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
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Beam intensity or current measurement
Transverse beam profile/size measurement
Eye of the accelerator physicists
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Eye of the accelerator physicists
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:
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: 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:
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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”.
7‐8 Ordybehesht 1395 (27‐28 April 2016) ‐ Tehran
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257‐8 Ordybehesht 1395 (27‐28 April 2016) ‐ Tehran
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Questions ?
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7‐8 Ordybehesht 1395 (27‐28 April 2016) ‐ Tehran