SRF2021 - List of Authors (Steder, L.)

Paper	Title	Page
SUPTEV006	Commissioning of a Calibration Device for Second Sound Quench Detection	124
	L. Ebeling, D. Reschke, L. Steder DESY, Hamburg, Germany W. Hillert University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	An important part of research and development in the field of superconducting radio frequency technology is the quench detection since these breakdowns of superconductivity often limit the cavity performance. Although the second sound based quench detection is widely used, only few studies dealing with its systematic uncertainties exist. Hence, the vertical test stands at the cavity test facility of DESY were extended by calibration device prototypes in order to estimate the accuracy of this method. For the first time at DESY, artificial signals have been generated and reconstructed by heating power film resistors. These second sound signals are determined using noise canceling algorithms and the existing reconstruction software. To evaluate the reconstructed positions, the absolute distance between reconstructed and true coordinates is calculated. Thus, a first uncertainty map of the cavity surface is created to quantify the reconstruction results of actual cavity quenches including systematic effects of the quench positioning like the varying sensor coverage around the cavity.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV006
About •	Received ※ 20 June 2021 — Revised ※ 09 July 2021 — Accepted ※ 20 November 2021 — Issue date ※ 30 April 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPTEV009	Development of a New B-Mapping System for SRF Cavity Vertical Tests	137
	J.C. Wolff, A. Gössel, C. Müller, D. Reschke, L. Steder, D. Tischhauser DESY, Hamburg, Germany W. Hillert, J.C. Wolff University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program. Magnetic flux trapped in the Niobium bulk material of superconducting radio frequency (SRF) cavities degrades their quality factor and the accelerating gradient. The sensitivity of the cavity to trapped magnetic flux is mainly determined by the treatment, the geometry and the Niobium grain size and orientation. To potentially improve the flux expulsion characteristics of SRF cavities and hence the efficiency of future accelerator facilities, further studies of the trapping behavior are essential. For this purpose a so-called B-mapping system to monitor the magnetic flux along the outer cavity surface of 1.3 GHz TESLA-Type single-cell SRF cavities is currently under development at DESY. Contrary to former approaches, this system digitizes the sensor signals already inside of the cryostat to extensively reduce the number of required cable feedthroughs. Furthermore, the signal-to-noise ratio (SNR) and consequently the measuring sensitivity can be enhanced by shorter analog signal lines, less thermal noise and the Mu-metal shielding of the cryostat. In this contribution the design, the development process as well as first performance test results of the B-mapping system are presented.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV009
About •	Received ※ 01 July 2021 — Accepted ※ 31 March 2022 — Issue date ※ 09 April 2022
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TUOFDV03	Vacancy-Hydrogen Dynamics and Magnetic Impurities During Mid-T Bake	342
	M. Wenskat, C. Bate, D. Reschke, J. Schaffran, L. Steder, H. Weise DESY, Hamburg, Germany C. Bate, G.D.L. Semione, A. Stierle University of Hamburg, Hamburg, Germany M. Butterling, E. Hirschmann, M.O. Liedke, A. Wagner HZDR, Dresden, Germany J. Cizek Charles University, Prague, Czech Republic W. Hillert University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Positron annihilation measurements allow to study the hydrogen interaction with vacancies in a crystal lattice. Furthermore, the 3/2 ratio of the positronium annihilation can be used to identify local magnetic impurities in thin layers. Dynamic studies of these properties in annealing studies up to 300°C will be presented. The discussion is accompanied by X-ray reflectivity studies performed on single crystal samples to study the niobium oxide dissolution. The dynamics of magnetic impurities during a Mid-T bake will be presented, put into the context of cavity studies and a potential link to rf properties will be discussed.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUOFDV03
About •	Received ※ 23 June 2021 — Revised ※ 12 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 05 December 2021
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WEPCAV013	Occurring Dependency between Adjustable Coupling and Q₀ - Finding and Solving a Problem during Vertical Cavity Testing at DESY	619
	Y.F. Liu, C. Luo SARI-CAS, Pudong, Shanghai, People’s Republic of China D. Reschke, L. Steder, M. Wiencek DESY, Hamburg, Germany
	In the AMTF (Accelerator Module Test Facility) hall at DESY, various types of cavities have been tested for different accelerators and R&D projects during the last years. For R&D purposes, dedicated inserts with additional auxiliaries like a movable INPUT antenna can be used to perform accurate measurements at different temperatures between 1.4 K and 4 K. Since 2017 more than hundred vertical tests were conducted in these inserts without troubles besides rare expected occurrences of cold leaks or even rarer a loose antenna. However, in the last months, an unexpected dependency between the measured quality factor and the coupling coefficient ß has been observed. In order to understand the source of this measurement uncertainty, several different special checks have been performed. In a logical sequence of measurements with different cryostats, inserts and cavities the problem has been encircled and in the end was identified and solved. In this paper, the observed problem is described in detail as well as the entire path leading to its solution.
	Poster WEPCAV013 [1.078 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPCAV013
About •	Received ※ 18 June 2021 — Revised ※ 18 October 2021 — Accepted ※ 18 October 2021 — Issue date ※ 22 November 2021
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Commissioning of a Calibration Device for Second Sound Quench Detection

