• M. Olvegård, E. Bravin, F. Carra, N.C. Chritin, A.E. Dabrowski, A. Dallocchio, S. Döbert, T. Lefèvre
  CERN, Geneva
• E. Adli
  University of Oslo, Oslo

The CLIC study is based on the so‐called two‐beam ac­cel­er­a­tion con­cept and one of the main goals of the CLIC Test Fa­cil­i­ty 3 is to demon­strate the ef­fi­cien­cy of the CLIC RF power pro­duc­tion scheme. As part of this fa­cil­i­ty a Test Beam Line (TBL), present­ly under com­mis­sion­ing, is a small scale ver­sion of a CLIC de­cel­er­a­tor. To per­form as ex­pect­ed the beam line must show ef­fi­cient and sta­ble RF power pro­duc­tion over 16 con­sec­u­tive de­cel­er­at­ing struc­tures. As the high in­ten­si­ty elec­tron beam is de­cel­er­at­ed its en­er­gy spread grows by up to 60%. A novel seg­ment­ed beam dump for time re­solved en­er­gy mea­sure­ments has been de­signed to match the re­quire­ments of the TBL. As a com­ple­ment, a dif­fu­sive OTR screen is also in­stalled in the same spec­trom­e­ter line. The com­bi­na­tion of these two de­vices will pro­vide both a high spa­tial res­o­lu­tion mea­sure­ment of both the en­er­gy and en­er­gy spread and a mea­sure­ment with a few nanosec­onds time re­sponse. This paper de­scribes the de­sign of the new seg­ment­ed dump and pre­sents the re­sults from the first com­mis­sion­ing of the TBL spec­trom­e­ter line.

• A. Bertarelli, A. Dallocchio, L. Gentini, N. Mariani, R. Perret, M.A. Timmins
  CERN, Geneva

Phase II col­li­ma­tors will com­ple­ment the ex­ist­ing sys­tem to im­prove the ex­pect­ed high RF impedance and lim­it­ed ef­fi­cien­cy of Phase I jaws. An in­ter­na­tion­al col­lab­o­ra­tive ef­fort has been launched to iden­ti­fy novel ad­vanced ma­te­ri­als re­spond­ing to the very chal­leng­ing re­quire­ments of the new col­li­ma­tors. Com­plex nu­mer­i­cal cal­cu­la­tions sim­u­lat­ing ex­treme con­di­tions and ex­per­i­men­tal tests are in progress. In par­al­lel, an in­no­va­tive mod­u­lar de­sign con­cept of the jaw as­sem­bly is being de­vel­oped to allow fit­ting in al­ter­na­tive ma­te­ri­als, min­i­miz­ing the ther­mal­ly in­duced de­for­ma­tions, with­stand­ing ac­ci­dents and tol­er­ate high ra­di­a­tion doses. Phase II jaw as­sem­bly is made up of a molyb­de­num back-stiff­en­er en­sur­ing high ge­o­met­ri­cal sta­bil­i­ty and a mod­u­lar jaw split in threes sec­tors. Each sec­tor is equipped with a high-ef­fi­cien­cy in­de­pen­dent cool­ing cir­cuit. Beam po­si­tion mon­i­tors (BPM) are em­bed­ded in the jaws to ac­cel­er­ate setup time and im­prove beam mon­i­tor­ing. An ad­just­ment sys­tem will per­mit to fine-tune the jaw flat­ness just be­fore com­mis­sion­ing the sys­tem. A full scale col­li­ma­tor pro­to­type is being man­u­fac­tured by CERN work­shops to val­i­date each fea­ture of the new de­sign.

• D. Wollmann, O. Aberle, G. Arnau-Izquierdo, R.W. Assmann, J.-P. Bacher, V. Baglin, G. Bellodi, A. Bertarelli, A.P. Bouzoud, C. Bracco, R. Bruce, M. Brugger, S. Calatroni, F. Caspers, F. Cerutti, R. Chamizo, A. Cherif, E. Chiaveri, P. Chiggiato, A. Dallocchio, R. De Morais Amaral, B. Dehning, M. Donze, A. Ferrari, R. Folch, P. Francon, P. Gander, J.-M. Geisser, A. Grudiev, E.B. Holzer, D. Jacquet, J.B. Jeanneret, J.M. Jimenez, M. Jonker, J.M. Jowett, Y. Kadi, K. Kershaw, L. Lari, J. Lendaro, F. Loprete, R. Losito, M. Magistris, M. Malabaila, A. Marsili, A. Masi, S.J. Mathot, M. Mayer, C.C. Mitifiot, N. Mounet, E. Métral, A. Nordt, R. Perret, S. Perrollaz, C. Rathjen, S. Redaelli, G. Robert-Demolaize, S. Roesler, A. Rossi, B. Salvant, M. Santana-Leitner, I. Sexton, P. Sievers, T. Tardy, M.A. Timmins, E. Tsoulou, E. Veyrunes, H. Vincke, V. Vlachoudis, V. Vuillemin, Th. Weiler, F. Zimmermann
  CERN, Geneva
• I. Baishev, I.A. Kurochkin
  IHEP Protvino, Protvino, Moscow Region
• D. Kaltchev
  TRIUMF, Vancouver

The LHC has two ded­i­cat­ed clean­ing in­ser­tions: IR3 for mo­men­tum clean­ing and IR7 for be­ta­tron clean­ing. The col­li­ma­tion sys­tem has been spec­i­fied and built with tight me­chan­i­cal tol­er­ances (e.g. jaw flat­ness ~ 40 μm) and is de­signed to achieve a high ac­cu­ra­cy and re­pro­ducibil­i­ty of the jaw po­si­tions. The prac­ti­cal­ly achiev­able clean­ing ef­fi­cien­cy of the pre­sent Phase-I sys­tem de­pends on the pre­ci­sion of the jaw cen­ter­ing around the beam, the ac­cu­ra­cy of the gap size and the jaw par­al­lelism against the beam. The re­pro­ducibil­i­ty and sta­bil­i­ty of the sys­tem is im­por­tant to avoid the fre­quent rep­e­ti­tion of beam based align­ment which is cur­rent­ly a lengthy pro­ce­dure. With­in this paper we de­scribe the method used for the beam based align­ment of the LHC col­li­ma­tion sys­tem, its achieved ac­cu­ra­cy and sta­bil­i­ty and its per­for­mance at 450GeV.

Slides