IPAC2019 - List of Authors (Velotti, F.M.)

Paper	Title	Page
WEPMP027	Update on Beam Transfer Line Design for the SPS Beam Dump Facility	2375
	Y. Dutheil, J. Bauche, L.A. Dougherty, M.A. Fraser, B. Goddard, C. Heßler, V. Kain, J. Kurdej, J.A. Uythoven, F.M. Velotti CERN, Meyrin, Switzerland
	The SPS Beam Dump Facility (BDF) being studied as part of the Physics Beyond Colliders (PBC) CERN project has recently reached an important milestone with the completion of the comprehensive feasibility study. The BDF is a proposed fixed target facility to be installed in the SPS North Area, to accommodate experiments such as SHiP (Search for Hidden Particles), which is most notably aiming at studying hidden sector particles. This experiment requires a high intensity slowly extracted 400 GeV proton beam with 4·10¹³ protons per 1 s spill to achieve 4·10¹⁹ protons on target per year. The extraction and transport scheme will make use of the first 600 m of the existing North Area extraction line. This contribution presents the status of the design work of the new transfer line and discusses the challenges identified. Aperture studies and failure scenarios are treated and the results discussed. In particular, interlock systems aiming at protecting critical components against the uncontrolled loss of the high energy proton beam are considered. We also present the latest results and implications of the design of a new laminated Lambertson splitter magnet to provide fast switching between the current North Area experiments and the BDF.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP027
About •	paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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WEPMP028	Crystal for Slow Extraction Loss-Reduction of the SPS Electrostatic Septum	2379
	L.S. Esposito, P. Bestman, M.E.J. Butcher, M. Calviani, M. Di Castro, M. Donzé, M.A. Fraser, M. Garattini, Y. Gavrikov, S.S. Gilardoni, B. Goddard, V. Kain, J. Lendaro, A. Masi, M. Pari, J. Prieto, R. Rossi, W. Scandale, R. Seidenbinder, P. Serrano Galvez, L.S. Stoel, F.M. Velotti, V. Zhovkovska CERN, Meyrin, Switzerland F.M. Addesa, F. Iacoangeli INFN-Roma, Roma, Italy A.G. Afonin, Y.A. Chesnokov, A.A. Durum, V.A. Maisheev, Yu.E. Sandomirskiy, A.A. Yanovich IHEP, Moscow Region, Russia J.E. Borg, M. Garattini, G. Hall, T. James, M. Pesaresi Imperial College of Science and Technology, Department of Physics, London, United Kingdom A.S. Denisov, Y. Gavrikov, Yu.M. Ivanov, M.A. Koznov, L.G. Malyarenko, V. Skorobogatov PNPI, Gatchina, Leningrad District, Russia F. Galluccio INFN-Napoli, Napoli, Italy A.D. Kovalenko, A.M. Taratin JINR, Dubna, Moscow Region, Russia F. Murtas INFN/LNF, Frascati, Italy A. Natochii LAL, Orsay, France
	The use of a bent crystal was investigated in order to reduce the losses at the CERN Super Proton Synchrotron (SPS) electrostatic septa (ZS) during the slow extraction of 400 GeV protons toward the North Area. The crystal, installed a few meters upstream the ZS, bends protons that would otherwise impinge on the ZS wires. Since particle deflection with good efficiency is achieved only when the crystal lattice is aligned within ~10 urad to the trajectory of the particles (at p = 400 GeV/c), a compact goniometer was built to allow the correct angular alignment of the crystal with respect to the incoming beam with a precision of few urad. In this paper, we report on the crystal features measured during a dedicated beam test by the UA9 experimental installation in the CERN H8 beam line. Details of the goniometer and its installation are also reported. The first results achieved during dedicated Machine Development (MD) sessions are finally presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP028
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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WEPMP029	Systematic Optics Studies for the Commissioning of the AWAKE Beamline	2383
	C. Bracco, B. Goddard, I. Gorgisyan, M. Turner, F.M. Velotti, L. Verra CERN, Meyrin, Switzerland M. Aiba PSI, Villigen PSI, Switzerland
