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

1
Luminosity Prospects of LHeC,a Lepton Proton
Collider in the LHC Tunnel DESY 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 spacing tb 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 / eNp3.21020m-1
5
Lepton Beam Current

• Assumptions Limited by RF Power
  only
• depends on Bending radius
• r 80 (CLHC-8Lstraigth) / 2p
  2886 m
• eUloss CgEe4 / (er)
  734 MeV

CERN Power Consumption
If 50 MW beam power considered as a limit ? Ie
68mA Ne1.3 1010
6
Design Task e-Ring and IR Design which
provides

• sufficient dynamic aperture
• With matched beams,
• Small crossing angle q ltsxe/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
exe 26 nm
Dffodo 72 degree
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 ebq2ss2
qc/2
IP
Transverse RF resonators
90 degree
p
e
Crabbed Trajectories
qc0.5mr
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