Accelerators. Lecture V. Oliver Brüning. school/lecture5

Transcription

1 Accelerators Lecture V Oliver Brüning AB/ABP school/lecture5

2 V) LEP, LHC + more LEP LHC Other HEP Projects Future Projects What else?

3 LEP Precision Experiment: LEP: E = 45.6 GeV Z -.3% LEP2: E = 8.5 GeV (m = 9 GeV) Z +/- W -.% (m = 8.5 GeV) W E = GeV? Limits: 2 π R = 27 km P > 2 MW U > 2.8 GeV P > 4 kw ( MW) σ γ

4 Luminosity N b, max : L LEP: LEP2: 2 Np σ x σ n b y TMCI, beam-beam heat loss I = e N f b b rev =.3 -. ma I tot : RF power (P = U I) 8 ma n b= 8-2 bunches / beam σ: σ x σ y synchrotron radiation closed orbit γ quantum excitations coupling vertical dispersion

5 Beam Separation for e - /e+ Lorentz Equation: F = e *E +e* v x B Electrostatic Separation Positive Voltage e - e + Negative Voltage 4 meter Sparking: +/- 5 kvolt

6 Horizontal Orbit: Vertical Orbit: LEP Orbit beam offset in quadrupoles: energy error Lake Geneva moon beam offset in quadrupoles beam separation orbit deflection depends on particle energy vertical dispersion [D(s)] σ = ε β + δ y y 2 y 2 D small vertical beam size relies on good orbit 994: 3 vertical orbit corrections in physics

7 Average Luminosity L n b I e + σ x σ I e - y beam size is determined by synchrotron radiation and optics constant Beam Lifetime: I(t) = I e -t/ τ I t Residual gas pressure -8 P < Torr [atmosphere: P = 75 Torr] Compton scattering

8 Thermal and Synchroton Radiation Photons: Compton Scattering Beam Gas Torr - τ = Beam thermal photons Beam synchrotron photons g τ = tp 2 hours 8 hours τ = 34 hours sp Total τ = tot 4 hours

9 LHC - Hardware 7 TeV p-p Collider: discovery potential (Higgs) LEP Tunnel: π (2 R = 27 km) B = 8.4 T Superconducting Magnets: f(t, B, I) I = 7 A T =.9 K magnet quench! double bore; L = 5 m field quality Cooling: superfluid He 3 ktons coldmass; 9 Tons He p-p and Ion Beams: (Pb; Ca) 4 Experiments (2 + 2)

10 LHC Layout 2 Ring Layout: RF IP4 CMS TOTEM IP5 extraction IP6 collimation machine protection IP3 beam beam2 IP7 IP2 ALICE injection b IP ATLAS IP8 LHCb injection b2 2 in magnet design 4 proton experiments + ion experiment beam cross over in 4 IR s

11 Circular Accelerators uniform B field: R = const. r = m Q γ B v p = Q B L 2π E / c for E >> E realistic synchrotron: B field is not uniform: drift space for installation different types of magnets space for experiments etc E = Q c 2π B d l high beam energy requires: high magnetic field large packing factor F

12 Why 8.4 Tesla? required maximum dipole field: B γ 2π B[T] =.3 p[gev/c] F L[meter] Physics: p = 7 GeV/c LEP tunnel: L = 27 meter arcs: L = 222 meter only 8% of the arc are filled with dipoles: F =.8 B max = 8.38 T iron saturation: 2 Tesla 4 earth:.3 * Tesla

13 Power Consumption LEP: B =.35 Tesla I = 45A; R = m Ω ca. 5 magnets P = R I 2 P = 2 kw / magnet P = MW LHC: B I B max = 8.38 T I = 28 A (current density!) P > 78 MW / magnet ca. 5 magnets P > 39 GW superconducting technology! 8.4 T is at the limit of available technology!

14 Bending Magnet saturation B magnetic induction H magnetic field amplification process does not work for fields above 2 Tesla! field quality control via pole face shape does not work for the LHC magnets! use the coil design to determine the field quality cosine field distribution in the magnet cross section generates a uniform vertical dipole field coil precision and stability is a major concern for superconducting magnets!

15 Superconducting Magnets a a y r I B I φ x r > a: B = µ I [-sin( φ), cos( φ), ] 2 π r µ r < a: j r B = [-sin( φ), cos( φ), ] 2 Overlap the two cylinders: A r p x y r 2 B φ φ 2 2 r cos( ) - r cos( ) = d r sin( φ ) - r sin( φ 2 2 ) = B y = const. C B x = j = in C

16 Coil Winding: vacuum pipe beam superconducting cable Superconducting Cable: Persistent Currents: = -c rot E wire cable NbTi + Cu B Ι Ι e B t e

17 LHC - Beam Parameter L = N 2 p ε β n b f rev 2 π Beam-Beam Interaction: Beam Size: Q magnet quality + N b ε < 5-3 aperture N = p ε β: quadrupole strength + β =.5 meter n = 2835 b I beam =.5 A aperture Beam Power E = 3 MJ = 2 kg TnT Synchrotron Radiation P =.5 W/m

18 Summary LHC Magnet Technology: B = 8.4 T; Beam Energy: E = 7 TeV; field errors quench performance beam losses Bunch Current: N p = ; beam-beam limit Beam Current: I =.5 A; synchrotron radiation collective effects

19 Other Projects Tevatron: Chicago, USA p / p E = TeV km; ring; B = 4.5 T; T = 4.2 K n = 6 36; I = 2 ma; range: 6 b beam HERA: e / p E =.9 TeV 99 Hamburg, Germany RHIC: 6.3 km; 2 rings; B = 5.5 T; T = 4.4 K n = 8; I =.5 ma; range: 2 b beam Au/Au; p / p New York, USA E =.25 TeV 999 b 3.8 km; 2 rings; B = 3.5 T; T = 4 K n = 57 4; I = 3 µ A; range: 7 beam LHC: B = 8.4 T; T =.9 K; range = 6; I =.5 A beam

20 Future VLHC: magnet technology 95 km; 2 ring; B = 2 T; n = km; 2 ring; B = 2 T; n = 3 Muon Collider: muon source muon lifetime (τ = 2.2 µ s ) lepton collider without synchrotron radiation Linear Collider: USA / Japan Germany CERN 5 GeV / 3 TeV NC SC NC; 2 beams

21 Linear Collider No Bending Field: reduced synchrotron radiation Beam Size: σ / γ High Frequency: E = - e e A t high frequency λ = c f small structure Tesla: NLC: CLIC:.3 GHz.4 GHz 3 GHz alignment and wakefields

22 What Else? High Energy Physics Nuclear + Atomic Physics: LEAR: anti-hydrogen Synchrotron Radiation Sources: solid state physics chemestry biology Hospitals: cancer treatment Industry: surface treatment sterilisation nuclear waste disposal