New Strong-Field QED Effects at ELI: Nonperturbative Vacuum Pair Production

Since the work of Sauter, and Heisenberg, Euler and K\"ockel, it has been understood that vacuum polarization effects in quantum electrodynamics (QED) predict remarkable new phenomena such as light-light scattering and pair production from vacuum. However, these fundamental effects are difficult to probe experimentally because they are very weak, and they are difficult to analyze theoretically because they are highly nonlinear and/or nonperturbative. The Extreme Light Infrastructure (ELI) project offers the possibility of a new window into this largely unexplored world. I review these ideas, along with some new results, explaining why quantum field theorists are so interested in this rapidly developing field of laser science. I concentrate on the theoretical tools that have been developed to analyze nonperturbative vacuum pair production.Comment: 20 pages, 9 figures; Key Lecture at the ELI Workshop and School on "Fundamental Physics with Ultra-High Fields", 29 Sept - 2 Oct. 2008, Frauenworth Monastery, Germany; v2: refs updated, English translations of reviews of Nikishov and Ritu

Magnetic properties of electroplated wires coated by ferrofluid

[EN] Low-frequency magnetic properties of ferromagnetic composite wires were studied with and without coating by ferrofluid. Nonmagnetic CuBe wires of 0.1 mm diameter were electroplated with FeCoNi layer of 1 mu m thickness. Magnetization curves were measured in the frequency range of 10 Hz-3 kHz. The composite CuBe/FeCoNi/ferrofluid material shows a hysteretic behaviour in a small field. The hysteresis loop of ferrofluid covered electroplated wire is not a simple sum of the ferrofluid "wire" plus non-covered wire signals. It indicates an interaction between magnetic wire and ferrofluid which can be revealed by low-frequency measurements. The combination "electroplated wire/ferrofluid" can be considered as a new type of composite magnetic material consisting of solid magnetic core coated by complementary liquid magnetic material. Low-frequency measurements in presence of ferrofluid can be a useful method to study magnetic properties of ferromagnets. (C) 2005 Elsevier B.V. All rights reserved.This work was supported by "Ramon y Cajal" grant of UPV-EHU, Spanish MEC and Programa de Incentivo a la Investigacion de la U.P.V.García Miquel, ÁH.; Kurlyandskaya, G.; Levit, V. (2006). Magnetic properties of electroplated wires coated by ferrofluid. Journal of Magnetism and Magnetic Materials. 300(1):55-58. doi:10.1016/j.jmmm.2005.10.147S5558300

Simulation and measurement of a vertical bridgman growth system for β-NiAl crystal

A coordinated theoretical and experimental study of the temperature distributions inside a customized vertical Bridgman system for growing β-NiAl crystal has been conducted. This model accounts for the combined effects of phase change dynamics, coupled heat transfer processes of conduction, convection and radiation, variable material properties,and complex geometry pertaining to the system. Comparisons between numerical predictions and experimental measurements show satisfactory agreement. Important processing parameters such as interface curvatures and temperature gradients across the interface, along with possibilities of improving the solidification process have been explored