> From the infinitely small to the
infinitely large
> INTRODUCTION
THE COLLECTION
1 > The atom
2 > Radioactivity
3 > Radiation and man
4 > Energy
5 > Nuclear energy: fusion and fission
6 > How a nuclear reactor works
7 > The nuclear fuel cycle
8 > Microelectronics
9 > The laser: a concentrate of light
10 > Medical imaging
11 > Nuclear astrophysics
12 > Hydrogen
FROM RESEARCH
TO INDUSTRY
1
> The atom
AT THE HEART OF MATTER: ATOMS
CHEMICAL ELEMENTS
AND ISOTOPES
THE FOUR FUNDAMENTAL
INTERACTIONS
NUCLEAR PHYSICS
© Commissariat à l’Énergie Atomique et aux Energies Alternatives, 2005
Communication Division
Bâtiment Siège - 91191 Gif-sur-Yvette cedex
www.cea.fr
ISSN 1637-5408.
From the infinitely small to the infinitely large
1 > The atom
From the infinitely small to the infinitely large
1 > The atom
2
> CONTENTS
> INTRODUCTION
Every atom consists of
a nucleus surrounded
by a cloud of electrons.
CHEMICAL ELEMENTS
AND ISOTOPES
Chemical elements
Isotopes
The periodic table
THE FOUR FUNDAMENTAL
INTERACTIONS
Strong interaction
Electromagnetic interaction
Weak interaction
Gravitation
NUCLEAR PHYSICS
A brief description
of the nucleus
Nuclear ‘microsurgery’
The nuclear furnace
T
4
5
5
6
6
8
9
9
11
12
13
13
14
14
15
introduction
he concept of the atom was due to philosophers such as Leucippus and Democritus,
who, in an attempt to answer questions about
the beginning and end of the cosmos and the
sameness and difference of material things,
found a common denominator for all things,
for the whole Universe: the atom.
As the centuries passed, this desire to understand the origin of the world led physicists
to consider the atom as a physical object.
This “small unit of matter” enabled great
progress to be made in understanding our
Universe, and it remains at the center of much
research today. But it has not yet yielded all
its secrets.
HISTORY
© Palais de la découverte/Ph. C. Greutz
AT THE HEART OF MATTER:
ATOMS
The composition of atoms
The size of an atom
and its nucleus
The mass of an atom
The electrical charge
of an atom
© PhotoDisc
The atom
© Roger-Viollet
From left to right:
Joseph John
Thomson, Ernest
Rutherford and
James Chadwick.
• In the fifth century BC, Leucippus, then Democritus,
named this everlasting, unlimited “small unit of
matter” in constant rapid movement, the “atom”
(from the Greek “atomos” meaning “cannot be cut”).
Electrostatic shower.
• More than 2,500 years passed before anyone
expanded upon this understanding. Then, in 1897,
Joseph John Thomson discovered one of the atom’s
components, the electron. By 1904, he believed
that atoms were spheres filled with an electrically
positive substance and stuffed with negative
electrons.
• In 1911, the English scientist Ernest Rutherford saw
that particles projected on to matter passed through
it as if it were a vacuum, apart from a very few that
altered their course or bounced back like bullets
fired into a big wide hedge containing a few small
hidden steel balls. He had discovered the nucleus
of the atom, in which almost all the atom’s mass
is concentrated in a volume one hundred thousand
times smaller than the atom itself.
16
16
19
• The next discovery to be made was that the nucleus’
positive electrical charge is carried by several
corpuscules, known as protons. And in 1932,
James Chadwick discovered the neutron, the neutral
constituent of the nucleus. On its own, it disintegrates
into a proton and an electron, but when inside
the atom’s nucleus, it is stable.
• In 1969, physicists bombarded nuclei with a beam of
particles (electrons) traveling fast enough to penetrate
the core of nucleons. And the Rutherford story
was repeated within the nucleon, as some of these
electrons rebounded in an apparently bizarre way.
