gammaspectrometers

Gammaspectrometers are analytical instruments used to measure the energy and intensity of gamma rays emitted by radioactive sources. By producing gamma spectra, they enable identification of radionuclides and quantification of activity in a sample or environment.

A typical gamma spectrometer comprises a detector, a signal-processing chain, and a data-acquisition system. The detector converts gamma interactions into electrical signals; a preamplifier and shaping amplifier condition the signals; an analog-to-digital converter creates an energy spectrum on a multichannel analyzer, from which a gamma spectrum is generated and stored for analysis.

Common detectors are scintillation crystals, such as sodium iodide doped with thallium (NaI(Tl)), CsI(Tl), and BGO, and semiconductor detectors such as high-purity germanium (HPGe) and cadmium zinc telluride (CdZnTe, CZT). HPGe provides superior energy resolution and accurate peak identification but requires cooling, typically with liquid nitrogen or a mechanical cooler. Scintillators offer higher detection efficiency and can operate at room temperature, but have broader energy peaks. CZT operates at room temperature with moderate resolution and is favored for portable systems.

Applications include radionuclide identification in nuclear physics and environmental monitoring, radiological safety and safeguards, industrial process control, and medical imaging such as single-photon emission computed tomography (SPECT), where gamma spectroscopy aids isotope identification and activity determination.

Calibration and analysis involve energy calibration using known gamma lines, efficiency calibration as a function of energy and geometry, and background subtraction. Peak search and fitting extract peak areas, which with detector efficiency yield nuclide activities. More advanced work uses Monte Carlo simulations to model detector response and correct for summing, escape peaks, and dead time.