IPAC2016 - List of Authors (Ruprecht, M.)

Paper	Title	Page
TUPOR004	Calculation of Transverse Coupled Bunch Instabilities in Electron Storage Rings Driven By Quadrupole Higher Order Modes	1655
	M. Ruprecht, P. Goslawski, M. Ries, G. Wüstefeld HZB, Berlin, Germany
	This paper presents a formula that estimates the growth rate of a transverse coupled bunch instability driven by quadrupole higher order modes (HOMs) in electron storage rings. Thus far, quadrupole HOMs are usually ignored in HOM driven instability studies for electron storage rings due to their weak nature compared to the lower orders. However, they may become relevant when high gradient SC multi-cell cavities with their potentially strong impedance spectrum are operated at high currents in a third generation or future synchrotron light source. An example is BESSY VSR, a scheme where 1.7 ps and 15 ps long bunches (rms) can be stored simultaneously in the BESSY II storage ring[]. With the presented formula, instability thresholds are discussed for a recent BESSY VSR cavity model and different beam parameters. A. Jankowiak, J. Knobloch, P. Goslawski, and N. Neumann, eds., BESSY VSR - Technical Design Study, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 2015.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR004
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WEPOW007	Status and Prospects of the BESSY II Injector System	2826
	T. Atkinson, W. Anders, P. Goslawski, A. Jankowiak, F. Kramer, P. Kuske, D. Malyutin, A.N. Matveenko, A. Neumann, M. Ries, M. Ruprecht, A. Schälicke, T. Schneegans, D. Schüler, P.I. Volz, G. Wüstefeld HZB, Berlin, Germany H.G. Glass BESSY GmbH, Berlin, Germany
	The BESSY II injector system consists of a 50 MeV Linac, installed in preparation for TopUp operation, and a 10 Hz fast-ramping booster synchrotron. The system provides injection efficiencies into the BESSY II storage ring well above 90 % . This contribution reports on the present status, measurements of energy acceptance and other essential beam parameters as well as studies on coupled-bunch-by-bunch instability. Requirements for BESSY-VSR and possible upgrade scenarios are discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW007
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WEPOW008	Specific Operation Modes at the Metrology Light Source	2829
	J. Feikes, P. Goslawski, J. Li, M. Ries, M. Ruprecht, G. Wüstefeld HZB, Berlin, Germany A. Hoehl PTB, Berlin, Germany
	The high flexibility of the Metrology Light Source (MLS) allows application of various nonstandard user modes adapted to the specific needs of their users. We report on some of them including a mode for division of the revolution frequency for the user signal and a mode with an adjustable photon pulse delay on the few ps scale.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW008
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WEPOW009	The Bessy Vsr Project for Short X-Ray Pulse Production	2833
	A. Jankowiak, W. Anders, T. Atkinson, H. Ehmler, A. Föhlisch, P. Goslawski, K. Holldack, J. Knobloch, P. Kuske, D. Malyutin, A.N. Matveenko, R. Müller, A. Neumann, K. Ott, M. Ries, M. Ruprecht, A. Schälicke, A.V. Vélez, G. Wüstefeld HZB, Berlin, Germany A. Burrill SLAC, Menlo Park, California, USA
	Funding: Work supported by the German Bundesministerium für Bildung und Forschung, Land Berlin and grants of the Helmholtz Association HZB has started the innovative project, BESSY VSR, to upgrade the 1.7 GeV synchrotron radiation source BESSY II. Its goal is to provide both 1.7 ps and 15 ps long, intense X-ray pulses simultaneously at all beam lines. These pulses are generated by enhanced longitudinal bunch focusing using superconducting 5-cell cavities operating at 1.5 GHz and 1.75 GHz. The resulting beating of the voltages creates alternating long and short buckets that can be custom filled. As a first major step, prototype superconducting cavities, initially only cooled to 4.4 K and thus operating at reduced voltage, will be installed into the BESSY II storage ring. Physical and technical aspects of this proposal where recently studied* and the results and project status are presented. * A. Jankowiak, J. Knobloch for the BESSY VSR team, Technical Design Study BESSY VSR, doi:10.5442/R0001, Helmholtz-Zentrum Berlin (Germany), June 2015.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW009
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WEPOW010	Beam Lifetime Optimization by Adjusting the Sextupoles at the MLS and BESSY	2837
	J. Li, J. Feikes, P. Goslawski, M. Ries, M. Ruprecht, T. Tydecks HZB, Berlin, Germany
