LINAC2012 - List of Authors (Knobloch, J.)

Paper

Title

Page

Impact of Trapped Flux and Systematic Flux Expulsion in Superconducting Niobium

77

J.M. Vogt, J. Knobloch, O. Kugeler
HZB, Berlin, Germany

The intrinsic quality factor Q₀ of superconducting cavities is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We already reported an additional impact of temperature gradients during the cool-down on the obtained Q₀. We believe cooling conditions can influence the level of flux trapping and hence the residual resistance. For further studies we have constructed a test stand using niobium rods to study flux trapping. Here we can precisely control the temperature and approach T_c in the superconducting state. Although the sample remains in the superconducting state a change in the amount of trapped flux is visible. The procedure can be applied repeatedly resulting in a significantly lowered level of trapped flux in the sample. Applying a similar procedure to a superconducting cavity could allow for reduction of the magnetic contribution to the surface resistance and result in a significant improvement of Q₀.

MOPB065

Impact of Trapped Magnetic Flux and Systematic Flux Expulsion in Superconducting Niobium

327

J.M. Vogt, J. Knobloch, O. Kugeler
HZB, Berlin, Germany

The intrinsic quality factor Q₀ of superconducting cavities is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We already reported an additional impact of temperature gradients during the cool-down on the obtained Q₀. We believe cooling conditions can influence the level of flux trapping and hence the residual resistance. For further studies we have constructed a test stand using niobium rods to study flux trapping. Here we can precisely control the temperature and approach T_c in the superconducting state. Although the sample remains in the superconducting state a change in the amount of trapped flux is visible. The procedure can be applied repeatedly resulting in a significantly lowered level of trapped flux in the sample. Applying a similar procedure to a superconducting cavity could allow for reduction of the magnetic contribution to the surface resistance and result in a significant improvement of Q₀.

MOPB067

Results and Performance Simulations of the Main Linac Design for BERLinPro

333

A. Neumann, W. Anders, J. Knobloch
HZB, Berlin, Germany
K. Brackebusch, T. Flisgen, T. Galek, K. Papke, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
B. Riemann, T. Weis
DELTA, Dortmund, Germany

Funding: this work is partly funded by BMBF contract no. 05K10PEA and 05K10HRC
The Berlin Energy Recovery Linac Project (BERLinPro) is designed to develop and demonstrate CW LINAC technology for 100-mA-class ERLs. High-current operation requires an effective damping of higher-order modes (HOMs) of the 1.3 GHz main-linac cavities. We have studied elliptical 7-cell cavities damped by on the whole five waveguides at both ends. Eigenmode computations for geometrical figures of merit show that the present design should allow successful CW linac operation at the maximum beam current of 100 mA/77 pC bunch charge. To verify the results, the external Q factors are compared to the results of S-Parameter simulations that are postprocessed by a pole-fitting technique. First results of scattering parameter measurement on a room-temperature aluminium model are discussed. An outlook presenting the possibilities of combined multi-cavity simulations is included.

THPLB12

Photoinjector SRF Cavity Development for BERLinPro

837

A. Neumann, W. Anders, T. Kamps, J. Knobloch
HZB, Berlin, Germany
E.N. Zaplatin
FZJ, Jülich, Germany

In 2010 HZB has received approval to build BERLinPro, an ERL project to demonstrate energy recovery at 100 mA beam current by pertaining a high quality beam. These goals place stringent requirements on the SRF cavity for the photoinjector which has to deliver a small emittance 100 mA beam with at least 1.5 MeV kinetic energy while limited by fundamental power coupler performance to about 200 kW forward power. In oder to achieve these goals the injector cavity is being developed in a three stage approach. The current design studies focus on implementing a normal conducting cathode insert into a newly developed superconducting photoinjector cavity. In this paper the fundamental RF design calculations concerning cell shape for optimized beam dynamics as well as SRF performance will be presented. Further studies concentrate on the HZDR based choke cell design to implement the high quantum efficiency normal conducting cathode with the SRF cavity.

Slides THPLB12 [1.431 MB]

THPB066

Photoinjector SRF Cavity Development for BERLinPro

993

A. Neumann, W. Anders, T. Kamps, J. Knobloch
HZB, Berlin, Germany
E.N. Zaplatin
FZJ, Jülich, Germany

In 2010 HZB has received approval to build BERLinPro, an ERL project to demonstrate energy recovery at 100 mA beam current by pertaining a high quality beam. These goals place stringent requirements on the SRF cavity for the photoinjector which has to deliver a small emittance 100 mA beam with at least 1.5 MeV kinetic energy while limited by fundamental power coupler performance to about 200 kW forward power. In oder to achieve these goals the injector cavity is being developed in a three stage approach. The current design studies focus on implementing a normal conducting cathode insert into a newly developed superconducting photoinjector cavity. In this paper the fundamental RF design calculations concerning cell shape for optimized beam dynamics as well as SRF performance will be presented. Further studies concentrate on the HZDR based choke cell design to implement the high quantum efficiency normal conducting cathode with the SRF cavity.

