• E. Todesco, N. Aquilina, B. Auchmann, L. Bottura, M.C.L. Buzio, R. Chritin, G. Deferne, L. Deniau, L. Fiscarelli, J. Garcia Perez, M. Giovannozzi, P. Hagen, M. Lamont, G. Montenero, G.J. Müller, S. Redaelli, RV. Remondino, F. Schmidt, R.J. Steinhagen, M. Strzelczyk, M. Terra Pinheiro Fernandes Pereira, R. Tomás, W. Venturini Delsolaro, J. Wenninger, R. Wolf
  CERN, Geneva
• N.J. Sammut
  University of Malta, Faculty of Engineering, Msida

The re­la­tion be­tween field and cur­rent in each fam­i­ly of the Large Hadron Col­lid­er mag­nets is mod­eled with a set of em­pir­i­cal equa­tions (FiDeL) whose free pa­ram­e­ters are fit­ted on mag­net­ic mea­sure­ments. They take into ac­count of resid­u­al mag­ne­ti­za­tion, per­sis­tent cur­rents, hys­tere­sis, sat­u­ra­tion, decay and snap­back dur­ing ini­tial part of the ramp. Here we give a first sum­ma­ry of the re­con­struc­tion of the mag­net­ic field prop­er­ties based on the beam ob­serv­ables (orbit, tune, cou­pling, chro­matic­i­ty) and a com­par­i­son with the ex­pec­ta­tions based on the large set of mag­net­ic mea­sure­ments car­ried out dur­ing the 5-years-long pro­duc­tion. The most crit­i­cal is­sues for the ma­chine per­for­mance in terms of knowl­edge of the re­la­tion mag­net­ic field vs cur­rent are pinned out.

Slides

• B.J. Holzer, S.D. Fartoukh, F. Schmidt
  CERN, Geneva

The lay­out of the in­ter­ac­tion re­gion for the LHC up­grade pro­ject is based on a num­ber of new mag­nets that will pro­vide the re­quired strengths to focus the col­lid­ing beams as well as to sep­a­rate them after the col­li­sion. As in the nom­i­nal LHC, a triplet of quadrupole mag­nets is fore­seen for the up­grade op­tics and in ad­di­tion a sep­a­ra­tor dipole to limit the par­a­sitic bunch cross­ings of the two counter ro­tat­ing bunch trains. Due to the small­er beta func­tion at the IP how­ev­er, the re­quire­ments for the free aper­ture of these IR mag­nets are more de­mand­ing and the ef­fect of the high­er order mul­ti­poles is more se­vere than under the nom­i­nal LHC con­di­tions. Using the track­ing sim­u­la­tions to study these ef­fects, tar­get val­ues for the mul­ti­pole co­ef­fi­cients of the new mag­nets have been de­fined as well as a mul­ti­pole cor­rec­tion scheme that will be used to com­pen­sate those field er­rors which can­not be avoid­ed due to de­sign and con­struc­tion tol­er­ances. Based on these con­sid­er­a­tions the re­quired field qual­i­ty of the new LHC low beta mag­nets is dis­cussed and the re­sult­ing dy­nam­ic aper­ture for dif­fer­ent mul­ti­pole cor­rec­tion scheme is pre­sent­ed.

• K. Fuchsberger, S.D. Fartoukh, B. Goddard, V. Kain, M. Meddahi, F. Schmidt, J. Wenninger
  CERN, Geneva

The trans­fer lines from the SPS to the LHC, TI2 and TI8, with a total length of al­most 6km are the longest ones in the world. For that rea­son even small sys­tem­at­ic op­tics er­rors are not neg­li­gi­ble be­cause they add up and re­sult in an in­jec­tion mis­match in the LHC. Next to other lat­tice mea­sure­ment meth­ods Kick-re­sponse mea­sure­ments were the most im­por­tant sources of in­for­ma­tion dur­ing the early phas­es of beam com­mis­sion­ing of these trans­fer lines and the LHC ring. This mea­sure­ment tech­nique was used to ver­i­fy or­bit-cor­rec­tor and BPM gains as well as to sort out op­tics er­rors. Fur­ther­more fits to off-mo­men­tum kick re­sponse turned out to be an ap­pro­pri­ate method to es­tab­lish a model for sys­tem­at­ic er­rors of the trans­fer line mag­nets. This paper short­ly de­scribes the tools and meth­ods de­vel­oped for the anal­y­sis of the taken data and pre­sents the most im­por­tant re­sults of the anal­y­sis.

