MAGNET TECHNOLOGY CENTRE

Accelerators, CERN and High Energy PhysicsPekka Suominen

European summer school on superconductivity 12.6.2008

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Contents

Motivation for accelerators; nuclear physics, medical and industrial applications

Principles of different types of particle accelerators

Superconducting components in accelerators (magnets, RF-cavities)

Magnet systems of ion sources

CERN & LHC

Magnets systems of particle detectors

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Accelerators – where?

CRT – Cathode Ray Tube

– (1) Electron accelerator (15 - 30 kV)

– (3) Focusing by (electro or permanent) solenoid magnets

– (4) Deflection by XY-magnets (eg. 100 Hz)

– (7) Phosphor layer with RGB zones

…

Soon to be replaced by LCD

© Wikipedia

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Motivation for accelerators: nuclear physics

Studying the nucleus of the atom, their interactions, related forces and nuclear models. Trying to understand

– the nature of nucleonic matter.– the origin of the elements. – events and the astrophysical sites that produce the elements.

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Nuclear physics instrumentation

Detectors

Alpha

Beta

Gamma

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Motivation for accelerators: particle physics

Also called high energy physics

Studies the elementary constituents of matter and radiation, and the interactions between them

Standard Model: all particles except the Higgs boson have been observed motivation for LHC

1895 - X-rays produced by Wilhelm Röntgen (later identified as photons)[1]1897 - Electron discovered by J. J. Thomson[2]1899 - Alpha particle discovered by Ernest Rutherford in uranium radiation[3]1900 - Gamma ray (high-energy photon) discovered by Paul Villard in uranium decay.[4]1911 - Atomic nucleus identified by Ernest Rutherford, based on scattering observed by Hans

Geiger and Ernest Marsden.[5]1919 - Proton discovered by Ernest Rutherford[6]1932 - Neutron discovered by James Chadwick[7] (predicted by Rutherford in 1920[8]) 1932 - Positron, the first antiparticle, discovered by Carl D. Anderson[9] (proposed by Paul Dirac

in 1927) 1937 - Muon discovered by Seth Neddermeyer, Carl Anderson, J.C. Street, and E.C. Stevenson,

using cloud chamber measurements of cosmic rays.[10] (It was mistaken for the pion until 1947.[11])

1947 - Pion discovered by Cecil Powell (predicted by Hideki Yukawa in 1935[12]) 1947 - Kaon, the first strange particle, discovered by G.D. Rochester and C.C. Butler[13]1955 - Antiproton discovered by Owen Chamberlain, Emilio Segrè, Clyde Wiegand, and

Thomas Ypsilantis

1956 - Neutrino detected by Frederick Reines and Clyde Cowan (proposed by Wolfgang Pauli in 1931 to explain the apparent violation of energy conservation in beta decay)

1962 - Muon neutrino shown to be distinct from electron neutrino by group headed by Leon Lederman

1969 - Partons (internal constituents of hadrons) observed in deep inelastic scattering experiments between protons and electrons at SLAC; this was eventually associated with the quark model (predicted by Murray Gell-Mannand George Zweig in 1963) and thus constitutes the discovery of the up quark, down quark, and strange quark.

1974 - J/ψ particle discovered by groups headed by Burton Richter and Samuel Ting, demonstrating the existence of the charm quark (proposed by Sheldon Glashow, John Iliopoulos, and Luciano Maiani in 1970)

1975 - Tau lepton discovered by group headed by Martin Perl1977 - Upsilon particle discovered at Fermilab, demonstrating the existence of the

bottom quark (proposed by Kobayashi and Maskawa in 1973) 1979 - Gluon observed indirectly in three jet events at DESY1983 - W and Z bosons discovered by Carlo Rubbia, Simon van der Meer, and the

CERN UA-1 collaboration (predicted in detail by Sheldon Glashow, AbdusSalam, and Steven Weinberg in the 1960s)

1995 - Top quark discovered at Fermilab[14][15]2000 - Tau neutrino shown to be distinct from other neutrinos at Fermilab

© wikipedia:

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Particle physics instrumentation

Very large setups (like Compact Muon Solenoid)

More details comes after…

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Motivation for accelerators: medical applicationsElectron emitter (gun)AcceleratorBeam manipulation (focussing, bending, steering, …)

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Medical applications – Hadron therapy

X-rays Proton therapy Carbon therapy

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Motivation for accelerators: Industrial applications

