SRF2011 - List of Authors (Twarowski, K.)

Paper

Title

Page

Nine - Cell Tesla Shape Cavities Produced From Hydroformed Cells

431

W. Singer, A. Ermakov, G. Kreps, A. Matheisen, X. Singer, K. Twarowski
DESY, Hamburg, Germany
R. Crooks
Black Laboratories, L.L.C., Newport News, USA
P. Kneisel
JLAB, Newport News, Virginia, USA
I.N. Zhelezov
RAS/INR, Moscow, Russia

Production of two types of seamless niobium tubes for hydroforming of RF cavities has been developed. The first type of tubes, developed at DESY, have been spun from sheets and flow formed. The second type of tubing was developed by Black Laboratories in collaboration with the company ATI Wah Chang. These longer length tubes were extruded from a heavily deformed billet, processed for a fine-grained microstructure and flow formed. Several seamless three cell units have been produced by hydroforming at DESY. Some of the units have been treated by buffered chemical polishing and RF tested at JLab. The accelerating gradient Eacc of the units exceeded in most cases 30 MV/m. Three of the 3-cell units from the first type of tubing were combined to three 9-cell niobium cavities at the company E. Zanon. The 3-cell units from extruded tubing are welded together to the fourth 9-cell cavity at JLab. All cavities are in preparation for the RF tests at DESY and JLab. Up to now two of the cavities are electropolished and tested at DESY. The first cavity reached an accelerating gradient of Eacc of ~30 MV/m, the second one ~35 MV/m.

Poster TUPO026 [2.664 MB]

TUPO066

Analysis of Recent Results from Second Sound, Temperature Mapping and Optical Inspection of 1.3 GHz Cavities at DESY

558

F. Schlander, S. Aderhold, D. Reschke, K. Twarowski
DESY, Hamburg, Germany

DESY is preparing for the delivery of some 600 superconducting 9-cell cavities for the European XFEL. Analysing the history and recorded data of recently tested cavities gives important evidence for proper treatment, preparation and handling of cavities. The experience given by temperature mapping, the Second Sound technique and optical inspection will be compared and an overview of the results obtained so far will be given in this report.

Poster TUPO066 [1.160 MB]

TUPO046

Results on Large Grain Nine-Cell Cavities at DESY: Gradients up to 45 MV/m after Electropolishing

490

D. Reschke, S. Aderhold, A. Gössel, J. Iversen, S. Karstensen, D. Kostin, G. Kreps, A. Matheisen, W.-D. Möller, F. Schlander, W. Singer, X. Singer, N. Steinhau Kühl, A.A. Sulimov, K. Twarowski
DESY, Hamburg, Germany

Since 2009 a series of eight nine-cell cavities (AC151 – AC158) of TESLA shape fabricated of large grain (LG) niobium material is under preparation and test at DESY. In a first step all cavities were tested after a BCP treatment. In a second step additional electro polishing is applied to all cavities. In this paper the treatment will be discussed and present results will be reported

THPO035

Comparison of Field Emission at Different SRF Cavity Assembly States and Test Stands

795

D. Kostin, A. Gössel, V. Gubarev, W.-D. Möller, D. Reschke, K. Twarowski
DESY, Hamburg, Germany

SRF cavity Field Emission (FE) presents a major diagnostics instrument on the cavity performance, save the FE levels differ significantly from one cavity test setup to another, making the analysis difficult. A comparison study complimented with a direct calibration of FE in the cavities tested with different auxillaries and test stands (vertical / horizontal / module) is presented and discussed.

Poster THPO035 [0.312 MB]

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]

THPO055

Investigation of Samples Separated From Prototype Cavities of the European XFEL

855

X. Singer, S. Aderhold, A. Ermakov, D. Reschke, W. Singer, K. Twarowski
DESY, Hamburg, Germany
M. Hoss
W.C. Heraeus GmbH, Materials Technology Dept., Hanau, Germany

XFEL prototype cavities fabricated in industry and treated at DESY mainly meet the specification. Few cavities demonstrated low performance (13-20 MV/m) limited by thermal breakdown. The T-map analysis detected quench areas mainly close to the equator. Optical inspection by high resolution camera allowed tracking the several stages of preparation (as received, after the main electropolishing EP, after RF test) and in some cases makes possible monitoring the evolution of defects. In order to understand the nature of reduced performance and get more detailed information on the origin of defects, some samples have been extracted from four cavities and investigated by light microscope, 3D-microscope, SEM, EDX and Auger spectroscopy. Several surface flaws with sizes from a few μm to hundreds of μm have been detected. The defects can be grouped in four categories. The first category of defects indicates foreign elements (often with increased content of carbon). Deviation from smooth surface profile characterizes the second type of defects (holes, bumps). Damaged surface areas at high pressure water rinsing and etching pits belong to the third and fourth category of defects.

