FY2010 - Oak Ridge National Laboratory

Seed Money Fund—
Computational Sciences and Engineering Division
05888
Development of Real-Time Optimization Methods for Neutron
Scattering Experiments—Where to Measure and When to Stop
Y. Jiao, K. An, P. F. Peterson, X.-L. Wang, and S. D. Miller
Project Description
In advanced neutron scattering, there are strong interests in the research community to study in situ
dynamic or kinematic behaviors of materials under varying temperature, magnetism, pressure, and
electric fields. The major challenge is that materials often react to changing conditions in heterogeneous
and unpredictable ways: parts of the material may exhibit interesting behavior, while the rest does not;
characteristics of a material may change dramatically within a very small range of temperatures, but do
not vary much outside that range; as the pressure increases, molecular structural changes of a material
may appear and then disappear; and the list goes on. We developed a new iterative, dynamic sampling
approach that adjusts an experiment’s plan on the fly, based on the actual observations, to dynamically
decide the area of interest (where to measure) and the minimum measurement time required to obtain
sufficient data (when to stop). The novelty of our approach is threefold: (1) processing of streaming event
data in real time, (2) developing robust algorithms that can handle various material samples and
experimental settings, and (3) interfacing and controlling the instrument in real time. While experiment
optimization on neutron instruments faces the same fundamental challenges, specific solutions are highly
dependent on the instrument. For the proof of principle, we choose an engineering diffraction beam line,
VULCAN at the Spallation Neutron Source, as our test bed with a real neutron diffraction experiment.
Mission Relevance
Neutrons are used by scientists to explore a wide spectrum of problems in the fields of physics, biology,
chemistry, materials science, etc. Ideally, scientists want to be able to capture the intriguing moments
when transformation occurs inside the material and to obtain sufficient amounts of data so that
statistically significant conclusions can be drawn. Due to the exploratory nature of scientific experiments,
scientists usually do not possess the precise knowledge of where or when these moments occur, nor do
they know exactly the minimum measurement time required to obtain sufficient data prior to the
experiment. As a result, precious beam time may be wasted and scientific discoveries may be delayed.
One of the long-term goals of the neutron scattering sciences community is to be able to conduct
experiments the way radiologists do magnetic resonance imaging oday: data are visualized and analyzed
as the procedure is progressing, and decision support software, in real time, helps doctors to decide where
they should investigate further. This project aims to take a step toward that goal. The success of this
project can help accelerate scientific discoveries and can potentially save the research community
millions of dollars.
Results and Accomplishments
We have successfully designed, implemented, and deployed software modules that provide real-time
uncertainty analysis and optimization support to scientists. A Restful web service interface seamlessly
connects the optimization components to the existing data acquisition system (DAS). The design of the
software architecture follows three main principles: simple, modular, and extensible. First, we choose the
RESTful web service paradigm instead of a SOAP-based web interface for its simplicity and stateless
nature. This feature significantly reduces the amount of bookkeeping on the server side and allows for
faster processing. Second, our fitting, visualization, and optimization tools are implemented as separate
modules that can be mixed and matched to solve specific problems. Finally, we decoupled data analysis
from data acquisition to allow both systems to expand independently. This work combines experiment
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