SRF2021 - List of Authors (Frahm, A.)

Paper	Title	Page
MOPTEV007	RF Conditioning of 120 kW CW 1.3 GHz High Power Couplers for the bERLinPro Energy Recovery Linac	216
	A. Neumann, W. Anders, A. Frahm, F. Göbel, A. Heugel, S. Klauke, J. Knobloch, M. Schuster, Y. Tamashevich HZB, Berlin, Germany
	Funding: The work is funded by the Helmholtz-Association, BMBF, the state of Berlin and HZB. This year, the commissioning of the 50 MeV, 100 mA bERLinPro Energy Recovery Linac test facility [1] will resume. For the Booster cryo-module of the injector line, operated with three modified 1.3 GHz Cornell style 2-cell SRF cavities, a new type of power coupler was developed, based on KEK’s C-ERL injector coupler. Modifications were made for a stronger coupling and lower emittance diluting coupler tip variant, a so-called "Golf Tee" shape and the cooling concept was redesigned based on KEK’s first experiences. For the final stage, the injector needs to deliver a low emittance beam of 100 mA average beam current at 6.5 MeV. That results in a traveling and continuous wave forward power requirement of up to 120 kW each of the twin setup feeding one Booster cavity. In this contribution we will give a short overview of the RF design and its impact on the beam’s emittance, give an overview of the conditioning teststand and the results achieved with the first pairs of couplers. [1] M. Abo-Bakr et al., in Proc. 9th Int. Particle Accelerator Conf. (IPAC’18), Vancouver, BC, Canada, Apr. 4,, pp. 4127-4130, doi:10.18429/JACoW-IPAC2018-THPMF034
	Poster MOPTEV007 [2.466 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPTEV007
About •	Received ※ 19 June 2021 — Accepted ※ 19 August 2021 — Issue date ※ 17 January 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPTEV013	The VSR Demo Module Design – A Spaceframe-Based Module for Cavities with Warm Waveguide HOM Absorbers	233
	F. Glöckner, D. Böhlick, M. Bürger, V. Dürr, A. Frahm, J. Knobloch, F. Pflocksch, A. Veléz, D. Wolk, N. Wunderer HZB, Berlin, Germany
	The VSR (Variable pulse length Storage Ring) demo module is a prototype for the superconducting upgrade of HZB’s Bessy II. The module houses two 1.5 GHz superconducting cavities operated at 1.8 K in continuous wave (CW) mode. Each cavity has five water cooled Waveguide HOM Absorbers with high thermal load (450 W), which requires them to be water cooled. This setup introduces several design challenges, concerning space restriction, the interconnection of warm and cold parts and the alignment. In order to provide support and steady alignment an innovative space frame was designed. The transition from cold to warm over the partially superconducting waveguides made a more complex design for shielding and cooling system necessary. With the design close to completion, we are now entering the purchase phase.
	Poster MOPTEV013 [3.239 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPTEV013
About •	Received ※ 21 June 2021 — Revised ※ 02 September 2021 — Accepted ※ 18 November 2021 — Issue date ※ 02 December 2021
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WEPTEV003	A Superconducting Magnetic Shield for SRF Modules with Strong Magnetic Field Sources	637
	J. Völker, A. Frahm, S. Keckert, J. Knobloch, A.N. Matveenko, A. Neumann, H. Plötz, Y. Tamashevich HZB, Berlin, Germany J. Knobloch University of Siegen, Siegen, Germany
	Frequently SRF modules require strong focusing magnets close to SRF cavities. The shielding of those magnetic fields to avoid flux trapping, for example during a quench, is a challenge. At HZB, the bERLinPro photo-injector module includes a 1.4 cell SRF cavity placed in close proximity to a superconducting (SC) focusing solenoid. At full solenoid operation, parts of the double mu-metal shield are expected to saturate. To prevent saturation, we developed a new superconducting Meissner-Shield. Several tests of different designs were performed both in the injector module and in the HoBiCaT test facility. The measured results of the final design show a significant shielding that are in good agreement with calculations. Based on these results, a reduction of the magnetic flux density in the mu-metal shields of almost one order of magnitude is expected The design has now been incorporated in the injector module. In this paper we will present the design, the setup and results of the final testing of the superconducting shield.
	Poster WEPTEV003 [1.859 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPTEV003
About •	Received ※ 21 June 2021 — Revised ※ 16 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 15 March 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTEV008	VSR Demo Cold String: Recent Developments and Manufacturing Status	647
	N. Wunderer, V. Dürr, A. Frahm, H.-W. Glock, F. Glöckner, J. Knobloch, E. Sharples-Milne, A.V. Tsakanian, A. Veléz HZB, Berlin, Germany M. Bonezzi, A. D’Ambros, R. Paparella INFN/LASA, Segrate (MI), Italy J. Guo, J. Henry, R.A. Rimmer JLab, Newport News, Virginia, USA J. Knobloch University of Siegen, Siegen, Germany A. Veléz Technical University Dortmund, Dortmund, Germany
	The BESSY VSR project aims to demonstrate the possibility to simultaneously run both long (15ps) and short bunches (1.7ps) within BESSY II storage ring. To achieve this, a new SRF cavity system with higher harmonic cavities (3 and 3.5 harm.) needs to be installed. The combined cavity SRF beating allows for stable bunch shortening for half of the buckets while standard lengths remaining for the other half. These SRF cavities will be equipped with waveguide-connected HOM absorbers and will be controlled with a blade tuner plus piezos. To demonstrate the feasibility of this complex system the VSR DEMO cold string consists of two 1.5 GHz cavities, each featuring five waveguides and a higher power coupler, plus all interconnecting elements coupled to the beam vacuum. For most of these components the fundamental development work is completed and has been reported in the past. This paper summarizes recent enhancements, component detailing and manufacturing status. The key cold string components such as cavities, higher power couplers and blade tuners have already entered the manufacturing phase. All other cold string components will be ready for purchase at the latest beginning of 2022.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPTEV008
About •	Received ※ 18 June 2021 — Revised ※ 09 August 2021 — Accepted ※ 22 November 2021 — Issue date ※ 05 January 2022
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WEOCAV07	Damage Recovery for SRF Photoinjector Cavities
	Y. Tamashevich, A. Frahm, F. Göbel, S. Heling, A. Hellwig, K. Janke, S. Klauke, J. Knobloch, A.N. Matveenko, A. Neumann, H. Plötz, A.L. Prudnikava, S. Rotterdam, M. Schuster, J. Ullrich HZB, Berlin, Germany
	Two niobium elliptical 1.3 GHz SRF electron photoinjector cavities were successfully recovered after mechanical inner surface damage. Both injector cavities had deep imprints in critical high surface electric field area around the photoelectric cathode position. The repairing procedure, consisting of surface inspection, mechanical polishing and light chemical etching is described in detail. Subsequent cold RF tests demonstrate complete performance recovery.
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

