IPAC2017 - List of Authors (Kain, V.)

Paper	Title	Page
MOPIK045	SPS Slow Extraction Losses and Activation: Challenges and Possibilities for Improvement	611
	M.A. Fraser, B. Balhan, H. Bartosik, C. Bertone, D. Björkman, J.C.C.M. Borburgh, N. Conan, K. Cornelis, R. Garcia Alia, L. Gatignon, B. Goddard, Y. Kadi, V. Kain, A. Mereghetti, F. Roncarolo, P.M. Schicho, J. Spanggaard, O. Stein, L.S. Stoel, F.M. Velotti, H. Vincke CERN, Geneva, Switzerland
	In 2015 the highest integrated number of protons in the history of the North Area was slow extracted from the CERN Super Proton Synchrotron (SPS) for the Fixed Target physics programme. At well over 1.10¹⁹ protons on target (POT), this represented the highest annual figure at SPS for almost two decades, since the West Area Neutrino Facility was operational some 20 years ago. The high intensity POT requests have continued into 2016-17 and look set to do so for the foreseeable future, especially in view of the proposed SPS Beam Dump Facility and experiments, e.g. SHiP, which are requesting up to 4·10¹⁹ POT per year. Without significant improvements, the attainable annual POT will be limited to well below the total the SPS machine could deliver, due to activation of accelerator equipment and associated personnel dose limitations. In this contribution, the issues arising from the recent high activation levels are discussed along with the steps taken to understand, manage and mitigate these issues. The research avenues being actively pursued to improve the slow extraction related beam loss for present operation and future requests are outlined, and their relative merits discussed. A. Golutvin et al., ‘‘A Facility to Search for Hidden Particles (SHiP) at the CERN SPS'', CERN, Geneva, Switzerland, Rep. CERN-SPSC-2015-016 (SPSC-P-350), Apr. 2015.
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MOPIK046	Phase Space Folding Studies for Beam Loss Reduction During Resonant Slow Extraction at the CERN SPS	615
	L.S. Stoel, M. Benedikt, K. Cornelis, M.A. Fraser, B. Goddard, V. Kain, F.M. Velotti CERN, Geneva, Switzerland
	The requested number of protons slow-extracted from the CERN Super Proton Synchrotron (SPS) for Fixed Target (FT) physics is expected to continue increasing in the coming years, especially if the proposed SPS Beam Dump Facility is realised. Limits on the extracted intensity are already being considered to mitigate the dose to personnel during interventions required to maintain the extraction equipment, especially the electrostatic extraction septum. In addition to other on-going studies and technical developments, a reduction of the beam loss per extracted proton will play a crucial role in the future performance reach of the FT experimental programme at the SPS. In this paper a concept is investigated to reduce the fraction of beam impacting the extraction septum by folding the arm of the phase space separatrix. Beam dynamics simulations for the concept are presented and compared to the phase space acceptance of the extraction channel. The performance potential of the concept at SPS is evaluated and discussed alongside the necessary changes to the non-linear optical elements in the machine.
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MOPIK048	Experimental Results of Crystal-Assisted Slow Extraction at the SPS	623
	M.A. Fraser, S.S. Gilardoni, B. Goddard, V. Kain, D. Mirarchi, S. Montesano, S. Petrucci, S. Redaelli, R. Rossi, W. Scandale, L.S. Stoel, F.M. Velotti CERN, Geneva, Switzerland F.M. Addesa, G. Cavoto, F. Iacoangeli INFN-Roma, Roma, Italy F. Galluccio INFN-Napoli, Napoli, Italy F. Murtas INFN/LNF, Frascati (Roma), Italy
	The possibility of extracting highly energetic particles from the Super Proton Synchrotron (SPS) by means of silicon bent crystals has been explored since the 1990's. The channelling effect of a bent crystal can be used to strongly deflect primary protons and eject them from the synchrotron. Many studies and experiments have been carried out to investigate crystal channelling effects. The extraction of 120 and 270 GeV proton beams has already been demonstrated in the SPS with dedicated experiments located in the ring. Presently in the SPS, the UA9 experiment is performing studies to evaluate the possibility to use bent silicon crystals to steer particle beams in high energy accelerators. Recent studies on the feasibility of extraction from the SPS have been made using the UA9 infrastructure with a longer-term view of using crystals to help mitigate slow extraction induced activation of the SPS. In this paper, the possibility to eject particles into the extraction channel in LSS2 using the bent crystals already installed in the SPS is presented. Details of the concept, simulations and measurements carried out with beam are presented, before the outlook for the future is discussed.
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MOPIK049	SPS Slow Extracted Spill Quality During the 2016 Run	627
	V. Kain, J. Bauche, P. Catherine, K. Cornelis, M.A. Fraser, L. Gatignon, C.M. Genton, B. Goddard, K. Kahle, M. Magrans de Abril, O. Michels, L.S. Stoel, F.M. Velotti CERN, Geneva, Switzerland
