<r Carleton physics students and professors, work doesn’t stop at the end of spring term. This summer, physicists budding and professional wrestled with physics quandaries across the globe, from Australia to Olin.
Visiting professor Matt Wiebold and student Zachary Lynn ’14 researched the properties and uses of medical plasmas. According to Lynn, plasmas have a wide variety of medical applications.
“They can sterilize surfaces, since bacteria can’t become immune to plasma,” Lynn explained, “and some groups have been working on using them to sterilize root canals as well.” They can also cauterize wounds, since “wet, bleeding tissue has lower thermal resistance than dry skin”.
To investigate the properties of these plasmas, Lynn and Wiebold built a simple plasma generator, or plasma source.
“The source was just a tube with argon pumped through it,” Lynn said. “There were two disc-shaped electrodes with holes in them, and the electric field between them would ionize the gas” by stripping electrons from the argon atoms. The resulting plasma was near room temperature, although the electrons were much hotter than the ionized argon.
While Lynn and Wiebold were toiling in Northfield, Astronomy professor Joel Weisberg and students, Carolyn Raithel ’15 and Ruiqi Geng ’16, were nine time zones away, in Australia. The trip is an annual tradition for Weisberg in which over a generation of Carls has taken part.
“I’ve had a long connection with astronomers there,” Weisberg explained. Going to Australia, he said, allows students to observe “the other half of the universe you can’t see” from the northern hemisphere.
Weisberg’s research focuses on pulsars, neutron stars that ”pulse” radio signals, which are particularly prevalent in the southern hemisphere. , and Australia ’s Parks Radio Telescope, one of the largest radio telescopes in the world, provided an ideal tool to study them.
Weisberg’s students, meanwhile, worked on individual projects. Geng tried to find out what kind of particles pulsars emitted, while Raithel tried to understand why pulsars emitted a radio signal.
Meanwhile, back at Carleton, Professor Melissa Eblen-Zayas and her students Luke Hellwig ’14 and Berit Goodge ’16 were studying colossal magnetoresistant materials.
“In normal materials,” Zayas explained, “if you apply a magnetic field the resistance changes by maybe a few percent.” But when researchers apply a magnetic field to a colossal magnetoresistant material, the resistance changes by thousands of percent. The group’s research focused on new ways of creating one such material, europium oxide.
“Previously, we had been depositing Europium and oxidizing it,” Zayas said, “but now we are depositing both europium and oxygen simultaneously.”
This technique is called co-deposition, and it lets them make more samples that show colossal magnetoresistant behavior. Zayas said that colossal magnetoresistors could be used to make new types of computer memory and circuits that were based on electron spin rather than charge, but noted that the materials only exhibit this behavior at temperatures of 150 Kelvin, or 216 degrees Fahrenheit below zero.
McCoy Becker ’14 Jay Tasson worked together on the physics of Lorentz violations. Lorentz symmetry, as Becker explained, was a property of spacetime that stated the laws of physics were unaffected by changes in direction or velocity.
Thus far, he said, experiments have shown it to be an immutable law of physics. However, theoretical physics allows for the existence of “background vector fields” in empty space, which might break Lorentz symmetry by, for instance, causing particles to move in a specific direction.
“We looked at specific cases in which Lorentz symmetry would be broken,” Becker said, “and worked out situations in which we could detect it.”.
For instance, one background vector field could change the orbit of electrons around an atom. Nevertheless, much remains to be studied, according to Becker. “I think I’ll continue to work on it for the rest of my time at Carleton,” he said.