	The commissioning of the AWAKE electron beam line was successfully completed in 2018. Despite a modest length of about 15 m, this low-energy line is quite complex and several iterations were needed before finding satisfactory agreement between the model and the measurements. The work allowed to precisely predict the size and positioning of the electron beam at the merging point with the protons inside the plasma cell, where no direct measurement is possible. All the key aspects and corrections which had to be included in the model, precautions and systematic checks to apply for the correct setup of the line are presented. The sensitivity of the ~18 MeV electron beam to various perturbations, like different initial optics parameters and beam conditions, energy jitter and drifts, earth’s magnetic field etc., is described.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP029
About •	paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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WEPMP030	LHC Injection Losses and Trajectories During Run 1 and 2 and Outlook to Injection of HL-LHC Beams	2387
	W. Bartmann, C. Bracco, B. Goddard, F.M. Velotti, J. Wenninger CERN, Meyrin, Switzerland
	The LHC turn-around time is impacted by the control of injection losses and trajectories. While shot-to-shot trajectory variations dominated the injection efficiency during LHC Run 1, several improvements of hardware and operational settings allowed for a high rate of successful injections during Run 2. Injection losses and trajectories are analysed and presented for the high intensity proton runs, as well as for different beam types used from the injectors. Based on this analysis, an outlook is shown for the HL-LHC era, where double the bunch intensity will have to be injected.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP030
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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WEPMP031	SPS Slow Extraction Losses and Activation: Update on Recent Improvements	2391
	M.A. Fraser, B. Balhan, H. Bartosik, J. Bernhard, C. Bertone, D. Björkman, J.C.C.M. Borburgh, M. Brugger, N. Charitonidis, N. Conan, K. Cornelis, Y. Dutheil, L.S. Esposito, R. Garcia Alia, L. Gatignon, C.M. Genton, B. Goddard, C. Heßler, Y. Kadi, V. Kain, A. Mereghetti, M. Pari, M. Patecki, J. Prieto, S. Redaelli, F. Roncarolo, R. Rossi, W. Scandale, N. Solieri, J. Spanggaard, O. Stein, L.S. Stoel, F.M. Velotti, H. Vincke CERN, Meyrin, Switzerland D. Barna, K. Brunner Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary
	Annual high intensity requests of over 10¹⁹ protons on target (POT) from the CERN Super Proton Synchrotron (SPS) Fixed Target (FT) physics program continue, with the prospect of requests for even higher, unprecedented levels in the coming decade. A concerted and multifaceted R&D effort has been launched to understand and reduce the slow extraction induced radioactivation of the SPS and to anticipate future experimental proposals, such as SHiP* at the SPS Beam Dump Facility (BDF)*, which will request an additional 4·10¹⁹ POT per year. In this contribution, we report on operational improvements and recent advances that have been made to significantly reduce the slow extraction losses, by up to a factor of 3, with the deployment of new extraction concepts, including passive and active (thin, bent crystal) diffusers and extraction on the third-integer resonance with octupoles. In light of the successful tests of the prototype extraction loss reduction schemes, an outlook and implications for future SPS FT operation will be presented. A. Golutvin et al., Rep. CERN-SPSC-2015-016 (SPSC-P-350), CERN, Geneva, Switzerland, Apr. 2015. ** M. Lamont et al., Rep. CERN-PBC-REPORT-2018-001, CERN, Geneva, Switzerland, 11 Dec 2018.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP031
About •	paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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WEPMP032	Tracking Simulations of Shadowing Electrostatic Septum Wires by Means of Bent Crystals	2395
	F.M. Velotti, M.A. Fraser, B. Goddard, V. Kain, L.S. Stoel CERN, Meyrin, Switzerland
