IPAC2013 - List of Keywords (beam-losses)

Paper	Title	Other Keywords	Page
MOODB202	Simulations and Measurements of Cleaning with 100 MJ Beams in the LHC	simulation, proton, collimation, betatron	52
	R. Bruce, R.W. Aßmann, V. Boccone, C. Bracco, M. Cauchi, F. Cerutti, D. Deboy, A. Ferrari, L. Lari, A. Marsili, A. Mereghetti, E. Quaranta, S. Redaelli, G. Robert-Demolaize, A. Rossi, B. Salvachua, E. Skordis, G. Valentino, V. Vlachoudis, Th. Weiler, D. Wollmann CERN, Geneva, Switzerland L. Lari IFIC, Valencia, Spain E. Quaranta Politecnico/Milano, Milano, Italy G. Valentino University of Malta, Information and Communication Technology, Msida, Malta
	The CERN Large Hadron Collider is routinely storing proton beam intensities of more than 100 MJ, which puts extraordinary demands on the control of beam losses to avoid quenches of the superconducting magnets. Therefore, a detailed understanding of the LHC beam cleaning is required. We present tracking and shower simulations of the LHC's multi-stage collimation system and compare with measured beam losses, which allow us to conclude on the predictive power of the simulations.
	Slides MOODB202 [6.343 MB]

MOPEA005	A Linear Beam Raster System for the European Spallation Source?	target, linac, quadrupole, optics	70
	H.D. Thomsen, A.I.S. Holm, S.P. Møller ISA, Aarhus, Denmark
	The European Spallation Source (ESS) will, when built, be the most intense neutron source in the world. The neutrons are generated by a high power (5 MW) proton beam impacting a rotating W spallation target. To reduce the replacement frequency of components subjected to the full beam current, i.e. the proton beam window and the target, means to introduce low peak current densities, i.e. flat transverse beam profiles, are necessary. The relatively long beam pulse duration of 2.86 ms (at 14 Hz) leaves ample time to facilitate a Lissajous-like, linear raster system that illuminates a footprint area by sweeping an only moderately enlarged LINAC beamlet. Although slightly more technically challenging, this method has many advantages over the previously envisaged beam expander system based on non-linear DC magnets. The design, specifications, performance, and benefits of the beam raster system will be described and discussed.

MOPWA035	Beam Loss Studies for the CERN PS Booster using FLUKA	injection, booster, multipole, extraction	744
	S. Damjanovic, B. Dehning, B. Mikulec, M. Sapinski CERN, Geneva, Switzerland
	In view of future upgrade plans, the beam loss monitor (BLM) coverage of the PS Booster (PSB) rings was reviewed. The response of two types of monitors, LHC-IC and LHC-LIC, has been studied with FLUKA at LINAC4 injection and PSB extraction energies. The goal of this study was to find out whether the current beam loss monitor coverage of two monitors at a certain location per PSB section was adapted to potential beam losses associated with a future Linac4 injection. The outcome of this study was a proposal to double the number of beam loss monitors in the PSB section by using a combination of horizontally oriented LHC-IC and LHC-LIC type monitors.

MOPWA040	Bipolar 10A and 50A Magnet Power Supplies for SwissFEL	controls, power-supply, monitoring	756
	R. Künzi, M. Emmenegger PSI, Villigen PSI, Switzerland
	15 years ago the Power Electronics Group at PSI, Switzerland developed power supplies (PS) for the magnets of the Swiss Light Source (SLS). These PS are based on switched mode converters with fully digital control. During the 12 years of operation of the SLS they have shown a very good reliability but also revealed some potential for improvement: After several years of operation the many fans installed started to fail more frequently and the same was observed for “off-the-shelf” AC/DC converters for the DC link. For the new SwissFEL, which shall be in service by 2016, approx. 610 PS rated at 10A and 40 PS rated at 50A will be necessary. As for any accelerator application high stability and reliability of the magnet PS are essential for high beam quality and availability. The development of the SwissFEL PS aims to raise the already good reliability by omitting as many fans as possible and adding redundancy for the AC/DC converters. Presently, a prototype rack with 21 10A PS is available and the mass production has started. The presented paper describes the PS concept and test results of the prototype regarding stability and efficiency are given.

MOPWO010	Machine Protection Studies for a Crab Cavity in the LHC	simulation, luminosity, cavity, collimation	906
	B. Yee-Rendon, R. Lopez-Fernandez CINVESTAV, Mexico City, Mexico T. Baer, J. Barranco, R. Calaga, A. Marsili, R. Tomás, F. Zimmermann CERN, Geneva, Switzerland
	Funding: US-LARP and CONACYT Crab cavities (CCs) apply a transverse kick that rotate the bunches so as to have a head-on collision at the interaction point (IP). Such cavities were successfully used to improve the luminosity of KEKB. They are also a key ingredient of the HL-LHC project to increase the luminosity of the LHC. As CCs can rapidly change the particle trajectories, machine protection studies are required to assess the beam losses due to fast CC failures. In this paper, we discuss the effect of rapid voltage or phase changes in a CC for the HL-LHC layout using measured beam distributions from the present LHC.

MOPWO032	SPS Scraping and LHC Transverse Tails	injection, emittance, luminosity, controls	957
	L.N. Drøsdal, K. Cornelis, B. Goddard, V. Kain, M. Meddahi, O. Mete, B. Salvachua, G. Valentino, E. Veyrunes CERN, Geneva, Switzerland
	All high-intensity LHC beams have to be scraped before extraction from the SPS to remove the non-Gaussian transverse tails of the particle distributions. The tail particles would otherwise cause unacceptably high losses during injection or other phases of the LHC cycle. Studies have been carried out to quantify the scraping using injection losses and emittance measurements from wire scanners as diagnostics. Beams scraped in the SPS were scraped again in the LHC with collimators to investigate possible tail repopulation. The results of these studies will be presented in this paper.

MOPWO039	Experience with High-intensity Beam Scraping and Tail Populations at the Large Hadon Collider	emittance, injection, hadron, diagnostics	978
	S. Redaelli, R. Bruce, F. Burkart, D. Mirarchi, B. Salvachua, G. Valentino, D. Wollmann CERN, Geneva, Switzerland R.W. Aßmann DESY, Hamburg, Germany G. Valentino University of Malta, Information and Communication Technology, Msida, Malta
	The population of beam tails at the LHC is source of concern because even small fractions of the total beam intensity could represent a potential danger is case of slow or fast losses, e.g. caused by orbit transients or by collimator movements. Different studies have been performed using the technique of collimator scans to probe the beam tail population, for different beam energies and beam intensities. The experience accumulated during the operation at 3.5 TeV and 4 TeV is reviewed and extrapolations to higher energies are considered.