This could only mean they were bouncing against even
smaller corpuscules. And so, quarks were discovered.
There are three quarks inside every nucleon.
• One day perhaps we’ll discover even smaller
particles inside quarks! We would need even more
powerful particle accelerators though.
The smaller we want to see, the larger
our “microscope” must be.
Designed and produced by Spécifique - Cover photo by © PhotoDisc - Illustrations by YUVANOE - Printed by Imprimerie de Montligeon - 04/2005
From the infinitely small to the infinitely large
1 > The atom
From the infinitely small to the infinitely large
1 > The atom
3
4
> AT THE HEART OF MATTER: ATOMS
AN ATOM IS MADE UP OF A NUCLEUS
OF PROTONS AND NEUTRONS, AND A CLOUD
OF ELECTRONS.
At the heart
of matter: atoms
THE COMPOSITION OF ATOMS
The planets, air, water, stones and living
organisms, in fact all bodies within nature
are made up of atoms or atom assemblies
(molecules, etc.). Contrary to what its etymology suggests,
Assemblies of several atoms held
together by chemical bonds.
the atom is not
indivisible. So what’s in it?
An atom consists of:
• a central nucleus, which is a collection of
protons and neutrons. Protons and neutrons
are the nucleons (from the Greek word
“nucleus”);
• a peripheral cloud of electrons, which orbit
around the nucleus at amazing speeds. It’s
impossible really to predict their trajectories;
we can only, using mathematical formulae,
predict the areas in which they are most likely
to be found inside the cloud they make around
the nucleus.
There are lots of different atoms, but they
are all made from protons, neutrons and
electrons.
10-15 meters, which is nearly 100,000 times
smaller than the atom with its electron cloud.
REPRESENTATION
OF THE ELECTRON CLOUD
IN A LITHIUM ATOM
The lithium atom shown has three protons,
four neutrons and three electrons. It is not possible
to give the exact position of the three electrons
in the lithium atom’s electron cloud.
In this representation, the electrons are most likely
to be in the darker areas. This image is the result
of mathematical formulae.
Atomic nucleus
THE SIZE OF AN ATOM
AND ITS NUCLEUS
Electron cloud
© PhotoDisc
The atom’s spherical electron cloud is about
10-10 meters in diameter. This is truly miniscule. To make a centimeter, you would need
to line up 100 million atoms.
The nucleus is much smaller still. It occupies
a sphere with an average diameter of
From the infinitely small to the infinitely large
1 > The atom
From the infinitely small to the infinitely large
1 > The atom
5
6
> AT THE HEART OF MATTER: ATOMS
7
> AT THE HEART OF MATTER: ATOMS
“The space between the nucleus
and the electron cloud is empty.”
approximate mass of an atom. However the
result of the calculation is only an estimate (see
the Nuclear energy: fusion and fission booklet).
THE ELECTRICAL CHARGE
OF AN ATOM
© PhotoDisc
© PhotoAlto
© PhotoDisc
Of the three parts that make up an atom, only
the neutron does not have an electrical charge:
it is neutral, hence its name. Protons are
positively charged and electrons negatively
charged. An atom in its normal state has as
many protons as electrons. It is therefore electrically neutral. However, under certain conditions (e.g. chemical reactions), atoms can gain
or lose one or more electrons and can therefore
become positively or negatively charged. They
are then called ions.
© MNHN
© PhotoDisc
Mass is not distributed evenly throughout an
atom. The protons and neutrons have about the
same mass, but they are approximately 2,000
times heavier than an electron, so almost all
the atom’s mass is concentrated in the nucleus,
and the matter making up a nucleus is a million
billion times denser than ordinary matter. If all
the Earth’s nuclei were put together so they
were touching, the planet would be little more
than a hundred meters in diameter and a grain
of sand would weigh more than a metric ton.
