Anomalous stopping of laser-accelerated intense proton beam in dense ionized matter

Ultrahigh-intensity lasers (10$^{18}$-10$^{22}$W/cm$^{2}$) have opened up new perspectives in many fields of research and application [1-5]. By irradiating a thin foil, an ultrahigh accelerating field (10$^{12}$ V/m) can be formed and multi-MeV ions with unprecedentedly high intensity (10$^{10}$A/cm$^2$) in short time scale ($\sim$ps) are produced [6-14]. Such beams provide new options in radiography [15], high-yield neutron sources [16], high-energy-density-matter generation [17], and ion fast ignition [18,19]. An accurate understanding of the nonlinear behavior of beam transport in matter is crucial for all these applications. We report here the first experimental evidence of anomalous stopping of a laser-generated high-current proton beam in well-characterized dense ionized matter. The observed stopping power is one order of magnitude higher than single-particle slowing-down theory predictions. We attribute this phenomenon to collective effects where the intense beam drives an decelerating electric field approaching 1GV/m in the dense ionized matter. This finding will have considerable impact on the future path to inertial fusion energy.Comment: 8 pages, 4 figure

Energy loss enhancement of very intense proton beams in dense matter due to the beam-density effect

Thoroughly understanding the transport and energy loss of intense ion beams in dense matter is essential for high-energy-density physics and inertial confinement fusion. Here, we report a stopping power experiment with a high-intensity laser-driven proton beam in cold, dense matter. The measured energy loss is one order of magnitude higher than the expectation of individual particle stopping models. We attribute this finding to the proximity of beam ions to each other, which is usually insignificant for relatively-low-current beams from classical accelerators. The ionization of the cold target by the intense ion beam is important for the stopping power calculation and has been considered using proper ionization cross section data. Final theoretical values agree well with the experimental results. Additionally, we extend the stopping power calculation for intense ion beams to plasma scenario based on Ohm's law. Both the proximity- and the Ohmic effect can enhance the energy loss of intense beams in dense matter, which are also summarized as the beam-density effect. This finding is useful for the stopping power estimation of intense beams and significant to fast ignition fusion driven by intense ion beams

Electronic Structures of Cu/S Co-doped/Anatase TiO 2 by First-principles

ABSTRACT The structural parameters, band structures and density of states of anatase TiO2 co-doped with Cu and S were calculated by first-principles based on the density functional theory. The results indicate that the volumes of the co-doped TiO2 increase due to the lattice distortion. The calculated X-ray diffraction pattern shows that the crystal phase of TiO2 is still kept as anatase after Cu and S co-doping. The band gap of TiO2 broadened when S substitutes for Ti or O along with Cu substitutes for Ti. The calculated partial density of states shows that the impurity energy levels mainly come from the Cu 3d and S 3p orbital. The calculated results may provide some theoretical foundations for the photocatalytic activity enhancement of TiO2 co-doped with Cu and S

Allocating Freight Empty Cars in Railway Networks with Dynamic Demands

This paper investigates the freight empty cars allocation problem in railway networks with dynamic demands, in which the storage cost, unit transportation cost, and demand in each stage are taken into consideration. Under the constraints of capacity and demand, a stage-based optimization model for allocating freight empty cars in railway networks is formulated. The objective of this model is to minimize the total cost incurred by transferring and storing empty cars in different stages. Moreover, a genetic algorithm is designed to obtain the optimal empty cars distribution strategies in railway networks. Finally, numerical experiments are given to show the effectiveness of the proposed model and algorithm

Electronic Structures of Cu/S Co-doped/Anatase TiO 2 by First-principles

ABSTRACT The structural parameters, band structures and density of states of anatase TiO2 co-doped with Cu and S were calculated by first-principles based on the density functional theory. The results indicate that the volumes of the co-doped TiO2 increase due to the lattice distortion. The calculated X-ray diffraction pattern shows that the crystal phase of TiO2 is still kept as anatase after Cu and S co-doping. The band gap of TiO2 broadened when S substitutes for Ti or O along with Cu substitutes for Ti. The calculated partial density of states shows that the impurity energy levels mainly come from the Cu 3d and S 3p orbital. The calculated results may provide some theoretical foundations for the photocatalytic activity enhancement of TiO2 co-doped with Cu and S

Feature Selection for Cotton Matter Classification

International audienceFeature selection are highly important to improve the classification accuracy of recognition systems for foreign matter in cotton. To address this problem, this paper presents six filter approaches of feature selection for obtaining the good feature combination with high classification accuracy and small size, and make comparisons using support vector machine and k-nearest neighbor classifier. The result shows that filter approach can efficiently find the good feature sets with high classification accuracy and small size, and the selected feature sets can effectively improve the performance of recognition system for foreign matter in cotton. The selected feature combination has smaller size and higher accuracy than original feature combination. It is important for developing the recognition systems for cotton matter using machine vision technology

Real-time integrated train rescheduling and rolling stock circulation planning for a metro line under disruptions

More and more unexpected events occur in metro systems, which may cause serious disturbances and even disruptions for the operation of trains. This paper studies an integrated train rescheduling and rolling stock circulation planning problem for the complete blockage situations in a metro line. We consider several key practical train operation constraints, including the maximum number of available rolling stocks, the turnaround constraints, the service connection constraints. This problem is viewed as a complex multi-objective mixed integer linear programming (MILP) formulation, where the objectives involve the deviations with respect to the timetable, the (partial) cancellations, and the headway deviations of train services. A two-stage approach is also developed to enhance the computational efficiency, where a smaller-size optimization problem is solved in the first stage, by considering a set of key turnaround stations only, while the original MILP problem is solved in the second stage by fixing some binary variables according to the first stage solution. In addition, we propose a heuristic technique that is based on introducing a new set of constraints to reduce the search space without eliminating potentially good solutions. Comprehensive experiments are investigated based on the practical data of Beijing Subway Lines, where the proposed integrated models and approaches yield much better solutions when compared with a widely used strategy, i.e., holding (waiting at station) strategy and the sequential approach. Moreover, the impacts of the complete blockage locations/durations and the effects of different weight settings in the multi-objective optimization are deeply analyzed