Author: Métral, E.
Paper Title Page
MOPWA030 Upgrade of the LHC Injection Kicker Magnets 729
 
  • M.J. Barnes, P. Adraktas, V. Baglin, G. Bregliozzi, S. Calatroni, F. Caspers, H.A. Day, L. Ducimetière, M. Garlaschè, V. Gomes Namora, J.M. Jimenez, N. Magnin, V. Mertens, E. Métral, B. Salvant, M. Taborelli, J.A. Uythoven, W.J.M. Weterings
    CERN, Geneva, Switzerland
  
  The two LHC in­jec­tion kicker sys­tems, com­pris­ing 4 mag­nets per ring, pro­duce a kick of 1.3 T.m with a rise-time of less than 900 ns and a flat­top rip­ple of less than ±0.5%. A beam screen is placed in the aper­ture of each mag­net, to pro­vide a path for the image cur­rent of the high in­ten­sity LHC beam and screen the fer­rite yoke against wake fields. The screen con­sists of a ce­ramic tube with con­duc­tors in the inner wall. The ini­tially im­ple­mented beam screen en­sured a low rate of elec­tri­cal break­downs while pro­vid­ing an ad­e­quate beam cou­pling im­ped­ance. Op­er­a­tion with in­creas­ingly higher in­ten­sity beams, sta­ble for many hours at a time, now re­sults in sub­stan­tial heat­ing of the fer­rite yoke, some­times re­quir­ing cool down over sev­eral hours be­fore the LHC can be re­filled. Dur­ing the long shut­down in 2013/2014 all 8 kicker mag­nets will be up­graded with an im­proved beam screen and an in­creased emis­siv­ity of the vac­uum tank. In ad­di­tion equip­ment ad­ja­cent to the in­jec­tion kick­ers and var­i­ous vac­uum com­po­nents will also be mod­i­fied to help re­duce the vac­uum pres­sure in the kick­ers dur­ing high-in­ten­sity op­er­a­tion. This paper dis­cusses the up­grades as well as their prepa­ra­tion and plan­ning.  
 
TUPFI031 Effect of Collision Pattern in the LHC on the Beam Stability: Requirements from Experiments and Operational Considerations 1409
 
  • W. Herr, G. Arduini, R. Giachino, E. Métral, G. Papotti, T. Pieloni
    CERN, Geneva, Switzerland
  • X. Buffat, N. Mounet
    EPFL, Lausanne, Switzerland
  • S.M. White
    BNL, Upton, Long Island, New York, USA
  
  Co­her­ent in­sta­bil­i­ties of bunches in the LHC bunch train can be ob­served when the tune spread from beam-beam in­ter­ac­tions be­comes in­suf­fi­cient to en­sure Lan­dau damp­ing. In par­tic­u­lar these ef­fects are seen on bunches with a re­duced num­ber of beam-beam in­ter­ac­tions due to their col­li­sion pat­tern. Fur­ther­more, such a re­duc­tion of the nec­es­sary sta­bil­ity can occur dur­ing the processes when the beams are pre­pared for col­li­sions or dur­ing the op­ti­miza­tion pro­ce­dure. We dis­cuss the ob­ser­va­tions and pos­si­ble coun­ter­mea­sures, in par­tic­u­lar al­ter­na­tives to the ex­ist­ing beam ma­nip­u­la­tion processes where such a sit­u­a­tion can occur.  
 
TUPFI032 Observation of Instabilities in the LHC due to Missing Head-on Beam-beam Interactions 1412
 
  • W. Herr, G. Arduini, R. Giachino, E. Métral, G. Papotti, T. Pieloni
    CERN, Geneva, Switzerland
  • X. Buffat, N. Mounet
    EPFL, Lausanne, Switzerland
  
  We re­port the ob­ser­va­tion of co­her­ent in­sta­bil­i­ties on in­di­vid­ual bunches out of the LHC bunch train. These in­sta­bil­i­ties oc­cured spon­ta­neously after sev­eral hours of sta­ble beam while in other cases they were re­lated to the ap­pli­ca­tion of a small trans­verse beam sep­a­ra­tion dur­ing a lu­mi­nos­ity op­ti­miza­tion. Only few bunches were af­fected, de­pend­ing on there col­li­sion scheme and fol­low­ing var­i­ous tests we in­ter­prete these in­sta­bil­i­ties as a sud­den loss of Lan­dau damp­ing when the tune spread from the beam-beam in­ter­ac­tion be­came in­suf­fi­cient.  
 
