ILC concepts / schematic

Transcription

1 INFN School on Electron Accelerators September 2007, INFN Sezione di Pisa Lecture 1a ILC concepts / schematic Carlo Pagani University of Milano INFN Milano-LASA & GDE

2 The Standard Model Fundamental Particles and Interactions Carlo Pagani 2

3 Just to Remind m = γ m 0 E 0 = m 0 c 2 γ = (1-β 2 ) -1/2 β = v/c E= mc 2 Momentum Kinetic energy p = m v m 0 γ c K = E E 0 = (γ -1) m 0 c 2 Speed of light: c = ms -1 Energy unit: 1 ev = J Electron rest energy: E 0 = MeV Proton rest energy: E 0 = 938 MeV Carlo Pagani 3

4 Energy Frontier and e + e - Colliders LHC ILC LEP at CERN E cm ~ 200 GeV P RF ~ 30 MW Carlo Pagani 4

5 Colliding Beams for High Energy E.J.N. Wilson Carlo Pagani 5

6 LHC, ILC and Meson Factories Since the ILC will start after the start of LHC, it must add significant amount of information. This is the case! Neither LC nor HC s can draw the whole picture alone. ILC will add new discoveries and the precision of ILC will be essential for a better understanding of the underlying physics. High Luminosity Meson Factories are though being also essential for a deeper understanding of a few key mechanisms. There are probably pieces which can only be explored by the LHC due to the higher mass reach. Joint interpretation of the results will improve the overall picture Overlapping running of different machines increases the potential of each machine and might turn out to be mandatory, depending on the physics scenario beyond the Standard Model Carlo Pagani 6

7 Simulations of Higgs events at CMS CERN-EX _05 CERN-EX _10 Carlo Pagani 7

8 Cyclotron: constant B RF acceleration: Synchrotron The LEP Example Synchrotron: constant ρ mv B ρ = = q p q Accelerating cycle Strong focusing concept For v c E [GeV] 0.3 B [T] ρ [m] Carlo Pagani 8

9 No Circular e + e - Collider after LEP Synchrotron Radiation: charged particle in a magnetic field: B Energy loss dramatic for electrons U SR 21 4 [ GeV ] = 6 10 γ 1 r[ km] U SR = energy loss per turn γ = relativistic factor r = machine radius γ proton / γ electron 2000 Energy loss replaced by RF power cost scaling $ E cm 2 Carlo Pagani 9

10 A Simple Exercise Synchrotron Radiation (SR) becomes prohibitive for electrons in a circular machine above LEP energies: U SR 21 4 [ GeV ] = 6 10 γ 1 r[ km] RF system must replace this loss, and r scale as E GeV/beam: 27 km around, 2 GeV/turn lost Possible scale to 250 GeV/beam i.e. E cm = 500 GeV: 170 km around 13 GeV/turn lost Consider also the luminosity For a luminosity of ~ /cm 2 /second, scaling from b-factories gives ~ 1 Ampere of beam current 13 GeV/turn x 2 amperes = 26 GW RF power Because of conversion efficiency, this collider would consume more power than the state of California in summer: ~ 45 GW Both size and power seem excessive U SR = energy loss per turn γ = relativistic factor r = machine radius γ 250GeV = Circulating beam power = 500 GW Carlo Pagani 10

11 A great success for LEP II Accelerating Field Evolution with time from G. Geschonke s Poster for the ITRP visit to DESY Number of cavities GeV 100 GeV 104 GeV design 96 GeV: Mean Nb/Cu 6.1 MV/m 100 GeV: 3500MV Mean Nb/Cu 6.9 MV/m 104 GeV: 3666MV Mean Nb/Cu 7.5 MV/m Final energy reach limited by allowable cryogenic power Accelerating field [MV/m] Carlo Pagani 11

12 Origin of the Linear Collider Idea M. Tigner, Nuovo Cimento 37 (1965) 1228 A Possible Apparatus for Electron-Clashing Experiments (*). M. Tigner Laboratory of Nuclear Studies. Cornell University - Ithaca, N.Y. While the storage ring concept for providing clashingbeam experiments ( 1 ) is very elegant in concept it seems worth-while at the present juncture to investigate other methods which, while less elegant and superficially more complex may prove more tractable. Carlo Pagani 12

13 Linear Collider Conceptual Scheme Final Focus Demagnify and collide beams Bunch Compressor Reduce σ z to eliminate hourglass effect at IP Damping Ring Reduce transverse phase space (emittance) so smaller transverse IP size achievable Electron Gun Deliver stable beam current Main Linac Accelerate beam to IP energy without spoiling DR emittance Positron Target Use electrons to pairproduce positrons Carlo Pagani 13

