SRF2013 - List of Authors (Singer, X.)

Paper

Title

Page

Statistic to Eddy-Current Scanning of Niobium Sheets for European XFEL

171

A. Brinkmann, S. Arnold, A. Ermakov, J. Iversen, M. Lengkeit, A. Poerschmann, L. Schaefer, W. Singer, X. Singer
DESY, Hamburg, Germany

The fabrication experiences of superconducting cavities for FLASH have shown that eddy-current scanning of the Nb-sheets foreseen for half-cells reduces the cavity failures. New eddy current devices have been developed and build together with the industry for the production of 800 pieces 1.3 GHz superconducting niobium cavities for European XFEL. More than 15.000 Nb-sheets provided by three companies have been tested by eddy-current scanning. The sheets that demonstrated local deviations of the signal have been subsequently non-destructively examined by 3d-microscope and X-Ray element analysis. The surface defects (dents, holes, scratches) are the mainly detected flaws. In addition several types of foreign material inclusions observed. Statistic concerning eddy-current signal deviation and rejection rates for each supplier will be presented.

MOP043

ILC-HiGrade Cavities as a Tool of Quality Control for European XFEL

212

A. Navitski, E. Elsen, B. Foster, J. Iversen, A. Matheisen, D. Reschke, W. Singer, X. Singer, L. Steder, M. Wenskat
DESY, Hamburg, Germany
R. Laasch, Y. Tamashevich
University of Hamburg, Hamburg, Germany

Funding: BMBF, Helmholtz Association, ILC-HiGrade, FP7 (CRISP), Alexander von Humboldt Stiftung/Foundation
The EXFEL order for SRF cavities includes 24 cavities, which are part of the ILC-HiGrade program. Initially, these cavities serve as quality control (QC) sample extracted from the EXFEL cavities series production on a regular basis. The QC and quality assurance (QA) include all processing steps of the EXFEL cavities. To maximize the information from these so-called QC cavities, a surface mapping technique is applied in a second cold RF test. There the cavities delivered have experienced identical treatment of the inner surface with the exception of mounting of the Helium vessel. After the normal acceptance test at the cavity RF measurement facility, the cavities are removed from the production flow. Further quality assurance steps beginning with a detailed RF test with surface mapping followed by a high resolution optical inspection (OBACHT) are carried out to improve the understanding of defects in close collaboration with the standing experts engaged in the EXFEL production. Results of the first QC cavities tests as well as planned further R&D will be presented and discussed.

MOP050

Strategy and Experiences on Procurement of Material for European XFEL Cavities

X. Singer, J. Iversen, W. Singer
DESY, Hamburg, Germany
F. Gaus, K-H. Marrek
TÜV NORD Systems GmbH & Co. KG, Hamburg, Germany

Analysis of the strategy for material procurement and quality management is done on base of the European XFEL experiences. In the preparation phase the requirements to material has been defined and the qualification of various companies as potential supplier for European XFEL executed. Estimation of the material for production of pressure bearing parts, creation of PMAs (particular material appraisal) acc. the European Pressure Equipment Directive and certification of the companies as producer of the material for pressure bearing parts has been done together with the notified body (TÜV NORD Systems). The procurement of material, QC, documentation, shipment and supervising the material workflow at cavity-producers has been carried out by DESY. Four companies produced ca. 25.000 semi-finished parts of high purity niobium and NbTi within of three years. Analysis of the main flaws and foreign material inclusions in niobium sheets is presented.

Poster MOP050 [1.609 MB]

MOP053

R&D on Cavity Treatments at DESY Towards the ILC Performance Goal

240

A. Navitski, E. Elsen, B. Foster, D. Reschke, J. Schaffran, W. Singer, X. Singer
DESY, Hamburg, Germany
R. Laasch, Y. Tamashevich
University of Hamburg, Hamburg, Germany

Funding: BMBF, Helmholtz Association, ILC-HiGrade, FP7 (CRISP), Alexander von Humboldt Stiftung/Foundation
The actual R&D program at DESY is derived from the global effort for the International Linear Collider (ILC) and is well in phase with effort elsewhere. The program aims at a solid understanding and control of the industrial mass-production process of the superconducting radio-frequency accelerating cavities, which are manufactured for the European X-ray Free Electron Laser (EXFEL) at DESY. The goal is to identify the gradient limiting factors and further refine the cavity treatment technique to provide gradients above 35 MV/m at >90% production yield. Techniques such as 2nd sound quench detection, OBACHT optical inspections, defect metrology using silicon replica as well as Centrifugal Barrel Polishing (CBP) and Local Grinding repair are foreseen as tools. Actual status, details, and first achievements of the program will be reported.

