在HIRFL上的中能重离子物理基础和应用研究

本文总结了三年来在兰州重离子研究装置(HIRFL)上进行的科研工作和取得的成果.简单介绍了HIRFL 的工作状态、次级束流线与ECR 离子源的发展、中能重离子引起的反应研究、热核与远离β稳定线核素的合成与研究和重离子束的应用等. A The scientific activities and achievements made at the Heavy Ion Research Facil- ity Lanzhou (HIRFL) during the past three years are summarized.In addition to the brief in- troduction of the operation status of HIRFL and the development of the secondary beam line and an ECR ion source,the paper describes the experimental studies of intermediate ener- gy heavy ion-induced reactions,the investigation of hot nuclei,the synthesis and study of nuclei far from ...     

Design of a 450 MHz β=0.2 single spoke cavity at PKU

The design of a 450 MHz β=0.2 superconducting single spoke cavity has been finished at Peking University. A theoretical model and a numerical simulation are used to study the relationship between the RF performance and the geometric parameters of the cavity. In this paper, the optimization of the spoke cavity is described in detail. The RF simulation gives the optimum parameters Epk/Zacc of 2.65 and Bpk/Eacc of 5.22 mT/（MV/m）. The mechanical properties of the cavity are also studied. Two stiff ribs are used to offer a credible mechanical stability.     

60Co gamma radiation effect on AlGaN/AlN/GaN HEMT devices

The testing techniques and experimental methods of the ⁶⁰Co gamma irradiation effect on AlGaN/AlN/ GaN high electron mobility transistors （HEMTs） are established. The degradation of the electrical properties of the device under the actual radiation environment are analyzed theoretically, and studies of the total dose effects of gamma radiation on AlGaN/AlN/GaN HEMTs at three different radiation bias conditions are carried out. The degradation patterns of the main parameters of the AlGaN/AlN/GaN HEMTs at different doses are then investigated, and the device parameters that were sensitive to the gamma radiation induced damage and the total dose level induced device damage are obtained.     

A Backward-Looking Optimal Current Lattice Model

An optimai current lattice model with backward-looking effect is proposed to describe the motion of traffic flow on a single lane highway. The behavior of the new model is investigated anaiytically and numerically. The stability, neutrai stability, and instability conditions of the uniform flow are obtained by the use of linear stability theory. The stability of the uniform flow is strengthened effectively by the introduction of the backward-looking effect. The numerical simulations are carried out to verify the validity of the new model. The outcomes of the simulation are corresponding to the linearly analyticai results. The analytical and numerical results show that the performance of the new model is better than that of the previous models.     

mechanical and thermodynamic properties of α-and β-Si3N4 ceramics： ab initio and quasi-harmonic Debye modeling

The plane-wave pseudo-potential method within the framework of ab initio technique is used to investigate the structural and elastic properties of α-and β-Si3N4. The ground-state parameters accord quite well with the experimental data. Our calculation reveals that α-Si3N4 can retain its stability to at least 40 GPa when compressed at 300 K. The α → β phase transformation would not occur in a pressure range of 0-40 （3Pa and a temperature range of 0 300 K. Actually, the α → β transition occurs at 1600 K and 7.98 GPa. For α-and β-Si3N4, the c axes are slightly more incompressible than the a axes. We conclude that β-Si3N4 is a hard material and ductile in nature. On the other hand, β-Si3N4 is also found to be an ionic material and can retain its mechanical stability in a pressure range of 0 - 010 GPa. Besides, the thermodynamic properties such as entropy, heat capacity, and Debye temperature of α-and β-Si3N4 are determined at various temperatures and pressures. Significant features in these properties are observed at high temperature. The calculated results are in good agreement with available experimental data and previous theoretical values. Many fundamental solid-state properties are reported at high pressure and high temperature. Therefore, our results may provide useful information for theoretical and experimental investigations of the Si3N4 polymorphs.     

Adaptive control of bifurcation and chaos in a time-delayed system

In this paper,the stabilization of a continuous time-delayed system is considered.To control the bifurcation and chaos in a time-delayed system,a parameter perturbation control and a hybrid control are proposed.Then,to ensure the asymptotic stability of the system in the presence of unexpected system parameter changes,the adaptive control idea is introduced,i.e.,the perturbation control parameter and the hybrid control parameter are automatically tuned according to the adaptation laws,respectively.The adaptation algorithms are constructed based on the Lyapunov-Krasovskii stability theorem.The adaptive parameter perturbation control and the adaptive hybrid control methods improve the corresponding constant control methods.They have the advantages of increased stability,adaptability to the changes of the system parameters,control cost saving,and simplicity.Numerical simulations for a well-known chaotic time-delayed system are performed to demonstrate the feasibility and superiority of the proposed control methods.A comparison of the two adaptive control methods is also made in an experimental study.     