	The flux of particles slow extracted with the 1/3 integer resonance from the Super Proton Synchrotron at CERN should ideally be constant over the length of the extraction plateau, for optimum use of the beam by the fixed target experiments. The extracted intensity is controlled in feed-forward correction of the horizontal tune via the main SPS quadrupoles. The Mains power supply noise at 50 Hz and harmonics is also corrected in feed-forward by small amplitude tune modulation at the respective frequencies with a dedicated additional quadrupole circuit. In 2016 the spill quality could be much improved with respect to the situation of the previous year with more performant algorithms. In this paper the improved tools are described and the characteristics of the SPS slow extracted spill in terms of macro structure and typical frequency content are shown. Other sources of perturbation were, however, also present in 2016 which frequently caused the spill quality to be much reduced. The different effects are discussed and possible or actual solutions detailed. Finally, the evolution of the spill quality during characteristic periods in the 2016 run is presented.
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MOPIK050	Reduction of Resonant Slow Extraction Losses with Shadowing of Septum Wires by a Bent Crystal	631
	F.M. Velotti, M.A. Fraser, B. Goddard, V. Kain, W. Scandale, L.S. Stoel CERN, Geneva, Switzerland
	A new experiment, SHiP, is being studied at CERN to investigate the existence of three Heavy Neutral Leptons in order to give experimental proof to the proposed neutrino minimal Standard Model. High-intensity slow-extraction of protons from the SPS is a pre-requisite for SHiP. The experiment requires a resonant extraction with in a 7.2 s cycle, and about 4·10¹³ protons extracted at 400 GeV in a 1 s flat-top, to achieve the needed 2·10²⁰ protons on target in five years. Although the SPS has delivered this in the past to the CNGS experiment with fast extraction, for SHiP beam losses and activation of the SPS electrostatic extraction septum (ZS) could be a serious performance limitation, since the target number of protons to resonantly extract per year is a factor of two higher than ever achieved before and a factor of four than ever reached with the third-integer slow extraction. In this paper, a novel extraction technique to significantly reduce the losses at the ZS is proposed, based on the use of a bent crystal to shadow the septum wires. Theoretical concepts are developed, the performance gain quantified and a possible layout proposed.
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TUOAB1	First LHC Transverse Beam Size Measurements With the Beam Gas Vertex Detector	1240
SUSPSIK078	use link to see paper's listing under its alternate paper code
	A. Alexopoulos, C. Barschel, E. Bravin, G. Bregliozzi, N. Chritin, B. Dehning, M. Ferro-Luzzi, M. Giovannozzi, R. Jacobsson, L.K. Jensen, O.R. Jones, V. Kain, R. Matev, M.N. Rihl, V. Salustino Guimaraes, R. Veness, S. Vlachos, B. Würkner CERN, Geneva, Switzerland A. Bay, F. Blanc, S. Gianì, O. Girard, G.J. Haefeli, P. Hopchev, A. Kuonen, T. Nakada, O. Schneider, M. Tobin, Q.D. Veyrat, Z. Xu EPFL, Lausanne, Switzerland R. Greim, W. Karpinski, T. Kirn, S. Schael, A. Schultz von Dratzig, G. Schwering, M. Wlochal RWTH, Aachen, Germany
	The Beam Gas Vertex detector (BGV) is an innovative beam profile monitor based on the reconstruction of beam-gas interaction vertices which is being developed as part of the High Luminosity LHC project. Tracks are identified using several planes of scintillating fibres, located outside the beam vacuum chamber and perpendicular to the beam axis. The gas pressure in the interaction volume is adjusted such as to provide an adequate trigger rate, without disturbing the beam. A BGV demonstrator monitoring one of the two LHC beams was fully installed and commissioned in 2016. First data and beam size measurements show that the complete detector and data acquisition system is operating as expected. The BGV operating parameters are now being optimised and the reconstruction algorithms developed to produce accurate and fast reconstruction on a CPU farm in order to provide real time beam profile measurements to the LHC operators.
	Slides TUOAB1 [3.456 MB]
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TUPIK032	AWAKE Proton Beam Commissioning	1747
	J.S. Schmidt, D. Barrientos, M. Barros Marin, B. Biskup, A. Boccardi, T.B. Bogey, T. Bohl, C. Bracco, S. Cettour Cave, H. Damerau, V. Fedosseev, F. Friebel, S.J. Gessner, A. Goldblatt, E. Gschwendtner, L.K. Jensen, V. Kain, T. Lefèvre, S. Mazzoni, J.C. Molendijk, A. Pardons, C. Pasquino, S.F. Rey, H. Vincke, U. Wehrle CERN, Geneva, Switzerland J.T. Moody MPI-P, München, Germany K. Rieger MPI, Muenchen, Germany
	AWAKE will be the first proton driven plasma wakefield acceleration experiment worldwide. The facility is located in the former CNGS area at CERN and will include a proton, laser and electron beam line merging in a 10 m long plasma cell, which is followed by the experimental diagnostics. In the first phase of the AWAKE physics program, which started at the end of 2016, the effect of the plasma on a high energy proton beam will be studied. A proton bunch is expected to experience the so called self-modulation instability, which leads to the creation of micro-bunches within the long proton bunch. The plasma channel is created in a rubidium vapor via field ionization by a TW laser pulse. This laser beam has to overlap with the proton beam over the full length of the plasma cell, resulting in tight requirements for the stability of the proton beam at the plasma cell in the order of ~ 0.1 mm. In this paper the beam commissioning results of the ~810 m long transfer line for proton bunches with 3·10¹¹ protons/bunch and a momentum of 400 GeV/c will be presented with a focus on the challenges of the parallel operation of the laser and proton beam.
