Calculations of particle and heavy ion interactions with space shielding materials using the SHIELD-HIT transport code

Spectra of secondary particles produced by nucleus–nucleus interactions and heavy-ion interactions in the extended targets of interest for space research were calculated using the Monte Carlo code SHIELD-HIT. This code simulates the interactions of hadrons and atomic nuclei of arbitrary charge and mass number (Z,A) with complex extended targets in a wide energy range, from 10 GeV/u down to 1 MeV/u, and to thermal energies in the case of neutrons. Inelastic nuclear reactions in SHIELD-HIT are simulated using the Russian models of nuclear reactions. The total reaction cross sections evaluated by these models are discussed for proton and carbon interactions with different nuclei in a wide energy range. Production of secondary neutrons and charged secondary particles from the thick targets of lead, water and PMMA irradiated by ⁴He, ¹²C and ²⁸Si ions of different energies was calculated and compared with the experimental data. The results obtained by SHIELD-HIT are in reasonable agreement with experiments and are promising for further applications in space research.     

PHITS—a particle and heavy ion transport code system

The paper presents a summary of the recent development of the multi-purpose Monte Carlo Particle and Heavy Ion Transport code System, PHITS. In particular, we discuss in detail the development of two new models, JAM and JQMD, for high energy particle interactions, incorporated in PHITS, and show comparisons between model calculations and experiments for the validations of these models. The paper presents three applications of the code including spallation neutron source, heavy ion therapy and space radiation. The results and examples shown indicate PHITS has great ability of carrying out the radiation transport analysis of almost all particles including heavy ions within a wide energy range.     

蒙特卡罗粒子输运程序JMCT研制

介绍了具有自主知识产权的蒙特卡罗(MC)粒子输运程序JMCT的初步研制成果。JMCT基于三维组合几何支撑软件框架JCOGIN,采用模块化,分成多层管理结构,可处理多群碰撞和连续能量碰撞,可进行粒子并行和区域分解并行两种并行方法,并具有良好的可扩展性和高速通信技术,同时配有可视化建模前处理软件。介绍了JMCT采用的多群物质碰撞机制,展示了程序模拟计算测试模型的结果,与MCNP程序计算结果一致。JMCT串行计算速度相比MCNP提高了约3 倍;在20 480个处理器核上模拟2109样本,并行效率可达70%。     

蒙特卡罗粒子输运程序JMCT研制

介绍了具有自主知识产权的蒙特卡罗(MC)粒子输运程序JMCT的初步研制成果。JMCT基于三维组合几何支撑软件框架JCOGIN,采用模块化,分成多层管理结构,可处理多群碰撞和连续能量碰撞,可进行粒子并行和区域分解并行两种并行方法,并具有良好的可扩展性和高速通信技术,同时配有可视化建模前处理软件。介绍了JMCT采用的多群物质碰撞机制,展示了程序模拟计算测试模型的结果,与MCNP程序计算结果一致。JMCT串行计算速度相比MCNP提高了约3 倍;在20 480个处理器核上模拟2109样本,并行效率可达70%。     

Multicomponent transport theoretical approach to ultrarelativistic heavy ion collisions

A new theoretical model is introduced which is able to describe the initial compression and thermalization stage of an ultrarelativistic heavy-ion collision in a hydrodynamical three-flow picture. The first and second fluid is attributed to the nucleons of target and projectile, while a third component is introduced in order to take into account the gradual thermalization of the incoming flow. Based on relativistic transport theory, hydrodynamic equations of motion are derived for each component including transitions of target and projectile nucleons to the thermalized matter component as well as mutual deceleration accompanied with gradual heat transfer between the components. Hence, the multicomponent formalism contains the former two fluid approach as a limiting case.     

Role of single particle transfer in heavy ion fusion

Fusion excitation functions in heavy ion collision have been calculated taking into account the effect of random transfer of single particles in a classical dynamical model. The model has been applied to fusion of ¹⁶O+²⁷Al and ⁴⁰Ar +¹⁰⁹Ag. The transfer does not affect the low energy fusion excitation function but the effect of transfer is appreciable for high energies.     

Mass transport and energy equilibration in heavy ion collisions

The lack of mass drift observed in Kr-induced collisions is explained assuming energy and particle transfer from the light to the heavy fragment during the equilibration stage in asymmetric heavy-ion reactions. Transferred energy and particle number can be estimated from the interfragment thermal equilibrium distribution provided the initial partition is known which we calculate within a semiclassical theory based on TDHF. The experimental findings are consistent with the theoretical predictions. In particular, the experimental mass drift as function of total kinetic energy loss is quantitatively described within a modified diffusion model which takes into account the mass exchange prior to the transport stage.     

Nucleon transport processes in fission and heavy ion reactions

The nucleon exchange process between two nuclei in close proximity and its application to an explanation of fragment mass and charge distributions in fission and in heavy ion deep inelastic collisions are reviewed. An analysis of the measured correlations between the energy loss from relative motion and the fragment mass and charge variances in the heavy ion deep inelastic collisions is presented. The recent data on fragment mass and charge variances as a function of the fragment kinetic energy in thermal neutron induced fission of²³⁵U, lends added support to the hypothesis that the nucleon transport process plays a similar role both in fission and in heavy ion deep inelastic collisions.     

Inertia effects in the mass transport of heavy ion reactions

The general trend of the multi differential cross section plots for the products obtained from the dissipation collisions of the three systems, forming almost the same composite systems but with different degrees of mass asymmetry in the entrance channel,⁵²Cr (261 MeV)+⁵⁶Fe,⁴⁰Ca (182 MeV)+⁶⁴Ni and¹⁶O (187 MeV)+⁹²Mo, were analysed in the frame of the Diffusion Model, assuming that the intermediate system decays with a statistical life time. A fairly good agreement has been obtained between the calculated multi differential plots and the experimental ones. The half life time of the composite systems seem to depend on the mass asymmetry of the entrance channel.     

