Detection and Measurement Flashcards
7 cards from real NRRPT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Detection and Measurement flashcards as text
In a proportional counter, the gas multiplication factor (M) represents:
Answer: The factor by which primary ionization is amplified through avalanche multiplication
In the proportional region, primary electrons accelerate and create additional ionization; the gas multiplication factor M is the ratio of total collected charge to initial ionization charge.
A fission chamber detector is primarily used to measure:
Answer: Neutron flux in reactor environments where high gamma fields are present
Fission chambers use U-235 or Pu-239 coatings where neutron-induced fission produces heavy, highly ionizing fragments detectable above the gamma background through pulse height discrimination.
The 'air-equivalence' of a detector material is important because:
Answer: The detector's energy response should mimic the ionization characteristics of air or tissue
Air-equivalent or tissue-equivalent detector materials have similar atomic composition (effective Z) to air or tissue, ensuring the detector's energy response matches the quantity being measured.
What does the 'W-value' represent in radiation detection?
Answer: The average energy required to produce one ion pair in a detector fill gas
The W-value (approximately 35 eV for air) is the mean energy deposited per ion pair formed, used to convert ionization measurements to absorbed dose.
An area radiation monitor continuously displaying dose rate near a hot cell would most likely use which detector type?
Answer: High-pressure ionization chamber or Geiger-Mueller tube with remote readout
Area radiation monitors typically use robust ionization chambers or GM tubes with remote readout capability, providing continuous real-time dose rate data to a central monitoring system.
When performing a low-background beta counting measurement, the choice to use a liquid scintillation counter (LSC) over a gas-flow proportional counter is justified when:
Answer: The sample contains pure low-energy beta emitters like H-3 or C-14 dissolved in solution
LSC is ideal for H-3 and C-14 because the emitter is mixed directly with the scintillant, achieving near-100% geometric efficiency for these low-energy betas that cannot penetrate detector windows.
The process of 'quenching' in liquid scintillation counting refers to:
Answer: Any process that reduces the light output or light transmission to the photomultiplier tubes
Quenching reduces LSC counting efficiency by either absorbing energy before scintillation (chemical quench) or absorbing emitted light (color quench), requiring quench correction for accurate results.