IPAC2016 - List of Authors (Fraser, M.A.)

Paper	Title	Page
TUPMR023	First Operational Experience of HIE-Isolde	1284
	J.A. Rodriguez, N. Bidault, E. Bravin, R. Catherall, E. Fadakis, P. Fernier, M.A. Fraser, M.J. Garcia Borge, K. Hanke, K. Johnston, Y. Kadi, M. Kowalska, M.L. Lozano Benito, E. Matli, S. Sadovich, E. Siesling, W. Venturini Delsolaro, F.J.C. Wenander CERN, Geneva, Switzerland M. Huyse, P. Van Duppen KU Leuven, Leuven, Belgium J. Pakarinen JYFL, Jyväskylä, Finland E. Rapisarda PSI, Villigen PSI, Switzerland M. Zielinska Warsaw University, Warsaw, Poland
	The High Intensity and Energy ISOLDE project (HIE-ISOLDE)* is a major upgrade of the ISOLDE facility at CERN. The energy range of the post-accelerator will be extended from 2.85 MeV/u to 9.3 MeV/u for beams with A/q = 4.5 (and to 14.3 MeV/u for A/q = 2.5) once all the cryomodules of the superconducting accelerator are in place. The project has been divided into different phases, the first of which (phase 1a) finished in October 2015 after the hardware and beam commissioning were completed*. The physics campaign followed with the delivery of both radioactive and stable beams to two different experimental stations. The characteristics of the beams (energies, intensities, time structure and beam contaminants) and the plans for the next experimental campaign will be discussed in this paper. The HIE-ISOLDE Project, Journal of Physics: Conference Series 312. HIE-ISOLDE First Commissioning Experience, IPAC'16 Beam Commissioning of the HIE-ISOLDE Post-Accelerator, IPAC'16
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMR023
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TUPMR050	Upgrades to the SPS-to-LHC Transfer Line Beam Stoppers for the LHC High-Luminosity Era	1367
	V. Kain, R. Esposito, M.A. Fraser, B. Goddard, M. Meddahi, A. Perillo Marcone, G.E. Steele, F.M. Velotti CERN, Geneva, Switzerland
	Each of the 3 km long transfer lines between the SPS and the LHC is equipped with two beam stoppers (TEDs), one at the beginning of the line and one close to the LHC injection point, which need to absorb the full transferred beam. The beam stoppers are used for setting up the SPS extractions and transfer lines with beam without having to inject into the LHC. Energy deposition and thermo-mechanical simulations have, however, shown that the TEDs will not be robust enough to safely absorb the high intensity beams foreseen for the high-luminosity LHC era. This paper will summarize the simulation results and limitations for upgrading the beam stoppers. An outline of the hardware upgrade strategy for the TEDs together with modifications to the SPS extraction interlock system to enforce intensity limitations for beam on the beam stoppers will be given.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMR050
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WEOBA01	Beam Commissioning of the HIE-ISOLDE Post-Accelerator	2045
	J.A. Rodriguez, W. Andreazza, J.M. Bibby, N. Bidault, E. Bravin, J.C. Broere, E.D. Cantero, R. Catherall, V. Cobham, M. Elias, E. Fadakis, P. Fernier, M.A. Fraser, F. Gerigk, K. Hanke, Y. Kadi, M.L. Lozano Benito, E. Matli, S. Sadovich, E. Siesling, D. Valuch, W. Venturini Delsolaro, F.J.C. Wenander, P. Zhang CERN, Geneva, Switzerland
	Phase 1a of the High Intensity and Energy ISOLDE (HIE-ISOLDE) project* was completed in 2015. The first cryomodule and two High Energy Beam Transfer lines (HEBT) were installed. In addition, many of the subsystems of the normal conducting part of the post-accelerator (REX) were renovated or refurbished. Following the hardware commissioning of the different system** and, in preparation for the start of the physics program, many tests and measurements were conducted as part of the beam commissioning program. The results of these tests and the plan for the next beam commissioning campaign are discussed in this paper. * Y. Kadi et al., "The HIE-ISOLDE Project", Journal of Physics: Conference Series 312. ** W. Venturini et al., "HIE-ISOLDE First Commissioning Experience", IPAC'16
	Slides WEOBA01 [1.437 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEOBA01
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WEPMB051	HIE-ISOLDE: First Commissioning Experience	2230
	W. Venturini Delsolaro, E. Bravin, N. Delruelle, M. Elias, J.A. Ferreira Somoza, M.A. Fraser, J. Gayde, Y. Kadi, G. Kautzmann, F. Klumb, Y. Leclercq, M. Martino, V. Parma, J.A. Rodriguez, S. Sadovich, E. Siesling, D. Smekens, L. Valdarno, D. Valuch, P. Zhang CERN, Geneva, Switzerland