To estimate the mass of a nucleus, you simply
have to know how many nucleons it has (also
known as its mass number). Once you know
that the mass of a nucleon is approximately
1.67x10 - 2 7 kg, it’s easy to calculate the
© PhotoDisc
THE MASS OF AN ATOM
In nature, all bodies are made up of atoms or atom assemblies (molecules).
From the infinitely small to the infinitely large
1 > The atom
From the infinitely small to the infinitely large
1 > The atom
8
> CHEMICAL ELEMENTS AND ISOTOPES
ATOMS FALL INTO DIFFERENT
CATEGORIES ACCORDING TO THE NUMBER
OF ATOMS THEY HAVE
Chemical elements
and isotopes
The atom
An aluminum atom (Al)
14 neutrons
An aluminum nucleus
13 protons
13 electrons
CHEMICAL ELEMENTS
© PhotoDisc
A chemical element is a set of atoms each with
the same number of protons. It is denoted by a
symbol of one or two letters (e.g. 1H for hydrogen, which only has one proton, or 26Fe for iron,
which has 26 protons).
The atoms naturally present on the Earth
belong to 90 chemical elements with between
1 and 92 protons. The chemical elements
technetium (Tc) with 43 protons and promethium (Pm) with 61 protons, do not exist in
the natural state. They can, however, be created
From the infinitely small to the infinitely large
1 > The atom
From the infinitely small to the infinitely large
artificially, as can other chemical elements with
more than 92 protons, such as plutonium (Pu)
for example, which has 94 protons.
ISOTOPES
Nuclei do not consist only of protons. They
also contain neutrons. Atoms of a chemical
element with a different number of neutrons
are isotopes of that element. For example:
• All the isotopes of hydrogen have one proton
and zero, one or two neutrons. They are light
hydrogen (often referred to simply as hydrogen
1 > The atom
9
10
> CHEMICAL ELEMENTS AND ISOTOPES
> CHEMICAL ELEMENTS AND ISOTOPES
Mendeleev’s periodic table of elements
“Isotopes are rather “sibling”
atoms, with the same chemical
properties but different numbers
of neutrons.”
2A ALKALINE EARTH METALS
4A
1
1
Isotopes
2
3
Tritium 3H or T
6.941
6
1 electron
Nucleus: {1 proton }
Nucleus:
1 electron
1 proton
1 neutron
{
because it is the most common form), heavy
hydrogen or deuterium, and tritium (see
diagram below).
• All the isotopes of carbon have six protons.
The most common ones have six, seven, or eight
neutrons. An atom is referred to using the name
of its chemical element followed by its total
number of nucleons: carbon-12, carbon-13 and
carbon-14.
The chemical properties of an atom depend
solely on the number and arrangement of the
electrons in its electron cloud; all isotopes of
the same element have the same chemical
properties. However, the slight difference in
the mass of their nucleus means that their
physical properties are very slightly different.
From the infinitely small to the infinitely large
}
1 electron
1 proton
Nucleus:
2 neutrons
{
}
9.0122
12
Na
Mg
20
K
Ca
39.0983 40.078
Rb
38
85.468
Sr
87.62
Sc
22
44.956
39
Y
Ti
47.88
40
88.906
13
Zr
91.224
23
24
V
50.942
41
42
Nb
Cr
25
26
Mn
Fe
27
Co
28
51.996 54.9309 55.847 58.9332
92.906
Mo
43
44
Tc
Ru
45
Rh
29
46
Cu
63.546
47
Pd
Ag
30
Zn
31
65.39
48
Cd
87
Fr
88
(223)
Ra
226.025
ACTINIDES
49
It is referred to using the name of its
chemical element followed by the total
number of nucleons it has (mass number).
For example, oxygen-16, iron-59.
The chemical element’s name tells us
the number of protons it has.
By subtracting the number of protons from
the number of nucleons, we can find out
how many neutrons it has.
