SRF2015 - List of Keywords (laser)

Paper	Title	Other Keywords	Page
MOPB072	Characterization of Surface Defects on EXFEL Series and ILC-Higrade Cavities	cavity, niobium, SRF, radiation	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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MOPB073	Surface Analyses and Optimization of Centrifugal Barrel Polishing of Nb Cavities	cavity, niobium, SRF, embedded	286
	A. Navitski, E. Elsen, B. Foster DESY, Hamburg, Germany B. Foster, A.L. Prudnikava, Y. Tamashevich University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Funding: BMBF project 05H12GU9, Alexander von Humboldt Foundation, and CRISP (No. 283745). Centrifugal barrel polishing (CBP) is an acid-free surface-polishing technique based on abrasive media. It considerably reduces the usage of chemicals in the preparation of Nb cavities, typically leaving only a final light electropolishing (EP) and achieves considerably smaller roughness than in chemical treatments alone. CBP addresses in particular the removal of pits, welding spatters, deep scratches, and foreign material inclusions that occasionally occur in the production process. A mirror-smooth surface without chemical contamination is also an important enabling step for thin films. Recent results indicate, however, the need of further optimizations, mainly to reduce the surface damaged layer as well as the pollution by the polishing media. A dedicated study of the CBP process using a “coupon” cavity facilitates better polishing characterisation and optimisation by direct measurements of the roughness, removal rate, and removal profile as well as the amount of contamination left behind and determination of a best combination of the CBP and chemical polishing. Results of the coupon-studies and perspectives of the optimizations will be presented and discussed.
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MOPB113	Study of the Evolution of Artificial Defects on the Surface of Niobium During Electrochemical and Chemical Polishing	SRF, controls, cavity, operation	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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THPB046	Design and Development of Superconducting Spoke Cavity for Compact Photon Source	cavity, photon, simulation, scattering	1196
	M. Sawamura Japan Atomic Energy Agency (JAEA), Gamma-ray Non-Destructive Assay Research Group, Tokai-mura, Ibaraki-ken, Japan E. Cenni CEA/IRFU, Gif-sur-Yvette, France R. Hajima JAEA, Ibaraki-ken, Japan H. Hokonohara, Y. Iwashita, H. Tongu Kyoto ICR, Uji, Kyoto, Japan T. Kubo, T. Saeki KEK, Ibaraki, Japan
	Funding: This study is supported by Photon and Quantum Basic Research Coordinated Development Program of MEXT, Japan. The spoke cavity is expected to have advantages for compact ERL accelerator for X-ray source based on laser Compton scattering. We have been developing the spoke cavity under a research program of MEXT, Japan to establish the fabrication process. Since our designed shape of the spoke cavity is complicated due to increase the RF properties, we have been designing the mold including the process of press work and the support parts for vacuum tolerance with the mechanical simulation. In this paper we present status of the spoke cavity fabrication.
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THPB058	Commissioning of the 112 MHz SRF Gun	gun, cathode, SRF, electron	1240
	S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, T. Hayes, V. Litvinenko, K. Mernick, G. Narayan, P. Orfin, I. Pinayev, T. Rao, F. Severino, J. Skaritka, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, Q. Wu, B. P. Xiao, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, T. Xin Stony Brook University, Stony Brook, USA
	Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE. A 112 MHz superconducting RF photoemission gun was designed, fabricated and installed in RHIC for the Coherent electron Cooling Proof-of-Principle (CeC PoP) experiment at BNL. The gun was commissioned first without beam. This was followed by generating the first photoemission beam from a multi-alkali cathode. The paper presents the commissioning results.
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THPB083	Energetic Copper Coating on Stainless Steel Power Couplers for SRF Application	SRF, cathode, plasma, ion	1330
	I. Irfan, S.F. Chapman, M. Krishnan, K.M. Velas AASC, San Leandro, California, USA W. Kaabi LAL, Orsay, France
	Funding: This research is supported by the US DOE via and SBIR grant: DE-SC0009581 Delivering RF power from the outside (at room temperature) to the inside of SRF cavities (at ~4 K temperature), requires a power coupler to be thermally isolating, while still electrically conducting on the inside. Stainless steel parts that are coated on the insides with a few skin depths of copper can meet these conflicting requirements. The challenge has been the adhesion strength of copper coating on stainless steel coupler parts when using electroplating methods. These methods also require a nickel flash layer that is magnetic and can therefore pose problems. Alameda Applied Sciences Corporation (AASC) uses Coaxial Energetic Deposition (CED) from a cathodic arc plasma to grow copper films directly on stainless steel coupler parts with no Ni layer and no electrochemistry. The vacuum arc plasma consists of ~100 eV Cu ions that penetrate a few monolayers into the stainless steel substrate to promote growth of highly adhesive films with crystalline structure. Adhesion strength and coating quality of copper coatings on complex stainless steel tubes, bellows, mock coupler parts and an actual Tesla Test Facility (TTF) type coupler part, are discussed. * Adhesion and Cu quality testing were done for us by the Fermilab Technical Division, Superconducting RF Development Department
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Paper

