclear structure of 101,102Sr isotopes in neutron-rich mass region. For 101,102Sr isotopes, the nucleons begin to fill proton g9/2 and neutron h11/2 orbital, the dependence of nuclear structure and properties on the different orbital occupies is described by carefully analyzing the contribution from proton g9/2 and neutron h11/2 orbital to the configuration of rotational bands in band diagram.
从35 MeV/nucleon 40Ca+40Ca反应实验数据中提取了碎片Z从1到9的横向流，发现探测器阈值、探测系统的角分辨等实验条件对横向流电荷依赖的形状有显著的影响。在考虑实验条件并采用软的核物质状态方程（K=200 MeV）之后，CoMD模型计算结果很好地重现了实验中横向流电荷依赖的形状。这表明如果要更加精确地提取实验中的横向流，必须使用阈值更低、角分辨更好的探测系统。此外，结合Kohley等[Phys Rev C，2012，85：064605]从实验中提取的横向流，讨论了横向流电荷依赖的形状存在异同的原因。1 ≤ Z ≤ 6的横向流电荷依赖呈肩峰形状可能是实验条的影响引起的，而我们的实验中Z ≥ 6的横向流的减小可能是由于动量守恒对集体运动的抑制。
The transverse flow in the reaction of 40Ca+40Ca at 35 MeV/nucleon has been determined for emitted isotopes with Z=1 to 9. A significant modification of the Z-dependent flow pattern caused by the experimental filters, the detector thresholds and the angular resolutions (△ϕ) of the detector array, is observed. With the application of the appropriate experimental filters, the general trend of the experimental Z-dependent flow is well reproduced by the Constrained Molecular Dynamics (CoMD) simulation, employing an effective interaction corresponding to a soft EOS (K=200 MeV). This fact suggests that to determine the flow values more precisely, a detection system with lower energy threshold and better angular resolution is urgently required. Additionally, together with the parallel work of Z. Kohley et al.[Phys Rev C, 2012, 85:064605], the pattern of the experimental Z dependence of transverse flow is also discussed. The shoulder patterns of Z-dependent flow for 1 ≤ Z ≤ 6 can be attributed by the experimental filters, while the reduction of flow for Z ≥ 6 in our experiment can be caused by the suppression of collective motion under the momentum conservation.
对400 AMeV 12C诱发乳胶核反应重电离粒子的前后关联进行了研究。重电离粒子来源于靶核碎片，分为灰径迹粒子和黑径迹粒子两种。实验结果很好地验证了核-核碰撞几何模型。灰径迹粒子的发射在前、后半球是各向异性的，而黑径迹粒子的发射基本是一致的。向前、向后发射的灰径迹粒子、黑径迹粒子平均多重数对重电离粒子数nh呈线性依赖，黑径迹粒子、灰径迹粒子的向前发射随nh的增加而增加的幅度分别大于其向后发射随nh的增加而增加的幅度，但核内级联效应受靶核大小的影响，向后半球内发射的灰径迹粒子平均多重数随nh的增加有饱和现象，这些多重数关联特性基本上可以利用基于碰撞几何的旁观体-反应体模型及级联蒸发模型来解释。
The forward-backward multiplicity correlation of heavily ionized particles produced in 12C-emulsion interactions at 400 AMeV is investigated. The heavy ionized particles, come from the target fragments, are divided into grey track particle and black track particle. The experimental results can be well explained by the geometry model of the nucleus-nucleus collisions. The emission of grey track particles in forward and backward hemisphere is not isotropic, but the emission of black track particle is almost isotropic. The averaged multiplicity of grey track particles and black track particles in forward and backward hemisphere linearly depend on the number of heavily ionized particle nh, the correlation strength in forward hemisphere is greater than that in backward hemisphere, but the dependence of grey track particle in backward hemisphere on the number of heavily ionized particle nh shows the saturation because of the intranuclar cascade effect is influenced by target size. The characteristics of multiplicity correlations can be well explained by the participant-spectator model based on the colliding geometrical picture and the cascade evaporation model of high energy nucleus-nucleus collisions.
