Cockcroft Education Lectures M W Poole Introduction to Accelerators Part 1 M W Poole Past Director and Honorary Scientist ASTeC

Cockcroft Education Lectures M W Poole Daresbury Campus Cockcroft Institute

Cockcroft Education Lectures M W Poole Basic Acceleration Principle A voltage drop accelerates charged particles Electrostatic acceleration in cathode ray tubes: televisions computer monitors oscilloscopes

Cockcroft Education Lectures M W Poole Birth of Particle Physics and Accelerators 1909Geiger/Marsden MeV  backscattering - Manchester 1919Rutherford disintegrates Nitrogen - Manchester 1927Rutherford demands accelerator development Particle accelerator studies start - Cavendish 1929Cockcroft and Walton start high voltage experiments 1932The prize achieved: Cockcroft + Walton split Li !!!! ‘High’ voltage generation is UK achievement at this stage – brute force UK grid initiated (132 kV) and industrial base started

Cockcroft Education Lectures M W Poole Walton, Rutherford, Cockcroft Start of the modern era – particle accelerators NOBEL PRIZE !

Cockcroft Education Lectures M W Poole Cockcroft-Walton Generator ISIS 665 kV Removed 2005 Greinacher 1921 See our Atrium !

Cockcroft Education Lectures M W Poole Electrostatic Monster: the NSF 1936 van der Graaff pioneers electrostatic solution (2.5 MeV) MeV machine at Liverpool (Manchester collaboration) 1972 Design Study of MV facility at Daresbury 1974 Civil construction starts 1983 NSF commissioned 1992 Closure World’s highest voltage machine No nuclear physics replacement

Cockcroft Education Lectures M W Poole Daresbury Nuclear Structure Facility (NSF) Last of the line ! Van de Graaf 20+ MV

Cockcroft Education Lectures M W Poole Seriously high voltages !

Cockcroft Education Lectures M W Poole Resonant Accelerator Concept 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 cavity. This naturally produces bunches of electrons Wideroe Linear Accelerator = LINAC

Cockcroft Education Lectures M W Poole Recirculation Concept - Cyclotron Radio frequency alternating voltage Hollow metal drift tubes time t =0 time t =½ RF period Synchronisation Necessary D-shaped RF cavities Orbit radius increases with energy Expensive/impractical for high energies (1 GeV) Lawrence: 4” – 80 keV 11” MeV q v B = mv 2 / r r = mv / qB T = 2  m / qB

Cockcroft Education Lectures M W Poole Accelerator Developments High Energy Cyclotrons have huge magnets - spiral orbits Also affected by relativistic mass increase - desynchronise Solution: Raise magnetic field strength as particle energy increases Produces annular orbit geometry SYNCHROTRON

Cockcroft Education Lectures M W Poole Synchrotron Ring Schematic Focusing magnets Vacuum tube Accelerating cavity Bending magnets Bending and focussing often combined

Cockcroft Education Lectures M W Poole Magnet Focusing FQUADs (shown above) focus the beam horizontally. DQUADs (as above, rotated 90º) focus the beam vertically. Quadrupole magnets are used to focus the beam.

Cockcroft Education Lectures M W Poole RF Accelerating Cavities Single cell example Typically 100 MHz – 3 GHz kV

Cockcroft Education Lectures M W Poole RF Power Sources Klystrons and other tubes Microwave industry solutions

Cockcroft Education Lectures M W Poole Simple Accelerator Lattice Dipole F Quadrupole D Quadrupole FODO Cell finite dispersion

Cockcroft Education Lectures M W Poole Betatron Oscillations Transverse motion of particles in both planes is harmonic - as they deviate from the design orbit a restoring force increases with displacement The particles follow betatron oscillations as they orbit the accelerator - value known as tunes The amplitude and wavelength of this motion is characterised by the beta functions of the accelerator Off-energy particles follow a dispersion function

Cockcroft Education Lectures M W Poole Phase Space Beta function gives transverse envelope Emittance measures phase space area

Cockcroft Education Lectures M W Poole The Double Bend Achromat Cell Dipole Quadrupoles Sextupoles Dipole Quadrupole Dispersive Path Dipole Non - Dispersive

