College of Engineering University of Wisconsin-Madison
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EPISODE: The Engineering Physics Department Newsletter

 

Spring/Summer 2003
Featured articles

Taming turbulence: Understanding the equations

Exploiting friction can make MEMS work

New boundaries: Experiments verify ion behavior in plasmas

Engineers develop new prostate-cancer treatment plan

Conference to address state energy crisis


Regular Features

Message from the chair

Department news

New faculty: Joseph Bisognano and Dennis Whyte

Student news

 

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NEW FACULTY

Portrait of Joseph Bisognano

Joseph Bisognano
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Joseph Bisognano

Decorative initial cap The University of Wisconsin-Madison has a long history as a center for accelerators. In 1952, a research group called MURA, or the Midwestern Universities Research Association, formed to design the next large U.S. accelerator facility. UW-Madison was key to that plan and a decade or so later the university became home to the 240 megavolt electron storage ring Tantalus, the first storage ring used exclusively for synchrotron radiation research.

Photo of the Aladdin Storage Ring at the Synchrotron Radiation Center
The Aladdin Storage Ring at the Synchrotron Radiation Center
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Tantalus also marked the inception of the university’s Synchrotron Radiation Center (SRC), located near Stoughton. Later, a larger synchrotron radiation source called Aladdin took its place, enabling researchers to use X-rays and ultraviolet light to image and study everything from the biology of cells and the composition of interstellar clouds to the superconducting properties of materials.

SRC Director Joseph Bisognano, who joined the department as a professor in fall 2002, studies the dynamics of the electron beam that creates the light source to make this research possible.

His primary area of interest is collective-beam dynamics in particle accelerators. “As you start putting more and more particles into the accelerator, they start talking to each other, because they’ve got charge and they push on each other,” he explains. “Coherent, wavelike motion can result. The resulting beam motion can become unstable, or nonlinear, and sets a limit on how much beam current an accelerator can tolerate. Since more current means more photons, increasing the threshold currents for this destructive behavior is critical to heightened performance.”

Because particle beams are high-current objects affected by long-range electromagnetic forces, he likens his research to plasma physics and says it is a good fit for the Department of Engineering Physics. “Accelerators embody a broad range of technology, including electrical engineering, control theory, cryogenics, vacuum systems, plasma physics, magnetic materials, and so on,” he says. “So if you look at the list of disciplines that go into accelerator science, it’s not just classical physics. It really involves very fundamental, innovative engineering.”

Bisognano, who earned his PhD in physics from the University of California-Berkeley in 1975, plans to start a graduate accelerator program here and will teach his first course in accelerators in spring 2004. He has served in both faculty and scientific positions at such institutions as the College of William & Mary, Lawrence Berkeley Lab, and the Thomas Jefferson National Accelerator Facility, with its 6 GeV superconducting linear accelerator, in Newport News, Virginia.

At Lawrence Berkeley Laboratory, he analyzed the current limitations of its advanced light source. He also researched the collective effects of superconducting proton colliders and inertial-confinement fusion drivers. “All of those have high-current particle beams, so a variety of collective effects become the limiting phenomena,” says Bisognano, who developed the theory of how an electronic feedback system reduces a particle beam’s temperature.

Currently he and others at SRC are working on ways to upgrade the photon beam properties for users by increasing the electron beam’s density. “We are now able to offer a photon beam with a factor of two-higher flux density,” says Bisognano. “Much other work is going on to enhance beam stability and increase beam lifetime.”

And in his free time, Bisognano is devoting much work to another ambitious endeavor: A house on Lake Mendota he and his wife just bought. “It’s a real fixer-upper,” he says, “with plenty of opportunities for upgrading performance!”

 

Photo of Dennis Whyte

A crane hoisted part of Dennis Whyte's ion-beam accelerator into his third-floor laboratory.
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Dennis Whyte

Decorative initial cap Tn a misty gray day back in November, even a casual observer could tell that Dennis Whyte nearly buzzed with enthusiasm. It was the day a crane hoisted a gigantic cylindrical Pelletron ion-beam accelerator through a third-story window and into his Engineering Research Building laboratory.

