Illinois Institute of Technology - Unlimiited Potential

Grad Student Research

A newsletter spotlighting the research of IIT Graduate Students

June 2009

Graduate student researchers at IIT make an important contribution to the scientific world. To bring attention to some of the outstanding graduate students within all IIT departments, the Graduate College is publishing a monthly newsletter spotlighting individual students and their research.

Ben Freemire, a Ph.D. Candidate in particle and accelerator physics is working from Fermi National Accelerator Laboratory on projects related to the Muon Ionization Cooling Experiment (MICE), located at Rutherford Appleton Laboratory (RAL) near Didcot, Oxfordshire in the United Kingdom. MICE is a precision accelerator physics experiment aimed at producing a beam of muons and reducing its transverse (perpendicular to the direction of travel) emittance by 10% to within 0.1% accuracy. To create muons, the proton beam from ISIS (RAL’s particle accelerator) collides with a target, producing pions, which in turn decay to muons (a muon is essentially an unstable electron with a larger mass). They select the muons with momenta between 140 and 240 MeV/c to be “cooled”.

Once the muons are obtained, they are passed through a series of detectors to measure their position and momentum. From this their initial emittance can be found. Emittance is basically a measure of the position and momentum distribution of a beam of particles. Small emittances are ideal, in that this provides larger beam luminosity, which equates to more collisions between particles. A series of liquid hydrogen absorbers and high grade electric fields decrease the muons’ overall energy and then reaccelerate them in the direction of the beamline. Finally they pass through another set of detectors to measure their final emittance.

Freemire has worked on two specific projects for MICE. He has been in charge of writing software to map two magnets that will be used in the experiment. This involves turning the solenoidal magnets on and sending a cart with probes on it through them to collect magnetic field measurement data. A map can then be created from the specified positions to give an accurate measurement of the magnetic field within the magnet and to ensure the field meets specifications. It is important to know this so that particles traveling through these magnets can be precisely tracked.

He has also worked on the tracker detectors that they use. The tracker detectors involve electronic circuitry that measure photons produced in scintillating fibers. This can tell a number of things about the particles that hit them. However, each tracker must be optimized in order to gather the most accurate information. This involves creating a mock setup and producing test signals that are read by the circuit boards on the tracker. These boards must be run at various voltages, and once the sample data is analyzed, the optimum values are selected. Once this is done, the components of that tracker are packed and shipped over to RAL to be installed.

More information about MICE may be found at http://mice.iit.edu/.

Transcranial magnetic stimulation (TMS) is an important technique with applications to both clinical therapeutics and neuroscience research. It induces electric current in the brain through a dynamic magnetic field that is generated by a coil positioned above the scalp. Because TMS is noninvasive, relatively painless, and capable of both inhibiting and exciting neuronal pathways, it has been widely applied in the treatment of neurological disorders such as schizophrenia, depression, Parkinson’s Disease, chronic pain reduction, and stroke. However, with all its potential, TMS is still not a very refined technique. The electromagnetic field distribution and excitation region in the brain during TMS has not been accurately mapped, and the interaction between these fields and neurons in the brain is not well understood. In addition, the stimulation coils currently available in the market do not adequately satisfy the requirements of deep brain penetration and tightly focused neuronal activation. Although researchers have attempted to solve these problems by providing distribution maps for the induced electric fields in the brain though computer modeling, most of these models lack key geometric details of the brain at both the macroscopic and microscopic scales. These elements can significantly affect the accuracy of calculated electric fields, which play a critical role in brain activation.

Ming Chen, a doctoral student in biomedical engineering, under the guidance of Dr. David Mogul, is working to address these issues through simulations using a complex 3D computer head model based on MR and CT images from real patients. Anatomical features on the neocortical surface as well as microstructural details under it are incorporated in the model. With this tool, Chen, along with other researchers, is investigating the influence of a TMS coil position, distance and orientation on the induced electric field and neocortical activation. Several factors including magnitude, orientation, polarity, and threshold of induced current density in the columnar structures are being tested for their impact on the distribution of neocortical activation. This information provides a resource for understanding the electrophysiological consequences of neuronal activation by TMS. In addition, new coil configurations will be created and tested in a computerized environment with this detailed head model to improve the ability to selectively innervate regions throughout the brain.