Cockcroft Education Lectures M W Poole Lattice Functions - DBA Example

Errors and Nonlinearities Real accelerators are non-ideal Misalignments and field errors must be corrected Nonlinear behaviour must be controlled Implies diagnostics and steering correctors Simulated behaviour is crucial Cockcroft Education Lectures M W Poole

Example - Sextupole Magnets Chromatic Correction (off-energy particle tune shift) Located in finite dispersion region: focussing matches energy offset

Cockcroft Education Lectures M W Poole Penalty: Collapse of Dynamic Stability No sextupolesCorrected to zero chromaticity by single magnet family

Cockcroft Education Lectures M W Poole Four families Six families Eight families Recovery of Stability - Sextupoles in Patterns

Cockcroft Education Lectures M W Poole Phase Synchronism Synchronous particle (A) crosses cavity after one turn at same phase relative to RF peak Particle B delayed behind A receives higher accelerating voltage and therefore after next turn returns nearer or even ahead of A Particles undergo harmonic synchrotron oscillations about A as they orbit the accelerator NOTE: This leads to BUNCHING about A

Engineering Issues Definition of beam stay clear aperture around a ring Allocations for oscillations, closed orbit errors, injection,.... Vacuum chamber walls and alignment (maybe bake out) Mass component production issues Radiation hardness Controls engineering: multi-parameter optimisation Cockcroft Education Lectures M W Poole

Early (UK) History (Synchro)Cyclotrons Berkeley (Lawrence) 60” (1939) Liverpool 37” 20 MeV (1939) Harwell 110” 175 MeV (1949) Liverpool 156” 380 MeV (1954) (extraction) Linacs Harwell 3.5 MeV (1947) 15 (Mullard), 55 (Met Vickers), 136 MeV Synchrotrons Woolwich Arsenal - Goward & Barnes 8 MeV (1946) (Betatron 1943) Malvern 30 MeV (1950) Oxford 125 MeV (1952) Birmingham 1 GeV p (1953) Glasgow 350 MeV (1954) NIMROD RAL 7 GeV p (1960) NINA DL 5 GeV (1966) Clatterbridge Oncology Centre 65 MeV

Cockcroft Education Lectures M W Poole Origins of Daresbury Laboratory 1957Wilkinson proposes HE electron synchrotron 1960Cockcroft + Cassels propose 4 GeV version 1961Cockcroft proposes Cheshire site !!!! 1962NINA approved - £3.5M Many local sites considered 1963Daresbury selected HEI driving force: Liverpool/Manchester/Glasgow/Sheffield/ (Lancaster)

Cockcroft Education Lectures M W Poole Daresbury Laboratory

Cockcroft Education Lectures M W Poole Construction of NINA

Cockcroft Education Lectures M W Poole A Bad Day at the Office !

Cockcroft Education Lectures M W Poole Grand Opening of NINA

Cockcroft Education Lectures M W Poole The NINA Synchrotron

Cockcroft Education Lectures M W Poole Chadwick’s 75 th Birthday – Daresbury Event

Cockcroft Education Lectures M W Poole NINA Closure UK joined SPS at CERN on condition domestic programme terminated (NINA AND NIMROD) NINA switched off in 1977 Alternative major facilities already sought - and found: NSF (discussed) ISIS and SRS (part 2 next week)

Cockcroft Education Lectures M W Poole EM Radiation from Accelerating Charge Non-relativistic charge source

Cockcroft Education Lectures M W Poole Fundamentals of Radiation Emission Any charge that is accelerated emits radiation Properties calculated since 1897 (Larmor) Lienard and Schott studied relativistic particles on circular trajectories: P  E 4 /R 2 So this applies to accelerated beams of charged particles in a ring (synchrotron) SYNCHROTRON RADIATION => Severe losses and energy restrictions eg NINA

Cockcroft Education Lectures M W Poole Relativistic Emission Relativistic Emission Cone Electron rest frame   Laboratory frame   Transforming between frames tan  =  -1 sin  (1 +  cos    ) -1 if  = 90  then:  =  -1

