Accession Number : AD0838387

Title :   PHOTON TRANSPORT FROM A POINT SOURCE IN THE ATMOSPHERE.

Descriptive Note : Master's thesis,

Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING

Personal Author(s) : Bigelow, Winfield S., Jr

Report Date : JUN 1968

Pagination or Media Count : 205

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)

Descriptors :   (*NUCLEAR EXPLOSIONS, ATMOSPHERES), (*PHOTONS, TRANSPORT PROPERTIES), ATMOSPHERE MODELS, FLOW CHARTING, COMPUTER PROGRAMS, INCOHERENT SCATTERING, PHOTOELECTRIC EFFECT, GAMMA RAYS, X RAYS, SPECIAL FUNCTIONS(MATHEMATICAL), MONTE CARLO METHOD, NUMERICAL ANALYSIS, POLYNOMIALS, SERIES(MATHEMATICS), THESES.

Subject Categories : Nuclear Physics & Elementary Particle Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE