IPAC2018 - List of Authors (Tsakanian, A.V.)

Paper	Title	Page
WEPML047	Study on RF Coupler Kicks of SRF Cavities in the BESSY VSR Module	2804
	A.V. Tsakanian, T. Mertens Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany H.-W. Glock, J. Knobloch, M. Ries, A.V. Vélez HZB, Berlin, Germany
	The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store long (ca. 15ps) and short (ca. 1.7ps) bunches in the storage ring with the standard user optics. This challenging goal requires installation of four new SRF multi-cell cavities (2x1.5GHz and 2x1.75GHz) equipped with strong waveguide HOM dampers ensuring tolerable beam coupling impedance, necessary for stable operation. These cavities will operate at high 20MV/m in CW mode and at the zero-crossing phase according to the accelerating voltage. Consequently the transverse voltages will be maximum and can impact the transverse beam dynamics. The asymmetric character of those transverse kicks are caused by cavity fundamental power couplers (FPC) with strong monopole terms, introducing transverse kick to on-axis particles. Different FPC orientations were analyzed to optimize the net coupler kick from the four cavity chain. The coupler kick strength of each cavity is estimated taking into account accelerating mode amplitudes and phases required for operation in VSR mode.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML047
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WEPML048	HOM Power Levels in the BESSY VSR Cold String	2808
	A.V. Tsakanian, T. Flisgen Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany H.-W. Glock, J. Knobloch, A.V. Vélez HZB, Berlin, Germany
	The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store long (ca. 15ps) and short (ca. 1.7ps) bunches in the storage ring. This challenging goal requires installation of four new SRF cavities (2x1.5 GHz and 2x1.75 GHz) in one module for installation in a single straight. These cavities are equipped with strong waveguide HOM dampers necessary for stable operation. The expected HOM power and spectrum has been analyzed for the complete cold string. The cold string is a combination of various elements such as SRF cavities, bellows with and without shielding, warm HOM beampipe absorbers and UHV pumping domes. The presented study is performed for various BESSY VSR bunch filling patterns with 300 mA beam current. The contribution of each component to the total HOM power is presented. In addition the optimization of different cavity arrangements in the module is performed in order to reach the optimal operation conditions with equally distributed power levels along the string and tolerable beam coupling impedance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML048
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THPAF085	Estimation of Dielectric Losses in the Bessy VSR Warm Beam Pipe Absorbers	3185
	T. Flisgen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany H.-W. Glock HZB, Berlin, Germany A.V. Tsakanian Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
	Funding: Work supported by the German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association. Currently Helmholtz Zentrum Berlin prepares the update of the BESSY II ring to BESSY VSR. The updated ring will be capable to simultaneously store short and long bunches to satisfy the various user demands. For this sake, a cryomodule accommodating two 1.5 GHz and two 1.75 GHz superconducting cavities will be installed into the storage ring. The cavity string will be equipped with warm dielectric absorber rings at both ends. Together with the waveguide dampers of the cavities, these rings damp electromagnetic fields excited by the beam. This contribution presents the estimation of the dielectric losses in the beam pipe absorber rings of the BESSY VSR module. The presented approach is based on determining a broad band impedance of the dielectric ring by exciting the numerical model with a single broad band Gaussian bunch. Subsequently, the power deposited into the ring is estimated in frequency domain by multiplying the impedance with the square of the beam current for all considered harmonics of the beam. Finally, these power contributions are added up. In addition to details of the scheme, the contribution presents results for the recent absorber layout of the BESSY VSR string.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF085
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THPAF084	Impact of RF Coupler Kicks on Beam Dynamics in BESSY VSR	3182
	T. Mertens Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany T. Atkinson, F. Glöckner, A. Jankowiak, M. Ries, A.V. Tsakanian HZB, Berlin, Germany
	The expected BESSY II upgrade to BESSY VSR requires the installation of a superconducting RF system, consisting of four cavities. Two cavities will operate at 1.5 GHz and two at 1.75 GHz. Each of them is equipped with a Fundamental Power Coupler and with Higher Order Mode (HOM) damping waveguide couplers. Dedicated simulations of these cavities and couplers have shown that at the location of the FPC the beam will see a transverse kick [], perturbing the closed orbit and affecting transverse beam dynamics. We present the results of simulations and experiments of the impact on transverse beam dynamics of these coupler induced kicks for different FPC orientations. [] Study on RF Coupler Kicks of SRF Cavities in the BESSY VSR Module A. Tsakanian#, H.-W. Glock, T. Mertens, M. Ries, A. Velez, J. Knobloch IPAC18
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF084
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THPMF033	Design of the Beamline Elements in the BESSY VSR Cold String	4123
	H.-W. Glock, F. Glöckner, J. Knobloch, E. Sharples, A.V. Tsakanian, A.V. Vélez HZB, Berlin, Germany T. Flisgen Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of the Helmholtz Association The four SRF cavities in the BESSY VSR module will be linked by bellows, which will be equipped with inner coaxial shielding pipes to prevent both parasitic fundamental mode losses and beam-induced heating. The central bellow will also act as a collimator for synchrotron radiation generated in the closest upstream dipole magnet. Additional bellows at the module's ends are needed to connect with the warm BESSY beam pipe. Outside the module the beam pipe cross section transitions will be located, which will be equipped with toroidal HOM absorbing elements. In the paper the recent design considerations and specifications for all those components will be described.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF033
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Study on RF Coupler Kicks of SRF Cavities in the BESSY VSR Module

2804

A.V. Tsakanian, T. Mertens
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
H.-W. Glock, J. Knobloch, M. Ries, A.V. Vélez
HZB, Berlin, Germany

The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store long (ca. 15ps) and short (ca. 1.7ps) bunches in the storage ring with the standard user optics. This challenging goal requires installation of four new SRF multi-cell cavities (2x1.5GHz and 2x1.75GHz) equipped with strong waveguide HOM dampers ensuring tolerable beam coupling impedance, necessary for stable operation. These cavities will operate at high 20MV/m in CW mode and at the zero-crossing phase according to the accelerating voltage. Consequently the transverse voltages will be maximum and can impact the transverse beam dynamics. The asymmetric character of those transverse kicks are caused by cavity fundamental power couplers (FPC) with strong monopole terms, introducing transverse kick to on-axis particles. Different FPC orientations were analyzed to optimize the net coupler kick from the four cavity chain. The coupler kick strength of each cavity is estimated taking into account accelerating mode amplitudes and phases required for operation in VSR mode.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML047

Export •

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

WEPML048

HOM Power Levels in the BESSY VSR Cold String

2808

A.V. Tsakanian, T. Flisgen
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
H.-W. Glock, J. Knobloch, A.V. Vélez
HZB, Berlin, Germany

The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store long (ca. 15ps) and short (ca. 1.7ps) bunches in the storage ring. This challenging goal requires installation of four new SRF cavities (2x1.5 GHz and 2x1.75 GHz) in one module for installation in a single straight. These cavities are equipped with strong waveguide HOM dampers necessary for stable operation. The expected HOM power and spectrum has been analyzed for the complete cold string. The cold string is a combination of various elements such as SRF cavities, bellows with and without shielding, warm HOM beampipe absorbers and UHV pumping domes. The presented study is performed for various BESSY VSR bunch filling patterns with 300 mA beam current. The contribution of each component to the total HOM power is presented. In addition the optimization of different cavity arrangements in the module is performed in order to reach the optimal operation conditions with equally distributed power levels along the string and tolerable beam coupling impedance.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML048

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

THPAF085

Estimation of Dielectric Losses in the Bessy VSR Warm Beam Pipe Absorbers

3185

T. Flisgen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
H.-W. Glock
HZB, Berlin, Germany
A.V. Tsakanian
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany

Funding: Work supported by the German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association.
Currently Helmholtz Zentrum Berlin prepares the update of the BESSY II ring to BESSY VSR. The updated ring will be capable to simultaneously store short and long bunches to satisfy the various user demands. For this sake, a cryomodule accommodating two 1.5 GHz and two 1.75 GHz superconducting cavities will be installed into the storage ring. The cavity string will be equipped with warm dielectric absorber rings at both ends. Together with the waveguide dampers of the cavities, these rings damp electromagnetic fields excited by the beam. This contribution presents the estimation of the dielectric losses in the beam pipe absorber rings of the BESSY VSR module. The presented approach is based on determining a broad band impedance of the dielectric ring by exciting the numerical model with a single broad band Gaussian bunch. Subsequently, the power deposited into the ring is estimated in frequency domain by multiplying the impedance with the square of the beam current for all considered harmonics of the beam. Finally, these power contributions are added up. In addition to details of the scheme, the contribution presents results for the recent absorber layout of the BESSY VSR string.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF085

Export •

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

THPAF084

Impact of RF Coupler Kicks on Beam Dynamics in BESSY VSR

3182

T. Mertens
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
T. Atkinson, F. Glöckner, A. Jankowiak, M. Ries, A.V. Tsakanian
HZB, Berlin, Germany

The expected BESSY II upgrade to BESSY VSR requires the installation of a superconducting RF system, consisting of four cavities. Two cavities will operate at 1.5 GHz and two at 1.75 GHz. Each of them is equipped with a Fundamental Power Coupler and with Higher Order Mode (HOM) damping waveguide couplers. Dedicated simulations of these cavities and couplers have shown that at the location of the FPC the beam will see a transverse kick [*], perturbing the closed orbit and affecting transverse beam dynamics. We present the results of simulations and experiments of the impact on transverse beam dynamics of these coupler induced kicks for different FPC orientations.
[*] Study on RF Coupler Kicks of SRF Cavities in the BESSY VSR Module
A. Tsakanian#, H.-W. Glock, T. Mertens, M. Ries, A. Velez, J. Knobloch
IPAC18

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF084

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

THPMF033

Design of the Beamline Elements in the BESSY VSR Cold String

4123

H.-W. Glock, F. Glöckner, J. Knobloch, E. Sharples, A.V. Tsakanian, A.V. Vélez
HZB, Berlin, Germany
T. Flisgen
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of the Helmholtz Association
The four SRF cavities in the BESSY VSR module will be linked by bellows, which will be equipped with inner coaxial shielding pipes to prevent both parasitic fundamental mode losses and beam-induced heating. The central bellow will also act as a collimator for synchrotron radiation generated in the closest upstream dipole magnet. Additional bellows at the module's ends are needed to connect with the warm BESSY beam pipe. Outside the module the beam pipe cross section transitions will be located, which will be equipped with toroidal HOM absorbing elements. In the paper the recent design considerations and specifications for all those components will be described.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF033

Export •

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