SRF2023 - List of Authors (Kubo, T.)

Paper	Title	Page
TUCXA01	Study of the Dynamics of Flux Trapping in Different SRF Materials	380
	F. Kramer, S. Keckert, J. Knobloch, O. Kugeler HZB, Berlin, Germany J. Knobloch University of Siegen, Siegen, Germany T. Kubo KEK, Ibaraki, Japan
	A dedicated experimental setup to measure magnetic flux dynamics and trapped flux in samples is used to precisely map out how trapped flux is influenced by different parameters. The setup allows for rapid thermal cycling of the sample so that effects of cooldown parameters can be investigated in detail. We show how temperature gradient, cooldown rate, and the magnitude of external field influence trapped flux in large grain, fine grain and coated niobium samples. The detailed measurements show unexpected results, namely that too fast cooldowns increase trapped flux, large grain material traps flux only when the external field is larger than a temperature gradient dependent threshold field, and the measured dependence of trapped flux on temperature gradient does not agree with an existing model. Therefore, a new model is presented which agrees better with the measured results.
	Slides TUCXA01 [3.180 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUCXA01
About •	Received ※ 17 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 26 June 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTB002	Modelling Trapped Flux in Niobium	393
SUSPB017	use link to see paper's listing under its alternate paper code
	F. Kramer, S. Keckert, J. Knobloch, O. Kugeler HZB, Berlin, Germany J. Knobloch University of Siegen, Siegen, Germany T. Kubo KEK, Ibaraki, Japan
	Detailed measurements of magnetic flux dynamics and trapped magnetic flux in niobium samples were conducted with a new experimental setup that permits precise control of the cooldown parameters. With this setup the dependency of trapped flux on the temperature gradient, external magnetic field, and cooldown rate can be mapped out in more detail compared to cavity measurements. We have obtained unexpected results, and an existing model describing trapped flux in dependence of temperature gradient does not agree with the measured data. Therefore, a new model is developed which describes the magnitude of trapped flux in dependence of the temperature gradient across the sample during cooldown. The model describes the amount of trapped flux lines with help of a density distribution function of the pinning forces of pinning centers and the thermal force which can de-pin flux lines from pinning centers. The model shows good agreement with the measured data and correctly predicts trapped flux at different external flux densities.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB002
About •	Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 13 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Study of the Dynamics of Flux Trapping in Different SRF Materials

380

F. Kramer, S. Keckert, J. Knobloch, O. Kugeler
HZB, Berlin, Germany
J. Knobloch
University of Siegen, Siegen, Germany
T. Kubo
KEK, Ibaraki, Japan

A dedicated experimental setup to measure magnetic flux dynamics and trapped flux in samples is used to precisely map out how trapped flux is influenced by different parameters. The setup allows for rapid thermal cycling of the sample so that effects of cooldown parameters can be investigated in detail. We show how temperature gradient, cooldown rate, and the magnitude of external field influence trapped flux in large grain, fine grain and coated niobium samples. The detailed measurements show unexpected results, namely that too fast cooldowns increase trapped flux, large grain material traps flux only when the external field is larger than a temperature gradient dependent threshold field, and the measured dependence of trapped flux on temperature gradient does not agree with an existing model. Therefore, a new model is presented which agrees better with the measured results.

Slides TUCXA01 [3.180 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUCXA01

About •

Received ※ 17 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 26 June 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTB002

Modelling Trapped Flux in Niobium

393

SUSPB017

use link to see paper's listing under its alternate paper code

F. Kramer, S. Keckert, J. Knobloch, O. Kugeler
HZB, Berlin, Germany
J. Knobloch
University of Siegen, Siegen, Germany
T. Kubo
KEK, Ibaraki, Japan

Detailed measurements of magnetic flux dynamics and trapped magnetic flux in niobium samples were conducted with a new experimental setup that permits precise control of the cooldown parameters. With this setup the dependency of trapped flux on the temperature gradient, external magnetic field, and cooldown rate can be mapped out in more detail compared to cavity measurements. We have obtained unexpected results, and an existing model describing trapped flux in dependence of temperature gradient does not agree with the measured data. Therefore, a new model is developed which describes the magnitude of trapped flux in dependence of the temperature gradient across the sample during cooldown. The model describes the amount of trapped flux lines with help of a density distribution function of the pinning forces of pinning centers and the thermal force which can de-pin flux lines from pinning centers. The model shows good agreement with the measured data and correctly predicts trapped flux at different external flux densities.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB002

About •

Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 13 July 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)