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TUPIK086	Modelling the Radioactivity Induced by Slow-Extraction Losses in the CERN SPS	1897
	M.A. Fraser, D. Björkman, K. Cornelis, B. Goddard, V. Kain, P.M. Schicho, C. Theis, H. Vincke CERN, Geneva, Switzerland
	Resonant slow extraction is used to provide an intense quasi-DC flux of high-energy protons for the Fixed Target (FT) physics programme at the CERN Super Proton Synchrotron (SPS). The unavoidable beam loss intrinsic to the extraction process activates the extraction region and its equipment. Although the radiation dose to equipment has an impact on availability, the cool-down times required to limit dose to the personnel carrying-out maintenance of the accelerator also pose important restrictions, and ultimately limit the number of protons on target. In order to understand how the extracted proton flux affects the build-up and subsequent cool-down of the induced activation, a model based on a simple empirical relationship has been developed and shown to predict the measured radioactive decay at ionisation chambers located along the extraction region. In this contribution, the empirical model is described, its strengths and limitations discussed, and its application as a predictive tool for estimating cool-down times as a function of extracted proton flux demonstrated.
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TUPVA020	The LHC Injectors Upgrade (LIU) Project at CERN: Ion Injector Chain	2089
	H. Bartosik, S.C.P. Albright, M.E. Angoletta, G. Bellodi, N. Biancacci, T. Bohl, J. Coupard, H. Damerau, A. Funken, B. Goddard, S. Hancock, K. Hanke, A. Huschauer, J.M. Jowett, V. Kain, D. Küchler, D. Manglunki, M. Meddahi, G. Rumolo, R. Scrivens, E.N. Shaposhnikova, V. Toivanen, F.J.C. Wenander CERN, Geneva, Switzerland
	The LHC injector chain for Pb-ion beams at CERN consists of Linac3, the accumulator ring LEIR, the PS and the SPS. In the context of the LHC injectors upgrade (LIU) project an intense program of machine development studies has been performed in the last two years to maximise the intensity of Pb-ion beams at LHC injection. In this paper we present an analysis of the operational performance achieved so far, with the goal of 1) identifying the remaining performance bottlenecks along the chain and possible areas for improvement, and 2) to optimize the Pb-ion beam production scheme for the High Luminosity (HL-) LHC era. A consistent set of beam parameters for the HL-LHC era has been established taking into account the already achieved improvements as well as foreseen upgrades still to be implemented, such as slip stacking in the SPS.
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TUPVA126	The SPS Beam Dump Facility	2389
	M. Lamont, G. Arduini, M. Battistin, M. Brugger, M. Calviani, F. B. Dos Santos Pedrosa, M.A. Fraser, L. Gatignon, S.S. Gilardoni, B. Goddard, J.L. Grenard, C. Heßler, R. Jacobsson, V. Kain, K. Kershaw, E. Lopez Sola, J.A. Osborne, A. Perillo-Marcone, H. Vincke CERN, Geneva, Switzerland
	The proposed SPS beam dump facility (BDF) is a fixed-target facility foreseen to be situated at the North Area of the SPS. Beam dump in this context implies a target aimed at absorbing the majority of incident protons and containing most of the cascade generated by the primary beam interaction. The aim is a general purpose fixed target facility, which in the initial phase is aimed at the Search for Hidden Particles (SHiP) experiment. Feasibility studies are ongoing at CERN to address the key challenges of the facility. These challenges include: slow resonant extraction from the SPS; a target that has the two-fold objective of producing charged mesons as well as stopping the primary proton beam; and radiation protection considerations related to primary proton beam with a power of around 355 kW. The aim of the project is to complete the key technical feasibility studies in time for the European Strategy for Particle Physics (ESPP) update foreseen in 2020. This is in conjunction with the recommendation by the CERN Research Board to the SHiP experiment to prepare a comprehensive design study as input to the ESPP.
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TUPVA128	Performance of the CERN Injector Complex and Transmission Studies into the LHC during the Second Proton-Lead Run	2395
	R. Alemany-Fernández, S.C.P. Albright, M.E. Angoletta, J. Axensalva, W. Bartmann, H. Bartosik, P. Baudrenghien, G. Bellodi, A. Blas, T. Bohl, E. Carlier, S. Cettour-Cave, K. Cornelis, H. Damerau, A. Findlay, S.S. Gilardoni, S. Hancock, A. Huschauer, M.A. Jebramcik, S. Jensen, J.M. Jowett, V. Kain, D. Küchler, A.M. Lombardi, D. Manglunki, T. Mertens, M. O'Neil, S. Pasinelli, Á. Saá Hernández, M. Schaumann, R. Scrivens, R. Steerenberg, H. Timko, V. Toivanen, G. Tranquille, F.M. Velotti, F.J.C. Wenander, J. Wenninger CERN, Geneva, Switzerland
	The LHC performance during the proton-lead run in 2016 fully relied on a permanent monitoring and systematic improvement of the beam quality in all the injectors. The beam production and characteristics are explained in this paper, together with the improvements realized during the run from the source up to the flat top of the LHC. Transmission studies from one accelerator to the next as well as beam quality evolution studies during the cycle at each accelerator, have been carried out and are summarized in this paper. In 2016, the LHC had to deliver the beams to the experiments at two different energies, 4 Z TeV and 6.5 Z TeV. The properties of the beams at these two energies are also presented
