ichst-iran cern hight school teacher program-7-8...

Introductory workshop about CERN for high school teachers, Tehran, Iran27‐28 April 2016, 7‐8 Ordybhrsht 1395

AcceleratorsM. Yarmohammadi Satri

(Institute for Research in Fundamental Sciences (IPM))

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Contents

Why Accelerator machines and Colliders ?

A very Brief Historical Overview

The Main Ingredients for having an Accelerator

7‐8 Ordybehesht 1395 (27‐28 April 2016) ‐ Tehran

Why Accelerator machines ?Why Accelerator machines and Colliders ?

Visible lightλ = 400 700 nm

X rayλ = 0.01 10 nm

Particle acceleratorλ <0.01 nm

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Colliding

All energy will be available for particle production

ColliderFix target

Much of the energy is lost in the target and only part is used to produce secondary

particles

The goal

• Verify the Standard Model

• Search for physics beyond the Standard Model


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Accelerators and our life

[*] World Scientific Reviews of Accelerator Science and Technology, A.W. Chao

Today: ~ 30’000 operational accelerators around the world *.

The large majority is applied in industry and medicine

The low minority is serving for research and discovery science: CyclotronSynchrotron light sources (e‐) Linear and circular accelerator colliders

In your old TV set: Cathode Tube


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Electrostatic accelerators

750 kV Cockcroft‐Walton Linac2 injector at CERN from 1978 to 1992

Strong electrostatic potential development of high voltage generators

Two methods succeded : Crockcroft‐Walton voltage multiplierand Van de Graaff electrostatic generator. It allowed first artificialnuclear transmutation, Li + p→ 2×α + 17 MeV

Only 20 years later, 1951, they awarded the Nobel prize “for their pioneer work on the transmutation of atomic nuclei by artificially accelerated atomic particles”.

John Douglas Cockcroft Ernest Walton

Constant potential difference, Energy gain in [eV]

Acceleration limited to few MeV (electric field breakdown)

Still used in very first stage of acceleration


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Wideroe linac

He succeeded to accelerate potassium ions in that structure, up to 50 keV.

• 1928, Rolf Wideroe demonstrates resonant acceleration by using the Ising principle with a 1 MHz, 25 kV generator.

High frequency and high power generators were not available.

Alvarez

Development of Radar technology during the WW II. Competences in the MHz‐GHz range.From Wideroe to Alvarez

• 1946, L. Alvarez and co‐workers at the Lawrence Berkeley Radiation Laboratory developed a proton linear accelerator.


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1929‐1930, Ernest O. Lawrence inspired by Wideroe & Ising ideas invents (the principle of) the cyclotron

Cyclotron

In 1939 Lawrence the Noble prize for his work.

1932, the cyclotron (30 cm) built by Lawrence produces protons at 1.25MeV.


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Synchrotrons

1959: CERN (PS) and BNL (AGS)

Fixed radius for particle orbit

Focusing of the beam particles

Providing beam for fixed target physics

Paved the way to colliders


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The Cern accelerator complex


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Beam

Diag

CavityTransport(Magnet)

RF Powersupply

Cooling

Powersupply

Diag Diag

DiagDiag

Control

Vaccum

The Main Ingredients for having an Accelerator


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RF

Sign

alE 0

RF Phase (°)

Synchronous Part.

Early Part.

Late Part.

RF

Sign

alE 0

RF Phase (°)

Acceleration & Bunching

Acceleration & Debunching

Deceleration & Debunching

Deceleration & Bunching

We have to define how to accelerate, deviate and focus the beam

RFpower supply

Wave guide

Power coupler

Cavity

BEAM

field

The synchronous part gets the correct kickThe late part gains slightly more energyThe early part gains slightly less energy.

RF structure


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Focusing quadrupoleDefocusing quadrupole

FFDD focusing structure FODO focusing structure

B field is focusing in one plane but defocusing in the other.

Magnet (Quadrupole)


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1

Magnet (Bending)


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A bunch of particles is characterized by its distribution in the 6D-phase space.

X

Y

ZBEAM

(z,zʹ)

(x,xʹ)(y,yʹ)

Eye of the accelerator physicists

7‐8 Ordybehesht 1395 (27‐28 April 2016) ‐ Tehran14

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Beam intensity or current measurement

Transverse beam profile/size measurement



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Longitudinal beam profile measurements

Emittance measurement


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LEIR (Low Energy Ion Ring) an example

Dipoles


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LEIR (Low Energy Ion Ring) an example

Quadrupoles


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Beam injecting & extracting

Kicker MagnetSeptum Magnet

Extracted beam

Circulating beam Beam to be extracted

Non magnetic field

magnetic field


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Kicker MagnetSeptum Magnet

Incoming beam

Circulating beam Injected beam

Non magnetic field

magnetic field

The rate of produced particles is expressed by the simple relation:

.

: Interaction cross section of the physical process (property of nature that is fixed)L : Luminosity (describes efficiency of the accelerator)

Two bunches with N1 and N2 particles in opposite direction beams, revolution frequency frevand the number of bunches Nb collide at zero crossing angle, luminosity is:

CERN, projects and the IPM contributionsIntrod

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2 operating modes: low duty for PSBooster (PSB) injection in the first phase,high duty for the other project in a secondphase.

Re‐use 352 MHz LEP RF components: klystrons, waveguides, circulators.

Ion species H‐

Output Energy 160 MeVBunch Frequency 352.2 MHzMax. Rep. Rate 2 HzBeam Pulse Length 400usMax. Beam Duty Cycle 0.08 %Chopper Beam‐on Factor 62 %Chopping scheme:

222 transmitted /133 empty bucketsSource current 80mARFQ output current 70mALinac pulse current 40mABeam power 5.1MWN. particles per pulse 1.0× 1014Transverse emittance 0.4πmm mrad

• Plan for commissioning LINAC4 in 6 stages with twotemporary measurement benches

• The beam will reach to 160MeV at the end of 2016

• A year for reliability run and sending a short beam pulse onthe main dump

• The connection to the PSB during the LHC shut down

Linac4


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12 MeV3 MeV

102 MeV

160 MeV

50 MeV

45 keV


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CLIC (Compact Linear Collider), CTF3


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Credits• much of the material is taken directly from Rende Steerenberg , CAS.• from previous linac courses at CAS and JUAS by Alessandra Lombardi, J‐B

Lallement(http://cas.web.cern.ch/cas)

Further reading• Thomas Wangler “RF Linear Accelerators”, Wiley Series in Beam physics and

accelerator technology.• Andrew Sessler, Edmund Wilson, “Engines of discovery, A Century of Particle

Accelerator”.


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Questions ?

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ichst-iran cern hight school teacher program-7-8...

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