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EPS-HEP Aachen 2003R. Brinkmann, DESY Linear Colliders R. Brinkmann, DESY EPS-HEP Conference, Aachen, July 17, 2003 Slide 2 EPS-HEP Aachen 2003R. Brinkmann, DESY The energy and luminosity challenges for a future e+e- linear collider: Its only an order of magnitude in energy (0.5 1 TeV) and three to four orders of magnitude in luminosity (>10 34 cm -2 s -1 ) from the SLC Slide 3 EPS-HEP Aachen 2003R. Brinkmann, DESY Lessons from the SLC New Territory in Accelerator Design and Operation Sophisticated on-line modeling of non-linear beam physics. Correction techniques (trajectory and emittance), from hands-on by operators to fully automated control, slow/fast feedback theory and practice. Slide 4 EPS-HEP Aachen 2003R. Brinkmann, DESY FFTB Collaboration BINP (Novosibirsk/Protvino) DESY Fermilab IBM Kawasaki KEK LAL (Orsay) MPI(Munich) Rochester SLAC FFTB beamline at the end of the SLAC linac. Vertical beam size of 60-70 nm demagnification needed for any LC. 1997 1994 Slide 5 EPS-HEP Aachen 2003R. Brinkmann, DESY Linear Collider Parameter Overview Slide 6 EPS-HEP Aachen 2003R. Brinkmann, DESY International Linear Collider Technical Review Committee 2 nd Report 2003 (480 pages), Chair: G. Loew, SLAC www.slac.stanford.edu/xorg/ilc-trc/2002/2002/report/03rep.htm Asses technical status of 500 GeV LC designs Potential for reaching higher energies Identify R&D work to be done ranking list R1(feasibility demonstration) R4(desirable for technical/cost optimisation) Slide 7 EPS-HEP Aachen 2003R. Brinkmann, DESY 500 ( 800) GeV e+e- Linear Collider Based on superconducting linac technology Slide 8 EPS-HEP Aachen 2003R. Brinkmann, DESY Why superconducting? High efficiency AC beam (>20%, ~10% normal c.) Low frequency: Long pulses with low RF peak power Small beam perturbations from wakefields Intra-train feedback on beam orbit, energy, luminosity First proposed in 1960s (M. Tigner) show stopper was too low acc. Gradient, too high cost Slide 9 EPS-HEP Aachen 2003R. Brinkmann, DESY Accelerating gradient on test stand reached 25 MV/m on average for 1999/2000 cavity production Slide 10 EPS-HEP Aachen 2003R. Brinkmann, DESY Test of complete accelerator modules in the TTF linac at DESY (>13,000h beam operation 1997 - 2003) Slide 11 EPS-HEP Aachen 2003R. Brinkmann, DESY Higher performance cavities: energy reach 800 GeV 1 st step: no add. investment, 2 nd step: add cryo+RF power Slide 12 EPS-HEP Aachen 2003R. Brinkmann, DESY Improvement of Nb surface quality with electro-polishing (pioneering work done at KEK) BCPEP Several single cell cavities at g > 40 MV/m 4 nine-cell cavities at ~35 MV/m Slide 13 EPS-HEP Aachen 2003R. Brinkmann, DESY CHECHIA test in pulsed mode TESLA 500 800 design Slide 14 EPS-HEP Aachen 2003R. Brinkmann, DESY X-band technology (SLAC/KEK & coll. Inst.) SLC-like 20MV/m, 3 GHz 50MV/m (65 unloaded), 11.4GHz NLC Slide 15 EPS-HEP Aachen 2003R. Brinkmann, DESY The NLCTA with 1.8 m accelerator structures (ca 1997). Demonstration of X- band concept, wakefield control, beamloading compensation, But: acc. Gradient limited < 40 MV/m Slide 16 EPS-HEP Aachen 2003R. Brinkmann, DESY Structure damage from RF breakdown Slide 17 EPS-HEP Aachen 2003R. Brinkmann, DESY Snowmass 2001 Slide 18 EPS-HEP Aachen 2003R. Brinkmann, DESY Unloaded Gradient (MV/m) Time with RF On (hr) Test Structure Run History (T-Series 2003, not final version for linac) 400 ns Pulse Width 1 Trip per 25 Hrs NLC/JLC Goal: Less than 1 trip per 10 Hrs at 65 MV/m No Observed Change in Microwave Properties Slide 19 EPS-HEP Aachen 2003R. Brinkmann, DESY CLIC two-beam accelerator approach CERN & coll. Inst. Slide 20 EPS-HEP Aachen 2003R. Brinkmann, DESY Slide 21 EPS-HEP Aachen 2003R. Brinkmann, DESY Successful demonstration of 30 GHz two- beam concept at CTF-II But: serious structure damage from RF breakdown at high gradient Slide 22 EPS-HEP Aachen 2003R. Brinkmann, DESY Systematic study of high-g RF breakdown/damage problem: RF breakdown vs. frequency damage vs. different material of irises (Cu, W, Mo) Slide 23 EPS-HEP Aachen 2003R. Brinkmann, DESY Slide 24 EPS-HEP Aachen 2003R. Brinkmann, DESY Final intensity profile combination factor 4 1 st turn - 1 st bunch train from linac 2 nd turn 3 rd turn 4 th turn streak camera images of beam in the ring time LOW CURRENT BUNCH TRAIN COMBINATION First demonstration in June 2002 Tested combination factors 4 & 5 CTF3 (under construction) Slide 25 EPS-HEP Aachen 2003R. Brinkmann, DESY Luminosity challenge: beam quality & stability Damping rings: emittances required ~factor 35 below best values obtained to date at SR sources and ATF-DR (KEK) Wakefields f RF 3 tighter alignment tolerances & more precise beam diagnostics for higher frequency linacs Dynamic stability: higher rep. Rate of n.c. linacs compensates (partially) for tighter tolerances Slide 26 EPS-HEP Aachen 2003R. Brinkmann, DESY Slide 27 EPS-HEP Aachen 2003R. Brinkmann, DESY Luminosity stability: Start-to-end simulations, including ground motion 50 s2 s Slide 28 EPS-HEP Aachen 2003R. Brinkmann, DESY Ground motion: varies form quiet (model A) to noisy (model C), depending on site Power spectral density Slide 29 EPS-HEP Aachen 2003R. Brinkmann, DESY Seismic measurements: TESLA LC central site (Ellerhoop) more quiet than HERA (data taken on a Monday, 0.00h 1.00h) HERA tunnel Ellerhoop (barn) Slide 30 EPS-HEP Aachen 2003R. Brinkmann, DESY There are a number of subtle effects in LC beam dynamics e.g. the banana effect (amplification of bunch deformations during collision): (TESLA beam-beam simulation) Slide 31 EPS-HEP Aachen 2003R. Brinkmann, DESY Choice of technology: hybrid collider?? superconductingNormal conducting Doesnt work. Slide 32 EPS-HEP Aachen 2003R. Brinkmann, DESY Towards a Global Linear Collider International Linear Collider Steering Committee (Chair: M. Tigner, Cornell) will select the linac technology with the help of a group of Wise persons (~ mid 2004) Establish GLC design group Technical Design Report as basis for site selection and project approval Worldwide organisation at political level Start project construction ~2007