1 > The atom
Si
71
89
to
103
Ge
72.61
50
In
72
Hf
73
74
Ta
W
75
76
Re
178.49 180.948 183.85 186.207
104
Rf
105
Db
106
(261.11) 262.11
91
90
92
89
Pa
Ac Th
U
Sg
263.12
Os
190.2
107
108
Hs
Bh
264.12
265.13
77
Ir
192.22
109
Mt
268
78
79
Pt
195.08
Au
Hg
81
82
Tl
196.967 200.59 204.383
111
110
80
Uun Uuv
269
272
112
Sn
277
103
101
97
93
95
99
96
94
98
102
100
Np Pu Am Cm Bk Cf
Es Fm Md No
Lr
38 231.036 38.029 237.048 (244) (243)
227.028 232.0
2
(247) (247)
(251) (252)
(257)
(258)
(259)
Pb
207.2
KEY
Uub
8
9
O
F
10
Ne
15
P
16
17
S
33
As
34
51
Sb
Se
35
78.96
74.9216
52
Br
79.904
53
Te
Cl
18
Ar
35.4527 39.948
I
36
Kr
83.80
54
Xe
127.60 126.905 131.29
83
Bi
208.980
84
Po
85
(209)
Atomic number
Symbol
Atomic mass
At
86
(210)
Rn
(222)
1
H
1.00794
The figures between brackets
indicate the mass number
of the most stable isotope.
(260)
According to Handbook of Chemistry and Physics,
th
74 Ed. 1993, CRC Press
and Pure and Applied Chemistry, 1997, 69, 2471
ATOM NAMES
An atom is characterized by the number of
protons (identical to the number of electrons)
and the number of neutrons it has.
N
67
65
69
71
61
63
59
64
70
62
66
60
68
Ho
Lu
Tb
Pr Nd Pm Sm Eu
Er Tm Yb
Dy
Gd
1
1
58
57
La
Ce
to
32
Ga
69.723
57
Ba
7
101.07 102.906 106.42 107.868 112.411 114.82 118.710 121.75
(98)
95.94
Ni
58.69
55
56
C
12.011 14.0067 15.9994 18.9984 20.1797
14
Al
15 40.908 44.24 (145) 50.36 51.965 57.25 158.925 62.50 164.930 67.26 168.934 73.04 174.967
1
1
1
1
1
1
138.906 140.1
Cs
6
B
10.811
LANTHANIDES
132.905 137.327
7
5
26.9815 28.0855 30.9736 32.066
21
He
4.00206
7A MANGANESE family
NOBLE METALS 1B
8A
8B
8C
Period 4: MAGNETIC METALS
Period 5: PALLADIUM METALS
Period 6: PLATINUM METALS
Be
2
ZINC family 2B
22.9898 24.3050
37
5
4
Li
4B
TRIVALENT METALS 3B
6A CHROMIUM family
1.00794
19
4
TETRAVALENT METALS AND METALLOIDS
5A VANADIUM family
H
11
Deuterium 2H or D
TRIVALENT METALLOIDS 5B
3A RARE EARTHS
Period
3
Hydrogen 1H
MONOVALENT HALOGEN METALLOIDS 7B NOBLE
GASES
BIVALENT METALLOIDS 6B
1A ALKALI METALS
Al
C
Cd
Carbon
Cadmium
Hg
In
Pb
Mercury
Indium
Aluminum
From the infinitely small to the infinitely large
Co
Cr
Cobalt
Si
Lead
Chromium
Tl
Silicon
Ge
Germanium
W
Thallium
Tungsten
1 > The atom
11
12
> THE FOUR FUNDAMENTAL INTERACTIONS
IN NATURE, ALL OBJECTS ACT
UPON EACH OTHER. WE SAY
THAT THEY INTERACT.
The four
fundamental
interactions
I
n nature, objects are subject to all kinds of
forces exercised at a distance. So for example,
two masses attract each other and two electrical charges attract or repel each other
depending on their sign. Objects act upon each
other. They interact. There are four fundamental
types of interactive force (or simply, interactions), governed by the nature of the objects:
strong interaction, electromagnetic interaction,
weak interaction and gravitation.