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WEPVA110	Analysis and Operational Feedback on the New Design of the High Energy Beam Dump in the CERN SPS	3524
	P. Rios Rodriguez, J.A. Briz Monago, M. Calviani, K. Cornelis, S. De Man, R. Esposito, S.S. Gilardoni, B. Goddard, J.L. Grenard, D. Grenier, M. Grieco, J. Humbert, V. Kain, F.M. Leaux, C. Pasquino, A. Perillo-Marcone, J.R.F. Poujol, S. Sgobba, D. Steyart, F.M. Velotti, V. Vlachoudis CERN, Geneva, Switzerland
	CERN's Super Proton Synchrotron (SPS) high-energy internal dump (Target Internal Dump Vertical Graphite, known as TIDVG) is required to intercept beams from 10² to 450 GeV. The equipment installed in 2014 (TIDVG#3) featured an absorbing core composed of different materials surrounded by a water-cooled copper jacket, which hold the UHV of the machine. An inspection of a previous equipment (TIDVG#2) in 2013 revealed significant beam induced damage to the aluminium section of the dump, which required imposing operational limitations to minimise the risk of reproducing this phenomenon. Additionally, in 2016 a vacuum leak was detected in the dump assembly, which imposed further limitations, i.e. a reduction of the beam intensity that could be dumped per SPS supercycle. This paper presents a new design (TIDVG#4), which focuses on improving the operational robustness of the device. Moreover, thanks to the added instrumentation, a careful analysis of its performance (both experimentally and during operation) will be possible. These studies will help validating technical solutions for the design of the future SPS dump to be installed during CERN's Long Shutdown 2 in 2020 (TIDVG#5).
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THPAB049	Progress in the Understanding of the Performance Limitations in the CERN Low Energy Ion Ring	3819
	A. Huschauer, H. Bartosik, S. Hancock, V. Kain CERN, Geneva, Switzerland
	The performance of heavy ion beams in the CERN Low Energy Ion Ring is mainly limited by beam loss occuring during the radio-frequency capture and the first part of acceleration. Since October 2015, the driving mechanism of these losses has been studied in detail and an interplay of direct space charge forces and excited betatron resonances was identified as the most plausible explanation of the phenomenon. In this paper we summarize the current understanding of the loss mechanism by presenting recent experimental and simulation studies. We discuss strategies to mitigate beam loss and further improve the performance of the accelerator in the future.
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THPAB146	Investigation of the Remanent Field of the SPS Main Dipoles and Possible Solutions for Machine Operation	4069
	F.M. Velotti, H. Bartosik, J. Bauche, M.C.L. Buzio, K. Cornelis, M.A. Fraser, V. Kain CERN, Geneva, Switzerland
	The CERN Super Proton Synchrotron (SPS) provides different types of beams at different extraction energies. The main magnets of the SPS are regulated with a current loop, but it has turned out that hysteresis effects from the main dipoles have a significant impact on reproducibility and hence efficiency and availability. Beam and machine parameters were found to depend on the programmed sequence of magnetic cycles - the so-called super cycle - representing the production of the different beams. The scientific program of the SPS requires frequent changes of the supercycle composition and the effect of the main magnet hysteresis has to be understood, modelled and used in accelerator control system. This paper summarises the first main field measurements carried out with the currently available systems during operational conditions as well as measurements of vital machine and beam parameters as a function of the super cycle composition. Finally, ideas will be presented to provide reproducibility by automatically correcting different parameters taking the magnetic history of the main magnets into account.
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THPAB147	Automatic Local Aperture Measurements in the SPS	4073
	V. Kain, H. Bartosik, S. Cettour Cave, K. Cornelis, F.M. Velotti CERN, Geneva, Switzerland
	The CERN SPS (Super Proton Synchrotron) serves as LHC injector and provides beam for the North Area fixed target experiments. It is equipped with flat vacuum chambers to accommodate the large horizontal beam size required during transition crossing and slow extraction. At low energy, the vertical acceptance becomes critical with high intensity large emittance fixed target beams. Optimizing the vertical available aperture is a key ingredient to optimize transmission and reduce activation around the ring. Aperture measurements are routinely carried out after each shutdown. Global vertical aperture measurements are followed by detailed bump scans at the locations with the loss peaks. During the 2016 run a tool was developed to provide an automated local aperture scan around the entire ring. This allowed to establish detailed reference measurements of the vertical aperture and identify directly the SPS aperture bottlenecks. The methodology applied for the scans will be briefly described in this paper and the analysis discussed. Finally, the 2016 SPS measured vertical aperture will be presented and compared to the results obtained with the previous method.
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Paper