• K. Fuchsberger, V. Baggiolini, R. Gorbonosov, W. Herr, V. Kain, G.J. Müller, S. Redaelli, F. Schmidt, J. Wenninger
  CERN, Geneva

MADX (Me­thod­i­cal Ac­cel­er­a­tor De­sign) is the de-fac­to stan­dard soft­ware for mod­el­ing ac­cel­er­a­tor lat­tices at CERN. This fea­ture-rich soft­ware pack­age is im­ple­ment­ed and main­tained in the pro­gram­ming lan­guages C and FOR­TRAN. Nev­er­the­less the con­trols en­vi­ron­ment of mod­ern ac­cel­er­a­tors at CERN, e.g. of the LHC, is dom­i­nat­ed by JAVA ap­pli­ca­tions. A lot of these ap­pli­ca­tions, for ex­am­ple for lat­tice mea­sure­ment and fit­ting, re­quire a close in­ter­ac­tion with the nu­mer­i­cal mod­els, which are all de­fined by the use of the pro­pri­etary MADX script­ing lan­guage. To close this gap an API to MADX for the JAVA pro­gram­ming lan­guage (JMAD) was de­vel­oped. Al­ready the cur­rent im­ple­men­ta­tion pro­vides ac­cess to a large sub­set of the MADX ca­pa­bil­i­ties (e.g. twiss-cal­cu­la­tions, match­ing or query­ing and set­ting ar­bi­trary model pa­ram­e­ters) with­out any ne­ces­si­ty to de­fine the mod­els in yet an­oth­er en­vi­ron­ment. This paper de­scribes short­ly the de­sign of this pro­ject as well as the cur­rent sta­tus and some usage ex­am­ples.

• S. Redaelli, M.C. Alabau Pons, M. Giovannozzi, G.J. Müller, F. Schmidt, R. Tomás, J. Wenninger
  CERN, Geneva

The me­chan­i­cal aper­ture of the Large Hadron Col­lid­er (LHC) is a crit­i­cal pa­ram­e­ter for the op­er­a­tion of the ma­chine due to the high stored beam in­ten­si­ties in the su­per­con­duct­ing en­vi­ron­ment. Be­ta­tron and mo­men­tum aper­tures must be there­fore pre­cise­ly mea­sured and op­ti­mized. In this paper, we pre­sent the re­sults of beam-based mea­sure­ments of the LHC aper­ture. The ex­per­i­men­tal re­sults are com­pared with the ex­pec­ta­tions from the as-built model of the LHC aper­ture, tak­ing into ac­count the op­tics im­per­fec­tions of the su­per­con­duct­ing mag­nets. The im­pact of these mea­sure­ments on var­i­ous as­pects of the LHC op­er­a­tion are also dis­cussed.

• S. Redaelli, M.C. Alabau Pons, K. Fuchsberger, M. Giovannozzi, M. Lamont, G.J. Müller, F. Schmidt
  CERN, Geneva
• X. Buffat
  EPFL, Lausanne

The con­trol of the high in­ten­si­ty beams of the CERN Large Hadron Col­lid­er (LHC) is par­tic­u­lar chal­leng­ing and re­quires a pre­cise knowl­edge of the crit­i­cal beam and ma­chine pa­ram­e­ters. In re­cent years ef­forts were de­vot­ed to the de­sign of a soft­ware in­fras­truc­ture aimed at mim­ick­ing the be­hav­ior of the LHC. An on­line model of the ma­chine, based on the ac­cel­er­a­tor de­sign tool MADX, has been de­vel­oped to sup­port the com­mis­sion­ing and the op­er­a­tion of the LHC. This model is in­te­grat­ed into the JA­VA-based LHC soft­ware frame­work and pro­vides the full com­put­ing power of MADX, in­clud­ing the best knowl­edge of the ma­chine aper­ture and mag­net­ic mod­els. The MADX im­ple­men­ta­tion is serv­er-based and pro­vides var­i­ous fa­cil­i­ties for op­tics com­pu­ta­tion to other ap­pli­ca­tion clients. In this paper, we pre­sent the sta­tus of the MADX on­line ap­pli­ca­tion and il­lus­trate how it has been used dur­ing the LHC com­mis­sion­ing. Pos­si­ble fu­ture im­ple­men­ta­tions are also dis­cussed.

