IPAC2014 - List of Authors (Wuestefeld, G.)

Paper	Title	Page
MOPRO058	The Low-alpha Lattice and Bunch Length Limits at BESSY-VSR	216
	P. Goslawski, M. Ries, M. Ruprecht, G. Wüstefeld HZB, Berlin, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung and Land Berlin. An upgrade of the BESSY II ring to a Variable bunch length Storage Ring BESSY^VSR has been recently proposed , by introducing strongly focusing superconducting cavities. This will allow to store simultaneously long and short bunches. In the regular user optics, bunch lengths of 15 ps (rms) and down to 1.5 ps (rms) are expected. Bunches as short as 300 fs (rms), close to the bunch length limit, and a ring current of 3.5 mA at the bunch bursting threshold can be provided by using a modified low-alpha optics. This presentation will discuss the properties of the low-alpha optics and intrinsic bunch length limits, given by coupling effects of the longitudinal and horizontal plane. G. Wüstefeld, A. Jankowiak, J. Knobloch, M.Ries, "Simultaneous Long and Short Electron Bunches in the BESSYII Storage Ring", Proceedings of IPAC2011, San Sebastian, Spain.
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TUPRI043	Analysis of Coupled Bunch Instabilities in BESSY-VSR	1659
	M. Ruprecht, P. Goslawski, A. Jankowiak, M. Ries, A. Schälicke, G. Wüstefeld HZB, Berlin, Germany T. Weis DELTA, Dortmund, Germany
	BESSY-VSR, a scheme where 1.5 ps and 15 ps long bunches (rms) can be stored simultaneously in the BESSY II storage ring has recently been proposed. The strong longitudinal bunch focusing is achieved by superconducting high gradient RF cavities. This paper presents investigations of coupled bunch instabilities driven by HOMs of superconducting multi cell cavities in BESSY-VSR. Analytical calculations and tracking simulations in time domain are performed in the longitudinal and the transverse planes and factors that influence the threshold currents are being discussed. Suitable candidates of cavities which are presently available or in the phase of design are compared with respect to their instability thresholds. G. Wüstefeld, A. Jankowiak, J. Knobloch, M. Ries, Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring, Proceedings of IPAC2011, San Sebastián, Spain
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI043
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WEPRO028	A Robinson Wiggler Proposal for the Metrology Light Source	2001
	T. Goetsch, J. Feikes, M. Ries, G. Wüstefeld HZB, Berlin, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung and Land Berlin. The Metrology Light Source (MLS), situated in Berlin (Germany) is owned by the Physikalisch-Technische Bundesanstalt and was built / is operated by the Helmholtz-Zentrum Berlin. It is an electron storage ring operating from 10⁵ MeV to 630 MeV. The MLS serves as the national primary source standard from the near infrared to the extreme ultraviolet spectral region . Users of synchrotron radiation demand an improved lifetime which is Touschek dominated at the MLS. A possible solution to meet this demand is to lengthen the electron bunches. By installing a Robinson Wiggler (RW), damping effects can be transferred from the longitudinal to the horizontal plane ,*, thereby increasing the energy spread and reducing the horizontal emittance. By varying the energy spread, the bunch length can be increased and thus the scattering rate decreased, resulting in an improved lifetime. According to preliminary estimations a considerable increase in lifetime seems achievable, while preserving the source size. R. Klein et al., Phys. Rev. ST-AB 11, 110701, 2008 K. W. Robinson, Radiation effects in circular electron accelerators, 1958. * H. Abualrob et al., MOPPP062, IPAC2012, New Orleans, 2012
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRO028
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WEPRI008	First Cavity Design Studies for the BESSY-VSR Upgrade Proposal	2493
	A. Neumann, A. Burrill, P. Goslawski, A. Jankowiak, J. Knobloch, M. Ries, M. Ruprecht, A.V. Vélez, G. Wüstefeld HZB, Berlin, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung and Land Berlin Recently HZB proposed an upgrade of the 3rd generation synchrotron light source BESSY II allowing simultanous long and short pulse operation. For this scheme to work superconducting higher harmonic cavities of the fundamental 500 MHz at two frequencies need to be installed in the BESSY II storage ring. Given an appropiate choice of the higher harmonics the resulting gradient leads to a beating effect of the effective longitudinal focussing voltage at the stable fix points resulting in different bunch lengths in subsequent buckets. This project places stringent requirements on the cavity performance, as high accelerating fields, excellent HOM damping capabilities and high reliability as they will operate in a 300 mA 24/7 user facility. In this paper we describe the requirements for the cavity design and first designs steps. G. Wüstefeldt et al., Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring, Proc. of IPAC'11, San Sebástian, Spain
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI008
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THPME097	Schottky Diode Detectors for Monitoring Coherent THz Synchrotron Radiation Pulses	3465
	A. Semenov, H.-W. Hübers, A. Pohl DLR, Berlin, Germany O. Cojocari, M. Sobornytskyy ACST GmbH, Hanau, Germany A. Hoehl, R. Müller PTB, Berlin, Germany M. Ries, G. Wüstefeld HZB, Berlin, Germany
	Coherent synchrotron radiation (CSR) in the terahertz frequency range is a powerful tool for the diagnostics of the electron-beam relying on the fact that the emission spectrum of THz CSR depends on the shape of the electron bunch from which the radiation is emitted. Among available direct THz detectors only superconducting microbolometers and Schottky diodes are capable to resolve single CSR pulses. Here we present recent photoresponse measurements of CSR with a quasioptical zero-bias Schottky diode detector which was produced at ACST GmbH. The rise-time of the recorded real-time transient was limited to approximately 20 ps by the 18-GHz bandwidth of interconnecting cables. Non-saturated responsivity of the detector, that is the amplitude of the voltage transient referred to the total CSR pulse energy in the detector quasioptical mode, was approximately 1.5 mV/fJ. The dynamic range of the detector spans almost three orders of magnitude from 3 fJ to 1 pJ. The intrinsic jitter of the detector was less than 2 ps thus not affecting the effective time resolution and allowing us to measure the arrival-time jitter of CSR pulses for different settings of the storage ring parameters.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME097
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Paper

