IPAC2013 - List of Authors (Argyropoulos, T.)

Paper

Title

Page

Experimental Studies for Future LHC Beams in the SPS

1652

H. Bartosik, T. Argyropoulos, T. Bohl, S. Cettour-Cave, J.F. Esteban Müller, W. Höfle, G. Iadarola, Y. Papaphilippou, G. Rumolo, B. Salvant, F. Schmidt, E.N. Shaposhnikova, H. Timko
CERN, Geneva, Switzerland
A.Y. Molodozhentsev
KEK, Ibaraki, Japan

The High Luminosity LHC (HL-LHC) project requires significantly higher beam intensity than presently accessible in the LHC injector chain. The aim of the LHC injectors upgrade project (LIU) is to prepare the CERN accelerators for the future needs of the LHC. Therefore a series of machine studies with high brightness beams were performed, assessing the present performance reach and identifying remaining limitations. Of particular concern are beam loading and longitudinal instabilities at high energy, space charge for beams with 50ns bunch spacing and electron cloud effects for beams with 25ns bunch spacing. This paper provides a summary of the performed studies, that have been possible thanks to the implementation of the SPS low gamma-transition optics.

TUPWA039

Identification of the SPS Impedance at 1.4 GHz

1793

T. Argyropoulos, T. Bohl, H. Damerau, J.F. Esteban Müller, E.N. Shaposhnikova, H. Timko
CERN, Geneva, Switzerland

In the SPS spectrum measurements of very long single bunches were used in the past to identify sources of longitudinal microwave instability. Shielding of the identified objects significantly improved the beam stability. However, longitudinal instabilities are still one of the limitations for high intensity LHC beams in the SPS. Recently the same measurement technique was used again, revealing a strong high frequency resonance. During the slow de-bunching with the RF switched off, the presence of different resonant impedances leads to a line density modulation at the resonant frequencies. Longitudinal profiles of bunches of various intensities were acquired. For sufficiently high intensities their spectra show a fast growing and strong modulation at 1.4 GHz. Measurements using two transverse optics with different transition energy are compared. Reproducing the measurements with numerical simulations, including the known SPS longitudinal impedances, allowed the parameter range of this unknown source to be determined. Possible candidates as impedance sources in the SPS ring are investigated.

TUPWA040

Loss of Landau Damping for Inductive Impedance in a Double RF System

1796

T. Argyropoulos, E.N. Shaposhnikova
CERN, Geneva, Switzerland
A.V. Burov
Fermilab, Batavia, USA

In this paper the thresholds of the loss of Landau damping due to the presence of inductive impedance in a single and double harmonic RF systems are determined, both from calculations and particle simulations. High harmonic RF system, operating in bunch lengthening mode is used in many accelerators with space charge or inductive impedance to reduce the peak line density or stabilize the beam. An analytical approach, based on emerging of the discrete Van Kampen modes, shows that improved stability in a double RF system can be achieved only below some critical value of longitudinal emittance. Above this threshold, a phase shift of more than 15 degrees between the two RF components is proven to stabilize the bunch. These results, confirmed also by particle simulations, are able to explain now observations during the ppbar operation of the SPS. The thresholds in bunch shortening mode as well as in a single RF case are compared with this regime.

TUPWA049

Short High-Intensity Bunches for Plasma Wakefield Experiment AWAKE in the CERN SPS

1820

H. Timko, T. Argyropoulos, H. Bartosik, T. Bohl, J.F. Esteban Müller, E.N. Shaposhnikova
CERN, Geneva, Switzerland
A.V. Petrenko
BINP SB RAS, Novosibirsk, Russia

Obtaining the shortest possible bunch length in combination with the smallest transverse emittances and highest bunch intensity – this is the wish list of the proton-bunch driven, plasma wakefield acceleration experiment AWAKE currently under feasibility study at CERN. A few measurement sessions were conducted to determine the achievable bunch properties and their reproducibility. To obtain a short bunch length, the bunches were rotated in longitudinal phase space using the maximum available RF voltage prior to extraction. Measurements were carried out in two optics with different transition energies. The main performance limitation is longitudinal beam instability that develops during the acceleration ramp. With lower transition energy, beam stability is improved, but the bucket area is smaller for the same voltage. Based on the results obtained, we shall discuss the choice of optics, the impact of longitudinal instabilities, the importance of reproducibility, as well as options for improving the bunch parameters.