TUPFI034 Observations of Two-beam Instabilities during the 2012 LHC Physics Run 1418
 
  • T. Pieloni
    EPFL, Lausanne, Switzerland
  • G. Arduini, X. Buffat, R. Giachino, W. Herr, M. Lamont, N. Mounet, E. Métral, G. Papotti, B. Salvant, J. Wenninger
    CERN, Geneva, Switzerland
  • S.M. White
    BNL, Upton, Long Island, New York, USA
  
  Dur­ing the 2012 run co­her­ent beam in­sta­bil­i­ties have been ob­served in the LHC at 4 TeV, dur­ing the be­ta­tron squeeze and in col­li­sion for spe­cial fill­ing pat­terns. Sev­eral stud­ies to char­ac­ter­ize these in­sta­bil­i­ties have been car­ried out dur­ing op­er­a­tion and in spe­cial ded­i­cated ex­per­i­ments. In this paper we sum­ma­rize the ob­ser­va­tions col­lected for dif­fer­ent ma­chine pa­ra­me­ters and the pre­sent un­der­stand­ing of the ori­gin of these in­sta­bil­i­ties.  
 
TUPFI035 Head-on and Long range Beam-beam Interactions in the LHC: Effective Tune Spread and Beam Stability due to Landau Damping 1421
 
  • X. Buffat
    EPFL, Lausanne, Switzerland
  • W. Herr, N. Mounet, E. Métral, T. Pieloni
    CERN, Geneva, Switzerland
  
  We dis­cuss the Lan­dau damp­ing of co­her­ent in­sta­bil­i­ties in the pres­ence of be­ta­tron tune spread. This tune spread can orig­i­nate from ded­i­cated non-lin­ear mag­nets such as oc­tupoles, or through the beam-beam in­ter­ac­tion. In the lat­ter case we have to dis­tin­guish the con­tri­bu­tion from head-on and par­a­sitic beam-beam in­ter­ac­tions and the col­li­sion pat­tern of dif­fer­ent bunches plays an im­por­tant role. The in­ter­play of these sources of tune spread and the re­sult­ing sta­bil­ity is dis­cussed for the case of the LHC.  
 
TUPFI063 Electromagnetic Coupling between High Intensity LHC Beams and the Synchrotron Radiation Monitor Light Extraction System 1493
 
  • F. Roncarolo, W. Andreazza, A. Bertarelli, E. Bravin, F. Caspers, M. Garlaschè, A. Goldblatt, J-J. Gras, O.R. Jones, T. Lefèvre, E. Métral, A.A. Nosych, B. Salvant, G. Trad, R. Veness, C. Vollinger, M. Wendt
    CERN, Geneva, Switzerland
  
  The CERN LHC is equipped with two Syn­chro­tron Ra­di­a­tion Mon­i­tor sys­tems used to char­ac­terise trans­verse and lon­gi­tu­di­nal beam dis­tri­b­u­tions. Since the end of the 2011 LHC run the light ex­trac­tion sys­tem, based on a re­tractable mir­ror, has suf­fered de­for­ma­tion and me­chan­i­cal fail­ure that is cor­re­lated to the in­crease in beam in­ten­sity. Tem­per­a­ture probes have as­so­ci­ated these ob­ser­va­tions to a strong heat­ing of the mir­ror sup­port with a de­pen­dence on the lon­gi­tu­di­nal bunch length and shape, in­di­cat­ing the ori­gin as elec­tro­mag­netic cou­pling be­tween the beam and the struc­ture. This paper com­bines all this in­for­ma­tion with the aim of char­ac­ter­is­ing and im­prov­ing the sys­tem in view of its up­grade dur­ing the cur­rent LHC shut­down. Beam-based ob­ser­va­tions are pre­sented along with elec­tro­mag­netic and ther­mo­me­chan­i­cal sim­u­la­tions and com­ple­mented by lab­o­ra­tory mea­sure­ments, in­clud­ing the study of the RF prop­er­ties of dif­fer­ent mir­ror bulk and coat­ing ma­te­ri­als.  
 
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.  
 
