Objective
Provide a mobile system for the stand-off detection, identification, and localization of radioactive materials for the detection of hidden special nuclear materials.
The system was required to detect a 1 milliCurie source in 20 seconds at 100 meters and provide isotope identification and 3-D localization to 10 meters with at most one false positive for every 8 hours of observations.

Approach
The Mobile Imaging and Spectroscopic Threat Identification (MISTI) system was designed and built for DHS/Domestic Nuclear Detection Office. It consists of a hybrid system with two separate gamma-ray detection instruments.

  • An array of 28 High Purity Germanium (HPGe) detectors provides excellent spectroscopy and unique isotope identification
  • An array of sodium iodide detectors combined with a coded aperture provide two dimensional gamma-ray imaging
  • By combining many 2-D images using GPS position and pointing, three-dimensional source positions are derived
Top Left: gamma-ray counts vs Energy (keV) spectrum showing typical background (blue) and line of interest (red), as measured with HPGe detectors. Middle and Bottom Left: front and top view of reconstructed gamma-ray position (red box) overlaid on optical images. Right: photograph showing gamma-ray detection system.
Top Left: gamma-ray counts vs Energy (keV) spectrum showing typical background (blue) and line of interest (red), as measured with HPGe detectors. Middle and Bottom Left: front and top view of reconstructed gamma-ray position (red box) overlaid on optical images. Right: photograph showing gamma-ray detection system.

Deliverable/Value/Accomplishment

  • NRL built, integrated, and tested system in 24 months
  • NRL delivered system to DNDO on schedule and under budget
  • MISTI fully met original sponsor requirements
  • At Sponsor direction: NRL transitioned MISTI to DOE in October 2011; will also be using variants of MISTI for background measurement campaigns in the future