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LH e C Design Goals

Luminosity Prospects of LH e C, a Lepton Proton Collider in the LHC Tunnel DESY Colloquium May 23 2006 F. Willeke, DESY. LH e C Design Goals. Luminosity L = 1 ∙ 10 33 cm -2 s -1 Energy E cm = 1.4 TeV. Design Asumptions. based on LHC Proton beam parameters

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LH e C Design Goals

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  1. Luminosity Prospects of LHeC,a Lepton Proton Collider in the LHC TunnelDESY Colloquium May 23 2006F. Willeke, DESY

  2. LHeC Design Goals Luminosity L = 1 ∙1033 cm-2s-1 Energy Ecm = 1.4 TeV

  3. Design Asumptions based on LHC Proton beam parameters Energy Ep = 7 TeV Particles per Bunch Np = 1.68 1011 Emittance eNp = 3.76 radmm Bunch spacingtb = 75 ns (instead of 25ns) Bunch Length sp = 7.6 cm Ee = 70 GeV

  4. Luminosity Matched beam cross sections at IP sxp = sxe, syp = sye Lepton Beam-beam tune shift avoided With the proton beam brightness given by LHC, Npgp / eNp=3.2·1020m-1

  5. Lepton Beam Current Assumptions: Limited by RF Power only depends on Bending radius r = 80% ∙ (CLHC-8∙Lstraigth) / 2p = 2886 m eUloss= CgEe4 / (er) = 734 MeV CERN Power Consumption If 50 MW beam power considered as a limit  Ie = 68mA Ne=1.3 1010

  6. Design Task: e-Ring and IR Design which provides • sufficient dynamic aperture • With matched beams, • Small crossing angle q <sxe/sp • Small hour glass effect bye≥ sp • tolerable synchrotron radiation background • feasible components

  7. Dynamic Aperture Scaling Taken from HERA: 0.2 This assumes a Plain FODO structure for FODO cell structure, N number of FODO Cells Arc chromaticity IR chromaticity for matched beams

  8. Choosing Lepton Ring Lattice Parameters

  9. e Lattice 8 Octants with 500m Straight section 400 FODO cells, Cell length 54 m Dipole length 2 x 11.33 m B= 780 Gauss Quadrupole length 1.5 m (G = 7 T/m) 11.33m bend bend bend bend 54m Dffodo = 72 degree exe = 26 nm

  10. Synchrotron Radiation

  11. Bypass around Atlas and CMS

  12. Which IR?

  13. IR Parameters • sxp = sxe, syp = sye • exp = 0.5 nm exe = 26 nm Need to match “flat” e beam with “round” p beam bxp/byp = 4  bxp = 2 m byp = 50 cm bxe = 5 cm bye = 5 cm

  14. IR Layout Vertically focussing Quadrupole magnet for p e-low-beta triplets Other P beam

  15. IR Layout

  16. Luminosity

  17. Beam-Beam Effect Central crossing beam-beam parameters well within the HERA range

  18. Parasitic Crossings 1st parasitic crossing for different bunch spacing 75ns 50ns 25ns Dx = 8 s separation, ok Dx = 3.5 s separation, not ok Dx = 1 s separation, not ok Nominal Bunch spacing LHC not compatible with maximum LHeC luminosity !

  19. Crab Crossing Crossing angle will enhance effective beam size s2 = eb+q2ss2 qc/2 IP 90 degree Transverse RF resonators p e “Crabbed Trajectories qc=0.5mr

  20. Quadrupole Magnets

  21. Conclusions A first look at a possible lepton proton collider in the LHC tunnel with a luminosity of 1033cm-2s-1 appears to be technical possible Simultaneous operation of pp and ep should be possible (however with reduced pp luminosity) More work is needed to determine the most optimum parameters, the optimum technical choices and the cost of such a facility A workshop to discuss this exciting option together with experimental physicists and accelerator scientists is planned in October 06

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