	The HIE ISOLDE project [1] reached a major milestone in October 2015, with the start of the first physics run with radioactive ion beams. This achievement was the culminating point of intense months during which the first cryomodule of the HIE ISOLDE superconducting Linac and its high-energy beam transfer lines were first installed and subsequently brought into operation. Hardware commissioning campaigns were conducted in order to define the envelope of parameters within which the machine could be operated, to test and validate software and controls, and to investigate the limitations preventing the systems to reach their design performance. Methods and main results of the first commissioning of HIE ISOLDE post accelerator, including the performance of the superconducting cavities with beam, will be reviewed in this contribution.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB051
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THPMB047	Beam Dynamics Studies of the ELENA Electrostatic Transfer Lines in the Presence of Magnetic Stray Fields	3351
	J. Jentzsch, W. Bartmann, M.A. Fraser, R. Ostojić, G. Tranquille CERN, Geneva, Switzerland D. Barna University of Tokyo, Tokyo, Japan
	The ELENA (Extra Low ENergy Antiproton) ring at CERN will further decelerate antiprotons produced at the AD (Antiproton Decelerator) facility from a kinetic energy of 5.3 MeV to 100 keV. The antiprotons will be distributed through a network of electrostatic transfer lines to several experiments, which will replace the existing magnetic transfer lines. The existing experiments and limited space in the AD hall forces the new transfer lines into close proximity to the high-field solenoids used by some experiments to trap the antiprotons. The stray fields from the experimental magnets are known to perturb beam delivery and are a concern for operation at the decreased beam rigidity provided by ELENA. A study was carried out to investigate the influence of stray magnetic fields on the beam, including different ramping periods and operational scenarios. The analytical model of the fields used for simulation will be discussed. Furthermore, trajectory correction algorithms using MADX optic model of the lines have been investigated. The results of these studies as well as specifications of acceptable stray field limits and field attenuation requirements will be presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMB047
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THPMW035	Considerations on an Upgrade Possibility of the LHC Beam Dump Kicker System	3631
	M.A. Fraser, W. Bartmann, C. Bracco, L. Ducimetière, B. Goddard, T. Kramer, V. Senaj CERN, Geneva, Switzerland
	The LHC Beam Dump System (LBDS) is designed to safely dispose the circulating beams over a wide range of energy from 450 GeV up to 7 TeV, where the maximum stored energy is 362 MJ per beam. One of the most critical components of the LBDS are the extraction kickers that must reliably switch on within the 3 us particle-free abort gap. To ensure this functionality, even in the event of a power-cut, the power generator capacitors remain charged and hence the Gate Turn-Off (GTO) switch stack has to hold the full voltage throughout beam operation. The increase of the LHC collision energy to 13 TeV has increased the voltage levels at the GTO stacks and during re-commissioning an increased rate of high-voltage (HV) related issues at the level of the GTO stack was observed. Different solutions have been analysed and an improved GTO stack will be implemented. This paper also outlines the benefit of adding more kicker magnets to improve the voltage hold off issues and to improve the tolerance to missing kickers during extraction.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW035
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THPOR048	Beam Losses at CERNs PS and SPS Measured with Diamond Particle Detectors	3898
	F. Burkart, W. Bartmann, B. Dehning, E. Effinger, M.A. Fraser, B. Goddard, V. Kain, O. Stein CERN, Geneva, Switzerland E. Griesmayer CIVIDEC Instrumentation, Wien, Austria O. Stein University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Diamond particle detectors have been used in the LHC to measure fast particle losses with a nanosecond time resolution. In addition, these detectors were installed in the PS and the SPS. The detectors are mounted close to the extraction septum of the PS (transfer line to SPS) and the SPS (transfer lines TI2 and TI8 to LHC). Mainly, they monitor the losses occurring during the extraction process but the detectors are also able to measure turn-by-turn losses in the accelerators. In addition, detailed studies concerning losses due to ghost bunches were performed. This paper will describe the installed diamond detector setup, discuss the measurement results and possible loss mitigations.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR048
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THPOR051	Beam Based Measurements to Check Integrity of LHC Dump Protection Elements	3908
