Electron Cloud Effects in High-Intensity Proton Accelerators

One of the primary concerns in the design and operation of high-intensity proton synchrotrons and accumulators is the electron cloud and associated beam loss and instabilities. Electron-cloud effects are observed at high-intensity proton machines like the Los Alamos National Laboratory's PSR and CERN's SPS, and investigated experimentally and theoretically. In the design of next-generation high-intensity proton accelerators like the Spallation Neutron Source ring, emphasis is made in minimizing electron production and in enhancing Landau damping. This paper reviews the present understanding of the electron-cloud effects and presents mitigation measures

On the use of the cumulative strain energy density for fatigue life assessment in advanced high-strength steels

Publisher Copyright: © 2022 Elsevier LtdIn this paper, the applicability of the cumulative strain energy density is explored as a fatigue indicator parameter for advanced high-strength steels subjected to strain-controlled conditions. Firstly, the cyclic stress–strain responses of nine steels, selected from three multiphase families, encompassing different elemental compositions and different heat treatment routes, were studied. Then, the predictive capabilities of the proposed model were compared with those of other strain-based and energy-based approaches. It was found that the cumulative strain energy density decreases as the strain amplitude increaes. It was also found that the cumulative strain energy density and the fatigue life can be related via a power function. In addition, the relationship between the cumulative strain energy and the fatigue life was not significantly affected by the elemental composition or the heat treatment route. Finally, the fatigue lives computed through the cumulative strain energy density concept were close to those of the other models but were slightly more conservative.publishersversionpublishe

Twenty Years After the Velvet Revolution: Shifts in Czech Adolescents’ Perceptions of Family, School, and Society

Families and schools are traditionally seen as substantial socialization agents forming adolescents’ social values and their views of society. Special attention is paid to the question whether the relative importance of these influences remains stable in times of major social changes. In this study, two different generations of Czech middle adolescents are compared: (a) the “post-totalitarian” generation that grew up in the last decade of the communist regime and entered adolescence during the time of rapid political and socioeconomic changes (data collected in 1995) and (b) the current generation without personal experience with the communist regime, raised in a stable democratic society (data collected in 2010). Both groups of participants (total N = 2,127, aged from 14 to 17 years) were administered an identical questionnaire. First, we examined the changes in adolescents’ perception and evaluation of the society over the last 15 years. Today’s adolescents perceive society more as a community and their future orientations are more focused on materialistic and less on environmental values. While the emotional relationship between the children and parentsremains the same, adolescents learn a somewhat different message in the family, emphasizing self-reliance. School environment is perceived more as positive and engaging than 15 years ago. Second, we predicted adolescents’ social views and values from their assessment of family and school environment. Our results show that the effect of parental values on adolescents’ value orientations is higher in the current generation. Positive school environment contributes to the development of socially responsible orientations despite the changes in society

Calculation of resonances in the Coulomb three-body system with two disintegration channels in the adiabatic hyperspherical approach

The method of calculation of the resonance characteristics is developed for the metastable states of the Coulomb three-body (CTB) system with two disintegration channels. The energy dependence of K-matrix in the resonance region is calculated with the use of the stabilization method. Resonance position and partial widths are obtained by fitting the numerically calculated K(E)-matrix with the help of the generalized Breit-Wigner formula.Comment: Latex, 11 pages with 5 figures and 2 table

Evolution of spectral properties along the O(6)-U(5) transition in the interacting boson model. I. Level dynamics

We investigate the evolution of quantal spectra and the corresponding wave functions along the [O(6)-U(5)]$\supset$O(5) transition of the interacting boson model. The model is integrable in this regime and its ground state passes through a second-order structural phase transition. We show that the whole spectrum as a function of the Hamiltonian control parameter, as well as structures of all excited states, exhibit rather organized and correlated behaviors, that provide deeper insight into the nature of this transitional path.Comment: 10 pages, 8 figure

Evolution of spectral properties along the O(6)-U(5) transition in the interacting boson model. II. Classical trajectories

This article continues our previous study of level dynamics in the [O(6)-U(5)]$\supset$O(5) transition of the interacting boson model [nucl-th/0504016] using the semiclassical theory of spectral fluctuations. We find classical monodromy, related to a singular bundle of orbits with infinite period at energy E=0, and bifurcations of numerous periodic orbits for E>0. The spectrum of allowed ratios of periods associated with beta- and gamma-vibrations exhibits an abrupt change around zero energy. These findings explain anomalous bunching of quantum states in the E$\approx$0 region, which is responsible for the redistribution of levels between O(6) and U(5) multiplets.Comment: 11 pages, 7 figures; continuation of nucl-th/050401