Small invention, massive leap

November 22, 1996

NASA has awarded a contract to physicists at the University of Wales Aberystwyth to equip its deep space probes with the world's smallest yet most efficient mass spectrometer detector array.

The array will be used in the Mars follow-on and Discovery Programme missions to analyse both the upper altitudes of the Martian atmosphere, as well as lower altitudes, just before the probe hits the surface.

Nasa already has a miniature mass spectrometer, but with the addition of the Aberystwyth detector array it is now much lighter and almost 200 times more efficient. The original Nasa array needed external electronics whereas the new version is completely self-contained on a single silicon chip, weighing a mere 0.5 grams.

The array was developed under a Link programme, a government scheme to support research links between industry and the science base, with research council and Department of Trade and Industry funding. Two British companies, VG Analytical and ICI, collaborated on the project as well as the Rutherford-Appleton Laboratory and Hughes Microelectronic Europa. The total cost was about Pounds 1.25 million.

Mass spectrometers are often used to measure the concentration of pollutants in the air or to detect drugs in blood. They do this by evaluating ions - atoms or molecules with one electron missing which means they are positively charged and so can be manipulated using electronic and magnetic fields. But current instruments are not very efficient. They only have a single ion detector so that most of the sample spectrum is lost.

To combat this the Aberystwyth team have used the latest microtechnology to develop a whole array of detectors, three banks of 64, all placed on a single silicon chip. With all the 192 detectors operating, the spectrometer can detect a whole section of spectrum instead of a tiny segment.

Keith Birkenshaw, research leader, says: "Recently I was working on a project in the United States and using a conventional mass spectrometer. It took me nine months to come up with the final results. With our new array it could have been completed in a day."

Eventually Dr Birkenshaw would like to use 2,000 detectors on just 5cms of chip. The Aberystwyth team is hoping to join forces with Nasa's Advanced Concept Programme at the Jet Propulsion Laboratory at Pasadena, in California, to design larger arrays. These improvements should eventually allow "real time" analyses of rapidly varying samples - such as an explosion.

"I am convinced that detector technology in the future is going to be based on the integration of the electronics that we have pioneered," said Dr Birkenshaw. "An array of detectors requires a large amount of associated electronics, so we are offered no alternative but to miniaturise - and we have succeeded."

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