MULTI-fs – A computer code for laser–plasma interaction in the femtosecond regime Original Research Article

The code MULTI-fs is a numerical tool devoted to the study of the interaction of ultrashort sub-picosecond laser pulses with matter in the intensity range from 1011 to 1017 W cm−2. Hydrodynamics is solved in one-dimensional geometry together with laser energy deposition and transport by thermal conduction and radiation. In contrast to long nanosecond pulses, short pulses generate steep gradient plasmas with typical scale lengths in the order of the laser wavelength and smaller. Under these conditions, Maxwellʼs equations are solved explicitly to obtain the light field. Concerning laser absorption, two different models for the electron–ion collision frequency are implemented to cover the regime of warm dense matter between high-temperature plasma and solid matter and also interaction with short-wave-length (VUV) light. MULTI-fs code is based on the MULTI radiation-hydrodynamic code [R. Ramis, R. Schmalz, J. Meyer-ter-Vehn, Comp. Phys. Comm. 49 (1988) 475] and most of the original features for the treatment of radiation are maintained.