HVL/ATTENUATION Flashcards
What is the formula for calculating the Half-Value Layer (HVL)?
How do you calculate the mass attenuation coefficient?
What is the relationship between HVL and attenuation?
How do you compare attenuation for water, ice, and steam?
What does μ/ρ represent and why is it important?
μ/ρ is the mass attenuation coefficient, which is independent of the physical state (solid, liquid, gas).
Key to comparing how different materials absorb radiation based on their density and composition.
Second Half-Value Layer (HVL₂)
What is HVL₂?
HVL₂ is the additional thickness required to reduce the beam intensity by another factor of 2 after the first HVL. Typically, HVL₂ > HVL₁ for polyenergetic beams.
What is the linear attenuation coefficient?
µ is the constant that describes how quickly a material reduces the intensity of radiation. It varies with material type and density. The unit of µ is cm⁻¹.
How do you calculate the mass attenuation coefficient?
The mass attenuation coefficient is µ/ρ, where µ is the linear attenuation coefficient, and ρ is the material’s density.
Formula: [µ/ρ] = cm²/g
How do you calculate the reduction in intensity of radiation through a material?
Use the equation: I = I₀ * e^(-µx)
Where:
I is the final intensity.
I₀ is the initial intensity.
µ is the attenuation coefficient.
x is the thickness of the material.
What happens to the intensity of radiation if the distance from the source is doubled?
A cesium source has an initial intensity of 27 cGy/hr at 0.1 m. It is placed in a lead pig 3.15 cm thick. If cesium’s HVL in lead is 0.55 cm, find:
- The intensity at 0.1 m after the block.
- The intensity at 2.75 m with and without the block.
- The dose after a 40-hour work week.
How do you calculate the thickness of a material needed to reduce the dose rate of radiation?
How do you convert from MeV to keV?
