Author: Salvachua, B.
Paper Title Page
MOODB202 Simulations and Measurements of Cleaning with 100 MJ Beams in the LHC 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 icon Slides MOODB202 [6.343 MB]  
 
MOPWO032 SPS Scraping and LHC Transverse Tails 957
 
  • L.N. Drøsdal, K. Cornelis, B. Goddard, V. Kain, M. Meddahi, Ö. 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.  
 
MOPWO038 Cleaning Inefficiency of the LHC Collimation System during the Energy Ramp: Simulations and Measurements 975
 
  • E. Quaranta, R. Bruce, L. Lari, D. Mirarchi, S. Redaelli, A. Rossi, B. Salvachua, G. Valentino
    CERN, Geneva, Switzerland
  • 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
  
  The clean­ing in­ef­fi­ciency of the LHC col­li­ma­tion sys­tem has al­ready been stud­ied in de­tail at in­jec­tion and top en­ergy (450 GeV and 4 TeV re­spec­tively). In this paper the re­sults are pre­sented for the clean­ing in­ef­fi­ciency at in­ter­me­di­ate en­er­gies, sim­u­lated using the Six­Track code. The first com­par­isons with mea­sured pro­voked losses are dis­cussed. This study helps in bench­mark­ing the en­ergy de­pen­dence of the sim­u­lated in­ef­fi­ciency and is thus im­por­tant for the ex­trap­o­la­tion to fu­ture op­er­a­tion at higher en­er­gies.  
 
MOPWO039 Experience with High-intensity Beam Scraping and Tail Populations at the Large Hadon Collider 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.  
 
MOPWO046 Simulations and Measurements of Beam Losses on LHC Collimators during Beam Abort Failures 996
 
  • L. Lari, C. Bracco, R. Bruce, B. Goddard, S. Redaelli, B. Salvachua, G. Valentino
    CERN, Geneva, Switzerland
  • A. Faus-Golfe, L. Lari
    IFIC, Valencia, Spain
  • G. Valentino
    University of Malta, Information and Communication Technology, Msida, Malta
  
  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.
One of the main pur­poses of track­ing sim­u­la­tions for col­li­ma­tion stud­ies is to pro­duce loss maps along the LHC ring, in order to iden­tify the level of local beam losses dur­ing nom­i­nal and ab­nor­mal op­er­a­tion sce­nar­ios. The Six­Track pro­gram is the stan­dard track­ing tool used at CERN to per­form these stud­ies. Re­cently, it was ex­panded in order to eval­u­ate the pro­ton load on dif­fer­ent col­li­ma­tors in case of fast beam fail­ures. Sim­u­la­tions are com­pared with beam mea­sure­ments at 4 TeV. Com­bined fail­ures are as­sumed which pro­vide worst-case sce­nar­ios of the load on tung­sten ter­tiary col­li­ma­tors. 		 
 
MOPWO048 Cleaning Performance of the LHC Collimation System up to 4 TeV 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 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.  
 
MOPWO050 Comparison of LHC Beam Loss Maps using the Transverse Damper Blow up and Tune Resonance Crossing Methods 1008
 
  • V. Moens, R. Bruce, S. Redaelli, B. Salvachua, G. Valentino
    CERN, Geneva, Switzerland
  • V. Moens
    EPFL, Lausanne, Switzerland
  • G. Valentino
    University of Malta, Information and Communication Technology, Msida, Malta
  
  The LHC col­li­ma­tor set­tings are qual­i­fied reg­u­larly via beam loss maps. In this pro­ce­dure, the beam is ar­ti­fi­cially ex­cited to cre­ate ab­nor­mal loss rates. The trans­verse damper blow up and tune res­o­nance cross­ing meth­ods are used to in­crease the be­ta­tron am­pli­tude of par­ti­cles and ver­ify the ef­fi­ciency of the col­li­ma­tion clean­ing and the col­li­ma­tor hi­er­ar­chy. This paper pre­sents a quan­ti­ta­tive com­par­i­son of the meth­ods, based on mea­sure­ments done at dif­fer­ent phases of the LHC ma­chine cycle. The analy­sis is done using Beam Loss Mon­i­tor (BLM) with in­te­gra­tion times of 1.3 s and 80 ms. The use of the faster BLM data to study the time evo­lu­tion of the losses in IR3 and IR7 dur­ing off-mo­men­tum loss maps is also pre­sented.  
 
