Alessandro Cianchi - DidatticaWEB
Transcript of Alessandro Cianchi - DidatticaWEB
A. Cianchi Particle Accelerators For Science And Interdisciplinary Applications
Particle accelerators
Alessandro Cianchi
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Particle accelerators: instructions
48 hrs lectures (16:00 Monday T8bis,11:00 Tuesday T8bis)
No lecture 8,9,15,16 April All the documentation is available via web in pdf @ http://didattica.uniroma2.it/informazioni/index/insegna
mento/180277-Particle-Accelerators-For-Science-And-Interdisciplinary-Applications
Point of view: Physics We will face all the fundamental principles of particle
accelerators But we’ll focus also on the ingoing activities at the
next door
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LNF: the next door
A tour of the accelerators @LNF is included in the course (Jun 3rd likely)
Staff = 350Associates = 181Visitors = 463TOTAL 994
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Final test
Oral examination
Any problem? [email protected]
People interested in email update please send me an email to make an address book
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Basic Syllabus I
Introduction to the importance of the accelerators The history line: Electrostatic accelerators Electrodynamics accelerators:
Cyclotron Betatron Microtron Synchrotron Colliders
Linear optics in the accelerators Equation of motion Transverse dynamics Betatron oscillation Emittance: definition, meaning, measurement The beam envelope equation Resonance and instabilities
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Basic Syllabus II
Longitudinal dynamics Phase stability Equation of motion
The Synchrotron radiation The physics of Synchrotron radiation Transverse and longitudinal dynamics with radiation Light sources FEL
Accelerating structures RF Cavity Principal parameter The future: the plasma acceleration
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Background requested
Basic Electromagnetism, Maxwell equations Did you like Electromagnetism? Good! Did you experience problems? It’s time to make peace!
Special relativity
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What is an accelerator?
It is a device that transfers energy to charged particle by electromagnetic or electrostatic fields. The particles are injected at initial energy of Ti and they arrive to final energy Tf.
Source Accelerator Target
Ti Tf
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What are accelerators used for?
Understanding the fundamental building blocks of nature and the forces that act upon them (nuclear and particle physics)
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Investigate the matter
Understanding the structure and dynamics ofmaterials and their properties (physics, chemistry,biology, medicine) via neutron spallation source oSynchrotron and FEL light sources
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X radiation with fs pulse length
Investigation of the molecular dynamics, chemicalreaction time resolved. Wide range of applicationsfrom physics to pharmacy
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Inverse Compton Scattering
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Medical application of ions
Medical treatment of tumors and cancers, using the properties of the Bragg peak
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Big machines for medical treatment
CNAO is the first center in Italy for tumor treatment using ions produced in a particle accelerator
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Production of medical isotopes
Small size machine devoted to the production of short half-life radioactive isotopes
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Applications
Accelerators (compact cyclotrons or linacs) are used to produce radioisotopes for medical imaging.
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Ion implantation
Electrostatic accelerators are used to deposit ions in semiconductors.
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Electron beam processing
In the US, potential markets for industrialelectron beams total $50 billion per year.
33% Wire cable tubing 32% Ink curing 17% shrink film 7% service 5% tyres 6% other
When polymers are cross-linked, canbecome:
• stable against heat,• increased tensile strength, resistance tocracking• heat shrinking properties etc
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Sterilization
Manufacturers of medical disposables have to kill every germ on syringes, bandages, surgical tools and other gear, without altering the material itself.
E-beam sterilization works best on simple, low density products.
Advantages: takes only a few seconds (gamma irradiation can take hours)
Disadvantages: limited penetration depth, works best on simple, low density products (syringes)
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Food irradiation
‘Cold pasteurisation’ or ‘electronic pasteurisation’
Uses electrons (from an accelerator) or X-rays producedusing an accelerator.
The words ‘irradiated’ or ‘treated with ionizing radiation’ must appear on the label packaging.
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Spallation sources
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Stresses in Airbus A380 Wing
Aircraft manufacturer Airbus has used neutrons since 2006
Research into aluminum alloy weld integrity for aircrew programs
Residual stresses from welding cause weaknesses and the possibility of cracks
Neutrons look deep inside engineering components to measure stress fields
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Fast neutron for semiconductor industry
Atmospheric neutrons collide with microchips and upset microelectronic devices every few seconds
300 x greater effect at high altitude
Neutrons enables manufacturers to mitigate against the problem of cosmicradiation
Increased confidence in the quality and safety of aerospaceelectronic systems
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Driver for fission reactor
MYRRHA as in Multi-purpose hYbrid Research Reactor for High-tech Applications
MYRRHA is the very first prototype of a nuclear reactor driven by a particle accelerator in the world.
