Radiation Fundamentals & Detection Flashcards

Which interaction mechanism is responsible for most of the ionization produced by alpha particles in tissue?

Answer: Coulombic interactions with orbital electrons

Alpha particles lose energy primarily through coulombic (electrostatic) interactions with orbital electrons, causing excitation and ionization along their path.

A Geiger-Müller tube operating in the Geiger region produces output pulses that are:

Answer: Independent of the energy of the incident radiation

In the Geiger region, avalanche discharge saturates the detector so all pulses are the same size regardless of incident radiation energy.

The Q-value of a nuclear reaction is defined as:

Answer: The total kinetic energy of the products minus that of the reactants

The Q-value equals the kinetic energy of products minus that of reactants, which corresponds to the mass-energy difference (Q = Δmc²).

Which property of a scintillation detector makes it superior to a GM tube for gamma spectroscopy?

Answer: Pulse amplitude proportional to photon energy

Scintillation detectors produce light output proportional to the deposited energy, enabling energy discrimination and spectroscopy.

Thermoluminescent dosimeters (TLDs) measure dose by:

Answer: Measuring charge released when heated crystals luminesce

TLDs trap electrons in crystal defects; when heated, electrons release energy as light proportional to absorbed dose.

The specific ionization of a charged particle in matter generally increases as the particle:

Answer: Slows down near the end of its range

Specific ionization increases sharply near the end of a charged particle's range, forming the Bragg peak as the particle slows.

Which of the following nuclides undergoes electron capture (EC) decay?

Answer: Iron-55

Iron-55 decays by electron capture to Manganese-55, emitting characteristic X-rays rather than a beta particle.