What Are Gamma Detectors?

Are gamma detectors necessary for the detection of radiation?

Photons, the energy packets that make up visible light, also make up gamma rays. But gamma-ray photons contain millions of times more energy than visible light photons, which is why they are so powerful. There are also very few sources for cosmic gamma rays (that is, they produce relatively few gamma-ray photons for us to detect near Earth). In the same way as X-rays are detected one photon at a time, gamma rays are detected the same way.

In order to identify gamma rays, scientists look at the impact they have on materials. Electron collisions can either result in an electron being bounced off like a cue ball (Compton scatter) or an electron being propelled to a higher energy level (photoelectric ionization). Furthermore, because gamma rays contain so much energy, some of this energy may be immediately converted into matter by forming an electron and another particle (called a pair production). A current of electricity is formed when electrons begin to travel as a result of all of these interactions. Once the currents are amplified, the energy and direction of the initial gamma ray may be determined by measuring the currents.

There are two basic categories of gamma detectors: spectrometers and imagers.

In optical astronomy, spectrometers or photometers are commonly referred to as the first class. To put it another way, these devices are "light buckets" that aim to capture as many photons as possible from a certain area of sky. Scintillators or solid-state detectors are commonly used to turn the gamma ray into optical or electrical signals that may be recorded.

In the second class are gamma-ray detectors, which are extremely difficult to use. They either utilize a device like a coded-mask to reconstruct a picture or depend on the nature of the gamma-ray interaction mechanism (such as pair creation or Compton scattering) to compute the arrival direction of the incoming photon.