	C. Bracco, W. Bartmann, M.A. Fraser, B. Goddard, A. Lechner CERN, Geneva, Switzerland
	LHC operation is approaching its nominal operating goals and several upgrades are also being prepared to increase the beam intensity and brightness. In case of an asynchronous beam dump at 6.5 - 7 TeV a non-negligible fraction of the stored energy (360 MJ during nominal operation) will be deposited on the protection elements (TCDQ and TCDS) located downstream of the extraction kickers. These elements are designed to protect the machine aperture from the large amplitude particles resulting from the asynchronous dump. A number of checks and measurements with beam have been worked out to verify the integrity of these elements, after a potentially harmful event, without opening the machine vacuum. Details on measurements and simulations performed to evaluate the validity of the proposed method are presented in this paper.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR051
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THPOR052	A Beam-based Measurement of the LHC Beam Dump Kicker Waveform	3911
	M.A. Fraser, W. Bartmann, C. Bracco, E. Carlier, B. Goddard, V. Kain, N. Magnin, J.A. Uythoven, F.M. Velotti CERN, Geneva, Switzerland
	The increase of the LHC collision energy to 13 TeV after Long Shutdown 1 has doubled the operational energy range of the LHC beam dump system (LBDS) during Run 2. In preparation for the safe operation of the LHC, the waveform of the LBDS extraction kicker was measured using beam-based measurements for the first time during the machine's re-commissioning period. The measurements provide a reference for a more precise synchronisation of the dump system and abort-gap timing, and provide an independent check of the system's calibration. The precision of the beam-based technique allowed the necessary adjustments to the LBDS trigger delays to ensure the synchronous firing of the LBDS at all beam energies up to 6.5 TeV. In this paper the measurement and simulation campaign is described and the performance of the system reported.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR052
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THPOR054	Analysis of the SPS Long Term Orbit Drifts	3914
	F.M. Velotti, C. Bracco, K. Cornelis, L.N. Drøsdal, M.A. Fraser, B. Goddard, V. Kain, M. Meddahi CERN, Geneva, Switzerland E. Gianfelice-Wendt Fermilab, Batavia, Illinois, USA
	The Super Proton Synchrotron (SPS) is the last accelerator in the Large Hadron Collider (LHC) injector chain, and has to deliver the two high-intensity 450 GeV proton beams to the LHC. The transport from SPS to LHC is done through the two Transfer Lines (TL), TI2 and TI8, for Beam 1 (B1) and Beam 2 (B2) respectively. During the first LHC operation period Run 1, a long term drift of the SPS orbit was observed, causing changes in the LHC injection due to the resulting changes in the TL trajectories. This translated into longer LHC turnaround because of the necessity to periodically correct the TL trajectories in order to preserve the beam quality at injection into the LHC. Different sources for the SPS orbit drifts have been investigated: each of them can account only partially for the total orbit drift observed. In this paper, the possible sources of such drift are described, together with the simulated and measured effect they cause. Possible solutions and countermeasures are also discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR054
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THPOR055	Characterisation of the SPS Slow-extraction Parameters	3918
	F.M. Velotti, W. Bartmann, T. Bohl, C. Bracco, K. Cornelis, M.A. Fraser, B. Goddard, V. Kain, L.S. Stoel CERN, Geneva, Switzerland
	The Super Proton Synchrotron (SPS) is the last accelerator in the Large Hadron Collider (LHC) injector chain but its main users are the fixed-target experiments located in the North Area (NA). The beams, which are among the most intense circulating in the SPS, are extracted to the NA over several thousands of turns by exploiting a third-integer resonant extraction. The unavoidable losses intrinsic to such an extraction makes its optimisation one of the main priorities for operation, to reduce beam induced activation of the machine. The settings of the extraction systems, together with the tune sweep speed and the beam characteristics (momentum spread, emittance, etc.) are the parameters that can be controlled for spill and loss optimisation. In this paper, the contribution of these parameters to the slow-extraction spill quality are investigated through tracking simulations. The simulation model is compared with beam measurements and optimisations suggested.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR055
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Paper

