IPAC2016 - List of Keywords (beam-losses)

Paper	Title	Other Keywords	Page
MOPMR024	A Versatile Beam Loss Monitoring System for CLIC	electron, quadrupole, background, cavity	286
	M. Kastriotou, S. Döbert, W. Farabolini, E.B. Holzer, E. Nebot Del Busto, F. Tecker CERN, Geneva, Switzerland M. Kastriotou, E. Nebot Del Busto, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom M. Kastriotou, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	The design of a potential CLIC beam loss monitoring (BLM) system presents multiple challenges. To successfully cover the 48 km of beamline, ionisation chambers and optical fibre BLMs are under investigation. The former fulfils all CLIC requirements but would need more than 40000 monitors to protect the whole facility. For the latter, the capability of reconstructing the original loss position with a multi-bunch beam pulse and multiple loss locations still needs to be quantified. Two main sources of background for beam loss measurements are identified for CLIC. The two-beam accelerator scheme introduces so-called crosstalk, i.e. detection of losses originating in one beam line by the monitors protecting the other. Moreover, electrons emitted from the inner surface of RF cavities and boosted by the high RF gradients may produce signals in neighbouring BLMs, limiting their ability to detect real beam losses. This contribution presents the results of dedicated experiments performed in the CLIC Test Facility to quantify the position resolution of optical fibre BLMs in a multi-bunch, multi-loss scenario as well as the sensitivity limitations due to crosstalk and electron field emission.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR024
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MOPMR057	Measurements using Button BPM SUM Signal	electronics, storage-ring, operation, insertion	377
	W.X. Cheng, K. Ha, J. Mead, O. Singh, G.M. Wang BNL, Upton, Long Island, New York, USA
	Modern digital BPM detectors measure not only the beam positions, four buttons SUM signal can be very helpful for machine developments and operations. At NSLS-II, BPM SUM signal has been used from commissioning stage, to investigate localized beam losses. During top-off operation, precise beam lifetime measurement within relative short period of time becomes important. With many BPMs along the ring, BPM SUM can be a much more accurate tool to measure the beam current and lifetime. BPM SUM signal shall be proportional to beam current, and it may depends on button sizes and BPM chamber geometry, cable attenuations, electronics attenuations, beam position, bunch lengths, fill pattern etc. Experience of BPM SUM signals measurements will be presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR057
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MOPMY027	Preliminary Design of High-efficiency Klystron for Pohang Accelerator Laboratory (PAL)	cavity, klystron, simulation, operation	557
	S.J. Park, J.Y. Choi, Y.D. Joo, K.R. Kim, W. Namkung, C.D. Park PAL, Pohang, Kyungbuk, Republic of Korea M.-H. Cho, J.H. Hwang, T. Seong POSTECH, Pohang, Kyungbuk, Republic of Korea
	Funding: Supported by the Ministry of Science, ICT and Future Planning of Korea. Klystrons for particle accelerators are typically designed to have narrow bandwidths with center frequencies ranging from several hundreds (e.g., 350) MHz to X-band (11.424 GHz). Output powers are from several tens of kW to ~1 MW for CW klystrons and ~100 MW for pulsed ones. The narrow-bandwidth requirement has enabled them to provide high gain (typically 40 - 50 dB) which greatly simplifies the RF drive system. Recently, especially for large-scale accelerator facilities, the klystron efficiency has become one of the most demanding issues. This is because electricity cost occupies a great portion of their operating budgets and the klystron efficiency is one of the important factors determining the electricity consumption of the whole accelerator system. In this regard, we have designed a high-efficiency klystron for use in the PLS-II and PAL XFEL at PAL. The basic scheme is to re-design the cavity system to include multi-cell output cavity. In this article, we report on our preliminary design work to determine major cavity parameters including cell frequencies, inter-cell distances, and coupling to external circuits (coupling beta).
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY027
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TUOAA01	Operation of LANSCE Linear Accelerator with Double Pulse Rate and Low Beam Losses	linac, DTL, proton, operation	1004
	Y.K. Batygin, J.S. Kolski, R.C. McCrady, L. Rybarcyk LANL, Los Alamos, New Mexico, USA
