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

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.Program summaryProgram title: MULTI-fsCatalogue identifier: AEKT_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEKT_v1_0.htmlProgram obtainable from: CPC Program Library, Queenʼs University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 49 598No. of bytes in distributed program, including test data, etc.: 443 771Distribution format: tar.gzProgramming language: FORTRANComputer: PC (32 bits and 64 bits architecture)Operating system: Linux/UnixRAM: 1.6 MiBClassification: 19.13, 21.2Subprograms used: Cat Id: AECV_v1_0; Title: MULTI2D; Reference: CPC 180 (2009) 977Nature of problem: One-dimensional interaction of intense ultrashort (sub-picosecond) and ultraintense (up to 1017 W cm−2) laser beams with matter.Solution method: The hydrodynamic motion coupled to laser propagation and several transport mechanisms is solved in one-dimensional geometry using a fractional step scheme. Fluid motion together with heat diffusion is solved by using an implicit Lagrangian method. Transport by thermal conduction and radiation as well as electron–ion energy transfer are treated in a two-temperature (electron and ion) model covering the wide range from solid state to high temperature plasma. Laser propagation is calculated from the one-dimensional Maxwell equations. Radiation transfer is solved by using the forward-reverse method for a discrete number of frequency groups. Matter properties are interpolated from tables (equations-of-state, ionization, opacities, and emissivities) generated by external codes. An alternative WKB laser deposition package is available to be used for long pulse lasers.Restrictions: The code has been designed for typical conditions prevailing in short pulse (fs–ps time scale) laser–matter interactions at moderate intensities (1012–1017 W cm−2). Although a wider range of situations can be treated, extrapolations to regions beyond this design range need special care.Additional comments: A graphical post processor is included in the package. Its use requires the previous installation of code MULTI2D (see “Subprograms used” above).Running time: 4.8 seconds for the example supplied.

► 1D hydrocode to study the interaction of femtosecond laser pulses with matter.
► Laser intensities up to 1017 W cm−2.
► Laser propagation by solving Maxwell equation.
► Two optional models of electron collision time in warm dense matter.
► Radiation transport solved in multi-group forward/reverse approximation.