Title

Page

First Operational Experience of HIE-Isolde

1284

J.A. Rodriguez, N. Bidault, E. Bravin, R. Catherall, E. Fadakis, P. Fernier, M.A. Fraser, M.J. Garcia Borge, K. Hanke, K. Johnston, Y. Kadi, M. Kowalska, M.L. Lozano Benito, E. Matli, S. Sadovich, E. Siesling, W. Venturini Delsolaro, F.J.C. Wenander
CERN, Geneva, Switzerland
M. Huyse, P. Van Duppen
KU Leuven, Leuven, Belgium
J. Pakarinen
JYFL, Jyväskylä, Finland
E. Rapisarda
PSI, Villigen PSI, Switzerland
M. Zielinska
Warsaw University, Warsaw, Poland

The High Intensity and Energy ISOLDE project (HIE-ISOLDE)* is a major upgrade of the ISOLDE facility at CERN. The energy range of the post-accelerator will be extended from 2.85 MeV/u to 9.3 MeV/u for beams with A/q = 4.5 (and to 14.3 MeV/u for A/q = 2.5) once all the cryomodules of the superconducting accelerator are in place. The project has been divided into different phases, the first of which (phase 1a) finished in October 2015 after the hardware and beam commissioning were completed**. The physics campaign followed with the delivery of both radioactive and stable beams to two different experimental stations. The characteristics of the beams (energies, intensities, time structure and beam contaminants) and the plans for the next experimental campaign will be discussed in this paper.
* The HIE-ISOLDE Project, Journal of Physics: Conference Series 312.
** HIE-ISOLDE First Commissioning Experience, IPAC'16
** Beam Commissioning of the HIE-ISOLDE Post-Accelerator, IPAC'16

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMR023

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TUPMR050

Upgrades to the SPS-to-LHC Transfer Line Beam Stoppers for the LHC High-Luminosity Era

1367

V. Kain, R. Esposito, M.A. Fraser, B. Goddard, M. Meddahi, A. Perillo Marcone, G.E. Steele, F.M. Velotti
CERN, Geneva, Switzerland

Each of the 3 km long transfer lines between the SPS and the LHC is equipped with two beam stoppers (TEDs), one at the beginning of the line and one close to the LHC injection point, which need to absorb the full transferred beam. The beam stoppers are used for setting up the SPS extractions and transfer lines with beam without having to inject into the LHC. Energy deposition and thermo-mechanical simulations have, however, shown that the TEDs will not be robust enough to safely absorb the high intensity beams foreseen for the high-luminosity LHC era. This paper will summarize the simulation results and limitations for upgrading the beam stoppers. An outline of the hardware upgrade strategy for the TEDs together with modifications to the SPS extraction interlock system to enforce intensity limitations for beam on the beam stoppers will be given.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMR050

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WEOBA01

Beam Commissioning of the HIE-ISOLDE Post-Accelerator

2045

J.A. Rodriguez, W. Andreazza, J.M. Bibby, N. Bidault, E. Bravin, J.C. Broere, E.D. Cantero, R. Catherall, V. Cobham, M. Elias, E. Fadakis, P. Fernier, M.A. Fraser, F. Gerigk, K. Hanke, Y. Kadi, M.L. Lozano Benito, E. Matli, S. Sadovich, E. Siesling, D. Valuch, W. Venturini Delsolaro, F.J.C. Wenander, P. Zhang
CERN, Geneva, Switzerland

Phase 1a of the High Intensity and Energy ISOLDE (HIE-ISOLDE) project* was completed in 2015. The first cryomodule and two High Energy Beam Transfer lines (HEBT) were installed. In addition, many of the subsystems of the normal conducting part of the post-accelerator (REX) were renovated or refurbished. Following the hardware commissioning of the different system** and, in preparation for the start of the physics program, many tests and measurements were conducted as part of the beam commissioning program. The results of these tests and the plan for the next beam commissioning campaign are discussed in this paper.
* Y. Kadi et al., "The HIE-ISOLDE Project", Journal of Physics: Conference Series 312.
** W. Venturini et al., "HIE-ISOLDE First Commissioning Experience", IPAC'16

Slides WEOBA01 [1.437 MB]