TUPME033 Evaluation of the Beam Coupling Impedance of New beam Screen Designs for the LHC Injection Kicker Magnets 1649
 
  • H.A. Day
    UMAN, Manchester, United Kingdom
  • M.J. Barnes, F. Caspers, E. Métral, B. Salvant
    CERN, Geneva, Switzerland
  • R.M. Jones
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  
  The LHC in­jec­tion kicker mag­nets (MKIs) have ex­pe­ri­enced a sig­nif­i­cant de­gree of beam in­duced heat­ing since the be­gin­ning of the 2011 due to the in­creas­ing in­ten­sity stored in the LHC, for long pe­ri­ods of time, and the rel­a­tively large broad­band im­ped­ance of the in­stalled kicker mag­nets. In this paper we show the sources of im­ped­ance in the MKIs, es­pe­cially the ef­fect that the beam screen di­men­sions have on the im­ped­ance. We show how these alter the power loss, and pre­sent an im­proved beam screen de­sign that im­proves shield­ing on the mag­net, whilst fur­ther im­prov­ing elec­tri­cal break­down.  
 
TUPWA042 Lessons Learned and Mitigation Measures for the CERN LHC Equipment with RF Fingers 1802
 
  • E. Métral, O. Aberle, R.W. Aßmann, V. Baglin, M.J. Barnes, O.E. Berrig, A. Bertarelli, G. Bregliozzi, S. Calatroni, F. Carra, F. Caspers, H.A. Day, M. Ferro-Luzzi, M.A. Gallilee, C. Garion, M. Garlaschè, A. Grudiev, J.M. Jimenez, O.R. Jones, O. Kononenko, R. Losito, J.L. Nougaret, V. Parma, S. Redaelli, B. Salvant, P.M. Strubin, R. Veness, C. Vollinger, W.J.M. Weterings
    CERN, Geneva, Switzerland
  
  Beam-in­duced RF heat­ing has been ob­served in sev­eral LHC com­po­nents when the bunch/beam in­ten­sity was in­creased and/or the bunch length re­duced. In par­tic­u­lar eight bel­lows, out of the ten dou­ble-bel­lows mod­ules pre­sent in the ma­chine in 2011, were found with the spring, which should keep the RF fin­gers in good elec­tri­cal con­tact with the cen­tral in­sert, bro­ken. Fol­low­ing these ob­ser­va­tions, the de­signs of all the com­po­nents of the LHC equipped with RF fin­gers have been re­viewed. The lessons learnt and mit­i­ga­tion mea­sures are pre­sented in this paper.  
 
TUPWA043 Impedance Studies for VMTSA Module of LHC Equipped with RF Fingers 1805
 
  • O. Kononenko, F. Caspers, A. Grudiev, E. Métral, B. Salvant
    CERN, Geneva, Switzerland
  
  Dur­ing 2011 run of LHC it was found that beam-in­duced heat­ing causes many is­sues for ac­cel­er­a­tor com­po­nents. Par­tic­u­larly some of the dou­ble-bel­low mod­ules, called VMTSA mod­ules, were found to have de­formed RF fin­gers and a bro­ken spring which en­sured good con­tact be­tween them and a cen­tral in­sert. Im­ped­ance stud­ies have been per­formed for dif­fer­ent types of non­con­for­mi­ties and bench­marked against mea­sure­ments. It was found that even a small gap be­tween the fin­gers and a cen­tral in­sert could be fatal for the VMTSA op­er­a­tion. Re­sults of this study were an input for the fur­ther ther­mal analy­sis.  
 
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.  
 
WEPEA042 The PS Upgrade Programme: Recent Advances 2594
 
  • S.S. Gilardoni, S. Bart Pedersen, C. Bertone, N. Biancacci, A. Blas, D. Bodart, J. Borburgh, P. Chiggiato, H. Damerau, S. Damjanovic, J.D. Devine, T. Dobers, M. Gourber-Pace, S. Hancock, A. Huschauer, G. Iadarola, L.A. Lopez Hernandez, A. Masi, S. Mataguez, E. Métral, M.M. Paoluzzi, S. Persichelli, S. Pittet, S. Roesler, C. Rossi, G. Rumolo, B. Salvant, R. Steerenberg, G. Sterbini, L. Ventura, J. Vollaire, R. Wasef, C. Yin Vallgren
    CERN, Geneva, Switzerland
  • M. Migliorati
    University of Rome "La Sapienza", Rome, Italy
  
