SRF2015 - List of Authors (Ciovati, G.)

Paper	Title	Page
MOBA07	Lessons Learned From Nitrogen Doping at JLab - Exploration of Surface Resistance and Quench Field Trade-Offs With Varied Interstitial Atom Diffusion of Niobium Cavity Surfaces
	A.D. Palczewski, G. Ciovati, P. Dhakal, R.L. Geng, C.E. Reece, H. Tian JLab, Newport News, Virginia, USA
	Funding: This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 and by the LCLS-II Project under DE-AC02-76SF00515. Interstitial diffusion of atomic species into the surface of niobium has been found to yield significantly reduced srf surface resistance and lowered quench fields. This talk summarizes systematic efforts to explore the trade-offs of these phenomena with a goal of learning how to maximize Q0 in the 30 MV/m regime. The talk also summarizes N-doped cavity progress at JLab for LCLS-II.
	Slides MOBA07 [3.052 MB]
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MOPB001	RF Performance of Ingot Niobium Cavities of Medium-Low Purity	61
	G. Ciovati, P. Dhakal, P. Kneisel, G.R. Myneni, J.K. Spradlin JLab, Newport News, Virginia, USA
	Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q0-values, because of the well-known dependence of the BCS-surface resistance on mean free path. In this contribution we present the results from cryogenic RF tests of 1.3-1.5 GHz single-cell cavities made of ingot Nb of medium (RRR=100-150) and low (RRR=60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with Q0-values above 1.5·10¹⁰ at 2 K. The performance of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching.
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MOPB030	Measurements of Thermal Impedance on Superconducting Radiofrequency Cavities	154
	P. Dhakal, G. Ciovati, G.R. Myneni JLab, Newport News, Virginia, USA
	Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The thermal impedance of niobium plays an important role in the stability of the superconducting radio frequency cavities used in particle accelerators. During the operation of SRF cavities, the RF power dissipated on the inner surface of the cavities and the heat transport to the helium bath depend on the thermal conductivity of niobium and the Kapitza conductance of the interface between the niobium and superfluid helium. Here, we present the results of measurements done on samples as well as on SRF cavities made of both ingot and fine-grain Nb to explore the effect of the surface preparation and crystal structure on the thermal impedance.
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THPB026	Update on SRF Cavity Design, Production and Testing for BERLinPro	1127
	A. Neumann, W. Anders, A. Burrill, A. Frahm, H.-W. Glock, J. Knobloch, O. Kugeler HZB, Berlin, Germany K. Brackebusch, T. Galek, J. Heller, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany G. Ciovati, W.A. Clemens, C. Dreyfuss, D. Forehand, T. Harris, P. Kneisel, R.B. Overton, L. Turlington JLab, Newport News, Virginia, USA E.N. Zaplatin FZJ, Jülich, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association. The BERLinPro Energy Recovery Linac (ERL) is currently being built at Helmholtz-Zentrum Berlin in order to study the accelerator physics of operating a high current, 100 mA, 50 MeV low emittance ERL utilizing all SRF cavity technology. For this machine three different types of SRF cavities are being developed. For the injector section, consisting of an SRF photoinjector and a three two cell booster cavity module, fabrication is completed. The cavities were designed at HZB and manufactured, processed and vertically tested at Jefferson Laboratory. In this paper we will review the design and production process of the two structures and show the latest horizontal acceptance tests at HZB prior to installation into the newly designed cryo-module. For the Linac cavity the latest cavity and module design studies are being shown.
	Poster THPB026 [1.535 MB]
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THPB042	Advance Additive Manufacturing Method for SRF Cavities of Various Geometries	1181
	P. Frigola, R.B. Agustsson, L. Faillace, A.Y. Murokh RadiaBeam, Marina del Rey, California, USA G. Ciovati, W.A. Clemens, P. Dhakal, F. Marhauser, R.A. Rimmer, J.K. Spradlin, R.S. Williams JLab, Newport News, Virginia, USA J. Mireles, P.A. Morton, R.B. Wicker University of Texas El Paso, W.M. Keck Center for 3D Innovation, El Paso, Texas, USA
	An alternative fabrication method for superconducting radio frequency (SRF) cavities is presented. The novel fabrication method, based on 3D printing (or additive manufacturing, AM) technology capable of producing net-shape functional metallic parts of virtually any geometry, promises to greatly expand possibilities for advance cavity and end-group component designs. A description of the AM method and conceptual cavity designs are presented along with material analysis and RF measurement results of additively manufactured niobium samples.
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THPB055	RF Performance Results of the 2nd ELBE SRF Gun	1227
	A. Arnold, M. Freitag, P.N. Lu, P. Murcek, J. Teichert, H. Vennekate, R. Xiang HZDR, Dresden, Germany G. Ciovati, P. Kneisel, M. Stirbet, L. Turlington JLab, Newport News, Virginia, USA
	As in 2007 the first 3.5 cell superconducting radio frequency (SRF) gun was taken into operation at Helmholtz-Zentrum Dresden-Rossendorf, it turned out that the specified performance to realize an electron energy of 9.4 MeV has not been achieved. Instead, the resonator of the gun was limited by field emission to about one third of this value and the measured beam parameters remained significantly below its expectations. However, to demonstrate the full potential of this electron source for the ELBE linear accelerator, a second and slightly modified SRF gun was developed and built in collaboration with Thomas Jefferson National Accelerator Facility. We will report on commissioning of this new SRF gun and present a full set of RF performance results. Additionally, investigations are shown that try to explain a particle contamination that happened recently during our first cathode transfer.
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Paper

