Engines of Discovery R.S. Orr Department of Physics University of Toronto Berkley 1930 1 MeV Geneva 20089 14 TeV
Birth of Particle Physics and Accelerators 1909 Geiger/Marsden MeV a backscattering - Manchester 1919 Rutherford disintegrates Nitrogen - Manchester 1927 Rutherford demands accelerator development Particle accelerator studies - Cavendish 1929 Cockcroft and Walton start high voltage experiments 1932 The goal achieved: Cockcroft + Walton split Li nucleus
665 kv Cockcroft-Walton Generator
Ising 1924
Resonant Accelerator Concept Wideroe - 1928 Alternating (radio frequency) fields allow higher voltages The acceleration occurs in the electric field between cylindrical drift tubes. The RF power must be synchronised with the motion of the electrons, so that acceleration occurs in every gap. Linear Accelerator = LINAC
Recirculation Concept - Cyclotron Radio frequency alternating voltage D-shaped RF cavities Hollow metal drift tubes time t =0 Lawrence: 4 80 kev 11-1.2 MeV time t =½ RF period Orbit radius increases with momentum Orbital Frequency independent of momentum Particle motion and RF in phase
Equilibrium Orbit Constant revolution frequency f rev v 2 v eb 2 mv eb 2m Magnetic rigidity B mv e p e
Orbit Stability Slight Displacement from Equilibrium Orbit Particle Lost Vertical and Horizontal Focusing
Vertical Orbit Stability in Lawrence s Cyclotron Cross Section Thru Ds Electrostatic Focusing Lens
Orbital Stability in a Cyclotron SHIMS q F v B c
Horizontal B z n R Bz 2 0 r mv e vbz R c 0 0 Betatron Oscillations Field Index Equilibrium Orbit Centrifugal = Lorentz on equilibrium orbit m B x z 2 d y dt Vertical e vb c 2 x B z 0 x F x mv r 2 e vb c z Restoring Force 2 m d y n B z e v F 2 dt Rc z F x mv R 2 x R 1 n Simple Harmonic 2 2 d y v m nm dt R 2 2 0 x v R 1 n Stable Oscillations around Equilibrium orbit n v z R 2 2 n 1 Weak Focusing n 0
This machine is just a model for a bigger one, of course This machine is just a model for a bigger one, of course 1931 4 10 Volts 1953 9 10 Volts 1932 6 10 Volts This machine is just a model for a bigger one, of course 1960 10 10 Volts
Invention of the Synchrotron Marcus Oliphant later to become Governor of South Australia
Synchrotron Ring Schematic Accelerating Bending magnets cavity Increase magnetic field during acceleration. Constant orbital radius Vacuum tube Focusing magnets
1 0 1 0 L 1 L 1 f 1 1 1 0 1 1 f f L 2 f L L 1 f 1 0 L 1 2 f L f Net Focusing FODO Lattice Strong Focusing
Strong Focusing Field Index set by Pole Face Shape Weak, n = 0.5 Strong, n = 3500 Strong Focusing = Alternating Gradient Combined Function Magnet
Enormous Cost Saving Weak Focusing Magnet Strong Focusing = Alternating Gradient Reduce amplitude of betatron oscillations Reduce diameter of vacuum pipe Reduce Aperture of Magnets Strong Focusing Magnet 35 GeV (CERN PS, AGS) costs same as 7 GeV (NIMROD)
TRAJECTORY 2 dy ds 2 K s Y 0 Y s A scos s Y s s cos s BEAM ENVELOPE 2 d ds K s 1 2 3 s 2 s Amplitude of betatron oscillations
angle Single Particle Phase Space Beam Envelope position Real Accelerator Non-linear Shape of phase space changes along accelerator lattice Area constant -> Liouville
Successive turns around accelerator lattice A B C B is synchronous with RF phase A too energetic to be in phase B not energetic enough to be in phase E E ev s sin n1 s n s Closed Oscillations in Phase (non relativistic) Synchronous particle 1 1 2 2 Change in transit time around lattice
E E ev sin s n1 s n s Synchronous Particle n1 n 2 n1 v Es n1 n 2 c E E E ev sin Non-Synchronous Particle sin s Symplectic Mapping Preserves Phase Space
Unconfined motion = lost particles Stable oscillations Trapped by RF Synchronous particle separatrix Transformed s into Φ position around lattice Particle orbits in energy-phase
d E E ev dn s n1 2 v E c s 2 s n E sin s de dn ev sin sin s Non-linear equations Describing deviation in phase and energy from synchronous orbit
H Initial condition cos sin s separatrix RF Bucket constant = Η 2 2 1 d c = cos sin 2 2 s dn v E s
CERN Seen from the Air Tunnels of CERN accelerator complex superimposed on a map of Geneva. Accelerator is 50 m underground 25 km in circumference
Superconducting Magnet 8 Tesla In order to accelerate protons to high energy, must bend them in circular accelerator 7 TeV momentum needs intense magnetic field
LHC 2002
LHC 2003 Dipole Cold Masses
Ph. Lebrun ATLAS Plenary Meeting 18 February 2005
Infrastructure completed in 2003
Underground
Dipole-dipole interconnect
March 2006
Descent of the Last Magnet, 26 April 2007 300 m underground at 2 km/h!
RF Modules
Tunnel Cavern Shaft Surface Refrigeration Units at 1.8 K Point 8 Storage Air Liquide QSCC QSCA QSCB QSRA QSRB QSCC IHI Linde QURA QUIC QURC QURC Sector 7-8 Sector 8-1
Tunnel Cavern Shaft Surface Cryogenic Distribution Point 8 Storage QSCC QSCA QSCB QSCC QSRA QSRB QURA QUIC QURC QURC Sector 7-8 Sector 8-1
DFBA Electrical Feed Box Connection to magnets Shuffling module Vacuum equipment VAA Current lead chimneys 6kA leads 13kA leads x 16 2 per LHC Point SHM/HCM interconnect High current module 13kA & 6kA leads Jumper cryo connection to QRL Supporting beam 6kA leads Removable door 600A leads HCM/LCM interconnect Low current module 6kA & 600A leads 1.9K 4.5K
13 ka HTS Current Leads
6 ka current leads with water-cooled cables
Lyn Evans EDMS docment no. 970483 45
Beam 2 first beam D-Day 46
Beam on turns 1 and 2 Courtesy R. Bailey 47
No RF, debunching in ~ 25*10 turns, i.e. roughly 25 ms Courtesy E. Ciapala 48
First attempt at capture, at exactly the wrong injection phase Courtesy E. Ciapala 49
Capture with corrected injection phasing Courtesy E. Ciapala 50
Capture with optimum injection phasing, correct reference Courtesy E. Ciapala 51
LHC longitudinal bunch profile Beam 2 52
H wire scan Lyn Evans EDMS document no. 970483 53
54 Kick response compared with theoretical optics
Alors, c est fini! Et maintenant?
Storage Ring Stable phase = 0 No acceleration
Synchrotron (phase) oscillations 2 2 d c ev cos 0 2 2 s dn v E s 2 d t s 2 0 2 s dn t s 0 ; ; cos 0 0 ; ; cos 0