Introduction to radiation physics
José - Luis Gutiérrez Villanueva
Radonova Laboratories AB, Uppsala - Sweden Overview Introduction Radioactivity: fundamentals Radiation theory
Introduction
Radioactivity: fundamentals
Radiation theory
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Presentation
José Luis Gutiérrez–Villanueva
j PhD in Physics (U. Valladolid, Spain) j Currently working as specialist radon measurement advisor at Radonova Laboratories AB (Sweden) j Secretary of the Executive Committee and founding member of ERA (European Radon Association)
For any questions or comments please contact me at: [email protected]
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory
Introduction
Radioactivity: fundamentals
Radiation theory
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . .
I X- rays
I Some materials emit radiation
I Wow ! we can penetrate our body
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . .
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . .
I Photographic plates can get dark in the presence of material called Uranium I It must a property of the matter itself I Such a material emits a type of radiation
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . . MARIE SKLODOWSKA and PIERRE CURIE
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . .
A wonderful marriage
I Marie: a physicist and mathematician but . . . a Polish Woman
I Pierre: professor of Physics in Paris
I Studies on pitchblende
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . .
Their work with pitchblende
I They began separating elements and reducing sample’s size
I They observe an increase on the intensity of emitted radiation
I They discovered Polonium in 1898
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 I . . . the Radium
I It is necessary to determine its chemical and physical properties
I Very poor materials and infraestructures to do the task I Laboratory: a simple shed I From pitchblende to radium: years and years of hard work 3 I 10 kg pitchblende =⇒ few grams of radium
Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . .
Their work with pitchblende
I After separation of Plonium . . . emitted radiation increases more and more
I It must be another element different from Uranium and different from Radium. This element emits radiation too.
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 I Very poor materials and infraestructures to do the task I Laboratory: a simple shed I From pitchblende to radium: years and years of hard work 3 I 10 kg pitchblende =⇒ few grams of radium
Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . .
Their work with pitchblende
I After separation of Plonium . . . emitted radiation increases more and more
I It must be another element different from Uranium and different from Radium. This element emits radiation too.
I . . . the Radium
I It is necessary to determine its chemical and physical properties
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 3 I 10 kg pitchblende =⇒ few grams of radium
Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . .
Their work with pitchblende
I After separation of Plonium . . . emitted radiation increases more and more
I It must be another element different from Uranium and different from Radium. This element emits radiation too.
I . . . the Radium
I It is necessary to determine its chemical and physical properties
I Very poor materials and infraestructures to do the task I Laboratory: a simple shed I From pitchblende to radium: years and years of hard work
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . .
Their work with pitchblende
I After separation of Plonium . . . emitted radiation increases more and more
I It must be another element different from Uranium and different from Radium. This element emits radiation too.
I . . . the Radium
I It is necessary to determine its chemical and physical properties
I Very poor materials and infraestructures to do the task I Laboratory: a simple shed I From pitchblende to radium: years and years of hard work 3 I 10 kg pitchblende =⇒ few grams of radium
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . .
Milestones
I 1903: Nobel prize on Physics: Marie, Pierre and Becquerel (15000 $ !!!)
I 1906: Pierre Curie passed away in a street accident in Paris on 19 April 1906 (Crossing the busy Rue Dauphine in the rain at the Quai de Conti, he slipped and fell under a heavy horse-drawn cart. He died instantly when one of the wheels ran over his head, fracturing his skull (Wikipedia))
I 1911: Nobel prize on Chemistry: Marie Curie
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . .
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . .
Other names to bear in mind
I Ernest Rutherford I Friedrich Ernst Dorn (1871 – 1937): (1848 – 1916): see concept of later . . .
radioactive half-life; I Rolf Maximilian model of the atom Sievert (1896 – I Sir James Chadwick 1966): biological (1891 – 1974): the effects of radiation
discovery of the I Max Karl Ernst neutron Ludwig Planck I Frederick Soddy (1858 – 1947): (1877 – 1956): quantum theory radioactivity and nuclear reactions
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . .
Credit
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . .
Credit
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Once upon a time . . .