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEOBA01

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WEPMB051

HIE-ISOLDE: First Commissioning Experience

2230

W. Venturini Delsolaro, E. Bravin, N. Delruelle, M. Elias, J.A. Ferreira Somoza, M.A. Fraser, J. Gayde, Y. Kadi, G. Kautzmann, F. Klumb, Y. Leclercq, M. Martino, V. Parma, J.A. Rodriguez, S. Sadovich, E. Siesling, D. Smekens, L. Valdarno, D. Valuch, P. Zhang
CERN, Geneva, Switzerland

The HIE ISOLDE project [1] reached a major milestone in October 2015, with the start of the first physics run with radioactive ion beams. This achievement was the culminating point of intense months during which the first cryomodule of the HIE ISOLDE superconducting Linac and its high-energy beam transfer lines were first installed and subsequently brought into operation. Hardware commissioning campaigns were conducted in order to define the envelope of parameters within which the machine could be operated, to test and validate software and controls, and to investigate the limitations preventing the systems to reach their design performance. Methods and main results of the first commissioning of HIE ISOLDE post accelerator, including the performance of the superconducting cavities with beam, will be reviewed in this contribution.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB051

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THPMB047

Beam Dynamics Studies of the ELENA Electrostatic Transfer Lines in the Presence of Magnetic Stray Fields

3351

J. Jentzsch, W. Bartmann, M.A. Fraser, R. Ostojić, G. Tranquille
CERN, Geneva, Switzerland
D. Barna
University of Tokyo, Tokyo, Japan

The ELENA (Extra Low ENergy Antiproton) ring at CERN will further decelerate antiprotons produced at the AD (Antiproton Decelerator) facility from a kinetic energy of 5.3 MeV to 100 keV. The antiprotons will be distributed through a network of electrostatic transfer lines to several experiments, which will replace the existing magnetic transfer lines. The existing experiments and limited space in the AD hall forces the new transfer lines into close proximity to the high-field solenoids used by some experiments to trap the antiprotons. The stray fields from the experimental magnets are known to perturb beam delivery and are a concern for operation at the decreased beam rigidity provided by ELENA. A study was carried out to investigate the influence of stray magnetic fields on the beam, including different ramping periods and operational scenarios. The analytical model of the fields used for simulation will be discussed. Furthermore, trajectory correction algorithms using MADX optic model of the lines have been investigated. The results of these studies as well as specifications of acceptable stray field limits and field attenuation requirements will be presented.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMB047

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THPMW035

Considerations on an Upgrade Possibility of the LHC Beam Dump Kicker System

3631

M.A. Fraser, W. Bartmann, C. Bracco, L. Ducimetière, B. Goddard, T. Kramer, V. Senaj
CERN, Geneva, Switzerland

The LHC Beam Dump System (LBDS) is designed to safely dispose the circulating beams over a wide range of energy from 450 GeV up to 7 TeV, where the maximum stored energy is 362 MJ per beam. One of the most critical components of the LBDS are the extraction kickers that must reliably switch on within the 3 us particle-free abort gap. To ensure this functionality, even in the event of a power-cut, the power generator capacitors remain charged and hence the Gate Turn-Off (GTO) switch stack has to hold the full voltage throughout beam operation. The increase of the LHC collision energy to 13 TeV has increased the voltage levels at the GTO stacks and during re-commissioning an increased rate of high-voltage (HV) related issues at the level of the GTO stack was observed. Different solutions have been analysed and an improved GTO stack will be implemented. This paper also outlines the benefit of adding more kicker magnets to improve the voltage hold off issues and to improve the tolerance to missing kickers during extraction.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW035

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THPOR048

Beam Losses at CERNs PS and SPS Measured with Diamond Particle Detectors

3898

F. Burkart, W. Bartmann, B. Dehning, E. Effinger, M.A. Fraser, B. Goddard, V. Kain, O. Stein
CERN, Geneva, Switzerland
E. Griesmayer
CIVIDEC Instrumentation, Wien, Austria
O. Stein
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Diamond particle detectors have been used in the LHC to measure fast particle losses with a nanosecond time resolution. In addition, these detectors were installed in the PS and the SPS. The detectors are mounted close to the extraction septum of the PS (transfer line to SPS) and the SPS (transfer lines TI2 and TI8 to LHC). Mainly, they monitor the losses occurring during the extraction process but the detectors are also able to measure turn-by-turn losses in the accelerators. In addition, detailed studies concerning losses due to ghost bunches were performed. This paper will describe the installed diamond detector setup, discuss the measurement results and possible loss mitigations.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR048