TUP024

Unloaded Quality Factor Qo of Prototype European XFEL Cavities, Large Grain and Hydroformed Cavities

A. Ermakov, W. Singer, X. Singer
DESY, Hamburg, Germany

A statistical analysis of the unloaded quality factor Q0 of TESLA shape cavities at low accelerating field (up to 5 MV/m) and medium accelerating field (5-20 MV/m) was done on base of available RF data for test series: single-cell and 9-cell large grain cavities, single cell and multi-cell hydroformed at DESY cavities, fine grain cavities-prototypes for European XFEL. On the one hand the purpose of statistical analysis is done to find the relationship between the parameters describing the behavior between unloaded quality factor Q0 (as function of the accelerated field Eacc) and main treatment procedures (Buffered Chemical Polishing BCP, Electropolishing EP, 120°C baking). On the other hand the relationship between Q0 and different types of cavities (cavities with reduced number of grain boundaries, cavities without equator welding seam, cavities of standard fine grain material) was evaluated. The non - linearity of the surface resistance in low and medium field regions analyzed for these types of cavities and compared with the available theoretical models.

TUP041

Large Grain DESY Cavities and Crystallographic Orientation of the Niobium Discs

X. Singer, W. Singer
DESY, Hamburg, Germany
K. Kazimierz
University of Mining and Metallurgy, Kraków, Poland

Eleven 9-cell Large Grain LG cavities have been produced and successfully RF tested at DESY. Analysis of the LG niobium discs for these cavities from the crystallographic orientation point of view will be presented. Surface behavior and roughness of the LG samples of different crystallographic orientation after buffered chemical polishing BCP have been studied by light microscope and Atom Force Microscope AFM. Oxidation behavior of large grain samples with different orientations after BCP was studied by X-ray photoelectron spectroscopy XPS and compared to polycrystalline niobium. The thickness of oxide layer on LG niobium is smaller than on fine grain material. The thickness of the oxide layer also depends on crystal orientation. Electron beam welding of LG samples has shown that two crystals grow in one crystal together, if the crystallographic orientations are matched at the EB seam. Relationship between the crystallographic orientation of the main central crystal of LG cavities and RF-data are analyzed. It seems that the orientations (221) and (211) is more preferable for cavity performance

Poster TUP041 [2.490 MB]

TUP063

Quench Studies and Preheating Analysis of Seamless Hydroformed Cavities Processed at Jefferson Laboratories

575

A.D. Palczewski, G.V. Eremeev, R.L. Geng
JLAB, Newport News, Virginia, USA
I. Jelezov
RAS/INR, Moscow, Russia
W. Singer, X. Singer
DESY, Hamburg, Germany

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
One of the alternative manufacturing technologies for SRF cavities is hydroforming from seamless tubes. Although this technology has produced cavities with gradient and Q-values comparable to standard EBW/EP cavities, a few questions remain. One of these questions is whether the quench mechanism in hydroformed cavities is the same as in standard electron beam welded cavities. Towards this effort Jefferson Lab performed quench studies on 4 different seamless hydroformed cavities. These cavities include DESY’s – Z163 and Z164 nine-cell cavities, and Black Laboratories nine-cell and two-cell TESLA shaped cavities, hydroformed at DESY. Initial results from the cavities and quench localization were published in SRF2011*. In this report we will present post JLAB surface retreatment quench studies for each cavity. The data will include OST and T-mapping quench localization as well as quench location preheating analysis comparing them to the observations in standard electron beam welded cavities.
*W. Singer, A. Ermakov, G. Kreps, A. Matheisen, X. Singer, K. Twarowski, I. Zhelezov, P. Kneisel, R. Crooks, Proceedings of SRF2011, TUPO026 2011.

TUP110

An X-Ray Fluorescence Probe for Defect Detection in Superconducting 1.3 GHz Cavities

736

P. Michelato, M. Bertucci
INFN/LASA, Segrate (MI), Italy
A. Navitski, W. Singer, X. Singer
DESY, Hamburg, Germany
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
Y. Tamashevich
Uni HH, Hamburg, Germany

The aim of this project is to develop a system for defect detection by means of X-ray fluorescence (XRF) analysis. XRF is a high sensitivity spectroscopy technique allowing the detection of trace element content, such as the few microgram impurities, responsible for low cavity performances if embedded in the equatorial region during cavity manufacturing. The proposed setup is customized on 1.3 GHz TESLA-type niobium cavities: both the detector and the X-ray excitation source are miniaturized so to allow the probe to enter within the 70 mm iris diameter and aside of the HOM couplers. The detection-excitation geometry is focused on cavity cell equator surface located at about 10³ mm from the cavity axis, with an intrinsic spot-size of about 10 mm. The measuring head will be settled on a high angular resolution optical inspection system at DESY, exploiting the experience of OBACHT. Defect position is obtained by means of angular inner cavity surface scanning. A quantitative determination of defect content can also be carried out by means of fundamental parameters technique with a Niobium standard calibration.

