HomePhysicsTwo Paths to a Magnetic Gradiometer

Two Paths to a Magnetic Gradiometer

• Physics 15, s162

Atomic magnetometers using two new geometries can exclude background fields to choose up weak, close by radio-frequency sources.

From the slivers of pure magnetite used because the earliest magnetic compasses to right this moment’s cryogenically cooled superconducting quantum interference gadgets, researchers have employed many various means to measure magnetic fields. Now Robert Cooper at George Mason College, Virginia, and colleagues have added two extra [1]. Their devices, that are variations on a high-precision instrument known as an optically pumped atomic magnetometer, are the primary demonstrations of “intrinsic radio-frequency gradiometers.” These gadgets are particularly suited to measure weak, native radio-frequency sources whereas excluding background fields.

On the coronary heart of an optically pumped atomic magnetometer lies a gasoline of alkali atoms whose spins are aligned by a circularly polarized laser—the optical pump. The presence of an exterior magnetic discipline perturbs the spin axis of those atoms, displaying up as a change within the polarization route of the probe beam—a second, linearly polarized laser that can be transmitted by means of the gasoline.

Within the gadgets devised by Cooper and his colleagues, the probe beam makes a number of passes by means of the alkali gasoline, maximizing the machine’s sensitivity to weak fields. In a single setup, a high-power probe beam takes a single M-shaped route by means of the gasoline, passing twice by means of a pair of vapor cells. Within the different, a low-power beam traces overlapping V-shaped paths, passing 46 occasions by means of a single vapor cell.

In each gadgets, the researchers place within the beamline a half-waveplate—an optical element that rotates the sunshine’s polarization route 180°. This shift cancels out any polarization sign printed on the beam by a uniform background discipline, that means discipline gradients from weak, close by sources stand out. Measuring such sources might be helpful for functions that embody long-range radio-frequency communication and navigation, low-field nuclear magnetic resonance, and darkish matter detection.

–Marric Stephens

Marric Stephens is a Corresponding Editor for Physics Journal based mostly in Bristol, UK.


  1. R. J. Cooper et al., “Intrinsic radio-frequency gradiometer,” Phys. Rev. A 106, 053113 (2022).

Topic Areas

MagnetismAtomic and Molecular Physics

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