NIST minisensor has magnetic personality

Researchers at the National Institute of Standards and Technology (NIST; Boulder, CO) have demonstrated a tiny sensor that can detect magnetic field changes as small as 70 femtoteslas.

Researchers at the National Institute of Standards and Technology (NIST; Boulder, CO) have demonstrated a tiny sensor that can detect magnetic field changes as small as 70 femtoteslas. The NIST prototype comprises a single low-power infrared laser and a 3 × 2 × 1 mm container that holds about 100 billion rubidium atoms in gas form. As the laser beam passes through the atomic vapor, NIST scientists measured the transmitted optical power while varying the strength of a magnetic field applied perpendicular to the beam. The amount of laser light absorbed by the atoms varied predictably with the magnetic field, providing a reference scale for measuring the field. The stronger the magnetic field, the more light is absorbed.

According to project leader John Kitching, the minisensor could reduce the equipment size and costs associated with many noninvasive biomedical tests. The NIST group and collaborators have used a modified version of the original sensor to detect magnetic signals from a mouse heart, and they say the new sensor is already powerful enough for fetal heart monitoring. With further work, the sensitivity could be improved to the 10 femtotesla range, sufficient for additional applications such as measuring brain activity. The device also may have applications in homeland security for screening explosives. Contact John Kitching at kitching@boulder.nist.gov.

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