SRF2015 - List of Authors (Schaffran, J.)

Paper	Title	Page
MOPB072	Characterization of Surface Defects on EXFEL Series and ILC-Higrade Cavities	281
	A. Navitski, E. Elsen, V. Myronenko, J. Schaffran, O. Turkot DESY, Hamburg, Germany Y. Tamashevich University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Funding: BMBF project 05H12GU9, Alexander von Humboldt Foundation, CRISP (No. 283745) and ”Construction of New Infrastructures-Preparatory Phase” ILC-HiGrade (No. 206711) of the EU 7th FP7/2007-2013 Programme. Inspection of the inner cavity surface by an optical system is an inexpensive and useful means for surface control and identification of critical or suspicious features. Optical inspection of around 100 EXFEL series and ILC-HiGrade cavities has been performed recently using the high-resolution OBACHT system. It is a semi-automated tool based on the Kyoto camera. To gain information about the 3D topography of surface features or defects, a replica technique has been applied additionally. This is a non-destructive surface-study method reaching resolution down to 1 μm by imprinting the details of the surface onto a hardened rubber. The footprint is subsequently investigated with a microscope or profilometer. Based on these studies, several defects on the surface have been found and classified. Most of the cavity failures leading e.g. to field limitations below 20 MV/m have been identified and corresponding feedback given to the production cycle. Typical surface features and defects as well as their influence on the cavity performance will be presented and discussed.
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MOPB079	Analysis of the Test Rate for European XFEL Series Cavities	316
	J. Schaffran, S. Aderhold, D. Reschke, L. Steder, N. Walker DESY, Hamburg, Germany L. Monaco INFN/LASA, Segrate (MI), Italy
	The main part of the superconducting European XFEL linear accelerator consists of 100 accelerator modules each containing eight RF-cavities. Before the installation to a module, all of these cavities will be tested at cryogenic temperatures in a vertical cryostat in the accelerator module test facility (AMTF) at DESY. This paper discusses the average vertical test rate at the present status. It should be 1 in the ideal case, but actually it’s observed to be approximately 1.5. Classification and analysis concerning the reasons for this deviation are given as well as suggestions for a reduction of the test rate for future production cycles.
	Poster MOPB079 [0.632 MB]
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MOPB086	Update and Status of Vertical Test Results of the European XFEL Series Cavities	337
	N. Walker, D. Reschke, J. Schaffran, L. Steder DESY, Hamburg, Germany L. Monaco INFN/LASA, Segrate (MI), Italy M. Wiencek IFJ-PAN, Kraków, Poland
	The series production by two industrial vendors of the 800 1.3-GHz superconducting cavities for the European XFEL has been on-going since the beginning of 2013 and will conclude towards the end of this year. As of publication some 740 cavities (~93%) have been produced at an average rate of 6 cavities per week. As part of the acceptance testing, all cavities have undergone at least one vertical RF test at 2K at the AMTF facility at DESY. The acceptance criterion for module assembly is based on the concept of a “usable gradient”, which is defined as the maximum field taking into account Q0 performance and allowed thresholds for field emission, as well as breakdown limits. Approximate 20% of the cavities have undergone further surface treatment in the DESY infrastructure to improve their usable gradient performance. In this paper we present the performance statistics of the vertical test results, as well as an analysis of the limiting criteria for the usable gradient, and finally the impact of the surface retreatment on both usable gradient and Q0.
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MOPB113	Study of the Evolution of Artificial Defects on the Surface of Niobium During Electrochemical and Chemical Polishing	433
	L. Monaco, P. Michelato INFN/LASA, Segrate (MI), Italy A. Navitski, J. Schaffran, W. Singer DESY, Hamburg, Germany C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy A.L. Prudnikava, Y. Tamashevich University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	The presence of defects on the inner surface of Nb superconducting RF structures might limit its final performance. For this reason, strict requirements are imposed during mechanical production of the cavities, specifically on the quality control of the inner surface of components, to avoid the presence of defects or scratches. Nevertheless, some defects may remain also after control or can arise from the following production steps. Understanding the evolution of the defect might shine new insight on its origin and help in defining possible repair techniques. This paper reports the topographical evolution of defects on a Nb sample polished with the standard recipe used for the 1.3 GHz cavities of the EXFEL project. Various artificial defects of different shape, dimensions, and thicknesses/depths, with geometrical characteristics similar to the one that may occur during the machining and handling of cavities, have been “ad hoc” produced on the sample of the same material used for the cell fabrication. Analysis shows the evolution of the shape and profile of the defects at the different polishing steps.
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Paper