Title

Page

SPS Slow Extraction Losses and Activation: Challenges and Possibilities for Improvement

611

M.A. Fraser, B. Balhan, H. Bartosik, C. Bertone, D. Björkman, J.C.C.M. Borburgh, N. Conan, K. Cornelis, R. Garcia Alia, L. Gatignon, B. Goddard, Y. Kadi, V. Kain, A. Mereghetti, F. Roncarolo, P.M. Schicho, J. Spanggaard, O. Stein, L.S. Stoel, F.M. Velotti, H. Vincke
CERN, Geneva, Switzerland

In 2015 the highest integrated number of protons in the history of the North Area was slow extracted from the CERN Super Proton Synchrotron (SPS) for the Fixed Target physics programme. At well over 1.10¹⁹ protons on target (POT), this represented the highest annual figure at SPS for almost two decades, since the West Area Neutrino Facility was operational some 20 years ago. The high intensity POT requests have continued into 2016-17 and look set to do so for the foreseeable future, especially in view of the proposed SPS Beam Dump Facility and experiments, e.g. SHiP*, which are requesting up to 4·10¹⁹ POT per year. Without significant improvements, the attainable annual POT will be limited to well below the total the SPS machine could deliver, due to activation of accelerator equipment and associated personnel dose limitations. In this contribution, the issues arising from the recent high activation levels are discussed along with the steps taken to understand, manage and mitigate these issues. The research avenues being actively pursued to improve the slow extraction related beam loss for present operation and future requests are outlined, and their relative merits discussed.
*A. Golutvin et al., ‘‘A Facility to Search for Hidden Particles (SHiP) at the CERN SPS'', CERN, Geneva, Switzerland, Rep. CERN-SPSC-2015-016 (SPSC-P-350), Apr. 2015.

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MOPIK046

Phase Space Folding Studies for Beam Loss Reduction During Resonant Slow Extraction at the CERN SPS

615

L.S. Stoel, M. Benedikt, K. Cornelis, M.A. Fraser, B. Goddard, V. Kain, F.M. Velotti
CERN, Geneva, Switzerland

The requested number of protons slow-extracted from the CERN Super Proton Synchrotron (SPS) for Fixed Target (FT) physics is expected to continue increasing in the coming years, especially if the proposed SPS Beam Dump Facility is realised. Limits on the extracted intensity are already being considered to mitigate the dose to personnel during interventions required to maintain the extraction equipment, especially the electrostatic extraction septum. In addition to other on-going studies and technical developments, a reduction of the beam loss per extracted proton will play a crucial role in the future performance reach of the FT experimental programme at the SPS. In this paper a concept is investigated to reduce the fraction of beam impacting the extraction septum by folding the arm of the phase space separatrix. Beam dynamics simulations for the concept are presented and compared to the phase space acceptance of the extraction channel. The performance potential of the concept at SPS is evaluated and discussed alongside the necessary changes to the non-linear optical elements in the machine.

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MOPIK048

Experimental Results of Crystal-Assisted Slow Extraction at the SPS

623

M.A. Fraser, S.S. Gilardoni, B. Goddard, V. Kain, D. Mirarchi, S. Montesano, S. Petrucci, S. Redaelli, R. Rossi, W. Scandale, L.S. Stoel, F.M. Velotti
CERN, Geneva, Switzerland
F.M. Addesa, G. Cavoto, F. Iacoangeli
INFN-Roma, Roma, Italy
F. Galluccio
INFN-Napoli, Napoli, Italy
F. Murtas
INFN/LNF, Frascati (Roma), Italy

The possibility of extracting highly energetic particles from the Super Proton Synchrotron (SPS) by means of silicon bent crystals has been explored since the 1990's. The channelling effect of a bent crystal can be used to strongly deflect primary protons and eject them from the synchrotron. Many studies and experiments have been carried out to investigate crystal channelling effects. The extraction of 120 and 270 GeV proton beams has already been demonstrated in the SPS with dedicated experiments located in the ring. Presently in the SPS, the UA9 experiment is performing studies to evaluate the possibility to use bent silicon crystals to steer particle beams in high energy accelerators. Recent studies on the feasibility of extraction from the SPS have been made using the UA9 infrastructure with a longer-term view of using crystals to help mitigate slow extraction induced activation of the SPS. In this paper, the possibility to eject particles into the extraction channel in LSS2 using the bent crystals already installed in the SPS is presented. Details of the concept, simulations and measurements carried out with beam are presented, before the outlook for the future is discussed.