14 Energy & Luminosity In a collider Luminosity is as important as Energy The center of mass Energy, E c.m. is the Energy/Mass budget available for the creation of a consistent evolution of fermions and bosons - particles and forces is a temperature limit, or a time limit, for the reconstruction of the universe evolution from the big-bang is the upper limit to the complexity of the events that are accessible. The Luminosity, L is a measure of the number of collisions, i.e. energy packages, that the machine produces in a second once multiplied for a rare event cross section gives the number of the pictures per second that could be taken For E c.m. ~ 500 [GeV], L ~ [cm -2 s -1 ] is required Carlo Pagani 14

15 Fighting for Luminosity L 2 Ne σ σ x L = Luminosity y σ y σ x L n b f rep n b = # of bunches per pulse N e = # of electron per bunch σ x,y = beam sizes at IP IP = interaction point L b E P c.m. σ N x e σ y f rep = pulse repetition rate P b = beam power E c.m. = center of mass energy Parameters to play with Reduce beam emittance (ε. x ε y ) for smaller beam size (σ. x σ y ) Increase bunch population (N e ) Increase beam power ( P N n f ) b Increase beam to-plug power efficiency for cost e b rep Carlo Pagani 15

16 ILC versus LHC or LEP 1 For a given E c.m., Luminosity is determined by the maximum acceptable beam power and by the minimum obtainable emittance. σ y << σ x for beamstrahlung and bunch length is optimized. Beam Power In a storage ring collider as LHC: the same particles are circulating 10 4 times in a second, contributing 10 4 time to the beam current and power each of the two LHC beams will have a circulating power close to 4 TW, while for a linear collider we have to use 10 MW as the a reference value should the linac technology being able to transform plug power into beam power with a 10% unprecedented conversion efficiency. This would ask for a plug power of 200 MW that while twice higher than the one installed for the LHC operation is still considered as acceptable. Carlo Pagani 16

17 ILC versus LHC or LEP - 2 Beam Quality (normalized emittance) and Sources In a storage ring collider Beam Quality is a consequence of the overall machine design. The maximum density at the interaction point is limited by the life time of the beam. In a linear collider the beam is spent after each collision: the minimum attainable emittance is required to allow the maximum possible density at the interaction point. minimum emittance is generated in a damping ring and the linac has to preserve this value up to the interaction point. A flat beam is required to minimize the beamstrahlung induced energy spread at the interaction. beam bunches have to be longitudinally compressed for instabilities and focusing at the interaction point fresh particles per second have to be generated and cooled, half electrons and half positrons. Carlo Pagani 17

18 Competing technologies 1.3 GHz - Cold 30 GHz-Warm 11.4 GHz - Warm Carlo Pagani 18

19 Linear Colliders are pulsed LCs are pulsed machines to improve efficiency. As a result: duty factors are small pulse peak powers can be very large <1 µs-1ms < ms RF Pulse 100 m km nsec... Bunch Train accelerating field pulse: gradient with further input without input Beam Loading filling loading Carlo Pagani 19

20 ILC-TRC (Greg Loew Panel) International LC Technical Review Committee International Collaboration for R&D toward TeV-Scale e + e LC asked for first ILC-TRC in June 1994 ILC-TRC produced first report end of : ICFA requests that ILC-TRC reconvene to produce a second report with the following charge: To assess the present technology status of the four LC designs at hand, and their potential for meeting the advertised parameters at 500 GeV c.m. Use common criteria, definitions, computer codes, etc., for the assessments To assess the potential of each design for reaching higher energies above 500 GeV c.m. To establish, for each design, the R&D work that remains to be done in the next few years To suggest future areas of collaboration ILC-TRC produced second report January Carlo Pagani 20

21 LC status at first ILC-TRC End 1995 E cm = 500 GeV TESL A SBLC JLC- S JLC- C JLC- X NLC VLEPP CLIC f [GHz] L [cm -2 s - 1 ] P beam [MW] P AC [MW] γε y [ 10-8 m] σ y * [nm] Carlo Pagani 21

22 Tasks to be addressed Baseline cm Energy stays at 500 GeV Push Luminosity to the maximum value Technology: Demonstrate that the proposed technology can be pushed to the limits required for a Linear Collider Demonstrate that the proposed technology can be produced in large scale by industry with high reliability and reasonable cost Find solution for all critical items Design issues: Demonstrate that very small spot sizes (σ x. σ y < 1 µm 2 ) are possible Investigate all beam physics critical issues Support all design features with cross-checked simulations Address reliability and availability issues Roadmap for energy upgrade Test Facilities Carlo Pagani 22

