Formation of hollow heavy ion beams in plasma lens

Hollow cylindrical high-energy heavy ion beams are an efficient driver for target irradiation to achieve highly compressed matter. This paper is devoted to the study of how hollow beams form with the use of a plasma lens. Calculations and measurements were performed with a 200 MeV/amu C⁺⁶ beam.     

The theoretical simulation of magnetized electron beam effects on radially polarized of an annular cylindrical piezoelectric crystal

By using the equilibrium equations for a hollow cylindrical piezoelectric layer in absence of body forces and taking into the account a magnetized electron beam in hollow region of this system the effects of thermal pressure, electrostatic self field and the strength of external magnetic field of a non-relativistic magnetized electron beam column on radially polarized of an annular cylindrical piezoelectric crystal in the steady state are simulated. The electrostatic potential profile in piezoelectric layer due to the mechanical pressure and electrostatic self field of electron beam are studied. Furthermore the graphs of the difference of potential Δϕ between inner and outer surfaces of piezoelectric versus to electron temperature, density of beam and the strength of external magnetic field are presented.     

Structure formation and tearing of an MeV cylindrical electron beam in a laser-produced plasma

The stability of a cylindrical, solid hot electron beam propagating in a high density plasma has been studied using a two-dimensional, hybrid Darwin code. The initially solid beam evolves into a hollow, annular beam due to the Weibel instability and generates strong magnetic fields on both sides of the annular ring. The annular structure subsequently breaks up into several beamlets via a mechanism similar to a tearing instability. It is found that the magnetic fields parallel to the direction of beam propagation also grow due to the tearing process.     

Application of intense ion beams to planetary physics research at the Facility for Antiprotons and Ion Research facility

This paper presents detailed 2D hydrodynamic simulations of implosion of a multi‐layered cylindrical target that is driven by an intense uranium beam. The target is comprised of a thick, high‐Z, high‐ρ cylindrical shell that encloses a sample material (Fe in the present case). Two options have been used for the focal spot geometry: an annular form and a circular form. The purpose of this work is to show that an intense heavy‐ion beam can induce the extreme physical conditions in the sample material similar to those that exist in the planetary cores. In this study, we use parameters of the beam that will be generated at the Facility for Antiprotons and Ion Research (FAIR), Darmstadt, in a few years' time. Production of these high‐energy‐density (HED) samples will allow us to study planetary physics in the laboratory. It is to be noted that planetary physics research is an important part of the FAIR HED physics program. A dedicated experiment named LAboratory PLAnetary Sciences (LAPLAS) has been proposed for this purpose. These simulations show that in such experiments an Fe sample can be imploded to the Earth's core conditions and to those in more massive rocky planets called Super‐Earths. Similarly, implosion of hydrogen and water samples will generate the core conditions of solar and extrasolar hydrogen‐rich gas giants and water‐rich icy planets, respectively. The LAPLAS experiments will thus provide very valuable information on the equation of state and transport properties of matter under extreme physical conditions, which will help scientists understand the structure and evolution of the planets in our solar system as well as of the extrasolar planets.     

Evolution of the Continuous-Atomistic Method for the Simulation of Processes of the Interaction between Heavy Ions and Metals

The evolution of the continuous-atomistic approach to the simulation of processes of the interaction between high-energy heavy ions and metals is presented in this paper. The continuous-atomistic model is described by two different classes of equations, namely, thermal-conductivity equations with a source in the thermal-spike model and equations of motion of material points irradiated with a beam in a model of molecular dynamics. A software package is developed for simulation within the framework of the continuous-atomistic model. The results of simulation of the processes of metal-target irradiation with high-energy heavy ions depending on the parameters of the source function and the electron–phonon interaction coefficient are obtained.     

