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• 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 as we speak’s cryogenically cooled superconducting quantum interference units, researchers have employed many numerous 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 units 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 fuel 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, exhibiting up as a change within the polarization path of the probe beam—a second, linearly polarized laser that can also be transmitted by the fuel.
Within the units devised by Cooper and his colleagues, the probe beam makes a number of passes by the alkali fuel, maximizing the system’s sensitivity to weak fields. In a single setup, a high-power probe beam takes a single M-shaped route by the fuel, passing twice by a pair of vapor cells. Within the different, a low-power beam traces overlapping V-shaped paths, passing 46 instances by a single vapor cell.
In each units, the researchers place within the beamline a half-waveplate—an optical element that rotates the sunshine’s polarization path 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 may very well be helpful for purposes 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 primarily based in Bristol, UK.
References
- R. J. Cooper et al., “Intrinsic radio-frequency gradiometer,” Phys. Rev. A 106, 053113 (2022).
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