Nuclear Decay

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Nuclear Decay
Jr. Lab II sp01

• Lise Johnson
• Phillip Forkner

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List of Experiments

• Geiger Plateau
• Background Radiation Measurment
• Resolving Time
• Shelf Ratios
• Randomness of Disintegration

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Geiger Tubes

• Gas filled cylindrical tubes with an applied
  electric field
• Charged particles entering the tube cause a
  measurable pulse
• Rely on gas multiplication/ Townsend Avalanches
• Not proportional Counters

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Geiger Plateau

• No gas multiplication at low voltages
• At minimum voltage avalanches begin to form
• On the plateau avalanche increases are minimal
• At higher voltages avalanches are uncontrollable
• Operating above the plateau fries the tube
• Optimal operating voltage is at the knee of the
  plateau

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Background Measurement

• No source, Voltage 850, with and without
  shielding
• Found that approx 66 of the background was
  shielded

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Resolving Time

• There is an amount of time after a hit that the
  counter will not register subsequent hits
• Dead time

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Shelf Ratios

• Radiation is emitted from a source in all
  directions
• Only a fraction reaches the counter
• How does the count fall off when the source is
  moved ?
• Beta sources fall off faster because they are
  absorbed by air

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