Which scintillator has the longest decay time?

The scintillator with the longest decay time among the options provided is sodium iodide doped with thallium, commonly referred to as NaI (Tl). This material is known for its ability to efficiently convert high-energy photons into visible light, making it a popular choice in various types of imaging, including gamma cameras and PET scanners.

NaI (Tl) has a relatively long decay time, which is an important characteristic that can influence the timing resolution of imaging systems. The decay time refers to how quickly the scintillator material returns to its ground state after being excited by radiation, which is crucial in applications that require precise timing, such as in PET imaging where detecting quick successive decay events is necessary.

This longer decay time can lead to a slightly diminished rate of photon detection in rapid succession compared to scintillators with shorter decay times. However, NaI (Tl) remains favored for applications requiring high light output and good energy resolution.

In contrast, other scintillators like GSO (gadolinium oxysulphide) and BGO (bismuth germanate) exhibit shorter decay times and different properties, which may be advantageous in specific applications but do not provide the same combination of light output and detection efficiency as NaI (Tl