Credit
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory
Introduction
Radioactivity: fundamentals
Radiation theory
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 I Energies: keV and MeV
I Decay modes: alpha, beta and gamma
Overview Introduction Radioactivity: fundamentals Radiation theory Ionizing radiation
Radiation with enough energy to detach electrons from atoms or molecules, thus ionizing them
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Ionizing radiation
Radiation with enough energy to detach electrons from atoms or molecules, thus ionizing them
I Energies: keV and MeV
I Decay modes: alpha, beta and gamma
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 222 220 219 radon: 86 Rn; 86 Rn; 86 Rn
Overview Introduction Radioactivity: fundamentals Radiation theory Numbers and names
Symbol Definition Fingerprint Z (atomic num- The atomic number of an ATOM ber) atom is the number of protons it contains A (mass number; Total number of protons ISOTOPE atomic mass num- and neutrons (together ber or nucleon known as nucleons) in an number) atomic nucleus
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Numbers and names
Symbol Definition Fingerprint Z (atomic num- The atomic number of an ATOM ber) atom is the number of protons it contains A (mass number; Total number of protons ISOTOPE atomic mass num- and neutrons (together ber or nucleon known as nucleons) in an number) atomic nucleus
222 220 219 radon: 86 Rn; 86 Rn; 86 Rn
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Decay modes
4+ Alpha decay: Emission of an alpha particle (2 He) by a nucleus
Characteristics of the alpha decay mode
I High enery (MeV)
I Heavy particles: they can be stopped in some cm
I Elements heavy nucleus 222 238 210 I Examples: 86 Rn, 92 U, 84 Po
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Decay modes
Example of alpha spectrum
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Decay modes
Beta decay: Emission of beta particle (positive or negative) by a nucleus. Also electron capture by a nucleus.
Characteristics of the beta decay mode
I Less energy than alpha emission
I Longer distance before stopping
I Continuous spectrum of energy 3 90 I Examples: 1H, 38Sr
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Decay modes Example of beta spectrum
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Decay modes
Gamma decay: Photon’s emission by a nucleus when reaching steady state of energy.
Characteristics of the gamma decay mode
I Photons with different energies
I X Rays
I Gamma Rays (with different energies)
I Gamma rays = Nucleus
I X Rays = Atomic crust 99 60 I Examples: 43Tc, 27Co
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Decay modes Example of gamma spectrum
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Penetration power
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Definitions
I Activity (A): Number of disintegrations per second
I Half life (T1/2): Neccesary time for an isotope to decrease its nucleus by half (s)
I Decay constant (λ): Probability of disintegration by time (s−1)
I Decay chain: chained series of transformations (4 Natural decay chains)
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Units
I Becquerel (Bq) : unit of activity in the International System of Units: 1Bq = 1 DPS (disintegration / second) 10 I Curie(Ci):Old unit of activity: 1Ci=3.7 · 10 Bq
I Concentration : Bq/kg, Bq/l, Bq/m3
I Sievert (Sv) : Unit for equivalent dose
I Working Level Month (WLM): Occupational exposure (1 WLM is approximately equivalent to an exposure of 150 Bq m−3 in a year)
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Exponential’s decay law
−λ·t A = A0e
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Half-lives
Isotope Half life 238U 4.5 · 109 y 14C 5730 y 3H 12.4 y 131I 8.03 d 222Rn 3.8 d 99Tc 6 h 219Rn 3.96 s
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Natural decay series
Series Start Half life (y) Final product Thorium 232Th 1.41 · 1010 208Pb Neptunium 237Np 2.14 · 106 209Pb Uranium 238U 4.51 · 109 206Pb Actinium 235U 7.18 · 108 207Pb
Earth’s age: 4.65 · 109
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Natural decay series Uranium
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory
THANKS TO: Statistical methods in Radiation Physics. James E. Turner, Darryl J. Downing, James S. Bogard. Wiley-VCH.
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory
Classical Physics - Determinism The principle of Physics: to discover laws and regularities that provide a quantitative description of nature as verified by obser- vation Outcome: the ability to make valid predictions of future condi- tions from a knowledge of the present state of a system Example: Newton’s classical laws of motion
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory
Modern Physics - Probabilities The problem: the classical Physics fails on the small scale of atoms Outcome: atoms and radiation are governed by definite, but statistical, laws of quantum Physics Given the present state of an atomic system we can predict its future evolution . . . only in statistical terms Example: Probability that a radioactive sample will undergo a certain number of disintegrations in the next minute.
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory
Questioning the existing Physics: end of XIX century Ultraviolet catastrophe: incorrect prediction of the distribution of wavelengths in the spectrum of EM radiation emitted from hot bodies such as the sun Speed of light: sensitive measurements of this parameter in dif- ferent directions on earth revealed no difference
What to do ???
