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Manuscript Title: MF-FIRE: a multifrequency radiative transfer hydrodynamics code.
Authors: G.A. Moses, R.R. Peterson, T.J. McCarville
Program title: MF-FIRE
Catalogue identifier: ACDV_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 36(1985)249
Programming language: Fortran.
Computer: SPERRY 1100/82.
Operating system: SPERRY 1180 TIME/SHARING EXEC.
Program overlaid: yes
RAM: 80K words
Word size: 36
Peripherals: disc.
Keywords: Hydrodynamics radiation, X-ray attenuation, High temperature gas Dynamics, Plasma physics, Laser physics, Inertial confinement.
Classification: 15, 19.7.

Subprograms used:
Cat Id Title Reference
AAHO_v1_0 MIXERG CPC 28(1983)405

Nature of problem:
Inertial confinement fusion target explosions emit energy in the form of neutrons, X-rays, and ionic debris. If the explosion is contained in a vessel filled with gas, the X-rays and ionic debris are stopped in the gas, forming a microfireball. The MF-Fire code computes the attenuation of the target X-rays and debris in this gas and computes the radiation-hydrodynamic response of the microfireball.

Solution method:
The deposition of target x-rays into gas is computed with an expotential attenuation model. A table of x-ray attenuation coefficients for atoms with atomic numbers ranging from 1 to 100 and x-ray energies ranging from 0.01 keV to 1 MeV is supplied with this version of the code. The gas near the target is ionized beyond the level caused by the initial temperature of the gas so that the photoelectric attenuation coefficient is reduced for subsequent x-rays. The x-ray deposition model used by the MF-FIRE code accounts for the reduction in the attenuation coefficient with increasing ionization. The internal energy and momentum transferred from the target debris to the gas are computed from the results of an ion transport code. The results of the ion transport code are fitted to analytic functions, and these analytic functions are used to estimate the rates at which internal energy and momentum are deposited as functions of time and space. The MF-FIRE code simulates the response of a gas confined within a pressure vessel to the deposition of target x-rays and ions by solving the one-dimensional equations of radiation hydrodynamics in Langrangian coordinates using standard finite difference methods. The radiative transfer is treated in the non-equilibrium multifrequency diffusion approximation. An earlier published version of the FIRE code used only a one-temperature approximation for the radiative transfer. Tabulated equations of state and tabulated multifrequency mean Planck and Rosseland opacities are computed using the MIXERG atomic physics code.

The MF-FIRE code assumes one-dimensional symmetry in computing the interaction on the target x-rays and ions with the gas, and also in computing the gas response. The gas can be divided into a maximum of 50 Lagrangian zones, and either planar, cylindrical or sperical geometry can be assumed. Up to 20 frequency groups can be used for the radiative transfer calculation. The gas is assumed to be composed of only one atomic number in computing the x-ray deposition. At present, the model for computing the reduction in the photoelectric attenuation coefficient with increasing ionization is only used if the gas is neon, argon, xenon or nitrogen. To compute the reduction in the attenuation coefficient for additional gases, the binding energy of the K, L and M shell electrons of the neutral gas and the number of electrons in each shell must be added to the subroutine EDATA. Ion stopping data is only supplied for projectile ions Au, Fe, Si, He, T, D, and H in gases of Ar, Xe, and He.

Unusual features:
The MF-FIRE code is written in FORTRAN 66 with two exceptions: (1) NAMELIST input and (2) the manner in which the COMMON blocks are used. The COMMON blocks are listed only at the beginning of the program, where they are equated to INCLUDE statements. Thereafter, the INCLUDE statements are used to represent the COMMON blocks. The use of INCLUDE statements abbreviates the listing of a program that uses the same COMMON blocks in many subroutines, because an INCLUDE statement occupies only one line, whereas a COMMON block might occupy many lines. Most computer systems have a feature similar to the INCLUDE statement described here and it is recommended that the user make use of this feature in his system.

Running time:
The CPU time required to compute the deposition of target x-rays and ions into the gas is minimal compared to the time required to compute the hydrodynamic response. On the Univac 1100/82, the CPU time required to compute the gas response is about 2*10**-3 s/zone*cycle.