What is the most common isotopic source used in gamma radiography?

The most common isotopic source used in gamma radiography is Iridium 192. This isotope is favored in industrial radiography primarily for its optimal combination of energy and half-life, which makes it highly effective for penetrating materials and producing high-resolution images of internal structures. Iridium 192 has a half-life of approximately 73.83 days, allowing it to maintain its intensity over a reasonable period, making it suitable for repeated use in radiographic inspections.

Moreover, the gamma radiation emitted by Iridium 192 is well-suited for imaging a variety of materials, including metals, which is critical in industries such as construction and manufacturing where weld integrity must be evaluated. Its energy level is also sufficient to provide clear images while minimizing the exposure to the radiographer, making safety considerations more manageable.

The other isotopes listed may have specific applications in different contexts, such as Technetium 99m being predominantly used in medical imaging, Radium 226 having historical significance but largely phased out due to safety concerns, and Cesium 137 also being used, but less widely than Iridium 192 in gamma radiography. Thus, Iridium 192 stands out as the most prevalent choice in the field.