detection and measurement of radioactivity 1 nanik dwi nurhayati,s.si,m.si
TRANSCRIPT
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DETECTION AND MEASUREMENT OF RADIOACTIVITY
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NANIK DWI NURHAYATI,S.SI,M.SINANIK DWI NURHAYATI,S.SI,M.SI
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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
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• 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
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Radiation Measurement Principles
Detector
SignalPhysicalChemicalBiological
Reader
Calibration
Assessme
nt
Amplification
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RADIATION DETECTORS
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Type Radiation Detector
• Detector Gas• Detector Scintilation• Detector Semikonduktor
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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
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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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