Thermal gas models and particle production in heavy ion collisions

A systematic study of particle production in nuclear S–S and S–W collisions at 200 GeV/A is presented within the context of an equilibrium interacting hadron gas model. It is shown that the results for strange particle multiplicities and for non-strange baryons obtained in the NA35 and WA85 experiments can be well described in terms of the considered model.     

蒙特卡罗粒子输运软件JMCT抽样工具库设计

为通用型蒙特卡罗粒子输运程序JMCT设计了抽样工具库,通过两种技术途径提供各分布的抽样。一是针对各种常见分布提供特定抽样子程序;二是提供一个通用型的抽样子程序,可以实现任意离散分布和任意一维有限区间上连续分布的自动抽样。在设计任意一维有限区间上连续分布的自动抽样工具时利用了部分开源代码,利用其功能提供给用户最大的方便性。对抽样工具库的检验表明,其可以正确、方便地实现各种输运模拟中常见分布的抽样。     

Charged particle fluctuation as signal of the dynamics in heavy ion processes

We compare the dispersion of the charges in a central rapidity box according to the dual parton model with the predictions of statistical models. Significant deviations are found in heavy ion collisions at RHIC and LHC energies. Hence the charged particle fluctuations should provide a clear signal of the dynamics of heavy ion processes. They should allow one to directly measure the degree of thermalization in a quantitative way. Received: 7 November 2000 / Revised version: 4 September 2001 / Published online: 5 October 2001     

Quantum-coherent transport of a heavy particle in a fermionic bath

In this review, a detailed discussion of the behaviour of a heavy particle interacting with a Fermi sea is given. Particular emphasis is put on the issue of how strong correlations influence coherence and transport of the particle. First, we investigate the question of whether the heavy particle is a well defined quasiparticle at low temperatures. While in one dimension ( D = 1) and at a van Hove singularity in D = 2 the coherence of the particle is destroyed, the quasiparticle weight is finite in higher dimensions. The most important transport quantity is the diffusion constant or mobility of the heavy particle. We are able to describe both the well known high-temperature properties and the cross-over to the lowest temperatures in a unified approximation scheme based on a self-consistent evaluation of an effective action. Two strong-correlation effects of independent origin are discussed. The first arises if the scattering of the fermions from the heavy particle is nearly resonant, that is, if one of the scattering phase shifts δ is close to π/2. In this regime an anomalous exponent is observed in the temperature dependence of the mobility μ(T). In D = 3, for instance, the mobility is proportional to T^-3/2 rather than to T^-2. The second effect is a giant mass renormalization in the case of a large particle. In this situation, the low-temperature effective mass M* increases up to an exponentially large value, M* exp[c(r/λF)³], where r is the effective radius of the particle, λF the Fermi wavelength and c a non-universal constant of order one.     

Direct mechanisms of fast light particle formation in heavy ion collisions

Two direct mechanisms are considered for the heavy ion collisions which lead to fast α-particle emission: α-particle knock on by the incident ion and heavy fragment stripping of this ion. It is demonstrated that stripping mechanism allows to reproduce all the experimental characteristic features of the process except the cross-section dependence on α-particle separation energy in the target. Knock on process reproduces this feature as well. It is pointed that the analysis of experimental data on the hard part of α-particle spectrum allows to gain a unique information on the properties of the strongly rotating nuclei produced in these reactions.     

Catapult mechanism for fast particle emission in fission and heavy ion reactions

The fission process of slabs of nuclear matter is modelled in TDHF approximation by adding an initial collective velocity field to the static self-consistent solution. In dependence on its amplitude either large amplitude density oscillations are excited or fission occurs. The final disintegration of the slab proceeds on a time scale of 10^?22s and is characterized by a sharp peak in the actual velocity field in the region of the “snatching” inner low density tails. A characteristic time later corresponding to the transit time of a nucleon across the fragment with mean velocity being the Fermi velocity plus twice the maximum “snatching” velocity, a low density lump correlated with a peak in the velocity field emerges in front of the fragments. We call these particles “catapult particles”. Recent experimental results possibly provide evidence for catapult neutrons in low-energy fission. We also speculate on the significance of the catapult mechanism for fast particle emission in the exit channel of heavy ion reactions.     

Collision geometry and particle production in high energy heavy ion collision experiments

An overview of research status of soft physics in high energy heavy-ion collision experiments and recent experimental results are presented.This paper includes four parts:1)Theoretical predictions of quarkgluon plasma and introduction for high energy heavy ion collision experiments.2)Experimental status on collision geometry.3)Experimental status on particle production.4)Conclusion and outlook for research status of soft physics in LHC/ALICE.     

Collision geometry and particle production in high energy heavy ion collision experiments

An overview of research status of soft physics in high energy heavy-ion collision experiments and recent experimental results are presented. This paper includes four parts: 1) Theoretical predictions of quark-gluon plasma and introduction for high energy heavy ion collision experiments. 2) Experimental status on collision     

A model for continuous particle spectra from light and heavy ion induced reactions

Starting from the Kalbach systematics for preequilibrium angular distributions a model for energy differential cross sections is derived which is based on the assumption of a temperature like distribution of the excitation energy. A discussion for the physical basis is given. The dependences of the temperature like model parameterT are discussed for data from light ion and heavy ion induced reactions.