Campus researchers use magnetic microscope to advance thermionics research

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Researchers at Lawrence Berkeley National Laboratory have advanced research in thermionics, with the aid of a magnetic microscope unique to Berkeley Lab, to more efficiently convert solar energy.

Jared Schwede and Daniel Riley pursued their thermionics research at Cyclotron Road, an institute at Berkeley Lab that sponsors entrepreneurial scientists whose research focuses on clean energy and could have commercial value.

Thermionics is a field of science that involves the conversion of heat into energy. The creation of solar energy typically involves converting either light or heat from the sun into usable energy, according to Nicholas Melosh, an associate professor of material science and engineering at Stanford University. Melosh served as a research adviser for both Schwede and Riley when they were doctoral students at Stanford.

“They were discovering scientific results that really looked like, based on these discoveries, it should be possible to create a much more efficient heat-to-electricity conversion system,” said Andreas Schmid, a staff scientist at the Molecular Foundry, an institute within Berkeley Lab.

Schwede and Riley began developing a process that would combine the conversion of both heat and light energy in a manner similar to the function of a vacuum tube — a device that controls electric currents in a space devoid of matter — allowing for greater efficiency, Melosh said.

Before finishing at Stanford a year and a half ago, Schwede and Riley were studying thermionics for about five years, according to Melosh. They both belonged to his research group, which studied photon-enhanced thermionic emissions, or PETE, Melosh said.

“There’s a real opportunity in the business world for a simple version (of their research),” Melosh said about their thermionics work at Stanford. Cyclotron Road, where Schwede and Riley brought their research, was founded to connect the ideas of scientific discovery and creating a commercial project.

In 2010, Schwede and Riley contributed to an academic paper that concluded that “PETE’s straightforward design could lead to inexpensive manufacturing” using microelectromechanical systems technology, according to the paper.

Schmid began working with the two researchers when they discovered they could use the lab’s low-energy electron beam microscope — which was designed to take pictures of magnetism — to measure the work function, or the energy required, to remove atoms.

“This was sort of fortuitous because (the low-energy electron beam) inherently as a side effect becomes a very sensitive instrument to map out images of this work function property,” Schmid said.

Being able to determine work function using the microscope would allow Schwede and Riley to optimize their device and create a powerful electrical generator, according to Schmid.

Schmid, who has worked at the Molecular Foundry for more than 15 years, said many international and American researchers use this microscope for their research, as the device is unique. Though the microscope is mostly used to view magnetism, it has previously been used to detect other properties, according to Schmid.

Contact Patricia Serpa at [email protected] and follow her on Twitter at @pserpa_dc.