Title

Other Keywords

Page

MOPB072

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

cavity, niobium, SRF, radiation

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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MOPB073

Surface Analyses and Optimization of Centrifugal Barrel Polishing of Nb Cavities

cavity, niobium, SRF, embedded

286

A. Navitski, E. Elsen, B. Foster
DESY, Hamburg, Germany
B. Foster, A.L. Prudnikava, Y. Tamashevich
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Funding: BMBF project 05H12GU9, Alexander von Humboldt Foundation, and CRISP (No. 283745).
Centrifugal barrel polishing (CBP) is an acid-free surface-polishing technique based on abrasive media. It considerably reduces the usage of chemicals in the preparation of Nb cavities, typically leaving only a final light electropolishing (EP) and achieves considerably smaller roughness than in chemical treatments alone. CBP addresses in particular the removal of pits, welding spatters, deep scratches, and foreign material inclusions that occasionally occur in the production process. A mirror-smooth surface without chemical contamination is also an important enabling step for thin films. Recent results indicate, however, the need of further optimizations, mainly to reduce the surface damaged layer as well as the pollution by the polishing media. A dedicated study of the CBP process using a “coupon” cavity facilitates better polishing characterisation and optimisation by direct measurements of the roughness, removal rate, and removal profile as well as the amount of contamination left behind and determination of a best combination of the CBP and chemical polishing. Results of the coupon-studies and perspectives of the optimizations will be presented and discussed.

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MOPB113

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

SRF, controls, cavity, operation

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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THPB046

Design and Development of Superconducting Spoke Cavity for Compact Photon Source

cavity, photon, simulation, scattering

1196

M. Sawamura
Japan Atomic Energy Agency (JAEA), Gamma-ray Non-Destructive Assay Research Group, Tokai-mura, Ibaraki-ken, Japan
E. Cenni
CEA/IRFU, Gif-sur-Yvette, France
R. Hajima
JAEA, Ibaraki-ken, Japan
H. Hokonohara, Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
T. Kubo, T. Saeki
KEK, Ibaraki, Japan

Funding: This study is supported by Photon and Quantum Basic Research Coordinated Development Program of MEXT, Japan.
The spoke cavity is expected to have advantages for compact ERL accelerator for X-ray source based on laser Compton scattering. We have been developing the spoke cavity under a research program of MEXT, Japan to establish the fabrication process. Since our designed shape of the spoke cavity is complicated due to increase the RF properties, we have been designing the mold including the process of press work and the support parts for vacuum tolerance with the mechanical simulation. In this paper we present status of the spoke cavity fabrication.

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THPB058

Commissioning of the 112 MHz SRF Gun

gun, cathode, SRF, electron

1240

S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, T. Hayes, V. Litvinenko, K. Mernick, G. Narayan, P. Orfin, I. Pinayev, T. Rao, F. Severino, J. Skaritka, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, Q. Wu, B. P. Xiao, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, T. Xin
Stony Brook University, Stony Brook, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
A 112 MHz superconducting RF photoemission gun was designed, fabricated and installed in RHIC for the Coherent electron Cooling Proof-of-Principle (CeC PoP) experiment at BNL. The gun was commissioned first without beam. This was followed by generating the first photoemission beam from a multi-alkali cathode. The paper presents the commissioning results.

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THPB083

Energetic Copper Coating on Stainless Steel Power Couplers for SRF Application

SRF, cathode, plasma, ion

1330

I. Irfan, S.F. Chapman, M. Krishnan, K.M. Velas
AASC, San Leandro, California, USA
W. Kaabi
LAL, Orsay, France

Funding: This research is supported by the US DOE via and SBIR grant: DE-SC0009581
Delivering RF power from the outside (at room temperature) to the inside of SRF cavities (at ~4 K temperature), requires a power coupler to be thermally isolating, while still electrically conducting on the inside. Stainless steel parts that are coated on the insides with a few skin depths of copper can meet these conflicting requirements. The challenge has been the adhesion strength of copper coating on stainless steel coupler parts when using electroplating methods. These methods also require a nickel flash layer that is magnetic and can therefore pose problems. Alameda Applied Sciences Corporation (AASC) uses Coaxial Energetic Deposition (CED) from a cathodic arc plasma to grow copper films directly on stainless steel coupler parts with no Ni layer and no electrochemistry. The vacuum arc plasma consists of ~100 eV Cu ions that penetrate a few monolayers into the stainless steel substrate to promote growth of highly adhesive films with crystalline structure. Adhesion strength and coating quality of copper coatings on complex stainless steel tubes, bellows, mock coupler parts and an actual Tesla Test Facility (TTF) type coupler part, are discussed.
* Adhesion and Cu quality testing were done for us by the Fermilab Technical Division, Superconducting RF Development Department

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