Author: Wenninger, J.
Paper Title Page
TUPZ001 90 m Optics Commissioning 1795
 
  • S. Cavalier
    LAL, Orsay, France
  • H. Burkhardt, M. Fitterer, G.J. Müller, S. Redaelli, R. Tomás, G. Vanbavinckhove, J. Wenninger
    CERN, Geneva, Switzerland
  
  Spe­cial β* = 90 m op­tics have been de­vel­oped for the two very high lu­mi­nos­i­ty in­ser­tions of the LHC, as a first step to­wards to allow for very low angle pre­ci­sion mea­sure­ments of the pro­ton-pro­ton col­li­sions in the LHC. These op­tics were de­vel­oped to be com­pat­i­ble with the stan­dard LHC in­jec­tion and ramp op­tics. The tar­get value of β* = 90 m is reached by an un-squeeze from the in­jec­tion β* = 11 m. We de­scribe the im­ple­men­ta­tion of this op­tics in the LHC and the first ex­pe­ri­ence in the com­mis­sion­ing of these op­tics.  
 
TUPZ006 Aperture Determination in the LHC Based on an Emittance Blowup Technique with Collimator Position Scan 1810
 
  • R.W. Assmann, R. Bruce, M. Giovannozzi, G.J. Müller, S. Redaelli, F. Schmidt, R. Tomás, J. Wenninger, D. Wollmann
    CERN, Geneva, Switzerland
  • M. Alabau
    IFIC, Valencia, Spain
  
  A new method to de­ter­mine the LHC aper­ture was pro­posed. The new com­po­nent is a col­li­ma­tor scan tech­nique that refers the glob­al­ly mea­sured aper­ture limit to the shad­ow of the pri­ma­ry col­li­ma­tor, ex­pressed in σs of rms beam size. As a by-prod­uct the BLM re­sponse to beam loss is quan­ti­fied. The method is de­scribed and LHC mea­sure­ment re­sults are pre­sent­ed.  
 
TUPZ009 LHC Machine Protection against Very Fast Crab Cavity Failures 1816
 
  • T. Baer, R. Tomás, J. Tückmantel, J. Wenninger, F. Zimmermann
    CERN, Geneva, Switzerland
  • T. Baer
    Uni HH, Hamburg, Germany
  • R. Calaga
    BNL, Upton, Long Island, New York, USA
  
  For the high-lu­mi­nos­i­ty LHC up­grade pro­gram (HL-LHC), the in­stal­la­tion of crab cav­i­ties (CCs) is es­sen­tial to com­pen­sate the ge­o­met­ric lu­mi­nos­i­ty loss due to the cross­ing angle. The base­line is a local scheme with CCs around the ATLAS and CMS ex­per­i­ments. In a fail­ure case (e.g. a CC quench), the volt­age and/or phase of a CC can change sig­nif­i­cant­ly with a fast time con­stant of the order of a LHC turn. This can lead to large, glob­al be­ta­tron os­cil­la­tions of the beam. Against the back­ground of ma­chine pro­tec­tion, the in­flu­ence of a CC fail­ure on the beam dy­nam­ics is dis­cussed. The re­sults from ded­i­cat­ed track­ing stud­ies, in­clud­ing the LHC up­grade op­tics, are pre­sent­ed. Nec­es­sary coun­ter­mea­sures to limit the im­pact of CC fail­ures to an ac­cept­able level are pro­posed.  
 
TUPZ016 First Run of the LHC as a Heavy-ion Collider 1837
 
  • J.M. Jowett, G. Arduini, R.W. Assmann, P. Baudrenghien, C. Carli, M. Lamont, M. Solfaroli Camillocci, J.A. Uythoven, W. Venturini Delsolaro, J. Wenninger
    CERN, Geneva, Switzerland
  
  A year of LHC op­er­a­tion typ­i­cal­ly con­sists of an ex­tend­ed run with col­lid­ing pro­tons, end­ing with a month in which the LHC has to switch to its sec­ond role as a heavy ion col­lid­er and pro­vide a use­ful in­te­grat­ed lu­mi­nos­i­ty to three ex­per­i­ments. The first such run in Novem­ber 2010 demon­strat­ed that this is fea­si­ble. Com­mis­sion­ing was ex­treme­ly rapid, with col­li­sions of Pb nu­clei achieved with­in 55 h of first in­jec­tion. Sta­ble beams for physics da­ta-tak­ing were de­clared a lit­tle over one day later and the final in­te­grat­ed lu­mi­nos­i­ty sub­stan­tial­ly ex­ceed­ed ex­pec­ta­tions.  
 