	The Super Proton Synchrotron (SPS) slow extraction is a third integer resonant extraction and hence suffers from high losses at the electrostatic septum (ZS). This is one of the main limiting factors for the maximum number of Protons On Target (POT) deliverable from the SPS to the North Area (NA). A concept to significantly reduce the extraction losses via shadowing of the electrostatic septum wires using an upstream bent crystal has been proposed in , predicting a loss reduction of up to 50% for the prototype system installed in 2018. Following the successful experimental demonstration of the concept with beam , detailed tracking simulations have been performed to fully understand the results obtained. Further insights, such as the effective ZS width and its alignment, could be deduced by exploiting the response of the extraction loss as a function of the two degrees of freedom of the crystal (position and angle). In this paper, the beam dynamics simulations are discussed together with the implementation of the bent crystal into the simulation framework. A comparison with measurements is presented before proposals for new configurations and parameters are discussed. F.M. Velotti, et al., "Reduction of Resonant Slow Extraction Losses…", IPAC’18. ** F.M. Velotti, M.A. Fraser, et al., "Experimental SPS Slow Extraction Loss Reduction…", this conf.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP032
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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WEPMP033	Slow Extraction Loss Reduction With Octupoles at the CERN SPS	2399
	L.S. Stoel, H. Bartosik, M. Benedikt, M.A. Fraser, B. Goddard, V. Kain, F.M. Velotti CERN, Meyrin, Switzerland
	The powering of octupoles during third-integer resonant slow extraction has been studied and recently tested with beam at the CERN Super Proton Synchrotron (SPS) in order to increase the extraction efficiency and reduce the induced radioactivity of the extraction straight. The octupoles distort the particle trajectories in phase space in such a way that the extracted separatrix is folded, which decreases the particle density impinging the wires of the extraction septum at the expense of increasing the extracted beam emittance. During experimental SPS machine studies a reduction of over 40% in the specific (per extracted proton) beam loss measured at the extraction septum was demonstrated. In this paper, the prerequisite studies needed to safely but efficiently deploy the new extraction scheme in a limited time-frame are described, the experimental results are presented and an outlook is given towards the next steps to bring slow extraction with octupoles into routine operation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP033
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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WEPMP034	Characterisation of SPS Slow Extraction Spill Quality Degradation	2403
	F.M. Velotti, H. Bartosik, M.C.L. Buzio, K. Cornelis, V. Di Capua, M.A. Fraser, B. Goddard, V. Kain CERN, Meyrin, Switzerland
	The main physics users of the Super Proton Synchrotron (SPS) are the experiments installed in the North Area (NA). They are supplied with slowly extracted protons or heavy ions, exploiting a third integer slow extraction to provide a 4.8 s spill. High duty cycle and constant particle flux are the main requirements. Frequent super cycle changes induce variation of the spill macro structure which directly deteriorate the final spill quality. In this paper, the source of such an effect are investigated. Results of both beam based measurements and direct magnetic measurements on the SPS reference magnets are presented. Finally, a possible strategy to counteract this effect is discussed, in order to try to remove the super cycle changes variation as cause for spill quality deterioration.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP034
About •	paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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WEPMP035	Model and Measurements of CERN-SPS Slow Extraction Spill Re-Shaping - the Burst Mode Slow Extraction	2406
	M. Pari, M.A. Fraser, B. Goddard, V. Kain, L.S. Stoel, F.M. Velotti CERN, Meyrin, Switzerland
	The ENUBET ("Enhanced NeUtrino BEams from kaon Tagging") Project aims at reaching a new level of precision of the short-baseline neutrino cross section measurement by using an instrumented decay tunnel. The North Area (NA) experimental facility of the Super Proton Synchrotron (SPS) offers the required infrastructure for the experiment. A new slow extraction type, consisting of bursts of many consecutive millisecond spills within one macro spill, has been modeled and tested for the ENUBET Project. The burst-mode slow extraction has been tested for the first time at CERN-SPS, and MADX simulations of the process have been developed. In this paper the experimental results obtained during the test campaign are presented along with the results of the quality of the produced spill and comparing it with predictions from simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP035
