IPAC2018 - List of Authors (Bartosik, H.)

Paper	Title	Page
MOPMF061	Emittance Growth in Coast in the SPS at CERN	257
	F. Antoniou, H. Bartosik, T. Bohl, R. Calaga, L.R. Carver, J. Repond, G. Vandoni CERN, Geneva, Switzerland A. Alekou UMAN, Manchester, United Kingdom
	Funding: Research supported by the HL-LHC project. The HL-LHC prototype crab-cavities are installed in the CERN SPS, which will allow for a comprehensive beam test with high energy protons for the first time. As the time available for experimental beam dynamics studies with the crab cavities installed in the machine will be limited, a very good preparation is required. One of the main concerns is the induced emittance growth, driven by phase amplitude jitter in the crab cavities. In this respect, several machine development (MD) studies were performed during the past years to quantify and characterize the long term emittance evolution of proton beams in the SPS. In these proceedings, the experimental observations from past years are summarized and the MD studies from 2016 and 2017 are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF061
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TUPAF020	Performance of the CERN Low Energy Ion Ring (LEIR) with Xenon beams	705
	R. Alemany-Fernández, S.C.P. Albright, O. Andujar, M.E. Angoletta, J. Axensalva, H. Bartosik, G. Baud, N. Biancacci, M. Bozzolan, S. Cettour Cave, K. Cornelis, J. Dalla-Costa, M. Delrieux, A. Dworak, A. Findlay, F. Follin, A. Frassier, M. Gabriel, A. Guerrero, M. Haase, S. Hirlaender, S. Jensen, V. Kain, L.V. Kolbeck, Y. Le Borgne, D. Manglunki, O. Marqversen, S. Massot, D. Moreno Garcia, D.J.P. Nicosia, S. Pasinelli, L. Pereira, D. Perez, A. Rey, J.P. Ridewood, F. Roncarolo, Á. Saá Hernández, R. Scrivens, O.G. Sveen, G. Tranquille, E. Veyrunes CERN, Geneva, Switzerland
	In 2017 the CERN Low Energy Ion Ring demonstrated once more the feasibility of injecting, accumulating, cooling and accelerating a new nuclei, 129Xe39 . The operation of this new ion species started at the beginning of March with the start up of the xenon ion source and the Linac3. Ten weeks later the beam arrived to the Low Energy Ion Ring (LEIR) triggering the start of several weeks of beam commissioning in view of providing the injector complex with Xenon beams for different experiments and a series of machine development experiments in LEIR. Two types of beams were setup, the so called EARLY beam, with a single injection into LEIR from Linac3, and the NOMINAL beam with up to seven injections. 2017 was as well an interesting year for LEIR because several improvements in the control system of the accelerator and in the beam instrumentation were done in view of increasing the machine reliability. This paper summarises the beam commissioning phase and all the improvements carried out during 2017.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF020
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TUPAF021	Identification and Removal of SPS Aperture Limitations	709
	V. Kain, R. Alemany-Fernández, H. Bartosik, S. Cettour Cave, K. Cornelis, P. Cruikshank, J.A. Ferreira Somoza, B. Goddard, C. Pasquino CERN, Geneva, Switzerland
	The CERN SPS (Super Proton Synchrotron) serves as LHC injector and provides beam for the North Area fixed target experiments. Since the 2016 run automated local aperture scans have been performed with the main focus on the vertical plane where limitations typically arise due to the flat vacuum chambers in most SPS elements. For LHC beams the aperture limitations with the present low integer tune optics also occur at locations with large dispersion. Aperture measurements in the horizontal plane using a variety of techniques were performed and showed surprising results, which could partially explain the unexpected losses of high intensity LHC beams at the SPS flat bottom. In this paper, reference measurements from 2016 are compared with the ones taken at the beginning of the run in 2017. Several aperture restrictions in the vertical plane could be found and cured, and a potential systematic restriction in the horizontal plane has been identified. The results of the measurements and the origin of the restrictions are presented in this paper, and the outlook for partial mitigation is discussed.
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TUPAF022	Studies of a New Optics With Intermediate Transition Energy as Alternative for High Intensity LHC Beams in the CERN SPS	713
	M. Carlà, H. Bartosik, M.S. Beck, K.S.B. Li, M. Schenk CERN, Geneva, Switzerland M. Schenk EPFL, Lausanne, Switzerland
	The LHC injector upgrade project calls for a twofold increase in intensity of the SPS proton beam. In this paper, we present studies with a new SPS optics called Q22, which has a transition energy in between the one of the operationally used Q20 and Q26 optics. This new optics provides a compromise between the stability of Q20, due to the low transition energy, and the reduced requirements in terms of RF voltage and power in Q26. A non-linear effective model of Q22 has been extrapolated from beam based measurements and used to complement the SPS non-linear optics model. Furthermore the studies of the TMCI threshold performed so far are discussed.
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TUPAF024	Impedance and Instability Studies in LEIR with Xenon	720
	N. Biancacci, H. Bartosik, M. Gąsior, S. Hirlaender, V. Kain, T.E. Levens, E. Métral CERN, Geneva, Switzerland M. Migliorati Rome University La Sapienza, Roma, Italy
	In 2017, the LEIR accelerator has been operated with Xe³⁹⁺ beam for fixed target experiments in the SPS North Area. The different ion species, with respect to the usually operated Pb⁵⁴⁺, allowed for additional comparative measurements of tune shift versus intensity at injection energy both in coasting and bunched beams. The fast transverse instability observed for high accumulated intensities has been as well characterized and additional observations relevant to impedance have been collected from longitudinal Schottky signal and BTF measurements. The results of these measurements are summarised and compared to the currently developed machine impedance model.