STRONG INTERACTION
Strong interaction, or strong nuclear force,
keeps the nucleus together by making the
nucleons attract each other strongly. It only
operates over very short distances of several
nucleus diameters. Over an equal distance, it
is 100 to 1,000 times more intense than
electromagnetic interaction.
“A compass is
disturbed by lightning
during a storm: this is
one manifestation
of magnetic force,
which comes from
the movement
of electrical charges.”
infinity, but it is four times weaker at twice the
distance (inverse-square law). It underpins the
chemical properties of atoms.
Electric force governs phenomena such as lightning
and is involved in the electromagnetic interaction.
© Palais de la découverte/Ph. C. Greutz
Electromagnetic interaction manifests itself in
two forms, electric force and magnetic force.
The first governs electrical phenomena such as
lightning and hair standing on end when there
is electricity in the air, and the second,
magnetic phenomena such as compasses and
electromagnets. Magnetic force is an effect of
the movement of electrical charges, which is
why a compass is disturbed by lightning during a storm. This interaction makes two electric charges of the same sign (e.g. two protons)
repel, and two charges of opposite signs (an
electron and a nucleus) attract. It extends to
From the infinitely small to the infinitely large
1 > The atom
From the infinitely small to the infinitely large
© PhotoDisc
ELECTROMAGNETIC INTERACTION
1 > The atom
13
14
15
> THE FOUR FUNDAMENTAL INTERACTIONS
NUCLEAR PHYSICS IS THE STUDY OF
ATOMIC NUCLEI AND THEIR COMPONENTS.
“Gravitation varies
with distance. When
we fall from a height,
we hurt ourselves!”
Nuclear physics
WEAK INTERACTION
Weak interaction, or weak nuclear force, is
responsible for certain radioactive phenomena
(e.g. beta radioactivity). Its range is extremely
short – just a few hundredths of the size of a
nucleon – but it governs the thermonuclear
reactions that enable the Sun and stars to produce energy. It is approximately 100,000 times
weaker than strong interaction.
GRAVITATION
© CEA/GANIL
© PhotoDisc
Gravitation, which is responsible for the attraction of masses, explains weight (the pull of gravity) and the movement of the heavenly bodies.
It varies with distance according to the same
law as electromagnetic force. It is the weakest
force of the four by far, being 10-40 times
weaker than electromagnetic force! However,
it is the one we experience most: when we fall
from a height, we hurt ourselves! This is
because the mass attracting us – the Earth –
is gigantic. But although we may sometimes
break a leg, we will never break an atom and
still less a nucleus.
Gravitation, which is weak compared with the other forces,
is nevertheless the one we experience most.
From the infinitely small to the infinitely large
1 > The atom
From the infinitely small to the infinitely large
1 > The atom
> NUCLEAR PHYSICS
> NUCLEAR PHYSICS
“In the core of an atom, protons
and neutrons are “dancing” at more than
30,000 km/s. However, they are held
together by nuclear force.”
Characteristics of elementary particles
ELECTRON
ATOM
PROTON
QUARKS
NUCLEUS
NEUTRON
A BRIEF DESCRIPTION
OF THE NUCLEUS
From the infinitely small to the infinitely large
FIRST FAMILY
SECOND FAMILY
FERMIONS
Ordinary matter
is made up of
particles in this
group. For the
most part, these
particles existed
just after the
Big Bang. Today
they are only
found in cosmic
rays and near
accelerators.
THIRD FAMILY
So an atom is rather like a miniature solar
system, in which mini planets (electrons) are
revolving around a mini sun (the nucleus).
Nuclear physics is the study of atomic nuclei
and the enormous force – strong interaction –
that binds together their components, the
nucleons (protons and neutrons).