Focusing properties of concentric piecewise cylindrical vector beam

The focusing properties of a concentric piecewise cylindrical vector beam is investigated theoretically in this paper. The beam consists of three portions with different and changeable phase retardation and polarization. Numerical simulations show that the evolution of the focal shape is very considerable by changing the radius and polarization rotation angle of each portion of the vector beam. And some interesting focal spots may occur, such as two- or three-peak focus, dark hollow focus, ring focus, and two-ring-peak focus. Corresponding gradient force patterns are also computed, and novel trap patterns, including cup shell shape trap with one trap at its each side along axis, rectangle shell shape trap with one trap at its each side, dumbbell optical trap, spherical shell optical trap, may occur, which shows that the concentric piecewise cylindrical vector beam can be used to construct controllable optical tweezers.     

Technical developments for an upgrade of the LEBIT Penning trap mass spectrometry facility for rare isotopes

The LEBIT (Low Energy Beam and Ion Trap) facility is the only Penning trap mass spectrometry (PTMS) facility to utilize rare isotopes produced via fast-beam fragmentation. This technique allows access to practically all elements lighter than uranium, and in particular enables the production of isotopes that are not available or that are difficult to obtain at isotope separation on-line facilities. The preparation of the high-energy rare-isotope beam produced by projectile fragmentation for low-energy PTMS experiments is achieved by gas stopping to slow down and thermalize the fast-beam ions, along with an rf quadrupole cooler and buncher and rf quadrupole ion guides to deliver the beam to the Penning trap. During its first phase of operation LEBIT has been very successful, and new developments are now underway to access rare isotopes even farther from stability, which requires dealing with extremely short lifetimes and low production rates. These developments aim at increasing delivery efficiency, minimizing delivery and measurement time, and maximizing use of available beam time. They include an upgrade to the gas-stopping station, active magnetic field monitoring and stabilization by employing a miniature Penning trap as a magnetometer, the use of stored waveform inverse Fourier transform (SWIFT) to most effectively remove unwanted ions, and charge breeding.     

Acoustic signature of a submarine hull under harmonic excitation

The structural and acoustic responses of a submarine under harmonic force excitation are presented. The submarine hull is modelled as a cylindrical shell with internal bulkheads and ring stiffeners. The cylindrical shell is closed by truncated conical shells, which in turn are closed at each end using circular plates. The entire structure is submerged in a heavy fluid medium. The structural responses of the submerged vessel are calculated by solving the cylindrical shell equations of motion using a wave approach and the conical shell equations with a power series solution. The far-field radiated sound pressure is then calculated by means of the Helmholtz integral. The contribution of the conical end closures on the radiated sound pressure for the lowest circumferential mode numbers is clearly observed. Results from the analytical model are compared with computational results from a fully coupled finite element/boundary element model.     

Analysis of the response of damped cylindrical shells carrying discontinuously constrained beam elements

A simple analysis is presented of the forced vibratory response of a cylindrical shell having a number of axial beams adhered to it by a viscoelastic material layer. The attached beams are identical, closely spaced and distributed around the full circumference of the shell. The excitation is a concentrated vibratory force acting radially at the mid-section on the surface of the shell. The end conditions of the shell and the attached beams are all assumed to be simply supported. The effects of the operational temperature and frequency on the viscoelastic material properties are considered. An experiment was conducted, for comparison, on a damped cylindrical shell suspended in air by lightweight elastic shock cords and driven at the mid-section by an electromechanical vibration shaker. Good correlations between the test data and analytical solutions were obtained over a wide range of frequencies.     

Status of the SHIPTRAP Project: A Capture and Storage Facility for Heavy Radionuclides fromSHIP

The ion trap facility SHIPTRAP is being set up to deliver very clean and cool beams of singly-charged recoil ions produced at the SHIP velocity filter at GSI Darmstadt. SHIPTRAP consists of a gas cell for stopping and thermalizing high-energy recoil ions from SHIP, an rf ion guide for extraction of the ions from the gas cell, a linear rf trap for accumulation and bunching of the ions, and a Penning trap for isobaric purification. The progress in testing the rf ion guide is reported. A transmission of about 93(5)% was achieved. This revised version was published online in July 2006 with corrections to the Cover Date.     

