Treating electron transport in MCNP{sup trademark}

Conference · Tue Dec 31 00:00:00 EST 1996

OSTI ID:460773

Hughes, H G

The transport of electrons and other charged particles is fundamentally different from that of neutrons and photons. A neutron, in aluminum slowing down from 0.5 MeV to 0.0625 MeV will have about 30 collisions; a photon will have fewer than ten. An electron with the same energy loss will undergo 10{sup 5} individual interactions. This great increase in computational complexity makes a single- collision Monte Carlo approach to electron transport unfeasible for many situations of practical interest. Considerable theoretical work has been done to develop a variety of analytic and semi-analytic multiple-scattering theories for the transport of charged particles. The theories used in the algorithms in MCNP are the Goudsmit-Saunderson theory for angular deflections, the Landau an theory of energy-loss fluctuations, and the Blunck-Leisegang enhancements of the Landau theory. In order to follow an electron through a significant energy loss, it is necessary to break the electron`s path into many steps. These steps are chosen to be long enough to encompass many collisions (so that multiple-scattering theories are valid) but short enough that the mean energy loss in any one step is small (for the approximations in the multiple-scattering theories). The energy loss and angular deflection of the electron during each step can then be sampled from probability distributions based on the appropriate multiple- scattering theories. This subsumption of the effects of many individual collisions into single steps that are sampled probabilistically constitutes the ``condensed history`` Monte Carlo method. This method is exemplified in the ETRAN series of electron/photon transport codes. The ETRAN codes are also the basis for the Integrated TIGER Series, a system of general-purpose, application-oriented electron/photon transport codes. The electron physics in MCNP is similar to that of the Integrated TIGER Series.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 460773
• Report Number(s): LA-UR-96-4583; CONF-9605255-1; ON: DE97003094; TRN: 97:007238
• Resource Relation: Conference: Training course on use of MCNP in radiation protection dosimetry, Bologna (Italy), May 1996; Other Information: PBD: [1996]
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
99 MATHEMATICS
COMPUTERS
INFORMATION SCIENCE
MANAGEMENT
LAW
MISCELLANEOUS
MONTE CARLO METHOD
CHARGED-PARTICLE TRANSPORT
M CODES
ELECTRONS
PROBABILITY
CHARGED-PARTICLE TRANSPORT THEORY
ENERGY LOSSES
STOPPING POWER
TAIL ELECTRONS
LANDAU FLUCTUATIONS
MULTIPLE SCATTERING
MULTIPLE COLLISION METHOD