SRF2011 - List of Authors (Grill, R.)

Paper

Title

Page

Material for Fabrication of DESY Large Grain/Single Crystal Cavities

854

X. Singer, J. Iversen, W. Singer, K. Twarowski
DESY, Hamburg, Germany
H.G. Brokmeier
Technische Universität Clausthal, Institut für Nichtmetallische Werkstoffe, Clausthal-Zellerfeld, Germany
R. Grill
Plansee Metall GmbH, Reutte, Austria
F. Schölz, B. Spaniol
W.C. Heraeus GmbH, Materials Technology Dept., Hanau, Germany

Material for large grain LG and single crystal SC cavities of TESLA shape has been developed in collaboration with industry. One of the aspects of LG material was electron beam melting of the ingots with required structure. The second was slicing of the discs cost effectively with tight thickness tolerances, high surface quality and high purity. Surface and structural properties of SC on the LG discs are investigated. Measurements of the crystal orientation on the LG discs of three companies have been done by complete penetration using synchrotron radiation. Two LG material features have been stressed in cavity production: the influence of the LG crystal orientation on the anisotropic behavior during deep drawing and the impact of pronounced steps at grain boundaries on cavity behavior. 11 LG 9-cell cavities of XFEL-like shape are fabricated. The procedure of increasing the crystal size by rolling of LG discs and cut out of SC discs, followed by subsequent forming and welding without destroying of the SC structure, was developed. A method of fabrication of single crystal cavities was proposed. Several SC cavities with different crystal orientations were produced.

Poster THPO053 [2.201 MB]

THPO059

Correlation of Microstructure, Chemical Composition and RRR-Value in High Purity Niobium (Nb-RRR))

863

R. Grill, W. Simader
Plansee Metall GmbH, Reutte, Austria
M. Heilmaier, D. Janda
TU Darmstadt, Darmstadt, Germany
W. Singer, X. Singer
DESY, Hamburg, Germany

For manufacturing of Nb-RRR sheet material a thorough understanding of material properties and niobium metallurgy is necessary to meet the required regarding material properties as specified for the XFEL project. Especially for the RRR value it is known, that residual stresses, and increased levels of vacancy and impurity concentrations, and dislocation densities after the final heat treatment can cause a severe degradation of the RRR value. Also, a comprehensive understanding of the influence of further microstructural properties (e.g. different textures due to rolling operations and annealing, dislocation substructures, etc.) on the RRR-value is lacking. For specimens having RRR-values in the range of 360 to 430, the crystallographic texture has been investigated and correlated with the measured RRR values. Furthermore, the possible influence of different impurity levels on the RRR value was calculated, compared with the measured values and discussed with regard to the current material specification for the XFEL project.

Paper	Title	Page
THPO053	Material for Fabrication of DESY Large Grain/Single Crystal Cavities	854
	X. Singer, J. Iversen, W. Singer, K. Twarowski DESY, Hamburg, Germany H.G. Brokmeier Technische Universität Clausthal, Institut für Nichtmetallische Werkstoffe, Clausthal-Zellerfeld, Germany R. Grill Plansee Metall GmbH, Reutte, Austria F. Schölz, B. Spaniol W.C. Heraeus GmbH, Materials Technology Dept., Hanau, Germany
	Material for large grain LG and single crystal SC cavities of TESLA shape has been developed in collaboration with industry. One of the aspects of LG material was electron beam melting of the ingots with required structure. The second was slicing of the discs cost effectively with tight thickness tolerances, high surface quality and high purity. Surface and structural properties of SC on the LG discs are investigated. Measurements of the crystal orientation on the LG discs of three companies have been done by complete penetration using synchrotron radiation. Two LG material features have been stressed in cavity production: the influence of the LG crystal orientation on the anisotropic behavior during deep drawing and the impact of pronounced steps at grain boundaries on cavity behavior. 11 LG 9-cell cavities of XFEL-like shape are fabricated. The procedure of increasing the crystal size by rolling of LG discs and cut out of SC discs, followed by subsequent forming and welding without destroying of the SC structure, was developed. A method of fabrication of single crystal cavities was proposed. Several SC cavities with different crystal orientations were produced.
	Poster THPO053 [2.201 MB]

THPO059	Correlation of Microstructure, Chemical Composition and RRR-Value in High Purity Niobium (Nb-RRR))	863
	R. Grill, W. Simader Plansee Metall GmbH, Reutte, Austria M. Heilmaier, D. Janda TU Darmstadt, Darmstadt, Germany W. Singer, X. Singer DESY, Hamburg, Germany
	For manufacturing of Nb-RRR sheet material a thorough understanding of material properties and niobium metallurgy is necessary to meet the required regarding material properties as specified for the XFEL project. Especially for the RRR value it is known, that residual stresses, and increased levels of vacancy and impurity concentrations, and dislocation densities after the final heat treatment can cause a severe degradation of the RRR value. Also, a comprehensive understanding of the influence of further microstructural properties (e.g. different textures due to rolling operations and annealing, dislocation substructures, etc.) on the RRR-value is lacking. For specimens having RRR-values in the range of 360 to 430, the crystallographic texture has been investigated and correlated with the measured RRR values. Furthermore, the possible influence of different impurity levels on the RRR value was calculated, compared with the measured values and discussed with regard to the current material specification for the XFEL project.