BRing is the main accelerator of High Intensity heavy Ion Accelerator Facility(HIAF) and its design current is 1×1011 particles per pulse (238U34+). To accumulate beams up to the design current, the injection gain has to reach 88. Two planes painting injection scheme is proposed for BRing. This scheme uses a tilted electrostatic septum and 8 bump magnets to paint beams into horizontal and vertical phase space simultaneously. It can inject enough beams into the ring in a short time and paint beams uniformly. The injection process is simulated using ORBIT code and 113 turns is injected into BRing with an injection efficiency of 97.7% which meets the requirement for beam current of BRing. The accumulated beams are distributed uniformly in transverse and hence have a little tune shift of -0.02 which reduces the risk of beam loss due to the resonance. Errors of injection parameters are analysed and the result shows two planes painting injection scheme has a high tolerance for errors of injection parameters.
基于KONUS束流动力学理论，完成了一台工作频率为162.5 MHz、占空比为1%的交叉指型漂移管直线注入器（IH-DTL）的动力学设计。该IH-DTL内置两套三组合四极透镜，共有41个加速单元，可为同步加速器提供流强400 eμA、能量4 MeV/u的C4+束流。在动力学设计过程中着重对每个加速间隙的同步能量偏差、注入相位和间隙电压等参数进行优化，使得该IH-DTL的横向归一化RMS接收度达到0.24 πmm·mrad，且横纵向归一化发射度增长小于10%，有利于提高同步环的注入效率。然后根据动力学设计的结构参数进行IH-DTL的高频仿真计算，将得到的三维电磁场分布导入PIC粒子跟踪程序中进行束流动力学模拟。动力学模拟结果显示，束流在IH-DTL出口的横向自然发射度小于13 πmm·mrad，达到了同步环的注入要求，而且在7%的垂直二极场分量下，束流中心的横向偏移在±0.5 mm以内，整体的束流传输效率高于99%。
An interdigital H-mode drift tube linac (IH-DTL) with KONUS beam dynamic has been designed, which operation frequency was chosen 162.5 MHz. This IH-DTL consists of 41 accelerating cells and two quadrupole magnets triplets, can provide the C4+ with the current of 400 eμA and energy of 4 MeV/u for the synchrotron. In the beam dynamic design, the synchronous particle energy, inject RF phase and the acceleration voltage of each gap are optimized carefully to make the transverse normalized RMS acceptance of the IH-DTL to be 0.24 πmm·mrad and the beam emittance growth small than 10%. Then the RF structure was designed and the 3D electromagnetic field was imported into the PIC particle tracking code for the beam dynamic simulation. The transverse beam emittance at the exit of the IH-DTL is small than 13πmm·mrad which meets the injection requirement of the synchrotron. What is more, under the 7% vertical dipole fields component, the offset between the beam center and the drift tube's axis is ±0.5 mm at most. The transmission efficiency of the IH-DTL is higher than 99% for the whole beam in the acceptance.
High current proton source and the low energy beam transport(LEBT) are the key front-end systems for CIADS injector:high current proton linac accelerator. CIADS injector's LEBT adopts double solenoid matching structure, using a limit cone which can partially avoid H2+ and H3+ which injecting into the back-end linac accelerator may impact the long-term stability and reliability of the whole system. It will be an effective method to separate the hybrid ions (H+, H2+, H3+) by adding a dipole magnet at LEBT. In this article, we simulated and mesasured the high current proton beam quality behind the LEBT with a 30 degree dipole. The results show that the the proton beam quality is significantly effected by high-order magnetic fields of the dipole magnet, and the effect increases with the increase of the beam envelope. The achieved result is useful for the LEBT design of CIADS injector.