Paper	Title	Page
SUPB029	Impact of Trapped Flux and Systematic Flux Expulsion in Superconducting Niobium	77
	J.M. Vogt, J. Knobloch, O. Kugeler HZB, Berlin, Germany
	The intrinsic quality factor Q₀ of superconducting cavities is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We already reported an additional impact of temperature gradients during the cool-down on the obtained Q₀. We believe cooling conditions can influence the level of flux trapping and hence the residual resistance. For further studies we have constructed a test stand using niobium rods to study flux trapping. Here we can precisely control the temperature and approach T_c in the superconducting state. Although the sample remains in the superconducting state a change in the amount of trapped flux is visible. The procedure can be applied repeatedly resulting in a significantly lowered level of trapped flux in the sample. Applying a similar procedure to a superconducting cavity could allow for reduction of the magnetic contribution to the surface resistance and result in a significant improvement of Q₀.

MOPB065	Impact of Trapped Magnetic Flux and Systematic Flux Expulsion in Superconducting Niobium	327
	J.M. Vogt, J. Knobloch, O. Kugeler HZB, Berlin, Germany
	The intrinsic quality factor Q₀ of superconducting cavities is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We already reported an additional impact of temperature gradients during the cool-down on the obtained Q₀. We believe cooling conditions can influence the level of flux trapping and hence the residual resistance. For further studies we have constructed a test stand using niobium rods to study flux trapping. Here we can precisely control the temperature and approach T_c in the superconducting state. Although the sample remains in the superconducting state a change in the amount of trapped flux is visible. The procedure can be applied repeatedly resulting in a significantly lowered level of trapped flux in the sample. Applying a similar procedure to a superconducting cavity could allow for reduction of the magnetic contribution to the surface resistance and result in a significant improvement of Q₀.

MOPB067	Results and Performance Simulations of the Main Linac Design for BERLinPro	333
	A. Neumann, W. Anders, J. Knobloch HZB, Berlin, Germany K. Brackebusch, T. Flisgen, T. Galek, K. Papke, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany B. Riemann, T. Weis DELTA, Dortmund, Germany
	Funding: this work is partly funded by BMBF contract no. 05K10PEA and 05K10HRC The Berlin Energy Recovery Linac Project (BERLinPro) is designed to develop and demonstrate CW LINAC technology for 100-mA-class ERLs. High-current operation requires an effective damping of higher-order modes (HOMs) of the 1.3 GHz main-linac cavities. We have studied elliptical 7-cell cavities damped by on the whole five waveguides at both ends. Eigenmode computations for geometrical figures of merit show that the present design should allow successful CW linac operation at the maximum beam current of 100 mA/77 pC bunch charge. To verify the results, the external Q factors are compared to the results of S-Parameter simulations that are postprocessed by a pole-fitting technique. First results of scattering parameter measurement on a room-temperature aluminium model are discussed. An outlook presenting the possibilities of combined multi-cavity simulations is included.

THPLB12	Photoinjector SRF Cavity Development for BERLinPro	837
	A. Neumann, W. Anders, T. Kamps, J. Knobloch HZB, Berlin, Germany E.N. Zaplatin FZJ, Jülich, Germany
	In 2010 HZB has received approval to build BERLinPro, an ERL project to demonstrate energy recovery at 100 mA beam current by pertaining a high quality beam. These goals place stringent requirements on the SRF cavity for the photoinjector which has to deliver a small emittance 100 mA beam with at least 1.5 MeV kinetic energy while limited by fundamental power coupler performance to about 200 kW forward power. In oder to achieve these goals the injector cavity is being developed in a three stage approach. The current design studies focus on implementing a normal conducting cathode insert into a newly developed superconducting photoinjector cavity. In this paper the fundamental RF design calculations concerning cell shape for optimized beam dynamics as well as SRF performance will be presented. Further studies concentrate on the HZDR based choke cell design to implement the high quantum efficiency normal conducting cathode with the SRF cavity.
	Slides THPLB12 [1.431 MB]

THPB066	Photoinjector SRF Cavity Development for BERLinPro	993
	A. Neumann, W. Anders, T. Kamps, J. Knobloch HZB, Berlin, Germany E.N. Zaplatin FZJ, Jülich, Germany
	In 2010 HZB has received approval to build BERLinPro, an ERL project to demonstrate energy recovery at 100 mA beam current by pertaining a high quality beam. These goals place stringent requirements on the SRF cavity for the photoinjector which has to deliver a small emittance 100 mA beam with at least 1.5 MeV kinetic energy while limited by fundamental power coupler performance to about 200 kW forward power. In oder to achieve these goals the injector cavity is being developed in a three stage approach. The current design studies focus on implementing a normal conducting cathode insert into a newly developed superconducting photoinjector cavity. In this paper the fundamental RF design calculations concerning cell shape for optimized beam dynamics as well as SRF performance will be presented. Further studies concentrate on the HZDR based choke cell design to implement the high quantum efficiency normal conducting cathode with the SRF cavity.