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Manuscript Title: Computer simulation of photons in spheric media for density gauges.
Authors: E.R. Christensen
Program title: MCD
Catalogue identifier: AAUL_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 7(1974)192
Programming language: Fortran.
Computer: IBM 370/165.
Operating system: HASP II.
RAM: 23K words
Word size: 32
Keywords: Nuclear physics, Photon scattering, Monte carlo method, Spheric medium, Principle of similitude, Least-squares fit.
Classification: 17.1.

Subprograms used:
Cat Id Title Reference
AAUK_v1_0 MCS CPC 7(1974)185

Nature of problem:
Multiple photon scattering in a spheric medium is considered. The photons are assumed to originate from a mono-energetic point source situated at the center. The relative photon track length, weighted with a detector efficiency spectrum, is calculated in consecutive radial intervals. In order to contribute to the track length, the elements of the photon paths must form an angle with radius vector which is greater than a specified cut-off angle.

Solution method:
Photons are simulated by the Monte Carlo method. The scattering angle is determined by iteration from the Klein-Nishina cross section. A least squares fit of an analytical expression to the calculated results is performed.

Restrictions:
A maximum of 12 elements, 19 energy groups, 50 radial-, and 11 importance intervals may be considered. The medium is spheric and homogeneous.

Unusual features:
Responses in different radial intervals can by the principle of similitude be interpreted as responses in a given interval at different densities. This presupposes an infinite medium and similar radial intervals.

Running time:
Simulation of 24 000 histories takes about 3 min of central processor time.