TUPZ028 Beam Based Optimization of the Squeeze at the LHC 1867
 
  • X. Buffat
    EPFL, Lausanne, Switzerland
  • M. Lamont, S. Redaelli, J. Wenninger
    CERN, Geneva, Switzerland
  
  The be­ta­tron squeeze is a crit­i­cal op­er­a­tional phase for the LHC be­cause it is car­ried out at top en­er­gy, with the max­i­mum stored en­er­gy and with re­duced aper­ture mar­gins in the su­per­con­duct­ing triplets. A sta­ble op­er­a­tion with min­i­mum beam loss­es must be achieved in order to en­sure a safe and ef­fi­cient op­er­a­tion. The op­er­a­tional ex­pe­ri­ence at the LHC showed that this is pos­si­ble. The op­er­a­tion in 2010 is re­viewed. In par­tic­u­lar, orbit, tune and chro­matic­i­ty mea­sure­ments are in­ves­ti­gat­ed and cor­re­lat­ed to beam loss­es. Dif­fer­ent op­ti­miza­tions are then pro­posed to­wards a more ef­fi­cient and ro­bust op­er­a­tion. The im­prove­ments ob­tained for the op­er­a­tion in 2011 are pre­sent­ed.  
 
MOPS010 Experimental Studies with Low Transition Energy Optics in the SPS 613
 
  • H. Bartosik, T. Argyropoulos, T. Bohl, S. Cettour Cave, K. Cornelis, J. Esteban Muller, Y. Papaphilippou, G. Rumolo, B. Salvant, E.N. Shaposhnikova, J. Wenninger
    CERN, Geneva, Switzerland
  
  The op­tics of the SPS can be tuned to lower tran­si­tion en­er­gy such that the slip­page fac­tor at in­jec­tion is raised by a fac­tor of al­most 3. From the­o­ry, an in­crease of the in­ten­si­ty thresh­olds for trans­verse mode cou­pling, lon­gi­tu­di­nal cou­pled bunch and lon­gi­tu­di­nal in­sta­bil­i­ties due to the loss of Lan­dau damp­ing can be ex­pect­ed. In this paper, ex­per­i­men­tal stud­ies in the SPS with sin­gle bunch­es of pro­tons with in­ten­si­ties of up to 3.5·1011 p/b on the flat bot­tom and at 450 GeV/c are pre­sent­ed. Lon­gi­tu­di­nal in­sta­bil­i­ties were stud­ied with LHC-type beams with 50~ns spac­ing and in­ject­ed in­ten­si­ties up to 1.8·1011 p/b. The mea­sure­ments ad­dress the in­crease of in­ten­si­ty thresh­olds and the achiev­able trans­verse emit­tances in the new low gamma tran­si­tion op­tics with re­spect to the nom­i­nal SPS op­tics. The ob­tained re­sults are com­pared with nu­mer­i­cal sim­u­la­tions.  
 
TUPC136 Analysis of Fast Losses in the LHC with the BLM System 1344
 
  • E. Nebot Del Busto, T. Baer, B. Dehning, E. Effinger, J. Emery, E.B. Holzer, A. Marsili, A. Nordt, M. Sapinski, R. Schmidt, B. Velghe, J. Wenninger, C. Zamantzas, F. Zimmermann
    CERN, Geneva, Switzerland
  • N. Fuster
    Valencia University, Atomic Molecular and Nuclear Physics Department, Valencia, Spain
  • Z. Yang
    EPFL, Lausanne, Switzerland
  