RF Conditioning of 120 kW CW 1.3 GHz High Power Couplers for the bERLinPro Energy Recovery Linac

216

A. Neumann, W. Anders, A. Frahm, F. Göbel, A. Heugel, S. Klauke, J. Knobloch, M. Schuster, Y. Tamashevich
HZB, Berlin, Germany

Funding: The work is funded by the Helmholtz-Association, BMBF, the state of Berlin and HZB.
This year, the commissioning of the 50 MeV, 100 mA bERLinPro Energy Recovery Linac test facility [1] will resume. For the Booster cryo-module of the injector line, operated with three modified 1.3 GHz Cornell style 2-cell SRF cavities, a new type of power coupler was developed, based on KEK’s C-ERL injector coupler. Modifications were made for a stronger coupling and lower emittance diluting coupler tip variant, a so-called "Golf Tee" shape and the cooling concept was redesigned based on KEK’s first experiences. For the final stage, the injector needs to deliver a low emittance beam of 100 mA average beam current at 6.5 MeV. That results in a traveling and continuous wave forward power requirement of up to 120 kW each of the twin setup feeding one Booster cavity. In this contribution we will give a short overview of the RF design and its impact on the beam’s emittance, give an overview of the conditioning teststand and the results achieved with the first pairs of couplers.
[1] M. Abo-Bakr et al., in Proc. 9th Int. Particle Accelerator Conf. (IPAC’18), Vancouver, BC, Canada, Apr. 4,, pp. 4127-4130, doi:10.18429/JACoW-IPAC2018-THPMF034

Poster MOPTEV007 [2.466 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPTEV007

About •

Received ※ 19 June 2021 — Accepted ※ 19 August 2021 — Issue date ※ 17 January 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPTEV013

The VSR Demo Module Design – A Spaceframe-Based Module for Cavities with Warm Waveguide HOM Absorbers

233

F. Glöckner, D. Böhlick, M. Bürger, V. Dürr, A. Frahm, J. Knobloch, F. Pflocksch, A. Veléz, D. Wolk, N. Wunderer
HZB, Berlin, Germany

The VSR (Variable pulse length Storage Ring) demo module is a prototype for the superconducting upgrade of HZB’s Bessy II. The module houses two 1.5 GHz superconducting cavities operated at 1.8 K in continuous wave (CW) mode. Each cavity has five water cooled Waveguide HOM Absorbers with high thermal load (450 W), which requires them to be water cooled. This setup introduces several design challenges, concerning space restriction, the interconnection of warm and cold parts and the alignment. In order to provide support and steady alignment an innovative space frame was designed. The transition from cold to warm over the partially superconducting waveguides made a more complex design for shielding and cooling system necessary. With the design close to completion, we are now entering the purchase phase.