Poster THPO055 [3.802 MB]

Paper	Title	Page
TUPO026	Nine - Cell Tesla Shape Cavities Produced From Hydroformed Cells	431
	W. Singer, A. Ermakov, G. Kreps, A. Matheisen, X. Singer, K. Twarowski DESY, Hamburg, Germany R. Crooks Black Laboratories, L.L.C., Newport News, USA P. Kneisel JLAB, Newport News, Virginia, USA I.N. Zhelezov RAS/INR, Moscow, Russia
	Production of two types of seamless niobium tubes for hydroforming of RF cavities has been developed. The first type of tubes, developed at DESY, have been spun from sheets and flow formed. The second type of tubing was developed by Black Laboratories in collaboration with the company ATI Wah Chang. These longer length tubes were extruded from a heavily deformed billet, processed for a fine-grained microstructure and flow formed. Several seamless three cell units have been produced by hydroforming at DESY. Some of the units have been treated by buffered chemical polishing and RF tested at JLab. The accelerating gradient Eacc of the units exceeded in most cases 30 MV/m. Three of the 3-cell units from the first type of tubing were combined to three 9-cell niobium cavities at the company E. Zanon. The 3-cell units from extruded tubing are welded together to the fourth 9-cell cavity at JLab. All cavities are in preparation for the RF tests at DESY and JLab. Up to now two of the cavities are electropolished and tested at DESY. The first cavity reached an accelerating gradient of Eacc of ~30 MV/m, the second one ~35 MV/m.
	Poster TUPO026 [2.664 MB]

TUPO066	Analysis of Recent Results from Second Sound, Temperature Mapping and Optical Inspection of 1.3 GHz Cavities at DESY	558
	F. Schlander, S. Aderhold, D. Reschke, K. Twarowski DESY, Hamburg, Germany
	DESY is preparing for the delivery of some 600 superconducting 9-cell cavities for the European XFEL. Analysing the history and recorded data of recently tested cavities gives important evidence for proper treatment, preparation and handling of cavities. The experience given by temperature mapping, the Second Sound technique and optical inspection will be compared and an overview of the results obtained so far will be given in this report.
	Poster TUPO066 [1.160 MB]

TUPO046	Results on Large Grain Nine-Cell Cavities at DESY: Gradients up to 45 MV/m after Electropolishing	490
	D. Reschke, S. Aderhold, A. Gössel, J. Iversen, S. Karstensen, D. Kostin, G. Kreps, A. Matheisen, W.-D. Möller, F. Schlander, W. Singer, X. Singer, N. Steinhau Kühl, A.A. Sulimov, K. Twarowski DESY, Hamburg, Germany
	Since 2009 a series of eight nine-cell cavities (AC151 – AC158) of TESLA shape fabricated of large grain (LG) niobium material is under preparation and test at DESY. In a first step all cavities were tested after a BCP treatment. In a second step additional electro polishing is applied to all cavities. In this paper the treatment will be discussed and present results will be reported

THPO035	Comparison of Field Emission at Different SRF Cavity Assembly States and Test Stands	795
	D. Kostin, A. Gössel, V. Gubarev, W.-D. Möller, D. Reschke, K. Twarowski DESY, Hamburg, Germany
	SRF cavity Field Emission (FE) presents a major diagnostics instrument on the cavity performance, save the FE levels differ significantly from one cavity test setup to another, making the analysis difficult. A comparison study complimented with a direct calibration of FE in the cavities tested with different auxillaries and test stands (vertical / horizontal / module) is presented and discussed.
	Poster THPO035 [0.312 MB]

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]

THPO055	Investigation of Samples Separated From Prototype Cavities of the European XFEL	855
	X. Singer, S. Aderhold, A. Ermakov, D. Reschke, W. Singer, K. Twarowski DESY, Hamburg, Germany M. Hoss W.C. Heraeus GmbH, Materials Technology Dept., Hanau, Germany
	XFEL prototype cavities fabricated in industry and treated at DESY mainly meet the specification. Few cavities demonstrated low performance (13-20 MV/m) limited by thermal breakdown. The T-map analysis detected quench areas mainly close to the equator. Optical inspection by high resolution camera allowed tracking the several stages of preparation (as received, after the main electropolishing EP, after RF test) and in some cases makes possible monitoring the evolution of defects. In order to understand the nature of reduced performance and get more detailed information on the origin of defects, some samples have been extracted from four cavities and investigated by light microscope, 3D-microscope, SEM, EDX and Auger spectroscopy. Several surface flaws with sizes from a few μm to hundreds of μm have been detected. The defects can be grouped in four categories. The first category of defects indicates foreign elements (often with increased content of carbon). Deviation from smooth surface profile characterizes the second type of defects (holes, bumps). Damaged surface areas at high pressure water rinsing and etching pits belong to the third and fourth category of defects.
	Poster THPO055 [3.802 MB]