Transcript Detection RA - nanikdn chemistry uns

DETECTION AND MEASUREMENT OF
RADIOACTIVITY
NANIK 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, highenergy 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
Signal
Physical
Chemical
Biological
Amplification
Calibration
Assessment
Detector
Reader
RADIATION DETECTORS
Type Radiation Detector
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Detector Gas
Detector Scintilation
Detector Semikonduktor
Radiation Detector
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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 ptype
– 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 irradiation
 Not a particularly useful reaction for TLD use
 Phosphorescence - emission of light after the
irradiation period. Delay can be seconds to months.
 TLDs use phosphorescence to detect radiation.
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Summary
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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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