Poster MOPTEV013 [3.239 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPTEV013

About •

Received ※ 21 June 2021 — Revised ※ 02 September 2021 — Accepted ※ 18 November 2021 — Issue date ※ 02 December 2021

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTEV003

A Superconducting Magnetic Shield for SRF Modules with Strong Magnetic Field Sources

637

J. Völker, A. Frahm, S. Keckert, J. Knobloch, A.N. Matveenko, A. Neumann, H. Plötz, Y. Tamashevich
HZB, Berlin, Germany
J. Knobloch
University of Siegen, Siegen, Germany

Frequently SRF modules require strong focusing magnets close to SRF cavities. The shielding of those magnetic fields to avoid flux trapping, for example during a quench, is a challenge. At HZB, the bERLinPro photo-injector module includes a 1.4 cell SRF cavity placed in close proximity to a superconducting (SC) focusing solenoid. At full solenoid operation, parts of the double mu-metal shield are expected to saturate. To prevent saturation, we developed a new superconducting Meissner-Shield. Several tests of different designs were performed both in the injector module and in the HoBiCaT test facility. The measured results of the final design show a significant shielding that are in good agreement with calculations. Based on these results, a reduction of the magnetic flux density in the mu-metal shields of almost one order of magnitude is expected The design has now been incorporated in the injector module. In this paper we will present the design, the setup and results of the final testing of the superconducting shield.

Poster WEPTEV003 [1.859 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPTEV003

About •

Received ※ 21 June 2021 — Revised ※ 16 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 15 March 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTEV008

VSR Demo Cold String: Recent Developments and Manufacturing Status

647

N. Wunderer, V. Dürr, A. Frahm, H.-W. Glock, F. Glöckner, J. Knobloch, E. Sharples-Milne, A.V. Tsakanian, A. Veléz
HZB, Berlin, Germany
M. Bonezzi, A. D’Ambros, R. Paparella
INFN/LASA, Segrate (MI), Italy
J. Guo, J. Henry, R.A. Rimmer
JLab, Newport News, Virginia, USA
J. Knobloch
University of Siegen, Siegen, Germany
A. Veléz
Technical University Dortmund, Dortmund, Germany

The BESSY VSR project aims to demonstrate the possibility to simultaneously run both long (15ps) and short bunches (1.7ps) within BESSY II storage ring. To achieve this, a new SRF cavity system with higher harmonic cavities (3 and 3.5 harm.) needs to be installed. The combined cavity SRF beating allows for stable bunch shortening for half of the buckets while standard lengths remaining for the other half. These SRF cavities will be equipped with waveguide-connected HOM absorbers and will be controlled with a blade tuner plus piezos. To demonstrate the feasibility of this complex system the VSR DEMO cold string consists of two 1.5 GHz cavities, each featuring five waveguides and a higher power coupler, plus all interconnecting elements coupled to the beam vacuum. For most of these components the fundamental development work is completed and has been reported in the past. This paper summarizes recent enhancements, component detailing and manufacturing status. The key cold string components such as cavities, higher power couplers and blade tuners have already entered the manufacturing phase. All other cold string components will be ready for purchase at the latest beginning of 2022.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPTEV008

About •

Received ※ 18 June 2021 — Revised ※ 09 August 2021 — Accepted ※ 22 November 2021 — Issue date ※ 05 January 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEOCAV07

Damage Recovery for SRF Photoinjector Cavities

Y. Tamashevich, A. Frahm, F. Göbel, S. Heling, A. Hellwig, K. Janke, S. Klauke, J. Knobloch, A.N. Matveenko, A. Neumann, H. Plötz, A.L. Prudnikava, S. Rotterdam, M. Schuster, J. Ullrich
HZB, Berlin, Germany

Two niobium elliptical 1.3 GHz SRF electron photoinjector cavities were successfully recovered after mechanical inner surface damage. Both injector cavities had deep imprints in critical high surface electric field area around the photoelectric cathode position. The repairing procedure, consisting of surface inspection, mechanical polishing and light chemical etching is described in detail. Subsequent cold RF tests demonstrate complete performance recovery.

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)