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Radiation
Radiation - ILT2013
20
Physics
06/30/2011

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Term
Define electron volt
Definition
The amount of energy gained by an electron when it is accelerated through a potential of 1 volt.
Term
Define ionization
Definition
The process of removing orbital electrons from atoms.
Term
Describe the process of ionization
Definition
Radiation passing through matter transfers energy to the target atom and may cause the ejection of orbital electrons.
Term
Define secondary ionization
Definition
The process by which dislodged electrons and the positive ion cause other electrons to be driven from their orbits.
Term
Define specific ionization
Definition
The number of ion pairs produced by ionizing radiation per unit length of travel.
Term
Define total ionization
Definition
The total number of ion pairs produced by a particle or electromagnetic wave.
Term
Describe alpha radiation with respect to its mass, charge, energy, source, velocity, and range in air
Definition
mass = 6.70X10^-24 grams or 4.03477amu
charge = +2
energy = between 4 and 10 MeV
source = radioactive decay and fission of heavy nuclei.
velocity = ~1/10 speed of light (between 2000 and 20,000 miles/sec)
range in air = 2 in.
Term
Explain reasons for the alpha’s
low penetrating power.
Definition
The short range, or low penetrating power, is due to the large positive charge and a comparatively large mass (4 amu).
Term
Describe the interaction of alphas
with matter.
Definition
Alphas have high probability of interaction with orbital electrons through electrostatic interaction leaving approx. 120,000 ion pairs per inch of travel in air.
Term
Describe beta radiation with
respect to its mass, charge,
energy, source, velocity, and
range in air.
Definition
a The charge is minus one
b Mass is identical to an electron which is 9.1 x 10 -28
grams or 0.00055 amu.
1) A beta minus particle is 1/1840 the mass of a neutron.
c. Energy level ranges between 6 KeV and 4.81 MeV.
d. Sources
1) Most fission products at the plant are neutron
heavy (discussed later in Chapter 4) and thus
beta minus decay.
2) These sources are usually contained within a
metal pipe or tank, which provide adequate
shielding to stop most high-energy beta particles.
e Betas exist at about 99% the speed of light.
Term
Explain reasons for the difference
in penetration power of beta radiation.
Definition
Beta particles penetrate matter much farther than alpha particles due to the fact that they have less mass (.00055 vs. 4 amu), a higher velocity (.99
vs. .1 times speed of light), and a lower charge(-1 vs. +2).
Term
Describe the interaction process
of betas with matter.
Definition
Beta particles interact with orbital electrons through electrostatic interactions or sometimes by direct collision, both of which result in ionization and/or excitation.
Term
Describe the interaction process
of electromagnetic radiation with
matter.
Definition
When a radioactive atom decays by beta,
neutron, or alpha emission the nucleus is frequently left in an excited state – above its ground state. This excess energy may be released in the form of a gamma ray.
X-rays are produced when electrons drop between orbital shells.
Term
Describe gamma and x-ray radiation with respect to its mass,charge, energy, source, velocity,and range in air.
Definition
b. Electromagnetic radiation has no mass.
c. Electromagnetic radiation has no charge.
d. Energies
1) Gamma rays emitted by natural radioisotopes
have energies between 0.04 and 3.2 MeV with fission product gammas ranging higher.
2) X-rays generally exist at lower energies, but there is some overlapping. X-rays are commonly
emitted in the lower energy range, 0 to 88 KeV.
e. Sources
1) Gammas originate from nuclei, which are in an excited state.
2) X-rays are emitted when an electron drops to a lower energy orbit.
f Electromagnetic radiation travels at the speed of light (186,000 miles/sec).
g. Range
1) The range of high-energy electromagnetic
radiation is theoretically infinite since the intensity
of the radiation decreases exponentially as it
passes through material.
Term
Explain reasons for the difference
in penetrating power of
electromagnetic radiation.
Definition
Due to the high energy and lack of mass or charge, gamma and X-rays have a very high penetrating power in matter.
Term
Describe the interaction process
of electromagnetic radiation with
matter.
Definition
Photoelectric Effect,Compton Scattering, and Pair Production.
Term
List 3 natural sources of radiation.
Definition
1.Cosmic rays
2.Natural radioactivity within rocks, soils, minerals, and building materials
3.Natural radioactive isotopes in the body
Term
List 3 man-made sources of radiation.
Definition
a X-ray machines
b Low energy radioactive tracers for diagnosis of disease
c. High-energy radioactive isotopes used for treatment of diseases such as cancer.
Term
List 3 beneficial uses for radiation.
Definition
a X-ray machines
b Low energy radioactive tracers for diagnosis of disease
c. High-energy radioactive isotopes used for treatment of diseases such as cancer.
Term
Explain uses of laboratory radiation sources in connection with radiation detection instruments.
Definition
a. Neutron sources – startup of nuclear reactors
b Radiography – X-rays to detect material and welding flaws.
c. Radioactive sources – alignment and calibration of radiation detection equipment.