Short Introduction to CLIC and CTF3, Technologies for Future Linear Colliders Explanation of the Basic Principles and Goals Visit to the CTF3 Installation Roger Ruber
The CRT: Our Home Accelerator = × + F e ( v B E ) = F m a Roger Ruber - CLIC/CTF3 Visit - Introduction 2
Collider History p p “Livingstone” plot (adapted from W. Panofsky) • hadron collider at the frontier of physics – huge QCD background – not all nucleon energy available in collision [top quark] e+ e- [W ± , Z boson] [N ν =3] • lepton collider for precision physics [gluon] – well defined CM energy [charm quark, τ lepton] – polarization possible • LHC starting up – energy constantly increasing – consensus for next machine E cm ≥ 0.5 TeV for e + e - Roger Ruber - CLIC/CTF3 Visit - Introduction 3
Hadrons versus Leptons: Typical Event Patterns Hadron collision Lepton collision e- e+ p p Simulation of HIGGS production e + e – → Z H Z → e + e – , H → b b Roger Ruber - CLIC/CTF3 Visit - Introduction 4
Circular versus Linear Collider accelerating cavities N N S S Circular Collider many magnets, few cavities, stored beam higher energy → stronger magnetic field → higher synchrotron radiation losses ( ∝ E 4 /R) source main linac Linear Collider few magnets, many cavities, single pass beam higher energy → higher accelerating gradient higher luminosity → higher beam power (high bunch repetition) Roger Ruber - CLIC/CTF3 Visit - Introduction 5
Cost of Circular & Linear Accelerators cost Circular Collider Linear Collider energy 200 GeV e - Circular Collider Linear Collider • Δ E ~ (E 4 /m 4 R) • E ~ L • cost ~ aR + b Δ E • cost ~ aL • optimization: R~E 2 → cost ~ cE 2 Roger Ruber - CLIC/CTF3 Visit - Introduction 6
Linear Collider R&D RF power RF power Source Source Interaction Point with Detector e + source e + Linac e - source e - Linac accelerating cavities accelerating cavities Challenges: 1. high accelerating gradient 2. efficient power production Roger Ruber - CLIC/CTF3 Visit - Introduction 7
Acceleration of Charged Particles • Lorenz (EM) force most practical = e × + e - F ( v B E ) - + • increasing particle energy - + ∫ Δ = ⋅ = E e E d r eU • to gain 1 MeV energy requires a 1 MV field Direct-voltage acceleration used in • TV tube: 20~40 kV • X-ray tube: ~100 kV • tandem van de Graaff: up to ~25 MV Roger Ruber - CLIC/CTF3 Visit - Introduction 8
Higher Integrated Field: Modulation with Drift Tubes • shields particle while field direction is reversed • length adapted to particle velocity & RF frequency Courtesy E. Jensen electric field Roger Ruber - CLIC/CTF3 Visit - Introduction 9
Static or Modulated Fields (RF) DC acceleration not always possible: • keep beam tube at ground potential • circular machine: ∫ ⋅ = E d s 0 → use oscillatory waveform Proton E kin β = v/c 50 MeV 0.314 1.4 GeV 0.916 25 GeV 0.999 3 PS 450 GeV 0.999 998 SPS 7 TeV 0.999 999 991 LHC Roger Ruber - CLIC/CTF3 Visit - Introduction 10
Surfing: or How to Accelerate Particles DC Accelerator RF Accelerator Roger Ruber - CLIC/CTF3 Visit - Introduction 11
Cavity Type Acceleration Configuration • time-varying electro-magnetic field: – magnetic field encircles beam – accelerating gap fed with RF voltage r r ∂ r r E B ∫ ⋅ = − ∫∫ ⋅ E d s d A ∂ t B • cell length must be proportional to – particle velocity – frequency • magnetic field tracks particles’ energy to keep equilibrium orbit unchanged Roger Ruber - CLIC/CTF3 Visit - Introduction 12
Standing Wave Pillbox Cavity TM 010 -mode (only 1/8 shown) Courtesy E. Jensen electric field (@ 0 o ) magnetic field (@ 90 o ) Roger Ruber - CLIC/CTF3 Visit - Introduction 13