About •	paper received ※ 12 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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THXXPLM2	Demonstration of Loss Reduction Using a Thin Bent Crystal to Shadow an Electrostatic Septum During Resonant Slow Extraction	3399
	F.M. Velotti, P. Bestmann, M.E.J. Butcher, M. Calviani, M. Di Castro, M. Donzé, L.S. Esposito, M.A. Fraser, M. Garattini, S.S. Gilardoni, B. Goddard, V. Kain, J. Lendaro, A. Masi, D. Mirarchi, M. Pari, J. Prieto, S. Redaelli, R. Rossi, W. Scandale, R. Seidenbinder, P. Serrano Galvez, L.S. Stoel, C. Zamantzas, V. Zhovkovska CERN, Meyrin, Switzerland F.M. Addesa, F. Iacoangeli INFN-Roma, Roma, Italy A.G. Afonin, Y.A. Chesnokov, A.A. Durum, V.A. Maisheev, Yu.E. Sandomirskiy, A.A. Yanovich IHEP, Moscow Region, Russia J.E. Borg, M. Garattini, G. Hall, T. James, M. Pesaresi Imperial College of Science and Technology, Department of Physics, London, United Kingdom A.S. Denisov, Y. Gavrikov, Yu.M. Ivanov, M.A. Koznov, L.G. Malyarenko, V. Skorobogatov PNPI, Gatchina, Leningrad District, Russia F. Galluccio INFN-Napoli, Napoli, Italy F. Murtas INFN/LNF, Frascati, Italy
	A proof-of-principle experiment demonstrating the feasibility of using a thin, bent crystal aligned upstream of an extraction septum (ES) to increase the efficiency of the third-integer resonant slow extraction process has been carried out at the CERN Super Proton Synchrotron (SPS). With the primary aim of reducing the beam loss and induced radio-activation of the SPS, the crystal was aligned to both the beam and the septum to reduce by up to 40% the beam intensity impinging the ES and increase the intensity entering the external transfer line. In this contribution, we introduce the concept and the prototype system that was installed in 2018 before reporting in detail on the dedicated program of machine development studies carried out to characterise its performance and demonstrate operational feasibility. The performance reach and compatibility with other loss reduction techniques proposed to further increase the extraction efficiency, such as phase space folding with octupoles, is discussed in view of future high intensity operation.
	Slides THXXPLM2 [1.397 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THXXPLM2
About •	paper received ※ 15 May 2019 paper accepted ※ 28 May 2019 issue date ※ 21 June 2019
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THPRB080	Automatisation of the SPS ElectroStatic Septa Alignment	4001
	S. Hirlaender ATI, Vienna, Austria M.A. Fraser, B. Goddard, V. Kain, J. Prieto, L.S. Stoel, F.M. Velotti CERN, Meyrin, Switzerland M. Szakaly Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary
	An electrostatic septum composed of 5 separate tanks is used to slow-extract the 400 GeV proton beam resonantly on the third integer resonance from the CERN SPS. The septa are all mounted on a single support structure that can move the ensemble coherently and, in addition, the internal anode and cathode of each tank can be moved independently. The septum is aligned to the beam by measuring and minimising the induced beam loss signals in the extraction region following an alignment procedure that is usually carried out manually at the beginning of each year. The large number of positional degrees of freedom complicates the procedure and until recently each tank was aligned one after the other semi-manually, typically requiring 8 hours. It is not uncommon that the septum has to be re-aligned later in the run taking time away from physics programme. To tackle this issue, a simplified beam dynamics and scattering simulation routine was developed to permit error studies with a large number of seeds to be carried out in a reasonable computation time. In this contribution, the simulation model will be described before the results of its exploitation to understand the efficacy of alignment procedures based on different optimization algorithms are discussed and compared to the present operational procedure. The effort culminated with the implementation of an automated alignment procedure based on a Powell optimisation algorithm that reduced the time needed to align the septum by over an order of magnitude.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB080
About •	paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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Paper

