Scintillation Counter:

The scintillation counter is a solid state radiation detector.

  DESCRIBE the operation of a scintillation counter to involve:

a. Radiation detection

b. Three classes of phosphors

c. Photomultiplier tube operation

The scintillation counter is a solid state radiation detector that uses a scintillation crystal (phosphor) to detect radiation and generates light pulses. Below Figure is important within the explanation of scintillation counter operation.

As radiation interacts inside the scintillation crystal, energy is transferred to bound electrons of the crystal's atoms. The electron enters the conduction band and is free from the binding forces of the parent atom if the energy which is transferred is greater than the ionization energy. That leaves a vacancy in the valence band and is termed a hole. The electron remains attached if the energy transferred is less than the binding energy, but exists within an excited energy state. At one again, a hole is created in the valence band. Through adding impurities in during the growth of the scintillation crystal, the manufacturer is able to generate activator centers along with energy levels situated inside the forbidden energy gap. The activator center could trap a mobile electron, that increased the activator center from its ground state, G, to an excited state, E. While the center de-excites, a photon is emitted. The activator centers in a scintillation crystal are referred to as luminescence centers. The emitted photons are in the visible region of the electromagnetic spectrum.

Figure: Electronic Energy Band of an Ionic Crystal