Several fully automatic (turn-key) ion implantation systems available

Typical ion energies are in the range of 10 to 500 keV

Semiconductor device fabrication

– Used to alter the surface properties of semiconductor materials

– Doping

Metal finishing

– Tool steel toughening

– Surface finishing

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Motivation for accelerators: Industrial applications

Electronics radiation-hardness tests

Simulation of space radiation environment

– Reliability of electronics in space

Heavy ion irradiation chamber and ion diagnostics. © RADEF, Jyväskylä Finland

RADEF's proton station

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Free Electron Laser (FEL)

Use accelerator & synchrotron radiation to create high power laser radiation

© DESY, Hamburg

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TESLA XFEL project (DESY, Hamburg, Germany)

Ribosomes are large molecular complexes that act as "protein factories" and occur in every cell. The X-ray laser opens up completely new opportunities to decipher such biological structures with atomic resolution without the need for the extra step of tediously growing them into crystals first.

Users dream will soon become reality

Single shot imaging of single biomolecular complexes

– Needs many photons on the sample

Time resolved studies of structural processesduring chemical and biological reactions

©D

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Y, H

ambu

rg

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Accelerators in the world (2002)(Old fashion CRT-televisions are not counted)

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Principles of different types of particle accelerators

How to accelerate?

- Use electric field on charged particle

(and magnets for steering & focusing)

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High voltage generation

Wimhurst machine (~1880)

~10 kV Van de Graaff generator1929 Cockroft-Walton

voltage multiplier Up to 1 MV

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Linear accelerator (LINAC)

Principle of DC acceleration (static DC E-field)

– Intermediate electrodes are necessary for beam focusing (E-field shaping)

p+

Ion source on

HV terminal

Target on ground potential

700 kV 0 kV600 kV 500 kV 400 kV 300 kV 200 kV 100 kV

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LINAC history

An idea to double the energy:

– Place ion source on positive potential (+5 MV to ground)

– Laboratory with detectors sits on negative potential (-5 MV to ground)

Not very convenient to work inside HV-terminals…

Ion source

Laboratory

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Linear acceleratorIon source on High Voltage (HV) terminal

Few MegaVolts

Van de Graaff generator

Ion sourceHV terminal

© BNL

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Tandem linear acceleratorHigh Voltage (HV) terminal on center Injection and extraction on ground potential

Up to 20 000 000 Volts (20 MV) terminal

– H- stripped to proton: 40 MeV energy

– O- (Oxygen) stripped to O5+: 120 MeV energy

Charging pellets Pelletron™

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Tandem linear accelerator

The ESTU (Extended Stretched TransUranium) tandem accelerator at the A.W. Wright Nuclear Structure Laboratory, Yale University

21 MV terminal

Intensities up to 20 microamps

30 meters long

SF6 gas insulation (green house gas

problems)

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Linear accelerator (LINAC)

From DC acceleration to AC / RF acceleration

p+

700 kV

Ion source on

HV terminal

0 kV600 kV 500 kV 400 kV 300 kV 200 kV 100 kV

Target on ground potential

p+

+/- 100 kV+/- 50 kVAC / RFMHz … GHz

DC

AC

Target on ground potential

Ion source on ground potential

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RF LINACs

Why RF?

– Electric fields:DC: 1 MV/mMHz: 10 MV/mGHz: 100 MV/m

To reach 1 Gigavolt: 10 m GHz LINAC (1 km with DC)1 Teravolt: 10 km GHz LINAC (1000 km with DC impossible)

CLIC @ CERN (Design study for a 3 TeV e+e- Linear Collider, site length 48 km)

© CERN © GSI

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Circular accelerators

RF

RF

RFRF RF RF

Single pass

- Use the same RF structure and make the particles circulate many turns inside the accelerator

PARAMETERS CHECK LISTBeam energyVelocityFrequencyMagnetic field

Large dipole magnet is needed for bending

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Cyclotron

Static magnetic field

Constant Radio Frequency

© Ernest Lawrence, 1929University of California, Berkeley

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Cyclotron - largest

TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics

H- ions to up to energies of 520 MeVMagnet diameter 18 mMagnet weight 4000 tonsRF: 23 MHz, 94 kV

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Cyclotron Synchrotron

RF

(a lot of iron is saved)

CyclotronConst. FrequencyConst. Magnetic field

RF

SynchrotronFrequency increases with E

– If not ultrarelativistic

Magnetic field increases with E

(1) Injection

(3) Extraction

(2) Acceleration

106 pulses / second1 pulse / second

Lower cost per GeV

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Synchrotron

In picture: Brookhaven national laboratory / Alternating Gradient Synchrotron (AGS) under construction (in 1957). Emax = 33 GeV

Many Nobel Prizes to accelerator physicists!