  About 3600 Ion­iza­tion Cham­bers are lo­cat­ed around the LHC ring to de­tect beam loss­es that could dam­age the equip­ment or quench su­per­con­duct­ing mag­nets. The BLMs in­te­grate the loss­es in 12 dif­fer­ent time in­ter­vals (from 40 us to 83.8 s) al­low­ing for dif­fer­ent abort thresh­olds de­pend­ing on the du­ra­tion of the loss and the beam en­er­gy. The sig­nals are also record­ed in a database at 1 Hz for of­fline anal­y­sis. Dur­ing the 2010 run, a lim­it­ing fac­tor in the ma­chine avail­abil­i­ty were sud­den loss­es ap­pear­ing around the ring on the ms time scale and de­tect­ed ex­clu­sive­ly by the BLM sys­tem. It is be­lieved that such loss­es orig­i­nate from dust par­ti­cles falling into the beam, or being at­tract­ed by its strong elec­tro­mag­net­ic field. This doc­u­ment de­scribes some of the prop­er­ties of these "Uniden­ti­fied Falling Ob­jects" (UFOs) putting spe­cial em­pha­sis on their de­pen­dence on beam pa­ram­e­ters (en­er­gy, in­ten­si­ty, etc). The sub­se­quent mod­i­fi­ca­tion of the BLM beam abort thresh­olds for the 2011 run that were made to avoid un­nec­es­sary beam dumps caused by these UFO loss­es are also dis­cussed.  
 
TUPC137 UFOs in the LHC 1347
 
  • T. Baer, M.J. Barnes, B. Goddard, E.B. Holzer, J.M. Jimenez, A. Lechner, V. Mertens, E. Nebot Del Busto, A. Nordt, J.A. Uythoven, B. Velghe, J. Wenninger, F. Zimmermann
    CERN, Geneva, Switzerland
  
  One of the major known lim­i­ta­tions for the per­for­mance of the Large Hadron Col­lid­er are so called UFOs (”Uniden­ti­fied Falling Ob­jects”). UFOs were first ob­served in July 2010 and have since caused nu­mer­ous pro­tec­tion beam dumps. UFOs are thought to be mi­crom­e­ter sized dust par­ti­cles which lead to fast beam loss­es with a du­ra­tion of about 10 turns when they in­ter­act with the beam. In 2011, the di­ag­nos­tics for such events was sig­nif­i­cant­ly im­proved which al­lows es­ti­mates of the prop­er­ties, dy­nam­ics and pro­duc­tion mech­a­nisms of the dust par­ti­cles. The state of knowl­edge and mit­i­ga­tion strate­gies are pre­sent­ed.  
 
TUPS026 Specification of New Vacuum Chambers for the LHC Experimental Interactions 1584
 
  • R. Veness, R.W. Assmann, A. Ball, A. Behrens, C. Bracco, G. Bregliozzi, R. Bruce, H. Burkhardt, G. Corti, M.A. Gallilee, M. Giovannozzi, B. Goddard, D. Mergelkuhl, E. Métral, M. Nessi, W. Riegler, J. Wenninger
    CERN, Geneva, Switzerland
  • N. Mounet, B. Salvant
    EPFL, Lausanne, Switzerland
  
  The aper­tures for the vac­u­um cham­bers at the in­ter­ac­tion points in­side the LHC ex­per­i­ments are key both to the safe op­er­a­tion of the LHC ma­chine and to ob­tain­ing the best physics per­for­mance from the ex­per­i­ments. Fol­low­ing the suc­cess­ful start­up of the LHC physics pro­gramme the ALICE, ATLAS and CMS ex­per­i­ments have launched pro­jects to im­prove physics per­for­mance by adding de­tec­tor lay­ers clos­er to the beam. To achieve this they have re­quest­ed small­er aper­ture vac­u­um cham­bers to be in­stalled. The first pe­ri­ods of LHC op­er­a­tion have yield­ed much in­for­ma­tion both on the per­for­mance of the LHC and the sta­bil­i­ty and align­ment of the ex­per­i­ments. In this paper, the new in­for­ma­tion re­lat­ing to the aper­ture of these cham­bers is pre­sent­ed and a sum­ma­ry is made of anal­y­sis of pa­ram­e­ters re­quired to safe­ly re­duce the vac­u­um cham­bers aper­tures for the high-lu­mi­nos­i­ty ex­per­i­ments ATLAS and CMS.  
 