The nucleus is an extremely dense, complex
and tiny object. Like a Russian doll that contains more dolls getting smaller and smaller,
the nucleus contains nucleons, each containing three quarks. There are two sorts of
nucleon: protons, which are positively
charged, and neutrons, which are neutral.
In this minuscule space, not only are the
protons repelling each other very strongly
because they have the same electrical
charge, but the protons and neutrons are
dancing a dizzying ballet at more than
30,000 km/s (more than a tenth of the
speed of light, i.e. around the Earth in
1.34 seconds)! However the nucleus does
not shatter into a shower of nucleons, but
remains bound together. Within it, a colossal
force of attraction is at work between the
nucleons, a force much greater than the
electric force keeping the protons apart.
This nuclear force or strong interaction,
which maintains the cohesion of the
nucleus, is the most powerful of the four
fundamental interactions or forces of
nature.
LEPTONS
Can move about freely.
Particle accelerator at CERN,
in Switzerland.
© CEA
16
QUARKS
Prisoners of larger particles; they are not
observed individually.
ELECTRON
Responsible for
electricity and chemical
reactions. It has
a charge of - 1.
ELECTRON NEUTRINO
It has no electrical
charge and interacts
very rarely with
the surrounding
environment.
DOWN (d)
It has an electrical
charge of –1/3.
Protons contain one
and neutrons two.
UP (u)
It has an electrical
charge of +2/3.
Protons contain two
and neutrons one.
MUON
A companion to the
electron but with
greater mass.
MUON NEUTRINO
Properties similar
to those of the electron
neutrino.
STRANGE (s)
A heavier companion
to Down.
CHARM (c)
A heavier companion
to Up.
TAU
Even greater mass.
TAU NEUTRINO
Properties similar to
those of the electron
neutrino.
BEAUTY (b)
Even greater mass.
TOP (t)
PHOTON
Elementary grain of
light, which mediates
electromagnetic force.
GLUON
Mediates the
strong interaction
between quarks.
NUCLEAR “MICROSURGERY”
This is the study of the nucleus as a collection of nucleons that move and attract, the
detailed mechanisms of their attraction and
the influence of quarks on their properties and
behavior. Nuclei have to be probed with a kind
of microscalpel in proportion to their dimensions. An accelerated particle beam (see box
on page 18) is used to see what proportion of
the particles has been deflected and what
proportion absorbed. It is also used to see how
the nuclei react, e.g. by ejecting nucleons or
producing other particles. Some amazing things
1 > The atom
VECTOR
BOSONS
Fundamental
particles that
transmit the
forces of nature.
HIGGS BOSONS?
W-, W+, Z0
Mediators of the weak
interaction, responsible
for some forms of radioactive
disintegration.
GRAVITON
Assumed to be
the mediator
of gravitational force.
Responsible for breaking electroweak symmetry.
From the infinitely small to the infinitely large
1 > The atom
17
> NUCLEAR PHYSICS
> NUCLEAR PHYSICS
“For the study of atoms, some scientists
are going back in time by recreating extreme
conditions similar to those that existed in
the first moments of the Universe.”
© CEA/Gonin
© CEA/Dapnia
18
can be achieved in this way. It is possible to
see the difference in size between a proton on
its own and a proton in its nucleus, and to
measure the influence of the rotation of quarks
on the rotation of the nucleon that contains
them, i.e. to determine how three small
spinning tops turning perpetually in a sort of
HOW CAN WE “SEE” NUCLEI AND PARTICLES?
SPIRAL TAKES US FURTHER
In reality, we don’t actually see
nuclei. We can only determine
their size and shape by
bombarding them with
accelerated particle beams.
We will now look at how these
particles bounce off or are
absorbed and how the
nucleus reacts.
This process is not very different
from the way our vision works.
Objects reflect back to our eyes
the light used to illuminate them,
sometimes absorbing part of
this light.
We also see their size, color, etc.
