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Lecture 6

PHYS-3306EL Lecture Notes - Lecture 6: Van De Graaff Generator, Sudbury Neutrino Observatory, Gas-Filled Tube


Department
Physics
Course Code
PHYS-3306EL
Professor
K.Leszczynski, D.Boreham
Lecture
6

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Alpha particles don’t cause many effects unless they are inhaled or ingested.
o Examples
Radon – inhaled
C-14 – ingested
K-40 – ingested
Sudbury Neutrino Observatory (SNO lab)
o 2 km down from the earth’s surface
o Under 2 km of rock
o In Creighton mine
o The rock filters out almost all of the cosmic radiation.
o Neutrinos are weakly reactive, so they make it through the rock.
o Studies biological effects of neutrinos
Growing cells, observing effects on cells, etc.
X-rays
o Named that because the ray was previously unknown
X often stands for an unknown, so the discoverer called them X-rays
Linear accelerator (linac)
o Pro
Can give radiation from different angles
o Con
Also irradiates healthy tissue
o Solution
Irradiate from different angles
Tumour hit more than once
Each section of healthy tissue only hit once
Radiation exposure sources for the general population
o Background radiation
48%
Examples
Cosmic radiation
o From space
o Positive ions
o Interacts with the atmosphere
Terrestrial radiation
o From Earth
o Examples
Uranium
Thorium
Radon
14-carbon
o In the human body
40-potassium
o In the human body
o Man-made radiation
52%
Examples

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Nuclear weapons
Airport body scanners
Medical imaging
Medical treatments
Breakdown
Nuclear medicine/X-rays
o 91%
o Dental X-rays
50% of medical exposures
25 mSv
Consumer products
o 6.5%
Occupational exposure
o 1%
Fallout
o 1%
Nuclear fuel cycle
o 0.5%
The latency period for cancer developing from radiation exposure is about 20 – 30 yr.
o Because of the many variables, you can’t pick out the cause(s) of a 1% increase in
cancer risk 20 – 30 yr. down the road.
Some radiation history
o 1895
Using a gas discharge tube, Wilhelm Conrad Roentgen discovered X-rays.
o 1899
First use of X-rays
To treat basal-cell carcinoma of the nose skin
More than 100 treatments given over 9 mo.
About 30 yr. later, many patients were receiving radiation and impressed by
the experience.
o 1907
The Curies lent radium to different doctors in Paris.
A crossfire method was used to cure a child’s erectile angioma.
o After the discovery of the benefits of radiation and before discovery of the side
effects of radiation
Radium used for everything
Cream
Water
Example
o Radioendocrinator
o c. 1930
Radioendocrinator
1.7 mGy
Localized
o Worn like an athletic strap
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