MOPWO051 Estimate of Warm Magnets Lifetime in the Betatron and Momentum Cleaning Insertions of the LHC 1011
 
  • B. Salvachua, R. Bruce, M. Brugger, F. Cerutti, S. Redaelli
    CERN, Geneva, Switzerland
  
  The CERN LHC col­li­ma­tion sys­tem is de­signed to per­form mo­men­tum and be­ta­tron clean­ing in dif­fer­ent in­ser­tions, re­spec­tively IR3 and IR7. The in­ser­tions are not per­fectly de­cou­pled be­cause the dis­per­sion in IR7 is not null and the beta func­tion in IR3 is not zero. The de­tailed shar­ing of losses be­tween the two in­ser­tions de­pends on the rel­a­tive col­li­ma­tor set­tings as ob­served by the change be­tween 2011 and 2012 LHC op­er­a­tion. In this re­port, using the beam loss mea­sure­ments at the pri­mary col­li­ma­tors of IR3 and IR7, the total BLM losses in the two in­ser­tions are cal­cu­lated and com­pared to each other. These stud­ies are also used to quan­tify the total dose to warm mag­nets in those IRs with the aim to un­der­stand bet­ter their life­time and the im­pli­ca­tions of the ra­di­a­tion to elec­tron­ics. This will be of par­tic­u­lar im­por­tance in view of LHC op­er­at­ing at nom­i­nal per­for­mance after sev­eral years of op­er­a­tion.  
 
TUPFI037 Collimation Down to 2 Sigma in Special Physics Runs in the LHC 1427
 
  • H. Burkhardt, S. Jakobsen, S. Redaelli, B. Salvachua, G. Valentino
    CERN, Geneva, Switzerland
  
  We re­port on ob­ser­va­tions with col­li­ma­tion very close to the beam. Pri­mary col­li­ma­tors were moved in small steps down to 2 σ from the beam axis to allow for mea­sure­ments of very for­ward pro­ton scat­ter­ing in spe­cial high-beta runs in the LHC. We stud­ied the re­duc­tion in in­ten­sity as a func­tion of col­li­ma­tor po­si­tion which pro­vides in­for­ma­tion about the halo shape. After scrap­ing at 2 σ, col­li­ma­tors were re­tracted to 2.5 σ. This al­lowed for mea­sure­ments of very for­ward pro­ton-pro­ton scat­ter­ing with roman pot de­tec­tors at 3 σ from the beam axis at ac­cept­able back­ground lev­els for about an hour. Good back­ground con­di­tions were re­stored by an­other scrap­ing with pri­mary col­li­ma­tors at 2 σ. Beam life­times and halo re­pop­u­la­tion times were found to be suf­fi­ciently long to allow for sev­eral hours of data tak­ing be­tween scrap­ing in a sin­gle LHC fill.  
 
TUPFI041 Operating the LHC Off-momentum for p-Pb Collisions 1439
 
  • R. Versteegen, R. Bruce, J.M. Jowett, A. Langner, Y.I. Levinsen, E.H. Maclean, M.J. McAteer, T. Persson, S. Redaelli, B. Salvachua, P. Skowroński, M. Solfaroli Camillocci, R. Tomás, G. Valentino, J. Wenninger
    CERN, Geneva, Switzerland
  • E.H. Maclean
    JAI, Oxford, United Kingdom
  • M.J. McAteer
    The University of Texas at Austin, Austin, USA
  • T. Persson
    Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden
  • G. Valentino
    University of Malta, Information and Communication Technology, Msida, Malta
  • S.M. White
    BNL, Upton, Long Island, New York, USA
  
  The first high-lu­mi­nos­ity p-Pb run at the LHC took place in Jan­u­ary-Feb­ru­ary 2013 at an en­ergy of 4 Z TeV per beam. The RF fre­quency dif­fer­ence of pro­ton and Pb is about 60 Hz for equal mag­netic rigidi­ties, which means that beams move slightly to off-mo­men­tum, non-cen­tral, or­bits dur­ing physics when fre­quen­cies are locked to­gether. The re­sult­ing op­ti­cal per­tur­ba­tions ("beta-beat­ing") re­strict the avail­able aper­ture and re­quired a spe­cial cor­rec­tion. This was also the first op­er­a­tion of the LHC with low beta in all four ex­per­i­ments and re­quired a spe­cific col­li­ma­tion set up. Pre­dic­tions from of­fline cal­cu­la­tions of beta-beat­ing cor­rec­tion are com­pared with mea­sure­ments dur­ing the op­tics com­mis­sion­ing and col­li­ma­tor set up.  
 
