SRF2021 - List of Authors (Reschke, D.)

Paper	Title	Page
SUPFDV001	Update on Nitrogen Infusion Sample R&D at DESY	57
	C. Bate, A. Dangwal Pandey, A. Ermakov, B. Foster, T.F. Keller, D. Reschke, J. Schaffran, S. Sievers, H. Weise, M. Wenskat DESY, Hamburg, Germany B. Foster Oxford University, Physics Department, Oxford, Oxon, United Kingdom W. Hillert, M. Wenskat University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Many accelerator projects such as the European XFEL cw upgrade or the ILC, would benefit from cavities with reduced surface resistance (high Q-values) while maintaining a high accelerating gradient. A possible way to meet the requirements is the so-called nitrogen-infusion procedure on Niobium cavities. However, a fundamental understanding and a theoretical model of this method are still missing. The approach shown here is based on R\&D using small samples, with the goal of identifying all key parameters of the process and establishing a stable, reproducible recipe. To understand the underlying processes of the surface evolution that give improved cavity performance, advanced surface-analysis techniques (e.g. SEM/EDX, TEM, XPS, TOF-SIMS) are utilized and several kinds of samples are analyzed. Furthermore, parameters such as RRR and the surface critical magnetic field denoted as H_c3 have been investigated. For this purpose, a small furnace dedicated to sample treatment was set up to change and explore the parameter space of the infusion recipe. Results of these analyses and their implications for the R\&D on cavities are presented.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV001
About •	Received ※ 22 June 2021 — Accepted ※ 03 January 2022 — Issue date ※ 27 April 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

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
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)

TUPTEV011	SRF Accelerating Modules Repair at DESY	508
	D. Kostin, J. Eschke, K. Jensch, N. Krupka, L. Lilje, A. Muhs, D. Reschke, S. Saegebarth, J. Schaffran, M. Schalwat, P. Schilling, M. Schmökel, S. Sievers, N. Steinhau-Kühl, E. Vogel, H. Weise, M. Wiencek, B. van der Horst DESY, Hamburg, Germany
	Eight SRF cavities assembled in an accelerating module represent a building block of the particle linear accelerator based on TESLA SRF technology. DESY has two machines, European XFEL and FLASH. Both use almost same module and cavity types. During the module assembly many factors can deteriorate the cavity performance and cause a need for a repair action. Currently two European XFEL modules and two FLASH ones underwent reassembly procedures. The repair was not immediately successful on every of these modules and re-iterations did follow. The degradation causes were investigated. SRF modules were tested on both test-stands at DESY: AMTF and CMTB. The results of the described actions are presented and discussed.
	Poster TUPTEV011 [1.499 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPTEV011
About •	Received ※ 18 June 2021 — Accepted ※ 19 November 2021 — Issue date ※ 01 February 2022
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)

THPFDV001	Status of the New Quadrupole Resonator for SRF R&D	751
	R. Monroy-Villa, W. Hillert, M. Wenskat University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany S. Gorgi Zadeh, P. Putek Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany M. Lemke, R. Monroy-Villa, D. Reschke, M. Röhling, J.H. Thie DESY, Hamburg, Germany
	A basic understanding of the properties of SRF samples under surface treatments would aid in the development of consistent theories. To study the RF properties of such samples under realistic superconducting-cavity-like conditions, a test device called Quadrupole Resonator (QPR) was fabricated. In this publication we report the status of the QPR at Universität Hamburg in collaboration with DESY. Our device is based on the QPRs operated at CERN and at HZB, and its design will allow for testing samples at temperatures between 2 K and 8 K, under magnetic fields up to 120 mT and with operating frequencies of 433 MHz, 866 MHz and 1300 MHz. Fabrication tolerance studies on the electromagnetic field distributions and simulations of the static detuning of the device, together with the commissioning report and the ongoing surface treatment, will be presented.
	Poster THPFDV001 [1.074 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPFDV001
About •	Received ※ 27 June 2021 — Revised ※ 23 August 2021 — Accepted ※ 23 August 2021 — Issue date ※ 29 April 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Update on Nitrogen Infusion Sample R&D at DESY

