Contact
Laboratory
University of Chicago
Center for Integrative Science, W 309
929 E. 57th St
Chicago, IL 60637
ph: (773)834-9160
Research
Interests
The physics of "human" scale systems
far from equilibrium is vital to our every day lives,
but is not thoroughly understood. Much of physics is
historically focused on systems in equilibrium where the
math has clean analytic solutions, but these situations
represent only a subset of the interesting useful
phenomena we encounter in the world around us.
There are still many human scale physics problems that
until now have been inaccessible to science due to
their small size or high speed. More of these problems
are becoming accessible as instrumentation takes full
advantage of technological advances. The improvement
in instrumentation has brought with it the problem
of dealing with massive data sets, true staggering amounts
of information can be generated very easily. To understand
the physics it is necessary to develop new and novel
methods of data analysis and handling.
Glassy Colloidal Systems
The nature of glassy and amorphous
solid's present one of the last unsolved problems in
condensed matter physics. As a material is quenched from
the liquid to glass state the atomic structure does not
change. Despite no structural change, the macroscopic
properties change drastically. The viscosity diverges and
the material will support a shear stress. This is
contrasted to crystallization where both the changes in
macroscopic properties are accompanied by major
microscopic changes. Understanding the liquid-glass phase
transition will significantly expand our understanding of
condensed matter systems. I study glass systems by using
a model system made from thermosensitive colloids observed
using a high speed confocal microscope.
Confocal microscopes can generate an
amazing amount of raw data quickly, however interpretation
of the images requires that individual particles be
identified and tracked. While this is fairly easy to do
by eye for a few particles, but quickly becomes
intractable for large numbers of particles. The
algorithms for finding and tracking particles were
developed by Crocker and Greir and have been widely used
by the community.
There are a number of implementations of
the algorithm in IDL and MATLAB, however the execution
time of these implementations becomes unreasonably long
for extremely large data sets. Building on the work of
Peter Lu, who reimplemented the particle location
algorithm in c++ (
sourceforge project), I have been working on
reimplementing the single particle tracking algorithm in
c++. Currently the code has minimal functionality, but a
framework exists to move almost all analysis from MATLAB
or IDL in to c++ which will result in significant speed
improvements. Simplistic testing suggests the c++ code is
approximately 8-10 times faster than Dan Blair's MATLAB
code for identical data and parameters. Much of the
execution time is building and then destroying the
internal data structure, as more analysis is done in the
frame work the importance of this overhead will decrease.
Documentation is available at http://jfi.uchicago.edu/~tcaswell/track_doc
and the code is available via subversion from
svn://innoue.uchicago.edu/tracking/trunk.
If you are interested in using this code please feel free
to contact me.
Past Research
At Cornell I worked for Professor Sol
Gruner with the detector development group on Pixel
Array Detectors (PADs), a class of high-speed direct
detection x-ray detectors. I primarily worked on the
control systems and experimental applications of PADs,
participating in several experiments conducted at the
Cornell High Energy Synchrotron Source (CHESS) and
adapting a PAD for use in an electron microscope.
In the summer of 2005, I helped prepare
for and execute a two week experimental run at CHESS.
In collaboration with Jin Wang's group from Argonne
National Lab and Visteon Corporation we conducted two
radiography experiments. The first experiment was time
resolved tomography of the spray cone of a low pressure
injection nozzle for gasoline engines. In the second
experiment, we studied shock waves from fuel injection
in a simulated diesel engine.
For my undergraduate senior thesis I
finished adapting a 16x16 PAD for use in scanning
transmission electron microscopy (STEM) in collaboration
with Peter Ercius from Professor David Muller's group.
In STEM, a small electron probe is rastered across the
surface of a sample and a full diffraction pattern is
formed at each raster position. Commercial STEM systems
use point detectors to image the transmitted electrons
reducing the information to one or two channels. Point
detectors sum intensity across their active area, losing
almost all of the spatial information. However,
commercially available available area detectors are not
practical for use in STEM due to low frame rates. The
PAD used for this work is capable of framing at 1.1kHz,
making it's use in STEM practical. A practical area
detector for STEM could revolutionize the field of
electron microscopy by allowing access to orders of
magnitude more information from each sample with
comparable collection times to current point detectors.
Publications
- Thomas A Caswell, Peter Ercius, Mark W Tate, Alper Ercan, Sol M Gruner, David A Muller. A High Speed Area Detector for Novel Imaging Techniques in a Scanning Transmission Electron Microscope Ultramicroscopy (2008)( .pdf 802kb)
- Thomas A Caswell. Study and Testing of a Pixel Array Detector for Electron Microscope Applications Cornell University Senior Thesis, 2007 (.pdf 3.4Mb )
- Xin Liu, Kyoung-Su Im, Yujie Wang, Jin Wang, David L.S. Hung, James R. Winkelman, Mark W. Tate, Alper Ercan, Lucas J. Koerner, Thomas Caswell, Darol Chamberlain, Daniel R. Schuette, Hugh Philipp, Detlef M. Smilgies, Sol M. Gruner. Quantitative Characterization of Near-Field Fuel Sprays by Multi-Orifice Direct Injection Using Ultrafast X-Tomography Technique. Society of Automotive Engineers (SAE) Technical Paper 2006-01-1041. (.pdf 1.50 kb)

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