Detection of nuclear weapons and special nuclear material (SNM, certain types of uranium and plutonium) is crucial to thwarting nuclear proliferation and terrorism and to securing weapons and materials worldwide. Congress has funded a portfolio of detection R&D and acquisition programs, and has mandated inspection at foreign ports of all U.S.-bound cargo containers using two types of detection equipment. Nuclear weapons contain SNM, which produces unique or suspect signatures that can be detected. It emits radiation, notably gamma rays (high-energy photons) and neutrons. SNM is very dense, so it produces a bright image on a radiograph (a picture like a medical x-ray) when x- rays or gamma rays are beamed through a container in which it is hidden. Using lead or other shielding to attenuate gamma rays would make this image larger. Nuclear weapons produce detectable signatures, such as radiation generated by or a noticeable image on a radiograph. Other detection techniques are also available. Nine technologies illustrate the detection portfolio: (1) A new scintillator material to improve detector performance and lower cost. (2) GADRAS, an application using multiple algorithms to determine the materials in a container by analyzing gamma-ray spectra. If materials are the eyes and ears of detectors, ...