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

2. Daresbury Campus Cockcroft Institute
Cockcroft Education Lectures M W Poole

3. 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

4. Birth of Particle Physics and Accelerators
1898 Discovery of radium (a, b, g) 7.6 MeV
1909 Geiger/Marsden MeV a backscattering - Manchester
1927 Rutherford demands accelerator development
Particle accelerator studies start - Cavendish
1929 Cockcroft and Walton start high voltage experiments
1932 The prize achieved: Cockcroft + Walton split Li !!!!
‘High’ voltage generation – brute force
UK grid initiated (132 kV) and industrial base started

5. Walton, Rutherford, Cockcroft - 1932
Start of the modern era – particle accelerators
NOBEL PRIZE !

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

7. Early Challenges High voltage breakdown Reliable vacuum systems
Low beam currents
Zero diagnostics
Small industrial base
Scale – big science emerges !

8. Electrostatic Accelerator Development
Tuve builds multi-MV Tesla transformers
1931 van der Graaff pioneers effective electrostatic solution (1 MV)
MeV machine at Liverpool (Manchester collaboration)
1972 Design Study of MV facility at Daresbury
1974 Civil construction starts
1983 NSF commissioned – world’s highest energy operation
Closure

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

10. Seriously high voltages !
Cockcroft Education Lectures M W Poole

11. 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
Linear Accelerator = LINAC
Wideroe
Cockcroft Education Lectures M W Poole

12. Resonant Accelerator Concept - LINAC
Drift tubes screen beam
Synchronism and bunching
Original CERN linac
Wideroe – 1928
Alvarez

13. Linac Challenges Development of RF power sources – energy limit
Unsuitable for electrons – velocity too high
Beam dynamics - radial fields at gaps
Need for correction fields
Permanent magnet solutions
Scale issues (only few MeV/m)

14. Recirculation Concept - Cyclotron
Radio frequency alternating voltage
D-shaped RF cavities
time t =0
Lawrence:
4” – 80 keV
11” MeV
Hollow metal drift tubes
time t =½ RF period
q v B = mv2 / r
r = mv / qB
T = 2pm / qB
Orbit radius increases
with energy
Expensive/impractical for
high energies (1 GeV)
Automatic
Synchronisation
Cockcroft Education Lectures M W Poole

15. Accelerator Developments
High energy Cyclotrons have huge magnets - spiral orbits
Also problem of relativistic mass increase: desynchronises
(some help from FM synchrocyclotron)
Solution:
Raise magnetic field strength as particle energy increases
Produces annular orbit geometry
SYNCHROTRON

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

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

18. RF Accelerating Cavities
Typically MHz – 3 GHz kV
Single cell example – modified pill box
Cockcroft Education Lectures M W Poole

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

20. Properties of Charged Particle Beams
Unstable behaviour first encountered by Lawrence
Restoring forces provided by radial magnetic field variation (shims)
Uncoupled transverse motion with periodic driving terms
Hamiltonian solutions - now rare (simulations) canonical x,p
Betatron oscillations occur (tunes Qx/Qy) – and dispersion function
Weak focussing replaced by strong focussing (Q >> 1) => resonances
Ensemble of particles
Lattice functions
Phase space area = emittance

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

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

23. Lattice Functions - DBA Example
Cockcroft Education Lectures M W Poole

24. Errors and Nonlinearities
Real accelerators are non-ideal
Misalignments and field errors must be corrected
Nonlinear behaviour must be controlled (fields and motion)
Implies diagnostics and magnetic correctors
Simulated behaviour is crucial – complex analysis

25. Example - Chromatic Correction
Sextupoles – compensate
off-energy particle tune shift
B ~ x2
Located in finite dispersion region: focussing varies with energy offset

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

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

28. Phase Synchronism NOTE: This leads to BUNCHING about A
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
Cockcroft Education Lectures M W Poole

29. Engineering Challenges
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
Reliability

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

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

32. Daresbury Laboratory - 1964
Cockcroft Education Lectures M W Poole

33. Construction of NINA
Cockcroft Education Lectures M W Poole

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

35. The NINA Synchrotron
Cockcroft Education Lectures M W Poole

36. Grand Opening of NINA
Cockcroft Education Lectures M W Poole

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

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

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

40. 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 a E4/R2
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

41. Relativistic Emission
Electron rest frame
Laboratory frame b f q b
Transforming between frames
tan q = g -1sin f (1 + b cos f ) -1
if f = 900
then: q = g -1
Relativistic Emission Cone
Cockcroft Education Lectures M W Poole

42. Emission from Bends First observed 1947 Electron Acceleration
Cone angle = 1/g
Acceleration
g = E/m0c2
First observed 1947
GE Synchrotron
Cockcroft Education Lectures M W Poole

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

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

45. 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

46. Crab Nebula Accelerators in Space
Cockcroft Education Lectures M W Poole

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

48. 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
Cockcroft Education Lectures M W Poole

49. Storage Rings Synchrotrons can store beams at required (final) energy
Very high beam currents can be accumulated (100’s mA)
Beam lifetime set by:
Instabilities gas scattering IBS beam-beam etc
Typically hours (1012 turns !!!)
Radiation damping benefits electron rings (3D)
Exotic cooling schemes needed for protons (and ions)

50. Daresbury SRS Concept World’s first dedicated x-ray source Linac
80 keV
2 GeV
Linac
Storage Ring
Booster
12 MeV
Beamlines
600 MeV
Cockcroft Education Lectures M W Poole

51. Use of Existing Buildings
Cockcroft Education Lectures M W Poole

52. SRS Storage Ring Parameters
Electron Energy 2 GeV
Operating Current 300 mA
Total Circumference 96 m
Revolution Frequency 3.1 MHz
Pressure in Beam Tube atm
Number of Dipoles 16
Dipole Current at 2 GeV 1,420 A
Dipole Field T
RF Power Input to Beam 250 kW
Stored Beam Lifetime 30 hours
Cockcroft Education Lectures M W Poole

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

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

55. Real Synchrotron Radiation
Beam port
Cockcroft Education Lectures M W Poole

56. 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

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

58. 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

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

60. Compact Light Sources Demand is high for access to Light Sources
National facility scale dominates landscape
Alternatives include example of HELIOS (700MeV)
Daresbury led design
Commissioned 1991 (OI/Daresbury)
IBM operated for lithography trials
Superconducting magnets (4.5 T)

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