accelerator physics - wilson

8/9/2019 Accelerator Physics - Wilson

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Lecture 1 - E. Wilson – 14-Oct10 - Slide1

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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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


accelerator physics - wilson

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