MOPWO048	Cleaning Performance of the LHC Collimation System up to 4 TeV	alignment, collimation, insertion, betatron	1002
	B. Salvachua, R.W. Aßmann, R. Bruce, M. Cauchi, D. Deboy, L. Lari, A. Marsili, D. Mirarchi, E. Quaranta, S. Redaelli, A. Rossi, G. Valentino CERN, Geneva, Switzerland M. Cauchi UoM, Msida, Malta L. Lari IFIC, Valencia, Spain D. Mirarchi The Imperial College of Science, Technology and Medicine, London, United Kingdom G. Valentino University of Malta, Information and Communication Technology, Msida, Malta
	Funding: Research supported by EU FP7 HiLumi LHC (Grant agreement 284404) In this paper we review the performance of the LHC collimation system during 2012 and compare it with previous years. During 2012, the so-called tight settings were deployed for a better cleaning and improved beta-star reach. As a result, a record cleaning efficiency below a few 0.0001 was achieved in the cold regions where the highest beam losses occur. The cleaning in other cold locations is typically a factor of 10 better. No quenches were observed during regular operation with up to 140 MJ stored beam energy. The system stability during the year, monitored regularly to ensure the system functionality for all machine configurations, and the performance of the alignment tools are also reviewed.

MOPWO049	Lifetime Analysis at High Intensity Colliders Applied to the LHC	proton, collider, collimation, luminosity	1005
	B. Salvachua, R.W. Aßmann, R. Bruce, F. Burkart, S. Redaelli, G. Valentino, D. Wollmann CERN, Geneva, Switzerland G. Valentino University of Malta, Information and Communication Technology, Msida, Malta
	The beam lifetime is one of the main parameters to define the performance of a collider. In a super-conducting machine like the LHC, the lifetime determines the intensity reach for a given collimation cleaning. The beam lifetime can be calculated from the direct measurement of beam current. However, due to the noise in the beam current signal only an average lifetime over several seconds can be calculated. We propose here an alternative method, which uses the signal of the beam loss monitors in the vicinity of the primary collimators to get the instantaneous beam lifetime at the collimators. In this paper we compare the lifetime from the two methods and investigate the minimum lifetime over the LHC cycle for all the physics fills in 2011 and 2012. These data provide a reference for estimates of performance reach from collimator cleaning.

TUPFI011	Study and Operational Implementation of a Tilted Crossing Angle in LHCb	dipole, luminosity, controls, monitoring	1349
	R. Alemany-Fernandez, F. Follin, B.J. Holzer, D. Jacquet, R. Versteegen, J. Wenninger CERN, Geneva, Switzerland
	The current crossing angle scheme at LHCb interaction point (horizontal crossing angle and vertical beam separation) prohibits the use of the LHCb dipole positive polarity for 25 ns bunch spacing operation since the beam separation at the first parasitic encounter is very small inducing unwanted beam encounters. To overcome this limitation a different crossing angle scheme was proposed in 2007 by W. Herr and Y. Papaphilippou. The new schema implies a vertical external crossing angle that together with the horizontal internal crossing angle, from the LHCb dipole and its three compensator magnets, defines a new tilted crossing and separation plane providing enough beam separation at the parasitic encounters. This paper summarizes the feasibility study of the new crossing scheme, the implementation in routine operation and analyzes the beam stability during the building up of the tilted crossing plane.

TUPFI028	Beam Losses Through the LHC Operational Cycle in 2012	proton, luminosity, emittance, injection	1400
	G. Papotti, A.A. Gorzawski, M. Hostettler, R. Schmidt CERN, Geneva, Switzerland
	We review the losses through the nominal LHC cycle for physics operation in 2012. The loss patterns are studied and categorized according to timescale, distribution, time in the cycle, which bunches are affected, whether coherent or incoherent. Possible causes and correlations are identified, e.g. to machine parameters or instability signatures. A comparison with losses in the previous years of operation is also shown.

TUPFI045	Electron-cloud Maps for LHC Scrubbing Optimization	electron, injection, simulation, dipole	1451
	C.O. Domínguez, F. Zimmermann CERN, Geneva, Switzerland
	Electron-cloud maps as alternative to detailed build-up simulations have already been applied in the past for a few accelerators, e.g. RHIC and the LHC at 7 TeV. We here report a first application of maps to optimize the "beam scrubbing" of the LHC arcs at injection energy: Maps are used to efficiently determine the optimum bunch filling pattern which maximizes the electron flux on the chamber wall, while respecting constraints on the central cloud density to ensure beam stability. In addition, new features have been explored, e.g. by introducing thresholds which divide regions where either linear maps or cubic maps best describe the build-up and the decay of an electron cloud. In the near future we plan to extend the map formalism to individual slices in a dipole file in order to represent the vertical "stripes".

TUPFI078	Measurement of the Total Cross Section of Uranium-uranium Collisions at a Center-of-mass Energy of 192.8 GeV per Nucleon-pair	ion, luminosity, scattering, emittance	1529
	W. Fischer, A.J. Baltz, M. Blaskiewicz, K.A. Drees, D.M. Gassner, Y. Luo, M.G. Minty, P. Thieberger, M. Wilinski BNL, Upton, Long Island, New York, USA I.A. Pshenichnov RAS/INR, Moscow, Russia
	Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886 with the U.S. Department of Energy. Heavy ion cross sections totaling several hundred barns have been calculated previously for the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). These total cross sections are more than an order of magnitude larger than the geometric ion-ion cross sections, primarily due to Bound-Free Pair Production (BFPP) and Electro-Magnetic Dissociation (EMD). Apart from a general interest in verifying the calculations experimentally, an accurate prediction of the losses created in the heavy ion collisions is of practical interest for the LHC, where some collision products are lost in cryogenically cooled magnets and have the potential to quench these magnets. In the 2012 RHIC run uranium ions collided with each other at a center-of-mass energy of 192.8 GeV per nucleon-pair with nearly all beam losses due to collisions. This allows for the measurement of the total cross section and a comparison with calculations.

TUPME054	Experimental Study of the Effect of Beam Loading on RF Breakdown Rate in CLIC High-gradient Accelerating Structures	linac, beam-loading, optics, luminosity	1691
	F. Tecker, R. Corsini, M. Dayyani Kelisani, S. Döbert, A. Grudiev, O. Kononenko, S. Lebet, J.L. Navarro Quirante, G. Riddone, I. Syratchev, W. Wuensch CERN, Geneva, Switzerland A. Solodko JINR, Dubna, Moscow Region, Russia
	RF breakdown is a key issue for the multi-TeV high-luminosity e⁺e⁻ Compact Linear Collider (CLIC). Breakdowns in the high-gradient accelerator structures can deflect the beam and decrease the desired luminosity. The limitations of the accelerating structures due to breakdowns have been studied so far without a beam present in the structure. The presence of the beam modifies the distribution of the electrical and magnetic field distributions, which determine the breakdown rate. Therefore an experiment has been designed for high power testing a CLIC prototype accelerating structure with a beam present in the CLIC Test Facility (CTF3). A special beam line allows extracting a beam with nominal CLIC beam current and duration from the CTF3 linac. The paper describes the beam optics design for this experimental beam line and the commissioning of the experiment with beam.

