1

Current Compton Imaging Effort for Homeland Security at LLNL

• Address one of the outstanding problems for Homeland Security: “Faint” sources in the midst of background fluctuations

• Gamma-ray imaging to provide Location and shape of nuclear materials Increased sensitivity in the detection of nuclear materials

(increase signal-to-background, distinguish threat sources from background fluctuations (spatially and temporarily)

• Compton imaging provides high sensitivity with large FOV (4) and w/o heavy collimators

• Cryogenically cooled, large-volume Si(Li) + HPGe detector in double-sided strip configuration provide high sensitivity throughout energy range of interest for DHS (180 keV – 2.6 MeV)

• Couple 4 Compton imager to 4visual photo/video camera

• Provide 3D imaging either in near field or by moving source or detector

344 keV

Imaging of extended 152 Eu source

2

Current Compton Imaging effort for Homeland Security at LLNL

• Current Compact Compton Imager

system consisting of 2 Si(Li) and 2

HPGe DSSDs

• 3D position determination by

combining 2D segmentation and

pulse-shape analysis

• 2D and 3D gamma-ray imaging

• Combining 3D gamma-ray and visual

images (LIDAR mapping system)

Si+Ge detectors

Photo camera

Dewar

Pre-amplifiers

20 cm

2D gamma-ray + 3D visual images 3D gamma-ray + 3D visual images

Example of signal shape fitting to deduce #, energies, and 3D position of interactions

3

Proposal to DNDO/NSF 07-545 (Academic Research Initiative) to evaluate electron-tracking based Compton imaging

• Reduce cone to arc without loosing angular resolution

• Concept of Si-Drift Detectors

4

Examples of measured electron tracks

Position Track

E/dx Vertex (origin of track)Complete vs. incomplete energy deposition

Particle identification?

5

Opportunities for UC

• 1m2-scale gamma-ray and neutron detectors and imagers to detect faint sources

• Electron-tracking based imagers, e.g. LAr …

• Gamma-ray imaging …

…. Connection to Biomedical Applications

(10th Campus UCSF…)