Longitudinal phase-space coating of beam in a storage ring

In this Letter, I report on a novel scheme for beam stacking without any beam emittance dilution using a barrier rf system in synchrotrons. The general principle of the scheme called longitudinal phase-space coating, validation of the concept via multi-particle beam dynamics simulations applied to the Fermilab Recycler, and its experimental demonstration are presented. In addition, it has been shown and illustrated that the rf gymnastics involved in this scheme can be used in measuring the incoherent synchrotron tune spectrum of the beam in barrier buckets and in producing a clean hollow beam in longitudinal phase space. The method of beam stacking in synchrotrons presented here is the first of its kind.     

Scintillation properties of dark hollow beams in a weak turbulent atmosphere

The on-axis scintillation index for a circular dark hollow beam (DHB) propagating in a weak turbulent atmosphere is formulated, and the scintillation properties of a DHB are investigated in detail. The scintillation index for a DHB reduces to the scintillation index for a Gaussian beam, an annular beam and a flat-topped beam under certain conditions. It is found that the scintillation index of a DHB is closely related to the beam parameters and can be lower than that of a Gaussian beam, an annular beam and a flat-topped beam in a weak turbulent atmosphere at smaller waist sizes and longer propagation lengths. PACS 42.25.Bs; 42.68.Ay     

Bessel光束经椭圆环形孔径后的衍射光场

基于菲涅耳衍射积分理论及硬边孔径的复高斯函数展开法导出了Bessel光束经椭圆环形孔径后的光场表达式, 数值模拟了其光场的强度分布. 研究了Bessel光束经椭圆环形孔径后的光场变化及其传播过程; 在实验上利用轴棱锥输出的近似无衍射Bessel光, 通过椭圆环形孔径, 使用电荷耦合器件拍摄得到不同传播距离处的光强分布. 理论结果和实验结果均表明无衍射光束经椭圆环形孔径后会产生空心光束.     

利用HIRFL高能重离子束的核能材料辐照损伤研究

载能重离子与高能中子在材料中能够产生相似的级联碰撞损伤,加之重离子具有大的离位损伤截面和在材料样品中低的感生放射性,载能重离子束成为模拟先进核能装置内部结构材料辐照损伤的重要手段。HIRFL能区的重离子在结构材料中的射程一般远大于晶粒尺寸,因此能够产生材料体损伤,借助小样品技术可以获得材料力学性能变化（尤其辐照脆化）的有用信息,为探讨材料辐照损伤微结构和宏观力学性能变化的关联提供了重要条件。本文简要介绍了近年来我们基于HIRFL高能离子束开展的聚变堆候选材料辐照损伤的研究,包括低活化钢的辐照脆化行为、氧化物弥散强化（ODS）铁素体钢的结构优化对于抗辐照性能的影响、不同载能粒子辐照条件下铁素体/马氏体钢的辐照肿胀数据的关联,以及高能重离子辐照的钨材料中氢同位素的滞留行为。研究表明,结合特殊的测试技术及数据分析方法,高能重离子可作为核能结构材料辐照损伤研究及评估的有效手段。Because of the similarity in cascade damage structure in materials produced by energetic heavy ions and by fast neutrons, and the high displacement rate and low induced radioactivity of samples by heavy ions, heavy ion beam becomes an important tool to simulate radiation damage by energetic neutrons in materials in advanced nuclear energy systems. The ranges of heavy ions provided by HIRFL (Heavy Ion Research Facility in Lanzhou) are generally much larger than the mean dimensions of grains in alloys candidate to advanced nuclear reactors, and is capable of producing radiation damage in bulk scale. It therefore makes possible the evaluation of change of mechanical properties including the radiation induced embrittlement from the irradiated specimens by using miniaturized specimen techniques. In the present paper, we provide an introduction of our recent studies of radiation damage of materials candidate to future fusion reactors by utilizing heavy ion beams in HIRFL.The studies include issues as follows:ductility loss of RAFM steels causes by high-energy Ne ions, impact of oxide dispersoids on the radiation resistance of ODS ferritic steels, correlation of void swelling of ferritic/martensitic steels under different particle irradiation, and behavior of deuterium retention in tungsten under irradiation with high-energy heavy ions. The results show that high-energy heavy ions can be used as a tool to efficiently investigate or evaluate radiation damage in structure materials if combined with some special test techniques and data analysis.     

