CHP Radiation Measurement and Instrumentation 2

Question 1

A thermoluminescent dosimeter (TLD) uses which physical process to record dose?

Accepted Answer

Trapping of electrons in crystal lattice defects

Answer

TLDs work by trapping electrons in crystalline defect sites; heating the crystal releases them as measurable light proportional to absorbed dose.

Question 2

The Bragg-Gray cavity theory applies to ionization chambers when the cavity:

Accepted Answer

Is small enough not to perturb the radiation field

Answer

Bragg-Gray theory requires the cavity to be small relative to the range of secondary electrons so it does not disturb the fluence of charged particles.

Question 3

Which detector type is best suited for measuring fast neutrons through proton recoil?

Accepted Answer

Proton recoil scintillator (EJ-301)

Answer

Organic scintillators such as EJ-301 (NE-213) detect fast neutrons via elastic scattering off hydrogen nuclei, producing measurable proton recoil tracks.

Question 4

Dead time in a Geiger-Müller tube is the period during which:

Accepted Answer

The detector cannot register a new event after a previous pulse

Answer

Dead time is the interval following a pulse during which the detector is paralyzed and cannot produce a new independent output pulse.

Question 5

The energy resolution of a sodium iodide (NaI) detector at 662 keV (137Cs) is approximately:

Accepted Answer

6–8%

Answer

NaI(Tl) detectors typically achieve 6–8% full-width at half-maximum energy resolution at 662 keV, far inferior to HPGe but adequate for many field applications.

(CHP) Certified Health Physicist Practice Test

(CHP) Certified Health Physicist Practice Test

CHP Radiation Measurement and Instrumentation 2