WEPEA053

Progress with the Upgrade of the SPS for the HL-LHC Era

2624

B. Goddard, T. Argyropoulos, W. Bartmann, H. Bartosik, T. Bohl, F. Caspers, K. Cornelis, H. Damerau, L.N. Drøsdal, L. Ducimetière, J.F. Esteban Müller, R. Garoby, M. Gourber-Pace, W. Höfle, G. Iadarola, L.K. Jensen, V. Kain, R. Losito, M. Meddahi, A. Mereghetti, V. Mertens, Ö. Mete, E. Montesinos, Y. Papaphilippou, G. Rumolo, B. Salvant, E.N. Shaposhnikova, M. Taborelli, H. Timko, F.M. Velotti
CERN, Geneva, Switzerland
E. Gianfelice-Wendt
Fermilab, Batavia, USA

The demanding beam performance requirements of the HL-LHC project translate into a set of requirements and upgrade paths for the LHC injector complex. In this paper the performance requirements for the SPS and the known limitations are reviewed in the light of the 2012 operational experience. The various SPS upgrades in progress and still under consideration are described, in addition to the machine studies and simulations performed in 2012. The expected machine performance reach is estimated on the basis of the present knowledge, and the remaining decisions that still need to be made concerning upgrade options are detailed.

THOBB102

Beam Coupling Impedance Localization Technique Validation and Measurements in the CERN Machines

3106

N. Biancacci, G. Arduini, T. Argyropoulos, H. Bartosik, R. Calaga, K. Cornelis, S.S. Gilardoni, N. Mounet, E. Métral, Y. Papaphilippou, S. Persichelli, G. Rumolo, B. Salvant, G. Sterbini, R. Tomás, R. Wasef
CERN, Geneva, Switzerland
M. Migliorati, L. Palumbo
URLS, Rome, Italy

The beam coupling impedance could lead to limitations in beam brightness and quality, and therefore it needs accurate quantification and continuous monitoring in order to detect and mitigate high impedance sources. In the CERN machines, for example, kickers and collimators are expected to be the main contributors to the total imaginary part of the transverse impedance. In order to detect the other sources, a beam based measurement was developed: from the variation of betatron phase beating with intensity, it is possible to detect the locations of main impedance sources. In this work we present the application of the method with beam measurements in the CERN PS, SPS and LHC.

Slides THOBB102 [7.224 MB]

THPWO080

Operational Performance of the LHC Proton Beams with the SPS Low Transition Energy Optics

3945

Y. Papaphilippou, G. Arduini, T. Argyropoulos, W. Bartmann, H. Bartosik, T. Bohl, C. Bracco, S. Cettour-Cave, K. Cornelis, L.N. Drøsdal, J.F. Esteban Müller, B. Goddard, A. Guerrero, W. Höfle, V. Kain, G. Rumolo, B. Salvant, E.N. Shaposhnikova, H. Timko, D. Valuch, G. Vanbavinckhove, J. Wenninger
CERN, Geneva, Switzerland
E. Gianfelice-Wendt
Fermilab, Batavia, USA

An optics in the SPS with lower integer tunes (20 versus 26) was proposed and introduced in machine studies since 2010, as a measure for increasing transverse and longitudinal instability thresholds, especially at low energy, for the LHC proton beams. After two years of machine studies and careful optimisation, the new “Q20” optics became operational in September 2012 and steadily delivered beam to the LHC until the end of the run. This paper reviews the operational performance of the Q20 optics with respect to transverse and longitudinal beam characteristics in the SPS, enabling high brightness beams injected into the LHC. Aspects of longitudinal beam stability, transmission, high-energy orbit control and beam transfer are discussed.

