What is the primary function of the getter circuit in an image intensifier?

The primary function of the getter circuit in an image intensifier is to maintain vacuum within the tube. The getter is a material that absorbs any residual gas that may be present in the vacuum envelope of the image intensifier. By removing these gases, the getter helps to ensure that the vacuum remains at a sufficient level for optimal performance of the image intensifier. A good vacuum is essential for the efficient movement of electrons and for the overall functioning of the device, as any gas could lead to unwanted scattering of electrons and degradation of the image quality.

This function is critical in ensuring that the image intensifier operates efficiently and produces high-quality images. Without the getter maintaining the vacuum, the image intensifier's performance would suffer, resulting in lower brightness and clarity in the resulting images.