Take-off and recovery current measurements of NbTi superconductors in helium bath and forced flow cooling
Description
Magnetic field dependent take-off and recovery current measurements of NbTi/Cu superconductor samples with different copper-to-superconductor ratios (α) were performed to determine their stability behavior. A special measuring method was used in which the superconductor was led to normal conduction by raising the transport current. In this way it was shown in measurements conducted on variable sample lengths and differently cooled sample surfaces that take-off and recovery currents depend on the electrical matrix resistance, the thermal conductivity along the conductor, the nucleate boiling heat flux and the film boiling minimum. For the NbTi/Cu superconductor used the maximum nucleate boiling heat flux was found to be 0.68 +- 0.04 W/cm2 at a temperature difference of ΔT = 0.4 K between the conductor surface and the helium bath. Measurements performed in helium bath coolling compared with forced flow cooling showed the film boiling minimum to be reduced strongly by forced flow cooling. (orig.)
Availability note (English)
MF available from INIS under the Report Number.Abstract (German)
Magnetfeldabhaengige Take-off- und Recovery-Strommessungen wurden an NbTi/Cu-Supraleiterproben mit unterschiedlichem Kupferanteil (α) zur Bestimmung ihres Stabilitaetsverhaltens durchgefuehrt. Hierbei wurde ein besonderes Messverfahren angewandt, bei dem der Supraleiter durch Transportstromerhoehung in die Normalleitung gefuehrt wird. In Verbindung mit Messungen bei variierten Leiterlaengen und gekuehlter Leiteroberflaeche konnte gezeigt werden, dass die auf diese Weise gemessenen Take-off- und Recovery-Stroeme vom elektrischen Widerstand der Matrix, der Waermeleitung laengs des Leiters, dem maximalen Waermeuebergang zum Helium beim Blasensieden und dem Filmsiedeminimum bestimmt werden. Fuer den bei diesen Messungen benutzten NbTi/Cu-Supraleiter betraegt der maximale Waermeuebergang beim Blasensieden 0,68 +- 0,04 W/cm2 bei einer Temperaturdifferenz zwischen Leiteroberflaeche und Heliumbad von ΔT = 0,4 K. Vergleichende Messungen bei Heliumbad- und Zwangskuehlung ergaben, dass bei Zwangskuehlung das Minimum der Waermeflussdichte beim Filmsieden relativ stark reduziert wird. (orig.)
Files
Restricted
The record is publicly accessible, but files are restricted to users with access.
Additional details
Additional titles
- Original title (German)
- Take-off- und Recovery-Strommessungen an bad- und zwangsgekuehlten NbTi-Supraleitern
Publishing Information
- Imprint Pagination
- 38 p.
- Report number
- KFK--2811
INIS
- Country of Publication
- Germany
- Country of Input or Organization
- Germany
- INIS RN
- 12598050
- Subject category
- S71: CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS;
- Descriptors DEI
- DIRECT CURRENT; ELECTRIC CONDUCTIVITY; FORCED CONVECTION; HEAT FLUX; HELIUM; INTERMETALLIC COMPOUNDS; MAGNETIC FIELDS; NIOBIUM ALLOYS; STABILITY; STABILIZED SUPERCONDUCTORS; TITANIUM ALLOYS; ULTRALOW TEMPERATURE
- Descriptors DEC
- ALLOYS; CONVECTION; CURRENTS; ELECTRIC CURRENTS; ELECTRICAL PROPERTIES; ELEMENTS; ENERGY TRANSFER; HEAT TRANSFER; NONMETALS; PHYSICAL PROPERTIES; RARE GASES; SUPERCONDUCTORS; TRANSITION ELEMENT ALLOYS