  The LHC In­jec­tors Up­grade pro­ject (LIU) has been ini­ti­ated to im­prove the per­for­mances of the ex­ist­ing in­jec­tor com­plex at CERN to match the fu­ture re­quire­ments of the HL-LHC. In this frame­work, the Pro­ton Syn­chro­tron (PS) will un­dergo fun­da­men­tal changes for many of its main sys­tems: the in­jec­tion en­ergy will be in­creased to re­duce space-charge ef­fects, the trans­verse damper will be im­proved to cope with trans­verse in­sta­bil­i­ties the RF sys­tems will be up­graded to ac­cel­er­ate higher beam in­ten­sity and bright­ness. These hard­ware im­prove­ments are trig­gered by a se­ries of stud­ies meant to iden­tify the most crit­i­cal per­for­mance bot­tle­necks, like space charge, im­ped­ances, lon­gi­tu­di­nal and trans­verse in­sta­bil­i­ties, as well as elec­tron-cloud. Ad­di­tion­ally, al­ter­na­tive pro­duc­tion schemes for the LHC-type beams have been pro­posed and im­ple­mented to cir­cum­vent some of the pre­sent lim­i­ta­tions. A sum­mary of the most re­cent ad­vances of the stud­ies, as well as the pro­posed hard­ware im­prove­ments is given.  
 
WEPEA052 Investigations on CERN PSB Beam Dynamics with Strong Direct Space Charge Effects Using the PTC-ORBIT Code 2621
 
  • V. Forte, E. Benedetto, C. Carli, M. Martini, B. Mikulec, E. Métral, F. Schmidt
    CERN, Geneva, Switzerland
  • A.Y. Molodozhentsev
    KEK, Ibaraki, Japan
  
  The CERN PS Booster (PSB) is the first syn­chro­tron of the LHC in­jec­tor chain con­sist­ing out of four su­per­posed rings and pro­vid­ing beam for many users. As part of the LIU pro­ject, the ma­chine will be up­graded. Space charge and res­o­nances are se­ri­ous is­sues for the good qual­ity of the beam at in­jec­tion en­ergy. Con­se­quently sim­u­la­tions are needed to track the beam in the ma­chine tak­ing into ac­count space charge ef­fects: PTC-OR­BIT has been used as track­ing code. This paper pre­sents sim­u­la­tions re­sults com­pared with the mea­sure­ments for ma­chine per­for­mances eval­u­a­tion and code-bench­mark­ing pur­poses.  
 
WEPEA071 Performance Limitations in the Lhc Due to Parasitic Beam-Beam Encounters - Parameter Dependence, Scaling, and Pacman Effects 2672
 
  • T. Pieloni
    EPFL, Lausanne, Switzerland
  • X. Buffat, R. Calaga, R. Calaga, R. Giachino, W. Herr, E. Métral, G. Papotti, G. Trad
    CERN, Geneva, Switzerland
  • D. Kaltchev
    TRIUMF, Vancouver, Canada
  
  We stud­ied pos­si­ble lim­i­ta­tions due to the long-range beam-beam ef­fects in the LHC. With a large num­ber of bunches and col­li­sions in all in­ter­ac­tion points, we have re­duced the cross­ing an­gles (sep­a­ra­tion) to en­hance long-range beam-beam ef­fects to eval­u­ate their in­flu­ence on dy­namic aper­ture and losses. Dif­fer­ent β*, num­ber of bunches and in­ten­si­ties have been used in sev­eral ded­i­cated ex­per­i­ments and allow the test of the ex­pected scal­ing laws.  
 
THOBB102 Beam Coupling Impedance Localization Technique Validation and Measurements in the CERN Machines 3106
 
  • N. Biancacci, G. Arduini, T. Argyropoulos, H. Bartosik, R. Calaga, K. Cornelis, S.S. Gilardoni, N. Mounet, E. Métral, Y. Papaphilippou, S. Persichelli, G. Rumolo, B. Salvant, G. Sterbini, R. Tomás, R. Wasef
    CERN, Geneva, Switzerland
  • M. Migliorati, L. Palumbo
    URLS, Rome, Italy
  
  The beam cou­pling im­ped­ance could lead to lim­i­ta­tions in beam bright­ness and qual­ity, and there­fore it needs ac­cu­rate quan­tifi­ca­tion and con­tin­u­ous mon­i­tor­ing in order to de­tect and mit­i­gate high im­ped­ance sources. In the CERN ma­chines, for ex­am­ple, kick­ers and col­li­ma­tors are ex­pected to be the main con­trib­u­tors to the total imag­i­nary part of the trans­verse im­ped­ance. In order to de­tect the other sources, a beam based mea­sure­ment was de­vel­oped: from the vari­a­tion of be­ta­tron phase beat­ing with in­ten­sity, it is pos­si­ble to de­tect the lo­ca­tions of main im­ped­ance sources. In this work we pre­sent the ap­pli­ca­tion of the method with beam mea­sure­ments in the CERN PS, SPS and LHC.  
slides icon Slides THOBB102 [7.224 MB]