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory
Ultraviolet catastrophe: incorrect prediction of the distribution of wavelengths in the spectrum of EM radiationemitted from hot bodies such as the sun
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Speed of light: sensitive measurements of this parameter in different directions on earth revealed no difference
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Semiclassical atomic theory
Some events
I X-rays (Roentgen 1895)
I Radioactivity (Becquerel 1896) − I Charge-to-mass ratio e (1897) − I Charge e (Milikan 1909)
I Radioactive materials (Curie end 1800’s - 1910)
I Discovery of atomic nucleus (Rutherford 1911)
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Semiclassical atomic theory
New problems arrive with the model of atom after Rutherford’s finding: according to Maxwell’s equations, accelerated electric charges emit ebergy. Therefore the electron should spiral into the nucleus Nucleus cannot be stable
But they are !!!
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Not so easy, not so fast: what happens when we deal with atoms with more than one electron?
Overview Introduction Radioactivity: fundamentals Radiation theory Semiclassical atomic theory
Bohr in 1913 solved the problem: the electron can occupy only some circular orbits around the nucleus (proton). Its angular momentum is quantized. The electron emits radiation (photon) when moves from one orbit to another
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Semiclassical atomic theory
Bohr in 1913 solved the problem: the electron can occupy only some circular orbits around the nucleus (proton). Its angular momentum is quantized. The electron emits radiation (photon) when moves from one orbit to another Not so easy, not so fast: what happens when we deal with atoms with more than one electron?
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Semiclassical atomic theory
Einstein 1905: photoelectric effect
E hν p = = c c de Broglie 1924: postulate relationship wavelength and momentum to other fundamental particles, not only photons. Duality wave-particle was introduced
REVOLUTION
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Quantum mechanics and uncertainty principle
Heisenberg 1924:matrix theory of quantum mechanics Schödinger 1924: wave equation Both were demostrated to be equivalent formulations: quantum mechanics was born !! Heisenberg’s uncertainty principle:
∆x∆px > }
∆E∆t > }
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 But . . . how to explain the emission of an electron in beta decay??? Quantum mechanics explanation: beta particle and antineutrino are created. Both particles are ejected from the nucleus tha recoils. Shared energy: beta particle, antineutrino and recoil. This energy is equal to loss of mass (E = mc2). Such share of energy is continuous as the beta spectrum is.
Overview Introduction Radioactivity: fundamentals Radiation theory Radioactive Decay
Before the discovery of the neutron (Chadwick 1932): atomic nucleus must be made up of elementary subatomic particles (protons and electrons). This turns out into problems of angular momentum and kinetic energy of electron in the nucleus.
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Radioactive Decay
Before the discovery of the neutron (Chadwick 1932): atomic nucleus must be made up of elementary subatomic particles (protons and electrons). This turns out into problems of angular momentum and kinetic energy of electron in the nucleus. But . . . how to explain the emission of an electron in beta decay??? Quantum mechanics explanation: beta particle and antineutrino are created. Both particles are ejected from the nucleus tha recoils. Shared energy: beta particle, antineutrino and recoil. This energy is equal to loss of mass (E = mc2). Such share of energy is continuous as the beta spectrum is.
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Radioactive Decay
The radioactive decay of atoms and the accompanying emission of radiation are described in detail by QM The radioactive decay occurs spontaneously and randomly without influence of external factors
God does not play dice (A. Einstein)
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Radioactive Decay
Radioactive disintegration - exponential decay We must remember basic equations in radioactivity:
−λt dN = −λNdt ⇒ N = N0 e
A = λN
−λt A = A0 e
ln 2 T = 1/2 λ
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Radioactive Decay
Number of disintegrations - The Binomial distribution Let’s think in a large number of identical sources of a pure rad- dionuclide, each with N atoms. We observe the number of disin- tegrations occurring at time t, starting at t=0. We will obtain a distribution for the number of k atoms that decay with possible values k=0,1,2 . . . Each source: undergoing process in which, during time t, each individual atom represents a single one of N trials to success (de- cay) or failure (non-decay). The outcome of each trial is binary. All atoms are identical and indepedent: each trial has the same probability and this is independent of another trials.
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory Radioactive Decay
Number of disintegrations - The Binomial distribution
I Process: the radioactive decay is a Bernoulli process
I Binomial distribution: the resulting number of disintegrations from source to source Hence, the probability for k disintegrations in a time t from a source consisting initially of N identical radioactive atoms is:
N Pr(k) = pk qN−k k where
q = e−λt and p = 1 − q = 1 − e−λt
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019 Overview Introduction Radioactivity: fundamentals Radiation theory
J.L. Gutiérrez–Villanueva IAEA regional workshop Vilnius 2019