IPAC2016 - List of Authors (Sterbini, G.)

Paper	Title	Page
MOPMR028	Emittance Characterisation of High Brightness Beams in the CERN PS	299
	G. Sterbini, J.F. Comblin, V. Forte, A. Guerrero, E. Piselli CERN, Geneva, Switzerland V. Forte Université Blaise Pascal, Clermont-Ferrand, France
	Measurements in the CERN Proton Synchrotron showed that achieving the required accuracy for the emittance characterisation of high brightness beams is challenging. Some of the present limits can be related to systematic errors in the wire scanner calibration or, for the horizontal emittance determination, in the assumptions adopted while deconvoluting the contribution of the longitudinal plane from the measured transverse profile. We present in this paper the results of a beam-based test of the wire scanner calibration and of a general numerical deconvolution algorithm to compute the betatronic profile starting from the measured ones. In addition to the bunch train average emittance, a bunch-by-bunch transverse emittance measurement would increase the potential to understand, optimise and monitor the beam performance. In 2015 the first PS bunch-by-bunch measurement chain was setup. The results are reported and discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR028
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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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THPMR043	Performance of Transverse Beam Splitting and Extraction at the CERN Proton Synchrotron in the Framework of Multi-turn Extraction	3492
	G. Sterbini, J.C.C.M. Borburgh, S. Damjanovic, S.S. Gilardoni, M. Giovannozzi, C. Hernalsteens, M. Hourican, A. Huschauer, K. Kahle, G. Le Godec, O. Michels CERN, Geneva, Switzerland C. Hernalsteens EPFL, Lausanne, Switzerland
	Considerable progress has been made in 2015 in the setting up of the multi-turn extraction (MTE) in the CERN Proton Synchrotron (PS). A key ingredient in this novel extraction technique is the beam splitting in transverse phase space. This manipulation is based on adiabatic trapping in stable islands of transverse phase space and requires mastering a number of devices in the PS ring. In addition, an in-depth review of all fast extractions schemes in the PS had been required due to the development and installation of a dummy septum to shield the actual magnetic septum. In this paper, the current performance of the beam splitting and of the extraction including the shadowing effect is presented. Future lines of development will also be discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR043
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THPOR050	New Working Point for CERN Proton Synchrotron	3905
	F. Sperati, A. Beaumont, S.S. Gilardoni, D. Schoerling, M. Serluca, G. Sterbini CERN, Geneva, Switzerland
	The LHC High-luminosity project requests high brightness and intensity beams from the CERN Proton Synchrotron (PS). The generation of such beams is limited due to resonance effects at injection. The impact of resonances can be minimized by performing appropriate correction with dedicated magnets and by optimizing the tune working point. Currently the tune working point at injection is naturally set by the quadrupolar component generated by the one hundred combined function normal conducting magnets installed in the PS, and slightly corrected by low energy quadrupole magnets. In this paper, a study is presented exploiting the use of the available five auxiliary individually powered circuits to adjust the quadrupolar and higher-order multipole components for changing the tune integer at injection. Due to the non-linear contribution of each circuit to the magnetic field distribution a finite-element magnetic model was prepared to predict the required currents in the auxiliary coils. The magnetic model was benchmarked with magnetic measurements and then tested in the PS machine during dedicated machine development times.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR050
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Paper

Title

Page

Emittance Characterisation of High Brightness Beams in the CERN PS

299

G. Sterbini, J.F. Comblin, V. Forte, A. Guerrero, E. Piselli
CERN, Geneva, Switzerland
V. Forte
Université Blaise Pascal, Clermont-Ferrand, France

Measurements in the CERN Proton Synchrotron showed that achieving the required accuracy for the emittance characterisation of high brightness beams is challenging. Some of the present limits can be related to systematic errors in the wire scanner calibration or, for the horizontal emittance determination, in the assumptions adopted while deconvoluting the contribution of the longitudinal plane from the measured transverse profile. We present in this paper the results of a beam-based test of the wire scanner calibration and of a general numerical deconvolution algorithm to compute the betatronic profile starting from the measured ones. In addition to the bunch train average emittance, a bunch-by-bunch transverse emittance measurement would increase the potential to understand, optimise and monitor the beam performance. In 2015 the first PS bunch-by-bunch measurement chain was setup. The results are reported and discussed.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR028

Export •

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

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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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

Export •

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

Export •

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

THPMR043

Performance of Transverse Beam Splitting and Extraction at the CERN Proton Synchrotron in the Framework of Multi-turn Extraction

3492

G. Sterbini, J.C.C.M. Borburgh, S. Damjanovic, S.S. Gilardoni, M. Giovannozzi, C. Hernalsteens, M. Hourican, A. Huschauer, K. Kahle, G. Le Godec, O. Michels
CERN, Geneva, Switzerland
C. Hernalsteens
EPFL, Lausanne, Switzerland

Considerable progress has been made in 2015 in the setting up of the multi-turn extraction (MTE) in the CERN Proton Synchrotron (PS). A key ingredient in this novel extraction technique is the beam splitting in transverse phase space. This manipulation is based on adiabatic trapping in stable islands of transverse phase space and requires mastering a number of devices in the PS ring. In addition, an in-depth review of all fast extractions schemes in the PS had been required due to the development and installation of a dummy septum to shield the actual magnetic septum. In this paper, the current performance of the beam splitting and of the extraction including the shadowing effect is presented. Future lines of development will also be discussed.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR043

Export •

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

THPOR050

New Working Point for CERN Proton Synchrotron

3905

F. Sperati, A. Beaumont, S.S. Gilardoni, D. Schoerling, M. Serluca, G. Sterbini
CERN, Geneva, Switzerland

The LHC High-luminosity project requests high brightness and intensity beams from the CERN Proton Synchrotron (PS). The generation of such beams is limited due to resonance effects at injection. The impact of resonances can be minimized by performing appropriate correction with dedicated magnets and by optimizing the tune working point. Currently the tune working point at injection is naturally set by the quadrupolar component generated by the one hundred combined function normal conducting magnets installed in the PS, and slightly corrected by low energy quadrupole magnets. In this paper, a study is presented exploiting the use of the available five auxiliary individually powered circuits to adjust the quadrupolar and higher-order multipole components for changing the tune integer at injection. Due to the non-linear contribution of each circuit to the magnetic field distribution a finite-element magnetic model was prepared to predict the required currents in the auxiliary coils. The magnetic model was benchmarked with magnetic measurements and then tested in the PS machine during dedicated machine development times.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR050

Export •

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