Classical Monte-Carlo simulations of x-ray induced electron cascades in various materials

Abstract

In this paper, we present an extension to our code, XCASCADE [Medvedev, Appl. Phys. B 118, 417], that enables to model time evolution of electron cascades following low-intensity X-ray excitation in various materials consisting of elements with atomic numbers Z = 1 − 92. The code is based on a classical Monte-Carlo scheme and uses atomistic cross sections to describe electron impact ionization. The new extended version, XCascade-3D, also tracks the electron trajectories with 3D spatial resolution. This model takes into account anisotropic scattering of electrons on atoms. We show that the calculated electron ranges in various materials are in a good agreement with the available data, confirming the potential for high accuracy applications at FEL pulse diagnostics.

Mechanism of single-shot damage of Ru thin films irradiated by femtosecond extreme UV free-electron laser

“…In this part we describe the XCASCADE(3D) [22] and the TTM [23] that are used to simulate the interaction of the XUV femtosecond laser pulse with a thin Ru film. Within the XCASCADE(3D) approach, the target is assumed to be a homogeneous arrangement of atoms (atomic approximation) with a density corresponding to the chosen material.…”

“…In an elastic scattering event, an incident electron scatters on an atom without energy loss, so only the direction of electron propagation changes. The scattering angle of an incident electron in both scattering processes is calculated using the anisotropic scattering scheme, described in [22]. The scattering angle of the impact-ionized electron follows from the momentum conservation law.…”

“…All photo-as well as secondary electrons are traced until their energy falls below a cut-off energy, which is chosen to be 10 eV [22,38]. As soon as an electron loses its energy below this cut-off, it is considered as a slow electron thermalized in the conduction band of the material.…”

“…In the present work, apart from the experimental study, we use a combined computational approach to describe the interaction of XUV FEL femtosecond pulses with a Ru film. The first stage mentioned above, non-equilibrium electron kinetics induced by XUV light, is simulated with the classical Monte Carlo code XCASCADE(3D) [22]. The code models the absorption of XUV photons by the target and follows the temporal and spatial evolution of the electron cascades produced upon photoabsorption.…”

Modeling of XUV-induced damage in Ru films: the role of model parameters

“…In this paper, we analyze the model parameters of Ru as a material that is still poorly studied in the field of ultrafast lasermatter interaction despite its promising applications as just mentioned. The evolution of electron and lattice temperatures is calculated with our combined approach using the XCASCADE(3D) Monte Carlo (MC) code [24,25] and the two-temperature model (TTM) [26,27]. The influence of a particular choice of model parameters on the results of our calculations is investigated in order to determine which parameters play the most important role in the phenomenon of XUV single-shot damage.…”