Title

Page

Update on Beam Transfer Line Design for the SPS Beam Dump Facility

2375

Y. Dutheil, J. Bauche, L.A. Dougherty, M.A. Fraser, B. Goddard, C. Heßler, V. Kain, J. Kurdej, J.A. Uythoven, F.M. Velotti
CERN, Meyrin, Switzerland

The SPS Beam Dump Facility (BDF) being studied as part of the Physics Beyond Colliders (PBC) CERN project has recently reached an important milestone with the completion of the comprehensive feasibility study. The BDF is a proposed fixed target facility to be installed in the SPS North Area, to accommodate experiments such as SHiP (Search for Hidden Particles), which is most notably aiming at studying hidden sector particles. This experiment requires a high intensity slowly extracted 400 GeV proton beam with 4·10¹³ protons per 1 s spill to achieve 4·10¹⁹ protons on target per year. The extraction and transport scheme will make use of the first 600 m of the existing North Area extraction line. This contribution presents the status of the design work of the new transfer line and discusses the challenges identified. Aperture studies and failure scenarios are treated and the results discussed. In particular, interlock systems aiming at protecting critical components against the uncontrolled loss of the high energy proton beam are considered. We also present the latest results and implications of the design of a new laminated Lambertson splitter magnet to provide fast switching between the current North Area experiments and the BDF.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP027

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPMP028

Crystal for Slow Extraction Loss-Reduction of the SPS Electrostatic Septum

2379

L.S. Esposito, P. Bestman, M.E.J. Butcher, M. Calviani, M. Di Castro, M. Donzé, M.A. Fraser, M. Garattini, Y. Gavrikov, S.S. Gilardoni, B. Goddard, V. Kain, J. Lendaro, A. Masi, M. Pari, J. Prieto, R. Rossi, W. Scandale, R. Seidenbinder, P. Serrano Galvez, L.S. Stoel, F.M. Velotti, V. Zhovkovska
CERN, Meyrin, Switzerland
F.M. Addesa, F. Iacoangeli
INFN-Roma, Roma, Italy
A.G. Afonin, Y.A. Chesnokov, A.A. Durum, V.A. Maisheev, Yu.E. Sandomirskiy, A.A. Yanovich
IHEP, Moscow Region, Russia
J.E. Borg, M. Garattini, G. Hall, T. James, M. Pesaresi
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
A.S. Denisov, Y. Gavrikov, Yu.M. Ivanov, M.A. Koznov, L.G. Malyarenko, V. Skorobogatov
PNPI, Gatchina, Leningrad District, Russia
F. Galluccio
INFN-Napoli, Napoli, Italy
A.D. Kovalenko, A.M. Taratin
JINR, Dubna, Moscow Region, Russia
F. Murtas
INFN/LNF, Frascati, Italy
A. Natochii
LAL, Orsay, France

The use of a bent crystal was investigated in order to reduce the losses at the CERN Super Proton Synchrotron (SPS) electrostatic septa (ZS) during the slow extraction of 400 GeV protons toward the North Area. The crystal, installed a few meters upstream the ZS, bends protons that would otherwise impinge on the ZS wires. Since particle deflection with good efficiency is achieved only when the crystal lattice is aligned within ~10 urad to the trajectory of the particles (at p = 400 GeV/c), a compact goniometer was built to allow the correct angular alignment of the crystal with respect to the incoming beam with a precision of few urad. In this paper, we report on the crystal features measured during a dedicated beam test by the UA9 experimental installation in the CERN H8 beam line. Details of the goniometer and its installation are also reported. The first results achieved during dedicated Machine Development (MD) sessions are finally presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP028

