Laureate
Dr. Ralph Delmdahl, Rainer Pätzel, Dr. Kai Schmidt, Coherent GmbH, Germany, Dr. Alexander Usoskin, Bruker HTS GmbH, Germany
Subject
"UV Excimer Laser Technology: Key to Massproduction of Ceramic High Temperature Superconducting Tapes" |
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| Dr. Alexander Usoskin, Dr. Ralph Delmdahl and Dr. Kai Schmidt with a second generation super conductor. |
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| | Thanks to quantum physics, electrical power transmission without loss has been a reality for a long time. The effect of superconductivity has been known since the beginning of the last century. The discovery of first-generation high-temperature superconductors in 1986 substantially increased the potential of the technology. |
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Using high-performance excimer lasers from laser specialist Coherent, the Bruker Corporation built a new plant in their superconductivity division for the second generation of high-temperature superconductors. These can be produced at a lower cost making them more attractive for use in power transmission in a so-called smart grid. Furthermore, the second generation is more tolerant to high magnetic fields and will replace the low-temperature superconductors used in magnetic resonance imaging devices to reduce the required cooling efforts.
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As a part of Bruker Corporation, Bruker HTS in Alzenau, Germany is the first company worldwide that managed to apply pulsed laser deposition (PLD) technology in mass production of superconductors. The people behind that development are Dr. Alexander Usoskin of Bruker HTS and three engineers of Coherent in Göttingen, Germany, Dr. Ralph Delmdahl, Rainer Pätzel and Dr. Kai Schmidt. | |
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| The target (YBCO). Illuminated with UV laser pulses ... |
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In pulsed laser deposition a pulsed UV laser beam with high energy vaporizes a target in a vacuum chamber, creating a plasma of the target material. Atom by atom the material from the plasma is deposited on an exposed substrate creating a very precisely controllable and extremely pure layer, e.g. of yttrium barium copper oxide (YBCO), a high-temperature super conductor. Deposited on a tape as substrate, a long quasi-single crystal is produced. The superconducting layer with a thickness of only a few micrometers can carry an electric load without energy loss that conventionally requires copper wire as thick as a finger. Unfortunately PLD could not be used for mass production of tapes as the yield was restricted with low deposition rates and also homogenous layers could not be produced on larger areas.
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| …vaporaizes and produces a plasma. The material from the plasma deposits on the substrate atom by atom. |
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| | The output of PLD was considered to be nonscalable. But with a number of patented inventions on the process and beam guidance the collaboration has managed to transfer the technology from a special niche to mass production. That requires not only the process and vacuum tube for large areas and high yield. A pivotal factor for upscaling the process is also the UV laser light source. |
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The laser delivers the required power for the process. An economically feasible production requires an excimer laser that combines high pulse stability with the highest possible power and long lifetime. Because the speed of the deposition process is limited by physics, an increase in speed can only be achieved by using several laser beams simultaneously creating a corresponding number of plasma plumes for deposition. The current installation uses six-fold splitting of the beam and an excimer laser with a stabilized average output power of 600 watts. Worldwide there is no other manufacturer of lasers that allow PLD scaling to mass production. | |
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| The conventional coper wire (right) and super conducting tape transport the same electrical power. |
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