ICAP 2002 Abstracts and Posters

Tracking Particles in Axisymmetric MICHELLE Models*

Abstract

A novel particle tracker for 3D unstructured grids has been developed and employed in the finite element gun code MICHELLE. The particle tracker has now been extended to handle 2D planar and axisymmetric models. The unstructured 2d grids may contain triangle and/or quadrilateral elements and the element shapes may be linear, quadratic or cubic. In this paper we describe the particle tracking algorithm for axisymmetric models.

The 2D algorithm is similar to the 3D algorithm. A particle's position is integrated in the enclosing element's local coordinate system, and the particle's momentum is integrated in the global coordinate basis. For axisymmetric models we also integrate the azimuthal angle, and we continue to use the cartesian basis for the momentum. We do not integrate the momentum in the cylindrical coordinate basis. This provides for acceptable behavior near the axis without any exceptional treatment, but there is the additional cost of a coordinate transformation in the equations of motion.

* Work supported by DOE, contract W-7405-ENG-36, and ONR, NRL contracts N00014-02-C-2076 and N00173-02-MP-00044.

Eric M. Nelson and John J. Petillo**
Los Alamos National Laboratory, MS B259, Los Alamos, NM 87545
**SAIC, Suite 130, 20 Burlington Mall Road, Burlington, MA 01803

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