Now, light is at the same time
a collection of light particles,
known as photons, and a vibration
or wave, like the swell at sea.
The more energy the wave is
carrying, the faster it vibrates,
or in other words, the closer
together its undulations. The
distance between two successive
peaks is known as the
wavelength. The shorter the
wavelength, the more energy
in the wave, and the more finely
From the infinitely small to the infinitely large
we can see. The wavelength of
visible light is between 0.4 and
0.8 micrometers (millionths of
a meter). That’s about the size
of a microbe. We can see this
size of object with an optical
microscope, but if we want to
see anything smaller, an optical
microscope is of no use. To see
atoms, we need an electron
microscope in which a beam of
accelerated electrons plays the
role of light, because it behaves
like a wave, but with a wavelength
in the region of a fraction of a
nanometer (billionth of a meter).
The electron microscope, whose
electron “wave’’ has
10,000 times more energy than
visible light, lets us see
approximately
the diameter of an atom
(i.e. 10,000 times smaller
than the diameter of a microbe).
To “see” a nucleus, our powers
of observation must be at least
100,000 times more precise
and that means we need a beam
with at least 100,000 times more
energy than that of the most
powerful electron microscope.
This is possible with particle
accelerators.
CERN in Geneva, in partnership
with CEA, will soon be home to
the Large Hadron Collider (LHC).
This particle accelerator, the
biggest in the world, will contain
400 quadrupole magnets, which
will focus proton beams to
produce collisions at an energy
of 14 TeV (14,000 billion
electronvolts).
One of the aims is to see
the Higgs boson.
Top left: a quadrupole magnet
for the LHC.
Top right: the SIMS analytical
microscope is used to determine
the location of radionuclides
emitting weak rays.
It operates on the principle of
a scanning electron microscope
and replaces the primary electron
beam with a beam of ions,
enabling analysis of the
elements in solid surfaces.
1 > The atom
Spiral is a facility based at Ganil (Grand
accélérateur national d’ions lourds, or French
large heavy ion accelerator) in Caen, and is used
to produce and accelerate light and mediumheavy nuclei, known as exotic nuclei, which
do not exist on Earth. Studying these is essential
in many fields of nuclear physics, but also
astrophysics, particularly for understanding
the formation of the nuclei of atoms within
stars and supernovae.
Although physicists already know how to
synthesize exotic nuclei in the laboratory, the
Spiral installation will enable them for the first
time to produce exotic nuclei in large quantities,
accelerate them, observe their collisions
with other nuclei and thereby understand
their structure. Compared with other existing
installations, Spiral also gives much greater
scope for expanding the range of exotic elements
produced and the energy range accessible.
glue and enclosed in a spinning top a thousand times bigger (yet itself minuscule) can
be partly responsible for its rotation.
THE NUCLEAR FURNACE
This is the ‘overall’ study of the nucleus as a
sample of the very dense nuclear matter the
properties of which we know so little about. To
find out more, we can study it in extreme
conditions like those that existed when the
Universe began. This is like winding back time.
The method involves projecting bursts of nuclei
onto one another, accelerated to speeds close
to the speed of light.
This creates shocks of an unbelievable violence.
The nuclei find themselves in extreme states
of temperature, pressure, deformation and
instability, and they fuse, form new nuclei, most
of which do not exist on Earth, split, and above
a certain temperature, explode, literally
evaporating in a shower of nucleons. This is a
fantastic gift for physicists, because this is the
temperature below which nuclei formed when
the primordial soup resulting from the Big Bang
cooled. Fifteen billion years later, they can
actually measure it.
In September 2001, Spiral produced its first beam
with an exotic nucleus: neon-18. By observing
the collisions of this beam with a solid hydrogen
target, it was possible using Spiral to discover
the structure of sodium-19, a nucleus that is
not known on Earth, in particular to understand
some of the thermonuclear reactions involved
in the creation of the elements in the Universe.
From the infinitely small to the infinitely large
1 > The atom
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