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPMP029

Systematic Optics Studies for the Commissioning of the AWAKE Beamline

2383

C. Bracco, B. Goddard, I. Gorgisyan, M. Turner, F.M. Velotti, L. Verra
CERN, Meyrin, Switzerland
M. Aiba
PSI, Villigen PSI, Switzerland

The commissioning of the AWAKE electron beam line was successfully completed in 2018. Despite a modest length of about 15 m, this low-energy line is quite complex and several iterations were needed before finding satisfactory agreement between the model and the measurements. The work allowed to precisely predict the size and positioning of the electron beam at the merging point with the protons inside the plasma cell, where no direct measurement is possible. All the key aspects and corrections which had to be included in the model, precautions and systematic checks to apply for the correct setup of the line are presented. The sensitivity of the ~18 MeV electron beam to various perturbations, like different initial optics parameters and beam conditions, energy jitter and drifts, earth’s magnetic field etc., is described.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP029

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paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPMP030

LHC Injection Losses and Trajectories During Run 1 and 2 and Outlook to Injection of HL-LHC Beams

2387

W. Bartmann, C. Bracco, B. Goddard, F.M. Velotti, J. Wenninger
CERN, Meyrin, Switzerland

The LHC turn-around time is impacted by the control of injection losses and trajectories. While shot-to-shot trajectory variations dominated the injection efficiency during LHC Run 1, several improvements of hardware and operational settings allowed for a high rate of successful injections during Run 2. Injection losses and trajectories are analysed and presented for the high intensity proton runs, as well as for different beam types used from the injectors. Based on this analysis, an outlook is shown for the HL-LHC era, where double the bunch intensity will have to be injected.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP030

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPMP031

SPS Slow Extraction Losses and Activation: Update on Recent Improvements

2391

M.A. Fraser, B. Balhan, H. Bartosik, J. Bernhard, C. Bertone, D. Björkman, J.C.C.M. Borburgh, M. Brugger, N. Charitonidis, N. Conan, K. Cornelis, Y. Dutheil, L.S. Esposito, R. Garcia Alia, L. Gatignon, C.M. Genton, B. Goddard, C. Heßler, Y. Kadi, V. Kain, A. Mereghetti, M. Pari, M. Patecki, J. Prieto, S. Redaelli, F. Roncarolo, R. Rossi, W. Scandale, N. Solieri, J. Spanggaard, O. Stein, L.S. Stoel, F.M. Velotti, H. Vincke
CERN, Meyrin, Switzerland
D. Barna, K. Brunner
Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary

Annual high intensity requests of over 10¹⁹ protons on target (POT) from the CERN Super Proton Synchrotron (SPS) Fixed Target (FT) physics program continue, with the prospect of requests for even higher, unprecedented levels in the coming decade. A concerted and multifaceted R&D effort has been launched to understand and reduce the slow extraction induced radioactivation of the SPS and to anticipate future experimental proposals, such as SHiP* at the SPS Beam Dump Facility (BDF)**, which will request an additional 4·10¹⁹ POT per year. In this contribution, we report on operational improvements and recent advances that have been made to significantly reduce the slow extraction losses, by up to a factor of 3, with the deployment of new extraction concepts, including passive and active (thin, bent crystal) diffusers and extraction on the third-integer resonance with octupoles. In light of the successful tests of the prototype extraction loss reduction schemes, an outlook and implications for future SPS FT operation will be presented.
* A. Golutvin et al., Rep. CERN-SPSC-2015-016 (SPSC-P-350), CERN, Geneva, Switzerland, Apr. 2015.
** M. Lamont et al., Rep. CERN-PBC-REPORT-2018-001, CERN, Geneva, Switzerland, 11 Dec 2018.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP031

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPMP032

Tracking Simulations of Shadowing Electrostatic Septum Wires by Means of Bent Crystals