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TUPAF034	LEIR Injection Efficiency Studies as a Function of the Beam Energy Distribution from Linac3	758
	S. Hirlaender, R. Alemany-Fernández, H. Bartosik, G. Bellodi, N. Biancacci, V. Kain, R. Scrivens CERN, Geneva, Switzerland
	High intensities in the CERN Low Energy Ion Ring (LEIR) are achieved using multi-turn injections from the pre-accelerator Linac3 combined with simultaneous stacking in momentum and transverse phase spaces. Up to seven consecutive 200 μs long, 200 ms spaced pulses are injected from Linac3 into LEIR by stacking each of them into the six-dimensional phase-space over 70 turns. An inclined septum magnet allows proper filling of the transverse phase-space plane, while longitudinal stacking requires momentum variation achieved by a shift of mean momentum over time provided by phase shifting a combination of 2 RF cavities at the exit of Linac3. The achievable maximum accumulated intensity depends strongly on the longitudinal beam quality of the injected beam. The longitudinal Schottky signal is used to measure the received energy distribution of the circulating beam which is then correlated with the obtained injection efficiency. This paper presents the experimental studies to understand and further improve the injection reliability and the longitudinal stacking.
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TUPAF035	Observations of SPS Slow-Extracted Spill Quality Degradation and Possible Improvements	761
	F.M. Velotti, H. Bartosik, K. Cornelis, M.A. Fraser, B. Goddard, S. Hirlaender, V. Kain, O. Michels, M. Pari CERN, Geneva, Switzerland
	The SPS delivers slow extracted proton and heavy ion spills of several seconds to the North Area fixed target experiments with a very high duty factor. Reduced machine reproducibility due to magnetic history and power supply ripples on the main circuits lead however to frequent degradation of the spill duty factor. In this paper, the measured effect of the SPS magnetic history on spill quality and principal machine parameters is presented. Another detailed measurement campaign was aimed at characterising the frequency content and response of the spill to noise on the main power supplies ripples. The main findings of this study will also be reported. Finally, simulations of possible improvements based on the data acquired are discussed, as well as an extrapolation to the possible spill quality after the implementation of the improvements.
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TUPAF036	Studies of the Injection and Cooling Efficiency in LEIR Using the Longitudinal Schottky Spectrum	765
	S. Hirlaender, R. Alemany-Fernández, H. Bartosik, N. Biancacci, V. Kain CERN, Geneva, Switzerland
	The CERN Low Energy Ion Ring (LEIR) has two main operational beams with their associated cycles, the so-called EARLY and the NOMINAL beam. The EARLY beam consists of a single injected pulse from the LINAC3 accelerator, whereas seven consecutive injections are accumulated, and electron cooled for the NOMINAL beam. In both cases, the longitudinal Schottky monitor allows assessing the longitudinal particle distribution during the cooling process on the injection plateau. A method has been established to analyze the Schottky signal, reconstruct the initial particle momentum distribution and derive relevant parameters such as the cooling time, energy off-set of injected and stacked beam or the momentum distribution of the lost beam. The variations of the obtained parameters and the impact on the LEIR performance will be addressed.
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TUPAF039	Electron Cooling Simulation and Experimental Benchmarks at LEIR	776
	A. Latina, H. Bartosik, N. Biancacci, R. Corsini, D. Gamba, S. Hirlaender, A. Huschauer CERN, Geneva, Switzerland
	A fast and accurate simulation of Electron Cooling has recently been implemented in the tracking code RF-Track. The implementation, which is based on a "hybrid kinetic" model, enables the simulation of a large variety of realistic scenarios, including imperfections such as gradients in the electron density, misalignments of electrons / ions / solenoidal fields, both in the static and in the dynamic regimes. Benchmarks of the simulations against measurements performed at LEIR, using Lead and Xenon ions, are presented.
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TUPAF047	Systematic Studies of Transverse Emittance Measurements Along the CERN PS Booster Cycle	806
	A. Santamaría García, S.C.P. Albright, H. Bartosik, J.A. Briz Monago, G.P. Di Giovanni, V. Forte, B. Mikulec, F. Roncarolo, V. Vlachoudis CERN, Geneva, Switzerland
	The CERN Proton Synchrotron Booster (PSB) will need to deliver 2 times the current brightness to the Large Hadron Collider (LHC) after the LHC Injectors Upgrade (LIU) to meet the High-Luminosity-LHC beam requirements. Beam intensity and transverse emittance are the key parameters to increase brightness, the latter being more difficult to manipulate. It is, therefore, crucial to monitor not only the emittance evolution between the different injectors but also along each acceleration cycle. To this end, detailed emittance measurements were carried out for the four rings of the PSB at various times in the cycle with different beam types. A thorough analysis of systematic error sources was conducted including multiple Coulomb scattering happening during profile measurements with wire scanners, where experimental and analytical treatments of the emittance blow-up were compared to FLUKA simulations. In order to properly account for the dispersive contribution, the full momentum spread profile was considered using a deconvolution method. We conclude with an assessment of this first comprehensive emittance evolution measurement along the PSB cycle.