Paper	Title	Page
MOP032	Statistic to Eddy-Current Scanning of Niobium Sheets for European XFEL	171
	A. Brinkmann, S. Arnold, A. Ermakov, J. Iversen, M. Lengkeit, A. Poerschmann, L. Schaefer, W. Singer, X. Singer DESY, Hamburg, Germany
	The fabrication experiences of superconducting cavities for FLASH have shown that eddy-current scanning of the Nb-sheets foreseen for half-cells reduces the cavity failures. New eddy current devices have been developed and build together with the industry for the production of 800 pieces 1.3 GHz superconducting niobium cavities for European XFEL. More than 15.000 Nb-sheets provided by three companies have been tested by eddy-current scanning. The sheets that demonstrated local deviations of the signal have been subsequently non-destructively examined by 3d-microscope and X-Ray element analysis. The surface defects (dents, holes, scratches) are the mainly detected flaws. In addition several types of foreign material inclusions observed. Statistic concerning eddy-current signal deviation and rejection rates for each supplier will be presented.

MOP043	ILC-HiGrade Cavities as a Tool of Quality Control for European XFEL	212
	A. Navitski, E. Elsen, B. Foster, J. Iversen, A. Matheisen, D. Reschke, W. Singer, X. Singer, L. Steder, M. Wenskat DESY, Hamburg, Germany R. Laasch, Y. Tamashevich University of Hamburg, Hamburg, Germany
	Funding: BMBF, Helmholtz Association, ILC-HiGrade, FP7 (CRISP), Alexander von Humboldt Stiftung/Foundation The EXFEL order for SRF cavities includes 24 cavities, which are part of the ILC-HiGrade program. Initially, these cavities serve as quality control (QC) sample extracted from the EXFEL cavities series production on a regular basis. The QC and quality assurance (QA) include all processing steps of the EXFEL cavities. To maximize the information from these so-called QC cavities, a surface mapping technique is applied in a second cold RF test. There the cavities delivered have experienced identical treatment of the inner surface with the exception of mounting of the Helium vessel. After the normal acceptance test at the cavity RF measurement facility, the cavities are removed from the production flow. Further quality assurance steps beginning with a detailed RF test with surface mapping followed by a high resolution optical inspection (OBACHT) are carried out to improve the understanding of defects in close collaboration with the standing experts engaged in the EXFEL production. Results of the first QC cavities tests as well as planned further R&D will be presented and discussed.

MOP050	Strategy and Experiences on Procurement of Material for European XFEL Cavities
	X. Singer, J. Iversen, W. Singer DESY, Hamburg, Germany F. Gaus, K-H. Marrek TÜV NORD Systems GmbH & Co. KG, Hamburg, Germany
	Analysis of the strategy for material procurement and quality management is done on base of the European XFEL experiences. In the preparation phase the requirements to material has been defined and the qualification of various companies as potential supplier for European XFEL executed. Estimation of the material for production of pressure bearing parts, creation of PMAs (particular material appraisal) acc. the European Pressure Equipment Directive and certification of the companies as producer of the material for pressure bearing parts has been done together with the notified body (TÜV NORD Systems). The procurement of material, QC, documentation, shipment and supervising the material workflow at cavity-producers has been carried out by DESY. Four companies produced ca. 25.000 semi-finished parts of high purity niobium and NbTi within of three years. Analysis of the main flaws and foreign material inclusions in niobium sheets is presented.
	Poster MOP050 [1.609 MB]

MOP053	R&D on Cavity Treatments at DESY Towards the ILC Performance Goal	240
	A. Navitski, E. Elsen, B. Foster, D. Reschke, J. Schaffran, W. Singer, X. Singer DESY, Hamburg, Germany R. Laasch, Y. Tamashevich University of Hamburg, Hamburg, Germany
	Funding: BMBF, Helmholtz Association, ILC-HiGrade, FP7 (CRISP), Alexander von Humboldt Stiftung/Foundation The actual R&D program at DESY is derived from the global effort for the International Linear Collider (ILC) and is well in phase with effort elsewhere. The program aims at a solid understanding and control of the industrial mass-production process of the superconducting radio-frequency accelerating cavities, which are manufactured for the European X-ray Free Electron Laser (EXFEL) at DESY. The goal is to identify the gradient limiting factors and further refine the cavity treatment technique to provide gradients above 35 MV/m at >90% production yield. Techniques such as 2nd sound quench detection, OBACHT optical inspections, defect metrology using silicon replica as well as Centrifugal Barrel Polishing (CBP) and Local Grinding repair are foreseen as tools. Actual status, details, and first achievements of the program will be reported.