TUPWA034	On the Choice of Linac Parameters for Minimal Beam Losses	space-charge, linac, emittance, resonance	1787
	M. Eshraqi ESS, Lund, Sweden J.-M. Lagniel GANIL, Caen, France
	In high intensity linear accelerators, the tune spreads induced by the space-charge forces in the radial and longitudinal planes are key parameters for halo formation and beam losses. For matched beams they are the parameters governing the number of resonances (including coupling resonances) which affect the beam and determine the respective sizes of the stable and halo areas in phase space. The number and strength of the resonances excited in mismatched beams leading to even higher amplitude halos are also directly linked to the tune spreads. In this paper, the equations making the link between the basic linac parameters (rf frequency, zero-current phase advances, beam intensity and emittances) and the tune spreads are given. A first analysis of the way these linac parameters can be chosen to minimize the tune spreads is presented. The parameters of ESS linac are used for this study.

WEPEA046	Experimental Observations from the LHC Dynamic Aperture Machine Development Study in 2012	dynamic-aperture, emittance, injection, octupole	2606
	M. Giovannozzi, S. Cettour Cave, R. De Maria, M. Ludwig, A. Macpherson, S. Redaelli, F. Roncarolo, M. Solfaroli Camillocci, W. Venturini Delsolaro CERN, Geneva, Switzerland
	In view of improving the understanding of the behaviour of the dynamic aperture and to benchmark the numerical simulations performed so far, two experimental sessions have been scheduled at the LHC. The observations of the first sessions have been reported elsewhere[1], while in this paper the latest observations in terms of beam currents, blm losses and beam sizes will be described. The octupolar spool pieces have been used to artificially reduce the dynamic aperture and then induced slow beam losses. Alternating signs have been used in order to probe different configurations. Finally, scans over the strength of the decapolar spool pieces have been performed too. [1] M. Giovannozzi et al., “First Experimental Observations from the LHC Dynamic Aperture Experiment”, in proceedings of IPAC12, p. 1362

WEPEA050	Analysis of Possible Functional Forms of the Scaling Law for Dynamic Aperture as a Function of Time	dynamic-aperture, luminosity, simulation, lattice	2618
	M. Giovannozzi, R. De Maria, F. Lang CERN, Geneva, Switzerland
	Funding: The HiLumi LHC Design Study is included in the HL-LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404. In recent studies, the evolution of the dynamic aperture with time has been fitted with a simple scaling law based on a limited number of free parameters. In this paper, different approaches to improve the numerical stability of the fit are presented, together with a new functional form. The results are discussed in details and applied to a set of numerical simulations for the LHC.

WEPEA057	Numerical Simulations to Evaluate the Performance of CERN PS Dummy Septum to Reduce Irradiation for the Multi-Turn Extraction	septum, extraction, shielding, kicker	2636
	C. Hernalsteens, S. Damjanovic, S.S. Gilardoni, M. Giovannozzi CERN, Geneva, Switzerland
	The losses created by the proposed Multi-Turn Extraction (MTE) at the CERN PS induces high activation of the magnetic extraction septum due to the de-bunched longitudinal beam structure requested to transfer the beam to the SPS. A mitigation measure is under study aiming at localizing losses in a well-shielded area by shadowing the magnetic extraction septum thanks to septum-like passive device. Such a solution is based on a so-called dummy septum, a blade which absorbs particles during the rise time of the extraction kickers for MTE beams. The efficiency of the scheme is presented in this paper. The quantitative estimate is based on detailed simulations that analyse the beam-matter interaction and provide a determination of the shadowing effect of the dummy septum.

WEPME044	Generation of Controlled Losses in Milisecond Timescale with Transverse Damper in LHC	simulation, proton, emittance, injection	3025
	M. Sapinski, T. Baer, V. Chetvertkova, B. Dehning, W. Höfle, A. Priebe, R. Schmidt, D. Valuch CERN, Geneva, Switzerland
	A controlled way of generating of beam losses is required in order to investigate the quench limits of the superconducting magnets in the LHC. This is especially difficult to achieve for losses with millisecond duration. A series of experiments using the transverse damper system has proven that such a fast loss can be obtained even in the case of rigid 4 TeV beams. This paper describes the optimisation of beam parameters and transverse damper waveform required to mimic fast loss scenarios and reports on extensive tracking simulations undertaken to fully understand the time and spatial structure of these losses. The application of this method to the final quench tests is also presented.

THXB101	High Power Operation and Beam Instrumentations in J-PARC Synchrotrons	extraction, quadrupole, proton, synchrotron	3085
	T. Toyama J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	Beam monitors developed and utilized at MR and RCS of J-PARC will be presented with emphasis on special characteristics for high intensity proton accelerator. Achieved beam characteristics and approach to improve beam intensity will be described in connection with the beam monitors. Usage of a transverse RF field to improve a duty factor of the slow extracted beam will be presented.
	Slides THXB101 [16.387 MB]

THPEA040	Design of a Magnetic Bump Tail Scraping System for the CERN SPS	injection, extraction, radiation, closed-orbit	3228
	Ö. Mete, J. Bauche, F. Cerutti, S. Cettour Cave, K. Cornelis, L.N. Drøsdal, F. Galleazzi, B. Goddard, L.K. Jensen, V. Kain, Y. Le Borgne, G. Le Godec, M. Meddahi, E. Veyrunes, H. Vincke, J. Wenninger CERN, Geneva, Switzerland A. Mereghetti UMAN, Manchester, United Kingdom
	The LHC injectors are being upgraded to meet the demanding beam specification required for High Luminosity LHC (HL-LHC) operation. In order to reduce the beam losses which can trigger the sensitive LHC beam loss interlocks during the SPS-to-LHC beam injection process, it is important that the beam tails are properly scraped away in the SPS. The current SPS tail cleaning system relies on a moveable scraper blade, with the positioning of the scraper adjusted over time according to the orbit variations of the SPS. A new robust beam tail cleaning system has been designed which will use a fixed scraper block towards which the beam will be moved by a local magnetic orbit bump. The design proposal is presented, together with the related beam dynamics studies and results from machine studies with beam.