Backstepping synchronization of uncertain chaotic systems by a single driving variable

In this paper a parameter observer and a synchronization controller are designed to synchronize unknown chaotic systems with diverse structures. Based on stability theory the structures of the observer and the controller are presented. The unknown Coullet system and Rossler system are taken for examples to demonstrate that the method is effective and feasible. The artificial simulation results show that global synchronization between the unknown Coullet system and the Rossler system can be achieved by a single driving variable with co-operation of the observer and the controller, and all parameters of the Coullet system can be identified at the same time.     

Robust finite-time stabilization of unified chaotic complex systems with certain and uncertain parameters

This paper deals with the finite-time stabilization of unified chaotic complex systems with known and unknown parameters. Based on the finite-time stability theory, nonlinear control laws are presented to achieve finite-time chaos control of the determined and uncertain unified chaotic complex systems, respectively. The two controllers are simple, and one of the uncertain unified chaotic complex systems is robust. For the design of a finite-time controller on uncertain unified chaotic complex systems, only some of the unknown parameters need to be bounded. Simulation results for the chaotic complex Lorenz, Lu¨ and Chen systems are presented to validate the design and analysis.     

Electrical and dielectric characterization of Au/ZnO/n-Si device depending frequency and voltage

Au/Zn O/n-type Si device is obtained using atomic layer deposition(ALD) for Zn O layer, and some main electrical parameters are investigated, such as surface/interface state(Nss), barrier height(Φb), series resistance(Rs), donor concentration(Nd), and dielectric characterization depending on frequency or voltage. These parameters are acquired by use of impedance spectroscopy measurements at frequencies ranging from 10 k Hz to 1 MHz and the direct current(DC) bias voltages in a range from-2 V to +2 V at room temperature are used. The main electrical parameters and dielectric parameters,such as dielectric constant(ε"), dielectric loss(ε"), loss tangent(tan δ), the real and imaginary parts of electric modulus(M and M), and alternating current(AC) electrical conductivity(σ) are affected by changing voltage and frequency. The characterizations show that some main electrical parameters usually decrease with increasing frequency because charge carriers at surface states have not enough time to fallow an external AC signal at high frequencies, and all dielectric parameters strongly depend on the voltage and frequency especially in the depletion and accumulation regions. Consequently, it can be concluded that interfacial polarization and interface charges can easily follow AC signal at low frequencies.     

兰州重离子冷却储存环工程

兰州重离子加速器冷却储存环是兰州重离子研究装置的后续工程 .它的建造目的是将重离子束的能量提高到 1 Ge V/u附近 ,同时利用储存环电子冷却技术将束流品质提高一个数量级 ,并提供更多种类的重离子束 ,以开展更广范围和更高精度的物理实验 .兰州重离子加速器冷却储存环是一个双储存环系统 ,由一个主环和一个实验环构成 .对其总体布局、总体参数、主要功能进行了介绍. HIRFL- CSR, a new accelerator project at the Heavy Ion Research Facility in Lanzhou (HIRFL), is a multipurpose Cooling Storage Ring system which consists of a main ring (CSRm) and an experimental ring (CSRe). Beams from HIRFL will be accumulated and accelerated in CSRm, and then transported to CSRe for internal target experiments. The layout, major parameters and main functions of the CSR were described.     

SSC高频腔数值模拟及分析

SSC加速电压的提高对于HIRFL整体运行水平的提高具有重要的意义.利用三维电磁场计算程序MAFIA对SSC高频腔体作了更为细致的分析,重新计算了腔体的主要参数,结合运行中的实际结果,对电压提高的可行性进行了初步分析;由于在大功率运行状态下,少量的功率损失都可能影响腔–机系统的稳定性,所以同时利用MAFIA计算得到的结果,对功率耦合系统重新做了分析,得到了功率反射的理论极值及改进方案.     

重离子束治癌

本文回顾了辐射治癌的历史发展和国内外动态，讨论了重离子束与常规辐射相比在肿瘤治疗上的优势，提出了为治疗应用的重离子束的主要参数以及在兰州重离子研究装置（ＨＩＲＦＬ）拟建的冷却储存环（ＣＳＲ）上建立治疗实验室的初步考虑． Historical background and trends at home and abroad for radiation therapy arelooked back in the paper. The advantages of heavy ion beam in comparision with conventional radiation in tumour treatment are discussed. The main parameters of heavy ion beams fortherapy application and a tentative idea constructing treatment rooms at Cooling StorageRing(CSR) of Heavy Ion Research Facility in Lanzhou (HIRFL) are proposed.     

