Common types of industrial CT radiation sources and detectors

Industrial CT can clearly, accurately, and intuitively display the internal structure, composition, material, and defect status of the detected object in the form of two-dimensional sectional images or three-dimensional stereoscopic images without damage to the detected object. It is a high-tech product involving many disciplines.

The radiation sources commonly used in industrial CT include X-ray machines and electron linear accelerators, collectively known as electron radiation generators. The common advantage of electronic radiation generators is that they no longer produce radiation after cutting off the power, and this inherent safety is very beneficial for industrial use.

The advantages of isotopic radiation sources are their simple energy spectrum, low energy consumption, small and relatively simple equipment size; Its disadvantage is that the intensity of the radiation source is low, and in order to improve the intensity of the source, the volume of the source must be increased, resulting in an increase in the size of the "focus" and unsatisfactory resolution indicators. Therefore, it is less commonly used in industrial CT.

The radiation energy of the X-ray machine is adjustable, with an energy of ≤ 450kV. The radiation source energy of the electron linear accelerator is not adjustable, and the actual peak energy range used is 1-16MeV. Although higher energy can be achieved, it is mainly used for experiments.

In practical applications, the selection of radiation sources mainly depends on the wall thickness of the inspected workpiece, while also considering cost issues.

There are mainly two types of detectors commonly used in industrial CT: linear array detectors and area array detectors.

1. Array detector

Compared to linear array detectors, planar array detectors have higher ray utilization and are suitable for DR imaging, achieving real-time or quasi real-time dynamic imaging; In addition, array detectors are also more suitable for three-dimensional direct imaging. Due to structural reasons, all array detectors have a common drawback, which is low X-ray detection efficiency and inability to limit scattering and interference issues; The dynamic range is small, and the application effect in high energy range is poor.

2. Linear array detector

Main advantage: The depth of the scintillator in the ray direction can be unrestricted, thereby capturing most of the incident X-photons and improving detection efficiency. Especially under high-energy conditions, photon acquisition time can be shortened; Due to the independence of scintillators and the presence of tungsten or other heavy metal barriers between them, X-ray interference is reduced.

The main disadvantage is that the pixel size cannot be made too small, and its adjacent spacing (pitch) is generally greater than 0.1mm. The price is also relatively high.

Usually, array detectors can be wired under high and low energy conditions.