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MOPIK049

SPS Slow Extracted Spill Quality During the 2016 Run

627

V. Kain, J. Bauche, P. Catherine, K. Cornelis, M.A. Fraser, L. Gatignon, C.M. Genton, B. Goddard, K. Kahle, M. Magrans de Abril, O. Michels, L.S. Stoel, F.M. Velotti
CERN, Geneva, Switzerland

The flux of particles slow extracted with the 1/3 integer resonance from the Super Proton Synchrotron at CERN should ideally be constant over the length of the extraction plateau, for optimum use of the beam by the fixed target experiments. The extracted intensity is controlled in feed-forward correction of the horizontal tune via the main SPS quadrupoles. The Mains power supply noise at 50 Hz and harmonics is also corrected in feed-forward by small amplitude tune modulation at the respective frequencies with a dedicated additional quadrupole circuit. In 2016 the spill quality could be much improved with respect to the situation of the previous year with more performant algorithms. In this paper the improved tools are described and the characteristics of the SPS slow extracted spill in terms of macro structure and typical frequency content are shown. Other sources of perturbation were, however, also present in 2016 which frequently caused the spill quality to be much reduced. The different effects are discussed and possible or actual solutions detailed. Finally, the evolution of the spill quality during characteristic periods in the 2016 run is presented.

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MOPIK050

Reduction of Resonant Slow Extraction Losses with Shadowing of Septum Wires by a Bent Crystal

631

F.M. Velotti, M.A. Fraser, B. Goddard, V. Kain, W. Scandale, L.S. Stoel
CERN, Geneva, Switzerland

A new experiment, SHiP, is being studied at CERN to investigate the existence of three Heavy Neutral Leptons in order to give experimental proof to the proposed neutrino minimal Standard Model. High-intensity slow-extraction of protons from the SPS is a pre-requisite for SHiP. The experiment requires a resonant extraction with in a 7.2 s cycle, and about 4·10¹³ protons extracted at 400 GeV in a 1 s flat-top, to achieve the needed 2·10²⁰ protons on target in five years. Although the SPS has delivered this in the past to the CNGS experiment with fast extraction, for SHiP beam losses and activation of the SPS electrostatic extraction septum (ZS) could be a serious performance limitation, since the target number of protons to resonantly extract per year is a factor of two higher than ever achieved before and a factor of four than ever reached with the third-integer slow extraction. In this paper, a novel extraction technique to significantly reduce the losses at the ZS is proposed, based on the use of a bent crystal to shadow the septum wires. Theoretical concepts are developed, the performance gain quantified and a possible layout proposed.

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TUOAB1

First LHC Transverse Beam Size Measurements With the Beam Gas Vertex Detector

1240

SUSPSIK078

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

A. Alexopoulos, C. Barschel, E. Bravin, G. Bregliozzi, N. Chritin, B. Dehning, M. Ferro-Luzzi, M. Giovannozzi, R. Jacobsson, L.K. Jensen, O.R. Jones, V. Kain, R. Matev, M.N. Rihl, V. Salustino Guimaraes, R. Veness, S. Vlachos, B. Würkner
CERN, Geneva, Switzerland
A. Bay, F. Blanc, S. Gianì, O. Girard, G.J. Haefeli, P. Hopchev, A. Kuonen, T. Nakada, O. Schneider, M. Tobin, Q.D. Veyrat, Z. Xu
EPFL, Lausanne, Switzerland
R. Greim, W. Karpinski, T. Kirn, S. Schael, A. Schultz von Dratzig, G. Schwering, M. Wlochal
RWTH, Aachen, Germany

The Beam Gas Vertex detector (BGV) is an innovative beam profile monitor based on the reconstruction of beam-gas interaction vertices which is being developed as part of the High Luminosity LHC project. Tracks are identified using several planes of scintillating fibres, located outside the beam vacuum chamber and perpendicular to the beam axis. The gas pressure in the interaction volume is adjusted such as to provide an adequate trigger rate, without disturbing the beam. A BGV demonstrator monitoring one of the two LHC beams was fully installed and commissioned in 2016. First data and beam size measurements show that the complete detector and data acquisition system is operating as expected. The BGV operating parameters are now being optimised and the reconstruction algorithms developed to produce accurate and fast reconstruction on a CPU farm in order to provide real time beam profile measurements to the LHC operators.

Slides TUOAB1 [3.456 MB]

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TUPIK032

AWAKE Proton Beam Commissioning

1747

J.S. Schmidt, D. Barrientos, M. Barros Marin, B. Biskup, A. Boccardi, T.B. Bogey, T. Bohl, C. Bracco, S. Cettour Cave, H. Damerau, V. Fedosseev, F. Friebel, S.J. Gessner, A. Goldblatt, E. Gschwendtner, L.K. Jensen, V. Kain, T. Lefèvre, S. Mazzoni, J.C. Molendijk, A. Pardons, C. Pasquino, S.F. Rey, H. Vincke, U. Wehrle
CERN, Geneva, Switzerland
J.T. Moody
MPI-P, München, Germany
K. Rieger
MPI, Muenchen, Germany

AWAKE will be the first proton driven plasma wakefield acceleration experiment worldwide. The facility is located in the former CNGS area at CERN and will include a proton, laser and electron beam line merging in a 10 m long plasma cell, which is followed by the experimental diagnostics. In the first phase of the AWAKE physics program, which started at the end of 2016, the effect of the plasma on a high energy proton beam will be studied. A proton bunch is expected to experience the so called self-modulation instability, which leads to the creation of micro-bunches within the long proton bunch. The plasma channel is created in a rubidium vapor via field ionization by a TW laser pulse. This laser beam has to overlap with the proton beam over the full length of the plasma cell, resulting in tight requirements for the stability of the proton beam at the plasma cell in the order of ~ 0.1 mm. In this paper the beam commissioning results of the ~810 m long transfer line for proton bunches with 3·10¹¹ protons/bunch and a momentum of 400 GeV/c will be presented with a focus on the challenges of the parallel operation of the laser and proton beam.