As the accelerator soared through the air, Whyte already talked about its collaborative research potential. “It’s a generic tool for doing surface analysis and modification,” explains the assistant professor, who joined the department in fall 2002.

Photo of the installation of the accelerator
Installing the accelerator: a perfect fit
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He hopes to use it to study, in real time, how plasmas and surfaces affect each other, but says other fusion research facilities on campus and around the world could use it to study material samples. In addition, its applications include nanofabrication and plasma-surface implantation. “It has so many applications that it’s mindboggling, really,” says Whyte. “Anything that works with surfaces and materials can really use this as a tool. What’s exciting for the college is that kind of cross-collaboration and the possibilities for that kind of work to be going on outside of the fusion research.”

A native of Shaunavon, Saskatchewan, Canada, Whyte received his bachelor’s degree in engineering physics in 1986 from the University of Saskatchewan in Saskatoon. Studying at Canada’s national fusion research facility, the Tokamak de Varennes in Montreal, he earned a PhD in applied physics from the University of Québec in 1992.

There he developed a system that used high-powered lasers to create atomic beams that researchers could inject into a tokamak plasma. The beams help them nonintrusively track how particles (micro-sized bits of “dirt” the plasma sloughs off the containment vessel’s inner wall) are transported within the reactor. This dirt “poisons” the plasma and eventually destroys potential fusion reactions.

Similarly, as a postdoctoral fellow and later a research scientist at the University of California-San Diego, Whyte spent the bulk of his time at the DIII-D National Fusion Facility developing atomic-physics and measurement techniques to explain what occurs in the plasma.

He also studied what to do if the tokamak, or “magnetic bottle,” develops a leak. When that occurs, the plasma escapes within a thousandth of a second and pours massive amounts of heat and energy into what it contacts on the way. “The idea is not to stop the disruption, but we trigger what is essentially a safe shutdown of the plasma to minimize damage to the components inside the reactor,” he says.

His solution was to develop a system to inject a large gas “slug,” or jet, into the plasma. “We try to take all the energy in the plasma and convert it into light, and dissipate the energy by light,” he explains. “Light is the best way because it doesn’t damage materials as much and it more or less goes everywhere, so it kind of spreads the pain.” The technique proved successful and Whyte recently reported the results internationally.

In his research, both plasmas and the materials they interact with carry equal weight. He joined the DiMES (Diverter Material Evaluation Studies) project on the DIII-D tokamak in 1995 and became its experimental coordinator. The project focused mainly on testing materials for the containment vessel’s inner wall in a realistic fusion environment. “Typically this is a very thin layer of a few millimeters or more which basically is the contact between the plasma and the rest of the world,” he says.

In theory, the layer should be benign to the plasma, he says. In addition, it should extract heat from the reactor efficiently. Given that the tokamak fuels deuterium and tritium are forms of hydrogen, which is extremely chemically reactive, there are few compatible materials that are mechanically feasible and also can handle heat.

Among his group’s DiMES discoveries were a plasma cooling method that stopped the quick erosion of the reactor’s diverter plates, which remove power, heat and ash from the system. In addition, the researchers conducted the first careful physics studies of why tritium was becoming trapped in the containment vessel’s inner wall.

It’s an ongoing question, and one that Whyte hopes to answer at UW-Madison. In addition, he eagerly anticipated working with students. “I’m very motivated to attract and help train the next generation of people who will work on this … because the problems are not going to be solved anytime soon,” he says.

With his wife, Sandy, and daughters Camille, 5, and Malindi, 2, he recently purchased a house here. And after two hours daily on the road in San Diego, Whyte also is thankful for his new “commute”: an eight-minute walk to work.

 


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Date last modified: Monday, 16-July-2003 15:43:00 CDT
Date created: 14-July-2003

 

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