Polymer rheology plays a significant role in our lives. Every day we use products that are made of plastic, from the bags that carry your groceries, to the advanced materials that help your car get better gas mileage. However, despite our achievements in technology, the best method of designing plastic processing equipment is through intuition and trial and error. There have been many attempts to create a mathematical model that can predict polymer flow accurately. Although some models can successfully determine the results of specific experiments for distinct polymers, the application of these models is very narrow.

One of the biggest challenges is adapting these models for different polymer structures. There are models for linear polymer melts, polydisperse blends and completely different models for starshaped polymers. Nevertheless, most of these models cannot be applied to flow. The research of Renat Khaliullin of ChBE is part of an ambitious goal to develop a single unified mathematical model to predict polymer melt behavior for most flow experiments, independent of polymer structure. This model is called the sliplink model.

In order to extract useful information from the model, for instance the relaxation of stress following deformation, computer simulations must be run to solve the mathematics numerically. Khaliullin’s research includes developing a Fortran program to execute this simulation. After each simulation, the results are confirmed with prior experiments and they will be analyzed to create an analytic representation of the model. Analytical models are easier and faster to utilize and are more adaptable to variations in experimental parameters. Additionally, it is shown that the model is not restricted to plastic polymer melts, but can describe other dense polymer systems as well. One of Khaliullin’s applications is in modeling DNA electrophoresis in a polymer solution or gel. He is currently comparing model predictions with experimental data. In the future, he will be performing experiments on linear and star DNA diffusion and will be comparing these results with the sliplink model prediction.

Within the Thermal Science and Combustion Lab, under the guidance of Dr. Francisco Ruiz, Adrian Bueno, a Ph.D. student in Materials Science, is researching the mechanism of pulsed combustion caused by acoustic forcing. Pulsed combustion has been proven more efficient and less pollutant than continuous combustion, but it can be achieved only under certain circumstances, generally in the presence of some sort of flow rectifier, such as resonant tubes. Ruiz and his fellow researcher have succeeded in producing pulsed combustion by means of acoustic forcing instead of using a flow rectifier. The experiment built to investigate this phenomenon consists of a square duct with a burner and speaker attached to its respective ends fed with a mix of natural gas and air. The burner is a matrix of a porous metallic alloy and the speaker is a mid-range subwoofer where high-amplitude acoustic forcing is applied at several frequencies and voltage amplitudes.

It is believed that combustion gases go back to the matrix by means of backward flow, re-heating the burner. This inverse flow would be due to the fact that high pressure oscillations generate strong vortices in the periphery of the burner. In order to learn further, representative parameters are measured: pressure fluctuation inside and outside the duct, and surface temperature. Besides these measures, photographs are taken from two different angles, directly above the burner and in front of it. With these measurements and photographs, vortices and their impact can be studied. Zenith pictures show the dimension of the radiant area (where the combustion actually takes place) and front pictures reveal combustion gases flow. For a narrow range of frequencies, between 25 and 65 Hz, and voltages above 12V the temperature increases more than 100 degrees over the base condition, a leap from 1173K to 1300K, leading to a radiant flux increase as much as 75%. However, whereas the temperature rises, the radiant area decreases up to 50% due to the vortices that squeeze the radiant surface. On the other hand, for said frequency range low amplitudes drive not only to smaller hot surface but also lower temperatures than the base. All the same, the overall radiant heat output reaches a peak at 35Hz and 20Hz accompanied by a 5% increase.

Nevertheless, despite these promising facts very little is known and further research must be carried out to fully understand this extraordinary behavior and features such as the transition between combustion modes.