IPAC2016 - List of Authors (Migliorati, M.)

Paper	Title	Page
MOPOR014	Measurements of the CERN PS Longitudinal Resistive Coupling Impedance	626
	M. Migliorati, N. Biancacci, H. Damerau, G. Sterbini CERN, Geneva, Switzerland M. Migliorati University of Rome "La Sapienza", Rome, Italy M. Migliorati, L. Ventura INFN-Roma1, Rome, Italy S. Persichelli University of Rome La Sapienza, Rome, Italy
	The longitudinal coupling impedance of the CERN PS has been studied in the past years in order to better understand collective effects which could produce beam intensity limitations for the LHC Injectors Upgrade project. By measuring the incoherent quadrupole synchrotron frequency vs beam intensity, the inductive impedance was evaluated and compared with the impedance model obtained by taking into account the contribution of the most important machine devices. In this paper, we present the results of the measurements performed during a dedicated campaign, of the real part of the longitudinal coupling impedance by means of the synchronous phase shift vs beam intensity. The phase shift has been measured by using two different techniques: in one case, we injected in the machine two bunches, one used as a reference with constant intensity, and the second one changing its intensity; in the second case, more conventional, we measured the bunch position with respect to the RF signal of the 40 MHz cavities. The obtained dependence of the synchrotron phase with intensity is then related to the loss factor and the resistive coupling impedance, which is compared to the real part of the PS impedance model.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR014
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TUPOR010	Simulation of Instability at Transition Energy with a New Impedance Model for CERN PS	1674
	N. Wang IHEP, Beijing, People's Republic of China S. Aumon, N. Biancacci, M. Migliorati, G. Sterbini, N. Wang CERN, Geneva, Switzerland M. Migliorati INFN-Roma1, Rome, Italy S. Persichelli University of Rome La Sapienza, Rome, Italy
	Instabilities driven by the transverse impedance are proven to be one of the limitations for the high intensity reach of the CERN PS. Since several years, fast single bunch vertical instability at transition energy has been observed with the high intensity bunch serving the neu-tron Time-of-Flight facility (n-ToF). In order to better understand the instability mechanism, a dedicated meas-urement campaign took place. The results were compared with macro-particle simulations with PyHEADTAIL based on the new impedance model developed for the PS. Instability threshold and growth rate for different longitu-dinal emittances and beam intensities were studied.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR010
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TUPOR028	Excitation of Longitudinal Coupled-bunch Oscillations with the Wide-band Cavity in the CERN PS	1724
	L. Ventura, M. Migliorati INFN-Roma1, Rome, Italy H. Damerau, M. Migliorati, G. Sterbini CERN, Geneva, Switzerland M. Migliorati University of Rome "La Sapienza", Rome, Italy
	Longitudinal coupled-bunch oscillations in the CERN Proton Synchrotron have been studied in the past years and they have been recognized as one of the major challenges to reach the high brightness beam required by the High Luminosity LHC project. In the frame of the LHC Injectors Upgrade project in 2014 a new wide-band Finemet cavity has been installed in the Proton Synchrotron as a part of the coupled-bunch feedback system. To explore the functionality of the Finemet cavity during 2015 a dedicated measurement campaign has been performed. Coupled-bunch oscillations have been excited with the cavity around each harmonic of the revolution frequency with both a uniform and nominal filling pattern. In the following the measurements procedure and results are presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR028
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MOPOR012	Study of the Beam-Cavity Interaction in the PS 10 MHz RF System	618
	G. Favia, H. Damerau, M. Morvillo, C. Rossi CERN, Geneva, Switzerland M. Migliorati University of Rome "La Sapienza", Rome, Italy
	The eleven main accelerating cavities of the Proton Synchrotron (PS) at CERN consist of two ferrite-loaded coaxial λ/4 resonators each. Both resonators oscillate in phase, as their gaps are electrically connected by short bars. They are in addition magnetically coupled via the bias loop used for cavity tuning. The cavities are equipped with a wide-band feedback system, limiting the beam loading, and a further reduction of the beam induced voltage is achieved by relays which short-circuit each half-resonator gap when the cavity is not in use. Asymmetries of the beam induced voltage observed in the two half-cavities indicate that the coupling between the two resonators is not as tight as expected. The total cavity impedance coupling to the beam may be affected differently by the contributions of both resonators. A dedicated measurement campaign with high-intensity proton beam and numerical simulation have been performed to investigate the beam-cavity interaction. This paper reports the result of the study and the work aiming at the development of a model of the system, including the wide-band feedback, which reproduces this interaction.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR012
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Paper

