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


Lh e c design goals
LHeC Design Goals

Luminosity L = 1 ∙1033 cm-2s-1

Energy Ecm = 1.4 TeV


Design asumptions
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


Luminosity
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


Lepton beam current
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


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


Dynamic aperture scaling
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



E lattice
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





Ir parameters
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


Ir layout
IR Layout

Vertically focussing Quadrupole magnet for p

e-low-beta

triplets

Other

P beam




Beam beam effect
Beam-Beam Effect

Central crossing beam-beam parameters well within the HERA range


Parasitic crossings
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 !


Crab crossing
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



Conclusions
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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