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TUPAF048	LIU Space Charge Studies for the LHC Pre-Accelerators	810
	F. Schmidt, H. Bartosik CERN, Geneva, Switzerland
	In 2011 a working group has been started to study performance limitations due to Space Charge (SC) in the four LHC pre-accelerators, LEIR, PSB, PS & SPS, in view of the LHC Injector Upgrade (LIU) project. To this end external and in-house simulation tools have been benchmarked for the LIU study cases with the long-term goal of providing a full sequence of tested CERN Space Charge tools. It became clear that SC studies must be combined with trustworthy models of the machines, including linear and non-linear errors. In particular an effective s-dependent non-linear model is required. Recent studies indicate that also the low frequency ripple spectrum due to conventional power supplies might play an important role for the beam dynamics in presence of space charge in the pre-injectors.
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TUZGBD4	Impact of a Wideband Feedback Prototype System on TMCI in the SPS	1208
	W. Höfle, H. Bartosik, E.R. Bjørsvik, G. Kotzian, T.E. Levens, K.S.B. Li CERN, Geneva, Switzerland J.E. Dusatko, J.D. Fox, C.H. Rivetta SLAC, Menlo Park, California, USA O. Turgut Stanford University, Stanford, California, USA
	The transverse mode coupling instability (TMCI) in the SPS has been identified as one of the potential performance limitations for future high intensity LHC beams that will be required for the High Luminosity (HL)-LHC era and is being addressed by the LHC Injector Upgrade Project (LIU). A potential mitigation can be provided by wideband feedback systems with a frequency reach of about 1 GHz . For this reason, the development of a prototype system has been started in a CERN collaboration within the US-LARP framework in 2008. In this report we present latest experimental results in 2017 where this prototype system was used in single and multi-bunch studies. In particular, a successful mitigation against TMCI at injection could be demonstrated in single bunch studies.
	Slides TUZGBD4 [15.116 MB]
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WEYGBD3	The CERN Gamma Factory Initiative: An Ultra-High Intensity Gamma Source	1780
	M.W. Krasny LPNHE, Paris, France R. Alemany-Fernández, H. Bartosik, N. Biancacci, P. Czodrowski, B. Goddard, S. Hirlaender, J.M. Jowett, R. Kersevan, M. Kowalska, M.W. Krasny, M. Lamont, D. Manglunki, A.V. Petrenko, M. Schaumann, C. Yin Vallgren, F. Zimmermann CERN, Geneva, Switzerland P.S. Antsifarov Institute of Spectroscopy, Russian Academy of Science, Troitsk, Moscow, Russia A. Apyan ANSL, Yerevan, Armenia E.G. Bessonov LPI, Moscow, Russia J. Bieron, K. Dzierzega, W. Placzek, S. Pustelny Marian Smoluchowski Institute of Physics, Jagiellonian University, Kraków, Poland D. Budker Johannes Gutenberg University Mainz, Institut für Physik, Mainz, Germany K. Cassou, I. Chaikovska, R. Chehab, K. Dupraz, A. Martens, Z.F. Zomer LAL, Orsay, France F. Castelli Università degli Studi di Milano, Milano, Italy C. Curatolo, L. Serafini Istituto Nazionale di Fisica Nucleare, Milano, Italy K. Kroeger FSU Jena, Jena, Germany V. Petrillo Universita' degli Studi di Milano & INFN, Milano, Italy V.P. Shevelko LPI RAS, Moscow, Russia T. Stöhlker HIJ, Jena, Germany G. Weber IOQ, Jena, Germany Y.K. Wu FEL/Duke University, Durham, North Carolina, USA M.S. Zolotorev LBNL, Berkeley, California, USA
	This contribution discusses the possibility of broadening the present CERN research programme making use of a novel concept of light source. The proposed, Partially Stripped Ion beam driven, light source is the backbone of the Gamma Factory (GF) initiative. It could be realized at CERN by using the infrastructure of the already existing accelerators. It could push the intensity limits of the presently operating light-sources by up to 7 orders of magnitude, reaching fluxes of 10¹⁷ photons/s in the interesting gamma-ray energy domain between 1 MeV and 400 MeV. The GF light-source cannot be replaced, in this energy domain, by a FEL source as long as the multi TeV electron beams are not available. Its intensity is beyond the reach of the Inverse Compton Scattering sources. The unprecedented-intensity, energy-tuned gamma beams, together with the gamma-beams-driven secondary beams of polarized leptons, neutrinos, neutrons and radioactive ions are the basic research tools of the proposed Gamma Factory. A broad spectrum of new opportunities, in a vast domain of uncharted fundamental and applied physics territories, could be opened by the Gamma Factory research programme.
	Slides WEYGBD3 [7.531 MB]
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WEPAL079	Control of Intra-Bunch Vertical Motion in the SPS with GHz Bandwidth Feedback	2365
	J.D. Fox, J.E. Dusatko, C.H. Rivetta, O. Turgut SLAC, Menlo Park, California, USA H. Bartosik, E.R. Bjørsvik, W. Höfle, G. Kotzian, K.S.B. Li, E. Métral, B. Salvant, U. Wehrle CERN, Geneva, Switzerland S. De Santis LBNL, Berkeley, California, USA
	Funding: Work supported by the U.S. Department of Energy DE-AC02-76SF00515, US LHC Accelerator Research program, CERN LHC Injector Upgrade Project and the US-Japan Cooperative Program in High Energy Physics. A GHz bandwidth vertical beam feedback system has been in development at the CERN SPS to explore control of unstable beam motion in single bunch and bunch train configurations. We present measurements and recent studies of stable and unstable motion for intensities up to 2x10¹¹ p/bunch. The system has been operated at 3.2GS/s with 16 samples across a 5 ns RF bucket (4.2 ns 3 σ bunch at injection). Experimental results confirm damping of intra-bunch instabilities in Q20, Q22 and Q26 optics configurations. Instabilities with growth times of 200 turns are well-controlled from injection, consistent with the achievable gains for the 2 installed stripline kickers with 1 kW broadband total power. Studies of the damping achieved with the diagonal FIR controllers and existing system noise floors are highlighted to evaluate benefits of MIMO feedback controllers. The work is motivated by anticipated intensity increases from the LIU and HL-LHC upgrade programs, and has included the development of a new 1 GHz bandwidth slotline kicker structure and associated amplifier system