Distinctive feature: as an external source of neutrons, this particle accelerator maintains the nuclear fission chain reaction.
It is referred to as a subcritical reactor: the core does not contain enough fissile material to spontaneously maintain the chain reaction.
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Cargo scan
Cargo containers scanned at ports and bordercrossings
Accelerator-based sources of Xrays can be far more penetrating (6MV) than Co-60 sources.
Container must be scanned in 30 seconds.
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Accelerators can study art
This painting “Patch of grass” by Vincent Van Gogh was the first one analyzed by a particleaccelerator
Used X-ray fluorescencetechnique the distribution of Hg and Sb pigment allowed a reconstruction of underlying image
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Accelerators can help spot art forgeries
Ion Beam Analysis shows us the chemical composition of pigments used in paint
This allows art historians to compare them with paints available to artists like Leonardo da Vinci
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Accelerators in archaeology
The interior of samples can be studied usingaccelerators withoutdestroying them
Pomery from Armenia, dating back to 1300 BC, is set up for synchrotron experiment
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Accelerators can make food taste better
Cadbury used X-rays from a particleaccelerator to study how cocoa crystallises
Of the six possible crystal forms, the fifth (form V) produces the best quality chocolate
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And also…
The everyone’s accelerator is…
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Particle accelerators in the world
Accelerators 1994 2014Industrial >4500 27 000
Electron accelerators >300 keV 1500 ∼5000
Electron accelerators <300 keV >1000 ∼8000
Ion implanters and ion analysis >2000 ∼12 000
Neutron generators ∼2000
Science ∼1000 ∼1200
Medicine ∼4200 ∼14 000
Electron accelerators ∼4000 ∼13 000
Proton and ion accelerators 17 ∼59
Production of radioisotopes ∼200 ∼1100
TOTAL >9700 42 000Source: Chernyaev, A. P., and S. M. Varzar. "Particle accelerators in modern world." Physics of Atomic Nuclei 77.10 (2014): 1203-1215.
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Next time someone asks you what accelerators are for
“A beam of the right particles with the right energy at the right intensity can shrink a tumor, produce cleaner energy, spot suspicious cargo, make a better radial tire, clean up dirty drinking water, map a protein, study a nuclear explosion, design a new drug, make a heat-resistant automotive cable, diagnose a disease, reduce nuclear waste, detect an art forgery, implant ions in a semiconductor, prospect for oil, date an archaeological find, package a Thanksgiving turkey or…
…discover the secrets of the universe.”
-Accelerators for Americas FutureReport, pp. 4, DoE, USA, 2011
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Units
1 eV: energy of a particle di charge e, initially at rest, after the acceleration by a potential of 1 V
1 eV= 1.60219 10-19 J
1 keV = 103 eV ; 1 MeV = 106 eV 1 GeV = 109 eV; 1 TeV = 1012 eV
Energy of a proton in the LHC: 7 TeV =1.12 x 10-6J the same energy of a body of mass = 1 mg moving
at speed = 1.5 m /s (a mosquito!)
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Energy and momentum
Protons are accelerated to a kinetic energy of 200 MeV
Calculate their total energy, their momentum and their velocity in our units
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The needs of high energy particles
An accelerator is nothing else than a microscopy
λ =hp
Wavelength of the α– particles used by Rutherford (1911) in the discovery of the atomic nucleus:
m 107.6)s m105.1()kg106.6(
s J 10626.6v
151-727
34−
−
−
×≈×××
×≈=
α
λm
h
0.05 c~ resolving power
of Rutherford’sexperiment
α−particlemass
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Probe for micro cosmos
Resolving power
Optical microscopes Visible Light ~ 10−6 m
Electron microscopes Low energy electron ~ 10−10 m
Radioactive sources α particles ~ 10−14 m
Accelerators High energy electron, protons ~ 10−19 m
Another key point is the production of new particles at even higher energy
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Energy
Colliding beamStationary target
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Problem
At LHC there are two colliding beams of 7 TeV If we consider a fixed target experiment how much
must be the energy of the moving beam to achieve the same energy in the center of mass?
