IPAC2014 - List of Authors (Rumolo, G.)

Paper	Title	Page
TUPME026	TMCI Thresholds for LHC Single Bunches in the CERN-SPS and Comparison with Simulations	1407
	H. Bartosik, G. Iadarola, Y. Papaphilippou, G. Rumolo, B. Salvant, C. Zannini CERN, Geneva, Switzerland
	At the beginning of 2013 an extensive measurement campaign was carried out at the SPS in order to determine the Transverse Mode Coupling Instability thresholds of LHC-type bunches in a wide range of intensities and longitudinal emittances. The measurements were performed in two different configurations of machine optics (nominal and low gamma transition) with the goal to characterize the differences in behavior and performance. The purpose of this paper is to describe in detail the measurement procedure and results, as well as the comparison of the experimental data with HEADTAIL simulations based on the latest SPS impedance model. Beside the impedances of the resistive wall, the beam position monitors (BPMs), the RF cavities, and the flanges, an advanced model of the impedance of the kicker magnets is included, which are found to play a major role in the definition of the stability region of the LHC-type bunches in the two optics configurations studied.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME026
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TUPME027	Analysis of the Electron Cloud Observations with 25 ns Bunch Spacing at the LHC	1410
	G. Iadarola Naples University Federico II, Science and Technology Pole, Napoli, Italy G. Arduini, V. Baglin, D. Banfi, H. Bartosik, S.D. Claudet, C.O. Domínguez, J.F. Esteban Müller, G. Iadarola, T. Pieloni, G. Rumolo, E.N. Shaposhnikova, L.J. Tavian, C. Zannini, F. Zimmermann CERN, Geneva, Switzerland
	Electron Cloud (EC) effects have been identified as a major performance limitation for the Large Hadron Collider (LHC) when operating with the nominal bunch spacing of 25 ns. During the LHC Run 1 (2010 - 2013) the luminosity production mainly used beams with 50 ns spacing, while 25 ns beams were only employed for short periods in 2011 and 2012 for test purposes. On these occasions, observables such as pressure rise, heat load in the cold sections as well as clear signatures on bunch-by-bunch emittance blow up, particle loss and energy loss indicated the presence of an EC in a large portion of the LHC. The analysis of the recorded data, together with EC build up simulations, has led to a significant improvement of our understanding of the EC effect in the different components of the LHC. Studies were carried out both at injection energy (450 GeV) and at top energy (4 TeV) aiming at determining the energy dependence of the EC formation and its impact on the quality of the proton beam.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME027
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TUPRI052	Analysis of Single Bunch Measurements at the ALBA Storage Ring	1686
	T.F.G. Günzel, U. Iriso, F. Pérez CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain E. Koukovini-Platia, G. Rumolo CERN, Geneva, Switzerland
	Measurements of the vertical single bunch mode detuning and the TMCI threshold at zero chromaticity were carried out and their results were compared to the theoretical expectation. Around 65% of the found mode detuning can be explained by a developed transverse impedance model. A good bunch length parametrisation with current contributed essentially to this result. The analysis of single bunch measurements at non-zero chromaticity will also be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI052
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TUPRI057	Review of the Transverse Impedance Budget for the CLIC Damping Rings	1701
	E. Koukovini-Platia, G. Rumolo CERN, Geneva, Switzerland
	Single bunch instability thresholds and the associated coherent tune shifts have been evaluated in the transverse plane for the damping rings (DR) of the Compact Linear Collider (CLIC). A multi-kick version of the HEADTAIL code was used to study the instability thresholds in the case where different impedance contributions are taken into account such as the broad-band resonator model in combination with the resistive wall contribution from the arcs and the wigglers of the DR. Simulations performed for positive values of chromaticity showed that higher order bunch modes can be potentially dangerous for the beam stability.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI057
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TUPRI061	Power Loss Calculation in Separated and Common Beam Chambers of the LHC	1711
	C. Zannini, G. Iadarola, G. Rumolo CERN, Geneva, Switzerland G. Iadarola Naples University Federico II, Science and Technology Pole, Napoli, Italy
	The performance of 25 ns beams in the LHC is strongly limited by the electron cloud. To determine the amount electron cloud in the cold sections of the machine, it is very important to be able to disentangle the beam induced heating due to the beam coupling impedance from that attributable to electron cloud. This paper will focus on the calculation of the first contribution. First, the impedance model used for the calculation of the beam induced power loss is briefly discussed. Then, the methods for the calculation of the beam induced power loss in regions with one or two beams are also described. Finally, the calculated power loss is compared with the measured heat loads for both 25 and 50 ns beams in both the LHC arcs and in the inner triplets (ITs).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI061