	The Metrology Light Source (MLS) is a dedicated elec-tron storage ring for metrology applications with three families of sextupoles. The existing setting of the three independently powered sextupole families respective to lifetime were roughly determined by scanning their strengths against each other. As a flexible machine the sextupole families of the MLS can be regrouped into new families, which increase the complexity of the scan pro-cedure. Consequently the former strategy would be too time-consuming for refined global scan and it has to be complemented with physical constraints. Therefore a scheme has been developed to keep the chromaticity in a reasonable range during the scan and to reduce the degree of freedom, which is even more important at BESSY II with increasing number of independent sextupole cir-cuits. This paper presents the principle of sextupole scan and the experimental results at the MLS and preliminary test at BESSY II.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW010
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WEPOW012	Hardware Upgrades Improve the Reliability at BESSY II	2844
	A. Schälicke, W. Anders, J. Borninkhof, V. Dürr, P. Goslawski, A. Hellwig, A. Heugel, H.-G. Hoberg, H. Hoffmann, A. Jankowiak, J. Kolbe, P. Kuske, G. Mielczarek, R. Müller, D. Pflückhahn, M. Ries, S. Rotterdam, M. Ruprecht, B. Schriefer, D. Simmering, H. Stein HZB, Berlin, Germany
	The synchrotron light source BESSY II is now in its second decade of operation. Already in 2013 both top-up and fast orbit feedback have been introduced into user operation. Currently, the facility is undergoing significant hardware upgrades in order to fulfill the increasing demands of its user community in terms of reliability, stability and flexibility. These include replacement of the DORIS cavities with EU HOM damped cavities, the upgrade of the RF transmitters to solid state amplifiers, implementation of the shifted waist optics for the new in-vacuum undulator, and refurbishment of the superconducting multi-pole wiggler. In this contribution status of BESSY II operation and the upgrade projects is reported.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW012
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THPMR017	Resonance Island Experiments at BESSY II for User Applications	3427
	P. Goslawski, J. Feikes, K. Holldack, A. Jankowiak, M. Ries, M. Ruprecht, A. Schälicke, G. Wüstefeld HZB, Berlin, Germany R. Ovsyannikov BESSY GmbH, Berlin, Germany
	Beam storage close to a tune resonance (Qx = 1/3, 1/4) can generate resonance island buckets in the x,x' phase space providing a second stable island orbit winding around the standard orbit. Experiments with such an operation mode have been conducted at BESSY II and the Metrology Light Source (MLS),. The two orbits are well separated, with good life time and stability. Such operation mode will offer additional operation flexibility and allows users to choose their radiation source point from one or the other orbit. It has the potential to fulfill simultaneously conflicting user demands, e.g., high vs. low beam current and single or few bunch filling vs. multibunch filling. We discuss the required beam optics setup and present successful measurements taken at photon beamlines at BESSY II. P. Goslawski et al., "Bunch Separation by Transverse Resonance Island Buckets", ESLS XXIII Workshop, 2015, Villigen, Switzerland. ** M. Ries et al., Proc. IPAC 2015, Richmond, USA, MOPWA021.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR017
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THPOW039	Measurements of the Lattice Modifications for the Cryogenic Undulator CPMU17	4031
	J. Bahrdt, D.B. Engel, W. Frentrup, P. Goslawski, P. Kuske, R. Müller, M. Ries, M. Ruprecht, A. Schälicke HZB, Berlin, Germany
	A 2 mrad-canted double undulator system is in preparation as the wide energy range light source for the Energy Material in-situ Laboratory EMIL at the HZB storage ring BESSY II. The cryogenic undulator CPMU-17 is the hard X-ray device of the double undulator system. The soft X-ray undulator UE-48 is of the APPLE II type. It was installed and commissioned a few months ago, whereas the CPMU-17 is under fabrication. The CPMU-17 will employ a minimum magnetic gap of 5.5mm. Including a CuNi-foil for RF-shielding and geometric tolerances the free aperture is planned to be 5.0 mm. The BESSY II lattice has been modified locally in order to cope with the small gap device. The adapted betatron functions with a shifted vertical beam waist were measured and fitted with LOCO. The new optics agrees with the predicted performance. The free aperture at the installation place of the CPMU-17 was measured with four vertical scrapers. It is compatible with the projected minimum undulator gap. Finally, the measured injection efficiency with the new EMIL optics switched on is compatible with top-up operation (injection efficiency ≥ 90 %).
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW039
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Paper

