1. ECE699 – 004 Sensor Device Technology
Chapter 6 Radiation Detectors
Fall 2018
George Mason University

2. Introduction
N: number of nuclei still undecayed
dN, the number of nuclei which decay in a small interval dt
λ is a decay constant specific for a given substance
It is defined as radioactivity, unit becquerel (Bq) = s-1
Absorbed dose is measured in grays (Gy) = 1 joule per kilograms (J/kg)

3. Scintillating Detectors
-need photomultipliers to magnify the signal because the light intensity resulting from radiation is extremely small

4. The scintillation materials: When detecting 0
The scintillation materials: When detecting MeV γ-rays, the energy resolution for sodium iodine scintillators is limited to about 6% - mean the energy required to produce a photoelectron is about 1000eV

5. A new design of photomultiplier

6. 2. Ionization detectors
Rely on the ability of some gaseous and solid materials to produce ion pairs in response to the ionization radiation
2.1 Ionization chambers
-oldest and most widely used
-ionizing particle causes ionization and excitation of gas molecules along its passing track

9. 2.2 Proportional chambers – pulse mode and relies on gas multiplication

10. 2.3 Geiger-Muller(G-M) counters -much higher applied voltage

11. 2.4 Semiconductor detectors -radiation induces a large number of carriers: electron-hole pairs -good for γ-ray detection

12. Li-drifted (Ge/Li) detector

13. Materials: relatively high Z-value with a large bandgap semiconductor materials