针对物理实验读出的需求设计了一款低功耗12 bit 30 MSPS逐次比较型模数变换器（Analog-to-Digital Converter，ADC）芯片，为评估其性能指标参数，需进行系统的测试。在本研究工作中构建了测试系统，然后按照IEEE标准进行了系统的测试和分析。测试结果表明，输入信号在基带范围内ADC有效位（Effective Number Of Bit，ENOB）约为9 bit，达到了本版本芯片的设计指标。同时，综合分析静态性能与动态性能测试结果，可以通过优化逐次比较型ADC中电容阵列电容失配参数，进一步提升ADC的非线性指标，为下一版芯片的改进设计提供了参考依据。
Aiming at the requirement of readout electronics in physics experiments, a 12 bit 30 MSPS successiveapproximation-register (SAR) analog-to-digital converter (ADC) with low power consumption has been designed. To evaluate the performance of this ASIC, we conducted a series of tests. We set up a test system, and we tested the ADC according to IEEE std 1241-2010. The test results indicate that the effective number of bit (ENOB) of the ADC is around 9 bits when the input signal is in the first Nyquist zone, which has met the design requirements. According to the results of dynamic and static tests of this ADC, we found that the non-linearity performance of this ASIC can be further enhanced by improving the mismatching among the capacitor array, and this provides important information for the design of the second version of this ADC.
The China initiative Accelerator Driven System (CiADS) is the first integrated ADS facility designed to study the safety disposal of nuclear waste. As a nuclear facility, it will cause radiological impact on the environment. Therefore, the assessment of radiological impact on the environment around this facility will not only meaningful to the public health, but also offers significant guides to the shielding design of CiADS. Pebble samplings were collected around the campus of the Heavy Ion Research Facility in Lanzhou (HIRFL) and irradiated by a 241Am-Be neutron source. Based on the γ-spectrum measured by a HPGe detector before and after the neutron irradiation, the specific activities of induced radionuclides 24Na,54Mn,56Mn and 27Mg in these samples were analyzed and compared with the Monte-Carlo simulation values obtained with the Geant4 toolkit. The comparison between the experimental and simulated results indicates that Geant4 toolkit is feasible for radiation impact assessment of nuclear facilities, such as CiADS. Then the neutron spectrum outside the concrete shielding of HEBT tunnel of the CiADS have been simulated by the Geant4 toolkit, and the saturation activities of the induced nuclides in the first 10 cm pebble layer have been predicted. The results show that the saturation activities of induced radionuclides in pebbles outside the CiADS shielding are much lower than their exemption values and their radiation impacts to the environment could be ignored.
介绍了一种基于THGEM的X射线光斑寻迹探测器，用于X射线单光子计量技术研究和测量，探测器有效面积200 mm×200 mm，采用128路基于ASIC和FPGA的高速读出电子学，探测器分为中间高分辨区和外围低分辨区两部分，两部分共用一套读出电子学。实验在中国计量科学研究院利用X光机产生的束线，测试光斑位置、光斑精细分布以及探测器的位置分辨。实验结果表明，探测器实现了同时对光斑寻迹和光斑的精细测量，探测器中间高分辨区x方向的位置分辨率为0.63 mm（FWHM），y方向位置分辨率为0.62mm（FWHM），探测器各项性能指标均达到了预期目标。
This paper introduces the detector of X-ray spot tracing based on the THGEM. It is used for X ray single photon measurement technology research and measurement with an effective area of 200 mm×200 mm. The circuit board has 128 array of high speed readout electronics based on ASIC and FPGA. And it is divided into two parts:the middle area of high sensitive and the peripheral area of low sensitive. The two parts share a set of readout electronics. The experiment tests the position and the fine structure of the beam line produced by X ray machine in National Institute of Metrology. The results of the experimental show that the detector realizes both the spot tracing and the fine structure of the spot. The position resolution is 0.63 mm in x direction and 0.62 mm in y direction in high sensitive of the detector, which achieve the desired goal of preliminary design.
