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Lecture 1 - Overview of Accelerators I
ACCELERATOR PHYSICS
MT 2010
E. J. N. Wilson
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Links
Author’s e-mail: [email protected]
“Engines of Discovery”:
http://www.worldscibooks.com/physics/6272.html
http:// www.enginesofdiscovery.com
“Particle Accelerators”
http://www.oup.com/uk/catalogue/?ci=9780198508298
mailto:[email protected]://www.worldscibooks.com/physics/6272.htmlhttp://www.oup.com/uk/catalogue/?ci=9780198508298http://www.oup.com/uk/catalogue/?ci=9780198508298http://www.worldscibooks.com/physics/6272.htmlmailto:[email protected]
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Lecture 1 – Overview I- Contents
History of accelerators
Need for accelerators
Linear accelerator
Acceleration on a wave
Magnetic rigidity
Cyclotron
Magnetic rigidity
Vertical focussing
Components of a synchrotron
Phase stability
Weak focusing synchrotrons
Weak focusing in a synchrotron
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The history of accelerators
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Need for Accelerators
Why do we need accelerators? (2)
Resolution of "Matter" Microscopes:
Wavelength of Particles (Photon, Electron, Proton, ...): (de Broglie, 1923)
λ = h / p ( = 1.2 fm / [ GeV/c] )
The higher the momentum, the shorter the wavelength, the better the
resolution
Energy to Matter:
Einstein (1905):
Higher energy means we can produce more massive particles
When particles approach the speed of light, they get more massive, but
not faster
33
E = mc2 = moc
2
1−v
2
c2
= γ moc2
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The race to high energies
Rutherford fired the starting pistol
At the Royal Society in 1928 he said
“I have long hoped for a source of positive particles more energetic than those emitted from
natural radioactive substances”.
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Cockcroft and Walton - Electrostatic
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Van der Graaf
Van de Graaff was a Rhodes Scholar at Oxford when he first thought
about electrostatic machines. This is very large accelerator built at
MIT's Round Hill Experiment Station in the early 1930s.
Under normal operation, because the electrodes were very smooth and
almost perfect spheres, Van de Graaff generators did not normally spark.
However, the installation at Round Hill was in an open-air hanger,
frequented by pigeons, and here we see the effect of pigeon droppings.
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Linear accelerator
Particle gains energy at each gap Lengths of drift tubes follow increasing
velocity
Spacing becomes regular as v approaches c
Wideroe’s first linac:
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Wideroe’s Linac
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Fermilab linac (400MeV)
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Inside the Fermilab linac
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The Stanford Linear Accelerator
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TESLA technology: thesesuperconducting accelerator structures
are built of niobium, and are the crucial
components of the International Linear
Collider.
The International Linear Collider(ILC)
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A picture of the 11-inch cyclotron built by
Lawrence and his graduate students, David
Sloan and M. Stanley Livingston, during1931.
Cyclotrons –an inspired discovery
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Cyclotron
B ρ = mve
= pe
f rev = v2πρ
= v2π
eBmv
= eB2π m
Magnetic rigidity
Constant revolution frequency
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Magnetic Rigidity
e v×B =d p
dt
d p
dt = p
d θ
dt = p
ρ
ds
dt
ev ×B = eB ds
dt
B ρ T .m[ = pc eV
c m.s−1= 3.3356 pc
from resolution of momenta that:
the magnitude of the force may be written:
Equating the right hand sides of the two expressions above,we find we can define a quantity known as magnetic rigidity:
A common convention in charged particle dynamics is toquote pc in units of electron–volts. Whereupon:
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Vertical Focusing
People just got on with the job of building them.
Then one day someone was experimenting
Figure shows the principle of vertical focusing in a cyclotron
In fact the shims did not do what they had been expected to do
Nevertheless the cyclotron began to accelerate much higher currents
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Discovery of the Synchrotron
MarcusOliphant – anAussie – later tobecomeGovernor of
South Australia
The Arsenal Synchrotron- Late in WorldWar II the Woolwich Arsenal ResearchLaboratory in the UK had bought abetatron to "X-ray" unexploded bombs in
the streets of London. Frank Gowardconverted the betatron into the first “proofof principal”
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Components of a synchrotron
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Phase stability
V = V 0 sin(2π f a + φ s )
PHS.AD5
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Cosmotron
COSMOTRON.PCT
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Weak focusing in a synchrotron
Vertical focusing comes from the curvatureof the field lines when the field falls off withradius ( positive n-value)
Horizontal focusing from the curvature of thepath
The negative field gradient defocuses
horizontally and must not be so strong as tocancel the path curvature effect
The Cosmotron magnet
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Summary
History of acceleratorsNeed for accelerators
Linear accelerator
Acceleration on a wave
Magnetic rigidity
Cyclotron
Magnetic rigidity
Vertical focusing
Components of a synchrotron Phase stability
Weak focusing synchrotrons
Weak focusing in a synchrotron
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