Title

Page

Calculation of Transverse Coupled Bunch Instabilities in Electron Storage Rings Driven By Quadrupole Higher Order Modes

1655

M. Ruprecht, P. Goslawski, M. Ries, G. Wüstefeld
HZB, Berlin, Germany

This paper presents a formula that estimates the growth rate of a transverse coupled bunch instability driven by quadrupole higher order modes (HOMs) in electron storage rings. Thus far, quadrupole HOMs are usually ignored in HOM driven instability studies for electron storage rings due to their weak nature compared to the lower orders. However, they may become relevant when high gradient SC multi-cell cavities with their potentially strong impedance spectrum are operated at high currents in a third generation or future synchrotron light source. An example is BESSY VSR, a scheme where 1.7 ps and 15 ps long bunches (rms) can be stored simultaneously in the BESSY II storage ring[*]. With the presented formula, instability thresholds are discussed for a recent BESSY VSR cavity model and different beam parameters.
* A. Jankowiak, J. Knobloch, P. Goslawski, and N. Neumann, eds., BESSY VSR - Technical Design Study, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 2015.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR004

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WEPOW007

Status and Prospects of the BESSY II Injector System

2826

T. Atkinson, W. Anders, P. Goslawski, A. Jankowiak, F. Kramer, P. Kuske, D. Malyutin, A.N. Matveenko, A. Neumann, M. Ries, M. Ruprecht, A. Schälicke, T. Schneegans, D. Schüler, P.I. Volz, G. Wüstefeld
HZB, Berlin, Germany
H.G. Glass
BESSY GmbH, Berlin, Germany

The BESSY II injector system consists of a 50 MeV Linac, installed in preparation for TopUp operation, and a 10 Hz fast-ramping booster synchrotron. The system provides injection efficiencies into the BESSY II storage ring well above 90 % . This contribution reports on the present status, measurements of energy acceptance and other essential beam parameters as well as studies on coupled-bunch-by-bunch instability. Requirements for BESSY-VSR and possible upgrade scenarios are discussed.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW007

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WEPOW008

Specific Operation Modes at the Metrology Light Source

2829

J. Feikes, P. Goslawski, J. Li, M. Ries, M. Ruprecht, G. Wüstefeld
HZB, Berlin, Germany
A. Hoehl
PTB, Berlin, Germany

The high flexibility of the Metrology Light Source (MLS) allows application of various nonstandard user modes adapted to the specific needs of their users. We report on some of them including a mode for division of the revolution frequency for the user signal and a mode with an adjustable photon pulse delay on the few ps scale.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW008

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WEPOW009

The Bessy Vsr Project for Short X-Ray Pulse Production

2833

A. Jankowiak, W. Anders, T. Atkinson, H. Ehmler, A. Föhlisch, P. Goslawski, K. Holldack, J. Knobloch, P. Kuske, D. Malyutin, A.N. Matveenko, R. Müller, A. Neumann, K. Ott, M. Ries, M. Ruprecht, A. Schälicke, A.V. Vélez, G. Wüstefeld
HZB, Berlin, Germany
A. Burrill
SLAC, Menlo Park, California, USA

Funding: Work supported by the German Bundesministerium für Bildung und Forschung, Land Berlin and grants of the Helmholtz Association
HZB has started the innovative project, BESSY VSR, to upgrade the 1.7 GeV synchrotron radiation source BESSY II. Its goal is to provide both 1.7 ps and 15 ps long, intense X-ray pulses simultaneously at all beam lines. These pulses are generated by enhanced longitudinal bunch focusing using superconducting 5-cell cavities operating at 1.5 GHz and 1.75 GHz. The resulting beating of the voltages creates alternating long and short buckets that can be custom filled. As a first major step, prototype superconducting cavities, initially only cooled to 4.4 K and thus operating at reduced voltage, will be installed into the BESSY II storage ring. Physical and technical aspects of this proposal where recently studied* and the results and project status are presented.
* A. Jankowiak, J. Knobloch for the BESSY VSR team, Technical Design Study BESSY VSR, doi:10.5442/R0001, Helmholtz-Zentrum Berlin (Germany), June 2015.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW009

