Americium

²⁴¹Am (with a half-life of 433 days) is used in smoke detectors as an ionization source to detect smoke (Fig. IUPAC.95.1). A small piece of ²⁴¹Am oxide is housed inside ionizing smoke detectors. The americium compound emits alpha particles that strike air molecules in their path, causing them to ionize. The ions carry a current from one plate in the detector to a second plate. Current flows continuously until smoke disrupts the current between the two plates. The alarm sounds when the current is disrupted by smoke [75], [614], [615]. ²⁴¹Am is used for the control and measurement of industrial material thickness and product quality. In manufacturing, for example, a small piece of ²⁴¹Am is placed above a conveyer belt and a Geiger counter (used to count alpha particles) is placed below the conveyor belt. A specific quantity of radiation is expected to be measured by the Geiger counter. If the product being manufactured (i.e. glass) is thicker than expected, less radiation will be measured, and the product will be rejected [75]. The gamma radiation of ²⁴¹Am is also used in a variety of gauges. Thickness gauges, fluid-density gauges, aircraft fuel gauges, and distance-sensing devices use the density-measuring capabilities of the emitting gamma rays and radiation detector to function. When ²⁴¹Am is mixed with beryllium (²⁴¹AmBe), it emits neutrons at a high rate. This high rate of neutron generation is useful in oil-well operations to monitor the rate of oil production, and it can also be used in well logging to log the porosity (fraction of void volume to total volume of a material) of the geologic units along the sides of a borehole. Gamma rays from ²⁴¹Am are also used as portable X-ray machines to determine where new wells should be drilled. When a small pellet of ²⁴¹Am is placed in a sealed titanium capsule, it can serve as a portable source for gamma radiography, which is more penetrating than X-rays, to test various materials for defects, such as invisible cracks or faulty welds in pipelines [75], [614], [616].

Gamma-ray emissions from ²⁴¹Am have been used as a radiation source for medical diagnostic tests. In particular, ²⁴¹Am has helped to provide accurate diagnoses of thyroid function, but this use of americium is now obsolete [617].