	Funding: Work supported by US DOE under contract DE-AC52-06NA25396 In 2014 LANSCE accelerator facility return to 120 Hz pulse rate operation after long period of operation at 60 Hz pulse rate. Increased capabilities require careful tuning of all components of linear accelerator. Transformation to double pulse rate resulted in re-evaluation of tuning procedures in order to meet new challenges in beam operation. The paper summarizes experimental activity on sustaining of high productivity of accelerator facility while keeping beam losses along accelerator at the low level.
	Slides TUOAA01 [14.886 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOAA01
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TUPMW014	Improved Aperture Measurements at the LHC and Results from their Application in 2015	alignment, injection, operation, insertion	1446
	P.D. Hermes, R. Bruce, M. Fiascaris, H. Garcia, M. Giovannozzi, A. Mereghetti, D. Mirarchi, E. Quaranta, S. Redaelli, B. Salvachua, G. Valentino CERN, Geneva, Switzerland R. Kwee-Hinzmann Royal Holloway, University of London, Surrey, United Kingdom E. Quaranta Politecnico/Milano, Milano, Italy
	A good knowledge of the available aperture in the LHC is essential for a safe operation due to the risk of magnet quenches or even damage in case of uncontrolled beam losses. Experimental validations of the available aperture are therefore crucial and were in the past carried out by either a collimator scan combined with beam excitations or through the use of local orbit bumps. In this paper, we show a first comparison of these methods in the same machine configuration, as well as a new very fast method based on a beam-based collimator alignment and a new faster variant of the collimator scan method. The methods are applied to the LHC operational configuration for 2015 at injection and with squeezed beams and the measured apertures are presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW014
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TUPMW023	Macroparticle-Induced Losses During 6.5 TeV LHC Operation	operation, proton, electron, luminosity	1481
	G. Papotti, M. Albert, B. Auchmann, E.B. Holzer, M.K. Kalliokoski, A. Lechner CERN, Geneva, Switzerland
	One of the major performance limitations for operating the LHC at high energy was feared to be the so called UFOs (Unidentified Falling Objects, presumably micrometer sized dust particles which lead to fast beam losses when they interact with the beam). Indeed much higher rates were observed in 2015 compared to Run 1, and about 20 fills were prematurely terminated by too high losses caused by such events. Additionally they triggered a few beam induced quenches at high energy, the first in the history of the LHC. In this paper we review the latest update on the analysis of these events, e.g. the conditioning observed during the year and possible correlations with beam and machine parameters. At the same time we also review the optimization of beam loss monitor thresholds in terms of machine protection and availability.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW023
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TUPOW038	Measurement and Control of Beam Losses Under High Average-current Operation of the Compact ERL at KEK	radiation, operation, recirculation, optics	1839
	S. Sakanaka, K. Haga, Y. Honda, H. Matsumura, T. Miyajima, T. Nogami, T. Obina, H. Sagehashi, M. Shimada, M. Yamamoto KEK, Ibaraki, Japan
	The compact ERL (cERL)* is a superconducting accelerator aimed at demonstrating excellent ERL technologies for the future light source. The cERL comprises a 5 MeV injector, a main linac, and a recirculation loop. In the cERL, production and transportation of low-emittance and high average-current beams (tentative goals: 1 mm-mrad and 10 mA) is primarily important. At this moment (in December 2015), beam currents of up to 80 uA (CW) have successfully been transported through the recirculation loop at a beam energy of 20 MeV. Before such high-current operations, we carefully tuned up the machine so that beam losses became very small. The beam losses were watched using fast beam-loss detectors and radiation monitors while absolute losses were estimated from measured radiation levels on the roof of the shield. After careful beam-optics corrections and elimination of beam halos / tails at low-energy section, we achieved the beam losses of at most a few nA level at several locations along the loop, and those below 1 nA elsewhere in the loop. We will report these results together with the result of higher-current operation which is planned early in 2016. * S. Sakanaka et al., IPAC'15, TUBC1; T. Obina et al., to be presented at IPAC'16.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW038
