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Crygenic sensors - Superconducting Quantum Interference Devices (SQUIDs)

Cryogenic sensors are based on physical phenomena such as superconductivity at low temperatures. Superconducting quantum interferometers (SQUIDs) allow physical quantities that can be converted into a magnetic flux to be measured. These quantities are primarily magnetic fields and magnetic material parameters, but also electric currents and temperatures. Cryogenic sensors and SQUIDs enable precision measurements in metrology and fundamental research, but they are also used in commercial measuring systems for materials research or applied geophysics.

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One of the main applications of SQUIDs are biomagnetic measurements such as magnetoencephalography or low-field MRI. These applications require the operation of SQUID systems in low-noise cryogenic vessels to be able to detect the magnetic signals of the human body sensitively. Due to the special design of the cryogenic vessel, its noise contribution has been minimized to a negligible level, and record noise values of less than 200 aT Hz-1/2 have been attained.

Further innovations in this field can be attained by improving the manufacturing possibilities. To this end, the Josephson junctions have been miniaturized down to nanometer size, which has led to yet another noise reduction. This development has opened up new possibilities: novel SQUID systems can be set up and thus, new applications, both in biomagnetism and in fundamental research, are within reach.

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