Phase diagram of a 2D Ising model within a nonextensive approach

In this work we report Monte Carlo simulations of a 2D Ising model, in which the statistics of the Metropolis algorithm is replaced by the nonextensive one. We compute the magnetization and show that phase transitions are present for q ≠ 1. A q - phase diagram (critical temperature vs. the entropic parameter q) is built and exhibits some interesting features, such as phases which are governed by the value of the entropic index q. It is shown that such phases favors some energy levels of magnetization states. It is also shown that the contribution of the Tsallis cutoff is capital to the existence of phase transitions.     

John Bell and the Identical Twins

I present a biographical profile of John S. Bell based upon extensive interviews I had with him. I present Bell‘s views on the quantum theory along with a simple explanation of his identity. Jeremy Bernstein is Professor Emeritus of Physics at the Stevens Institute of Technology and a former staff writer for The New Yorker.     

Investigation of debris dynamics from laser-produced tin plasma for EUV lithography light source

The dynamics of debris from the laser-produced tin (Sn) plasma was investigated for an extreme ultraviolet light source in order to establish the guideline for the optimum design of a mitigation system, such as a mass-limited target. The dissemination of the Sn atoms from the different shapes of a wire and a mass-limited droplet target were investigated using the laser-induced fluorescence (LIF) imaging method. The Sn droplet targets with a diameter in the range of 5 to 17 μm were prepared by a new droplet generating technique using a pulsed laser. There was a large difference in the angular distribution of Sn atoms in the plane parallel and perpendicular to the wire axis, indicating the curvature of the target surface governed the angular distribution of the ablated species. The spatial distributions of Sn atoms from the droplet targets were similar to those from the curved surface of the wire targets. The ablation dynamics of the droplet observed by a high-speed imaging camera is also discussed.     

Reduction of surface coverage of finite systems due to geometrical steps

The coverage of vicinal, stepped surfaces with molecules is simulated with the help of a two-dimensional Ising model including local distortions and an Ehrlich-Schwoebel barrier term at the steps. An effective two-spin model is capable to describe the main properties of this distorted Ising model. It is employed to analyze the behavior of the system close to the critical points. Within a well-defined regime of bonding strengths and Ehrlich-Schwoebel barriers we find a reduction of coverage (magnetization) at low temperatures due to the presence of the surface step. This results in a second, low-temperature transition besides the standard Ising order-disorder transition. The additional transition is characterized by a divergence of the susceptibility as a finite-size effect. Due to the surface step the mean-field specific heat diverges with a power law.     

High-sensitivity bunch charge monitor

The conceptual design for a high-sensitivity bunch charge monitor is presented. The device operates with short, spaced bunches. For optimal performance, the bunch duration should be less than 10 ns and bunch spacing should be more than 100 ns. Sensitivity of the monitor is close to 10 V per nanocoulomb. The equivalent scheme and the output signal shape are also presented. Such a monitor seems to be promising for the bunch charge measurements of beams like those in TESLA or ILC projects. The text was submitted by the authors in English.     

Directional terahertz radiation through groove-assisted hole array

The authors theoretically demonstrate the terahertz beam shaping with metallic subwavelength holes array surrounded by concentric periodic grooves. High transmission and directional radiation can be obtained simultaneously for the resonant excitation of the surface wave in the combined structure. Finite-difference time-domain simulation results shows that the transmission mainly depends on the lattice constant of hole array and the features of incident surface around it, while the far-field angle distribution is dominated by the details of the output surface. This compact beam shaping structure is hoped to serve as a basic device for future terahertz systems.     

Strong water repellency effect on SiO<Subscript>2</Subscript> films processed at a nanometric scale

The present study deals with the creation of nano-rough surfaces with stable and controlled high hydrophobicity. These surfaces were obtained by combining the ion track etching technique with a simple functionalization by grafting perfluoroctyltrichlorosilane (PFOTS) molecules. Surface morphology was investigated by AFM observations which evidenced a self-affine fractal structure with a fractal dimension D_f ~ 2.6. The study of the wetting properties of these surfaces allowed to elucidate the conditions for observing a high hydrophobicity phenomenon and to predict the contact angle values for surfaces designed at a nanometric scale.     

Nucleon charge exchange on the deuteron: A critical review

The existing experimental data on the d(n, p)nn and d(p, n)pp cross-sections in the forward direction are reviewed in terms of the Dean sum rule. It is shown that the measurement of the ratio of the charge exchange on the deuteron to that on the proton might, if taken together with other experimental data, allow a direct construction of the np → np scattering amplitude in the backward direction with few ambiguities. Communicated by T. Hennino