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WEPMW007	Validation of Off-momentum Cleaning Performance of the LHC Collimation System	proton, collimation, injection, alignment	2427
	B. Salvachua, P. Baudrenghien, R. Bruce, H. Garcia, P.D. Hermes, S. Jackson, M. Jaussi, A. Mereghetti, D. Mirarchi, S. Redaelli, H. Timko, G. Valentino, A. Valloni CERN, Geneva, Switzerland R. Kwee-Hinzmann Royal Holloway, University of London, Surrey, United Kingdom
	The LHC collimation system is designed to provide effective cleaning against losses coming from off-momentum particles, either due to un-captured beam or to an unexpected RF frequency change. For this reason the LHC is equipped with a hierarchy of collimators in IR3: primary, secondary and absorber collimators. After every collimator alignment or change of machine configuration the off-momentum cleaning efficiency is validated with loss maps at low intensity. We describe here the improved technique used in 2015 to generate such loss maps without completely dumping the beam into the collimators. The achieved performance of the collimation system for momentum cleaning is reviewed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW007
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WEPMW031	Towards Optimum Material Choices for the HL-LHC Collimator Upgrade	impedance, collimation, luminosity, simulation	2498
	E. Quaranta, A. Bertarelli, N. Biancacci, R. Bruce, F. Carra, E. Métral, S. Redaelli, A. Rossi, B. Salvant CERN, Geneva, Switzerland F. Carra Politecnico di Torino, Torino, Italy
	The first years of operation at the LHC showed that collimator material-related concerns might limit the performance. In addition, the HL-LHC upgrade will bring the accelerator beyond the nominal performance through more intense and brighter proton beams. A new generation of collimators based on advanced materials is needed to match present and new requirements. After several years of R&D on collimator materials, studying the behaviour of novel composites with properties that address different limitations of the present collimation system, solutions have been found to fulfil various upgrade challenges. This paper describes the proposed staged approach to deploy new materials in the upgraded HL-LHC collimation system. Beam tests at the CERN HiRadMat facility were also performed to benchmark simulation methods and constitutive material models.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW031
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WEPMW033	Validation of Simulation Tools for Fast Beam Failure Studies in the LHC	simulation, optics, collimation, proton	2506
	E. Quaranta, C. Bracco, R. Bruce, S. Redaelli CERN, Geneva, Switzerland
	The LHC collimation system protects passively the most sensitive machine equipment against beam losses. In particular, collimators are the last line of defense in case of single-turn failures that cannot be caught by the standard interlock system. The collimator settings are conceived to protect the machine even for very rare events, like beam abort failures with a full machine. Collimator settings are established in simulations through a dedicated tracking setup but also empirically validated by beam measurements at low intensities. A benchmark of simulations is essential for reliably estimating the response of the system for future machine configurations and beam parameters. In the paper, results are presented of tracking simulations for different optics deployed in the LHC Run II at 6.5 TeV and compared with data.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW033
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WEPOY047	LHC Collimation and Energy Deposition Studies Using Beam Delivery Simulation (BDSIM)	simulation, collimation, optics, proton	3101
	L.J. Nevay, S.T. Boogert, S.M. Gibson, R. Kwee-Hinzmann JAI, Egham, Surrey, United Kingdom R. Bruce, H. Garcia, S. Redaelli CERN, Geneva, Switzerland
	Beam Delivery Simulation (BDSIM) is a program that uses a suite of high energy physics software including Geant4, CLHEP & ROOT, that seamlessly tracks particles through accelerators and detectors utilising the full range of particles and physics processes from Geant4. A comparison of the collimator cleaning efficiency and energy deposition throughout the full length of the Large Hadron Collider (LHC) with the established SixTrack simulations of the CERN collimation group is presented. The propagation of the full hadronic showers from collimators provides unparalleled detail in energy deposition maps and these are compared with the data from beam loss monitors that measure radiation outside the magnet body.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY047
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THPMR003	Failure Modes and Beam Losses Studies in ILC Bunch Compressors and Main Linac	quadrupole, linac, cavity, cryomodule	3388