为了提高纠错编码（ECC）的有效性，先进的静态随机存储器（SRAM）多采用位交错结构。但是，在没有物理版图信息的情况下，位交错设计使得从辐照测试数据中提取出多单元翻转（MCU）变得更加困难。运用Bi离子辐照带有ECC的65 nm SRAM器件，研究了该款器件在重离子辐照下的敏感性。为"伪多位翻转（FMBU）"以及MCU的数据分析提供了理论指导和帮助，完善了判别MCU的基本法则。除此之外，研究结果表明，ECC的汉明编码对于纳米器件的效果不够理想。在未来的空间应用中，需考虑更高层次的编码算法来抵抗单粒子翻转。
In order to improve the robustness of error-correcting codes (ECC), modern static random access memory (SRAM) always use bit-interleaving structure. However, in the absence of physical layout information, the bit-interleaving design makes it more difficult to extract the multiple-cell upset (MCU) from the test data. In this paper, the sensitivity of Bi ion irradiation was investigated in a 65 nm technology SRAM with ECC. The experimental results provide a theoretical guidance and help for the fake multiple-bit upset (FMBU) and MCU data analyzing, which improve and perfect the basic rules extracting MCU from the test data. In addition, the results show that the performance of hamming encoding is not ideal in Nano scale SRAM. In the future of space applications, it is necessary to consider more advanced algorithms to against SEU.
The layer number of MoS2 with different thickness was determined by the optical microscope and Raman spectra. And the damage effect of the CVD (chemical vapor deposition) prepared single-layer MoS2 sample irradiated by 209Bi ions was analyzed by the combination of Raman analysis and AFM observations. With the increase of irradiation fluence, the Raman characteristic peaks of E2g1 and A1g corresponding to both phonon vibration modes gradually bluely shift, and the intensity of the peaks obviously decreased. This is due to the fact that the 209Bi ion irradiation results in the latent track type lattice defects and they adsorb the oxygen molecules in the air ended with the p-type doping. Meanwhile, from the AFM image of the mono-layer of irradiated MoS2 under the 5×1010 ions/cm2, it can been seen that latent tracks mainly occur in the form of pits, which different from the hillock tracks observed by mechanical stripping method. The influence of different preparation technology to the track morphology is analyzed. Compared with the Raman and AFM results of MoS2 prepared by mechanical stripping, it is considered that different preparation methods will affect the electron density in single or few layers of MoS2.
Energy selection system (ESS) is an important component for medical proton cyclotron system. It has been widely used to modulate the proton energy in accordance with treatment requirements. ESS consists of the energy degrader which was mostly made of graphite. Recent years, to improve the transmission efficiency of the proton beams, beryllium and boron carbide have been proposed to substitute the graphite. In this work, the Monte Carlo code, TOPAS, was used to simulate the transport process of 200 MeV proton beams traversing the multi-wedge energy degrader made of graphite, beryllium and boron carbide, respectively. Energy fluxes of the protons and secondary neutrons after degrader, as well as the energy dispersion of the degraded proton beams, were calculated. It is found that the energy dissipation effect is nearly identical for all three kinds of degrader material, but using the beryllium or even boron carbide can improve the proton transmission efficiency. However, more secondary neutrons would be produced when proton beams interact with the beryllium and boron carbide, suggesting the need of additional consideration for radiation shielding to devices.
The heavy ion treatment planning system of Institute of Modern Physics(IMP), Chinese Academy of Sciences adopts single Gaussian model to depict the lateral dose distribution of pencil beam currently. Without taking secondary particles produced by heavy-ion pencil beam in medium into full consideration, the single Gaussian model is not accurate enough to describe the lateral dose distribution. In fact, an accurate pencil beam model should include the description of low dose envelope contributed by secondary particles. This work summarized the cause of formation, property, dose contribution, mathematic models and measuring methods of the low dose envelope laterally far away from the incident axis of a pencil beam. Moreover, the lateral dose distribution of heavy ion pencil beams with different energies were calculated by means of the Monte Carlo simulation method, based on the horizontal nozzle of the demonstration facility of heavy ion medical machine in the Wuwei heavy-ion therapy center, and thus the degree of coincidence between the simulated data and different mathematic models was investigated. The results verified that the triple Gaussian model was better than the single and double Gaussian models to depict the lateral dose distribution of heavy ion pencil beams, mentioned from existing papers. Thus, this work provides a basis for further developing practical and accurate pencil beam model for heavy ion cancer therapy.
