PHOTON TRANSPORT FROM A POINT SOURCE IN THE ATMOSPHERE.
Abstract
A moments calculation was performed for a point, isotropic source of photons in a homogeneous atmosphere. This calculation produces photon density as a function of position and energy. The calculation is carried out for steady-state sources, which means that the results are also applicable to time-integrated photon densities produced by pulsed sources. The uncollided and once-scattered contributions are obtained analytically; the multiply-scattered component is obtained from spatial moments of the spherical harmonic moments of the photon distribution by an expansion in biorthogonal polynomials. In this technique, monoenergetic sources are treated directly, while continuous source spectra are treated by superposition of monoenergetic sources of appropriate strengths. Results are presented for a series of calculations for monoenergetic sources in the 20 KeV to 8 MeV range, and for two continuous source spectra. (These calculations did not account for pair production.) The angle-integrated photon densities are well-converged out to at least 15 mean-free-paths. Angle-dependent densities, however, are poorly represented beyond one mean-free-path. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1968
- Accession Number
- AD0838387
Entities
People
- Winfield S. Bigelow Jr.
Organizations
- Air Force Institute of Technology