Paper	Title	Page
TUPME034	Experimental Studies for Future LHC Beams in the SPS	1652
	H. Bartosik, T. Argyropoulos, T. Bohl, S. Cettour-Cave, J.F. Esteban Müller, W. Höfle, G. Iadarola, Y. Papaphilippou, G. Rumolo, B. Salvant, F. Schmidt, E.N. Shaposhnikova, H. Timko CERN, Geneva, Switzerland A.Y. Molodozhentsev KEK, Ibaraki, Japan
	The High Luminosity LHC (HL-LHC) project requires significantly higher beam intensity than presently accessible in the LHC injector chain. The aim of the LHC injectors upgrade project (LIU) is to prepare the CERN accelerators for the future needs of the LHC. Therefore a series of machine studies with high brightness beams were performed, assessing the present performance reach and identifying remaining limitations. Of particular concern are beam loading and longitudinal instabilities at high energy, space charge for beams with 50ns bunch spacing and electron cloud effects for beams with 25ns bunch spacing. This paper provides a summary of the performed studies, that have been possible thanks to the implementation of the SPS low gamma-transition optics.

TUPWA039	Identification of the SPS Impedance at 1.4 GHz	1793
	T. Argyropoulos, T. Bohl, H. Damerau, J.F. Esteban Müller, E.N. Shaposhnikova, H. Timko CERN, Geneva, Switzerland
	In the SPS spectrum measurements of very long single bunches were used in the past to identify sources of longitudinal microwave instability. Shielding of the identified objects significantly improved the beam stability. However, longitudinal instabilities are still one of the limitations for high intensity LHC beams in the SPS. Recently the same measurement technique was used again, revealing a strong high frequency resonance. During the slow de-bunching with the RF switched off, the presence of different resonant impedances leads to a line density modulation at the resonant frequencies. Longitudinal profiles of bunches of various intensities were acquired. For sufficiently high intensities their spectra show a fast growing and strong modulation at 1.4 GHz. Measurements using two transverse optics with different transition energy are compared. Reproducing the measurements with numerical simulations, including the known SPS longitudinal impedances, allowed the parameter range of this unknown source to be determined. Possible candidates as impedance sources in the SPS ring are investigated.

TUPWA040	Loss of Landau Damping for Inductive Impedance in a Double RF System	1796
	T. Argyropoulos, E.N. Shaposhnikova CERN, Geneva, Switzerland A.V. Burov Fermilab, Batavia, USA
	In this paper the thresholds of the loss of Landau damping due to the presence of inductive impedance in a single and double harmonic RF systems are determined, both from calculations and particle simulations. High harmonic RF system, operating in bunch lengthening mode is used in many accelerators with space charge or inductive impedance to reduce the peak line density or stabilize the beam. An analytical approach, based on emerging of the discrete Van Kampen modes, shows that improved stability in a double RF system can be achieved only below some critical value of longitudinal emittance. Above this threshold, a phase shift of more than 15 degrees between the two RF components is proven to stabilize the bunch. These results, confirmed also by particle simulations, are able to explain now observations during the ppbar operation of the SPS. The thresholds in bunch shortening mode as well as in a single RF case are compared with this regime.

TUPWA049	Short High-Intensity Bunches for Plasma Wakefield Experiment AWAKE in the CERN SPS	1820
	H. Timko, T. Argyropoulos, H. Bartosik, T. Bohl, J.F. Esteban Müller, E.N. Shaposhnikova CERN, Geneva, Switzerland A.V. Petrenko BINP SB RAS, Novosibirsk, Russia
	Obtaining the shortest possible bunch length in combination with the smallest transverse emittances and highest bunch intensity – this is the wish list of the proton-bunch driven, plasma wakefield acceleration experiment AWAKE currently under feasibility study at CERN. A few measurement sessions were conducted to determine the achievable bunch properties and their reproducibility. To obtain a short bunch length, the bunches were rotated in longitudinal phase space using the maximum available RF voltage prior to extraction. Measurements were carried out in two optics with different transition energies. The main performance limitation is longitudinal beam instability that develops during the acceleration ramp. With lower transition energy, beam stability is improved, but the bucket area is smaller for the same voltage. Based on the results obtained, we shall discuss the choice of optics, the impact of longitudinal instabilities, the importance of reproducibility, as well as options for improving the bunch parameters.

