Lecture Notes: Radiation Source and Detector Efficiency

Introduction

• Shift from theoretical to practical applications of radiation.
• Discussed hypothetical radiation source and unknown detector efficiency.

Radiation and Distance

• Geiger counter (GM tube) and cobalt-60 source used as examples.
• Calculating counts expected from a detector at a certain distance.
• IDC offers tools like laser cutters for creating experimental setups.

Dose Distance Relationship

• Activity proportional to 1/ R².
• Discussion on how solid angle is calculated and its implications on radiation detection.
• Formula: Solid angle (Ω) = Area / R².

Solid Angle Approximation

• For large distances, simple formula approximates well.
• Real solid angle requires complex calculation.
• Issues arise when source is too close to the detector.

Units and Calibration

• Solid angles measured in steradians.
• Calibration of detector efficiency is crucial.

Experiment with Bananas

• Burned bananas used as a source of potassium-40.
• Importance of increasing signal strength or counting time for accurate measurements.
• Discussion on radioactivity of bananas.

Statistical Confidence in Measurements

• Importance of background count and signal strength.
• Counting time and its role in statistical certainty.
• Explanation of standard deviation in radiation measurements.

Measurement Error and Confidence

• Poisson statistics used to determine standard deviation.
• Error in counting rates calculated using quadrature.
• Practical applications in estimating required counting time.

Reactor Power Manipulations

• Experiment involves increasing/decreasing reactor power using different absorbers.
• Importance of controlling reactor power.
• Logbook entries and safety measures during operations.

Detectors and Efficiency

• High purity germanium detectors explained.
• Importance of shielding and calibration in radiation labs.

Practical Applications

• Use of NIST standards for comparative analysis.
• Historical use of NAA in environmental and forensic science.
• Various unusual samples analyzed over the years.

Conclusion

• Experimentation in counting lab and applications of detectors.
• Understanding the balance between statistical confidence and practical measurement constraints.
• Real-world applications and ongoing research in radiation detection and analysis.