Cockcroft Education Lectures M W Poole Emission from Bends First observed 1947 GE Synchrotron Electron Cone angle = 1/  Acceleration  = E/m 0 c 2

Cockcroft Education Lectures M W Poole Synchrotron Radiation Spectrum Pulse Length (electron transit arc - photon transit chord) For 2 GeV, 1.2 T: R ~ 5.5 m,  ~ 4000 Wavelength ~ 0.1 nm Typical wavelength

Cockcroft Education Lectures M W Poole Universal Synchrotron Radiation Curve In units of photons/s/mrad/0.1% bandwidth

Cockcroft Education Lectures M W Poole Accelerators in Space Crab Nebula

Cockcroft Education Lectures M W Poole Synchrotron Radiation –New Particle Accelerator Applications Accelerating charged particles emit electromagnetic radiation –very inconvenient for circular electron accelerators ! 1972Scientific use started at Daresbury by Manchester group 1974SRS Design Study (NINA replacement – 2nd Generation) 1980SRS commissioning (world’s first dedicated x-ray source) 1987High brightness upgrade Many pioneering additions: – superconducting wigglers undulators precision beam steering high currents 2008Project termination

Cockcroft Education Lectures M W Poole Daresbury SRS Design studies completed 1975 – anticipate NINA end Based on an electron storage ring World’s first dedicated x-ray source First user programme 1981 Major UK success story for 27 years Pioneering developments and upgrades

Storage Rings and Damping Synchrotrons can operate in a storage mode Losses must be minimised Radiation emission can lead to effective damping processes in all 3 dimensions Originally developed for HEP colliding beams Allow high average beam currents (100’s mA) Opportunity for highly stable source Cockcroft Education Lectures M W Poole

Daresbury SRS Concept Storage Ring Booster Linac Beamlines 80 keV 12 MeV 600 MeV World’s first dedicated x-ray source 2 GeV

Cockcroft Education Lectures M W Poole Daresbury Laboratory

Cockcroft Education Lectures M W Poole SRS Storage Ring Parameters Electron Energy2 GeV Operating Current300 mA Total Circumference96 m Revolution Frequency3.1 MHz Pressure in Beam Tube atm Number of Dipoles16 Dipole Current at 2 GeV1,420 A Dipole Field1.2 T RF Power Input to Beam250 kW Stored Beam Lifetime30 hours

Cockcroft Education Lectures M W Poole SRS Components - High Technology

Cockcroft Education Lectures M W Poole A Synchrotron as an Injector SRS Booster 600 MeV

Cockcroft Education Lectures M W Poole SRS Lifetime (Example) Operating mode is fill storage ring every morning 24/7 running (6000 hours annual)

Cockcroft Education Lectures M W Poole Real Synchrotron Radiation Beam port

Cockcroft Education Lectures M W Poole Synchrotron Radiation Spectrum Broad band source Covers huge spectral range Range set by electron energy and bending field strength Flux/power far exceeds previous sources

Cockcroft Education Lectures M W Poole From Source to Detector Light from source can be split for more than one experiment Light focused using mirrors Narrow range of wavelengths selected by monochromator Light illuminates crystal sample and is diffracted Diffraction pattern observed with detector

Cockcroft Education Lectures M W Poole Wide Range of Applications FMV Virus Structure (1990) Light Harvesting Complex (photosynthesis) Protein Crystallography LIGA Materials science

Cockcroft Education Lectures M W Poole The Nobel Prize: F1 ATPase structure Sir John Walker shared 1997 Nobel Prize for Chemistry - structure of the F1 ATPase enzyme, using the SRS

Cockcroft Education Lectures M W Poole High Field Insertion Devices Normal Straight With Insertion Device SRS Superconducting Wavelength Shifter 6.0 Tesla

Cockcroft Education Lectures M W Poole Alternative Compact Light Source ? Designed at Daresbury Sold by Oxford Instruments to IBM in lithography Operated successfully for 10 years 700 MeV 4.5 T

Cockcroft Education Lectures M W Poole Next: Big Accelerators - CERN etc