• R. Tomás, O.S. Brüning, M. Giovannozzi, M. Lamont, F. Schmidt, G. Vanbavinckhove
  CERN, Geneva
• M. Aiba
  PSI, Villigen
• R. Calaga, R. Miyamoto
  BNL, Upton, Long Island, New York

Op­tics sta­bil­i­ty dur­ing all phas­es of op­er­a­tion is cru­cial for the LHC. The op­ti­cal prop­er­ties of the ma­chine have been op­ti­mized based on a de­tailed mag­net­ic model of the SC mag­nets and on their sort­ing. Tools and pro­ce­dures have been de­vel­oped for rapid checks of beta beat­ing, dis­per­sion, and lin­ear cou­pling, as well as for prompt op­tics cor­rec­tion. Ini­tial op­tics er­rors, cor­rec­tion per­for­mance and op­tics sta­bil­i­ty from the first LHC run will be re­port­ed, and com­pared with ex­pec­ta­tions. Pos­si­ble im­pli­ca­tions for the col­li­ma­tion clean­ing ef­fi­cien­cy and LHC ma­chine pro­tec­tion will be dis­cussed.

Slides

• E. Laface, S.D. Fartoukh, F. Schmidt
  CERN, Geneva

The Phase I Lu­mi­nos­i­ty Up­grade of LHC (SLHC) will be based on a new Nb-Ti inner triplet for the high lu­mi­nos­i­ty re­gion ATLAS and CMS. The new pro­posed lay­out aims at push­ing beta* down to 30 cm re­plac­ing the cur­rent LHC inner triplet, with longer ones op­er­at­ing at lower gra­di­ent (123 T/m) and there­fore of­fer­ing enough aper­ture for the beam to re­duce beta* to its pre­scribed value. As a con­se­quence of this new longer in­ter­ac­tion re­gion, the num­ber of par­a­sitic en­coun­ters will in­crease from 15 to 21 be­fore the sep­a­ra­tion dipole D1, with an im­pact on the dy­nam­ic aper­ture of the ma­chine. In this paper the ef­fect of the beam-beam in­ter­ac­tion is eval­u­at­ed for the SLHC lay­out and op­tics, at in­jec­tion and in col­li­sion, eval­u­at­ing the pos­si­ble im­pact of a few ad­di­tion­al par­a­sitic col­li­sions in­side and be­yond the D1 sep­a­ra­tion dipole till the two beams do no longer oc­cu­py the same vac­u­um cham­ber. When­ev­er need­ed, a com­par­i­son with the nom­i­nal LHC will be given. Then a pos­si­ble back­up col­li­sion op­tics will be dis­cussed for the SLHC, of­fer­ing a much wider cross­ing angle at an in­ter­me­di­ate beta* of 40 cm in order to reach a tar­get dy­nam­ic aper­ture of 7.5 σ.

• R. Bartolini, G. Rehm, J. Rowland
  Diamond, Oxfordshire
• P. Kuske
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
• I.P.S. Martin
  JAI, Oxford
• F. Schmidt
  CERN, Geneva

The cor­rect im­ple­men­ta­tion of the non­lin­ear ring model is cru­cial to achieve the top per­for­mance of a syn­chrotron light source. Sev­er­al dy­nam­ics quan­ti­ties can be used to com­pare the real ma­chine with the model and even­tu­al­ly to cor­rect the ac­cel­er­a­tor. Most of these meth­ods are based on the anal­y­sis of turn-by-turn data of ex­cit­ed be­ta­tron os­cil­la­tions. We pre­sent the ex­per­i­men­tal re­sults of the cam­paign of mea­sure­ments car­ried out at the Di­a­mond. A com­bi­na­tion of Fre­quen­cy Map Anal­y­sis and res­o­nant driv­ing terms mea­sure­ments has al­lowed a pre­cise cal­i­bra­tion of the non­lin­ear model ca­pa­ble of re­pro­duc­ing and then cor­rect­ing the non­lin­ear beam dy­nam­ics in the stor­age ring.