IPAC2018 - List of Authors (Popovic, B.K.)

Paper	Title	Page
WEPMF089	Measurements of Electromagnetic Properties of Ferrites as a Function of Frequency and Temperature	2592
	A. Chmielinska, M.J. Barnes, F. Caspers, B.K. Popovic, C. Vollinger CERN, Geneva, Switzerland
	Fast kicker magnets are used to inject beam into and extract beam out of the CERN accelerator rings. These kickers are often ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. The interaction of the beam with the resistive part of the longitudinal beam coupling impedance leads to power dissipation and heating of different elements in the accelerator ring. In particular, power deposition in the kicker magnets can be a limitation: if the temperature of the ferrite yoke exceeds the Curie temperature, the beam will not be properly deflected. In addition, the imaginary portion of the beam coupling impedance contributes to beam instabilities. A good knowledge of electromagnetic properties of materials up to GHz frequency range is essential for a correct impedance evaluation. This paper presents the results of transmission line measurements of complex initial permeability and permittivity for different ferrite types. We present an approach for deriving electromagnetic properties as a function of both frequency and temperature; this information is required for simulating ferrite behaviour under realistic operating conditions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF089
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THPAF051	Beam Impedance Evaluation for CERN PS Gate Valves by Simulation and Benchmark Measurement	3080
	B.K. Popovic, C. Vollinger CERN, Geneva, Switzerland
	The CERN High Luminosity LHC project calls for a doubling of beam intensity which requires a clear identification of possible longitudinal instability sources in the injector chain. This requirement yields the need to further improve the longitudinal impedance model for the Proton Synchrotron (PS). In this impedance model it is necessary to include not only obvious impedance sources, such as RF cavities and kickers but also seemingly innocuous elements like certain vacuum components. Individually these vacuum elements would give only a small impedance contribution, however, due to the large number of these elements in the machine, their resultant combined impedances impact the overall impedance budget. This paper presents the electromagnetic simulation analysis of the PS sector gate valves along with EM measurements confirming the simulation model. These measurements are especially crucial in this case since no complete mechanical model or drawings are available and assumptions had to be made regarding its interior mechanical structure.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF051
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THPAF052	Impedance Analysis of New PS Internal Dump Design	3083
	B.K. Popovic, L. Teofili, C. Vollinger CERN, Geneva, Switzerland
	The High Luminosity Large Hadron Collider (HL-LHC) project at CERN calls for increasing beam intensity in the injector chain. In the Proton Synchrotron (PS), a pre-injector of the LHC, these intensities can result in beam instabilities and potential RF heating of machine components, such that impedance mitigation measures are required. To study these intensity effects, the PS impedance model has been developed and is continuously updated. Each new machine element that is to be added into the accelerator requires an impedance study to minimize its contribution with respect to the machine's overall impedance budget. In such a context, this paper presents the impedance analysis of the new design of the internal beam dump for the PS, showing the design process required to reduce the impedance contribution of this element. Furthermore, the impedance analysis of the currently installed beam dump is analysed in order to compare the impedance contributions of the two designs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF052
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THPAF063	Identification of Imperfections in Impedance Shields on the SPS-QF Flanges via Non-Intrusive Measurements	3119
	A. Farricker, P. Kramer, B.K. Popovic, E. Sunar, C. Vollinger, M. Wendt CERN, Geneva, Switzerland
	In order to achieve the highest beam intensities possible in the LHC the highest quality beam possible has to be supplied by the injector chain. The Super Proton Synchrotron (SPS) at CERN is the last accelerator in the injector chain of the LHC. One factor that is currently known to limit the intensity of the beam for injection to the LHC, is the longitudinal beam-coupling impedance in the SPS. One known source of multi-bunch instability is the vacuum flanges and campaigns to mechanically shield this source were completed in the year 2000. However, today it cannot be excluded that some of these shields may have partial or indeed full failures. Since these flanges are next to a QF magnet and are in most cases connected to a BPH (Beam Position Monitor Horizontal), it is possible to carry out via the BPH an in-situ measurement of the effectiveness of the shields. In this paper we present a methodology as well as measurement results taken with this non-intrusive in-situ method. From measurements, it is possible to identify if the flanges are without any impedance shield, equipped with either a fully functioning shield or a shield exhibiting non-ideal properties.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF063
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Measurements of Electromagnetic Properties of Ferrites as a Function of Frequency and Temperature