TUP024	Unloaded Quality Factor Qo of Prototype European XFEL Cavities, Large Grain and Hydroformed Cavities
	A. Ermakov, W. Singer, X. Singer DESY, Hamburg, Germany
	A statistical analysis of the unloaded quality factor Q0 of TESLA shape cavities at low accelerating field (up to 5 MV/m) and medium accelerating field (5-20 MV/m) was done on base of available RF data for test series: single-cell and 9-cell large grain cavities, single cell and multi-cell hydroformed at DESY cavities, fine grain cavities-prototypes for European XFEL. On the one hand the purpose of statistical analysis is done to find the relationship between the parameters describing the behavior between unloaded quality factor Q0 (as function of the accelerated field Eacc) and main treatment procedures (Buffered Chemical Polishing BCP, Electropolishing EP, 120°C baking). On the other hand the relationship between Q0 and different types of cavities (cavities with reduced number of grain boundaries, cavities without equator welding seam, cavities of standard fine grain material) was evaluated. The non - linearity of the surface resistance in low and medium field regions analyzed for these types of cavities and compared with the available theoretical models.

TUP041	Large Grain DESY Cavities and Crystallographic Orientation of the Niobium Discs
	X. Singer, W. Singer DESY, Hamburg, Germany K. Kazimierz University of Mining and Metallurgy, Kraków, Poland
	Eleven 9-cell Large Grain LG cavities have been produced and successfully RF tested at DESY. Analysis of the LG niobium discs for these cavities from the crystallographic orientation point of view will be presented. Surface behavior and roughness of the LG samples of different crystallographic orientation after buffered chemical polishing BCP have been studied by light microscope and Atom Force Microscope AFM. Oxidation behavior of large grain samples with different orientations after BCP was studied by X-ray photoelectron spectroscopy XPS and compared to polycrystalline niobium. The thickness of oxide layer on LG niobium is smaller than on fine grain material. The thickness of the oxide layer also depends on crystal orientation. Electron beam welding of LG samples has shown that two crystals grow in one crystal together, if the crystallographic orientations are matched at the EB seam. Relationship between the crystallographic orientation of the main central crystal of LG cavities and RF-data are analyzed. It seems that the orientations (221) and (211) is more preferable for cavity performance
	Poster TUP041 [2.490 MB]

TUP063	Quench Studies and Preheating Analysis of Seamless Hydroformed Cavities Processed at Jefferson Laboratories	575
	A.D. Palczewski, G.V. Eremeev, R.L. Geng JLAB, Newport News, Virginia, USA I. Jelezov RAS/INR, Moscow, Russia W. Singer, X. Singer DESY, Hamburg, Germany
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. One of the alternative manufacturing technologies for SRF cavities is hydroforming from seamless tubes. Although this technology has produced cavities with gradient and Q-values comparable to standard EBW/EP cavities, a few questions remain. One of these questions is whether the quench mechanism in hydroformed cavities is the same as in standard electron beam welded cavities. Towards this effort Jefferson Lab performed quench studies on 4 different seamless hydroformed cavities. These cavities include DESY’s – Z163 and Z164 nine-cell cavities, and Black Laboratories nine-cell and two-cell TESLA shaped cavities, hydroformed at DESY. Initial results from the cavities and quench localization were published in SRF2011. In this report we will present post JLAB surface retreatment quench studies for each cavity. The data will include OST and T-mapping quench localization as well as quench location preheating analysis comparing them to the observations in standard electron beam welded cavities. W. Singer, A. Ermakov, G. Kreps, A. Matheisen, X. Singer, K. Twarowski, I. Zhelezov, P. Kneisel, R. Crooks, Proceedings of SRF2011, TUPO026 2011.

TUP110	An X-Ray Fluorescence Probe for Defect Detection in Superconducting 1.3 GHz Cavities	736
	P. Michelato, M. Bertucci INFN/LASA, Segrate (MI), Italy A. Navitski, W. Singer, X. Singer DESY, Hamburg, Germany C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy Y. Tamashevich Uni HH, Hamburg, Germany
	The aim of this project is to develop a system for defect detection by means of X-ray fluorescence (XRF) analysis. XRF is a high sensitivity spectroscopy technique allowing the detection of trace element content, such as the few microgram impurities, responsible for low cavity performances if embedded in the equatorial region during cavity manufacturing. The proposed setup is customized on 1.3 GHz TESLA-type niobium cavities: both the detector and the X-ray excitation source are miniaturized so to allow the probe to enter within the 70 mm iris diameter and aside of the HOM couplers. The detection-excitation geometry is focused on cavity cell equator surface located at about 10³ mm from the cavity axis, with an intrinsic spot-size of about 10 mm. The measuring head will be settled on a high angular resolution optical inspection system at DESY, exploiting the experience of OBACHT. Defect position is obtained by means of angular inner cavity surface scanning. A quantitative determination of defect content can also be carried out by means of fundamental parameters technique with a Niobium standard calibration.