Author: Dehning, B.
Paper Title Page
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.  
 
WEPC170 Handling of BLM Abort Thresholds in the LHC 2382
 
  • E. Nebot Del Busto, B. Dehning, E.B. Holzer, S. Jackson, G. Kruk, M. Nemcic, A. Nordt, A. Orecka, C. Roderick, M. Sapinski, A. Skaugen, C. Zamantzas
    CERN, Geneva, Switzerland
  
  The Beam Loss Mon­i­tor­ing sys­tem (BLM) for the LHC con­sists of about 3600 Ion­iza­tion Cham­bers lo­cat­ed around the ring. Its main pur­pose is to re­quest a beam abort when the mea­sured loss­es ex­ceed a cer­tain thresh­old. The BLM de­tec­tors in­te­grate the mea­sured sig­nals in 12 dif­fer­ent time in­ter­vals (run­ning from 40 us to 83.8 s) en­abling for a dif­fer­ent set of abort thresh­olds de­pend­ing on the du­ra­tion of the beam loss. Fur­ther­more, 32 en­er­gy lev­els run­ning from 0 to 7 TeV ac­count for the fact that the en­er­gy den­si­ty of a par­ti­cle show­er in­creas­es with the en­er­gy of the pri­ma­ry par­ti­cle, i.e. the beam en­er­gy. Thus, about 1.3·106 thresh­olds must be han­dled and send to the ap­pro­pri­ate pro­cess­ing mod­ules for the sys­tem to func­tion. These thresh­olds are high­ly crit­i­cal for the safe­ty of the ma­chine and de­pend to a large part on human judg­ment, which can­not be re­placed by au­to­mat­ic test pro­ce­dures. The BLM team has de­fined well es­tab­lished pro­ce­dures to com­pute, set and check new BLM thresh­olds, in order to avoid and/or find non-con­for­mi­ties due to ma­nip­u­la­tion. These pro­ce­dures, as well as the tools de­vel­oped to au­to­mate this pro­cess are de­scribed in de­tail in this doc­u­ment.  
 
WEPC172 Beam-induced Quench Test of a LHC Main Quadrupole 2388
 
  • A. Priebe, K. Dahlerup-Petersen, B. Dehning, E. Effinger, J. Emery, E.B. Holzer, C. Kurfuerst, E. Nebot Del Busto, A. Nordt, M. Sapinski, J. Steckert, A.P. Verweij, C. Zamantzas
    CERN, Geneva, Switzerland
  • A. Priebe
    EPFL, Lausanne, Switzerland
  
  Un­ex­pect­ed beam loss might lead to tran­si­tion of a su­per­con­duct­ing ac­cel­er­a­tor mag­net to a nor­mal con­duct­ing state. The LHC beam loss mon­i­tor­ing (BLM) sys­tem is de­signed to abort the beam be­fore the en­er­gy de­posit­ed in the mag­net coils reach­es a quench-pro­vok­ing level. In order to ver­i­fy the thresh­old set­tings gen­er­at­ed by sim­u­la­tion, a se­ries of beam-in­duced quench tests at var­i­ous beam en­er­gies have been per­formed. The beam loss­es are gen­er­at­ed by means of an orbit bump peaked in one of the main quadrupole mag­nets. The anal­y­sis not only in­cludes BLM data but also data from the elec­tri­cal quench pro­tec­tion and cryo­genic sys­tems. The mea­sure­ments are com­pared to Gean­t4 sim­u­la­tions of en­er­gy de­po­si­tion in­side the coils and cor­re­spond­ing BLM sig­nal out­side the cryo­stat. The re­sults are also ex­trap­o­lat­ed to high­er beam en­er­gies.  
 
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.  
 
