SRF2019 - List of Authors (Weise, H.)

Paper	Title	Page
MOP023	Nitrogen Infusion Sample R&D at DESY	77
SUSP002	use link to see paper's listing under its alternate paper code
	C. Bate, A. Dangwal Pandey, A. Ermakov, B. Foster, T.F. Keller, D. Reschke, J. Schaffran, S. Sievers, N. Walker, H. Weise, M. Wenskat DESY, Hamburg, Germany W. Hillert University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany G.D.L. Semione, V. Vonk DESY Nanolab, FS-NL, Hamburg, Germany A. Stierle University of Hamburg, Hamburg, Germany
	The European XFEL continuous wave upgrade requires cavities with reduced surface resistance (high Q-values) for high duty cycle while maintaining high accelerating gradient for short-pulse operation. A possible way to meet the requirements is the so-called nitrogen infusion procedure. However, a fundamental understanding and a theoretical model of this method are still missing. The approach shown here is based on sample R&D, with the goal to identify key parameters of the process and establish a stable, reproducible recipe. To understand the underlying processes of the surface evolution, which gives improved cavity performance, advanced surface analysis techniques (e.g. SEM/EDX, TEM, XPS, TOF-SIMS) are utilized. Additionally, a small furnace just for samples was set up to change and explore the parameter space of the infusion recipe. Results of these analyses, their implications for the cavity R&D and next steps are presented.
	Poster MOP023 [3.759 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP023
About •	paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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MOP024	Vacancy-Hydrogen Dynamics in Samples During Low Temperature Baking	83
	M. Wenskat, C. Bate, D. Reschke, H. Weise DESY, Hamburg, Germany C. Bate University of Hamburg, Hamburg, Germany M. Butterling, E. Hirschmann, M.O. Liedke, A. Wagner HZDR, Dresden, Germany J. Cizek Charles University, Prague, Czech Republic
	Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program and by the BMBF under the research grant 05H18GURB1. The recent discovery of a modified low temperature baking process lead to a reduction of surface losses and an increase of the accelerating gradient of TESLA shape cavities. The hypothesis linking the accelerator performance and the treatment is the suppression of lossy nanohydrides via defect trapping, with vacancy-hydrogen complexes forming at the lower temperatures. Utilizing Doppler broadening Positron Annihilation Spectroscopy and Positron Annihilation Lifetime Spectroscopy samples made from European XFEL niobium sheets and cavity cut-outs were investigated. The evolution of vacancies, hydrogen and their interaction at different temperature levels have been studied during in-situ annealing. Measurements of niobium samples and a correlation between RF, material properties, and V-H distribution in cavity cut-outs has been done.
	Poster MOP024 [1.087 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP024
About •	paper received ※ 20 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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MOP034	European XFEL: Accelerating Module Repair at DESY	127
	D. Kostin, J. Eschke, K. Jensch, N. Krupka, 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
	The European XFEL is in operation since 2017. The design projected energy of 17.5 GeV was reached, even with the last 4 main linac accelerating modules not yet installed. 2 out of 4 not installed modules did suffer from strong cavity performance degradation, namely increased field emission, and required surface processing. The first of two modules is reassembled and tested. The module test results confirm a successful repair action. The module repair and test steps are described together with cavities performance evolution.
	Poster MOP034 [1.863 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP034
About •	paper received ※ 17 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUFUA6	Surface Analysis of Niobium After Thermal/Gas Treatments via Samples - Review
	A. Dangwal Pandey, T.F. Keller, H. Noei, D. Reschke, J. Schaffran, G.D.L. Semione, V. Vonk, H. Weise, M. Wenskat DESY, Hamburg, Germany C. Bate, A. Stierle University of Hamburg, Hamburg, Germany
	Thermal treatments of SRF Nb cavities - including the well-established 120°C bake and the recently reported N-infusion - are shown to improve the cavity performance significantly; however, the underlying physical phenomenon is not fully understood. A short review will be presented on surface characterization of niobium material subjected to various thermal and gas exposure protocols and how the findings correlate with observed SRF properties. Moreover, recent results obtained on single-crystal Nb samples - heated in different vacuum environments and characterised by means of X-ray photoelectron spectroscopy and grazing-incidence X-ray diffraction, electron microscopy, energy dispersive X-ray spectroscopy and time-of-flight secondary ion mass spectroscopy will be discussed.
	Slides TUFUA6 [6.968 MB]
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THP080	Status of the All Superconducting Gun Cavity at DESY	1087
	E. Vogel, S. Barbanotti, A. Brinkmann, Th. Buettner, J.I. Iversen, K. Jensch, D. Klinke, D. Kostin, W.-D. Möller, A. Muhs, J. Schaffran, M. Schmökel, J.K. Sekutowicz, S. Sievers, L. Steder, N. Steinhau-Kühl, A. Sulimov, J.H. Thie, H. Weise, M. Wenskat, M. Wiencek, L. Winkelmann, B. van der Horst DESY, Hamburg, Germany
	At DESY, the development of a 1.6-cell, 1.3 GHz all superconducting gun cavity with a lead cathode attached to its back wall is ongoing. The special features of the structure like the back wall of the half-cell and cathode hole require adaptations of the procedures used for the treatment of nine-cell TESLA cavities. Unsatisfactory test results of two prototype cavities motivated us to re-consider the back-wall design and production steps. In this contribution we present the status of the modified cavity design including accessories causing accelerating field asymmetries, like a pick up antenna located at the back wall and fundamental power- and HOM couplers. Additionally, we discuss preliminary considerations for the compensation of kicks caused by these components.
	Poster THP080 [7.365 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP080
About •	paper received ※ 20 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

