320 likes | 448 Views
Linear Colliders. R. Brinkmann, DESY EPS-HEP Conference, Aachen, July 17, 2003. The energy and luminosity challenges for a future e+e- linear collider:.
E N D
Linear Colliders R. Brinkmann, DESY EPS-HEP Conference, Aachen, July 17, 2003 R. Brinkmann, DESY
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
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
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
Linear Collider Parameter Overview R. Brinkmann, DESY
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
500( 800)GeV e+e- Linear Collider Based on superconducting linac technology R. Brinkmann, DESY
Why superconducting? • High efficiency ACbeam (>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
Accelerating gradient on test stand reached 25 MV/m on average for 1999/2000 cavity production R. Brinkmann, DESY
Test of complete accelerator modules in the TTF linac at DESY (>13,000h beam operation 1997 - 2003) R. Brinkmann, DESY
Higher performance cavities: energy reach 800 GeV 1st step: no add. investment, 2nd step: add cryo+RF power R. Brinkmann, DESY
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
CHECHIA test in pulsed mode TESLA 500 – 800 design R. Brinkmann, DESY
X-band technology(SLAC/KEK & coll. Inst.) NLC SLC-like 20MV/m, 3 GHz 50MV/m (65 unloaded), 11.4GHz R. 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 R. Brinkmann, DESY
Structure damage from RF breakdown R. Brinkmann, DESY
Snowmass 2001 R. Brinkmann, DESY
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
CLIC two-beam accelerator approachCERN & coll. Inst. R. Brinkmann, DESY
Successful demonstration of 30 GHz two-beam concept at CTF-II But: serious structure damage from RF breakdown at high gradient R. Brinkmann, DESY
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
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
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
Luminosity stability: “Start-to-end” simulations, including ground motion 50 s 2 s R. Brinkmann, DESY
Power spectral density Ground motion: varies form “quiet” (model A) to “noisy” (model C), depending on site R. 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) R. 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) R. Brinkmann, DESY
Choice of technology: hybrid collider?? superconducting Normal conducting Doesn’t work…. R. 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 R. Brinkmann, DESY