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TUPIK086

Modelling the Radioactivity Induced by Slow-Extraction Losses in the CERN SPS

1897

M.A. Fraser, D. Björkman, K. Cornelis, B. Goddard, V. Kain, P.M. Schicho, C. Theis, H. Vincke
CERN, Geneva, Switzerland

Resonant slow extraction is used to provide an intense quasi-DC flux of high-energy protons for the Fixed Target (FT) physics programme at the CERN Super Proton Synchrotron (SPS). The unavoidable beam loss intrinsic to the extraction process activates the extraction region and its equipment. Although the radiation dose to equipment has an impact on availability, the cool-down times required to limit dose to the personnel carrying-out maintenance of the accelerator also pose important restrictions, and ultimately limit the number of protons on target. In order to understand how the extracted proton flux affects the build-up and subsequent cool-down of the induced activation, a model based on a simple empirical relationship has been developed and shown to predict the measured radioactive decay at ionisation chambers located along the extraction region. In this contribution, the empirical model is described, its strengths and limitations discussed, and its application as a predictive tool for estimating cool-down times as a function of extracted proton flux demonstrated.

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TUPVA020

The LHC Injectors Upgrade (LIU) Project at CERN: Ion Injector Chain

2089

H. Bartosik, S.C.P. Albright, M.E. Angoletta, G. Bellodi, N. Biancacci, T. Bohl, J. Coupard, H. Damerau, A. Funken, B. Goddard, S. Hancock, K. Hanke, A. Huschauer, J.M. Jowett, V. Kain, D. Küchler, D. Manglunki, M. Meddahi, G. Rumolo, R. Scrivens, E.N. Shaposhnikova, V. Toivanen, F.J.C. Wenander
CERN, Geneva, Switzerland

The LHC injector chain for Pb-ion beams at CERN consists of Linac3, the accumulator ring LEIR, the PS and the SPS. In the context of the LHC injectors upgrade (LIU) project an intense program of machine development studies has been performed in the last two years to maximise the intensity of Pb-ion beams at LHC injection. In this paper we present an analysis of the operational performance achieved so far, with the goal of 1) identifying the remaining performance bottlenecks along the chain and possible areas for improvement, and 2) to optimize the Pb-ion beam production scheme for the High Luminosity (HL-) LHC era. A consistent set of beam parameters for the HL-LHC era has been established taking into account the already achieved improvements as well as foreseen upgrades still to be implemented, such as slip stacking in the SPS.

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TUPVA126

The SPS Beam Dump Facility

2389

M. Lamont, G. Arduini, M. Battistin, M. Brugger, M. Calviani, F. B. Dos Santos Pedrosa, M.A. Fraser, L. Gatignon, S.S. Gilardoni, B. Goddard, J.L. Grenard, C. Heßler, R. Jacobsson, V. Kain, K. Kershaw, E. Lopez Sola, J.A. Osborne, A. Perillo-Marcone, H. Vincke
CERN, Geneva, Switzerland

The proposed SPS beam dump facility (BDF) is a fixed-target facility foreseen to be situated at the North Area of the SPS. Beam dump in this context implies a target aimed at absorbing the majority of incident protons and containing most of the cascade generated by the primary beam interaction. The aim is a general purpose fixed target facility, which in the initial phase is aimed at the Search for Hidden Particles (SHiP) experiment. Feasibility studies are ongoing at CERN to address the key challenges of the facility. These challenges include: slow resonant extraction from the SPS; a target that has the two-fold objective of producing charged mesons as well as stopping the primary proton beam; and radiation protection considerations related to primary proton beam with a power of around 355 kW. The aim of the project is to complete the key technical feasibility studies in time for the European Strategy for Particle Physics (ESPP) update foreseen in 2020. This is in conjunction with the recommendation by the CERN Research Board to the SHiP experiment to prepare a comprehensive design study as input to the ESPP.

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TUPVA128

Performance of the CERN Injector Complex and Transmission Studies into the LHC during the Second Proton-Lead Run

2395

R. Alemany-Fernández, S.C.P. Albright, M.E. Angoletta, J. Axensalva, W. Bartmann, H. Bartosik, P. Baudrenghien, G. Bellodi, A. Blas, T. Bohl, E. Carlier, S. Cettour-Cave, K. Cornelis, H. Damerau, A. Findlay, S.S. Gilardoni, S. Hancock, A. Huschauer, M.A. Jebramcik, S. Jensen, J.M. Jowett, V. Kain, D. Küchler, A.M. Lombardi, D. Manglunki, T. Mertens, M. O'Neil, S. Pasinelli, Á. Saá Hernández, M. Schaumann, R. Scrivens, R. Steerenberg, H. Timko, V. Toivanen, G. Tranquille, F.M. Velotti, F.J.C. Wenander, J. Wenninger
CERN, Geneva, Switzerland

