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Manuscript Title: COLASE: a CO-N2-He laser kinetics code.
Authors: S.A. Roberts
Program title: COLASE
Catalogue identifier: ABVF_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 20(1980)373
Programming language: Fortran.
Computer: AMDAHL V/7.
Operating system: VM/CMS.
RAM: 130K words
Word size: 48
Keywords: Laser physics, Co-n2-he, E-beam, Kinetics.
Classification: 15.

Nature of problem:
From a knowledge of the rates of the various kinetic processes which occur in e-beam CO-N2-He gas lasers, the code COLASE predicts the time history or alternatively, the steady state values of the population inversion and hence the gain coefficients and output intensities for all lasing lines which are predicted to be above the lasing threshold.

Solution method:
A set of coupled, first-order, non-linear ordinary differential equations are developed which describe the time rate of change of the population number densities of the vibrational levels of CO and N2, the light intensities for each lasting line and the ambient temperature of the gas. These equations are solved numerically using either Gear's method, or initially by the Runge-Kutta method and subsequently by a modified Hamming predictor-corrector method. Alternatively, to simulate cw (steady-state) operation, an iterative method is used to solve the coupled, non-linear algebraic equations describing the cw population number densities and the light intensities.

The model assumes spatial homogeneity, that is effects of conduction and diffusion to the cavity walls are neglected.

Running time:
In cw mode of operation, typically 10 s on the CDC 7600. In pulsed mode the run time is highly dependent on input parameters. Results for test case 1 took 70 s on the CDC 7600.