THOAA03 Overview of LHC Beam Loss Measurements 2854
 
  • B. Dehning, A.E. Dabrowski, M. Dabrowski, E. Effinger, J. Emery, E. Fadakis, V. Grishin, E.B. Holzer, S. Jackson, G. Kruk, C. Kurfuerst, A. Marsili, M. Misiowiec, E. Nebot Del Busto, A. Nordt, A. Priebe, C. Roderick, M. Sapinski, C. Zamantzas
    CERN, Geneva, Switzerland
  • E. Griesmayer
    CIVIDEC Instrumentation, Wien, Austria
  
  The LHC beam loss mon­i­tor­ing sys­tem based on ion­iza­tion cham­bers is used for ma­chine pro­tec­tion, quench pre­ven­tion and ac­cel­er­a­tor op­ti­miza­tion. After one full year of op­er­a­tion it can be stat­ed that its main func­tion­al­i­ty, that of the pro­tec­tion of equip­ment, has proven to be very ro­bust with no is­sues ob­served for hun­dreds of crit­i­cal beam loss events and the num­ber of false beam aborts well below ex­pec­ta­tion. In ad­di­tion the in­jec­tion, dump and col­li­ma­tion sys­tem make reg­u­lar use of the pub­lished loss mea­sure­ments for sys­tem anal­y­sis and op­ti­mi­sa­tion, such as the de­ter­mi­na­tion of col­li­ma­tion ef­fi­cien­cy in order to iden­ti­fy pos­si­ble in­ten­si­ty lim­i­ta­tions as early as pos­si­ble. In­ten­tion­al mag­net quench­es have been per­formed to ver­i­fy both the cal­i­bra­tion ac­cu­ra­cy of the sys­tem and the ac­cu­ra­cy of the loss pat­tern pre­dic­tions from sim­u­la­tions. Tests have also been per­formed with fast loss de­tec­tors based on sin­gle- and poly­crys­talline CVD di­a­mond, which are ca­pa­ble of pro­vid­ing nanosec­ond res­o­lu­tion time loss struc­ture. This pre­sen­ta­tion will cover all of these as­pects and give an out­look on fu­ture per­for­mance.  
slides icon Slides THOAA03 [1.972 MB]  
 
THPS055 Controlling Beamloss at Injection into the LHC 3553
 
  • B. Goddard, F. Alessio, W. Bartmann, P. Baudrenghien, V. Boccone, C. Bracco, M. Brugger, K. Cornelis, B. Dehning, A. Di Mauro, L.N. Drosdal, E.B. Holzer, W. Höfle, R. Jacobsson, V. Kain, M. Meddahi, V. Mertens, A. Nordt, J.A. Uythoven, D. Valuch, S. Weisz, E.N. del Busto
    CERN, Geneva, Switzerland
  • R. Appleby
    UMAN, Manchester, United Kingdom
  
  Loss­es at in­jec­tion into the su­per­con­duct­ing LHC can ad­verse­ly af­fect the ma­chine per­for­mance in sev­er­al im­por­tant ways. The high in­ject­ed beam in­ten­si­ty and en­er­gy mean that pre­cau­tions must be taken against dam­age and quench­es, in­clud­ing col­li­ma­tors placed close to the beam in the in­jec­tion re­gions. Clean in­jec­tion is es­sen­tial, to avoid spu­ri­ous sig­nals on the sen­si­tive beam loss mon­i­tor­ing sys­tem which will trig­ger beam dumps. In ad­di­tion, the use of the two in­jec­tion in­ser­tions to house down­stream high en­er­gy physics ex­per­i­ments brings con­straints on per­mit­ted beam loss lev­els. In this paper the sources of in­jec­tion beam loss are dis­cussed to­geth­er with the con­tribut­ing fac­tors and var­i­ous is­sues ex­pe­ri­enced in the first full year of LHC op­er­a­tion. Sim­u­la­tions are com­pared with mea­sure­ment, and the im­ple­ment­ed and planned mit­i­ga­tion mea­sures and di­ag­nos­tic im­prove­ments are de­scribed. An out­look for fu­ture LHC op­er­a­tion is given.