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New type of magnetometer tested in the shielding room of PTB Berlin


In the past few years, the development of highly sensitive atomic magnetometers has made considerable progress. At the National Institute of Standards and Technology/USA (NIST), optical micromagnetometers have been developed with methods initially invented for chip-scale atomic clocks. Such an optical micromagnetometer was tested in the magnetically shielded room BMSR-2 of PTB Berlin; this was carried out together with colleagues from NIST*).

Magnetocardiograms of the human heart and the relaxation of magnetic nanoparticles were measured successfully. Both are important routine laboratory measurements, which are usually performed with superconducting quantum interference devices (SQUID). For a direct comparison of the results, reference data were recorded simultaneously with the multichannel SQUID magnetometer installed in the BMSR-2.

The impressive quality of the data obtained confirms the suitability of these optical micromagnetometers for the upper picotesla range. Compared to SQUIDs, the optical sensors exhibited - as expected - a significantly higher noise level. The distinct advantage of these sensors lies, however, in their small design (< 1 cm3). This allows them to be installed at a small distance from the source in order to increase the signal strength. The room temperature operation of the sensor and its small size will allow a much simpler system design compared to other sensor types suitable for this measurement range. The fabrication of the sensor by use of microsystem technology could enable simple and cost-effective mass production. NIST plans the development of a multichannel system on the basis of the existing technology. Further tests of these sensors at PTB are planned.

* Svenja Knappe und John Kitching NIST, Time and Frequency Division, 325 Broadway, Boulder, CO 80305, USA

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