NEW HIGH TECNOLOGY! Kalle Heiska science journalist
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New superconductor technology developed by VTT

VTT has long been working on technology based on superconductors which operate at extremely low temperatures. The development target has been the sensors needed in magnetic imaging of the brain, precision metres and indicators of electromagnetic radiation. One of the most recent breakthroughs is the nanotransistor developed by VTT, which operates in extreme cold. The transistor is particularly suitable for the measurement of small signals.

The transistor can be used to amplify outgoing signals of extremely sensitive electromagnetic radiation indicators. Other potential applications include astronomical measurements, security cameras and even a reform of the SI system of units.

Several physical phenomena can only be exploited at very low temperatures. The innovation, known as the Bloch Oscillating Transistor (BOT) operates at temperatures as low as 0.1 Kelvin (equivalent to 0.1 degrees Celsius above absolute zero). The advantage of such extreme cold is that there is little interference with the signals to be measured as the noise resulting from motion of atoms and electrons in the substance is small.

The transistor was invented at VTT. Its modelling, fabrication and trial measurements were accomplished in collaboration with the Low Temperature Laboratory of Helsinki University of Technology. The BOT transistor is based on a nanometric Josephson junction whose properties and applications are being actively researched by physicists around the world. The transistor developed by VTT provides a unique addition to the fascinating world of such objects.

It may be possible to utilise the new transistor in metrology, i.e. the branch of science concerned with measurement, as the comparison of very small currents (range one pA) is problematic with present methods. It may also be applicable as a comparison amplifier in the so-called quantum metrological experiment. Performing such a test would make it possible to define the SI system of units with natural constants, that is, with the speed of light, electronic charge and Planck's constant, which have the same value always and everywhere.

Antti Manninen, Group Leader at the Centre for Metrology and Accreditation (MIKES) is pictured beside the Josephson quantum voltage standard cooled by liquid helium.
High resolution image (913 Kb)
Photo: Jaani Nissilä

Another device suitable for use in the field of metrology is the quantum voltage standard developed by VTT, which maintains its value exactly constant when driven on the constant frequency of atomic clock. VTT's voltage standard makes the calibration comparisons needed in industry more effective and also enables measurements of alternating voltages. It is much easier to use than the present devices and actually operates million times faster – in less than a microsecond. Similar voltage standards have been developed in Germany and the USA. The competition in the development of such components is tough, and the Centre for Metrology and Accreditation intends to commercialize the invention to be internationally competitive.

The development work on the BOT transistor and the quantum voltage standard form part of the doctoral dissertation of VTT researcher Juha Hassel, which will be publicly defended at the Helsinki University of Technology on 9 November 2004. The supervisors of the dissertation are Professor Heikki Seppä of VTT and Professor Pertti Hakonen of TKK.

More information:

VTT Information Technology
Juha Hassel, Research
Tel. +358 9 456 6771, +358 50 367 3482
Centre for Metrology and Accreditation
Scientist Antti Manninen, Group Leader
Tel. +358 9 456 6272, +358 40 514 8658

Feel free to use all news. Photographs copyright Kalle Heiska.
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