• M.H. Lieng
  UNIDO, Dortmund
• R. Appleby, G. Corti
  CERN, Geneva
• V. Talanov
  IHEP Protvino, Protvino, Moscow Region

We con­sid­er the for­ma­tion of ma­chine back­ground in­duced by pro­ton loss­es in the long straight sec­tion of the LHCb ex­per­i­ment at LHC. Both sources show­er­ing from the ter­tiary col­li­ma­tors lo­cat­ed in the LHCb in­ser­tion re­gion as well as local beam-gas in­ter­ac­tion are taken into ac­count. We pre­sent the pro­ce­dure for, and re­sults of, nu­mer­i­cal stud­ies of such back­ground for var­i­ous con­di­tions. The ex­pect­ed im­pact on the ex­per­i­ment and sig­nal char­ac­ter­is­tics are also dis­cussed.

• Y.I. Levinsen, R. Appleby, H. Burkhardt
  CERN, Geneva

We re­port on first ob­ser­va­tions and de­tailed sim­u­la­tions of beam gas rates in the LHC. For the sim­u­la­tions, a com­pre­hen­sive tool has been set up to sim­u­late in a few hours the ex­pect­ed beam gas loss­es when pres­sure maps, col­li­ma­tor set­tings, and/or beam op­tics changes. The sim­u­la­tion in­cludes both elas­tic and in­elas­tic scat­ter­ing, with sub­se­quent mul­ti­turn track­ing of pro­ton residues. This pro­vides amongst oth­ers a more re­al­is­tic col­li­ma­tor loss dis­tri­bu­tions from elas­tic in­ter­ac­tions than what was pre­vi­ous­ly avail­able.

• Y.I. Levinsen, R. Appleby, H. Burkhardt, S.M. White
  CERN, Geneva

Back­ground and loss rates vary when beams are brought into col­li­sions in the LHC and when the beam sep­a­ra­tion is var­ied dur­ing lu­mi­nos­i­ty scans. We re­port on the first ob­ser­va­tions in the early LHC op­er­a­tion. The ob­served ef­fects are an­a­lyzed and com­pared with mod­els and sim­u­la­tion.

• B.J. Holzer, S. Bettoni, O.S. Brüning, S. Russenschuck
  CERN, Geneva
• R. Appleby
  UMAN, Manchester
• J.B. Dainton, L.N.S. Thompson
  Cockcroft Institute, Warrington, Cheshire
• M. Klein
  The University of Liverpool, Liverpool
• A. Kling, B. Nagorny, U. Schneekloth
  DESY, Hamburg
• P. Kostka
  DESY Zeuthen, Zeuthen
• A. Polini
  INFN-Bologna, Bologna

The LHeC aims at col­lid­ing hadron-lep­ton beams with cen­ter of mass en­er­gies in the TeV scale. For this pur­pose the ex­ist­ing LHC stor­age ring is ex­tend­ed by a high en­er­gy elec­tron ac­cel­er­a­tor in the en­er­gy range of 60 to 140 GeV. The elec­tron beam will be ac­cel­er­at­ed and stored in a LEP like stor­age ring in the LHC tun­nel. In this paper we pre­sent the lay­out of the in­ter­ac­tion re­gion which has to de­liv­er at the same time well matched beam op­tics and an ef­fi­cient sep­a­ra­tion of the elec­tron and pro­ton beams. In gen­er­al the large mo­men­tum dif­fer­ence of the two col­lid­ing beams pro­vides a very el­e­gant way to solve this prob­lem: A fo­cus­ing scheme that leads to the re­quired beam sizes of the elec­trons and pro­tons is com­bined with an early but gen­tle beam sep­a­ra­tion to avoid par­a­sitic beam en­coun­ters and still keep the syn­chrotron ra­di­a­tion level in the IR with­in rea­son­able lim­its. We pre­sent in this paper two ver­sions of this con­cept: A high lu­mi­nos­i­ty lay­out where the mini beta mag­nets are em­bed­ded into the de­tec­tor de­sign as well as an IR de­sign that is op­ti­mised for max­i­mum ac­cep­tance of the par­ti­cle de­tec­tor.

• F. Zimmermann, S. Bettoni, O.S. Brüning, B.J. Holzer, S. Russenschuck, D. Schulte, R. Tomás
  CERN, Geneva
• H. Aksakal
  N.U, Nigde
• R. Appleby
  UMAN, Manchester
• S. Chattopadhyay, M. Korostelev
  Cockcroft Institute, Warrington, Cheshire
• A.K. Çiftçi, R. Çiftçi, K. Zengin
  Ankara University, Faculty of Sciences, Tandogan/Ankara
• J.B. Dainton, M. Klein
  The University of Liverpool, Liverpool
• E. Eroglu, I. Tapan
  UU, Bursa
• P. Kostka
  DESY Zeuthen, Zeuthen
• V. Litvinenko
  BNL, Upton, Long Island, New York
• E. Paoloni
  University of Pisa and INFN, Pisa
• A. Polini
  INFN-Bologna, Bologna
• U. Schneekloth
  DESY, Hamburg
• M.K. Sullivan
  SLAC, Menlo Park, California

