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Manuscript Title: Numerical modelling of a chemical plasma. II. PLASKEM: a program to predict the variation with time of the number densities of chemical species within a plasma.
Authors: S.A. Roberts
Program title: PLASKEM
Catalogue identifier: ACZE_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 18(1979)363
Programming language: Fortran.
Computer: ICL 1906A.
Operating system: GEORGE 4.
RAM: 63K words
Word size: 48
Peripherals: disc.
Keywords: Plasma chemistry, Laser discharge, Plasma physics, Atomic process, Laser physics.
Classification: 15, 19.1.

Subprograms used:
Cat Id Title Reference
ACWX_v1_0 BOLTZ CPC 11(1976)369
ACZD_v1_0 REACS CPC 18(1979)353
ACZF_v1_0 DATSTOR CPC 18(1979)377

Nature of problem:
PLASKEM is a program to predict the variation with time of the number densities of the various chemical species contained within a plasma, with particular interest in the plasma contained in the discharge tube of gas lasers. The chemical reactions within the plasma may include neutral molecule-neutral molecule collisions as well as electron- molecule, electron-ion and molecule-ion collisions. The plasma is assumed initially to contain known fractions of primary species which react to form secondary species.

Solution method:
The time rates of change of the number densities of the chemical species are described by a set of coupled, nonlinear differential equations. One equation is required for each primary and each secondary species. An additional equation is required to account for changes in the effective electron temperature. The equations are solved by three alternative methods, (1) Runge-Kutta method, (2) initially by the Runge- Kutta method and subsequently by a modified Hamming predictor-corrector method, (3) Gear's method.

Restrictions:
The model used is a spatially independent one, reactions involving the container walls are neglected. The model assumes that the ambient gas temperature remains constant.

Running time:
To solve 20 equations over a period of 300 ns on the ICL 1906A requires of the order of 50 s.