THPEA044	Radiation Tolerance of Cryogenic Beam Loss Monitor Detectors	proton, radiation, cryogenics, monitoring	3240
	C. Kurfuerst, C. Arregui Rementeria, M.R. Bartosik, B. Dehning, T. Eisel, M. Sapinski CERN, Geneva, Switzerland V. Eremin, E. Verbitskaya IOFFE, St. Petersburg, Russia C. Fabjan HEPHY, Wien, Austria E. Griesmayer CIVIDEC Instrumentation, Wien, Austria
	At the triplet magnets, close to the interaction regions of the LHC, the current Beam Loss Monitoring system is sensitive to the particle showers resulting from the collision of the two beams. For the future, with beams of higher energy and intensity resulting in higher luminosity, distinguishing between these interaction products and possible quench-provoking beam losses from the primary proton beams will be challenging. Investigations are therefore underway to optimise the system by locating the beam loss detectors as close as possible to the superconducting coils of the triplet magnets. This means putting detectors inside the cold mass in superfluid helium at 1.9 K. Previous tests have shown that solid state diamond and silicon detectors as well as liquid helium ionisation chambers are promising candidates. This paper will address the final open question of their radiation resistance for 20 years of nominal LHC operation, by reporting on the results from high irradiation beam tests carried out at CERN in a liquid helium environment.

THPEA045	Beam Induced Quenches of LHC Magnets	injection, quadrupole, simulation, kicker	3243
	M. Sapinski, T. Baer, M. Bednarek, G. Bellodi, C. Bracco, R. Bruce, B. Dehning, W. Höfle, A. Lechner, E. Nebot Del Busto, A. Priebe, S. Redaelli, B. Salvachua, R. Schmidt, D. Valuch, A.P. Verweij, J. Wenninger, D. Wollmann, M. Zerlauth CERN, Geneva, Switzerland
	In the years 2009-2013 LHC was operating with the beam energy of 3.5 and 4 TeV instead of the nominal 7 TeV, with the corresponding currents in the superconducting magnets also half nominal. To date only a small number of beam-induced quenches have occurred, with most being due to specially designed quench tests. During normal collider operation with stored beam there has not been a single beam induced quench. This excellent result is mainly explained by the fact that the cleaning of the beam halo worked very well and, in case of beam losses, the beam was dumped before any significant energy was deposited in the magnets. However, conditions are expected to become much tougher after the long LHC shutdown, when the magnets will be working at near nominal currents in the presence of high energy and intensity beams. This paper summarizes the experience to date with beam-induced quenches. It describes the techniques used to generate controlled quench conditions which were used to study the limitations. Results are discussed along with their implication for LHC operation after the first Long Shutdown.

THPEA047	Diamond Particle Detector Properties during High Fluence Material Damage Tests and their Future Applications for Machine Protection in the LHC	simulation, target, proton, radiation	3249
	F. Burkart, J. Blanco, J. Borburgh, B. Dehning, M. Di Castro, E. Griesmayer, A. Lechner, J. Lendaro, F. Loprete, R. Losito, S. Montesano, R. Schmidt, D. Wollmann, M. Zerlauth CERN, Geneva, Switzerland E. Griesmayer CIVIDEC Instrumentation, Wien, Austria
	Experience with LHC machine protection (MP) during the last three years of operation shows that the MP systems sufficiently protect the LHC against damage in case of failures leading to beam losses with a time constant exceeding 1ms. An unexpected fast beam loss mechanism, called UFOs, was observed, which could potentially quench superconducting magnets. For such fast losses, but also for better understanding of slower losses, an improved understanding of the loss distribution within a bunch train is required. Diamond particle detectors with bunch-by-bunch resolution and high dynamic range have been developed and successfully tested in the LHC and in experiments to quantify the damage limits of LHC components. This paper will focus on experience gained in use of diamond detectors. The properties of these detectors were measured during high-fluence material damage tests in CERN's HiRadMat facility. The results will be discussed and compared to the cross-calibration with FLUKA simulations. Future applications of these detectors in the LHC to understand beam losses and to improve the protection against fast particle losses will be discussed.

THPFI022	The M-C Application in Designing Tailored Cryopump Used in Cyciae-100 Cyclotron	vacuum, cyclotron, radiation, ion	3342
	S.P. Zhang, Z.G. Li, G.F. Pan, J.S. Xing, F. Yang, T.J. Zhang CIAE, Beijing, People's Republic of China
	A compact high intensity cyclotron CYCIAE-100 was selected as the driver for the Beijing Radioactive Ion Facility (BRIF). A pressure of 5×10-8 mbar is required to achieve acceptable beam losses in the CYCIAE-100 cyclotron. As the existing ports on the cyclotron valley are insufficient to provide enough pumping speed using commercially available pumps, two tailored cryopanels with a pumping speed of 60000 l/s for each are designed. Based on the Monte-Carlo method, a mathematical model of molecular movement and collision between the panels and their shield was developed. The ratio of molecular reflected to the baffle to molecular passing through the baffle is the sticking probability on the panels. When taking the transmission probability of the chevron baffle, capture coefficient of cryopanel can be calculated. It could provide a reference to design the cryopanel shape and its condensation area.

THPFI045	Reliability Approach for Machine Protection Design in Particle Accelerators	linac, controls, proton, booster	3388
	A. Apollonio, J.-B. Lallement, B. Mikulec, B. Puccio, J.L. Sanchez Alvarez, R. Schmidt, S. Wagner CERN, Geneva, Switzerland
	Particle accelerators require Machine Protection Systems (MPS) to prevent beam induced damage of equipment in case of failures. This becomes increasingly important for proton colliders with large energy stored in the beam such as LHC, for high power accelerators with a beam power of up to 10 MW, such as the European Spallation Source (ESS), and for linear colliders with high beam power and very small beam size. The reliability of Machine Protection Systems is crucial for safe machine operation; all possible sources of risk need to be taken into account in the early design stage. This paper presents a systematic approach to classify failures and to assess the associated risk, and discusses the impact of such considerations on the design of Machine Protection Systems. The application of this approach will be illustrated using the new design of the MPS for LINAC 4, a linear accelerator under construction at CERN.

THPFI054	Preliminary Comparison of the Response of LHC Tertiary Collimators to Proton and Ion Beam Impacts	ion, proton, heavy-ion, collimation	3412
	M. Cauchi, R.W. Aßmann, A. Bertarelli, F. Carra, F. Cerutti, L. Lari CERN, Geneva, Switzerland M. Cauchi, P. Mollicone UoM, Msida, Malta L. Lari IFIC, Valencia, Spain N.J. Sammut University of Malta, Information and Communication Technology, Msida, Malta
	The CERN Large Hadron Collider is designed to bring into collision protons as well as heavy ions. Accidents involving impacts on collimators can happen for both species. The interaction of lead ions with matter differs to that of protons, thus making this scenario a new interesting case to study as it can result in different damage aspects on the collimator. This paper will present a preliminary comparison of the response of collimators to proton and ion beam impacts.

THPWA048	New Generation X-band Linacs for Medical and Industrial Appplications	linac, electron, RF-structure, radiation	3741
	A.V. Mishin, S. Proskin RMX, North Andover, USA
	The proposed designs of the new X-band linear accelerators for industrial and medical applications are based on a well-known side-coupled RF structure. The immediate applications envisioned for the new linear accelerators are security screening and intraoperative radiotherapy (IORT). The new design has promising features and presents cost reduction potential for electron beam and X-ray systems used in medical, industrial, and security screening applications.