In a linac-ring elec­tron-pro­ton col­lid­er based on the LHC ("LR-LHeC"), the final fo­cus­ing quadrupoles for the elec­tron beam can be in­stalled far from the col­li­sion point, as far away as the pro­ton final triplet (e.g. 23 m) if not fur­ther, thanks to the small elec­tron-beam emit­tance. The inner free space could ei­ther be fully do­nat­ed to the par­ti­cle-physics de­tec­tor, or ac­com­mo­date "slim" dipole mag­nets pro­vid­ing head-on col­li­sions of elec­tron and pro­ton bunch­es. We pre­sent ex­am­ple lay­outs for ei­ther sce­nario con­sid­er­ing elec­tron beam en­er­gies of 60 and 140 GeV, and we dis­cuss the op­tics for both pro­ton and elec­tron beams, the im­plied min­i­mum beam-pipe di­men­sions, pos­si­ble de­sign pa­ram­e­ters of the in­ner­most pro­ton and elec­tron mag­nets, the cor­re­spond­ing de­tec­tor ac­cep­tance, the syn­chrotron ra­di­a­tion power and its pos­si­ble shield­ing or de­flec­tion, con­straints from long-range beam-beam in­ter­ac­tions as well as from the LHC pro­ton-pro­ton col­li­sion points and from the rest of the LHC ring, the pas­sage of the sec­ond pro­ton beam, and the min­i­mum beta* for the col­lid­ing pro­tons.

• R.J. Barlow, R. Appleby, J. Molson, H.L. Owen, A.M. Toader
  UMAN, Manchester

The col­li­ma­tion sys­tem of the LHC will be crit­i­cal to its suc­cess, as the halo of high en­er­gy (7 TeV) par­ti­cles must be re­moved in such a way that they do not de­posit en­er­gy in the su­per­con­duct­ing mag­nets which would quench them, or show­ers in the ex­per­i­ments. We study the prop­er­ties of the LHC col­li­ma­tion sys­tem as pre­dict­ed by the Mer­lin and Six­track/K2 sim­u­la­tion pack­ages, and com­pare their pre­dic­tions for ef­fi­cien­cy and halo pro­duc­tion, and the pat­tern of beam loss­es. The so­phis­ti­cat­ed sys­tem in­cludes many col­li­ma­tors, serv­ing dif­fer­ent pur­pos­es. Both pro­grams in­clude en­er­gy loss and mul­ti­ple Coulomb scat­ter­ing as well as loss­es through nu­cle­ar scat­ter­ing. The MER­LIN code also in­cludes the ef­fects of wake­fields. We com­pare the re­sults and draw con­clu­sions on the per­for­mance that can be achieved.

• E. Gschwendtner, A. Apyan, K. Elsener, A. Sailer, J.A. Uythoven
  CERN, Geneva
• R. Appleby, M.D. Salt
  UMAN, Manchester
• A. Ferrari, V.G. Ziemann
  Uppsala University, Uppsala

The 1.5TeV CLIC beams, with a total power of 14MW per beam, are dis­rupt­ed at the in­ter­ac­tion point due to the very strong beam-beam ef­fect. As a re­sult, some 3.5MW reach the main dump in form of beam­strahlung pho­tons. About 0.5MW of e⁺e^- pairs with a very broad en­er­gy spec­trum need to be dis­posed along the post-col­li­sion line. The con­cep­tu­al de­sign of this beam line will be pre­sent­ed. Em­pha­sis will be on the op­ti­miza­tion stud­ies of the CLIC post-col­li­sion line de­sign with re­spect to the en­er­gy de­po­si­tion in win­dows, dumps and scrap­ers, on the de­sign of the lu­mi­nos­i­ty mon­i­tor­ing for a fast feed­back to the beam steer­ing and on the back­ground con­di­tions for the lu­mi­nos­i­ty mon­i­tor­ing equip­ment.

• E. Gschwendtner, K. Elsener
  CERN, Geneva
• R. Appleby, M.D. Salt
  UMAN, Manchester
• A. Apyan
  Fermilab, Batavia
• A. Ferrari
  Uppsala University, Uppsala

The 1.5TeV CLIC beams, with a total power of 14MW per beam, are dis­rupt­ed at the in­ter­ac­tion point due to the very strong beam- beam ef­fect. The re­sult­ing spent beam prod­ucts are trans­port­ed to suit­able dumps by the post-IP beam line, which gen­er­ates beam loss­es and caus­es the pro­duc­tion of sec­ondary cas­cades to­wards the in­ter­ac­tion re­gion. In this paper the elec­tro­mag­net­ic back­ground at the IP are pre­sent­ed, which were cal­cu­lat­ed using bi­ased Monte Carlo tech­niques. Also, a first es­ti­mate is made of neu­tron back-shine from the main beam dump.