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THPAF034	Studies of Horizontal Instabilities in the CERN SPS	3032
SUSPF091	use link to see paper's listing under its alternate paper code
	M.S. Beck, H. Bartosik, M. Carlà, K.S.B. Li, G. Rumolo, M. Schenk CERN, Geneva, Switzerland U. van Rienen Rostock University, Faculty of Engineering, Rostock, Germany
	In the framework of the LHC Injectors Upgrade (LIU), beams with double intensity with respect to the present values will have to be successfully accelerated by the CERN Super Proton Synchrotron (SPS) and extracted towards the Large Hadron Collider (LHC). However, first experience running with intensity higher than the nominal LHC beam has shown that coherent instabilities in the horizontal plane may develop, becoming a potential intensity limitation for the future high intensity operation. To understand the mechanism of these instabilities, the PyHEADTAIL code has been used to check if the SPS impedance model reproduces the observations. The instability growth rates have been studied for different machine models and different chromaticity settings. In addition, the effect of other stabilizing methods, like the octupoles and the transverse damper, has also been investigated. Measurements are presented to benchmark the simulations.
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THPAF054	Characterization of Losses and Emittance Growth for Ion Beams on the SPS Injection Plateau	3091
	Á. Saá Hernández, F. Antoniou, H. Bartosik, A. Huschauer CERN, Geneva, Switzerland
	Losses and transverse emittance growth in the Super Protron Synchrotron (SPS) impose presently the main performance limitation on the Large Hadron Collider (LHC) ion injector chain. In this paper we present the measurements performed in 2016 with Pb⁸²⁺ ions and the analysis to characterize the observations of beam degradation during the long injection plateau. Residual gas scattering, intrabeam scattering (IBS) and resonance excitation have been studied.
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THPAF055	Space Charge Studies on LEIR	3095
	Á. Saá Hernández, H. Bartosik, N. Biancacci, S. Hirlaender, A. Huschauer, D. Moreno Garcia CERN, Geneva, Switzerland
	The performance of the CERN Low Energy Ion Ring with electron cooled ion beams is presently limited by losses occurring once the beam has been captured in the RF buckets. An intense machine study program was started by the end of 2015 to mitigate the losses and improve the performance of the accelerator. The measurements pointed to the interplay of direct space charge forces and excited betatron resonances as the most plausible driving mechanism of these losses. In this paper, we present the systematic space-charge measurements performed in 2017 and compare them to space-charge tracking simulations based on an adaptive frozen potential.
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THPAK056	Resonance Identification Studies at the CERN PS	3350
SUSPF081	use link to see paper's listing under its alternate paper code
	F. Asvesta NTUA, Athens, Greece H. Bartosik, A. Huschauer, Y. Papaphilippou, G. Sterbini CERN, Geneva, Switzerland
	In view of the LHC Injectors Upgrade (LIU) and the challenging high brightness target beam parameters, a broad range of possible working points for the Proton Synchrotron (PS) is being investigated. High order resonances have been identified, both structural resonances driven by space charge due to the lattice harmonics of the PS, and resonances excited by multipolar components in the machine. This paper provides a summary of the performed tune scan studies, covering both experimental and simulation results. Furthermore, non-linear analysis techniques have been used to characterize the resonances and their effect on the beam in presence of space charge.
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THPMF015	Lifetime and Beam Losses Studies of Partially Strip Ions in the SPS (129Xe³⁹⁺)	4070
	S. Hirlaender, R. Alemany-Fernández, H. Bartosik, N. Biancacci, T. Bohl, S. Cettour Cave, K. Cornelis, B. Goddard, V. Kain, M.W. Krasny, M. Lamont, D. Manglunki, G. Papotti, M. Schaumann, F. Zimmermann CERN, Geneva, Switzerland K. Kroeger FSU Jena, Jena, Germany V.P. Shevelko LPI RAS, Moscow, Russia T. Stöhlker, G. Weber IOQ, Jena, Germany
	The CERN multipurpose Gamma Factory proposal relies on using Partially Stripped Ion (PSI) beams, instead of electron beams, as the drivers of its light source. If such beams could be successfully stored in the LHC ring, fluxes of the order of 10¹⁷ photons/s, in the gamma-ray energy domain between 1 MeV and 400 MeV could be achieved. This energy domain is out of reach for the FEL-based light sources as long as the multi TeV electron beams are not available. The CERN Gamma Factory proposal has the potential of increasing by 7 orders of magnitude the intensity limits of the present Inverse Compton Scattering sources. In 2017 the CERN accelerator complex demonstrated its flexibility by producing a new, xenon, ion beam. The Gamma Factory study group, based on this achievement, requested special studies. Its aim was to inject and to accelerate, in the SPS, partially stripped xenon ions Xe³⁹⁺ measure their life time, and determine the relative strength of the processes responsible for the PSI beam losses. This study, the results of which are presented in this contribution, was an initial step in view of the the future studies programmed for 2018 with lead PSI beams.
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Paper