Title

Page

MOBA07

Lessons Learned From Nitrogen Doping at JLab - Exploration of Surface Resistance and Quench Field Trade-Offs With Varied Interstitial Atom Diffusion of Niobium Cavity Surfaces

A.D. Palczewski, G. Ciovati, P. Dhakal, R.L. Geng, C.E. Reece, H. Tian
JLab, Newport News, Virginia, USA

Funding: This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 and by the LCLS-II Project under DE-AC02-76SF00515.
Interstitial diffusion of atomic species into the surface of niobium has been found to yield significantly reduced srf surface resistance and lowered quench fields. This talk summarizes systematic efforts to explore the trade-offs of these phenomena with a goal of learning how to maximize Q0 in the 30 MV/m regime. The talk also summarizes N-doped cavity progress at JLab for LCLS-II.

Slides MOBA07 [3.052 MB]

Export •

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MOPB001

RF Performance of Ingot Niobium Cavities of Medium-Low Purity

61

G. Ciovati, P. Dhakal, P. Kneisel, G.R. Myneni, J.K. Spradlin
JLab, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q0-values, because of the well-known dependence of the BCS-surface resistance on mean free path. In this contribution we present the results from cryogenic RF tests of 1.3-1.5 GHz single-cell cavities made of ingot Nb of medium (RRR=100-150) and low (RRR=60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with Q0-values above 1.5·10¹⁰ at 2 K. The performance of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching.

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

MOPB030

Measurements of Thermal Impedance on Superconducting Radiofrequency Cavities

154

P. Dhakal, G. Ciovati, G.R. Myneni
JLab, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The thermal impedance of niobium plays an important role in the stability of the superconducting radio frequency cavities used in particle accelerators. During the operation of SRF cavities, the RF power dissipated on the inner surface of the cavities and the heat transport to the helium bath depend on the thermal conductivity of niobium and the Kapitza conductance of the interface between the niobium and superfluid helium. Here, we present the results of measurements done on samples as well as on SRF cavities made of both ingot and fine-grain Nb to explore the effect of the surface preparation and crystal structure on the thermal impedance.

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

THPB026

Update on SRF Cavity Design, Production and Testing for BERLinPro

1127

A. Neumann, W. Anders, A. Burrill, A. Frahm, H.-W. Glock, J. Knobloch, O. Kugeler
HZB, Berlin, Germany
K. Brackebusch, T. Galek, J. Heller, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
G. Ciovati, W.A. Clemens, C. Dreyfuss, D. Forehand, T. Harris, P. Kneisel, R.B. Overton, L. Turlington
JLab, Newport News, Virginia, USA
E.N. Zaplatin
FZJ, Jülich, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association.
The BERLinPro Energy Recovery Linac (ERL) is currently being built at Helmholtz-Zentrum Berlin in order to study the accelerator physics of operating a high current, 100 mA, 50 MeV low emittance ERL utilizing all SRF cavity technology. For this machine three different types of SRF cavities are being developed. For the injector section, consisting of an SRF photoinjector and a three two cell booster cavity module, fabrication is completed. The cavities were designed at HZB and manufactured, processed and vertically tested at Jefferson Laboratory. In this paper we will review the design and production process of the two structures and show the latest horizontal acceptance tests at HZB prior to installation into the newly designed cryo-module. For the Linac cavity the latest cavity and module design studies are being shown.

Poster THPB026 [1.535 MB]

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THPB042

Advance Additive Manufacturing Method for SRF Cavities of Various Geometries

1181

P. Frigola, R.B. Agustsson, L. Faillace, A.Y. Murokh
RadiaBeam, Marina del Rey, California, USA
G. Ciovati, W.A. Clemens, P. Dhakal, F. Marhauser, R.A. Rimmer, J.K. Spradlin, R.S. Williams
JLab, Newport News, Virginia, USA
J. Mireles, P.A. Morton, R.B. Wicker
University of Texas El Paso, W.M. Keck Center for 3D Innovation, El Paso, Texas, USA

An alternative fabrication method for superconducting radio frequency (SRF) cavities is presented. The novel fabrication method, based on 3D printing (or additive manufacturing, AM) technology capable of producing net-shape functional metallic parts of virtually any geometry, promises to greatly expand possibilities for advance cavity and end-group component designs. A description of the AM method and conceptual cavity designs are presented along with material analysis and RF measurement results of additively manufactured niobium samples.

Export •

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

THPB055

RF Performance Results of the 2nd ELBE SRF Gun

1227

A. Arnold, M. Freitag, P.N. Lu, P. Murcek, J. Teichert, H. Vennekate, R. Xiang
HZDR, Dresden, Germany
G. Ciovati, P. Kneisel, M. Stirbet, L. Turlington
JLab, Newport News, Virginia, USA

As in 2007 the first 3.5 cell superconducting radio frequency (SRF) gun was taken into operation at Helmholtz-Zentrum Dresden-Rossendorf, it turned out that the specified performance to realize an electron energy of 9.4 MeV has not been achieved. Instead, the resonator of the gun was limited by field emission to about one third of this value and the measured beam parameters remained significantly below its expectations. However, to demonstrate the full potential of this electron source for the ELBE linear accelerator, a second and slightly modified SRF gun was developed and built in collaboration with Thomas Jefferson National Accelerator Facility. We will report on commissioning of this new SRF gun and present a full set of RF performance results. Additionally, investigations are shown that try to explain a particle contamination that happened recently during our first cathode transfer.

Export •

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