WEPC173 LHC Magnet Quench Test with Beam Loss Generated by Wire Scan 2391
 
  • M. Sapinski, F. Cerutti, K. Dahlerup-Petersen, B. Dehning, J. Emery, A. Ferrari, A. Guerrero, E.B. Holzer, M. Koujili, A. Lechner, E. Nebot Del Busto, M. Scheubel, J. Steckert, A.P. Verweij, J. Wenninger
    CERN, Geneva, Switzerland
  
  Beam loss­es with mil­lisec­ond du­ra­tion have been ob­served in the LHC in 2010 and 2011. They are ex­pect­ed to be pro­voked by dust par­ti­cles falling into the beam. These loss­es could com­pro­mise the LHC avail­abil­i­ty if they pro­voke quench­es of su­per­con­duct­ing mag­nets. In order to in­ves­ti­gate the quench lim­its for this loss mech­a­nism, a quench test using the wire scan­ner has been per­formed, with the wire move­ment through the beam mim­ick­ing a loss with sim­i­lar spa­tial and tem­po­ral dis­tri­bu­tion as in the case of dust par­ti­cles. This paper will show the con­clu­sions reached for mil­lisec­ond-du­ra­tion dust-pro­voked quench lim­its. It will in­clude de­tails on the max­i­mum en­er­gy de­posit­ed in the coil as es­ti­mat­ed using FLUKA code, show­ing good agree­ment with quench limit es­ti­mat­ed from the heat trans­fer code QP3. In ad­di­tion, in­for­ma­tion on the dam­age limit for car­bon wires in pro­ton beams will be pre­sent­ed, fol­low­ing elec­tron mi­cro­scope anal­y­sis which re­vealed strong wire sub­li­ma­tion.  
 
WEPO031 The Magnetic Model of the LHC during Commissioning to Higher Beam Intensities in 2010-2011 2466
 
  • L. Deniau, N. Aquilina, L. Fiscarelli, M. Giovannozzi, P. Hagen, M. Lamont, G. Montenero, R.J. Steinhagen, M. Strzelczyk, E. Todesco, R. Tomás, W. Venturini Delsolaro, J. Wenninger
    CERN, Geneva, Switzerland
  
  The Field De­scrip­tion of the Large Hadron Col­lid­er (FiDeL) model is a set of se­mi-em­pir­i­cal equa­tions link­ing the mag­nets be­haviours es­tab­lished from mag­net­ic mea­sure­ments to the mag­net­ic prop­er­ties of the ma­chine ob­served through beam mea­sure­ments. The FiDeL model in­cludes the pa­ram­e­ter­i­za­tion of stat­ic com­po­nents such as mag­nets resid­u­al mag­ne­ti­za­tion, per­sis­tent cur­rents, hys­tere­sis and sat­u­ra­tion as well as the decay and snap-back dy­nam­ic com­po­nents. In the pre­sent paper, we out­line the re­la­tion­ship be­tween the beam ob­serv­ables (orbit, tune, chro­matic­i­ty) and the model com­po­nents dur­ing the com­mis­sion­ing to high­er beam in­ten­si­ties in 2010-2011, with an en­er­gy of 3.5 TeV per beam. The main rel­e­vant is­sues are (i) the op­er­a­tion at 2 A/s and 10 A/s ramp rate and their in­flu­ence on chro­mat­ic cor­rec­tion, (ii) the beta beat­ing and its re­la­tion to the knowl­edge of the re­sis­tive quadrupoles trans­fer func­tions and (iii) the ob­served tune decay at in­jec­tion en­er­gy and its pos­si­bles ori­gins.  
 