Paper

Title

Other Keywords

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MOODB202

Simulations and Measurements of Cleaning with 100 MJ Beams in the LHC

simulation, proton, collimation, betatron

52

R. Bruce, R.W. Aßmann, V. Boccone, C. Bracco, M. Cauchi, F. Cerutti, D. Deboy, A. Ferrari, L. Lari, A. Marsili, A. Mereghetti, E. Quaranta, S. Redaelli, G. Robert-Demolaize, A. Rossi, B. Salvachua, E. Skordis, G. Valentino, V. Vlachoudis, Th. Weiler, D. Wollmann
CERN, Geneva, Switzerland
L. Lari
IFIC, Valencia, Spain
E. Quaranta
Politecnico/Milano, Milano, Italy
G. Valentino
University of Malta, Information and Communication Technology, Msida, Malta

The CERN Large Hadron Collider is routinely storing proton beam intensities of more than 100 MJ, which puts extraordinary demands on the control of beam losses to avoid quenches of the superconducting magnets. Therefore, a detailed understanding of the LHC beam cleaning is required. We present tracking and shower simulations of the LHC's multi-stage collimation system and compare with measured beam losses, which allow us to conclude on the predictive power of the simulations.

Slides MOODB202 [6.343 MB]

MOPEA005

A Linear Beam Raster System for the European Spallation Source?

target, linac, quadrupole, optics

70

H.D. Thomsen, A.I.S. Holm, S.P. Møller
ISA, Aarhus, Denmark

The European Spallation Source (ESS) will, when built, be the most intense neutron source in the world. The neutrons are generated by a high power (5 MW) proton beam impacting a rotating W spallation target. To reduce the replacement frequency of components subjected to the full beam current, i.e. the proton beam window and the target, means to introduce low peak current densities, i.e. flat transverse beam profiles, are necessary. The relatively long beam pulse duration of 2.86 ms (at 14 Hz) leaves ample time to facilitate a Lissajous-like, linear raster system that illuminates a footprint area by sweeping an only moderately enlarged LINAC beamlet. Although slightly more technically challenging, this method has many advantages over the previously envisaged beam expander system based on non-linear DC magnets. The design, specifications, performance, and benefits of the beam raster system will be described and discussed.

MOPWA035

Beam Loss Studies for the CERN PS Booster using FLUKA

injection, booster, multipole, extraction

744

S. Damjanovic, B. Dehning, B. Mikulec, M. Sapinski
CERN, Geneva, Switzerland

In view of future upgrade plans, the beam loss monitor (BLM) coverage of the PS Booster (PSB) rings was reviewed. The response of two types of monitors, LHC-IC and LHC-LIC, has been studied with FLUKA at LINAC4 injection and PSB extraction energies. The goal of this study was to find out whether the current beam loss monitor coverage of two monitors at a certain location per PSB section was adapted to potential beam losses associated with a future Linac4 injection. The outcome of this study was a proposal to double the number of beam loss monitors in the PSB section by using a combination of horizontally oriented LHC-IC and LHC-LIC type monitors.

MOPWA040

Bipolar 10A and 50A Magnet Power Supplies for SwissFEL

controls, power-supply, monitoring

756

R. Künzi, M. Emmenegger
PSI, Villigen PSI, Switzerland

15 years ago the Power Electronics Group at PSI, Switzerland developed power supplies (PS) for the magnets of the Swiss Light Source (SLS). These PS are based on switched mode converters with fully digital control. During the 12 years of operation of the SLS they have shown a very good reliability but also revealed some potential for improvement: After several years of operation the many fans installed started to fail more frequently and the same was observed for “off-the-shelf” AC/DC converters for the DC link. For the new SwissFEL, which shall be in service by 2016, approx. 610 PS rated at 10A and 40 PS rated at 50A will be necessary. As for any accelerator application high stability and reliability of the magnet PS are essential for high beam quality and availability. The development of the SwissFEL PS aims to raise the already good reliability by omitting as many fans as possible and adding redundancy for the AC/DC converters. Presently, a prototype rack with 21 10A PS is available and the mass production has started. The presented paper describes the PS concept and test results of the prototype regarding stability and efficiency are given.

MOPWO010

Machine Protection Studies for a Crab Cavity in the LHC

simulation, luminosity, cavity, collimation

906

B. Yee-Rendon, R. Lopez-Fernandez
CINVESTAV, Mexico City, Mexico
T. Baer, J. Barranco, R. Calaga, A. Marsili, R. Tomás, F. Zimmermann
CERN, Geneva, Switzerland

Funding: US-LARP and CONACYT
Crab cavities (CCs) apply a transverse kick that rotate the bunches so as to have a head-on collision at the interaction point (IP). Such cavities were successfully used to improve the luminosity of KEKB. They are also a key ingredient of the HL-LHC project to increase the luminosity of the LHC. As CCs can rapidly change the particle trajectories, machine protection studies are required to assess the beam losses due to fast CC failures. In this paper, we discuss the effect of rapid voltage or phase changes in a CC for the HL-LHC layout using measured beam distributions from the present LHC.

MOPWO032

SPS Scraping and LHC Transverse Tails

injection, emittance, luminosity, controls

957

L.N. Drøsdal, K. Cornelis, B. Goddard, V. Kain, M. Meddahi, O. Mete, B. Salvachua, G. Valentino, E. Veyrunes
CERN, Geneva, Switzerland

All high-intensity LHC beams have to be scraped before extraction from the SPS to remove the non-Gaussian transverse tails of the particle distributions. The tail particles would otherwise cause unacceptably high losses during injection or other phases of the LHC cycle. Studies have been carried out to quantify the scraping using injection losses and emittance measurements from wire scanners as diagnostics. Beams scraped in the SPS were scraped again in the LHC with collimators to investigate possible tail repopulation. The results of these studies will be presented in this paper.

MOPWO039

Experience with High-intensity Beam Scraping and Tail Populations at the Large Hadon Collider

emittance, injection, hadron, diagnostics

978

S. Redaelli, R. Bruce, F. Burkart, D. Mirarchi, B. Salvachua, G. Valentino, D. Wollmann
CERN, Geneva, Switzerland
R.W. Aßmann
DESY, Hamburg, Germany
G. Valentino
University of Malta, Information and Communication Technology, Msida, Malta

The population of beam tails at the LHC is source of concern because even small fractions of the total beam intensity could represent a potential danger is case of slow or fast losses, e.g. caused by orbit transients or by collimator movements. Different studies have been performed using the technique of collimator scans to probe the beam tail population, for different beam energies and beam intensities. The experience accumulated during the operation at 3.5 TeV and 4 TeV is reviewed and extrapolations to higher energies are considered.