2395

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

The Super Proton Synchrotron (SPS) slow extraction is a third integer resonant extraction and hence suffers from high losses at the electrostatic septum (ZS). This is one of the main limiting factors for the maximum number of Protons On Target (POT) deliverable from the SPS to the North Area (NA). A concept to significantly reduce the extraction losses via shadowing of the electrostatic septum wires using an upstream bent crystal has been proposed in *, predicting a loss reduction of up to 50% for the prototype system installed in 2018. Following the successful experimental demonstration of the concept with beam **, detailed tracking simulations have been performed to fully understand the results obtained. Further insights, such as the effective ZS width and its alignment, could be deduced by exploiting the response of the extraction loss as a function of the two degrees of freedom of the crystal (position and angle). In this paper, the beam dynamics simulations are discussed together with the implementation of the bent crystal into the simulation framework. A comparison with measurements is presented before proposals for new configurations and parameters are discussed.
* F.M. Velotti, et al., "Reduction of Resonant Slow Extraction Losses…", IPAC’18.
** F.M. Velotti, M.A. Fraser, et al., "Experimental SPS Slow Extraction Loss Reduction…", this conf.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP032

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPMP033

Slow Extraction Loss Reduction With Octupoles at the CERN SPS

2399

L.S. Stoel, H. Bartosik, M. Benedikt, M.A. Fraser, B. Goddard, V. Kain, F.M. Velotti
CERN, Meyrin, Switzerland

The powering of octupoles during third-integer resonant slow extraction has been studied and recently tested with beam at the CERN Super Proton Synchrotron (SPS) in order to increase the extraction efficiency and reduce the induced radioactivity of the extraction straight. The octupoles distort the particle trajectories in phase space in such a way that the extracted separatrix is folded, which decreases the particle density impinging the wires of the extraction septum at the expense of increasing the extracted beam emittance. During experimental SPS machine studies a reduction of over 40% in the specific (per extracted proton) beam loss measured at the extraction septum was demonstrated. In this paper, the prerequisite studies needed to safely but efficiently deploy the new extraction scheme in a limited time-frame are described, the experimental results are presented and an outlook is given towards the next steps to bring slow extraction with octupoles into routine operation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP033

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPMP034

Characterisation of SPS Slow Extraction Spill Quality Degradation

2403

F.M. Velotti, H. Bartosik, M.C.L. Buzio, K. Cornelis, V. Di Capua, M.A. Fraser, B. Goddard, V. Kain
CERN, Meyrin, Switzerland

The main physics users of the Super Proton Synchrotron (SPS) are the experiments installed in the North Area (NA). They are supplied with slowly extracted protons or heavy ions, exploiting a third integer slow extraction to provide a 4.8 s spill. High duty cycle and constant particle flux are the main requirements. Frequent super cycle changes induce variation of the spill macro structure which directly deteriorate the final spill quality. In this paper, the source of such an effect are investigated. Results of both beam based measurements and direct magnetic measurements on the SPS reference magnets are presented. Finally, a possible strategy to counteract this effect is discussed, in order to try to remove the super cycle changes variation as cause for spill quality deterioration.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP034

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paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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WEPMP035

Model and Measurements of CERN-SPS Slow Extraction Spill Re-Shaping - the Burst Mode Slow Extraction

2406

M. Pari, M.A. Fraser, B. Goddard, V. Kain, L.S. Stoel, F.M. Velotti
CERN, Meyrin, Switzerland

The ENUBET ("Enhanced NeUtrino BEams from kaon Tagging") Project aims at reaching a new level of precision of the short-baseline neutrino cross section measurement by using an instrumented decay tunnel. The North Area (NA) experimental facility of the Super Proton Synchrotron (SPS) offers the required infrastructure for the experiment. A new slow extraction type, consisting of bursts of many consecutive millisecond spills within one macro spill, has been modeled and tested for the ENUBET Project. The burst-mode slow extraction has been tested for the first time at CERN-SPS, and MADX simulations of the process have been developed. In this paper the experimental results obtained during the test campaign are presented along with the results of the quality of the produced spill and comparing it with predictions from simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP035

