Beam-beam effects in space charge dominated ion beams

During low-energy operations below the regular injection energy in the Relativistic Heavy Ion Collider (RHIC), significant beam lifetime reductions due to the beam-beam interaction in conjunction with large space charge tune shifts have been observed. We report on dedicated experiments aimed at understanding this phenomenon as well as preliminary simulation results, and propose alternative working points to improve the beam lifetime in future lowenergy RHIC runs.Comment: 6 pages, contribution to the ICFA Mini-Workshop on Beam-Beam Effects in Hadron Colliders, CERN, Geneva, Switzerland, 18-22 Mar 201

In Search of Exoplanets

Using data archives containing radial-velocity and light intensity information for stars, the DePaul Astrophysics Working Group created MATLAB programs to read and analyze the data in hopes of detecting extrasolar planets. The codes were able to successfully create graphs and obtain orbital periods for potential planets which matched published results. Additional tests were then researched to be used in the future as to confirm new planets

Facilities for the Energy Frontier of Nuclear Physics

The Relativistic Heavy Ion Collider at BNL has been exploring the energy frontier of nuclear physics since 2001. Its performance, flexibility and continued innovative upgrading can sustain its physics output for years to come. Now, the Large Hadron Collider at CERN is about to extend the frontier energy of laboratory nuclear collisions by more than an order of magnitude. In the coming years, its physics reach will evolve towards still higher energy, luminosity and varying collision species, within performance bounds set by accelerator technology and by nuclear physics itself. Complementary high-energy facilities will include fixed-target collisions at the CERN SPS, the FAIR complex at GSI and possible electron-ion colliders based on CEBAF at JLAB, RHIC at BNL or the LHC at CERN.Comment: Invited talk at the International Nuclear Physics Conference, Vancouver, Canada, 4-9 July 2010, to be published in Journal of Physics: Conference Series. http://inpc2010.triumf.ca

Designing for Ballet Classes: Identifying and Mitigating Communication Challenges Between Dancers and Teachers

Dancer-teacher communication in a ballet class can be challenging: ballet is one of the most complex forms of movements, and learning happens through multi-faceted interactions with studio tools (mirror, barre, and floor) and the teacher. We conducted an interview-based qualitative study with seven ballet teachers and six dancers followed by an open-coded analysis to explore the communication challenges that arise while teaching and learning in the ballet studio. We identified key communication issues, including adapting to multi-level dancer expertise, transmitting and realigning development goals, providing personalized corrections and feedback, maintaining the state of flow, and communicating how to properly use tools in the environment. We discuss design implications for crafting technological interventions aimed at mitigating these communication challenges

On the Evolution of Ion Bunch Profile in the Presence of Longitudinal Coherent Electron Cooling

In the presence of longitudinal coherent electron cooling, the evolution of the line-density profile of a circulating ion bunch can be described by the 1-D Fokker-Planck equation. We show that, in the absence of diffusion, the 1-D equation can be solved analytically for certain dependence of cooling force on the synchrotron amplitude. For more general cases with arbitrary diffusion, we solved the 1-D Fokker-Planck equation numerically and the numerical solutions have been compared with results from macro-particle tracking

Comparison of the Spherical Averaged Pseudopotential Model with the Stabilized Jellium Model

We compare Kohn-Sham results (density, cohesive energy, size and effect of charging) of the Spherical Averaged Pseudopotential Model with the Stabilized Jellium Model for clusters of sodium and aluminum with less than 20 atoms. We find that the Stabilized Jellium Model, although conceptually and practically more simple, gives better results for the cohesive energy and the elastic stiffness. We use the Local Density Approximation as well as the Generalized Gradient Approximation to the exchange and correlation energies.Comment: 13 pages, latex, 8 figures, compressed postscript version available at http://www.fis.uc.pt/~vieir

High energy Coulomb-scattered electrons for relativistic particle beam diagnostics

A new system used for monitoring energetic Coulomb-scattered electrons as the main diagnostic for accurately aligning the electron and ion beams in the new Relativistic Heavy Ion Collider (RHIC) electron lenses is described in detail. The theory of electron scattering from relativistic ions is developed and applied to the design and implementation of the system used to achieve and maintain the alignment. Commissioning with gold and 3He beams is then described as well as the successful utilization of the new system during the 2015 RHIC polarized proton run. Systematic errors of the new method are then estimated. Finally, some possible future applications of Coulomb-scattered electrons for beam diagnostics are briefly discussed.Comment: 16 pages, 23 figure

Psychometric assessment and gender invariance of the Polish version of the Gaming Disorder Test

In 2019, Gaming Disorder (GD) was officially recognised by the World Health Organization (WHO) as an official mental health disorder. Currently, the Gaming Disorder Test (GDT) is one of the most widely utilised psychometric tools to assess GD symptoms according to the WHO framework. In this context, the present study aimed to develop the Polish version of the GDT so that this tool can be used within the Polish cultural context. Additionally, the research aimed to ascertain the psychometric properties and appropriateness of the Polish GDT. To achieve this goal, the Polish GDT was investigated in terms of its validity, reliability, and gender measurement invariance through two studies. Accordingly, study 1 recruited a total of 675 gamers (340 female; Meanage = 31.74 years; SD = 7.75 years; range: 15–45 years) and study 2 comprised 575 gamers (275 female; Mage = 29.45 years; SD = 4.25 years; range: 18–35 years). A Confirmatory Factor Analysis (CFA) was used to assess psychometric properties of the Polish GDT. The reliability was assessed using Cronbach’s alpha, McDonald’s omega, and Average Variance Extracted. Gender measurement invariance was investigated using multiple-group CFA, and the unidimensionality was tested using mean of item residual absolute loadings (MIREAL), explained common variance (ECV), and unidimensional congruence (UC). The results of the psychometric analysis showed that the Polish GDT had a one-factor structure. Additionally, the present study demonstrated that the Polish GDT exhibited adequate levels of convergent validity, reliability, and strict gender measurement invariance. These findings suggest that the Polish version of GDT is a suitable psychometric test to assess GD and facilitate research on GD