	A. Saini, N. Solyak, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Proposed International linear collider (ILC) involves high average beam power. Dealing with high average beam power and smaller beam sizes result in stringent tolerances on beam losses and therefore, extensive studies are required to investigate every possible scenarios that lead to beam losses. In this paper we discuss beam losses due to failure of critical elements in beamline for ILC bunch compressors and main linac.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR003
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THPOY032	The Dual Use of Beam Loss Monitors at FAIR-SIS100: General Diagnostics and Quench Prevention of Superconducting Magnets	ion, quadrupole, extraction, simulation	4167
	S. Damjanovic, P. Kowina, C. Omet, M. Sapinski, M. Schwickert, P.J. Spiller GSI, Darmstadt, Germany
	In view of the planned coverage of the FAIR-SIS100 synchrotron with beam loss monitors (BLMs), FLUKA studies were performed aiming at two goals: i) evaluation of the sensitivity of the LHC-IC type detectors to the potential beam losses at SIS100; ii) estimation of the BLM quench prevention threshold via the correlation between the energy deposition inside the superconducting coils and the BLM active volume. A full spectrum of ion species and energies to be accelerated with SIS100 were considered in the simulations, showing a great sensitivity to the beam losses. An interesting finding of this study was that, for the same beam loss location, the quench prevention thresholds were almost identical for all ion species/energies including protons.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY032
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THPOY044	Experimental Setup to Measure the Damage Limits of Superconducting Magnets due to Beam Impact at CERN's HiRadMat Facility	experiment, dipole, proton, target	4200
	D. Kleiven Kleiven, David, Geneva, Switzerland B. Auchmann, V. Raginel, R. Schmidt, A.P. Verweij, D. Wollmann CERN, Geneva, Switzerland
	Funding: Research supported by the High Luminosity LHC project The future upgrade of CERN's injector chain for the Large Hadron Collider (LHC) will lead to an increase of the beam brightness in the LHC. Beam absorbers are capturing missteered beams, but some limited beam impact on superconducting magnets can hardly be avoided. Therefore, it is planned to measure the damage limits of superconducting magnet components due to beam impact at CERN's HiRad- Mat facility using the 440 GeV proton beam from the Super Proton Synchrotron. Two experiments are proposed. One at ambient and one at cryogenic temperatures, where several pre-stressed stacks of LHC main dipole Nb-Ti cables and some single strands will be irradiated with varying beam intensities. The electrical integrity and the degradation of critical current will be measured after the removal from the HiRadMat facility. In the cold experiment some sample magnets will be added and the degradation of performance will be monitored online. In this contribution the experimental setup of the first experiment, including the sample container and cable stacks, is presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY044
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THPOY045	Commissioning of the Machine Protection Systems of the Large Hadron Collider Following its First Long Shutdown	operation, dipole, injection, hadron	4203
	D. Wollmann, R. Schmidt, J.A. Uythoven, J. Wenninger, M. Zerlauth CERN, Geneva, Switzerland
	During the first long shutdown of the Large Hadron Collider (LHC) extending for more than 18 months, most Machine Protection Systems (MPS) have undergone significant changes, and upgrades. A full re-commissioning of the MPS was performed at the end of the shutdown and during the LHC beam commissioning in 2015. To verify the correct functioning of all protection-relevant systems with beam, a step-wise intensity ramp-up was performed, reaching at the end of 2015 a record stored beam energy of ~280 MJ per beam, nearly 80% of the value in the design report. This contribution summarizes the results of the MPS commissioning, the intensity ramp-up and the continuous follow-up during operation, focusing mainly on near misses and false triggers and their proposed mitigations. A strategy to minimize risks during machine development periods for future operation of the LHC, when the protection parameters are modified for several tests, is discussed. The machine protection strategy for the LHC run in 2016 is presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY045
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Paper

