Nuclear Physics 722822

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Nuclear Physics 722/822

• Moskov Amarian
• Department of Physics
• Old Dominion University

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Introduction

• In this course I shall discuss nuclear and
  particle physics from phenomenological point of
  view.
• Research in nuclear physics is an integral part
  of the search for knowledge and understanding of
  the world in which we live. All matter is
  composed of a hierarchy of building blocks.
• Living creatures, as well as our inanimate
  surroundings, are made of molecules, which are in
  turn made of atoms, whose mass resides almost
  entirely in the nuclei.
• The nuclei are composed of protons and neutrons,
  which ultimately consist of quarks and gluons.

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• The science of nuclear physics concerns itself
  with the properties of nuclear matter.
• Such matter constitutes the massive centers of
  the atoms that account for 99.9 percent of the
  world we see about us.
• Nuclear matter is within the proton and neutron
  building blocks of these nuclei, and appears in
  bulk form in neutron stars and in the matter that
  arose in the Big Bang.
• Nuclear physicists study the structure and
  properties of such matter in its various forms,
  from the soup of quarks and gluons present at the
  birth of our universe to the nuclear reactions in
  our Sun that make life possible on Earth.

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Rutherford experiment

• From angular distribution of rescattered ?
  -particles Rutherford concluded existence of
  positively charged core of atom then called
  nucleus
• The size of the nucleus was much smaller(10-14m)
  than size of the atom (10-10m)

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Angular distribution of scattered ?-particles
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Models of Atom
Rutherford model of atom
Thomson model of atom
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Nuclear Stability
Proton unstable
Stable nuclei
Neutron unstable
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?-decay
During beta-minus decay, a neutron in an atom's
nucleus turns into a proton, an electron and an
antineutrino. The electron and antineutrino fly
away from the nucleus, which now has one more
proton than it started with. Since an atom gains
a proton during beta-minus decay, it changes from
one element to another. For example, after
undergoing beta-minus decay, an atom of carbon
(with 6 protons) becomes an atom of nitrogen
(with 7 protons).
Homework Explain ? decay
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Homework ?-decay
Full equations
Solve the following
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Binding energy per nucleon
EB(Z,N) ZMpNMn - M(Z,N)

• Nuclei with the largest binding energy per
  nucleon are the most stable.
• The largest binding energy per nucleon is 8.7
  MeV, for mass number A 60.
• Beyond bismuth, A 209, nuclei are unstable.

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Fusion and Fission Reactions
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Fusion Reactions
To obtain a fusion reaction, we must bring two
nuclei sufficiently close together for them to
repel each other, as they are both charged
positively.
A certain amount of energy is therefore vital to
cross this barrier and arrive in the zone,
extremely close to the nucleus, where there are
the nuclear forces capable of getting the better
of electrostatic repulsion. The probability of
crossing this barrier may be quantified by the "
effective cross section". The variation against
interaction energy expressed in keV of effective
cross sections of several fusion reactions is
shown on the graph .
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Fission Chain Reaction
At each step energy is released !
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Abundances of elements
Solar system abundances of the elements. Note
that the 14 ratio of helium to hydrogen (by
weight) is what the Big Bang theory would
predict. But other, heaver elements must come
from other processes.
Abundances of the elements in Earth. Comparison
with the figure above shows that Earth has lost
most of its primordial hydrogen and helium.
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Nuclear fusion chain in the Sun
The energy radiated from solar surface is
produced in the interior of the Sun by fusion of
light nuclei to heavier, more strongly bound
nuclei.
Homework Calculate the released energy.
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Nuclear Fission
Homework Calculate the released energy
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Electricity from Nuclear Fission
Nuclear power plants account In a nuclear
reactor, enriched Uranium, which is Uranium-238
with a high concentration of Uranium-235,
undergoes a process known as Induced Nuclear
Fission. Nuclear Fission occurs when an atom of
a fissionable material is struck by a neutron and
splits into two lighter atoms, releasing a
massive amount of heat and gamma radiation. The
heat is used to boil water, producing steam used
to turn a generator.
17 percent of the worlds power.
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Power Plants
This is the Byron nuclear power plant in
Illinois with two reactors, one capable of
producing 1,194 Megawatts and the other 1,162
Megawatts. The cooling towers in the background
are not releasing smoke. The fog coming out is
merely condensed water vapor from cooling the
return steam from the turbines. This steam is not
coming out of the nuclear reactor.
There are several heat exchangers in between the
reactor water and the cooling water. Once cooled,
the water is circulated back through the reactor
to be heater to steam again.