Abiotic stress can reduce the growth of plant heavily, and the research of salt tolerance of plant mutant is valuable to the study plant stress resistance. Dry seeds of Arabidopsis thaliana were irradiated by carbon ion beams with energy of 43.3 MeV/u provided by Heavy Ion Research Facility in Lanzhou (HIRFL). One stable mutant #197 was obtained from the progenies of the irradiated populations, the study of tolerance to salt stress of this mutant were carried out through physiological and gene transcription anlaysis. The results demonstrated:mutant #197 shown a relatively lower germination rate than wild type in salt stress conditions, meanwhile, the mutant acquired a higher ratio of green embryo than the wild type. In the molecular level, NaCl with high concentrations prompted the transcription of P5CS1 gene rapidly both in #197 muatant and the wide type, and the expression level in mutant was significantly higher than wild type. The expression of ProDH, related to proline degradation, in mutant #197 was slightly less than the wide type. Such expression patterns improved the accumulation of proline, and protect the #197 mutant from salt stress, which may lead to a lower expression of DREB2A and RD29A in mutant compared with wide type.
在ADS散裂靶系统的优化设计中，蒙特卡罗方法结合可靠的散裂反应理论模型进行中子学计算具有重要的作用。本工作利用Geant4程序中的INCLXX模型、BIC模型以及BERT模型和FLUKA程序分别模拟了597 MeV和1 500 MeV质子轰击薄铅靶不同出射角度的中子双微分截面，500，1 500 MeV质子轰击厚铅靶不同出射角度的中子双微分产额，以及400，600，800，1 000和1 200 MeV质子轰击厚钨靶在反角方向（175 °）的中子双微分产额，并与实验数据进行比较。研究表明，对于薄铅靶，Geant4程序的INCLXX模型和FLUKA程序模拟结果与实验符合得更好。能量在10～40 MeV范围内，BIC模型模拟结果明显高于实验数据，而BERT模型模拟结果略微低于实验数据。对于厚铅靶，在40 MeV左右所有的模拟结果都低于实验数据。对于厚钨靶，Geant4程序的BIC模型和FLUKA程序与实验数据符合得较好，INCLXX模型在能量高于60 MeV时模拟结果低于实验数据，BERT模型与实验数据差异较大。总体来看，Geant4程序的INCLXX模型和FLUKA程序进行ADS散裂靶相关的中子学的计算是合理和可靠的。
The reliable Monte Carlo simulation codes coupled with nuclear reaction models play an important role in the neutronic calculation for the design and optimization of the ADS spallation target. In this work, the double differential cross sections at different angles produced from a thin lead target bombarded with 597 and 1 500 MeV protons, the neutron energy spectra at different angles produced from a thick lead target bombarded with 500 and 1 500 MeV protons, and the neutron energy spectra in the backward direction(175°) produced from a thick tungsten target bombarded with 400, 600, 800, 1 000 and 1 200 MeV protons are calculated with the Geant4 code coupled INCLXX, BIC and BERT models and the FLUKA code. The calculations are compared with the available experimental data. The results show that, for the thin lead target, the calculations with the Geant4 coupled INCLXX model and FLUKA code well reproduce the experimental results. In a energy range from 10 to 40 MeV, BIC model obviously overestimates the experimental results, and BERT model slightly underestimates the experimental results. For the thick lead target, all of the calculations underestimate the experimental results around 40MeV. For the thick tungsten target, the Geant4 coupled BIC model and FLUKA code well reproduce the experimental results. INCLXX model underestimates the experimental results above 60 MeV. BERT model bad reproduces the experimental results. Overall, the neutronic calculations with the Geant4 code coupled INCLXX model and FLUKA code for the ADS spallation target is reasonable and reliable.