MOPWO048

Cleaning Performance of the LHC Collimation System up to 4 TeV

alignment, collimation, insertion, betatron

1002

B. Salvachua, R.W. Aßmann, R. Bruce, M. Cauchi, D. Deboy, L. Lari, A. Marsili, D. Mirarchi, E. Quaranta, S. Redaelli, A. Rossi, G. Valentino
CERN, Geneva, Switzerland
M. Cauchi
UoM, Msida, Malta
L. Lari
IFIC, Valencia, Spain
D. Mirarchi
The Imperial College of Science, Technology and Medicine, London, United Kingdom
G. Valentino
University of Malta, Information and Communication Technology, Msida, Malta

Funding: Research supported by EU FP7 HiLumi LHC (Grant agreement 284404)
In this paper we review the performance of the LHC collimation system during 2012 and compare it with previous years. During 2012, the so-called tight settings were deployed for a better cleaning and improved beta-star reach. As a result, a record cleaning efficiency below a few 0.0001 was achieved in the cold regions where the highest beam losses occur. The cleaning in other cold locations is typically a factor of 10 better. No quenches were observed during regular operation with up to 140 MJ stored beam energy. The system stability during the year, monitored regularly to ensure the system functionality for all machine configurations, and the performance of the alignment tools are also reviewed.

MOPWO049

Lifetime Analysis at High Intensity Colliders Applied to the LHC

proton, collider, collimation, luminosity

1005

B. Salvachua, R.W. Aßmann, R. Bruce, F. Burkart, S. Redaelli, G. Valentino, D. Wollmann
CERN, Geneva, Switzerland
G. Valentino
University of Malta, Information and Communication Technology, Msida, Malta

The beam lifetime is one of the main parameters to define the performance of a collider. In a super-conducting machine like the LHC, the lifetime determines the intensity reach for a given collimation cleaning. The beam lifetime can be calculated from the direct measurement of beam current. However, due to the noise in the beam current signal only an average lifetime over several seconds can be calculated. We propose here an alternative method, which uses the signal of the beam loss monitors in the vicinity of the primary collimators to get the instantaneous beam lifetime at the collimators. In this paper we compare the lifetime from the two methods and investigate the minimum lifetime over the LHC cycle for all the physics fills in 2011 and 2012. These data provide a reference for estimates of performance reach from collimator cleaning.

TUPFI011

Study and Operational Implementation of a Tilted Crossing Angle in LHCb

dipole, luminosity, controls, monitoring

1349

R. Alemany-Fernandez, F. Follin, B.J. Holzer, D. Jacquet, R. Versteegen, J. Wenninger
CERN, Geneva, Switzerland

The current crossing angle scheme at LHCb interaction point (horizontal crossing angle and vertical beam separation) prohibits the use of the LHCb dipole positive polarity for 25 ns bunch spacing operation since the beam separation at the first parasitic encounter is very small inducing unwanted beam encounters. To overcome this limitation a different crossing angle scheme was proposed in 2007 by W. Herr and Y. Papaphilippou. The new schema implies a vertical external crossing angle that together with the horizontal internal crossing angle, from the LHCb dipole and its three compensator magnets, defines a new tilted crossing and separation plane providing enough beam separation at the parasitic encounters. This paper summarizes the feasibility study of the new crossing scheme, the implementation in routine operation and analyzes the beam stability during the building up of the tilted crossing plane.

TUPFI028

Beam Losses Through the LHC Operational Cycle in 2012

proton, luminosity, emittance, injection

1400

G. Papotti, A.A. Gorzawski, M. Hostettler, R. Schmidt
CERN, Geneva, Switzerland

We review the losses through the nominal LHC cycle for physics operation in 2012. The loss patterns are studied and categorized according to timescale, distribution, time in the cycle, which bunches are affected, whether coherent or incoherent. Possible causes and correlations are identified, e.g. to machine parameters or instability signatures. A comparison with losses in the previous years of operation is also shown.

TUPFI045

Electron-cloud Maps for LHC Scrubbing Optimization

electron, injection, simulation, dipole

1451

C.O. Domínguez, F. Zimmermann
CERN, Geneva, Switzerland

Electron-cloud maps as alternative to detailed build-up simulations have already been applied in the past for a few accelerators, e.g. RHIC and the LHC at 7 TeV. We here report a first application of maps to optimize the "beam scrubbing" of the LHC arcs at injection energy: Maps are used to efficiently determine the optimum bunch filling pattern which maximizes the electron flux on the chamber wall, while respecting constraints on the central cloud density to ensure beam stability. In addition, new features have been explored, e.g. by introducing thresholds which divide regions where either linear maps or cubic maps best describe the build-up and the decay of an electron cloud. In the near future we plan to extend the map formalism to individual slices in a dipole file in order to represent the vertical "stripes".

TUPFI078

Measurement of the Total Cross Section of Uranium-uranium Collisions at a Center-of-mass Energy of 192.8 GeV per Nucleon-pair

ion, luminosity, scattering, emittance

1529

W. Fischer, A.J. Baltz, M. Blaskiewicz, K.A. Drees, D.M. Gassner, Y. Luo, M.G. Minty, P. Thieberger, M. Wilinski
BNL, Upton, Long Island, New York, USA
I.A. Pshenichnov
RAS/INR, Moscow, Russia

Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886 with the U.S. Department of Energy.
Heavy ion cross sections totaling several hundred barns have been calculated previously for the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). These total cross sections are more than an order of magnitude larger than the geometric ion-ion cross sections, primarily due to Bound-Free Pair Production (BFPP) and Electro-Magnetic Dissociation (EMD). Apart from a general interest in verifying the calculations experimentally, an accurate prediction of the losses created in the heavy ion collisions is of practical interest for the LHC, where some collision products are lost in cryogenically cooled magnets and have the potential to quench these magnets. In the 2012 RHIC run uranium ions collided with each other at a center-of-mass energy of 192.8 GeV per nucleon-pair with nearly all beam losses due to collisions. This allows for the measurement of the total cross section and a comparison with calculations.

TUPME054

Experimental Study of the Effect of Beam Loading on RF Breakdown Rate in CLIC High-gradient Accelerating Structures

linac, beam-loading, optics, luminosity

1691

F. Tecker, R. Corsini, M. Dayyani Kelisani, S. Döbert, A. Grudiev, O. Kononenko, S. Lebet, J.L. Navarro Quirante, G. Riddone, I. Syratchev, W. Wuensch
CERN, Geneva, Switzerland
A. Solodko
JINR, Dubna, Moscow Region, Russia

RF breakdown is a key issue for the multi-TeV high-luminosity e⁺e⁻ Compact Linear Collider (CLIC). Breakdowns in the high-gradient accelerator structures can deflect the beam and decrease the desired luminosity. The limitations of the accelerating structures due to breakdowns have been studied so far without a beam present in the structure. The presence of the beam modifies the distribution of the electrical and magnetic field distributions, which determine the breakdown rate. Therefore an experiment has been designed for high power testing a CLIC prototype accelerating structure with a beam present in the CLIC Test Facility (CTF3). A special beam line allows extracting a beam with nominal CLIC beam current and duration from the CTF3 linac. The paper describes the beam optics design for this experimental beam line and the commissioning of the experiment with beam.