Title

Other Keywords

Page

MOPMR024

A Versatile Beam Loss Monitoring System for CLIC

electron, quadrupole, background, cavity

286

M. Kastriotou, S. Döbert, W. Farabolini, E.B. Holzer, E. Nebot Del Busto, F. Tecker
CERN, Geneva, Switzerland
M. Kastriotou, E. Nebot Del Busto, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
M. Kastriotou, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The design of a potential CLIC beam loss monitoring (BLM) system presents multiple challenges. To successfully cover the 48 km of beamline, ionisation chambers and optical fibre BLMs are under investigation. The former fulfils all CLIC requirements but would need more than 40000 monitors to protect the whole facility. For the latter, the capability of reconstructing the original loss position with a multi-bunch beam pulse and multiple loss locations still needs to be quantified. Two main sources of background for beam loss measurements are identified for CLIC. The two-beam accelerator scheme introduces so-called crosstalk, i.e. detection of losses originating in one beam line by the monitors protecting the other. Moreover, electrons emitted from the inner surface of RF cavities and boosted by the high RF gradients may produce signals in neighbouring BLMs, limiting their ability to detect real beam losses. This contribution presents the results of dedicated experiments performed in the CLIC Test Facility to quantify the position resolution of optical fibre BLMs in a multi-bunch, multi-loss scenario as well as the sensitivity limitations due to crosstalk and electron field emission.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR024

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MOPMR057

Measurements using Button BPM SUM Signal

electronics, storage-ring, operation, insertion

377

W.X. Cheng, K. Ha, J. Mead, O. Singh, G.M. Wang
BNL, Upton, Long Island, New York, USA

Modern digital BPM detectors measure not only the beam positions, four buttons SUM signal can be very helpful for machine developments and operations. At NSLS-II, BPM SUM signal has been used from commissioning stage, to investigate localized beam losses. During top-off operation, precise beam lifetime measurement within relative short period of time becomes important. With many BPMs along the ring, BPM SUM can be a much more accurate tool to measure the beam current and lifetime. BPM SUM signal shall be proportional to beam current, and it may depends on button sizes and BPM chamber geometry, cable attenuations, electronics attenuations, beam position, bunch lengths, fill pattern etc. Experience of BPM SUM signals measurements will be presented.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR057

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MOPMY027

Preliminary Design of High-efficiency Klystron for Pohang Accelerator Laboratory (PAL)

cavity, klystron, simulation, operation

557

S.J. Park, J.Y. Choi, Y.D. Joo, K.R. Kim, W. Namkung, C.D. Park
PAL, Pohang, Kyungbuk, Republic of Korea
M.-H. Cho, J.H. Hwang, T. Seong
POSTECH, Pohang, Kyungbuk, Republic of Korea

Funding: Supported by the Ministry of Science, ICT and Future Planning of Korea.
Klystrons for particle accelerators are typically designed to have narrow bandwidths with center frequencies ranging from several hundreds (e.g., 350) MHz to X-band (11.424 GHz). Output powers are from several tens of kW to ~1 MW for CW klystrons and ~100 MW for pulsed ones. The narrow-bandwidth requirement has enabled them to provide high gain (typically 40 - 50 dB) which greatly simplifies the RF drive system. Recently, especially for large-scale accelerator facilities, the klystron efficiency has become one of the most demanding issues. This is because electricity cost occupies a great portion of their operating budgets and the klystron efficiency is one of the important factors determining the electricity consumption of the whole accelerator system. In this regard, we have designed a high-efficiency klystron for use in the PLS-II and PAL XFEL at PAL. The basic scheme is to re-design the cavity system to include multi-cell output cavity. In this article, we report on our preliminary design work to determine major cavity parameters including cell frequencies, inter-cell distances, and coupling to external circuits (coupling beta).