Title

Page

The Low-alpha Lattice and Bunch Length Limits at BESSY-VSR

216

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

Funding: Work supported by German Bundesministerium für Bildung und Forschung and Land Berlin.
An upgrade of the BESSY II ring to a Variable bunch length Storage Ring BESSY^VSR has been recently proposed *, by introducing strongly focusing superconducting cavities. This will allow to store simultaneously long and short bunches. In the regular user optics, bunch lengths of 15 ps (rms) and down to 1.5 ps (rms) are expected. Bunches as short as 300 fs (rms), close to the bunch length limit, and a ring current of 3.5 mA at the bunch bursting threshold can be provided by using a modified low-alpha optics. This presentation will discuss the properties of the low-alpha optics and intrinsic bunch length limits, given by coupling effects of the longitudinal and horizontal plane.
* G. Wüstefeld, A. Jankowiak, J. Knobloch, M.Ries, "Simultaneous Long and Short Electron Bunches in the BESSYII Storage Ring", Proceedings of IPAC2011, San Sebastian, Spain.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO058

Export •

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

TUPRI043

Analysis of Coupled Bunch Instabilities in BESSY-VSR

1659

M. Ruprecht, P. Goslawski, A. Jankowiak, M. Ries, A. Schälicke, G. Wüstefeld
HZB, Berlin, Germany
T. Weis
DELTA, Dortmund, Germany

BESSY-VSR, a scheme where 1.5 ps and 15 ps long bunches (rms) can be stored simultaneously in the BESSY II storage ring has recently been proposed*. The strong longitudinal bunch focusing is achieved by superconducting high gradient RF cavities. This paper presents investigations of coupled bunch instabilities driven by HOMs of superconducting multi cell cavities in BESSY-VSR. Analytical calculations and tracking simulations in time domain are performed in the longitudinal and the transverse planes and factors that influence the threshold currents are being discussed. Suitable candidates of cavities which are presently available or in the phase of design are compared with respect to their instability thresholds.
* G. Wüstefeld, A. Jankowiak, J. Knobloch, M. Ries, Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring, Proceedings of IPAC2011, San Sebastián, Spain

