Particle Physics: Status and PerspectivesPart 3: Accelerators

Manfred Jeitler

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electron microscope

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Van-de-Graaf generator

4Fundamental Accelerator Theory, Simulations and Measurement Lab – Arizona State University, Phoenix January 16-27, 2006

Van de Graaff Accelerator:Van de Graaff Accelerator:ApplicationsApplications

Changing theParticle EnergyF. Sannibale

Tandem SchemeTandem Scheme

•Negative ions (HNegative ions (H-- for example) are for example) are created and accelerated through the created and accelerated through the

first stagefirst stage•At the end of the first stage the At the end of the first stage the

electrons are electrons are ‘‘strippedstripped’’ out from the out from the ions (by a gas target for example)ions (by a gas target for example)

•In the second stage the positive ions In the second stage the positive ions (protons in our example) are (protons in our example) are

accelerated. The net energy gain is accelerated. The net energy gain is twicetwice the voltage of the Van de Graaff the voltage of the Van de Graaff

+

++

+++ +

1st Stage

2nd Stage

5Fundamental Accelerator Theory, Simulations and Measurement Lab – Arizona State University, Phoenix January 16-27, 2006

Electrostatic Accelerators:Electrostatic Accelerators:The Simplest SchemeThe Simplest Scheme

Changing theParticle EnergyF. Sannibale

Still one of the most used schemes for electron sourcesStill one of the most used schemes for electron sources

- --

-- -

Cathode Anode

Budker InstituteBudker Institute

Diode PierceGeometry

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Cockroft-Waltonaccelerator

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Cockroft-Walton accelerator at CERN

8Fundamental Accelerator Theory, Simulations and Measurement Lab – Arizona State University, Phoenix January 16-27, 2006

RF Accelerators:RF Accelerators:Wideroe and Alvarez SchemesWideroe and Alvarez Schemes

Changing theParticle EnergyF. Sannibale

In 1946 Alvarez overcame to the In 1946 Alvarez overcame to the inconvenient by including the Wideroe inconvenient by including the Wideroe structure inside a large metallic tube structure inside a large metallic tube forming an efficient cavity where the forming an efficient cavity where the

fields were confined.fields were confined.

In 1925-28 Ising and Wideroe conceived the first linear accelerator (linac). The In 1925-28 Ising and Wideroe conceived the first linear accelerator (linac). The revolutionary device was based on the revolutionary device was based on the drift tubes schemedrift tubes scheme..

Synchronicity condition:Synchronicity condition:

At high frequency the Wideroe scheme becomes lossy due to electromagnetic At high frequency the Wideroe scheme becomes lossy due to electromagnetic radiation.radiation.

During the decelerating half period of the RF, the beam is shielded inside the During the decelerating half period of the RF, the beam is shielded inside the conductive tubes.conductive tubes.

200 MHz RF200 MHz RFsource from radarssource from radars

The Alvarez structures are still widely used as pre-accelerator for protons and The Alvarez structures are still widely used as pre-accelerator for protons and ions. The particles at few hundred keV from a Cockcroft-Walton for example, are ions. The particles at few hundred keV from a Cockcroft-Walton for example, are

accelerated to few hundred MeV.accelerated to few hundred MeV.

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inside of an Alvarez-typeaccelerating structure

The cyclotron

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Cyclotron

r.............orbit radiusp...........particle momentume............particle chargeB............magnetic field

revolution frequency must be independent of the particle‘s momentum !

12Fundamental Accelerator Theory, Simulations and Measurement Lab – Arizona State University, Phoenix January 16-27, 2006

Cyclotron andCyclotron andSynchro-cyclotronSynchro-cyclotron

Changing theParticle EnergyF. Sannibale

1939 Nobel PrizeProton Source

UniformMagnetic

Field

AcceleratedProtons

ElectricField

For non-relativistic particlesFor non-relativistic particlesthe revolution periodthe revolution period

does not depend on energydoes not depend on energy

• If the RF frequency is equal to the particles revolution frequency synchronicity is If the RF frequency is equal to the particles revolution frequency synchronicity is obtained and acceleration is achieved.obtained and acceleration is achieved.

• The synchro-cyclotron is a variation that allows acceleration also of relativistic The synchro-cyclotron is a variation that allows acceleration also of relativistic particles. The RF frequency is dynamically changed to matchparticles. The RF frequency is dynamically changed to match

the changing revolution frequency of the particlethe changing revolution frequency of the particle

The first cyclotron4.5” diameter (1929).

In an uniform magnetic field:In an uniform magnetic field:

• In 1946 Lawrence built in Berkeley the 184In 1946 Lawrence built in Berkeley the 184”” synchro-cyclotron with an orbit radius of synchro-cyclotron with an orbit radius of 2.337 m and capable of 350 MeV protons. The largest cyclotron still in operation is in 2.337 m and capable of 350 MeV protons. The largest cyclotron still in operation is in

Gatchina and accelerates protons to up 1 GeV for nuclear physics experiments. Gatchina and accelerates protons to up 1 GeV for nuclear physics experiments.

E. O. Lawrence

13Fundamental Accelerator Theory, Simulations and Measurement Lab – Arizona State University, Phoenix January 16-27, 2006

The Cyclotron:The Cyclotron:Different Points of ViewDifferent Points of View

Changing theParticle EnergyF. Sannibale

By Dave Judd and Ronn MacKenzieBy Dave Judd and Ronn MacKenzie

From LBNL Image LibraryFrom LBNL Image LibraryCollectionCollection

…the operator

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Synchrotron

elements of a synchrotron

quadrupole magnet: focussing

dipole magnet: to keep particles on track

high-frequency accelerating cavity

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SPS Tunnel Super-Proton-Synchrotron (Geneva)

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first electron-electron collider: Novosibirsk / Russia

VEP-1 130+130 MeV

Particle production at a collider

particles do not disintegrate and show what is inside but

the kinetic energy of the colliding particles (protons) is transformed into the mass of another particle

Fixed-target accelerators and colliders

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quadrupole

dipoleresonator

reaction products

interaction zone

layout of a circular collider

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LHC dipole

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layout of the LHC storage ring(built into the former LEP tunnel)

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the world‘s largest accelerators

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luminosity

(instant) luminosity is rate per cross section usual units: cm-2 s-1

e.g., 1030 cm-2 s-1 corresponds, for a reaction cross section of 10-30

cm-2 ( = 1 μbarn), to a rate of 1 event per second

for a collider, the luminosity can be calculated as follows:

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integrated luminosity

number of events collected divided by the cross section usual units: fb-1 (“inverse femtobarn”),

ab-1 (“inverse attobarn”)

an integrated luminosity of 1 fb-1 means that for a process with a cross section of 1 fb, 1 event (on average) should have been collected or 1000 events for a cross section of 1 nb, etc. so, 1 inverse attobarn = 1000 inverse femtobarns :

1 ab-1 = 1000 fb-1

physicists are now looking for very rare events, so it is vital to reach not only high energies (so that heavy particles can be produced) but also high luminosities handling the resulting data rates is a challenge also for the

detectors, trigger systems, and readout electronics

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“Accelerator”: do particles really get faster?

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Years of Design, Construction and Commissioning of the LHC

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accelerator centers worldwide

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photon collider

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layout of a muon storage ring