Title

Page

Emittance Growth in Coast in the SPS at CERN

257

F. Antoniou, H. Bartosik, T. Bohl, R. Calaga, L.R. Carver, J. Repond, G. Vandoni
CERN, Geneva, Switzerland
A. Alekou
UMAN, Manchester, United Kingdom

Funding: Research supported by the HL-LHC project.
The HL-LHC prototype crab-cavities are installed in the CERN SPS, which will allow for a comprehensive beam test with high energy protons for the first time. As the time available for experimental beam dynamics studies with the crab cavities installed in the machine will be limited, a very good preparation is required. One of the main concerns is the induced emittance growth, driven by phase amplitude jitter in the crab cavities. In this respect, several machine development (MD) studies were performed during the past years to quantify and characterize the long term emittance evolution of proton beams in the SPS. In these proceedings, the experimental observations from past years are summarized and the MD studies from 2016 and 2017 are presented.

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TUPAF020

Performance of the CERN Low Energy Ion Ring (LEIR) with Xenon beams

705

R. Alemany-Fernández, S.C.P. Albright, O. Andujar, M.E. Angoletta, J. Axensalva, H. Bartosik, G. Baud, N. Biancacci, M. Bozzolan, S. Cettour Cave, K. Cornelis, J. Dalla-Costa, M. Delrieux, A. Dworak, A. Findlay, F. Follin, A. Frassier, M. Gabriel, A. Guerrero, M. Haase, S. Hirlaender, S. Jensen, V. Kain, L.V. Kolbeck, Y. Le Borgne, D. Manglunki, O. Marqversen, S. Massot, D. Moreno Garcia, D.J.P. Nicosia, S. Pasinelli, L. Pereira, D. Perez, A. Rey, J.P. Ridewood, F. Roncarolo, Á. Saá Hernández, R. Scrivens, O.G. Sveen, G. Tranquille, E. Veyrunes
CERN, Geneva, Switzerland

In 2017 the CERN Low Energy Ion Ring demonstrated once more the feasibility of injecting, accumulating, cooling and accelerating a new nuclei, 129Xe39 . The operation of this new ion species started at the beginning of March with the start up of the xenon ion source and the Linac3. Ten weeks later the beam arrived to the Low Energy Ion Ring (LEIR) triggering the start of several weeks of beam commissioning in view of providing the injector complex with Xenon beams for different experiments and a series of machine development experiments in LEIR. Two types of beams were setup, the so called EARLY beam, with a single injection into LEIR from Linac3, and the NOMINAL beam with up to seven injections. 2017 was as well an interesting year for LEIR because several improvements in the control system of the accelerator and in the beam instrumentation were done in view of increasing the machine reliability. This paper summarises the beam commissioning phase and all the improvements carried out during 2017.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF020

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TUPAF021

Identification and Removal of SPS Aperture Limitations

709

V. Kain, R. Alemany-Fernández, H. Bartosik, S. Cettour Cave, K. Cornelis, P. Cruikshank, J.A. Ferreira Somoza, B. Goddard, C. Pasquino
CERN, Geneva, Switzerland

The CERN SPS (Super Proton Synchrotron) serves as LHC injector and provides beam for the North Area fixed target experiments. Since the 2016 run automated local aperture scans have been performed with the main focus on the vertical plane where limitations typically arise due to the flat vacuum chambers in most SPS elements. For LHC beams the aperture limitations with the present low integer tune optics also occur at locations with large dispersion. Aperture measurements in the horizontal plane using a variety of techniques were performed and showed surprising results, which could partially explain the unexpected losses of high intensity LHC beams at the SPS flat bottom. In this paper, reference measurements from 2016 are compared with the ones taken at the beginning of the run in 2017. Several aperture restrictions in the vertical plane could be found and cured, and a potential systematic restriction in the horizontal plane has been identified. The results of the measurements and the origin of the restrictions are presented in this paper, and the outlook for partial mitigation is discussed.

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TUPAF022

Studies of a New Optics With Intermediate Transition Energy as Alternative for High Intensity LHC Beams in the CERN SPS

713

M. Carlà, H. Bartosik, M.S. Beck, K.S.B. Li, M. Schenk
CERN, Geneva, Switzerland
M. Schenk
EPFL, Lausanne, Switzerland

The LHC injector upgrade project calls for a twofold increase in intensity of the SPS proton beam. In this paper, we present studies with a new SPS optics called Q22, which has a transition energy in between the one of the operationally used Q20 and Q26 optics. This new optics provides a compromise between the stability of Q20, due to the low transition energy, and the reduced requirements in terms of RF voltage and power in Q26. A non-linear effective model of Q22 has been extrapolated from beam based measurements and used to complement the SPS non-linear optics model. Furthermore the studies of the TMCI threshold performed so far are discussed.

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TUPAF024

Impedance and Instability Studies in LEIR with Xenon

720

N. Biancacci, H. Bartosik, M. Gąsior, S. Hirlaender, V. Kain, T.E. Levens, E. Métral
CERN, Geneva, Switzerland
M. Migliorati
Rome University La Sapienza, Roma, Italy

In 2017, the LEIR accelerator has been operated with Xe³⁹⁺ beam for fixed target experiments in the SPS North Area. The different ion species, with respect to the usually operated Pb⁵⁴⁺, allowed for additional comparative measurements of tune shift versus intensity at injection energy both in coasting and bunched beams. The fast transverse instability observed for high accumulated intensities has been as well characterized and additional observations relevant to impedance have been collected from longitudinal Schottky signal and BTF measurements. The results of these measurements are summarised and compared to the currently developed machine impedance model.