WEPEA053	Progress with the Upgrade of the SPS for the HL-LHC Era	2624
	B. Goddard, T. Argyropoulos, W. Bartmann, H. Bartosik, T. Bohl, F. Caspers, K. Cornelis, H. Damerau, L.N. Drøsdal, L. Ducimetière, J.F. Esteban Müller, R. Garoby, M. Gourber-Pace, W. Höfle, G. Iadarola, L.K. Jensen, V. Kain, R. Losito, M. Meddahi, A. Mereghetti, V. Mertens, Ö. Mete, E. Montesinos, Y. Papaphilippou, G. Rumolo, B. Salvant, E.N. Shaposhnikova, M. Taborelli, H. Timko, F.M. Velotti CERN, Geneva, Switzerland E. Gianfelice-Wendt Fermilab, Batavia, USA
	The demanding beam performance requirements of the HL-LHC project translate into a set of requirements and upgrade paths for the LHC injector complex. In this paper the performance requirements for the SPS and the known limitations are reviewed in the light of the 2012 operational experience. The various SPS upgrades in progress and still under consideration are described, in addition to the machine studies and simulations performed in 2012. The expected machine performance reach is estimated on the basis of the present knowledge, and the remaining decisions that still need to be made concerning upgrade options are detailed.

THOBB102	Beam Coupling Impedance Localization Technique Validation and Measurements in the CERN Machines	3106
	N. Biancacci, G. Arduini, T. Argyropoulos, H. Bartosik, R. Calaga, K. Cornelis, S.S. Gilardoni, N. Mounet, E. Métral, Y. Papaphilippou, S. Persichelli, G. Rumolo, B. Salvant, G. Sterbini, R. Tomás, R. Wasef CERN, Geneva, Switzerland M. Migliorati, L. Palumbo URLS, Rome, Italy
	The beam coupling impedance could lead to limitations in beam brightness and quality, and therefore it needs accurate quantification and continuous monitoring in order to detect and mitigate high impedance sources. In the CERN machines, for example, kickers and collimators are expected to be the main contributors to the total imaginary part of the transverse impedance. In order to detect the other sources, a beam based measurement was developed: from the variation of betatron phase beating with intensity, it is possible to detect the locations of main impedance sources. In this work we present the application of the method with beam measurements in the CERN PS, SPS and LHC.
	Slides THOBB102 [7.224 MB]

THPWO080	Operational Performance of the LHC Proton Beams with the SPS Low Transition Energy Optics	3945
	Y. Papaphilippou, G. Arduini, T. Argyropoulos, W. Bartmann, H. Bartosik, T. Bohl, C. Bracco, S. Cettour-Cave, K. Cornelis, L.N. Drøsdal, J.F. Esteban Müller, B. Goddard, A. Guerrero, W. Höfle, V. Kain, G. Rumolo, B. Salvant, E.N. Shaposhnikova, H. Timko, D. Valuch, G. Vanbavinckhove, J. Wenninger CERN, Geneva, Switzerland E. Gianfelice-Wendt Fermilab, Batavia, USA
	An optics in the SPS with lower integer tunes (20 versus 26) was proposed and introduced in machine studies since 2010, as a measure for increasing transverse and longitudinal instability thresholds, especially at low energy, for the LHC proton beams. After two years of machine studies and careful optimisation, the new “Q20” optics became operational in September 2012 and steadily delivered beam to the LHC until the end of the run. This paper reviews the operational performance of the Q20 optics with respect to transverse and longitudinal beam characteristics in the SPS, enabling high brightness beams injected into the LHC. Aspects of longitudinal beam stability, transmission, high-energy orbit control and beam transfer are discussed.