SRF2011 - List of Authors (Aull, S.)

Paper

Title

Page

Study of Trapped Magnetic Flux in Superconducting Niobium Samples

702

S. Aull, J. Knobloch, O. Kugeler
HZB, Berlin, Germany

Trapped magnetic flux is known to be one cause of residual losses in an SRF cavity. An ambient magnetic field is trapped in the material when lattice defects inhibit the expulsion of the field during the transition into the Meissner phase. We measured the fraction of trapped magnetic flux in niobium samples with different treatment histories, such as BCP and tempering. The differences between single crystal and polycrystalline material as well as the influence of local temperature gradients and different cooling rates were investigated. In addition, the progression of the release of a trapped field during warm up was studied. It was found that different fractions of an applied field were trapped due to heat treatment. Differences between single crystal and polycrystalline material were also observed. Additionally, single crystal samples showed a logarithmic dependency on the cooling rate. It was demonstrated that a local temperature gradient produces an additional magnetic field which has impact on the flux trapping.

Poster THPO006 [1.436 MB]

Paper	Title	Page
THPO006	Study of Trapped Magnetic Flux in Superconducting Niobium Samples	702
	S. Aull, J. Knobloch, O. Kugeler HZB, Berlin, Germany
	Trapped magnetic flux is known to be one cause of residual losses in an SRF cavity. An ambient magnetic field is trapped in the material when lattice defects inhibit the expulsion of the field during the transition into the Meissner phase. We measured the fraction of trapped magnetic flux in niobium samples with different treatment histories, such as BCP and tempering. The differences between single crystal and polycrystalline material as well as the influence of local temperature gradients and different cooling rates were investigated. In addition, the progression of the release of a trapped field during warm up was studied. It was found that different fractions of an applied field were trapped due to heat treatment. Differences between single crystal and polycrystalline material were also observed. Additionally, single crystal samples showed a logarithmic dependency on the cooling rate. It was demonstrated that a local temperature gradient produces an additional magnetic field which has impact on the flux trapping.
	Poster THPO006 [1.436 MB]