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Radiation Detection Measurement II

Pulse height analyzers. Many radiation detectors produce electrical pulses whose amplitudes are proportional to the energies deposited in the detector by individual interactionsPHAs are electronic systems that may be used with these detectors to perform pulse height spectroscopy and energy-selectiv

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Radiation Detection Measurement II

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    1. Radiation Detection & Measurement II Pulse height spectroscopy Nonimaging detector applications Counting statistics

    2. Pulse height analyzers Many radiation detectors produce electrical pulses whose amplitudes are proportional to the energies deposited in the detector by individual interactions PHAs are electronic systems that may be used with these detectors to perform pulse height spectroscopy and energy-selective counting In energy-selective counting, only interactions that deposit energies within a certain energy range are counted

    3. PHAs (cont.) Energy-selective counting can be used to: Reduce the effects of background radiation Reduce the effects of scatter Separate events caused by different radionuclides in a mixed radionuclide sample Two types of PHAs single-channel analyzers (SCAs) and multichannel analyzers (MCAs) Pulse height discrimination circuits incorporated in scintillation cameras and other nuclear medicine imaging devices to reduce effects of scatter

    4. Single-channel analyzer systems High-voltage power supply typically provides 800 to 1,200 volts to the PMT Raising voltage increases magnitude of voltage pulses from PMT Preamp connected to PMT using very short cable Amplifies voltage pulses to minimize distortion and attenuation of signal during transmission to remainder of system

    6. SCA systems (cont.) Amplifier further amplifies the pulses and modifies their shapes gain typically adjustable SCA allows user to set two voltage levels, a lower level and an upper level If input pulse has voltage within this range, output from SCA is a single logic pulse (fixed amplitude and duration) Counter counts the logic pulses from the SCA for a time interval set by the timer

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