How does a gamma spectrometer work?

In gamma-ray spectroscopy, the energy of incident gamma-rays is measured by a detector. By comparing the measured energy to the known energy of gamma-rays produced by radioisotopes, the identity of the emitter can be determined.

Why does photo peak and annihilation peak appear on the spectrum?

This is know as coincidence summing. The pulse size reflects the sum of the energies deposited by the two photons. If both photons interact via the photoelectric effect, and this happens with sufficient frequency, a summation (sum) peak appears on the spectrum.

What do the counts of the measurements in the gamma-ray spectrum signify?

Detector efficiency The probability that an emitted gamma ray will interact with the detector and produce a count is the efficiency of the detector. High-efficiency detectors produce spectra in less time than low-efficiency detectors.

What causes backscatter peak?

Backscattered peaks. Close inspection of a gamma-ray spectrum may reveal a wide peak with energy <250keV which does not correspond to a known photon from the source. Such a feature, termed a Backscatter peak, is due to gamma-rays which first interact by Compton scattering with the shielding.

What is the annihilation peak how it is produced?

As the name suggests, radiation of this energy is produced by annihilation of positrons and electrons. It is produced around positron-emitting radioactive materials, and is also produced when energetic photons (gamma or x-rays with energy exceeding 1.02 MeV) are absorbed in matter through the pair-production process.

What causes the backscatter peak?

What is an annihilation peak?

For high energy gamma rays (greater than 1.02 MeV), electron-positron pair production is a possible interaction. If one annihilation photon is absorbed and the second exits the crystal, then 0.51 MeV is removed from the photopeak, resulting in a secondary peak 0.51 MeV below the photopeak. …

What are gamma rays used for?

Gamma rays are ionizing electromagnetic radiation, obtained by the decay of an atomic nucleus. Gamma rays are more penetrating, in matter, and can damage living cells to a great extent. Gamma rays are used in medicine (radiotherapy), industry (sterilization and disinfection) and the nuclear industry.

What causes backscattering?

Backscattering is defined also as the phenomenon that occurs when radiation or particles are scattered at angles to the original direction of motion of greater than 90°. It is a diffuse reflection due to scattering, as opposed to specular reflection like a mirror.

What is gamma backscatter?

The NDC Backscatter Gamma sensor (GBS) is an integrated source and detector instrument that provides a thickness or weight measurement from one side of the sheet. Its compact size allows product measurements to be taken from areas of the process that are often inaccessible to conventional sensors.

Are annihilation photons gamma rays?

Annihilation photons are similar to gamma rays in their ability to penetrate large distances of matter without interacting. They may undergo Compton or photoelectric interactions elsewhere or may escape from detectors of small size.

What is a gamma ray spectrometer?

A gamma ray spectrometer (GRS) is a sophisticated device for measuring the energy distribution of gamma radiation. For the measurement of gamma rays above several hundred keV, there are two detector categories of major importance, inorganic scintillators as NaI (Tl) and semiconductor detectors.

What determines the shape of the peak of a spectrophotometer?

The peak shape is usually a Gaussian distribution. In most spectra the horizontal position of the peak is determined by the gamma ray’s energy, and the area of the peak is determined by the intensity of the gamma ray and the efficiency of the detector. The most common figure used to express detector resolution is full width at half maximum (FWHM).

What determines the width of the peaks in a gamma spectrum?

The width of the peaks is determined by the resolution of the detector, a very important characteristic of gamma spectroscopic detectors, and high resolution enables the spectroscopist to separate two gamma lines that are close to each other.

What are the components of a gamma spectroscopy detector?

Additional components may include signal amplifiers, rate meters, peak position stabilizers, and data handling devices. Gamma spectroscopy detectors are passive materials that are able to interact with incoming gamma rays.