TUPWA034

On the Choice of Linac Parameters for Minimal Beam Losses

space-charge, linac, emittance, resonance

1787

M. Eshraqi
ESS, Lund, Sweden
J.-M. Lagniel
GANIL, Caen, France

In high intensity linear accelerators, the tune spreads induced by the space-charge forces in the radial and longitudinal planes are key parameters for halo formation and beam losses. For matched beams they are the parameters governing the number of resonances (including coupling resonances) which affect the beam and determine the respective sizes of the stable and halo areas in phase space. The number and strength of the resonances excited in mismatched beams leading to even higher amplitude halos are also directly linked to the tune spreads. In this paper, the equations making the link between the basic linac parameters (rf frequency, zero-current phase advances, beam intensity and emittances) and the tune spreads are given. A first analysis of the way these linac parameters can be chosen to minimize the tune spreads is presented. The parameters of ESS linac are used for this study.

WEPEA046

Experimental Observations from the LHC Dynamic Aperture Machine Development Study in 2012

dynamic-aperture, emittance, injection, octupole

2606

M. Giovannozzi, S. Cettour Cave, R. De Maria, M. Ludwig, A. Macpherson, S. Redaelli, F. Roncarolo, M. Solfaroli Camillocci, W. Venturini Delsolaro
CERN, Geneva, Switzerland

In view of improving the understanding of the behaviour of the dynamic aperture and to benchmark the numerical simulations performed so far, two experimental sessions have been scheduled at the LHC. The observations of the first sessions have been reported elsewhere[1], while in this paper the latest observations in terms of beam currents, blm losses and beam sizes will be described. The octupolar spool pieces have been used to artificially reduce the dynamic aperture and then induced slow beam losses. Alternating signs have been used in order to probe different configurations. Finally, scans over the strength of the decapolar spool pieces have been performed too.
[1] M. Giovannozzi et al., “First Experimental Observations from the LHC Dynamic Aperture Experiment”, in proceedings of IPAC12, p. 1362

WEPEA050

Analysis of Possible Functional Forms of the Scaling Law for Dynamic Aperture as a Function of Time

dynamic-aperture, luminosity, simulation, lattice

2618

M. Giovannozzi, R. De Maria, F. Lang
CERN, Geneva, Switzerland

Funding: The HiLumi LHC Design Study is included in the HL-LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.
In recent studies, the evolution of the dynamic aperture with time has been fitted with a simple scaling law based on a limited number of free parameters. In this paper, different approaches to improve the numerical stability of the fit are presented, together with a new functional form. The results are discussed in details and applied to a set of numerical simulations for the LHC.

WEPEA057

Numerical Simulations to Evaluate the Performance of CERN PS Dummy Septum to Reduce Irradiation for the Multi-Turn Extraction

septum, extraction, shielding, kicker

2636

C. Hernalsteens, S. Damjanovic, S.S. Gilardoni, M. Giovannozzi
CERN, Geneva, Switzerland

The losses created by the proposed Multi-Turn Extraction (MTE) at the CERN PS induces high activation of the magnetic extraction septum due to the de-bunched longitudinal beam structure requested to transfer the beam to the SPS. A mitigation measure is under study aiming at localizing losses in a well-shielded area by shadowing the magnetic extraction septum thanks to septum-like passive device. Such a solution is based on a so-called dummy septum, a blade which absorbs particles during the rise time of the extraction kickers for MTE beams. The efficiency of the scheme is presented in this paper. The quantitative estimate is based on detailed simulations that analyse the beam-matter interaction and provide a determination of the shadowing effect of the dummy septum.

WEPME044

Generation of Controlled Losses in Milisecond Timescale with Transverse Damper in LHC

simulation, proton, emittance, injection

3025

M. Sapinski, T. Baer, V. Chetvertkova, B. Dehning, W. Höfle, A. Priebe, R. Schmidt, D. Valuch
CERN, Geneva, Switzerland

A controlled way of generating of beam losses is required in order to investigate the quench limits of the superconducting magnets in the LHC. This is especially difficult to achieve for losses with millisecond duration. A series of experiments using the transverse damper system has proven that such a fast loss can be obtained even in the case of rigid 4 TeV beams. This paper describes the optimisation of beam parameters and transverse damper waveform required to mimic fast loss scenarios and reports on extensive tracking simulations undertaken to fully understand the time and spatial structure of these losses. The application of this method to the final quench tests is also presented.

THXB101

High Power Operation and Beam Instrumentations in J-PARC Synchrotrons

extraction, quadrupole, proton, synchrotron

3085

T. Toyama
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

Beam monitors developed and utilized at MR and RCS of J-PARC will be presented with emphasis on special characteristics for high intensity proton accelerator. Achieved beam characteristics and approach to improve beam intensity will be described in connection with the beam monitors. Usage of a transverse RF field to improve a duty factor of the slow extracted beam will be presented.

Slides THXB101 [16.387 MB]

THPEA040

Design of a Magnetic Bump Tail Scraping System for the CERN SPS

injection, extraction, radiation, closed-orbit

3228

Ö. Mete, J. Bauche, F. Cerutti, S. Cettour Cave, K. Cornelis, L.N. Drøsdal, F. Galleazzi, B. Goddard, L.K. Jensen, V. Kain, Y. Le Borgne, G. Le Godec, M. Meddahi, E. Veyrunes, H. Vincke, J. Wenninger
CERN, Geneva, Switzerland
A. Mereghetti
UMAN, Manchester, United Kingdom

The LHC injectors are being upgraded to meet the demanding beam specification required for High Luminosity LHC (HL-LHC) operation. In order to reduce the beam losses which can trigger the sensitive LHC beam loss interlocks during the SPS-to-LHC beam injection process, it is important that the beam tails are properly scraped away in the SPS. The current SPS tail cleaning system relies on a moveable scraper blade, with the positioning of the scraper adjusted over time according to the orbit variations of the SPS. A new robust beam tail cleaning system has been designed which will use a fixed scraper block towards which the beam will be moved by a local magnetic orbit bump. The design proposal is presented, together with the related beam dynamics studies and results from machine studies with beam.