CERN PS 19 MHz Cavity (prototype 1966) Roger Ruber - CLIC/CTF3 Visit - Introduction 14
Standing Wave Cavity • long pulse time • frequency <3 GHz Beam • typical 2~5 MV/m • superconducting 1 Electric field 0 . 5 z up to ~30 MV/m 0 0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 (at time t 0 ) - 0 . 5 - 1 l= βλ /2 • ions & electrons, all energies Roger Ruber - CLIC/CTF3 Visit - Introduction 15
Travelling Wave Structure • short pulses • high frequency >3 GHz • typical 10~20 MV/m • CLIC: – 12 GHz RF RF power load – 240 ns source – 100 MV/m particle bunch electric field d • electrons β ~1 (v~c) Roger Ruber - CLIC/CTF3 Visit - Introduction 16
Linear Collider R&D RF power RF power Source Source Interaction Point with Detector e + source e + Linac e - source e - Linac accelerating cavities accelerating cavities Challenges: 1. high accelerating gradient 2. efficient power production Roger Ruber - CLIC/CTF3 Visit - Introduction 17
Klystron RF Power Amplifier • velocity modulation (RF in ) of electron bunch → microwave amplifier • output power (RF out ) 1 MW continuous 150 MW pulsed • 0.1 – 300 GHz range 5 – 10% bandwidth • expensive (40-60% efficiency) and high maintenance cost Roger Ruber - CLIC/CTF3 Visit - Introduction 18
CLIC Two-beam Power Distribution Scheme • high power drive beam like the modulated klystron beam • power extraction in a deceleration structure (PETS) • high power, high frequency • sub-harmonic frequency of main beam • compress energy density: “transformer” function drive beam main beam Roger Ruber - CLIC/CTF3 Visit - Introduction 19
Recombination to Increase Peak Power & Frequency Drive Beam Accelerator Delay Loop x 2 efficient acceleration in fully loaded linac gap creation, pulse compression & frequency multiplication RF Transverse Deflectors Combiner Ring x 3 pulse compression & frequency multiplication Combiner Ring x 4 pulse compression & frequency multiplication Drive Beam Decelerator Sector Power Extraction Drive beam time structure - initial Drive beam time structure - final 240 ns 240 ns 5.8 µs 140 µs train length - 24 x 24 sub-pulses - 4.2 A Roger Ruber - CLIC/CTF3 Visit - Introduction 20 24 pulses – 100 A – 2.5 cm between bunches 2.4 GeV - 60 cm between bunches
Drive Beam Generation Scheme Roger Ruber - CLIC/CTF3 Visit - Introduction 21
Linear Collider R&D RF power RF power Source Source Interaction Point with Detector e + source e + Linac e - source e - Linac accelerating cavities accelerating cavities Challenges: 1. high accelerating gradient 2. efficient power production 3. build a working accelerator Roger Ruber - CLIC/CTF3 Visit - Introduction 22
CLIC: Compact Linear Collider Main Linac C.M. Energy 3 TeV 2x10 34 cm -2 s -1 Peak luminosity Beam Rep. rate 50 Hz Pulse time duration 156 ns Average field gradient 100 MV/m Φ 4.5m tunnel # accelerating cavities 2 x 71,548 Roger Ruber - CLIC/CTF3 Visit - Introduction 23
CTF3 Test Facility • demonstration drive beam generation • evaluate beam stability & losses in deceleration • develop power production & accelerating structures X 2 Drive Beam Accelerator Delay loop Drive Drive beam Beam 42 m generation Injector scheme 30 GHz High Gradient Test stand CLEX X 5 Combiner Ring Drive beam stability bench marking 84 m Decelerator Test Beam Line 30 A - 150 MeV Two-Beam Test-stand 180 MeV Probe 140 ns CLIC sub-unit Beam Injector Roger Ruber - CLIC/CTF3 Visit - Introduction 24
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