57

C. Bate, A. Dangwal Pandey, A. Ermakov, B. Foster, T.F. Keller, D. Reschke, J. Schaffran, S. Sievers, H. Weise, M. Wenskat
DESY, Hamburg, Germany
B. Foster
Oxford University, Physics Department, Oxford, Oxon, United Kingdom
W. Hillert, M. Wenskat
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Many accelerator projects such as the European XFEL cw upgrade or the ILC, would benefit from cavities with reduced surface resistance (high Q-values) while maintaining a high accelerating gradient. A possible way to meet the requirements is the so-called nitrogen-infusion procedure on Niobium cavities. However, a fundamental understanding and a theoretical model of this method are still missing. The approach shown here is based on R\&D using small samples, with the goal of identifying all key parameters of the process and establishing a stable, reproducible recipe. To understand the underlying processes of the surface evolution that give improved cavity performance, advanced surface-analysis techniques (e.g. SEM/EDX, TEM, XPS, TOF-SIMS) are utilized and several kinds of samples are analyzed. Furthermore, parameters such as RRR and the surface critical magnetic field denoted as H_c3 have been investigated. For this purpose, a small furnace dedicated to sample treatment was set up to change and explore the parameter space of the infusion recipe. Results of these analyses and their implications for the R\&D on cavities are presented.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV001

About •

Received ※ 22 June 2021 — Accepted ※ 03 January 2022 — Issue date ※ 27 April 2022

Cite •

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

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

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)

TUPTEV011

SRF Accelerating Modules Repair at DESY

508

D. Kostin, J. Eschke, K. Jensch, N. Krupka, L. Lilje, A. Muhs, D. Reschke, S. Saegebarth, J. Schaffran, M. Schalwat, P. Schilling, M. Schmökel, S. Sievers, N. Steinhau-Kühl, E. Vogel, H. Weise, M. Wiencek, B. van der Horst
DESY, Hamburg, Germany

Eight SRF cavities assembled in an accelerating module represent a building block of the particle linear accelerator based on TESLA SRF technology. DESY has two machines, European XFEL and FLASH. Both use almost same module and cavity types. During the module assembly many factors can deteriorate the cavity performance and cause a need for a repair action. Currently two European XFEL modules and two FLASH ones underwent reassembly procedures. The repair was not immediately successful on every of these modules and re-iterations did follow. The degradation causes were investigated. SRF modules were tested on both test-stands at DESY: AMTF and CMTB. The results of the described actions are presented and discussed.

Poster TUPTEV011 [1.499 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPTEV011

About •

Received ※ 18 June 2021 — Accepted ※ 19 November 2021 — Issue date ※ 01 February 2022

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)

THPFDV001

Status of the New Quadrupole Resonator for SRF R&D

751

R. Monroy-Villa, W. Hillert, M. Wenskat
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Gorgi Zadeh, P. Putek
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
M. Lemke, R. Monroy-Villa, D. Reschke, M. Röhling, J.H. Thie
DESY, Hamburg, Germany

A basic understanding of the properties of SRF samples under surface treatments would aid in the development of consistent theories. To study the RF properties of such samples under realistic superconducting-cavity-like conditions, a test device called Quadrupole Resonator (QPR) was fabricated. In this publication we report the status of the QPR at Universität Hamburg in collaboration with DESY. Our device is based on the QPRs operated at CERN and at HZB, and its design will allow for testing samples at temperatures between 2 K and 8 K, under magnetic fields up to 120 mT and with operating frequencies of 433 MHz, 866 MHz and 1300 MHz. Fabrication tolerance studies on the electromagnetic field distributions and simulations of the static detuning of the device, together with the commissioning report and the ongoing surface treatment, will be presented.

Poster THPFDV001 [1.074 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPFDV001

About •

Received ※ 27 June 2021 — Revised ※ 23 August 2021 — Accepted ※ 23 August 2021 — Issue date ※ 29 April 2022

Cite •

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