2592

A. Chmielinska, M.J. Barnes, F. Caspers, B.K. Popovic, C. Vollinger
CERN, Geneva, Switzerland

Fast kicker magnets are used to inject beam into and extract beam out of the CERN accelerator rings. These kickers are often ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. The interaction of the beam with the resistive part of the longitudinal beam coupling impedance leads to power dissipation and heating of different elements in the accelerator ring. In particular, power deposition in the kicker magnets can be a limitation: if the temperature of the ferrite yoke exceeds the Curie temperature, the beam will not be properly deflected. In addition, the imaginary portion of the beam coupling impedance contributes to beam instabilities. A good knowledge of electromagnetic properties of materials up to GHz frequency range is essential for a correct impedance evaluation. This paper presents the results of transmission line measurements of complex initial permeability and permittivity for different ferrite types. We present an approach for deriving electromagnetic properties as a function of both frequency and temperature; this information is required for simulating ferrite behaviour under realistic operating conditions.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF089

Export •

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

THPAF051

Beam Impedance Evaluation for CERN PS Gate Valves by Simulation and Benchmark Measurement

3080

B.K. Popovic, C. Vollinger
CERN, Geneva, Switzerland

The CERN High Luminosity LHC project calls for a doubling of beam intensity which requires a clear identification of possible longitudinal instability sources in the injector chain. This requirement yields the need to further improve the longitudinal impedance model for the Proton Synchrotron (PS). In this impedance model it is necessary to include not only obvious impedance sources, such as RF cavities and kickers but also seemingly innocuous elements like certain vacuum components. Individually these vacuum elements would give only a small impedance contribution, however, due to the large number of these elements in the machine, their resultant combined impedances impact the overall impedance budget. This paper presents the electromagnetic simulation analysis of the PS sector gate valves along with EM measurements confirming the simulation model. These measurements are especially crucial in this case since no complete mechanical model or drawings are available and assumptions had to be made regarding its interior mechanical structure.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF051

Export •

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

THPAF052

Impedance Analysis of New PS Internal Dump Design

3083

B.K. Popovic, L. Teofili, C. Vollinger
CERN, Geneva, Switzerland

The High Luminosity Large Hadron Collider (HL-LHC) project at CERN calls for increasing beam intensity in the injector chain. In the Proton Synchrotron (PS), a pre-injector of the LHC, these intensities can result in beam instabilities and potential RF heating of machine components, such that impedance mitigation measures are required. To study these intensity effects, the PS impedance model has been developed and is continuously updated. Each new machine element that is to be added into the accelerator requires an impedance study to minimize its contribution with respect to the machine's overall impedance budget. In such a context, this paper presents the impedance analysis of the new design of the internal beam dump for the PS, showing the design process required to reduce the impedance contribution of this element. Furthermore, the impedance analysis of the currently installed beam dump is analysed in order to compare the impedance contributions of the two designs.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF052

Export •

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

THPAF063

Identification of Imperfections in Impedance Shields on the SPS-QF Flanges via Non-Intrusive Measurements

3119

A. Farricker, P. Kramer, B.K. Popovic, E. Sunar, C. Vollinger, M. Wendt
CERN, Geneva, Switzerland

In order to achieve the highest beam intensities possible in the LHC the highest quality beam possible has to be supplied by the injector chain. The Super Proton Synchrotron (SPS) at CERN is the last accelerator in the injector chain of the LHC. One factor that is currently known to limit the intensity of the beam for injection to the LHC, is the longitudinal beam-coupling impedance in the SPS. One known source of multi-bunch instability is the vacuum flanges and campaigns to mechanically shield this source were completed in the year 2000. However, today it cannot be excluded that some of these shields may have partial or indeed full failures. Since these flanges are next to a QF magnet and are in most cases connected to a BPH (Beam Position Monitor Horizontal), it is possible to carry out via the BPH an in-situ measurement of the effectiveness of the shields. In this paper we present a methodology as well as measurement results taken with this non-intrusive in-situ method. From measurements, it is possible to identify if the flanges are without any impedance shield, equipped with either a fully functioning shield or a shield exhibiting non-ideal properties.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF063

Export •

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