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TUOAA01

Operation of LANSCE Linear Accelerator with Double Pulse Rate and Low Beam Losses

linac, DTL, proton, operation

1004

Y.K. Batygin, J.S. Kolski, R.C. McCrady, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by US DOE under contract DE-AC52-06NA25396
In 2014 LANSCE accelerator facility return to 120 Hz pulse rate operation after long period of operation at 60 Hz pulse rate. Increased capabilities require careful tuning of all components of linear accelerator. Transformation to double pulse rate resulted in re-evaluation of tuning procedures in order to meet new challenges in beam operation. The paper summarizes experimental activity on sustaining of high productivity of accelerator facility while keeping beam losses along accelerator at the low level.

Slides TUOAA01 [14.886 MB]

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TUPMW014

Improved Aperture Measurements at the LHC and Results from their Application in 2015

alignment, injection, operation, insertion

1446

P.D. Hermes, R. Bruce, M. Fiascaris, H. Garcia, M. Giovannozzi, A. Mereghetti, D. Mirarchi, E. Quaranta, S. Redaelli, B. Salvachua, G. Valentino
CERN, Geneva, Switzerland
R. Kwee-Hinzmann
Royal Holloway, University of London, Surrey, United Kingdom
E. Quaranta
Politecnico/Milano, Milano, Italy

A good knowledge of the available aperture in the LHC is essential for a safe operation due to the risk of magnet quenches or even damage in case of uncontrolled beam losses. Experimental validations of the available aperture are therefore crucial and were in the past carried out by either a collimator scan combined with beam excitations or through the use of local orbit bumps. In this paper, we show a first comparison of these methods in the same machine configuration, as well as a new very fast method based on a beam-based collimator alignment and a new faster variant of the collimator scan method. The methods are applied to the LHC operational configuration for 2015 at injection and with squeezed beams and the measured apertures are presented.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW014

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TUPMW023

Macroparticle-Induced Losses During 6.5 TeV LHC Operation

operation, proton, electron, luminosity

1481

G. Papotti, M. Albert, B. Auchmann, E.B. Holzer, M.K. Kalliokoski, A. Lechner
CERN, Geneva, Switzerland

One of the major performance limitations for operating the LHC at high energy was feared to be the so called UFOs (Unidentified Falling Objects, presumably micrometer sized dust particles which lead to fast beam losses when they interact with the beam). Indeed much higher rates were observed in 2015 compared to Run 1, and about 20 fills were prematurely terminated by too high losses caused by such events. Additionally they triggered a few beam induced quenches at high energy, the first in the history of the LHC. In this paper we review the latest update on the analysis of these events, e.g. the conditioning observed during the year and possible correlations with beam and machine parameters. At the same time we also review the optimization of beam loss monitor thresholds in terms of machine protection and availability.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW023

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TUPOW038

Measurement and Control of Beam Losses Under High Average-current Operation of the Compact ERL at KEK

radiation, operation, recirculation, optics

1839

S. Sakanaka, K. Haga, Y. Honda, H. Matsumura, T. Miyajima, T. Nogami, T. Obina, H. Sagehashi, M. Shimada, M. Yamamoto
KEK, Ibaraki, Japan

The compact ERL (cERL)* is a superconducting accelerator aimed at demonstrating excellent ERL technologies for the future light source. The cERL comprises a 5 MeV injector, a main linac, and a recirculation loop. In the cERL, production and transportation of low-emittance and high average-current beams (tentative goals: 1 mm-mrad and 10 mA) is primarily important. At this moment (in December 2015), beam currents of up to 80 uA (CW) have successfully been transported through the recirculation loop at a beam energy of 20 MeV. Before such high-current operations, we carefully tuned up the machine so that beam losses became very small. The beam losses were watched using fast beam-loss detectors and radiation monitors while absolute losses were estimated from measured radiation levels on the roof of the shield. After careful beam-optics corrections and elimination of beam halos / tails at low-energy section, we achieved the beam losses of at most a few nA level at several locations along the loop, and those below 1 nA elsewhere in the loop. We will report these results together with the result of higher-current operation which is planned early in 2016.
* S. Sakanaka et al., IPAC'15, TUBC1; T. Obina et al., to be presented at IPAC'16.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW038

