memory phosphor

A memory phosphor is a material used in radiation detection, particularly as an alternative to traditional X-ray films. It functions similarly to thermoluminescent dosimeter (TLD) crystals, but instead of heat, it uses light to release trapped charges.

When exposed to X-rays, the memory phosphor screen builds up a pattern of trapped charges. This pattern is then read by scanning the screen with a laser beam. The laser stimulates the release of the trapped charges, which emit light. By measuring the intensity of this emitted light, the X-ray image is reconstructed. A key advantage is that the screen can be reused multiple times after the charges are erased during readout.1

Phosphors, in general, are solid materials that emit light when exposed to radiation like ultraviolet light or electron beams. Memory phosphors specifically utilize a process where charges are trapped for extended periods, allowing for later readout. This trapping mechanism is related to phosphorescence, where light emission persists after the exciting radiation is removed, often due to electrons being held in a metastable state or "electron trap".213