Generation of a decoherence-free entangled state using a radio-frequency dressed state

We propose the generation of entangled states with trapped calcium ions using a combination of an rf dressed state and a spin-dependent force. By using this method, a decoherence-free entangled state of rf qubits can be directly generated, and ideally its fidelity is close to unity. We demonstrate an rf entangled state with a fidelity of 0.68±0.08, which has a coherence time of more than 200 ms by virtue of the fact that it is an eigenstate with energy gaps between adjacent levels. Using the same technique, we also produce a qutrit-qutrit entangled state with a fidelity of 0.77±0.09, which exceeds the threshold value for separability of 2/3.     

Neutron productions in the fragmentation of relativistic heavy nuclei and formation of a beam of high-energy neutrons

The production of quasimonoenergetic high-energy neutrons at zero angle (0°) in the spallation of relativistic heavy nuclei is discussed by considering the example of the interaction of lead nuclei with light target nuclei. It is shown that this process can be used to generate a beam of high-energy neutrons at existing heavy ion accelerators. At the same time, itmay lead to the appearance of a parasitic neutron beam because of the interaction of the heavy-ion beam used with beam line and experimental setup materials.     

Analysis of transient responses in a laminated piezoelectric cylindrical shell

A hybrid numerical method is proposed for analysis of transient responses in a multilayered piezoelectric cylindrical shell.In the present method,the associated equations of the displacement field and the electro-potential field are developed using an analytical-numerical method.The piezoelectric cylindrical shell is discretized into layered annular elements along the wall thickness direction.The governing equations are determined by Hamilton's Principle considering the coupling between the elastic and elec...     

Heavy-ion irradiation of UBe13 superconductors

We irradiate the heavy fermion superconductors (U,Th)Be₁₃ with high-energy heavy ions. Damage from the ions affects both heat capacity and magnetization measurements, although much less dramatically than in other superconductors. From these data and from direct imaging, we conclude that the irradiation does not create the amorphous columnar defects observed in high-temperature superconductors and other materials. We also find that the damage suppresses the two superconducting transitions of U_0.97Th_0.03Be₁₃ by comparable amounts, unlike their response to other types of defects.     

The SHIPTRAP project: A capture and storage facility at GSI for heavy radionuclides from SHIP

SHIPTRAP is an ion trap facility which is being set up to deliver very clean and cool beams of singly-charged recoil ions produced at the SHIP velocity filter at GSI Darmstadt. SHIPTRAP consists of a gas cell for stopping and thermalizing high-energy recoil ions from SHIP, a rf ion guide for extraction of the ions from the gas cell, a linear rf trap for accumulation and bunching of the ions, and a Penning trap for isobaric purification. The physics programme of the SHIPTRAP facility comprises mass spectrometry, nuclear spectroscopy, laser spectroscopy and chemistry of transeinsteinium elements. This revised version was published online in August 2006 with corrections to the Cover Date.     

Vibration coupling effects between two concentric cylindrical shells through periodic annular plates and entrained fluid

The coupling effects on two concentric cylindrical shells with periodic annular plates as well as entrained fluid were investigated theoretically. Expressions for the reactive forces by the annular plates were derived on the assumption that only quasi-longitudinal waves exist in the annular plates and an analytical expression for the outer shell was developed. Comparisons of numerical results for infinite two-walled cylindrical shell to measured data for a cabin model are in good agreement. Numerical results were presented for analyzing the characteristics of the loadings due to the acoustic fluid and the periodic annular plates, and their influences on the outer shell＇s far field acoustic radiation.