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WEPMW007

Validation of Off-momentum Cleaning Performance of the LHC Collimation System

proton, collimation, injection, alignment

2427

B. Salvachua, P. Baudrenghien, R. Bruce, H. Garcia, P.D. Hermes, S. Jackson, M. Jaussi, A. Mereghetti, D. Mirarchi, S. Redaelli, H. Timko, G. Valentino, A. Valloni
CERN, Geneva, Switzerland
R. Kwee-Hinzmann
Royal Holloway, University of London, Surrey, United Kingdom

The LHC collimation system is designed to provide effective cleaning against losses coming from off-momentum particles, either due to un-captured beam or to an unexpected RF frequency change. For this reason the LHC is equipped with a hierarchy of collimators in IR3: primary, secondary and absorber collimators. After every collimator alignment or change of machine configuration the off-momentum cleaning efficiency is validated with loss maps at low intensity. We describe here the improved technique used in 2015 to generate such loss maps without completely dumping the beam into the collimators. The achieved performance of the collimation system for momentum cleaning is reviewed.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW007

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WEPMW031

Towards Optimum Material Choices for the HL-LHC Collimator Upgrade

impedance, collimation, luminosity, simulation

2498

E. Quaranta, A. Bertarelli, N. Biancacci, R. Bruce, F. Carra, E. Métral, S. Redaelli, A. Rossi, B. Salvant
CERN, Geneva, Switzerland
F. Carra
Politecnico di Torino, Torino, Italy

The first years of operation at the LHC showed that collimator material-related concerns might limit the performance. In addition, the HL-LHC upgrade will bring the accelerator beyond the nominal performance through more intense and brighter proton beams. A new generation of collimators based on advanced materials is needed to match present and new requirements. After several years of R&D on collimator materials, studying the behaviour of novel composites with properties that address different limitations of the present collimation system, solutions have been found to fulfil various upgrade challenges. This paper describes the proposed staged approach to deploy new materials in the upgraded HL-LHC collimation system. Beam tests at the CERN HiRadMat facility were also performed to benchmark simulation methods and constitutive material models.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW031

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WEPMW033

Validation of Simulation Tools for Fast Beam Failure Studies in the LHC

simulation, optics, collimation, proton

2506

E. Quaranta, C. Bracco, R. Bruce, S. Redaelli
CERN, Geneva, Switzerland

The LHC collimation system protects passively the most sensitive machine equipment against beam losses. In particular, collimators are the last line of defense in case of single-turn failures that cannot be caught by the standard interlock system. The collimator settings are conceived to protect the machine even for very rare events, like beam abort failures with a full machine. Collimator settings are established in simulations through a dedicated tracking setup but also empirically validated by beam measurements at low intensities. A benchmark of simulations is essential for reliably estimating the response of the system for future machine configurations and beam parameters. In the paper, results are presented of tracking simulations for different optics deployed in the LHC Run II at 6.5 TeV and compared with data.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW033

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WEPOY047

LHC Collimation and Energy Deposition Studies Using Beam Delivery Simulation (BDSIM)

simulation, collimation, optics, proton

3101

L.J. Nevay, S.T. Boogert, S.M. Gibson, R. Kwee-Hinzmann
JAI, Egham, Surrey, United Kingdom
R. Bruce, H. Garcia, S. Redaelli
CERN, Geneva, Switzerland

Beam Delivery Simulation (BDSIM) is a program that uses a suite of high energy physics software including Geant4, CLHEP & ROOT, that seamlessly tracks particles through accelerators and detectors utilising the full range of particles and physics processes from Geant4. A comparison of the collimator cleaning efficiency and energy deposition throughout the full length of the Large Hadron Collider (LHC) with the established SixTrack simulations of the CERN collimation group is presented. The propagation of the full hadronic showers from collimators provides unparalleled detail in energy deposition maps and these are compared with the data from beam loss monitors that measure radiation outside the magnet body.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY047