MOP023

Nitrogen Infusion Sample R&D at DESY

77

SUSP002

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

C. Bate, A. Dangwal Pandey, A. Ermakov, B. Foster, T.F. Keller, D. Reschke, J. Schaffran, S. Sievers, N. Walker, H. Weise, M. Wenskat
DESY, Hamburg, Germany
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
G.D.L. Semione, V. Vonk
DESY Nanolab, FS-NL, Hamburg, Germany
A. Stierle
University of Hamburg, Hamburg, Germany

The European XFEL continuous wave upgrade requires cavities with reduced surface resistance (high Q-values) for high duty cycle while maintaining high accelerating gradient for short-pulse operation. A possible way to meet the requirements is the so-called nitrogen infusion procedure. However, a fundamental understanding and a theoretical model of this method are still missing. The approach shown here is based on sample R&D, with the goal to identify key parameters of the process and establish a stable, reproducible recipe. To understand the underlying processes of the surface evolution, which gives improved cavity performance, advanced surface analysis techniques (e.g. SEM/EDX, TEM, XPS, TOF-SIMS) are utilized. Additionally, a small furnace just for samples was set up to change and explore the parameter space of the infusion recipe. Results of these analyses, their implications for the cavity R&D and next steps are presented.

Poster MOP023 [3.759 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP023

About •

paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

Export •

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

MOP024

Vacancy-Hydrogen Dynamics in Samples During Low Temperature Baking

83

M. Wenskat, C. Bate, D. Reschke, H. Weise
DESY, Hamburg, Germany
C. Bate
University of Hamburg, Hamburg, Germany
M. Butterling, E. Hirschmann, M.O. Liedke, A. Wagner
HZDR, Dresden, Germany
J. Cizek
Charles University, Prague, Czech Republic

Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program and by the BMBF under the research grant 05H18GURB1.
The recent discovery of a modified low temperature baking process lead to a reduction of surface losses and an increase of the accelerating gradient of TESLA shape cavities. The hypothesis linking the accelerator performance and the treatment is the suppression of lossy nanohydrides via defect trapping, with vacancy-hydrogen complexes forming at the lower temperatures. Utilizing Doppler broadening Positron Annihilation Spectroscopy and Positron Annihilation Lifetime Spectroscopy samples made from European XFEL niobium sheets and cavity cut-outs were investigated. The evolution of vacancies, hydrogen and their interaction at different temperature levels have been studied during in-situ annealing. Measurements of niobium samples and a correlation between RF, material properties, and V-H distribution in cavity cut-outs has been done.

Poster MOP024 [1.087 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP024

About •

paper received ※ 20 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

Export •

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

MOP034

European XFEL: Accelerating Module Repair at DESY

127

D. Kostin, J. Eschke, K. Jensch, N. Krupka, 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

The European XFEL is in operation since 2017. The design projected energy of 17.5 GeV was reached, even with the last 4 main linac accelerating modules not yet installed. 2 out of 4 not installed modules did suffer from strong cavity performance degradation, namely increased field emission, and required surface processing. The first of two modules is reassembled and tested. The module test results confirm a successful repair action. The module repair and test steps are described together with cavities performance evolution.

Poster MOP034 [1.863 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP034

About •

paper received ※ 17 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019

Export •

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

TUFUA6

Surface Analysis of Niobium After Thermal/Gas Treatments via Samples - Review

A. Dangwal Pandey, T.F. Keller, H. Noei, D. Reschke, J. Schaffran, G.D.L. Semione, V. Vonk, H. Weise, M. Wenskat
DESY, Hamburg, Germany
C. Bate, A. Stierle
University of Hamburg, Hamburg, Germany

Thermal treatments of SRF Nb cavities - including the well-established 120°C bake and the recently reported N-infusion - are shown to improve the cavity performance significantly; however, the underlying physical phenomenon is not fully understood. A short review will be presented on surface characterization of niobium material subjected to various thermal and gas exposure protocols and how the findings correlate with observed SRF properties. Moreover, recent results obtained on single-crystal Nb samples - heated in different vacuum environments and characterised by means of X-ray photoelectron spectroscopy and grazing-incidence X-ray diffraction, electron microscopy, energy dispersive X-ray spectroscopy and time-of-flight secondary ion mass spectroscopy will be discussed.

Slides TUFUA6 [6.968 MB]

Export •

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

THP080

Status of the All Superconducting Gun Cavity at DESY

1087

E. Vogel, S. Barbanotti, A. Brinkmann, Th. Buettner, J.I. Iversen, K. Jensch, D. Klinke, D. Kostin, W.-D. Möller, A. Muhs, J. Schaffran, M. Schmökel, J.K. Sekutowicz, S. Sievers, L. Steder, N. Steinhau-Kühl, A. Sulimov, J.H. Thie, H. Weise, M. Wenskat, M. Wiencek, L. Winkelmann, B. van der Horst
DESY, Hamburg, Germany

At DESY, the development of a 1.6-cell, 1.3 GHz all superconducting gun cavity with a lead cathode attached to its back wall is ongoing. The special features of the structure like the back wall of the half-cell and cathode hole require adaptations of the procedures used for the treatment of nine-cell TESLA cavities. Unsatisfactory test results of two prototype cavities motivated us to re-consider the back-wall design and production steps. In this contribution we present the status of the modified cavity design including accessories causing accelerating field asymmetries, like a pick up antenna located at the back wall and fundamental power- and HOM couplers. Additionally, we discuss preliminary considerations for the compensation of kicks caused by these components.

Poster THP080 [7.365 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP080

About •

paper received ※ 20 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019

Export •

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