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Linear Colliders

Linear Colliders. R. Brinkmann, DESY EPS-HEP Conference, Aachen, July 17, 2003. The energy and luminosity challenges for a future e+e- linear collider:.

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Linear Colliders

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  1. Linear Colliders R. Brinkmann, DESY EPS-HEP Conference, Aachen, July 17, 2003 R. Brinkmann, DESY

  2. The energy and luminosity challenges for a future e+e- linear collider: “It’s only an order of magnitude in energy (0.5  1 TeV) and three to four orders of magnitude in luminosity (>1034 cm-2 s-1) from the SLC…” R. Brinkmann, DESY

  3. 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. R. Brinkmann, DESY

  4. FFTB beamline at the end of the SLAC linac. FFTB Collaboration BINP (Novosibirsk/Protvino) DESY Fermilab IBM Kawasaki KEK LAL (Orsay) MPI(Munich) Rochester SLAC 1997 1994 Vertical beam size of 60-70 nm … demagnification needed for any LC. R. Brinkmann, DESY

  5. Linear Collider Parameter Overview R. Brinkmann, DESY

  6. International Linear Collider Technical Review Committee 2nd 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) R. Brinkmann, DESY

  7. 500( 800)GeV e+e- Linear Collider Based on superconducting linac technology R. Brinkmann, DESY

  8. 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 R. Brinkmann, DESY

  9. Accelerating gradient on test stand reached 25 MV/m on average for 1999/2000 cavity production R. Brinkmann, DESY

  10. Test of complete accelerator modules in the TTF linac at DESY (>13,000h beam operation 1997 - 2003) R. Brinkmann, DESY

  11. Higher performance cavities: energy reach  800 GeV 1st step: no add. investment, 2nd step: add cryo+RF power R. Brinkmann, DESY

  12. Improvement of Nb surface quality with electro-polishing (pioneering work done at KEK) BCP EP • Several single cell cavities at g > 40 MV/m • 4 nine-cell cavities at ~35 MV/m R. Brinkmann, DESY

  13. CHECHIA test in pulsed mode TESLA 500 – 800 design R. Brinkmann, DESY

  14. X-band technology(SLAC/KEK & coll. Inst.) NLC SLC-like 20MV/m, 3 GHz  50MV/m (65 unloaded), 11.4GHz R. Brinkmann, DESY

  15. 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 R. Brinkmann, DESY

  16. Structure damage from RF breakdown R. Brinkmann, DESY

  17. Snowmass 2001 R. Brinkmann, DESY

  18. Test Structure Run History (T-Series 2003, not final version for linac) 1 Trip per 25 Hrs Unloaded Gradient (MV/m) NLC/JLC Goal: Less than 1 trip per 10 Hrs at 65 MV/m 400 ns Pulse Width No Observed Change in Microwave Properties Time with RF On (hr) R. Brinkmann, DESY

  19. CLIC two-beam accelerator approachCERN & coll. Inst. R. Brinkmann, DESY

  20. R. Brinkmann, DESY

  21. Successful demonstration of 30 GHz two-beam concept at CTF-II But: serious structure damage from RF breakdown at high gradient R. Brinkmann, DESY

  22. Systematic study of high-g RF breakdown/damage problem: RF breakdown vs. frequency damage vs. different material of irises (Cu, W, Mo) R. Brinkmann, DESY

  23. R. Brinkmann, DESY

  24. LOW CURRENT BUNCH TRAIN COMBINATION streak camera images of beam in the ring 1st turn - 1st bunch train from linac time 2nd turn • First demonstration in June 2002 • Tested combination factors 4 & 5 3rd turn Final intensity profile 4th turn combination factor 4 CTF3 (under construction) R. Brinkmann, DESY

  25. Luminosity challenge:beam quality & stability • Damping rings: emittances required ~factor 3…5 below best values obtained to date at SR sources and ATF-DR (KEK) • Wakefields  fRF3 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 R. Brinkmann, DESY

  26. R. Brinkmann, DESY

  27. Luminosity stability: “Start-to-end” simulations, including ground motion 50 s 2 s R. Brinkmann, DESY

  28. Power spectral density Ground motion: varies form “quiet” (model A) to “noisy” (model C), depending on site R. Brinkmann, DESY

  29. Seismic measurements: TESLA LC central site (Ellerhoop) more quiet than HERA (data taken on a Monday, 0.00h – 1.00h) HERA tunnel Ellerhoop (barn) R. Brinkmann, DESY

  30. 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) R. Brinkmann, DESY

  31. Choice of technology: hybrid collider?? superconducting Normal conducting Doesn’t work…. R. Brinkmann, DESY

  32. 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 R. Brinkmann, DESY

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