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TUPRI063	Electromagnetic Simulations for Non-ultrarelativistic Beams and Application to the CERN Low Energy Machines	1718
	C. Zannini, N. Biancacci, T.L. Rijoff, G. Rumolo CERN, Geneva, Switzerland T.L. Rijoff TU Darmstadt, Darmstadt, Germany
	In the framework of the PS-Booster upgrade project an accurate impedance model is needed in order to determine the effect on the beam stability and assess the impact of the new devices to be installed in the machine. CST 3-D EM simulations are widely used to estimate the impedance contribution of the different devices along the CERN accelerator complex. Unlike the highly relativistic case, in which the reliability of the EM solver has been proved in many specific cases by comparing simulations with analytical results, the nonrelativistic case has been so far not yet benchmarked. In order to use systematically CST 3-D EM simulations for the PS-Booster, or even lower energy machines like the antiproton decelerator ELENA, a validation campaign has been carried out. The main complication to single out the beam coupling impedance, as resulting from the interaction of the beam with the surroundings, consisted of removing reliably the strong contribution of the direct space charge of the source bunch, which is included in the EM calculation. The simulation results were then benchmarked with the analytical results for the case of a PEC cylindrical tube and of a ferrite loaded kicker.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI063
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WEPME032	Detailed Investigation of the Low Energy Secondary Electron Yield of Technical Cu and its Relevance for LHC	2329
	R. Cimino, L.A. Gonzalez, A.L. Romano INFN/LNF, Frascati (Roma), Italy R. Cimino, G. Iadarola, G. Rumolo CERN, Geneva, Switzerland R. Larciprete ISM-CNR, Rome, Italy
	The detailed study of the Secondary Electron Yield (SEY) of technical Cu for very low electron landing energies (from 0 to 30 eV) is very important for electron cloud build up in high intensity accelerators and in many other fields of research. However, this question has been rarely addressed due to the intrinsic experimental complexity to control very low energy electrons. Furthermore, several results published in the past have been recently questioned for allegedly suffering from experimental systematics. In this paper, we critically review the experimental method used to study low energy SEY and define more precise energy regions, in which the experimental data can be considered valid. The new SEY curves are then fed into e-cloud simulation codes to address their impact for electron cloud predictions in the LHC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME032
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WEPME050	High Frequency Electromagnetic Characterization of NEG properties for the CLIC Damping Rings	2384
SUSPSNE103	use link to see paper's listing under its alternate paper code
	E. Koukovini-Platia, G. Rumolo, C. Zannini CERN, Geneva, Switzerland
	Coating materials will be used in the CLIC damping rings (DR) to suppress two-stream effects. In particular, NEG coating is necessary to suppress fast beam ion instabilities in the electron damping ring (EDR). The electromagnetic (EM) characterization of the material properties up to high frequencies is required for the impedance modeling of the CLIC DR components. The EM properties for frequencies of few GHz are determined with the waveguide method, based on a combination of experimental measurements of the complex transmission coefficient S21 and CST 3D EM simulations. The results obtained from a NEG coated copper (Cu) waveguide are presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME050
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THPRO082	Observation of Coherent Instability in the CERN PS Booster	3076
	M. McAteer, C. Carli, V. Forte, G. Rumolo, R. Tomás CERN, Geneva, Switzerland
	Funding: This project has been supported by a Marie Curie Early Initial Training Network Fellowship of the European Community's Seventh Framework Programme, contract number (PITN-GA-2011-289485-OPAC). At high intensities and at a certain working point an instability develops in the CERN PS Booster, and large coherent transverse oscillations and beam loss occur. The coherent oscillations and beam loss can be effectively controlled with the transverse damper system, but the origin of the instability is not well-understood. Recent measurements with the PSB's new trajectory measurement system have provided some insight into the nature of this instability, and these observations are presented here.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO082
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Paper

