Author: Steinhagen, R.J.
Paper Title Page
WEPC078 Non-linear Chromaticity Studies of the LHC at Injection 2199
 
  • E.H. Maclean, M. Giovannozzi, F. Schmidt, R.J. Steinhagen, E. Todesco, R. Tomás, G. Vanbavinckhove
    CERN, Geneva, Switzerland
  • R. Bartolini
    JAI, Oxford, United Kingdom
  
  The non-lin­ear chro­matic­i­ty of the LHC has been stud­ied. Mea­sure­ments of vari­a­tion in tune with dp/p on both beams at in­jec­tion op­tics are being com­pared with Q'' and Q''' as cal­cu­lat­ed with the LHC ef­fec­tive model. This model uses the best cur­rent­ly avail­able mea­sure­ments of mag­net­ic field har­mon­ics. An at­tempt is being made to op­ti­mize the b4 and b5 pool-pieces cor­rec­tions in view of the cor­re­spond­ing chro­matic­i­ty terms.  
 
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.  
 
MOPS009 Probing Intensity Limits of LHC-type Bunches in the CERN SPS with Nominal Optics 610
 
  • B. Salvant, G. Adrian, D.J. Allen, O. Andujar, T. Argyropoulos, J. Axensalva, J. Baldy, H. Bartosik, S. Cettour Cave, F. Chapuis, J.F. Comblin, K. Cornelis, D.G. Cotte, K. Cunnington, H. Damerau, M. Delrieux, J.L. Duran-Lopez, A. Findlay, J. Fleuret, F. Follin, P. Freyermuth, H. Genoud, S.S. Gilardoni, A. Guerrero, S. Hancock, K. Hanke, O. Hans, R. Hazelaar, W. Höfle, L.K. Jensen, J. Kuczerowski, Y. Le Borgne, R. Maillet, D. Manglunki, S. Massot, E. Matli, G. Metral, B. Mikulec, E. Métral, J.-M. Nonglaton, E. Ovalle, L. Pereira, F.C. Peters, A. Rey, J.P. Ridewood, G. Rumolo, J.L. Sanchez Alvarez, E.N. Shaposhnikova, R.R. Steerenberg, R.J. Steinhagen, J. Tan, B. Vandorpe, E. Veyrunes
    CERN, Geneva, Switzerland
  
  Some of the up­grade sce­nar­ios of the high-lu­mi­nos­i­ty LHC re­quire large in­ten­si­ty per bunch from the in­jec­tor chain. Sin­gle bunch beams with in­ten­si­ties of up to 3.5 to 4·1011 p/b and nom­i­nal emit­tances were suc­cess­ful­ly pro­duced in the PS Com­plex and de­liv­ered to the SPS in 2010. This con­tri­bu­tion pre­sents re­sults of stud­ies with this new in­tense beam in the SPS to probe sin­gle bunch in­ten­si­ty lim­i­ta­tions with nom­i­nal gamma tran­si­tion. In par­tic­u­lar, the ver­ti­cal Trans­verse Mode Cou­pling In­sta­bil­i­ty (TMCI) thresh­old with low chro­matic­i­ty was ob­served at 1.6·1011 p/b for sin­gle nom­i­nal LHC bunch­es in the SPS. With in­creased ver­ti­cal chro­matic­i­ty, larg­er in­ten­si­ties could be in­ject­ed, stored along the flat bot­tom and ac­cel­er­at­ed up to 450 GeV/c. How­ev­er, sig­nif­i­cant loss­es and/or trans­verse emit­tance blow up were then ob­served. Lon­gi­tu­di­nal and trans­verse op­ti­miza­tion ef­forts in the PSB, PS and SPS were put in place to min­i­mize this beam degra­da­tion and suc­ceed­ed to ob­tain sin­gle 2.3·1011 p/b LHC type bunch­es with sat­is­fy­ing pa­ram­e­ters at ex­trac­tion of the SPS.  
 
THOBA01 Electron Cloud Observations in LHC 2862
 
  • G. Rumolo, G. Arduini, V. Baglin, H. Bartosik, P. Baudrenghien, N. Biancacci, G. Bregliozzi, S.D. Claudet, R. De Maria, J. Esteban Muller, M. Favier, C. Hansen, W. Höfle, J.M. Jimenez, V. Kain, E. Koukovini, G. Lanza, K.S.B. Li, G.H.I. Maury Cuna, E. Métral, G. Papotti, T. Pieloni, F. Roncarolo, B. Salvant, E.N. Shaposhnikova, R.J. Steinhagen, L.J. Tavian, D. Valuch, W. Venturini Delsolaro, F. Zimmermann
    CERN, Geneva, Switzerland
  • C.M. Bhat
    Fermilab, Batavia, USA
  • U. Iriso
    CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
  • N. Mounet, C. Zannini
    EPFL, Lausanne, Switzerland
  
  Op­er­a­tion of LHC with bunch trains dif­fer­ent spac­ings has re­vealed the for­ma­tion of an elec­tron cloud in­side the ma­chine. The main ob­ser­va­tions of elec­tron cloud build-up are the pres­sure rise mea­sured at the vac­u­um gauges in the warm re­gions, as well as the in­crease of the beam screen tem­per­a­ture in the cold re­gions due to an ad­di­tion­al heat load. The ef­fects of the elec­tron cloud were also vis­i­ble as a strong in­sta­bil­i­ty and emit­tance growth af­fect­ing the last bunch­es of longer trains, which could be im­proved run­ning with high­er chro­matic­i­ty and/or larg­er trans­verse emit­tances. A sum­ma­ry of the 2010 and 2011 ob­ser­va­tions and mea­sure­ments and a com­par­i­son with ex­ist­ing mod­els will be pre­sent­ed. The ef­fi­cien­cy of scrub­bing and scrub­bing strate­gies to im­prove the ma­chine run­ning per­for­mance will be also briefly dis­cussed.  
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