Regensburg 2004 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
TT: Tiefe Temperaturen
TT 12: Supraleitung: Anwendungen, Materialien, technische Supraleiter, Bauelemente
TT 12.2: Vortrag
Dienstag, 9. März 2004, 14:45–15:00, H20
Fast active high power switches on YBCO thin films — •Alois Hiebl1, Kai Nummsen1, Helmut Kinder1, Werner Weck2, Anton Müller2, and Hermann Schölderle2 — 1TU München, Physik Department E10, 85748 Garching — 2Fa. Magnet Motor, Petersbrunner Str. 2, 82139 Starnberg
YBCO thin films have excellent switching properties at high power levels and within microsecond time scale. We have studied the possibility of using YBCO thin films not only as passive switches, as in the case of resistive fault current limiters (FCL), but also as actively switchable devices. We have investigated a new switching method with a radio frequency (RF) trigger pulse directly applied to the superconducting strip itself. The RF magnetic field is applied by various types of coils at frequencies in the MHz - kHz range. The samples were prepared by thermal co-evaporation on sapphire substrates in the form of strips with dimensions 10 mm x 42 mm and a thickness of 300 nm. No normal conducting topcoat was used to retain higher switching powers. They were submerged in liquid nitrogen and biased by a dc current. We observe the onset of a dc voltage drop along the superconductor simultaneously with the leading edge of the RF pulse. This voltage drop continues to increase over several microseconds until the YBCO film switches into the normal state. We present measurements for the frequency dependence of the switching time, which decreases from 10 kHz to 45 MHz. For the RF induced heating we present a theoretical explanation which we proved with a new experimental setup. With the new setup short switching times are also achievable, using a trigger pulse in the kHz range.