This machine only:

– Samuel C.C. Ting:Discovery of the J/psi Particle(1976)

– James W. Cronin and Val L. Fitch: CP Violation (1980)

– Leon Lederman, Melvin Schwartz and Jack Steinberger: Discovery of the Muon-Neutrino(1988)

© BNL

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Synchrotron

Accelerator magnets

– Dipoles (for bending)

– Quadrupoles (for focusing)

– Sextupoles (for beam manipulation and error correction)

– Octupoles (for beam manipulation and error correction)

– Special fast pulsing magnets for injection and extraction

Often the bending magnets are only about 50% of the synchrotron length

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Synchrotron colliderOne beam pipe (CERN-LEP)

electron – positron

proton – antiproton

Two beam pipes (CERN-LHC)

electron - electron

proton – proton

or for example lead – lead

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Superconducting components in accelerators

Magnets, RF cavities, beam diagnostics & instrumentation

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Superconducting cyclotron

Superconducting 250 MeV Cyclotron for proton radiation therapy

Commercially available (ACCEL Instruments GmbH)

Center 2.4 T

Conductor 4 T

D = 3.2 m

© PSI© Accel

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SC Radio Frequency cavities

A collection of SCRF cavities developed at Cornell University with frequencies spanning 200 MHz to 3 GHz.

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Development of SCRF cavities

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Magnet systems of ion sources

Particle accelerator needs particles to accelerate need of sophisticated ion sources

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Atom to ion (ionization)

Neutral carbon atom Charged carbon - ion

One electron is missing

Positive total charge

”Feels” electric and magnetic fields

Accelerators

-

-

-

-

-

-

-

--

-

6+

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Electron Cyclotron Resonance Ion Source (ECRIS)

Injection:microwaves +gas

Highly charged ionsare extracted via high voltage

Strong magnetic field:

Solenoids (electric magnet)

Permanent magnetmultipole

Microwaves will heatthe gas to plasma-state, which is trappedin a ”magnetic bottle”

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ECR Ion Source: VENUSSC hexapole inside SC solenoids

– Strong forces– Gamma-radiation heat load to cryostat

© LBNL

© LBNL

© LBNL

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CERN & LHC

History

Today

Future (?)

Conseil Européen pour la Recherche Nucléaire(European Council for Nuclear Research)

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CERN

Established on 29 September 1954

20 member states and 8 observers

Located close to Geneva on Swiss-France border

Its main function is to provide particle accelerators and infrastructure for high-energy physics research

2600 full-time employees + some 8000 scientists and engineers working in related projects

The World Wide Web began in CERN, in a project initiated by Tim Berners-Lee and Robert Cailliau (1989)

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CERN accelerator complex today

50 MeV

1.4 GeV

28 GeV

450 GeV

p+: 7 TeV

Pb54+: 575 TeVCircumference 27 km

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CERN & LHC

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LHC dipoles

© CERN

© CERN

© CERN

© CERN

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Magnets systems of particle detectors

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CERN - CMS Experiment (Compact Muon Solenoid)

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© CERN

The silicon strip tracker of CMS

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CMS Magnet

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CERN & LHC

CMS

ATLAS

A Toroidal LHC ApparatuS

Compact MuonSolenoid

MAGNET TECHNOLOGY CENTREATLAS Experiment© CERN

• 25 MB / event

• 40 MHz

• 1 Petabyte/s

Triggering allows to reduce the data

• 100 MB/s

1 PB / year

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LHC is a big SMES(H)

One LHC dipole stores 7.8 MJ (0.12 H, 11.5 kA)– (weight 26 tonnes equivalent KineticE 88 km/h)

– There are 1232 dipoles 10 GJ

+ ATLAS: 1.2 GJ

+ CMS: 2.7 GJ

+ Additional 400 smaller SC magnets

Also the beam stores a lot of energy!

– 2 x 362 MJ = 724 MJ (two beams)

– Beam dump needs to absorb 362 MJ of beam energy in the 90 μs circulation time, which equates to a power of 4 TW.

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CERN ECR Ion SourceFirst experiments with proton – proton (collision energy = 14 TeV)

After: lead – lead (collision E = 1150 TeV)

– Produced Pb27+ Stripped to Pb54+

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CERN – future (?)Compact Linear Collider (CLIC) study

– Maximum achievable accelerating field (>150 MV/m) in order to lower the cost per GeV

– Needs a lot of high power RF systemdevelopment