WEPS022 Ions for LHC: Performance of the Injector Chain 2529
 
  • D. Manglunki, M. E. Angoletta, P. Baudrenghien, G. Bellodi, A. Blas, T. Bohl, C. Carli, E. Carlier, S. Cettour Cave, M. Chanel, K. Cornelis, H. Damerau, A. Findlay, S.S. Gilardoni, S. Hancock, J.M. Jowett, D. Kuchler, S. Maury, E. Métral, S. Pasinelli, M. Schokker, G. Tranquille, B. Vandorpe, U. Wehrle, J. Wenninger
    CERN, Geneva, Switzerland
  
  The first LHC Pb ion run took place at 1.38 A TeV/c per beam in au­tumn 2010. After a short pe­ri­od of run­ning-in, the in­jec­tor chain was able to fill the col­lid­er with up to 137 bunch­es per ring, with an in­ten­si­ty of 108 Pb ions/bunch, about 50% high­er than the de­sign value. This yield­ed a lu­mi­nos­i­ty of 3E25 Hz/cm2, al­low­ing the ex­per­i­ments to ac­cu­mu­late just under 10 in­verse mi­cro­barn each dur­ing the four week run. We re­view the per­for­mance of the in­di­vid­u­al links of the in­jec­tor chain, and ad­dress the main is­sues lim­it­ing the LHC lu­mi­nos­i­ty, in view of reach­ing 1026 Hz/cm2 in 2011, and sub­stan­tial­ly be­yond when the LHC en­er­gy in­creas­es after the long shut­down in 2013-14.  
 
THPZ025 Stability of the LHC Transfer lines 3741
 
  • V. Kain, W. Bartmann, C. Bracco, L.N. Drosdal, B. Goddard, M. Meddahi, J.A. Uythoven, J. Wenninger
    CERN, Geneva, Switzerland
  
  The LHC is filled from the SPS through two 3 km trans­fer lines. The in­ject­ed beam pa­ram­e­ters need to be well under con­trol for lu­mi­nos­i­ty per­for­mance, ma­chine pro­tec­tion and op­er­a­tional ef­fi­cien­cy. Small frac­tions of beam loss on the trans­fer line col­li­ma­tion sys­tem cre­ate show­ers which can trig­ger the sen­si­tive LHC beam loss mon­i­tor sys­tem near­by and cause a beam abort dur­ing fill­ing. The sta­bil­i­ty of the trans­fer line tra­jec­to­ry through the col­li­ma­tors is par­tic­u­lar­ly crit­i­cal in this re­spect. This paper will re­port on the trans­fer line tra­jec­to­ry sta­bil­i­ty dur­ing the pro­ton run in 2011, cor­re­la­tions with in­jec­tion loss­es, cor­rec­tion fre­quen­cy and the most like­ly sources for the ob­served os­cil­la­tions.  
 
THPS053 Results from the HiRadMat Primary Beam Line Commissioning 3547
 
  • C. Heßler, M. Arruat, J. Bauche, K. Bestmann, J. Blanco, N. Conan, K. Cornelis, I. Efthymiopoulos, H. Gaillard, B. Goddard, D. Grenier, G.G. Gros, A. Habert, L.K. Jensen, V. Kain, G. Le Godec, M. Meddahi, S. Pelletier, P. Pepinster, B. Puccio, C. Theis, P. Trilhe, G. Vandoni, J. Wenninger
    CERN, Geneva, Switzerland
  
  The High Ra­di­a­tion to Ma­te­ri­als fa­cil­i­ty (Hi­Rad­Mat) is a new ex­per­i­men­tal area at CERN, for stud­ies of the im­pact of high-in­ten­si­ty pulsed beams on ac­cel­er­a­tor com­po­nents and ma­te­ri­als. The beam is de­liv­ered from the SPS by a new pri­ma­ry beam line, which has been con­struct­ed dur­ing the 2010/11 win­ter tech­ni­cal stop. The paper sum­ma­rizes the con­struc­tion phase and de­scribes the re­sults from the beam line com­mis­sion­ing in spring 2011. Beam pa­ram­e­ter and aper­ture mea­sure­ments are pre­sent­ed, as well as steer­ing tests. A spe­cial em­pha­sis has been put on the han­dling of the ex­cep­tion­al­ly flex­i­ble beam line op­tics in the con­trol sys­tem.