Title

Page

TMCI Thresholds for LHC Single Bunches in the CERN-SPS and Comparison with Simulations

1407

H. Bartosik, G. Iadarola, Y. Papaphilippou, G. Rumolo, B. Salvant, C. Zannini
CERN, Geneva, Switzerland

At the beginning of 2013 an extensive measurement campaign was carried out at the SPS in order to determine the Transverse Mode Coupling Instability thresholds of LHC-type bunches in a wide range of intensities and longitudinal emittances. The measurements were performed in two different configurations of machine optics (nominal and low gamma transition) with the goal to characterize the differences in behavior and performance. The purpose of this paper is to describe in detail the measurement procedure and results, as well as the comparison of the experimental data with HEADTAIL simulations based on the latest SPS impedance model. Beside the impedances of the resistive wall, the beam position monitors (BPMs), the RF cavities, and the flanges, an advanced model of the impedance of the kicker magnets is included, which are found to play a major role in the definition of the stability region of the LHC-type bunches in the two optics configurations studied.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME026

Export •

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

TUPME027

Analysis of the Electron Cloud Observations with 25 ns Bunch Spacing at the LHC

1410

G. Iadarola
Naples University Federico II, Science and Technology Pole, Napoli, Italy
G. Arduini, V. Baglin, D. Banfi, H. Bartosik, S.D. Claudet, C.O. Domínguez, J.F. Esteban Müller, G. Iadarola, T. Pieloni, G. Rumolo, E.N. Shaposhnikova, L.J. Tavian, C. Zannini, F. Zimmermann
CERN, Geneva, Switzerland

Electron Cloud (EC) effects have been identified as a major performance limitation for the Large Hadron Collider (LHC) when operating with the nominal bunch spacing of 25 ns. During the LHC Run 1 (2010 - 2013) the luminosity production mainly used beams with 50 ns spacing, while 25 ns beams were only employed for short periods in 2011 and 2012 for test purposes. On these occasions, observables such as pressure rise, heat load in the cold sections as well as clear signatures on bunch-by-bunch emittance blow up, particle loss and energy loss indicated the presence of an EC in a large portion of the LHC. The analysis of the recorded data, together with EC build up simulations, has led to a significant improvement of our understanding of the EC effect in the different components of the LHC. Studies were carried out both at injection energy (450 GeV) and at top energy (4 TeV) aiming at determining the energy dependence of the EC formation and its impact on the quality of the proton beam.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME027

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TUPRI052

Analysis of Single Bunch Measurements at the ALBA Storage Ring

1686

T.F.G. Günzel, U. Iriso, F. Pérez
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
E. Koukovini-Platia, G. Rumolo
CERN, Geneva, Switzerland

Measurements of the vertical single bunch mode detuning and the TMCI threshold at zero chromaticity were carried out and their results were compared to the theoretical expectation. Around 65% of the found mode detuning can be explained by a developed transverse impedance model. A good bunch length parametrisation with current contributed essentially to this result. The analysis of single bunch measurements at non-zero chromaticity will also be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI052

Export •

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

TUPRI057

Review of the Transverse Impedance Budget for the CLIC Damping Rings

1701

E. Koukovini-Platia, G. Rumolo
CERN, Geneva, Switzerland

Single bunch instability thresholds and the associated coherent tune shifts have been evaluated in the transverse plane for the damping rings (DR) of the Compact Linear Collider (CLIC). A multi-kick version of the HEADTAIL code was used to study the instability thresholds in the case where different impedance contributions are taken into account such as the broad-band resonator model in combination with the resistive wall contribution from the arcs and the wigglers of the DR. Simulations performed for positive values of chromaticity showed that higher order bunch modes can be potentially dangerous for the beam stability.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI057

Export •

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

TUPRI061

Power Loss Calculation in Separated and Common Beam Chambers of the LHC

1711

C. Zannini, G. Iadarola, G. Rumolo
CERN, Geneva, Switzerland
G. Iadarola
Naples University Federico II, Science and Technology Pole, Napoli, Italy