23 TTF for TTF = TESLA Test Facility TTF Goals: Demonstrate that Superconducting RF technology is suitable for LC Operate TTF at E acc > 15 MV/m Develop cavity technology for Eacc > 25 MV/m TTF as operated for SASE FEL Carlo Pagani 23

24 NLCTA Goals: NLCTA for NLCTA = NLC Test Accelerator RF system integration test of a NLC linac section Test efficient, stable and uniform acceleration of a NLC-like bunch train klystron SLED II pulse compression X 4 3db hybrid 40 m resonant delay lines beam accelerating structures Carlo Pagani 24

25 ATF = Accelerator Test Facility ATF Goals: ATF for Demonstrate very low beam emittance Develop RF technology Damping ring Cavity Production Carlo Pagani 25

26 CTF for CTF3 = CLIC Test Facility #3 (Under construction after CTF1 and CTF2) CTF3 Goals: Demonstrate the drive beam scheme Develop RF structures and technology Carlo Pagani 26

27 Lessons from the SLC SLC = SLAC Linear Collider IP Beam Size vs Time 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. Beam Size (microns) SLC Design (σx σy) σ X σ y σ X σ Y σ x σ y (microns 2 ) Slow/fast feedback theory and practice Year 1 0 Carlo Pagani 27

28 2 nd to 1 st ILC-TRC Comparison 2003 vs E cm = 500 GeV TESLA 2003 TESLA 1995 JLC/NLC 2003 <JLC/NLC > 1995 CLIC 2003 CLIC 1995 f [GHz] L [cm -2 s - 1 ] P beam [MW] P AC [MW] γε y [ 10-8 m] σ y * [nm] Carlo Pagani 28

29 Beam Sizes M. Tigner Carlo Pagani 29

30 Technology Choice: NLC/JLC or TESLA The International Linear Collider Steering Committee (ILCSC) selected the twelve members of the International Technology Recommendation Panel (ITRP) at the end of 2003: Asia: G.S. Lee A. Masaike K. Oide H. Sugawara Europe: J-E Augustin G. Bellettini G. Kalmus V. Soergel North America: J. Bagger B. Barish (Chair) P. Grannis N. Holtkamp First meeting end of January 2004 at RAL Mission: one technology by end 2004 Result: recommendation on 19 August COLD Carlo Pagani 30

31 From the ILC Birthday Carlo Pagani 31

32 From the ILC Birthday Carlo Pagani 32

33 ILC Pictorial View (TESLA Like) As at the Technology Recommendation time Carlo Pagani 33

34 GDE Actual Members Director Carlo Pagani 34

35 ILC actual scheme (as in the RDR) Carlo Pagani 35

36 RDR Design Parameters Max. Center-of-mass energy Peak Luminosity 500 ~2x10 34 GeV 1/cm 2 s Beam Current 9.0 ma Repetition rate 5 Hz Average accelerating gradient 31.5 MV/m Beam pulse length 0.95 ms Total Site Length 31 km Total AC Power Consumption ~230 MW Carlo Pagani 36

37 ILC Reference Design 11km SC linacs operating at 31.5 MV/m for 500 GeV Centralized injector Circular damping rings for electrons and positrons Undulator-based positron source Single IR with 14 mrad crossing angle Dual tunnel configuration for safety and availability Carlo Pagani 37

38 ILC Reference Design and Plan - 1 6km Damping Ring Making Positrons 10MW Klystrons Beam Delivery and Interaction Point Carlo Pagani 38

39 ILC Reference Design and Plan - 2 Producing Cavities Cavity Shape Obtaining Gradient single cells Carlo Pagani 39

40 Cryomodules TESLA cryomodule 4 th generation prototype ILC cryomodule Carlo Pagani 40

41 The Main Linac Costs have been estimated regionally and can be compared. Understanding differences require detail comparisons industrial experience, differences in design or technical specifications, labor rates, assumptions regarding quantity discounts, etc. Carlo Pagani 41

42 ILC Facility Overview Carlo Pagani 42

43 The ILC Linac in a Double Tunnel Three RF/cable penetrations every rf unit Safety crossovers every 500 m 34 kv power distribution Carlo Pagani 43

44 Summary of Conventional Facilities 72.5 km tunnels ~ meters underground 13 major shafts > 9 meter diameter 443,000 m 3. underground excavation: caverns, alcoves, halls 92 surface buildings, 52,000 m 2 Carlo Pagani 44

45 ILC Value by Area Systems Main Cost Driver Conventional Facilities Components Carlo Pagani 45 45

46 ILC Global Design Phase Barry Barish Global Design Effort Project Baseline configuration Reference Design LHC Physics Engineering Design ILC R&D Program Expression of Interest to Host International Mgmt Carlo Pagani 46