Introduction to particle accelerators

Transcription

1 Introduction to particle accelerators Walter Scandale CERN - AT department Lecce, 17 June 2006

2 Introductory remarks Particle accelerators are black boxes producing either flux of particles impinging on a fixed target or debris of interactions emerging from colliding particles In trying to clarify what the black boxes are one can list the technological problems describe the basic physics and mathematics involved Most of the phenomena in a particle accelerator can be described in terms of classical mechanics and electro-dynamics, using a little bit of restricted relativity However there will be complications: in an accelerator there are many non-linear phenomena (stability of motion, chaotic single-particle trajectories) there are many particles interacting to each other and with a complex surroundings the available instrumentation will only provide observables averaged over large ensembles of particles In two hours we can only fly over the problems just to have an overview of them W.Scandale, Introduction to Particle Accelerators 12 June

3 Inventory of synchrotron components W.Scandale, Introduction to Particle Accelerators 12 June

4 Bending magnet Efficient use of the current -> small gap height Field quality -> determined by the pole shape Field saturation -> 2 Tesla B Earth = Tesla B > 2 Tesla -> use superconducting magnets B LHC = 8.4 Tesla W.Scandale, Introduction to Particle Accelerators 12 June

5 Quadrupole magnet Vertical focusing Horizontal defocusing g=gradient [T/m] W.Scandale, Introduction to Particle Accelerators 12 June

6 Alternate gradient focusing QF QD QF QD QF W.Scandale, Introduction to Particle Accelerators 12 June

7 Mechanical analogy for alternate gradient W.Scandale, Introduction to Particle Accelerators 12 June

8 Basic 2-D equation of motion in a dipolar field W.Scandale, Introduction to Particle Accelerators 12 June

9 Basic 2D equation of motion W.Scandale, Introduction to Particle Accelerators 12 June

10 Basic 2D equation of motion FODO structure Periodic envelop Cos-like trajectory Sin-like trajectory Multi-turn trajectory W.Scandale, Introduction to Particle Accelerators 12 June

11 Longitudinal stability Momentum compaction W.Scandale, Introduction to Particle Accelerators 12 June

12 Chromaticity and sextupole magnet Dispersion orbit W.Scandale, Introduction to Particle Accelerators 12 June

13 Chromaticity correction and non-linear resonance W.Scandale, Introduction to Particle Accelerators 12 June

14 Emittance W.Scandale, Introduction to Particle Accelerators 12 June

15 Synchrotron radiation W.Scandale, Introduction to Particle Accelerators 12 June

16 Synchrotron radiation and beam size Adiabatic damping Synchrotron light emission W.Scandale, Introduction to Particle Accelerators 12 June

17 Effect of synchrotron light W.Scandale, Introduction to Particle Accelerators 12 June

18 Collective effects W.Scandale, Introduction to Particle Accelerators 12 June

19 Instabilities and feedback W.Scandale, Introduction to Particle Accelerators 12 June

20 W.Scandale, Introduction to Particle Accelerators 12 June

21 Space charge W.Scandale, Introduction to Particle Accelerators 12 June

22 Beam size W.Scandale, Introduction to Particle Accelerators 12 June

23 Fixed target versus collider rings Fixed target Collider Advantage Bruno Touschek W.Scandale, Introduction to Particle Accelerators 12 June

24 Lepton versus hadron colliders -> (At the parton level ) -> W.Scandale, Introduction to Particle Accelerators 12 June

25 Lecture II W.Scandale, Introduction to Particle Accelerators 12 June

26 LHC lay-out C = m Arc = m DS = 2 x 170 m INS = 2 x 269 m Free space for detectors: ± 23 m W.Scandale, Introduction to Particle Accelerators 12 June

27 LHC features Technological challenge (+1) W.Scandale, Introduction to Particle Accelerators 12 June

28 ε = m Bunch spacing 25 ns m W.Scandale, Introduction to Particle Accelerators 12 June

29 Maximum B-field W.Scandale, Introduction to Particle Accelerators 12 June

30 Cos(θ) coil W.Scandale, Introduction to Particle Accelerators 12 June

31 Superconducting dipole W.Scandale, Introduction to Particle Accelerators 12 June

32 Collider luminosity High L needs: W.Scandale, Introduction to Particle Accelerators 12 June

33 Beam-beam interaction W.Scandale, Introduction to Particle Accelerators 12 June

34 Head-on collisions W.Scandale, Introduction to Particle Accelerators 12 June

35 W.Scandale, Introduction to Particle Accelerators 12 June

36 W.Scandale, Introduction to Particle Accelerators 12 June

37 LHC luminosity Performances limitations Luminosity: protons in a bunch no. of bunches revolution frequency L = event rate cross section = 1 N1 N2 k f S beam cross section 2 for equal, round, bi-gaussian beams: N1 N2 = N S --> 4š σ 2 2 σ ε* = γ β* invariant emittance L = 2 N k f γ 4π ε β L = γ N N 4πβ * ε * ²t Transverse beam density: head-on beam-beam space-charge in the injectors transfers dilution Beam current: long range beam-beam collective instability synchrotron radiation stored beam energy Head-on beam-beam: detuning ξ = ξ nb. of interactions Š π ε ε W.Scandale, Introduction to Particle Accelerators 12 June rp N

38 LHC insertions 56 m W.Scandale, Introduction to Particle Accelerators 12 June

39 W.Scandale, Introduction to Particle Accelerators 12 June

40 W.Scandale, Introduction to Particle Accelerators 12 June

41 W.Scandale, Introduction to Particle Accelerators 12 June

42 High luminosity experiments W.Scandale, Introduction to Particle Accelerators 12 June

43 Ion-ion experiment W.Scandale, Introduction to Particle Accelerators 12 June

44 W.Scandale, Introduction to Particle Accelerators 12 June

45 W.Scandale, Introduction to Particle Accelerators 12 June

46 W.Scandale, Introduction to Particle Accelerators 12 June

47 W.Scandale, Introduction to Particle Accelerators 12 June

48 W.Scandale, Introduction to Particle Accelerators 12 June

49 W.Scandale, Introduction to Particle Accelerators 12 June