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## The new CLIC parameters

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**The new CLIC parameters**29.10.2007 Alexej Grudiev**Linear Collider major parameters**wall-plug to beam efficiency energy loss by beamstrahlung wall-plug power • Energy reach High accelerating gradient center-of-mass energy Vertical emittance • Luminosity: • High Beam Power (several MWatts) • Wall-plug to beam transfer efficiencyas high as possible (several %) • Generation & preservation of beamemittancesat I.P. as small as possible (few nmrad) • Beam focusing to very small dimentions at IP (few nm) • Beamstrahlung energy spreadincreasing with c.m. colliding energies**326 klystrons**33 MW, 139 ms 326 klystrons 33 MW, 139 ms combiner rings Circumferences delay loop 80.3 m CR1 160.6 m CR2 481.8 m drive beam accelerator 2.37 GeV, 1.0 GHz drive beam accelerator 2.37 GeV, 1.0 GHz CR1 CR1 1 km 1 km delay loop delay loop CR2 CR2 decelerator, 24 sectors of 868 m BDS 2.75 km BDS 2.75 km BC2 BC2 245m 245m IP1 e- main linac , 12 GHz, 100 MV/m, 21 km e+ main linac TA R=120m TA R=120m 48 km booster linac, 9 GeV, 2 GHz BC1 e- injector 2.4 GeV e+ injector, 2.4 GeV e+ DR 365m e- DR 365m CLIC overall layout Drive Beam Generation Complex CLIC overall layout 3 TeV Main Beam Generation Complex**Old and new CLIC main parameters**http://clic-meeting.web.cern.ch/clic-meeting/clictable2007.html**CLIC main linac optimization model**<Ea>, f, ∆φ, <a>, da, d1, d2 BD Bunch population Cell parameters N Q, R/Q, vg, Es/Ea, Hs/Ea Q1, A1, f1 Structure parameters Bunch separation BD Ns Ls, Nb η, Pin, Esmax, ∆Tmax rf constraints Cost function minimization YES NO**Optimization constraints**• Beam dynamics (BD) constraints based on the simulation of the main linac, BDS and beam-beam collision at the IP: • N – bunch population depends on <a>/λ, Δa/<a>, f and <Ea> because of short-range wakes • Ns – bunch separation depends on the long-range dipole wake and is determined by the condition: • Wt,2 · N / <Ea> = 10 V/pC/mm/m · 4x109 / 150 MV/m • RF breakdown and pulsed surface heating (rf) constraints: • ΔTmax(Hsurfmax, tp) < 56 K • Esurfmax < 250 MV/m • Pin/Cin•tp1/3 < 18 MW·ns1/3/mm @ X-band (frequency dependent)**Frequency scaling of power constraint**Experimental data at X-band and 30 GHz become available 2006 Scaled structures Scaled structures show the same gradient at X-band and at 30 GHz: Eatp1/6 = const Pin/Cin•tp1/3•f = const**Optimization Cost functions**1. Luminosity per linac input power (performance): Figure of Merit (FoM) Collision energy is constant 2. Total cost parametric model (become available 2006) Investment cost + Exploitation cost for 10 years Ct = Ci + Ce**Optimization parameter space**N structures: 7 14 2 24 60 61 4 -------------- 68.866.560 All structure parameters are variable: <Eacc> = 90 – 150 MV/m, f = 10 – 30 GHz, Δφ= 120o, 150o, <a>/λ= 0.09 - 0.21, Δa/<a> = 0.01 – 0.6, d1/λ= 0.025 - 0.1, d2 > d1 Ls = 100 – 1000 mm.**CLIC performance and cost versus gradient**Ecms = 3 TeV L(1%) = 2.0 1034 cm-2s-1 Performance Cost Previous Previous New New Optimum • Performance increases with lower accelerating gradient (mainly due to higher efficiency) • Flat cost variation in 100 to 130 MV/m with a minimum around 120 MV/m**CLIC performance and cost versus frequency**Ecms = 3 TeV L(1%) = 2.0 1034 cm-2s-1 Performance Cost New Optimum Previous Previous New Optimum • Maximum Performance around 14 GHz • Flat cost variation in 12 to 16 GHz frequency range with a minimum around 14 GHz**CLIC Performance and Cost optimization**Performance (a.u.) CLIC Old Parameters Accelerating field = 150 MV/m RF frequency = 30 GHz CLIC New parameters Accelerating field = 100 MV/m RF frequency = 12 GHz Total cost (a.u.)**FoM = L1/N · η**RF BD Interplay between BD and RF L1/N BD optimum aperture: <a> = 2.6 mm Why X-band ? Crossing gives optimum frequency RF optimum aperture: <a>/λ = 0.1 ÷ 0.12**CLIC main linac optimization model taking into account**complex interplay between beam dynamics and rf performance has been developed over the past few years In 2006, new experimental data both at 30 GHz and at X-band have been obtained CLIC total cost parametric model has become available Optimization of CLIC frequency and gradient has been done which (together with some other considerations) resulted in major change of CLIC parameters from 150MV/m at 30GHz to 100MV/m at 12GHz Summary