Which counter type is typically used for beta-emitting isotopes such as H-3 and C-14?

Which counter type is typically used for beta-emitting isotopes such as H-3 and C-14?

• A. Crystal gamma counter
• B. Liquid beta counter
• C. Gas proportional counter
• D. Scintillation counter

Answer: (B)

For beta emitters with very low energy like tritium (H-3) and carbon-14, the most efficient way to measure their activity is to convert the beta energy into light in a scintillant that’s in liquid form. In liquid scintillation counting, the sample is mixed with a scintillation cocktail, placing the radioactive material in intimate contact with the scintillant molecules. When a beta particle lands in the liquid, it deposits energy that excites the solvent and fluors, producing light pulses that are picked up by photomultiplier tubes. This setup yields high counting efficiency for low-energy betas and handles the specific chemistry of many H-3 and C-14 samples well. The other detectors are less optimal for these isotopes. A crystal gamma counter is designed for gamma photons, not beta particles. A gas proportional counter relies on ionization in a gas and tends to be less efficient for very low-energy betas and often requires particular sample geometries. A general scintillation counter can detect beta radiation, but without the liquid medium, it doesn’t achieve the same high efficiency for low-energy beta emissions as liquid scintillation counting does.

For beta emitters with very low energy like tritium (H-3) and carbon-14, the most efficient way to measure their activity is to convert the beta energy into light in a scintillant that’s in liquid form. In liquid scintillation counting, the sample is mixed with a scintillation cocktail, placing the radioactive material in intimate contact with the scintillant molecules. When a beta particle lands in the liquid, it deposits energy that excites the solvent and fluors, producing light pulses that are picked up by photomultiplier tubes. This setup yields high counting efficiency for low-energy betas and handles the specific chemistry of many H-3 and C-14 samples well.

The other detectors are less optimal for these isotopes. A crystal gamma counter is designed for gamma photons, not beta particles. A gas proportional counter relies on ionization in a gas and tends to be less efficient for very low-energy betas and often requires particular sample geometries. A general scintillation counter can detect beta radiation, but without the liquid medium, it doesn’t achieve the same high efficiency for low-energy beta emissions as liquid scintillation counting does.