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TUPAF034

LEIR Injection Efficiency Studies as a Function of the Beam Energy Distribution from Linac3

758

S. Hirlaender, R. Alemany-Fernández, H. Bartosik, G. Bellodi, N. Biancacci, V. Kain, R. Scrivens
CERN, Geneva, Switzerland

High intensities in the CERN Low Energy Ion Ring (LEIR) are achieved using multi-turn injections from the pre-accelerator Linac3 combined with simultaneous stacking in momentum and transverse phase spaces. Up to seven consecutive 200 μs long, 200 ms spaced pulses are injected from Linac3 into LEIR by stacking each of them into the six-dimensional phase-space over 70 turns. An inclined septum magnet allows proper filling of the transverse phase-space plane, while longitudinal stacking requires momentum variation achieved by a shift of mean momentum over time provided by phase shifting a combination of 2 RF cavities at the exit of Linac3. The achievable maximum accumulated intensity depends strongly on the longitudinal beam quality of the injected beam. The longitudinal Schottky signal is used to measure the received energy distribution of the circulating beam which is then correlated with the obtained injection efficiency. This paper presents the experimental studies to understand and further improve the injection reliability and the longitudinal stacking.

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TUPAF035

Observations of SPS Slow-Extracted Spill Quality Degradation and Possible Improvements

761

F.M. Velotti, H. Bartosik, K. Cornelis, M.A. Fraser, B. Goddard, S. Hirlaender, V. Kain, O. Michels, M. Pari
CERN, Geneva, Switzerland

The SPS delivers slow extracted proton and heavy ion spills of several seconds to the North Area fixed target experiments with a very high duty factor. Reduced machine reproducibility due to magnetic history and power supply ripples on the main circuits lead however to frequent degradation of the spill duty factor. In this paper, the measured effect of the SPS magnetic history on spill quality and principal machine parameters is presented. Another detailed measurement campaign was aimed at characterising the frequency content and response of the spill to noise on the main power supplies ripples. The main findings of this study will also be reported. Finally, simulations of possible improvements based on the data acquired are discussed, as well as an extrapolation to the possible spill quality after the implementation of the improvements.

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TUPAF036

Studies of the Injection and Cooling Efficiency in LEIR Using the Longitudinal Schottky Spectrum

765

S. Hirlaender, R. Alemany-Fernández, H. Bartosik, N. Biancacci, V. Kain
CERN, Geneva, Switzerland

The CERN Low Energy Ion Ring (LEIR) has two main operational beams with their associated cycles, the so-called EARLY and the NOMINAL beam. The EARLY beam consists of a single injected pulse from the LINAC3 accelerator, whereas seven consecutive injections are accumulated, and electron cooled for the NOMINAL beam. In both cases, the longitudinal Schottky monitor allows assessing the longitudinal particle distribution during the cooling process on the injection plateau. A method has been established to analyze the Schottky signal, reconstruct the initial particle momentum distribution and derive relevant parameters such as the cooling time, energy off-set of injected and stacked beam or the momentum distribution of the lost beam. The variations of the obtained parameters and the impact on the LEIR performance will be addressed.

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TUPAF039

Electron Cooling Simulation and Experimental Benchmarks at LEIR

776

A. Latina, H. Bartosik, N. Biancacci, R. Corsini, D. Gamba, S. Hirlaender, A. Huschauer
CERN, Geneva, Switzerland

A fast and accurate simulation of Electron Cooling has recently been implemented in the tracking code RF-Track. The implementation, which is based on a "hybrid kinetic" model, enables the simulation of a large variety of realistic scenarios, including imperfections such as gradients in the electron density, misalignments of electrons / ions / solenoidal fields, both in the static and in the dynamic regimes. Benchmarks of the simulations against measurements performed at LEIR, using Lead and Xenon ions, are presented.

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TUPAF047

Systematic Studies of Transverse Emittance Measurements Along the CERN PS Booster Cycle

806

A. Santamaría García, S.C.P. Albright, H. Bartosik, J.A. Briz Monago, G.P. Di Giovanni, V. Forte, B. Mikulec, F. Roncarolo, V. Vlachoudis
CERN, Geneva, Switzerland

The CERN Proton Synchrotron Booster (PSB) will need to deliver 2 times the current brightness to the Large Hadron Collider (LHC) after the LHC Injectors Upgrade (LIU) to meet the High-Luminosity-LHC beam requirements. Beam intensity and transverse emittance are the key parameters to increase brightness, the latter being more difficult to manipulate. It is, therefore, crucial to monitor not only the emittance evolution between the different injectors but also along each acceleration cycle. To this end, detailed emittance measurements were carried out for the four rings of the PSB at various times in the cycle with different beam types. A thorough analysis of systematic error sources was conducted including multiple Coulomb scattering happening during profile measurements with wire scanners, where experimental and analytical treatments of the emittance blow-up were compared to FLUKA simulations. In order to properly account for the dispersive contribution, the full momentum spread profile was considered using a deconvolution method. We conclude with an assessment of this first comprehensive emittance evolution measurement along the PSB cycle.