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WEPOW010

Beam Lifetime Optimization by Adjusting the Sextupoles at the MLS and BESSY

2837

J. Li, J. Feikes, P. Goslawski, M. Ries, M. Ruprecht, T. Tydecks
HZB, Berlin, Germany

The Metrology Light Source (MLS) is a dedicated elec-tron storage ring for metrology applications with three families of sextupoles. The existing setting of the three independently powered sextupole families respective to lifetime were roughly determined by scanning their strengths against each other. As a flexible machine the sextupole families of the MLS can be regrouped into new families, which increase the complexity of the scan pro-cedure. Consequently the former strategy would be too time-consuming for refined global scan and it has to be complemented with physical constraints. Therefore a scheme has been developed to keep the chromaticity in a reasonable range during the scan and to reduce the degree of freedom, which is even more important at BESSY II with increasing number of independent sextupole cir-cuits. This paper presents the principle of sextupole scan and the experimental results at the MLS and preliminary test at BESSY II.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW010

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WEPOW012

Hardware Upgrades Improve the Reliability at BESSY II

2844

A. Schälicke, W. Anders, J. Borninkhof, V. Dürr, P. Goslawski, A. Hellwig, A. Heugel, H.-G. Hoberg, H. Hoffmann, A. Jankowiak, J. Kolbe, P. Kuske, G. Mielczarek, R. Müller, D. Pflückhahn, M. Ries, S. Rotterdam, M. Ruprecht, B. Schriefer, D. Simmering, H. Stein
HZB, Berlin, Germany

The synchrotron light source BESSY II is now in its second decade of operation. Already in 2013 both top-up and fast orbit feedback have been introduced into user operation. Currently, the facility is undergoing significant hardware upgrades in order to fulfill the increasing demands of its user community in terms of reliability, stability and flexibility. These include replacement of the DORIS cavities with EU HOM damped cavities, the upgrade of the RF transmitters to solid state amplifiers, implementation of the shifted waist optics for the new in-vacuum undulator, and refurbishment of the superconducting multi-pole wiggler. In this contribution status of BESSY II operation and the upgrade projects is reported.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW012

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THPMR017

Resonance Island Experiments at BESSY II for User Applications

3427

P. Goslawski, J. Feikes, K. Holldack, A. Jankowiak, M. Ries, M. Ruprecht, A. Schälicke, G. Wüstefeld
HZB, Berlin, Germany
R. Ovsyannikov
BESSY GmbH, Berlin, Germany

Beam storage close to a tune resonance (Qx = 1/3, 1/4) can generate resonance island buckets in the x,x' phase space providing a second stable island orbit winding around the standard orbit. Experiments with such an operation mode have been conducted at BESSY II and the Metrology Light Source (MLS)*,**. The two orbits are well separated, with good life time and stability. Such operation mode will offer additional operation flexibility and allows users to choose their radiation source point from one or the other orbit. It has the potential to fulfill simultaneously conflicting user demands, e.g., high vs. low beam current and single or few bunch filling vs. multibunch filling. We discuss the required beam optics setup and present successful measurements taken at photon beamlines at BESSY II.
* P. Goslawski et al., "Bunch Separation by Transverse Resonance Island Buckets", ESLS XXIII Workshop, 2015, Villigen, Switzerland.
** M. Ries et al., Proc. IPAC 2015, Richmond, USA, MOPWA021.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR017

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THPOW039

Measurements of the Lattice Modifications for the Cryogenic Undulator CPMU17

4031

J. Bahrdt, D.B. Engel, W. Frentrup, P. Goslawski, P. Kuske, R. Müller, M. Ries, M. Ruprecht, A. Schälicke
HZB, Berlin, Germany

A 2 mrad-canted double undulator system is in preparation as the wide energy range light source for the Energy Material in-situ Laboratory EMIL at the HZB storage ring BESSY II. The cryogenic undulator CPMU-17 is the hard X-ray device of the double undulator system. The soft X-ray undulator UE-48 is of the APPLE II type. It was installed and commissioned a few months ago, whereas the CPMU-17 is under fabrication. The CPMU-17 will employ a minimum magnetic gap of 5.5mm. Including a CuNi-foil for RF-shielding and geometric tolerances the free aperture is planned to be 5.0 mm. The BESSY II lattice has been modified locally in order to cope with the small gap device. The adapted betatron functions with a shifted vertical beam waist were measured and fitted with LOCO. The new optics agrees with the predicted performance. The free aperture at the installation place of the CPMU-17 was measured with four vertical scrapers. It is compatible with the projected minimum undulator gap. Finally, the measured injection efficiency with the new EMIL optics switched on is compatible with top-up operation (injection efficiency ≥ 90 %).

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW039

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