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paper received ※ 12 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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THXXPLM2

Demonstration of Loss Reduction Using a Thin Bent Crystal to Shadow an Electrostatic Septum During Resonant Slow Extraction

3399

F.M. Velotti, P. Bestmann, M.E.J. Butcher, M. Calviani, M. Di Castro, M. Donzé, L.S. Esposito, M.A. Fraser, M. Garattini, S.S. Gilardoni, B. Goddard, V. Kain, J. Lendaro, A. Masi, D. Mirarchi, M. Pari, J. Prieto, S. Redaelli, R. Rossi, W. Scandale, R. Seidenbinder, P. Serrano Galvez, L.S. Stoel, C. Zamantzas, V. Zhovkovska
CERN, Meyrin, Switzerland
F.M. Addesa, F. Iacoangeli
INFN-Roma, Roma, Italy
A.G. Afonin, Y.A. Chesnokov, A.A. Durum, V.A. Maisheev, Yu.E. Sandomirskiy, A.A. Yanovich
IHEP, Moscow Region, Russia
J.E. Borg, M. Garattini, G. Hall, T. James, M. Pesaresi
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
A.S. Denisov, Y. Gavrikov, Yu.M. Ivanov, M.A. Koznov, L.G. Malyarenko, V. Skorobogatov
PNPI, Gatchina, Leningrad District, Russia
F. Galluccio
INFN-Napoli, Napoli, Italy
F. Murtas
INFN/LNF, Frascati, Italy

A proof-of-principle experiment demonstrating the feasibility of using a thin, bent crystal aligned upstream of an extraction septum (ES) to increase the efficiency of the third-integer resonant slow extraction process has been carried out at the CERN Super Proton Synchrotron (SPS). With the primary aim of reducing the beam loss and induced radio-activation of the SPS, the crystal was aligned to both the beam and the septum to reduce by up to 40% the beam intensity impinging the ES and increase the intensity entering the external transfer line. In this contribution, we introduce the concept and the prototype system that was installed in 2018 before reporting in detail on the dedicated program of machine development studies carried out to characterise its performance and demonstrate operational feasibility. The performance reach and compatibility with other loss reduction techniques proposed to further increase the extraction efficiency, such as phase space folding with octupoles, is discussed in view of future high intensity operation.

Slides THXXPLM2 [1.397 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THXXPLM2

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paper received ※ 15 May 2019 paper accepted ※ 28 May 2019 issue date ※ 21 June 2019

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THPRB080

Automatisation of the SPS ElectroStatic Septa Alignment

4001

S. Hirlaender
ATI, Vienna, Austria
M.A. Fraser, B. Goddard, V. Kain, J. Prieto, L.S. Stoel, F.M. Velotti
CERN, Meyrin, Switzerland
M. Szakaly
Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary

An electrostatic septum composed of 5 separate tanks is used to slow-extract the 400 GeV proton beam resonantly on the third integer resonance from the CERN SPS. The septa are all mounted on a single support structure that can move the ensemble coherently and, in addition, the internal anode and cathode of each tank can be moved independently. The septum is aligned to the beam by measuring and minimising the induced beam loss signals in the extraction region following an alignment procedure that is usually carried out manually at the beginning of each year. The large number of positional degrees of freedom complicates the procedure and until recently each tank was aligned one after the other semi-manually, typically requiring 8 hours. It is not uncommon that the septum has to be re-aligned later in the run taking time away from physics programme. To tackle this issue, a simplified beam dynamics and scattering simulation routine was developed to permit error studies with a large number of seeds to be carried out in a reasonable computation time. In this contribution, the simulation model will be described before the results of its exploitation to understand the efficacy of alignment procedures based on different optimization algorithms are discussed and compared to the present operational procedure. The effort culminated with the implementation of an automated alignment procedure based on a Powell optimisation algorithm that reduced the time needed to align the septum by over an order of magnitude.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB080

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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