The performance of 25 ns beams in the LHC is strongly limited by the electron cloud. To determine the amount electron cloud in the cold sections of the machine, it is very important to be able to disentangle the beam induced heating due to the beam coupling impedance from that attributable to electron cloud. This paper will focus on the calculation of the first contribution. First, the impedance model used for the calculation of the beam induced power loss is briefly discussed. Then, the methods for the calculation of the beam induced power loss in regions with one or two beams are also described. Finally, the calculated power loss is compared with the measured heat loads for both 25 and 50 ns beams in both the LHC arcs and in the inner triplets (ITs).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI061

Export •

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

TUPRI063

Electromagnetic Simulations for Non-ultrarelativistic Beams and Application to the CERN Low Energy Machines

1718

C. Zannini, N. Biancacci, T.L. Rijoff, G. Rumolo
CERN, Geneva, Switzerland
T.L. Rijoff
TU Darmstadt, Darmstadt, Germany

In the framework of the PS-Booster upgrade project an accurate impedance model is needed in order to determine the effect on the beam stability and assess the impact of the new devices to be installed in the machine. CST 3-D EM simulations are widely used to estimate the impedance contribution of the different devices along the CERN accelerator complex. Unlike the highly relativistic case, in which the reliability of the EM solver has been proved in many specific cases by comparing simulations with analytical results, the nonrelativistic case has been so far not yet benchmarked. In order to use systematically CST 3-D EM simulations for the PS-Booster, or even lower energy machines like the antiproton decelerator ELENA, a validation campaign has been carried out. The main complication to single out the beam coupling impedance, as resulting from the interaction of the beam with the surroundings, consisted of removing reliably the strong contribution of the direct space charge of the source bunch, which is included in the EM calculation. The simulation results were then benchmarked with the analytical results for the case of a PEC cylindrical tube and of a ferrite loaded kicker.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI063

Export •

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

WEPME032

Detailed Investigation of the Low Energy Secondary Electron Yield of Technical Cu and its Relevance for LHC

2329

R. Cimino, L.A. Gonzalez, A.L. Romano
INFN/LNF, Frascati (Roma), Italy
R. Cimino, G. Iadarola, G. Rumolo
CERN, Geneva, Switzerland
R. Larciprete
ISM-CNR, Rome, Italy

The detailed study of the Secondary Electron Yield (SEY) of technical Cu for very low electron landing energies (from 0 to 30 eV) is very important for electron cloud build up in high intensity accelerators and in many other fields of research. However, this question has been rarely addressed due to the intrinsic experimental complexity to control very low energy electrons. Furthermore, several results published in the past have been recently questioned for allegedly suffering from experimental systematics. In this paper, we critically review the experimental method used to study low energy SEY and define more precise energy regions, in which the experimental data can be considered valid. The new SEY curves are then fed into e-cloud simulation codes to address their impact for electron cloud predictions in the LHC.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME032

Export •

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

WEPME050

High Frequency Electromagnetic Characterization of NEG properties for the CLIC Damping Rings

2384

SUSPSNE103

use link to see paper's listing under its alternate paper code

E. Koukovini-Platia, G. Rumolo, C. Zannini
CERN, Geneva, Switzerland

Coating materials will be used in the CLIC damping rings (DR) to suppress two-stream effects. In particular, NEG coating is necessary to suppress fast beam ion instabilities in the electron damping ring (EDR). The electromagnetic (EM) characterization of the material properties up to high frequencies is required for the impedance modeling of the CLIC DR components. The EM properties for frequencies of few GHz are determined with the waveguide method, based on a combination of experimental measurements of the complex transmission coefficient S21 and CST 3D EM simulations. The results obtained from a NEG coated copper (Cu) waveguide are presented in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME050

Export •

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

THPRO082

Observation of Coherent Instability in the CERN PS Booster

3076

M. McAteer, C. Carli, V. Forte, G. Rumolo, R. Tomás
CERN, Geneva, Switzerland

Funding: This project has been supported by a Marie Curie Early Initial Training Network Fellowship of the European Community's Seventh Framework Programme, contract number (PITN-GA-2011-289485-OPAC).
At high intensities and at a certain working point an instability develops in the CERN PS Booster, and large coherent transverse oscillations and beam loss occur. The coherent oscillations and beam loss can be effectively controlled with the transverse damper system, but the origin of the instability is not well-understood. Recent measurements with the PSB's new trajectory measurement system have provided some insight into the nature of this instability, and these observations are presented here.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO082

Export •

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