Accelerator Technology for Long Range Detection of Nuclear Material*

The Defense Threat Reduction Agency's (DTRA) mission is to safeguard the United States and its allies from global threats due to weapons of mass destruction. This mission requires the capability to detect from a distance nuclear material located in a target object, such as a ship, vehicle or building. One technique being explored to aid the longrange detection of nuclear material is active interrogation using beams of energetic photons, protons, or muons from an appropriate accelerator to stimulate detectable signatures on the target objects. Since the Department of Defense requires a capability to respond to situations anywhere in the world, accelerators used to generate particle beams for active interrogation must be extremely compact and transportable. They must also generate precise beams of sufficient quantity and energy with high efficiency. Limited budgetary resources require that research for evaluation of the military utility of active interrogation for detection of special nuclear material must make use of the most mature beam technologies. Electron linear accelerator (LINAC) technology and pulsedpower sources are being used to generate bremsstrahlung photon beams for active interrogation. Two beam-enhancement technologies continue to receive limited support. These are low- and medium-beta superconducting radio-frequency (SRF) accelerator cavities and thin multi-layer coatings to increase the accelerating gradient achievable in SRF cavities.