Particle tracking acceleration via signed distance fields in direct-accelerated geometry Monte Carlo

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Particle tracking acceleration via signed distance fields in direct-accelerated geometry Monte Carlo. This work describes the adaptation of a rendering data structure, the signed distance field, as a geometric query tool for accelerating CAD-based transport in the direct-accelerated geometry Monte Carlo toolkit. Demonstrations of its effectiveness are shown for several problems. The beginnings of a predictive model for the data structure's utilization based on various problem parameters is also introduced.
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Nuclear Engineering and Technology
journal homepage: www.elsevier.com/locate/net
Original Article
Particle tracking acceleration via signed distance elds in
direct-accelerated geometry Monte Carlo
Patrick C. Shriwise*, Andrew Davis, Lucas J. Jacobson, Paul P.H. Wilson
CNERG Research Group, University of Wisconsin - Madison, Madison, WI, USA
a r t i c l e
i n f o
a b s t r a c t
Article history:
Computer-aided design (CAD)-based Monte Carlo radiation transport is of value to the nuclear engi-
Received 3 June 2017
Accepted 7 August 2017
Available online 26 August 2017
neering community for its ability to conduct transport on high-delity models of nuclear systems, but it
is more computationally expensive than native geometry representations. This work describes the
adaptation of a rendering data structure, the signed distance eld, as a geometric query tool for accel-
Keywords:
Monte Carlo
Radiation Transport
CAD
DAGMC
erating CAD-based transport in the direct-accelerated geometry Monte Carlo toolkit. Demonstrations of
its effectiveness are shown for several problems. The beginnings of a predictive model for the data
structure's utilization based on various problem parameters is also introduced.
© 2017 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the
1. Introduction
signed distance eld data structureintendedfor rendering dynamic
surfaces is introduced. The remaining content describes this data
The direct-accelerated geometry Monte Carlo (DAGMC) [1]
structure's adaptation for use in accelerated particle tracking for
toolkit provides the capability for robust radiation transport on
CAD-based Monte Carlo simulations. The application of this data
CAD geometries. This allows nuclear analysis to be performed on
structure and associated tracking methods are then demonstrated
the same models that are used in other engineering domains. The
as a new method for particle tracking acceleration in DAGMC.
toolkit also has the capability to convert native Monte Carlo models
Included demonstrations of this method are shown to greatly
to computer-aided design (CAD) for further development, modi-
reduce run times in a few test problems for commonly encountered
cation, and analysis.
conditions during transport. Next, some studies involving the data
DAGMC tracks particles on discretized representations of ana-
structure's
effectiveness
for
various
problem
parameters
are
lytic CAD surfaces as triangle meshes, such that all points on any
investigated and discussed. Finally, conclusions, current limita-
given triangle are within a specied tolerance of the analytic rep-
tions, and future extensions of this work are discussed.
resentation. This mesh representation of the model is then stored in
the mesh oriented database (MOAB) [2] inwhich geometric queries
such as next surface intersection, point containment, and nearest to
2. Background
boundary are performed.
It has been shown that DAGMC can achieve robust transport
2.1. Acceleration techniques in DAGMC
equal to that of the native codes with which it communicates [3],
but that it currently takes much longer [4]. This additional time
occurs despite the acceleration techniques that DAGMC uses to
avoid searching over the large number of triangles ( 106e107).
Those acceleration techniques, implemented within MOAB, will be
briey discussed to motivate this work, which aims to further
accelerate geometry queries within DAGMC.
To begin, this article gives a brief overview of the employed
acceleration techniques in DAGMC for particle tracking. Next, the
Particle tracking in DAGMC relies on the capability to robustly
perform geometric queries on the triangle surface meshes which
represent the problem geometry. The most common form of geo-
metric query in particle tracking is a next surface crossing query.
This is called to determine if a particle within the current cell will
reach its nextevent location orcross a surface of the cell, potentially
entering a new medium with different physical characteristics,
based on the particle's current position and trajectory. Geometry
kernels in native Monte Carlo codes perform analytic calculations
for the nearest intersection along the particle's trajectory from its
* Corresponding author.
current location. In DAGMC, a similar operation is performed, but
E-mail address: shriwise@wisc.edu (P.C. Shriwise).
on the triangle surfaces that compose the current cell (or volume).
1738-5733/© 2017 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/