DETECTION AND MEASUREMENT OF RADIOACTIVITY

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NANIK DWI NURHAYATI,S.SI,M.SINANIK DWI NURHAYATI,S.SI,M.SI

RADIATION DETECTORS

• Instruments used in the practice of health physics serve a wide variety of purposes

• one finds instruments designed specifically for the measurement of a certain type of radiation, such as low-energy X-rays, high-energy gamma rays. fast neutrons, and so on

• The basic requirement of any such instrument is that its detector interact with the radiation in such a manner that the magnitude of the instrument's response is proportional to the radiation effect or radiation property being measured

Radiation Measurement Principles

Detector

SignalPhysicalChemicalBiological

Reader

Calibration

Assessme

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Amplification

RADIATION DETECTORS

Type Radiation Detector

• Detector Gas• Detector Scintilation• Detector Semikonduktor

Radiation Detector • Elektroskup (Electroscope)• Kamar Ionisasi (Ionization Chamber)• Proporsional Counter• Geiger-Muller Counter• Cloud Chamber• Diffusion Chamber• Bubble Chamber• Nuclear Emulsion• Scintillation Counter• Solid State Detector• The Spark Chamber• Cerenkov Detecto

Examples

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Operating Principles of Semiconductor detectors

• Si semiconductor is a layer of p-type Si in contact with n-type Si.

• What happens when this junction is created?– Electrons from n-type migrate across junction to fill holes in p-

type– Creates an area around the p-n junction with no excess of holes

or electrons– Called a “depletion region”

• Apply (+) voltage to n-type and (-) to p-type:– Depletion region made thicker– Called a “reverse bias”

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Thermoluminescence

(TL) is the ability to convert energy from radiation to a radiation of a different wavelength, normally in the visible light range.

Two categories Fluorescence - emission of light during or immediately

after irradiationNot a particularly useful reaction for TLD usePhosphorescence - emission of light after the

irradiation period. Delay can be seconds to months. TLDs use phosphorescence to detect radiation.

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Summary

• Wide range of detection equipment available• Understand strengths and weaknesses of each• No single detector will do everything• We’ll get to selection issues in the next two

days

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