THPEA044

Radiation Tolerance of Cryogenic Beam Loss Monitor Detectors

proton, radiation, cryogenics, monitoring

3240

C. Kurfuerst, C. Arregui Rementeria, M.R. Bartosik, B. Dehning, T. Eisel, M. Sapinski
CERN, Geneva, Switzerland
V. Eremin, E. Verbitskaya
IOFFE, St. Petersburg, Russia
C. Fabjan
HEPHY, Wien, Austria
E. Griesmayer
CIVIDEC Instrumentation, Wien, Austria

At the triplet magnets, close to the interaction regions of the LHC, the current Beam Loss Monitoring system is sensitive to the particle showers resulting from the collision of the two beams. For the future, with beams of higher energy and intensity resulting in higher luminosity, distinguishing between these interaction products and possible quench-provoking beam losses from the primary proton beams will be challenging. Investigations are therefore underway to optimise the system by locating the beam loss detectors as close as possible to the superconducting coils of the triplet magnets. This means putting detectors inside the cold mass in superfluid helium at 1.9 K. Previous tests have shown that solid state diamond and silicon detectors as well as liquid helium ionisation chambers are promising candidates. This paper will address the final open question of their radiation resistance for 20 years of nominal LHC operation, by reporting on the results from high irradiation beam tests carried out at CERN in a liquid helium environment.

THPEA045

Beam Induced Quenches of LHC Magnets

injection, quadrupole, simulation, kicker

3243

M. Sapinski, T. Baer, M. Bednarek, G. Bellodi, C. Bracco, R. Bruce, B. Dehning, W. Höfle, A. Lechner, E. Nebot Del Busto, A. Priebe, S. Redaelli, B. Salvachua, R. Schmidt, D. Valuch, A.P. Verweij, J. Wenninger, D. Wollmann, M. Zerlauth
CERN, Geneva, Switzerland

In the years 2009-2013 LHC was operating with the beam energy of 3.5 and 4 TeV instead of the nominal 7 TeV, with the corresponding currents in the superconducting magnets also half nominal. To date only a small number of beam-induced quenches have occurred, with most being due to specially designed quench tests. During normal collider operation with stored beam there has not been a single beam induced quench. This excellent result is mainly explained by the fact that the cleaning of the beam halo worked very well and, in case of beam losses, the beam was dumped before any significant energy was deposited in the magnets. However, conditions are expected to become much tougher after the long LHC shutdown, when the magnets will be working at near nominal currents in the presence of high energy and intensity beams. This paper summarizes the experience to date with beam-induced quenches. It describes the techniques used to generate controlled quench conditions which were used to study the limitations. Results are discussed along with their implication for LHC operation after the first Long Shutdown.

THPEA047

Diamond Particle Detector Properties during High Fluence Material Damage Tests and their Future Applications for Machine Protection in the LHC

simulation, target, proton, radiation

3249

F. Burkart, J. Blanco, J. Borburgh, B. Dehning, M. Di Castro, E. Griesmayer, A. Lechner, J. Lendaro, F. Loprete, R. Losito, S. Montesano, R. Schmidt, D. Wollmann, M. Zerlauth
CERN, Geneva, Switzerland
E. Griesmayer
CIVIDEC Instrumentation, Wien, Austria

Experience with LHC machine protection (MP) during the last three years of operation shows that the MP systems sufficiently protect the LHC against damage in case of failures leading to beam losses with a time constant exceeding 1ms. An unexpected fast beam loss mechanism, called UFOs, was observed, which could potentially quench superconducting magnets. For such fast losses, but also for better understanding of slower losses, an improved understanding of the loss distribution within a bunch train is required. Diamond particle detectors with bunch-by-bunch resolution and high dynamic range have been developed and successfully tested in the LHC and in experiments to quantify the damage limits of LHC components. This paper will focus on experience gained in use of diamond detectors. The properties of these detectors were measured during high-fluence material damage tests in CERN's HiRadMat facility. The results will be discussed and compared to the cross-calibration with FLUKA simulations. Future applications of these detectors in the LHC to understand beam losses and to improve the protection against fast particle losses will be discussed.

THPFI022

The M-C Application in Designing Tailored Cryopump Used in Cyciae-100 Cyclotron

vacuum, cyclotron, radiation, ion

3342

S.P. Zhang, Z.G. Li, G.F. Pan, J.S. Xing, F. Yang, T.J. Zhang
CIAE, Beijing, People's Republic of China

A compact high intensity cyclotron CYCIAE-100 was selected as the driver for the Beijing Radioactive Ion Facility (BRIF). A pressure of 5×10-8 mbar is required to achieve acceptable beam losses in the CYCIAE-100 cyclotron. As the existing ports on the cyclotron valley are insufficient to provide enough pumping speed using commercially available pumps, two tailored cryopanels with a pumping speed of 60000 l/s for each are designed. Based on the Monte-Carlo method, a mathematical model of molecular movement and collision between the panels and their shield was developed. The ratio of molecular reflected to the baffle to molecular passing through the baffle is the sticking probability on the panels. When taking the transmission probability of the chevron baffle, capture coefficient of cryopanel can be calculated. It could provide a reference to design the cryopanel shape and its condensation area.

THPFI045

Reliability Approach for Machine Protection Design in Particle Accelerators

linac, controls, proton, booster

3388

A. Apollonio, J.-B. Lallement, B. Mikulec, B. Puccio, J.L. Sanchez Alvarez, R. Schmidt, S. Wagner
CERN, Geneva, Switzerland

Particle accelerators require Machine Protection Systems (MPS) to prevent beam induced damage of equipment in case of failures. This becomes increasingly important for proton colliders with large energy stored in the beam such as LHC, for high power accelerators with a beam power of up to 10 MW, such as the European Spallation Source (ESS), and for linear colliders with high beam power and very small beam size. The reliability of Machine Protection Systems is crucial for safe machine operation; all possible sources of risk need to be taken into account in the early design stage. This paper presents a systematic approach to classify failures and to assess the associated risk, and discusses the impact of such considerations on the design of Machine Protection Systems. The application of this approach will be illustrated using the new design of the MPS for LINAC 4, a linear accelerator under construction at CERN.

THPFI054

Preliminary Comparison of the Response of LHC Tertiary Collimators to Proton and Ion Beam Impacts

ion, proton, heavy-ion, collimation

3412

M. Cauchi, R.W. Aßmann, A. Bertarelli, F. Carra, F. Cerutti, L. Lari
CERN, Geneva, Switzerland
M. Cauchi, P. Mollicone
UoM, Msida, Malta
L. Lari
IFIC, Valencia, Spain
N.J. Sammut
University of Malta, Information and Communication Technology, Msida, Malta

The CERN Large Hadron Collider is designed to bring into collision protons as well as heavy ions. Accidents involving impacts on collimators can happen for both species. The interaction of lead ions with matter differs to that of protons, thus making this scenario a new interesting case to study as it can result in different damage aspects on the collimator. This paper will present a preliminary comparison of the response of collimators to proton and ion beam impacts.

THPWA048

New Generation X-band Linacs for Medical and Industrial Appplications

linac, electron, RF-structure, radiation

3741

A.V. Mishin, S. Proskin
RMX, North Andover, USA

The proposed designs of the new X-band linear accelerators for industrial and medical applications are based on a well-known side-coupled RF structure. The immediate applications envisioned for the new linear accelerators are security screening and intraoperative radiotherapy (IORT). The new design has promising features and presents cost reduction potential for electron beam and X-ray systems used in medical, industrial, and security screening applications.