1,721,112 research outputs found
Analysis of switching times statistical distributions for perpendicular magnetic memories
No full textDesign and high-power test of a short prototype of high gradient S-band accelerating structure for the FERMI free electron laser linac upgrade
No full textLocated on the site of the Elettra Sincrotrone in Trieste, Italy, the FERMI free-electron laser (FEL) is a user facility fed by a 1.5 GeV, 10 to 50 Hz, S-band radio-frequency linear accelerator (linac). The FEL is based on an external laser seeding scheme which allows lasing down to a fundamental wavelength of 4 nm. In order to achieve shorter wavelengths and improved beam quality, a high gradient upgrade to the facility has been proposed which will extend the current capabilities of the system allowing the generation of beams up to 1.8 GeV while keeping breakdown rates low enough for high machine up-time. This article presents the detailed RF analysis of a 3.0 m S-band, high gradient (HG) structure designed for the new FERMI linac upgrade. This HG structure is designed to provide a reliable accelerating gradient of 30 MV/m with a very low breakdown rate. To ensure the low breakdown rate, Electric-Coupled (EC) RF couplers, also known as waveguide couplers, were designed for the HG structure. To demonstrate the reliability and feasibility of the upgrade plan, a short prototype was built in collaboration with Paul Scherrer Institute (PSI), Switzerland. Using a newly commissioned S-band cavity test facility, the short prototype was successfully conditioned to an accelerating gradient of 40 MV/m with a pulse length of 600 ns at a breakdown rate of 8×10−8 bpp. A comprehensive overview of the testing facility, its data processing tools and the conditioning of this short prototype will be illustrated. Concluding the paper is a visual inspection of the cells for signs of damage resulting from RF breakdown during the high power testing
Micromagnetic study of statistical switching in magnetic tunnel junctions stabilized by perpendicular shape anisotropy
No full text
Midpoint geometric integrators for inertial magnetization dynamics
No full textWe consider the numerical solution of the inertial version of Landau-Lifshitz-Gilbert equation (iLLG), which describes high-frequency nutation on top of magnetization precession due to angular momentum relaxation. The iLLG equation defines a higher-order nonlinear dynamical system with very different nature compared to the classical LLG equation, requiring twice as many degrees of freedom for space-time discretization. It exhibits essential conservation properties, namely magnetization amplitude preservation, magnetization projection conservation, and a balance equation for generalized free energy, leading to a Lyapunov structure (i.e. the free energy is a decreasing function of time) when the external magnetic field is constant in time. We propose two second-order numerical schemes for integrating the iLLG dynamics over time, both based on implicit midpoint rule. The first scheme unconditionally preserves all the conservation properties, making it the preferred choice for simulating inertial magnetization dynamics. However, it implies doubling the number of unknowns, necessitating significant changes in numerical micromagnetic codes and increasing computational costs especially for spatially inhomogeneous dynamics simulations. To address this issue, we present a second time-stepping method that retains the same computational cost as the implicit midpoint rule for classical LLG dynamics while unconditionally preserving magnetization amplitude and projection. Special quasi-Newton techniques are developed for solving the nonlinear system of equations required at each time step due to the implicit nature of both time-steppings. The numerical schemes are validated on analytical solution for macrospin terahertz frequency response and the effectiveness of the second scheme is demonstrated with full micromagnetic simulation of inertial spin waves propagation in a magnetic thin-film
Deformations of polarizable fluids subject to stationary electromagnetic fields
No full textIEEE TRANSACTIONS ON MAGNETIC
Cellular Networks for Simulating Evolution Partial Differential Equations
No full textFrontiers in Artificial Intelligence and Applications Serie
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