Synthetic acceleration methods for linear transport problems with highly anisotropic scattering

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5909106

Khattab, K M

One of the iterative methods which is used to solve the discretized transport equation is called the Source Iteration Method (SI). The SI method converges very slowly for problems with optically thick regions and scattering ratios ({sigma}{sub s}/{sigma}{sub t}) near unity. The Diffusion-Synthetic Acceleration method (DSA) is one of the methods which has been devised to improve the convergence rate of the SI method. The DSA method is a good tool to accelerate the SI method, if the particle which is being dealt with is a neutron. This is because the scattering process for neutrons is not severely anisotropic. However, if the particle is a charged particle (electron), DSA becomes ineffective as an acceleration device because here the scattering process is severely anisotropic. To improve the DSA algorithm for electron transport, the author approaches the problem in two different ways in this thesis. He develops the first approach by accelerating more angular moments ({phi}{sub 0}, {phi}{sub 1}, {phi}{sub 2}, {phi}{sub 3},...) than is done in DSA; he calls this approach the Modified P{sub N} Synthetic Acceleration (MPSA) method. In the second approach he modifies the definition of the transport sweep, using the physics of the scattering; he calls this approach the Modified Diffusion Synthetic Acceleration (MDSA) method. In general, he has developed, analyzed, and implemented the MPSA and MDSA methods in this thesis and has shown that for a high order quadrature set and mesh widths about 1.0 cm, they are each about 34 times faster (clock time) than the DSA method. Also, he has found that the MDSA spectral radius decreases as the mesh size increases. This makes the MDSA method a better choice for large spatial meshes.

• Research Organization: Michigan Univ., Ann Arbor, MI (USA)
• OSTI ID: 5909106
• Country of Publication: United States
• Language: English

Related Subjects

654001* -- Radiation & Shielding Physics-- Radiation Physics
Shielding Calculations & Experiments
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ANGULAR MOMENTUM
CHARGED-PARTICLE TRANSPORT
CHARGED-PARTICLE TRANSPORT THEORY
CONVERGENCE
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
ITERATIVE METHODS
LEPTONS
MESH GENERATION
PERFORMANCE
RADIATION TRANSPORT
SCATTERING
TRANSPORT THEORY