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THPMR003

Failure Modes and Beam Losses Studies in ILC Bunch Compressors and Main Linac

quadrupole, linac, cavity, cryomodule

3388

A. Saini, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Proposed International linear collider (ILC) involves high average beam power. Dealing with high average beam power and smaller beam sizes result in stringent tolerances on beam losses and therefore, extensive studies are required to investigate every possible scenarios that lead to beam losses. In this paper we discuss beam losses due to failure of critical elements in beamline for ILC bunch compressors and main linac.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR003

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THPOY032

The Dual Use of Beam Loss Monitors at FAIR-SIS100: General Diagnostics and Quench Prevention of Superconducting Magnets

ion, quadrupole, extraction, simulation

4167

S. Damjanovic, P. Kowina, C. Omet, M. Sapinski, M. Schwickert, P.J. Spiller
GSI, Darmstadt, Germany

In view of the planned coverage of the FAIR-SIS100 synchrotron with beam loss monitors (BLMs), FLUKA studies were performed aiming at two goals: i) evaluation of the sensitivity of the LHC-IC type detectors to the potential beam losses at SIS100; ii) estimation of the BLM quench prevention threshold via the correlation between the energy deposition inside the superconducting coils and the BLM active volume. A full spectrum of ion species and energies to be accelerated with SIS100 were considered in the simulations, showing a great sensitivity to the beam losses. An interesting finding of this study was that, for the same beam loss location, the quench prevention thresholds were almost identical for all ion species/energies including protons.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY032

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THPOY044

Experimental Setup to Measure the Damage Limits of Superconducting Magnets due to Beam Impact at CERN's HiRadMat Facility

experiment, dipole, proton, target

4200

D. Kleiven
Kleiven, David, Geneva, Switzerland
B. Auchmann, V. Raginel, R. Schmidt, A.P. Verweij, D. Wollmann
CERN, Geneva, Switzerland

Funding: Research supported by the High Luminosity LHC project
The future upgrade of CERN's injector chain for the Large Hadron Collider (LHC) will lead to an increase of the beam brightness in the LHC. Beam absorbers are capturing missteered beams, but some limited beam impact on superconducting magnets can hardly be avoided. Therefore, it is planned to measure the damage limits of superconducting magnet components due to beam impact at CERN's HiRad- Mat facility using the 440 GeV proton beam from the Super Proton Synchrotron. Two experiments are proposed. One at ambient and one at cryogenic temperatures, where several pre-stressed stacks of LHC main dipole Nb-Ti cables and some single strands will be irradiated with varying beam intensities. The electrical integrity and the degradation of critical current will be measured after the removal from the HiRadMat facility. In the cold experiment some sample magnets will be added and the degradation of performance will be monitored online. In this contribution the experimental setup of the first experiment, including the sample container and cable stacks, is presented.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY044

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THPOY045

Commissioning of the Machine Protection Systems of the Large Hadron Collider Following its First Long Shutdown

operation, dipole, injection, hadron

4203

D. Wollmann, R. Schmidt, J.A. Uythoven, J. Wenninger, M. Zerlauth
CERN, Geneva, Switzerland

During the first long shutdown of the Large Hadron Collider (LHC) extending for more than 18 months, most Machine Protection Systems (MPS) have undergone significant changes, and upgrades. A full re-commissioning of the MPS was performed at the end of the shutdown and during the LHC beam commissioning in 2015. To verify the correct functioning of all protection-relevant systems with beam, a step-wise intensity ramp-up was performed, reaching at the end of 2015 a record stored beam energy of ~280 MJ per beam, nearly 80% of the value in the design report. This contribution summarizes the results of the MPS commissioning, the intensity ramp-up and the continuous follow-up during operation, focusing mainly on near misses and false triggers and their proposed mitigations. A strategy to minimize risks during machine development periods for future operation of the LHC, when the protection parameters are modified for several tests, is discussed. The machine protection strategy for the LHC run in 2016 is presented.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY045

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