Transcript Slide 1
Luminosity Prospects of LHeC, a Lepton Proton Collider in the LHC Tunnel DESY Colloquium May 23 2006 F. Willeke, DESY LHeC Design Goals Luminosity L = 1 ∙1033 cm-2s-1 Energy Ecm = 1.4 TeV Design Asumptions based on LHC Proton beam parameters Energy Particles per Bunch Emittance Bunch spacing Bunch Length Ep = 7 TeV Np = 1.68 1011 eNp = 3.76 radmm tb = 75 ns (instead of 25ns) sp = 7.6 cm Ee = 70 GeV Luminosity L N p N e f rev nb 2 e xp xp e xe xe e yp yp e ye ye sxp = sxe, syp = sye Matched beam cross sections at IP Lepton Beam-beam tune shift avoided L Ie N p p 2 e e Np xp yp With the proton beam brightness given by LHC, Ie xp yp Npp / eNp=3.2·1020m-1 A 0.063 m Lepton Beam Current Assumptions: Limited by RF Power only depends on Bending radius r = 80% ∙ (CLHC-8∙Lstraigth) / 2 = 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 xp yp 1m • sufficient dynamic aperture •With matched beams, • Small crossing angle • Small hour glass effect q <sxe/sp ye ≥ sp • tolerable synchrotron radiation background • feasible components Dynamic Aperture Scaling Taken from HERA: 0.2 This assumes a for FODO cell structure, N number of FODO Cells Plain FODO structure Arc chromaticity IR chromaticity for matched beams Choosing Lepton Ring Lattice Parameters 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 54m Dffodo = 72 degree exe = 26 nm bend Synchrotron Radiation Value s for IR Instantaneous Power for one electron Total Pow er ) Pg Ee r ir 3 .20 3 1 0 7 watt Ee r ir qir Ie) 1 7.4 1kW 2 Psyn ) Pow er per unit Length Ps Ee r ir Ie 0 .45 5kWm 1 Critical Energy ) uc Ee r ir 1 07 .24 4k eV Bypass around Atlas and CMS Which IR? IR Parameters sxp = sxe, syp = sye exp = 0.5 nm exe = 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 IR Layout Other P beam e-low-beta triplets Vertically focussing Quadrupole magnet for p IR Layout Luminosity 2 1 Lpeak 1.0110 cm sec 33 Beam-Beam Effect Central crossing beam-beam parameters well within the HERA range 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 Crossing angle will enhance effective beam size s2 = e+q2ss2 qc/2 IP 90 degree p “Crabbed Trajectories Transverse e RF resonators qc=0.5mr Quadrupole Magnets 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