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Magnetic and electric rigidity
B orthogonal to the particle trajectory
y
x
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Only magnetic field to bend the beam
Electron 1 GeV moving on y=0, B=1 T
Calculate the magnetic rigidity, the radius of curvature and the electric field needed to have the same radius of curvature
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Energy scale
“Starting from the 1930s, the energy has increased-- by about a factor of 10 every six to eight years… this spectacular achievement has resulted from a succession of technologies rather than from construction of bigger and better machines of a given type.” W. K. H. Panofsky, 1997.
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Accelerator history
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Particle accelerators
The Electrostatic Accelerators
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References
K. Wille “The Physics of Particle Accelerator”, Oxford University press pag 1-29
H. Wiedeman “Particle accelerator physics” volume 1, chapter 3
Just for your knowledge:
A. Sessler, E. Wilson, “ENGINES OF DISCOVERY”, World Scientific
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Principle of operation
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Current in electrostatic accelerators
Ohmic: proportional to voltage
Residual ion current: saturates rapidly (also beam)
Corona: negligible for small voltages
Current grows exponentially for high voltages causing spark discharge and voltage breakdown
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Paschen’s law
When the pressure increases, the collision probability increases, but the path between two collisions decreases, so also the energy transferred to an electron is decreased.
When the pressure is very low, the path between two collision is quite large, but the probability of a collision is relatively smaller.
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Cockroft Walton
Cockroft and Walton were able to accelerate protons to hundreds of keV.
In 1932 they bombarded Lithium with 700 keV protons and transmuted it into Helium and other elements.
This was the first time that a particle accelerator had been use to trigger a nuclear reaction.
Cockroft and Walton were awarded the Nobel prize in 1951.
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Voltage Duplicator
During the first quarter cycle the diode D1 is in conduction and the capacitor C1 is charging
During the second quarter cycle the C1 is already charged and nothing changes
During the third quarter cycle the diode D2 is in conduction and the capacitor C2 is charging
During the fourth quarter cycle the C2 is already charged and nothing changes
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Cockroft Walton @LNF
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Cockcroft Walton @ FERMILAB
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Van de Graaff
In a Van de Graaff generator charges are mechanically carried by a conveyor belt from a low potential source to a high potential collector.
Van de Graaff generator can reach several MV and are still used in DC accelerators
~2MV in air Up to 20+ MV in SF6!
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Using Van de Graaff
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Public science in the ‘30s
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Pigeon droppings
Under normal operation, because the electrodes were very smooth and almost perfect spheres, Van de Graf generators did not normally spark.
However, the installation at Round Hill (MIT) was in an open-air hanger, frequented by pigeons, and here we see the effect of pigeon droppings.
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Tandem
Reverse ion charge state in middle of Van de Graaffallows over twice the energy gain
The stripper is usually a gas Source is at ground
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Example
Br ion in a Tandem with V0 = 20 MV.
Br ( A = 79 ) charge Z = -1. The beam is accelerated to 20 MeV From the stripper, Ar (density l ≈ 1μg/cm2 ), the beam comes
out with a spectrum of charge with a maximum around Z+≈ 7, and it arrives to Z+ ≈ 10.
Filtering the Z+= 10 ions, these are again accelerated to the energy
E= (1 + Z ) qVo = 220 MeV ( 220/79 = 2.8 MeV/nucleon = 2.8 MeV/A).
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Atomic Mass Spectroscopy
Resolve 1 atom of 14C over 1015 of other Carbon atoms!
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Dating old documents
AMS was used to date ashes found in Newfoundland in a European-type settlement. These ashes were dated back to the XIth century.
A Viking map featuring Newfoundland was shown to be older than Columbus’ trip to America. AMS has contributed to establish that North America was visited by Vikings well before other European nations
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Limits of electrostatics accelerators
The maximum achievable voltage is limited by discharge
A further disadvantage of accelerating particles with high voltages is that either the source of the particles or the measuring instruments (or even both) have to be at high voltage, which makes any operation rather awkward and even dangerous.
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Advantages of Electrostatic Machines
Voltage may be very precisely controlled allows a detailed study of nuclear reactions and in particular narrow resonances in energy
Another interesting application is in the extensive study of the reactions that take place in stars, rather low energy by nuclear physics standards, and therefore requiring exacting work. In 1983 a Nobel Prize was awarded to William Fowler, of Caltech, for his “theoretical and experimental studies of the nuclear reactions of importance in the formation of the chemical elements in the universe”
Experimental work that was all carried out on electrostatic machines.