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

2. LHeC Design Goals Luminosity L = 1 ∙10 33 cm -2 s -1 Energy E cm = 1.4 TeV

3. Design Asumptions based on LHC Proton beam parameters Energy E p = 7 TeV Particles per Bunch N p = 1.68 1011 Emittance  Np = 3.76 rad  m Bunch spacing  b = 75 ns (instead of 25ns) Bunch Length  p = 7.6 cm E e = 70 GeV

4. Luminosity Matched beam cross sections at IP  xp =  xe,  yp =  ye Lepton Beam-beam tune shift avoided With the proton beam brightness given by LHC, N p  p /  Np =3.2·10 20 m -1

5. Lepton Beam Current Assumptions: Limited by RF Power only depends on Bending radius  = 80% ∙ (C LHC -8∙L straigth ) / 2  = 2886 m eU loss = C g E e 4 / (e  MeV CERN Power Consumption If 50 MW beam power considered as a limit  I e = 68mA N e =1.3 10 10

6. Design Task : e-Ring and IR Design which provides sufficient dynamic aperture With matched beams, Small crossing angle  <  xe /  p Small hour glass effect  ye ≥  p tolerable synchrotron radiation background feasible components

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

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) bend 54m 11.33m   xe = 26 nm  fodo = 72 degree

10. Synchrotron Radiation

11. Bypass around Atlas and CMS

12. Which IR?

13. IR Parameters  xp =  xe,  yp =  ye  xp = 0.5 nm  xe = 26 nm Need to match “flat” e beam with “round” p beam  xp /  yp = 4   xp = 2 m  yp = 50 cm  xe = 5 cm  ye = 5 cm

14. IR Layout e-low-beta triplets Vertically focussing Quadrupole magnet for p 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 75ns 50ns 25ns  x = 8  separation, ok  x = 3.5  separation, not ok  x = 1  separation, not ok 1 st parasitic crossing for different bunch spacing Nominal Bunch spacing LHC not compatible with maximum LHeC luminosity !

19. Crab Crossing pe  c =0.5mr “Crabbed Trajectories IP Transverse RF resonators  c /2 90 degree Crossing angle will enhance effective beam size  2 =  +  2  s 2

20. Quadrupole Magnets

21. Conclusions A first look at a possible lepton proton collider in the LHC tunnel with a luminosity of 10 33 cm -2 s -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