Title

Page

Characterization of Surface Defects on EXFEL Series and ILC-Higrade Cavities

281

A. Navitski, E. Elsen, V. Myronenko, J. Schaffran, O. Turkot
DESY, Hamburg, Germany
Y. Tamashevich
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Funding: BMBF project 05H12GU9, Alexander von Humboldt Foundation, CRISP (No. 283745) and ”Construction of New Infrastructures-Preparatory Phase” ILC-HiGrade (No. 206711) of the EU 7th FP7/2007-2013 Programme.
Inspection of the inner cavity surface by an optical system is an inexpensive and useful means for surface control and identification of critical or suspicious features. Optical inspection of around 100 EXFEL series and ILC-HiGrade cavities has been performed recently using the high-resolution OBACHT system. It is a semi-automated tool based on the Kyoto camera. To gain information about the 3D topography of surface features or defects, a replica technique has been applied additionally. This is a non-destructive surface-study method reaching resolution down to 1 μm by imprinting the details of the surface onto a hardened rubber. The footprint is subsequently investigated with a microscope or profilometer. Based on these studies, several defects on the surface have been found and classified. Most of the cavity failures leading e.g. to field limitations below 20 MV/m have been identified and corresponding feedback given to the production cycle. Typical surface features and defects as well as their influence on the cavity performance will be presented and discussed.

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

MOPB079

Analysis of the Test Rate for European XFEL Series Cavities

316

J. Schaffran, S. Aderhold, D. Reschke, L. Steder, N. Walker
DESY, Hamburg, Germany
L. Monaco
INFN/LASA, Segrate (MI), Italy

The main part of the superconducting European XFEL linear accelerator consists of 100 accelerator modules each containing eight RF-cavities. Before the installation to a module, all of these cavities will be tested at cryogenic temperatures in a vertical cryostat in the accelerator module test facility (AMTF) at DESY. This paper discusses the average vertical test rate at the present status. It should be 1 in the ideal case, but actually it’s observed to be approximately 1.5. Classification and analysis concerning the reasons for this deviation are given as well as suggestions for a reduction of the test rate for future production cycles.

Poster MOPB079 [0.632 MB]

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

MOPB086

Update and Status of Vertical Test Results of the European XFEL Series Cavities

337

N. Walker, D. Reschke, J. Schaffran, L. Steder
DESY, Hamburg, Germany
L. Monaco
INFN/LASA, Segrate (MI), Italy
M. Wiencek
IFJ-PAN, Kraków, Poland

The series production by two industrial vendors of the 800 1.3-GHz superconducting cavities for the European XFEL has been on-going since the beginning of 2013 and will conclude towards the end of this year. As of publication some 740 cavities (~93%) have been produced at an average rate of 6 cavities per week. As part of the acceptance testing, all cavities have undergone at least one vertical RF test at 2K at the AMTF facility at DESY. The acceptance criterion for module assembly is based on the concept of a “usable gradient”, which is defined as the maximum field taking into account Q0 performance and allowed thresholds for field emission, as well as breakdown limits. Approximate 20% of the cavities have undergone further surface treatment in the DESY infrastructure to improve their usable gradient performance. In this paper we present the performance statistics of the vertical test results, as well as an analysis of the limiting criteria for the usable gradient, and finally the impact of the surface retreatment on both usable gradient and Q0.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

MOPB113

Study of the Evolution of Artificial Defects on the Surface of Niobium During Electrochemical and Chemical Polishing

433

L. Monaco, P. Michelato
INFN/LASA, Segrate (MI), Italy
A. Navitski, J. Schaffran, W. Singer
DESY, Hamburg, Germany
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
A.L. Prudnikava, Y. Tamashevich
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

The presence of defects on the inner surface of Nb superconducting RF structures might limit its final performance. For this reason, strict requirements are imposed during mechanical production of the cavities, specifically on the quality control of the inner surface of components, to avoid the presence of defects or scratches. Nevertheless, some defects may remain also after control or can arise from the following production steps. Understanding the evolution of the defect might shine new insight on its origin and help in defining possible repair techniques. This paper reports the topographical evolution of defects on a Nb sample polished with the standard recipe used for the 1.3 GHz cavities of the EXFEL project. Various artificial defects of different shape, dimensions, and thicknesses/depths, with geometrical characteristics similar to the one that may occur during the machining and handling of cavities, have been “ad hoc” produced on the sample of the same material used for the cell fabrication. Analysis shows the evolution of the shape and profile of the defects at the different polishing steps.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)