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TUPAF048

LIU Space Charge Studies for the LHC Pre-Accelerators

810

F. Schmidt, H. Bartosik
CERN, Geneva, Switzerland

In 2011 a working group has been started to study performance limitations due to Space Charge (SC) in the four LHC pre-accelerators, LEIR, PSB, PS & SPS, in view of the LHC Injector Upgrade (LIU) project. To this end external and in-house simulation tools have been benchmarked for the LIU study cases with the long-term goal of providing a full sequence of tested CERN Space Charge tools. It became clear that SC studies must be combined with trustworthy models of the machines, including linear and non-linear errors. In particular an effective s-dependent non-linear model is required. Recent studies indicate that also the low frequency ripple spectrum due to conventional power supplies might play an important role for the beam dynamics in presence of space charge in the pre-injectors.

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TUZGBD4

Impact of a Wideband Feedback Prototype System on TMCI in the SPS

1208

W. Höfle, H. Bartosik, E.R. Bjørsvik, G. Kotzian, T.E. Levens, K.S.B. Li
CERN, Geneva, Switzerland
J.E. Dusatko, J.D. Fox, C.H. Rivetta
SLAC, Menlo Park, California, USA
O. Turgut
Stanford University, Stanford, California, USA

The transverse mode coupling instability (TMCI) in the SPS has been identified as one of the potential performance limitations for future high intensity LHC beams that will be required for the High Luminosity (HL)-LHC era and is being addressed by the LHC Injector Upgrade Project (LIU). A potential mitigation can be provided by wideband feedback systems with a frequency reach of about 1 GHz . For this reason, the development of a prototype system has been started in a CERN collaboration within the US-LARP framework in 2008. In this report we present latest experimental results in 2017 where this prototype system was used in single and multi-bunch studies. In particular, a successful mitigation against TMCI at injection could be demonstrated in single bunch studies.

Slides TUZGBD4 [15.116 MB]

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WEYGBD3

The CERN Gamma Factory Initiative: An Ultra-High Intensity Gamma Source

1780

M.W. Krasny
LPNHE, Paris, France
R. Alemany-Fernández, H. Bartosik, N. Biancacci, P. Czodrowski, B. Goddard, S. Hirlaender, J.M. Jowett, R. Kersevan, M. Kowalska, M.W. Krasny, M. Lamont, D. Manglunki, A.V. Petrenko, M. Schaumann, C. Yin Vallgren, F. Zimmermann
CERN, Geneva, Switzerland
P.S. Antsifarov
Institute of Spectroscopy, Russian Academy of Science, Troitsk, Moscow, Russia
A. Apyan
ANSL, Yerevan, Armenia
E.G. Bessonov
LPI, Moscow, Russia
J. Bieron, K. Dzierzega, W. Placzek, S. Pustelny
Marian Smoluchowski Institute of Physics, Jagiellonian University, Kraków, Poland
D. Budker
Johannes Gutenberg University Mainz, Institut für Physik, Mainz, Germany
K. Cassou, I. Chaikovska, R. Chehab, K. Dupraz, A. Martens, Z.F. Zomer
LAL, Orsay, France
F. Castelli
Università degli Studi di Milano, Milano, Italy
C. Curatolo, L. Serafini
Istituto Nazionale di Fisica Nucleare, Milano, Italy
K. Kroeger
FSU Jena, Jena, Germany
V. Petrillo
Universita' degli Studi di Milano & INFN, Milano, Italy
V.P. Shevelko
LPI RAS, Moscow, Russia
T. Stöhlker
HIJ, Jena, Germany
G. Weber
IOQ, Jena, Germany
Y.K. Wu
FEL/Duke University, Durham, North Carolina, USA
M.S. Zolotorev
LBNL, Berkeley, California, USA

This contribution discusses the possibility of broadening the present CERN research programme making use of a novel concept of light source. The proposed, Partially Stripped Ion beam driven, light source is the backbone of the Gamma Factory (GF) initiative. It could be realized at CERN by using the infrastructure of the already existing accelerators. It could push the intensity limits of the presently operating light-sources by up to 7 orders of magnitude, reaching fluxes of 10¹⁷ photons/s in the interesting gamma-ray energy domain between 1 MeV and 400 MeV. The GF light-source cannot be replaced, in this energy domain, by a FEL source as long as the multi TeV electron beams are not available. Its intensity is beyond the reach of the Inverse Compton Scattering sources. The unprecedented-intensity, energy-tuned gamma beams, together with the gamma-beams-driven secondary beams of polarized leptons, neutrinos, neutrons and radioactive ions are the basic research tools of the proposed Gamma Factory. A broad spectrum of new opportunities, in a vast domain of uncharted fundamental and applied physics territories, could be opened by the Gamma Factory research programme.

Slides WEYGBD3 [7.531 MB]

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WEPAL079

Control of Intra-Bunch Vertical Motion in the SPS with GHz Bandwidth Feedback

2365

J.D. Fox, J.E. Dusatko, C.H. Rivetta, O. Turgut
SLAC, Menlo Park, California, USA
H. Bartosik, E.R. Bjørsvik, W. Höfle, G. Kotzian, K.S.B. Li, E. Métral, B. Salvant, U. Wehrle
CERN, Geneva, Switzerland
S. De Santis
LBNL, Berkeley, California, USA