The LHC performance during the proton-lead run in 2016 fully relied on a permanent monitoring and systematic improvement of the beam quality in all the injectors. The beam production and characteristics are explained in this paper, together with the improvements realized during the run from the source up to the flat top of the LHC. Transmission studies from one accelerator to the next as well as beam quality evolution studies during the cycle at each accelerator, have been carried out and are summarized in this paper. In 2016, the LHC had to deliver the beams to the experiments at two different energies, 4 Z TeV and 6.5 Z TeV. The properties of the beams at these two energies are also presented

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WEPVA110

Analysis and Operational Feedback on the New Design of the High Energy Beam Dump in the CERN SPS

3524

P. Rios Rodriguez, J.A. Briz Monago, M. Calviani, K. Cornelis, S. De Man, R. Esposito, S.S. Gilardoni, B. Goddard, J.L. Grenard, D. Grenier, M. Grieco, J. Humbert, V. Kain, F.M. Leaux, C. Pasquino, A. Perillo-Marcone, J.R.F. Poujol, S. Sgobba, D. Steyart, F.M. Velotti, V. Vlachoudis
CERN, Geneva, Switzerland

CERN's Super Proton Synchrotron (SPS) high-energy internal dump (Target Internal Dump Vertical Graphite, known as TIDVG) is required to intercept beams from 10² to 450 GeV. The equipment installed in 2014 (TIDVG#3) featured an absorbing core composed of different materials surrounded by a water-cooled copper jacket, which hold the UHV of the machine. An inspection of a previous equipment (TIDVG#2) in 2013 revealed significant beam induced damage to the aluminium section of the dump, which required imposing operational limitations to minimise the risk of reproducing this phenomenon. Additionally, in 2016 a vacuum leak was detected in the dump assembly, which imposed further limitations, i.e. a reduction of the beam intensity that could be dumped per SPS supercycle. This paper presents a new design (TIDVG#4), which focuses on improving the operational robustness of the device. Moreover, thanks to the added instrumentation, a careful analysis of its performance (both experimentally and during operation) will be possible. These studies will help validating technical solutions for the design of the future SPS dump to be installed during CERN's Long Shutdown 2 in 2020 (TIDVG#5).

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THPAB049

Progress in the Understanding of the Performance Limitations in the CERN Low Energy Ion Ring

3819

A. Huschauer, H. Bartosik, S. Hancock, V. Kain
CERN, Geneva, Switzerland

The performance of heavy ion beams in the CERN Low Energy Ion Ring is mainly limited by beam loss occuring during the radio-frequency capture and the first part of acceleration. Since October 2015, the driving mechanism of these losses has been studied in detail and an interplay of direct space charge forces and excited betatron resonances was identified as the most plausible explanation of the phenomenon. In this paper we summarize the current understanding of the loss mechanism by presenting recent experimental and simulation studies. We discuss strategies to mitigate beam loss and further improve the performance of the accelerator in the future.

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THPAB146

Investigation of the Remanent Field of the SPS Main Dipoles and Possible Solutions for Machine Operation

4069

F.M. Velotti, H. Bartosik, J. Bauche, M.C.L. Buzio, K. Cornelis, M.A. Fraser, V. Kain
CERN, Geneva, Switzerland

The CERN Super Proton Synchrotron (SPS) provides different types of beams at different extraction energies. The main magnets of the SPS are regulated with a current loop, but it has turned out that hysteresis effects from the main dipoles have a significant impact on reproducibility and hence efficiency and availability. Beam and machine parameters were found to depend on the programmed sequence of magnetic cycles - the so-called super cycle - representing the production of the different beams. The scientific program of the SPS requires frequent changes of the supercycle composition and the effect of the main magnet hysteresis has to be understood, modelled and used in accelerator control system. This paper summarises the first main field measurements carried out with the currently available systems during operational conditions as well as measurements of vital machine and beam parameters as a function of the super cycle composition. Finally, ideas will be presented to provide reproducibility by automatically correcting different parameters taking the magnetic history of the main magnets into account.

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THPAB147

Automatic Local Aperture Measurements in the SPS

4073

V. Kain, H. Bartosik, S. Cettour Cave, K. Cornelis, F.M. Velotti
CERN, Geneva, Switzerland

The CERN SPS (Super Proton Synchrotron) serves as LHC injector and provides beam for the North Area fixed target experiments. It is equipped with flat vacuum chambers to accommodate the large horizontal beam size required during transition crossing and slow extraction. At low energy, the vertical acceptance becomes critical with high intensity large emittance fixed target beams. Optimizing the vertical available aperture is a key ingredient to optimize transmission and reduce activation around the ring. Aperture measurements are routinely carried out after each shutdown. Global vertical aperture measurements are followed by detailed bump scans at the locations with the loss peaks. During the 2016 run a tool was developed to provide an automated local aperture scan around the entire ring. This allowed to establish detailed reference measurements of the vertical aperture and identify directly the SPS aperture bottlenecks. The methodology applied for the scans will be briefly described in this paper and the analysis discussed. Finally, the 2016 SPS measured vertical aperture will be presented and compared to the results obtained with the previous method.

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