Which isotope is used in nuclear gauges to determine asphalt content?

The isotope that is commonly used in nuclear gauges for determining asphalt content is Americium-241. This isotope emits alpha particles, which are particularly effective for measuring the density of materials such as asphalt. Nuclear gauges work by sending radiation into a material and detecting the radiation that is scattered or absorbed, allowing for an accurate measurement of specific components, like asphalt content, based on their density.

Americium-241 is favored in this context due to its suitable half-life and energy characteristics, which provide a stable source of radiation for the analysis required in asphalt mixtures. In addition to asphalt, Americium-241 can be utilized in other applications where density measurements are critical.

Knowing the practical applications of these isotopes in nuclear gauging helps understand the specific function and effectiveness of each one. Other isotopes listed have different applications or may not possess the optimal properties needed for asphalt content measurement, emphasizing why Americium-241 is the correct choice for this context.