TUPME032 Update on Beam Induced RF Heating in the LHC 1646
 
  • B. Salvant, O. Aberle, G. Arduini, R.W. Aßmann, V. Baglin, M.J. Barnes, W. Bartmann, P. Baudrenghien, O.E. Berrig, A. Bertarelli, C. Bracco, E. Bravin, G. Bregliozzi, R. Bruce, F. Carra, F. Caspers, G. Cattenoz, S.D. Claudet, H.A. Day, M. Deile, J.F. Esteban Müller, P. Fassnacht, M. Garlaschè, L. Gentini, B. Goddard, A. Grudiev, B. Henrist, S. Jakobsen, O.R. Jones, O. Kononenko, G. Lanza, L. Lari, T. Mastoridis, V. Mertens, N. Mounet, E. Métral, A.A. Nosych, J.L. Nougaret, S. Persichelli, A.M. Piguiet, S. Redaelli, F. Roncarolo, G. Rumolo, B. Salvachua, M. Sapinski, R. Schmidt, E.N. Shaposhnikova, L.J. Tavian, M.A. Timmins, J.A. Uythoven, A. Vidal, J. Wenninger, D. Wollmann, M. Zerlauth
    CERN, Geneva, Switzerland
  • H.A. Day
    UMAN, Manchester, United Kingdom
  • L. Lari
    IFIC, Valencia, Spain
  
  Since June 2011, the rapid in­crease of the lu­mi­nos­ity per­for­mance of the LHC has come at the ex­pense of in­creased tem­per­a­ture and pres­sure read­ings on spe­cific near-beam LHC equip­ment. In some cases, this beam in­duced heat­ing has caused de­lays whilie equip­ment cools down, beam dumps and even degra­da­tion of these de­vices. This con­tri­bu­tion gath­ers the ob­ser­va­tions of beam in­duced heat­ing at­trib­ut­able to beam cou­pling im­ped­ance, their cur­rent level of un­der­stand­ing and pos­si­ble ac­tions that are planned to be im­ple­mented dur­ing the long shut­down in 2013-2014.  
 
TUPWA047 Collimator Impedance Measurements in the LHC 1817
 
  • N. Mounet, R. Bruce, E. Métral, S. Redaelli, B. Salvachua, B. Salvant, G. Valentino
    CERN, Geneva, Switzerland
  
  The col­li­ma­tion sys­tem of the LHC is one of the largest im­ped­ance con­trib­u­tors of the ma­chine, in par­tic­u­lar for its imag­i­nary part. To eval­u­ate the col­li­ma­tor im­ped­ance and its evo­lu­tion with in­te­grated lu­mi­nos­ity, sev­eral mea­sure­ment cam­paigns were per­formed along the year 2012, in which col­li­ma­tor jaws were moved back-and-forth lead­ing to sig­nif­i­cant tune shifts for a nom­i­nal in­ten­sity bunch in the ma­chine. These ob­ser­va­tions are com­pared to the re­sults from HEAD­TAIL sim­u­la­tions with the im­ped­ance model in its cur­rent state of de­vel­op­ment.  
 
THPEA045 Beam Induced Quenches of LHC Magnets 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.  
 
THPFI063 Development and Beam Tests of an Automatic Algorithm for Alignment of LHC Collimators with Embedded BPMs 3439
 
  • G. Valentino
    University of Malta, Information and Communication Technology, Msida, Malta
  • R.W. Aßmann
    DESY, Hamburg, Germany
  • R. Bruce, M. Gasior, D. Mirarchi, A.A. Nosych, S. Redaelli, B. Salvachua, N.J. Sammut
    CERN, Geneva, Switzerland
  
  Col­li­ma­tors with em­bed­ded Beam Po­si­tion Mon­i­tor (BPM) but­tons will be in­stalled in the LHC dur­ing the up­com­ing long shut­down pe­riod. Dur­ing the sub­se­quent op­er­a­tion, the BPMs will allow the col­li­ma­tor jaws to be kept cen­tered around the beam tra­jec­tory. In this man­ner, the best pos­si­ble beam clean­ing ef­fi­ciency and ma­chine pro­tec­tion can be pro­vided at un­prece­dented higher beam en­er­gies and in­ten­si­ties. A col­li­ma­tor align­ment al­go­rithm is pro­posed to cen­ter the jaws au­to­mat­i­cally around the beam. The al­go­rithm is based on suc­ces­sive ap­prox­i­ma­tion, as the BPM mea­sure­ments are af­fected by non-lin­ear­i­ties, which vary with the dis­tance be­tween op­po­site but­tons, as well as the dif­fer­ence be­tween the beam and the jaw cen­ters. The suc­cess­ful test re­sults, as well as some con­sid­er­a­tions for even­tual op­er­a­tion in the LHC are also pre­sented.