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI043

Export •

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

WEPRO028

A Robinson Wiggler Proposal for the Metrology Light Source

2001

T. Goetsch, J. Feikes, M. Ries, G. Wüstefeld
HZB, Berlin, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung and Land Berlin.
The Metrology Light Source (MLS), situated in Berlin (Germany) is owned by the Physikalisch-Technische Bundesanstalt and was built / is operated by the Helmholtz-Zentrum Berlin. It is an electron storage ring operating from 10⁵ MeV to 630 MeV. The MLS serves as the national primary source standard from the near infrared to the extreme ultraviolet spectral region *. Users of synchrotron radiation demand an improved lifetime which is Touschek dominated at the MLS. A possible solution to meet this demand is to lengthen the electron bunches. By installing a Robinson Wiggler (RW), damping effects can be transferred from the longitudinal to the horizontal plane **,***, thereby increasing the energy spread and reducing the horizontal emittance. By varying the energy spread, the bunch length can be increased and thus the scattering rate decreased, resulting in an improved lifetime. According to preliminary estimations a considerable increase in lifetime seems achievable, while preserving the source size.
* R. Klein et al., Phys. Rev. ST-AB 11, 110701, 2008
** K. W. Robinson, Radiation effects in circular electron accelerators, 1958.
*** H. Abualrob et al., MOPPP062, IPAC2012, New Orleans, 2012

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRO028

Export •

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

WEPRI008

First Cavity Design Studies for the BESSY-VSR Upgrade Proposal

2493

A. Neumann, A. Burrill, P. Goslawski, A. Jankowiak, J. Knobloch, M. Ries, M. Ruprecht, A.V. Vélez, G. Wüstefeld
HZB, Berlin, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung and Land Berlin
Recently HZB proposed an upgrade of the 3rd generation synchrotron light source BESSY II allowing simultanous long and short pulse operation*. For this scheme to work superconducting higher harmonic cavities of the fundamental 500 MHz at two frequencies need to be installed in the BESSY II storage ring. Given an appropiate choice of the higher harmonics the resulting gradient leads to a beating effect of the effective longitudinal focussing voltage at the stable fix points resulting in different bunch lengths in subsequent buckets. This project places stringent requirements on the cavity performance, as high accelerating fields, excellent HOM damping capabilities and high reliability as they will operate in a 300 mA 24/7 user facility. In this paper we describe the requirements for the cavity design and first designs steps.
* G. Wüstefeldt et al., Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring, Proc. of IPAC'11, San Sebástian, Spain

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI008

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

THPME097

Schottky Diode Detectors for Monitoring Coherent THz Synchrotron Radiation Pulses

3465

A. Semenov, H.-W. Hübers, A. Pohl
DLR, Berlin, Germany
O. Cojocari, M. Sobornytskyy
ACST GmbH, Hanau, Germany
A. Hoehl, R. Müller
PTB, Berlin, Germany
M. Ries, G. Wüstefeld
HZB, Berlin, Germany

Coherent synchrotron radiation (CSR) in the terahertz frequency range is a powerful tool for the diagnostics of the electron-beam relying on the fact that the emission spectrum of THz CSR depends on the shape of the electron bunch from which the radiation is emitted. Among available direct THz detectors only superconducting microbolometers and Schottky diodes are capable to resolve single CSR pulses. Here we present recent photoresponse measurements of CSR with a quasioptical zero-bias Schottky diode detector which was produced at ACST GmbH. The rise-time of the recorded real-time transient was limited to approximately 20 ps by the 18-GHz bandwidth of interconnecting cables. Non-saturated responsivity of the detector, that is the amplitude of the voltage transient referred to the total CSR pulse energy in the detector quasioptical mode, was approximately 1.5 mV/fJ. The dynamic range of the detector spans almost three orders of magnitude from 3 fJ to 1 pJ. The intrinsic jitter of the detector was less than 2 ps thus not affecting the effective time resolution and allowing us to measure the arrival-time jitter of CSR pulses for different settings of the storage ring parameters.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME097

Export •

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