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Researchers improve mass spectrometer performance

Scientists' findings could have widespread applications

<p>Research scientist Jason Amsden noted that NASA often seeks more advanced spectrometers.</p>

Research scientist Jason Amsden noted that NASA often seeks more advanced spectrometers.

Duke scientists are developing technology that could be used to better detect methane leaks and hidden explosives, among other substances.

A research team led by Jeffrey Glass, professor of electrical and computer engineering, is using software to improve the performance of mass spectrometers. These instruments can identify almost any compound by electrically charging its molecules and detecting the degree they bend in an electric or magnetic field. Glass' team is working to increase mass spectrometers' resolution and decrease their size and cost.

The scientists have developed the technology to build a coded aperture spectrometer, which can be smaller and more portable without compromising its performance, Glass explained. The spectrometer has potential applications in many areas, including in detecting explosives and possibly in space travel.

“NASA’s missions always have mass spectrometers on them, and they’re always looking to make things smaller, but they still want the level of performance of a larger instrument,” said Jason Amsden, manager of the project and a research scientist in Glass' Nanomaterials and Thin Films lab.

Glass said that the team is now funded by the Department of Energy's Advanced Research Projects Agency-Energy to develop a spectrometer capable of detecting methane leaks, which pose environmental risks.

Although mass spectrometry has been used since the 1930s, the spectrometers are usually confined to the lab because of their large size. Amsden noted that there is usually a trade-off between size and resolution, so it is difficult to scale the instrument down.

Glass compared this challenge in developing spectrometer images to how a camera functions.

“If there’s an eclipse, what you do is put a pinhole in a piece of cardboard and project the image of the eclipse onto the ground," Glass said. “If the pinhole is small, you’d get a very sharp image of the eclipse but the image would also be dim and you’d barely be able to see it. Make the pinhole too large, and the image would not have any resolution.”

He explained that the way to fix that problem is to put a thousand pinholes in a piece of paper, getting a series of low intensity images. Each of these images produces a slightly different shot of the original object but these can then be layered on top of each other.

“The coded apertures allows the number of ions or the number of molecules we’re detecting to be increased dramatically without hurting resolution, meaning that we’ll get much more signal and we’ll still be able to identify more molecules from one another," Glass said. "It breaks the traditional trade-off between resolution and signal intensity.”

The coding uses the sizes and positions of the apertures to help combine these images and account for the slight lateral shifts when layering multiple pictures into a single image.

Glass explained that the higher resolution of the coded aperture spectrometers could be useful for analyzing smaller amounts of compounds, such as infant blood samples. He said that he hopes eventually this type of mass spectrometer will be placed in every doctor’s office, which will allow patients to get quicker blood sample results.

Amsden added that the coded aperture spectrometers developed by the team will also likely be less expensive than the current high resolution spectrometers.