124

L. Ebeling, D. Reschke, L. Steder
DESY, Hamburg, Germany
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

An important part of research and development in the field of superconducting radio frequency technology is the quench detection since these breakdowns of superconductivity often limit the cavity performance. Although the second sound based quench detection is widely used, only few studies dealing with its systematic uncertainties exist. Hence, the vertical test stands at the cavity test facility of DESY were extended by calibration device prototypes in order to estimate the accuracy of this method. For the first time at DESY, artificial signals have been generated and reconstructed by heating power film resistors. These second sound signals are determined using noise canceling algorithms and the existing reconstruction software. To evaluate the reconstructed positions, the absolute distance between reconstructed and true coordinates is calculated. Thus, a first uncertainty map of the cavity surface is created to quantify the reconstruction results of actual cavity quenches including systematic effects of the quench positioning like the varying sensor coverage around the cavity.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV006

About •

Received ※ 20 June 2021 — Revised ※ 09 July 2021 — Accepted ※ 20 November 2021 — Issue date ※ 30 April 2022

Cite •

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

SUPTEV009

Development of a New B-Mapping System for SRF Cavity Vertical Tests

137

J.C. Wolff, A. Gössel, C. Müller, D. Reschke, L. Steder, D. Tischhauser
DESY, Hamburg, Germany
W. Hillert, J.C. Wolff
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program.
Magnetic flux trapped in the Niobium bulk material of superconducting radio frequency (SRF) cavities degrades their quality factor and the accelerating gradient. The sensitivity of the cavity to trapped magnetic flux is mainly determined by the treatment, the geometry and the Niobium grain size and orientation. To potentially improve the flux expulsion characteristics of SRF cavities and hence the efficiency of future accelerator facilities, further studies of the trapping behavior are essential. For this purpose a so-called B-mapping system to monitor the magnetic flux along the outer cavity surface of 1.3 GHz TESLA-Type single-cell SRF cavities is currently under development at DESY. Contrary to former approaches, this system digitizes the sensor signals already inside of the cryostat to extensively reduce the number of required cable feedthroughs. Furthermore, the signal-to-noise ratio (SNR) and consequently the measuring sensitivity can be enhanced by shorter analog signal lines, less thermal noise and the Mu-metal shielding of the cryostat. In this contribution the design, the development process as well as first performance test results of the B-mapping system are presented.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV009

About •

Received ※ 01 July 2021 — Accepted ※ 31 March 2022 — Issue date ※ 09 April 2022

Cite •

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

TUOFDV03

Vacancy-Hydrogen Dynamics and Magnetic Impurities During Mid-T Bake

342

M. Wenskat, C. Bate, D. Reschke, J. Schaffran, L. Steder, H. Weise
DESY, Hamburg, Germany
C. Bate, G.D.L. Semione, A. Stierle
University of Hamburg, Hamburg, Germany
M. Butterling, E. Hirschmann, M.O. Liedke, A. Wagner
HZDR, Dresden, Germany
J. Cizek
Charles University, Prague, Czech Republic
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Positron annihilation measurements allow to study the hydrogen interaction with vacancies in a crystal lattice. Furthermore, the 3/2 ratio of the positronium annihilation can be used to identify local magnetic impurities in thin layers. Dynamic studies of these properties in annealing studies up to 300°C will be presented. The discussion is accompanied by X-ray reflectivity studies performed on single crystal samples to study the niobium oxide dissolution. The dynamics of magnetic impurities during a Mid-T bake will be presented, put into the context of cavity studies and a potential link to rf properties will be discussed.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUOFDV03

About •

Received ※ 23 June 2021 — Revised ※ 12 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 05 December 2021

Cite •

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

WEPCAV013

Occurring Dependency between Adjustable Coupling and Q₀ - Finding and Solving a Problem during Vertical Cavity Testing at DESY

619

Y.F. Liu, C. Luo
SARI-CAS, Pudong, Shanghai, People’s Republic of China
D. Reschke, L. Steder, M. Wiencek
DESY, Hamburg, Germany

In the AMTF (Accelerator Module Test Facility) hall at DESY, various types of cavities have been tested for different accelerators and R&D projects during the last years. For R&D purposes, dedicated inserts with additional auxiliaries like a movable INPUT antenna can be used to perform accurate measurements at different temperatures between 1.4 K and 4 K. Since 2017 more than hundred vertical tests were conducted in these inserts without troubles besides rare expected occurrences of cold leaks or even rarer a loose antenna. However, in the last months, an unexpected dependency between the measured quality factor and the coupling coefficient ß has been observed. In order to understand the source of this measurement uncertainty, several different special checks have been performed. In a logical sequence of measurements with different cryostats, inserts and cavities the problem has been encircled and in the end was identified and solved. In this paper, the observed problem is described in detail as well as the entire path leading to its solution.

Poster WEPCAV013 [1.078 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPCAV013

About •

Received ※ 18 June 2021 — Revised ※ 18 October 2021 — Accepted ※ 18 October 2021 — Issue date ※ 22 November 2021

Cite •

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