David Argento

The nuclear underpinnings of Cosmogenic Nuclides

David Argento

David Argento

Outline

• Atomic and particle basics– Atomic structure– Major groups of subatomic particles

• Nuclear forces, structures and processes– Four primary forces– Radioactivity– Forms of radiation

David Argento

Before we launch

• David Argento– Graduate student– JHN423– dargento@u.washington.edu

• References– Hyperphysics: http://hyperphysics.phy-astr.gsu.edu/hbase/HFrame.html– Wickipedia: useful, but be very skeptical– Hundreds of papers

• Apologies for errors, omissions, over simplicity, over complication, and pace.

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The Atom

electronelectron

proton

neutron

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Quarks

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Subatomic Particle Families & Generations

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Back to the nucleus

• What happens with similar charged objects?

10-15m10-10m

FE = ~100N

FG = ~10-35N

221

r

QkQFE

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Forces

Force Range Primary source/ interaction

Gravity Infinite Mass

Electromagnetic Infinite charge

Weak nuclear ~10-18m W and Z bosons, neutrinos and quarks

Strong Nuclear ~10-15m Gluons and nucleons

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Nuclear Stability

• The nucleus is stable in specific proton and neutron combinations

• Stability is based on electric-nuclear force balance

• Unstable nuclei will decay to achieve stability• Eject energy, electrical charge and nucleons

(protons and neutrons)• Thus…

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Radioactivity

• Gamma radiation– Electromagnetic

radiation

• Alpha radiation– Helium nucleus

• Beta radiation– Electron or positron

• Neutrons

• Neutrinos

• Fission

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Gamma Radiation

• Electromagnetic Radiation

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Alpha radiation

• Energetic ejection of helium-4 in 2+ state (no electrons)

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Beta Radiation

• Energetic ejection of electron or positron

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Neutrons

• Ejection of neutrons (low to high energy)

• Can also accompany other decay modes

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Neutrinos

• Weakly interacting, extremely small mass, and accompanies most, radioactive decay

• Not important for this the purpose of this class, but there is promise for use as probe of the interior of the earth (McDonough, W. F., Mapping the interior of the Earth, Science, 31, August 2007, pp1177 - 1178)

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Fission

• Not important for this class, but an important aspect of radioactive decay

• In-situ neutron source, must be corrected for if fissile material is present

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Probability and the Half life

• Each and every atom of an isotopic species has the same probability of decaying during a period of time.

• This results in a set fraction of the population decaying in the same time period, regardless of total population

• Each isotope is different

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Decay Curve

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Modeling exponential decay

2/1

2

10

T

t

NN

toeNN

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Population change

• Take the derivative:

Ndt

dN