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THPOR051

Beam Based Measurements to Check Integrity of LHC Dump Protection Elements

3908

C. Bracco, W. Bartmann, M.A. Fraser, B. Goddard, A. Lechner
CERN, Geneva, Switzerland

LHC operation is approaching its nominal operating goals and several upgrades are also being prepared to increase the beam intensity and brightness. In case of an asynchronous beam dump at 6.5 - 7 TeV a non-negligible fraction of the stored energy (360 MJ during nominal operation) will be deposited on the protection elements (TCDQ and TCDS) located downstream of the extraction kickers. These elements are designed to protect the machine aperture from the large amplitude particles resulting from the asynchronous dump. A number of checks and measurements with beam have been worked out to verify the integrity of these elements, after a potentially harmful event, without opening the machine vacuum. Details on measurements and simulations performed to evaluate the validity of the proposed method are presented in this paper.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR051

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THPOR052

A Beam-based Measurement of the LHC Beam Dump Kicker Waveform

3911

M.A. Fraser, W. Bartmann, C. Bracco, E. Carlier, B. Goddard, V. Kain, N. Magnin, J.A. Uythoven, F.M. Velotti
CERN, Geneva, Switzerland

The increase of the LHC collision energy to 13 TeV after Long Shutdown 1 has doubled the operational energy range of the LHC beam dump system (LBDS) during Run 2. In preparation for the safe operation of the LHC, the waveform of the LBDS extraction kicker was measured using beam-based measurements for the first time during the machine's re-commissioning period. The measurements provide a reference for a more precise synchronisation of the dump system and abort-gap timing, and provide an independent check of the system's calibration. The precision of the beam-based technique allowed the necessary adjustments to the LBDS trigger delays to ensure the synchronous firing of the LBDS at all beam energies up to 6.5 TeV. In this paper the measurement and simulation campaign is described and the performance of the system reported.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR052

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THPOR054

Analysis of the SPS Long Term Orbit Drifts

3914

F.M. Velotti, C. Bracco, K. Cornelis, L.N. Drøsdal, M.A. Fraser, B. Goddard, V. Kain, M. Meddahi
CERN, Geneva, Switzerland
E. Gianfelice-Wendt
Fermilab, Batavia, Illinois, USA

The Super Proton Synchrotron (SPS) is the last accelerator in the Large Hadron Collider (LHC) injector chain, and has to deliver the two high-intensity 450 GeV proton beams to the LHC. The transport from SPS to LHC is done through the two Transfer Lines (TL), TI2 and TI8, for Beam 1 (B1) and Beam 2 (B2) respectively. During the first LHC operation period Run 1, a long term drift of the SPS orbit was observed, causing changes in the LHC injection due to the resulting changes in the TL trajectories. This translated into longer LHC turnaround because of the necessity to periodically correct the TL trajectories in order to preserve the beam quality at injection into the LHC. Different sources for the SPS orbit drifts have been investigated: each of them can account only partially for the total orbit drift observed. In this paper, the possible sources of such drift are described, together with the simulated and measured effect they cause. Possible solutions and countermeasures are also discussed.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR054

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THPOR055

Characterisation of the SPS Slow-extraction Parameters

3918

F.M. Velotti, W. Bartmann, T. Bohl, C. Bracco, K. Cornelis, M.A. Fraser, B. Goddard, V. Kain, L.S. Stoel
CERN, Geneva, Switzerland

The Super Proton Synchrotron (SPS) is the last accelerator in the Large Hadron Collider (LHC) injector chain but its main users are the fixed-target experiments located in the North Area (NA). The beams, which are among the most intense circulating in the SPS, are extracted to the NA over several thousands of turns by exploiting a third-integer resonant extraction. The unavoidable losses intrinsic to such an extraction makes its optimisation one of the main priorities for operation, to reduce beam induced activation of the machine. The settings of the extraction systems, together with the tune sweep speed and the beam characteristics (momentum spread, emittance, etc.) are the parameters that can be controlled for spill and loss optimisation. In this paper, the contribution of these parameters to the slow-extraction spill quality are investigated through tracking simulations. The simulation model is compared with beam measurements and optimisations suggested.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR055

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