15 research outputs found
Gallone Samples Archive: a resource for Cultural Heritage studies
A vast collection of samples from artworks. A unique resource for future research in the field of
conservation: investigating samples, implementing more advanced techniques
Optimisation Study of the Fabry-PĂ©rot Optical Cavity for the MARIX/BRIXS Compton X-Ray Source
We present the study of the optimization of the optical cavity parameters, in order to maximise the flux of scattered photons in the Compton scattering process. In the optimisation, we compensate the losses of the photon number due to the elliptical shape of the laser pulse in optical cavity with a high focusing electron beam
Temperature-dependent criticality in random 2D Ising models
We consider 2D random Ising ferromagnetic models, where quenched disorder is
represented either by random local magnetic fields (random-field Ising model) or by a random
distribution of interaction couplings (random-bond Ising model). In both cases, we first
perform zero- and finite-temperature Monte Carlo simulations to determine how the critical
temperature depends on the disorder parameter. We then focus on the reversal transition
triggered by an external field and study the associated Barkhausen noise. Our main result
is that the critical exponents characterizing the power law associated with the Barkhausen
noise exhibit a temperature dependence in line with existing experimental observations
Magneto-optical Kerr effect (MOKE) measurements with uniform laser profiles
The probability distribution of the amplitude DeltaM of Barkhausen jumps during magnetization
reversal in thin films can be measured with optical techniques since each jump produces a variation DeltaI of the laser beam intensity used to probe magnetization. Here we present a theoretical model which demonstrates that no distortion takes place if P(DeltaM) is a power law P(DeltaM)=DeltaM^(-alpha) with alpha >= 1.0. This prediction has been experimentally confirmed by measuring P(DeltaI) in the same experimental conditions but in two different ways: first with a Gaussian and then with a constant intensity laser profile. In both cases the same power-law distribution has been observed with alpha=1
Dynamic Phase Transition in 2D Ising Systems: Effect of Anisotropy and Defects
We investigate the dynamic phase transition in two-dimensional Ising models whose equilibrium characteristics are influenced by either anisotropic interactions or quenched defects. The presence of anisotropy reduces the dynamical critical temperature, leading to the expected result that the critical temperature approaches zero in the full-anisotropy limit. We show that a comprehensive understanding of the dynamic behavior of systems with quenched defects requires a generalized definition of the dynamic order parameter. By doing so, we demonstrate that the inclusion of quenched defects lowers the dynamic critical temperature as well, with a linear trend across the range of defect fractions considered. We also explore if and how it is possible to predict the dynamic behavior of specific magnetic systems with quenched randomness. Various geometric quantities, such as a defect potential index, the defect dipole moment, and the properties of the defect Delaunay triangulation, prove useful for this purpose