Funding: Work supported by the U.S. Department of Energy DE-AC02-76SF00515, US LHC Accelerator Research program, CERN LHC Injector Upgrade Project and the US-Japan Cooperative Program in High Energy Physics.
A GHz bandwidth vertical beam feedback system has been in development at the CERN SPS to explore control of unstable beam motion in single bunch and bunch train configurations. We present measurements and recent studies of stable and unstable motion for intensities up to 2x10¹¹ p/bunch. The system has been operated at 3.2GS/s with 16 samples across a 5 ns RF bucket (4.2 ns 3 σ bunch at injection). Experimental results confirm damping of intra-bunch instabilities in Q20, Q22 and Q26 optics configurations. Instabilities with growth times of 200 turns are well-controlled from injection, consistent with the achievable gains for the 2 installed stripline kickers with 1 kW broadband total power. Studies of the damping achieved with the diagonal FIR controllers and existing system noise floors are highlighted to evaluate benefits of MIMO feedback controllers. The work is motivated by anticipated intensity increases from the LIU and HL-LHC upgrade programs, and has included the development of a new 1 GHz bandwidth slotline kicker structure and associated amplifier system

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THPAF034

Studies of Horizontal Instabilities in the CERN SPS

3032

SUSPF091

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M.S. Beck, H. Bartosik, M. Carlà, K.S.B. Li, G. Rumolo, M. Schenk
CERN, Geneva, Switzerland
U. van Rienen
Rostock University, Faculty of Engineering, Rostock, Germany

In the framework of the LHC Injectors Upgrade (LIU), beams with double intensity with respect to the present values will have to be successfully accelerated by the CERN Super Proton Synchrotron (SPS) and extracted towards the Large Hadron Collider (LHC). However, first experience running with intensity higher than the nominal LHC beam has shown that coherent instabilities in the horizontal plane may develop, becoming a potential intensity limitation for the future high intensity operation. To understand the mechanism of these instabilities, the PyHEADTAIL code has been used to check if the SPS impedance model reproduces the observations. The instability growth rates have been studied for different machine models and different chromaticity settings. In addition, the effect of other stabilizing methods, like the octupoles and the transverse damper, has also been investigated. Measurements are presented to benchmark the simulations.

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THPAF054

Characterization of Losses and Emittance Growth for Ion Beams on the SPS Injection Plateau

3091

Á. Saá Hernández, F. Antoniou, H. Bartosik, A. Huschauer
CERN, Geneva, Switzerland

Losses and transverse emittance growth in the Super Protron Synchrotron (SPS) impose presently the main performance limitation on the Large Hadron Collider (LHC) ion injector chain. In this paper we present the measurements performed in 2016 with Pb⁸²⁺ ions and the analysis to characterize the observations of beam degradation during the long injection plateau. Residual gas scattering, intrabeam scattering (IBS) and resonance excitation have been studied.

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THPAF055

Space Charge Studies on LEIR

3095

Á. Saá Hernández, H. Bartosik, N. Biancacci, S. Hirlaender, A. Huschauer, D. Moreno Garcia
CERN, Geneva, Switzerland

The performance of the CERN Low Energy Ion Ring with electron cooled ion beams is presently limited by losses occurring once the beam has been captured in the RF buckets. An intense machine study program was started by the end of 2015 to mitigate the losses and improve the performance of the accelerator. The measurements pointed to the interplay of direct space charge forces and excited betatron resonances as the most plausible driving mechanism of these losses. In this paper, we present the systematic space-charge measurements performed in 2017 and compare them to space-charge tracking simulations based on an adaptive frozen potential.

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THPAK056

Resonance Identification Studies at the CERN PS

3350

SUSPF081

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F. Asvesta
NTUA, Athens, Greece
H. Bartosik, A. Huschauer, Y. Papaphilippou, G. Sterbini
CERN, Geneva, Switzerland

In view of the LHC Injectors Upgrade (LIU) and the challenging high brightness target beam parameters, a broad range of possible working points for the Proton Synchrotron (PS) is being investigated. High order resonances have been identified, both structural resonances driven by space charge due to the lattice harmonics of the PS, and resonances excited by multipolar components in the machine. This paper provides a summary of the performed tune scan studies, covering both experimental and simulation results. Furthermore, non-linear analysis techniques have been used to characterize the resonances and their effect on the beam in presence of space charge.

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THPMF015

Lifetime and Beam Losses Studies of Partially Strip Ions in the SPS (129Xe³⁹⁺)

4070

S. Hirlaender, R. Alemany-Fernández, H. Bartosik, N. Biancacci, T. Bohl, S. Cettour Cave, K. Cornelis, B. Goddard, V. Kain, M.W. Krasny, M. Lamont, D. Manglunki, G. Papotti, M. Schaumann, F. Zimmermann
CERN, Geneva, Switzerland
K. Kroeger
FSU Jena, Jena, Germany
V.P. Shevelko
LPI RAS, Moscow, Russia
T. Stöhlker, G. Weber
IOQ, Jena, Germany

The CERN multipurpose Gamma Factory proposal relies on using Partially Stripped Ion (PSI) beams, instead of electron beams, as the drivers of its light source. If such beams could be successfully stored in the LHC ring, fluxes of the order of 10¹⁷ photons/s, in the gamma-ray energy domain between 1 MeV and 400 MeV could be achieved. This energy domain is out of reach for the FEL-based light sources as long as the multi TeV electron beams are not available. The CERN Gamma Factory proposal has the potential of increasing by 7 orders of magnitude the intensity limits of the present Inverse Compton Scattering sources. In 2017 the CERN accelerator complex demonstrated its flexibility by producing a new, xenon, ion beam. The Gamma Factory study group, based on this achievement, requested special studies. Its aim was to inject and to accelerate, in the SPS, partially stripped xenon ions Xe³⁹⁺ measure their life time, and determine the relative strength of the processes responsible for the PSI beam losses. This study, the results of which are presented in this contribution, was an initial step in view of the the future studies programmed for 2018 with lead PSI beams.

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