Title

Page

Measurements of the CERN PS Longitudinal Resistive Coupling Impedance

626

M. Migliorati, N. Biancacci, H. Damerau, G. Sterbini
CERN, Geneva, Switzerland
M. Migliorati
University of Rome "La Sapienza", Rome, Italy
M. Migliorati, L. Ventura
INFN-Roma1, Rome, Italy
S. Persichelli
University of Rome La Sapienza, Rome, Italy

The longitudinal coupling impedance of the CERN PS has been studied in the past years in order to better understand collective effects which could produce beam intensity limitations for the LHC Injectors Upgrade project. By measuring the incoherent quadrupole synchrotron frequency vs beam intensity, the inductive impedance was evaluated and compared with the impedance model obtained by taking into account the contribution of the most important machine devices. In this paper, we present the results of the measurements performed during a dedicated campaign, of the real part of the longitudinal coupling impedance by means of the synchronous phase shift vs beam intensity. The phase shift has been measured by using two different techniques: in one case, we injected in the machine two bunches, one used as a reference with constant intensity, and the second one changing its intensity; in the second case, more conventional, we measured the bunch position with respect to the RF signal of the 40 MHz cavities. The obtained dependence of the synchrotron phase with intensity is then related to the loss factor and the resistive coupling impedance, which is compared to the real part of the PS impedance model.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR014

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

TUPOR010

Simulation of Instability at Transition Energy with a New Impedance Model for CERN PS

1674

N. Wang
IHEP, Beijing, People's Republic of China
S. Aumon, N. Biancacci, M. Migliorati, G. Sterbini, N. Wang
CERN, Geneva, Switzerland
M. Migliorati
INFN-Roma1, Rome, Italy
S. Persichelli
University of Rome La Sapienza, Rome, Italy

Instabilities driven by the transverse impedance are proven to be one of the limitations for the high intensity reach of the CERN PS. Since several years, fast single bunch vertical instability at transition energy has been observed with the high intensity bunch serving the neu-tron Time-of-Flight facility (n-ToF). In order to better understand the instability mechanism, a dedicated meas-urement campaign took place. The results were compared with macro-particle simulations with PyHEADTAIL based on the new impedance model developed for the PS. Instability threshold and growth rate for different longitu-dinal emittances and beam intensities were studied.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR010

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

TUPOR028

Excitation of Longitudinal Coupled-bunch Oscillations with the Wide-band Cavity in the CERN PS

1724

L. Ventura, M. Migliorati
INFN-Roma1, Rome, Italy
H. Damerau, M. Migliorati, G. Sterbini
CERN, Geneva, Switzerland
M. Migliorati
University of Rome "La Sapienza", Rome, Italy

Longitudinal coupled-bunch oscillations in the CERN Proton Synchrotron have been studied in the past years and they have been recognized as one of the major challenges to reach the high brightness beam required by the High Luminosity LHC project. In the frame of the LHC Injectors Upgrade project in 2014 a new wide-band Finemet cavity has been installed in the Proton Synchrotron as a part of the coupled-bunch feedback system. To explore the functionality of the Finemet cavity during 2015 a dedicated measurement campaign has been performed. Coupled-bunch oscillations have been excited with the cavity around each harmonic of the revolution frequency with both a uniform and nominal filling pattern. In the following the measurements procedure and results are presented.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR028

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

MOPOR012

Study of the Beam-Cavity Interaction in the PS 10 MHz RF System

618

G. Favia, H. Damerau, M. Morvillo, C. Rossi
CERN, Geneva, Switzerland
M. Migliorati
University of Rome "La Sapienza", Rome, Italy

The eleven main accelerating cavities of the Proton Synchrotron (PS) at CERN consist of two ferrite-loaded coaxial λ/4 resonators each. Both resonators oscillate in phase, as their gaps are electrically connected by short bars. They are in addition magnetically coupled via the bias loop used for cavity tuning. The cavities are equipped with a wide-band feedback system, limiting the beam loading, and a further reduction of the beam induced voltage is achieved by relays which short-circuit each half-resonator gap when the cavity is not in use. Asymmetries of the beam induced voltage observed in the two half-cavities indicate that the coupling between the two resonators is not as tight as expected. The total cavity impedance coupling to the beam may be affected differently by the contributions of both resonators. A dedicated measurement campaign with high-intensity proton beam and numerical simulation have been performed to investigate the beam-cavity interaction. This paper reports the result of the study and the work aiming at the development of a model of the system, including the wide-band feedback, which reproduces this interaction.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR012

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