HIRFL与CSR的匹配研究

国家重大科学工程HIRFLCSR冷却储存环计划主环CSRm利用已有的HIRFL作为注入器,为了更好地利用HIRFL加速器的能力,对这两台加速器的匹配在原来的初步考虑的基础上进行了较为详细的研究,提出了分别利用HIRFL自己的注入器SFC单独注入到CSR以及SFC加上主加速器SSC注入到CSR的两套方案,既可以提高HIRFL与CSR的总传输效率,又可以在SFC与CSR联合运行的同时使SSC与另建的小回旋加速器组合加速质子,从而充分提高HIRFL的运行效率.     

重离子加速器冷却储存环高频腔体设计

 通过二维高频电磁场的计算，设计了兰州重离子加速器冷却储存环（HIRFL–CSR）的铁氧体加载腔，给出了高频系统主要参数及加速电场的分布。     

Schottky探针研制与测试研究

利用Schottky质谱仪进行远离β稳定线核质量测量研究是九五国家大科学工程兰州重离子加速器冷却储存环上的一个重要研究方向. 简要分析了Schottky探针的工作原理和利用 Schottky质谱仪进行质量测量， 给出了对用于HIRFL CSR束流诊断与测量的Schottky探针的研制与测试结果. he mass measurement of the nuclides far from the β stability by using Schottky mass spectrometry is an important aspect of the studies on HIRFL CSR. The principle of Schottky pick up and the method and prospect of Schottky mass spectrometry are also briefly analyzed. The Schottky pick up designed for the system of diagnostics and measurement of HIRFL CSR and also the test results are given.     

HIRFL-CSR六极磁铁数字电源研究与设计

设计了一台用于兰州重离子加速器HIRFL-CSR的六极磁铁数字电源, 该电源以H桥变换器为主拓扑结构电路, 采用Cyclone II FPGA作为核心硬件, 以Verilog语言实现了全数字化的PI调节算法。 电源输出电流达到了340 A, 直流电流稳定度达到了3.14×10-5, 达到了1×10-4的设计指标。One digital power supply was designed for the sextupole magnets of Cooler Storage Ring of the Heavy Ion Research Facility in Lanzhou (HIRFL CSR). It adopts H Bridge convertor as the main topology circuit and Cyclone II FPGA as the main hardware, and has realized fully digitized PI regulation arithmetic by Verilog language. The peak current of the power supply reaches 340 A and the stability approaches 3.14×10-5. Finally the power supply has achieved the designed specification of 1×10-4.     

HIRFL上的中、低能重离子物理基础和应用研究

本文简介HIRFL上中、低能重离子物理基础和应用研究的主要进展;着重介绍三个方面的研究:中能HIC和热核性质的研究,远离稳定线核的合成和研究,重离子束应用,并概述近期实验研究规划的初步建议。 The experimental studies and achievements recently made at the Heavy Ion ResearchFacility of Lanzhou(HIRFL) are reviewed with an emphasis on the three research fields: the study of intermediate energy heavy ion collision and properties of hot nuclei, the synthesis and study of nucleifar from stability, and the applications of heavy ions. A research program for the near future is alsobriefly introduced.     

SFC轴向注入系统和中心区的研究和设计

介绍了在HIRFL注入器SFC上进行的中心区、聚束器系统和轴向注入束运线的设计、加工和调试结果.中心区的设计采用了两种注入半径及相应的两套螺旋式静电偏转镜,解决了高频电压在某些工作区域偏低及三次谐波加速时轴向注入线上空间电荷效应较为严重的问题.新的锯齿波聚束器系统不仅可以提高聚束效率,而且还提出了采用半频聚束模式以提高SFC与主加速器SSC?的纵向匹配效率.新设计的轴向注入束运线配备了两台在线ECR离子源,提高了电荷态分辨能力和注入相空间匹配能力,在提高注入效率的同时还改善了离子源及束运线的工作环境和调束手段.     

兰州重离子加速器冷却储存环

 兰州重离子加速器冷却储存环HIRFL-CSR，是一个多用途、多功能的双冷却储存环同步加速器系统，由主环CSRm和实验环CSRe构成，并以兰州重离子级联回旋加速器HIRFL作注入器。CSR利用高频变谐波的方法，将重离子束的能量从7～25 MeV/u同步加速到２00～1 000 MeV/u，同时利用重离子储存环中空心电子束冷却技术将束流品质提高１个数量级，并通过储存环的快引出及慢引出，提供多种类的重离子束以及放射性次级束(RIBs)，以开展范围更广精度更高的物理实验。该装置于2007年投入运行，已取得了重要的运行结果，如实现了剥离注入与多圈注入、空心电子束对重离子束的冷却与累积、变谐波宽能区同步加速、等时性环型谱仪、RIBs的产生收集与ToF高分辨质量测量以及高能重离子束的变能慢引出等。