Most of the gamma-ray imaging systems existing today use position sensitive scintillators, which have good efficiency, but lack good energy resolution, and their position resolution decreases significantly with increasing energy. LLNL has demonstrated methods that will help improve the resolution and sensitivity of Compton imagers using cyrogenically-cooled, position-sensitive semiconductor detectors.


LLNL is developing a highly-sensitive compact Compton imaging technology with excellent energy resolution, good imaging performance and large field-of-view. This system is built of large-volume and high-resolution Si(Li) and HPGe detectors. These detectors are built in double-sided strip configurations providing excellent three-dimensional position resolution. The system can measure individual gamma-ray interactions and determine interaction sequences through gamma-ray tracking algorithms.


LLNL’s system will enable real-time imaging of radioactive sources. With further development, we envision a scalable Compton imaging module. A moderate-sized array of such modules would extend the detection range to 30-50 m, while a large array may extend detection to 100 m.

Potential Applications

The methods will increase the image resolution and sensitivity of gamma-ray imaging systems used for national security, military, and medical imaging applications. In particular, gamma-ray imagers are important in surveillance, monitoring, and search applications (i.e., stand-off detection). NOTE: LLNL’s Compton Imaging technology is only available nonexclusively in the field of use for Security Imaging and Materials Imaging for Fissionable and/or Radioactive Materials.

Development Status

LLNL has developed excellent performance of a second-generation, hybrid Compton imaging system built using two Si(Li) detectors in a single cryostat and two HPGe detectors in a single cryostat. As such, significant steps have been taken to address physics and engineering challenges associated with Compton imaging. LLNL has an extensive portfolio of patents covering its Compton Imaging technology.

6,724,782 Femtosecond Laser-Electron X-ray Source 6,804,045 Optical Chirped Beam Amplification and Propagation 8,068,522 Hyper-dispersion Pulse Compressor for Chirped Pulse Amplification Systems 7,564,241 Isotopic Imaging via Nuclear Resonance Fluorescence with Laser-based Thomson Radiation 8,369,480 Dual Isotope Notch Observer for Isotope Identification, Assay and Imaging with Mono-Energetic Gamma-Ray Sources 8,934,608 High Flux, Narrow Bandwidth Compton Light Sources via Extend Laser-Electron Interactions 9,166,355 Directly Driven Source of Multi-Gigahertz, Sub-Picsecond Optical Pulses

US Patent Application: 14/274348 Modulated, Long-Pulse Method for Efficient, Narrow-Bandwidth, Laser Compton X-ray and Gamma-ray Sources

Foreign Patent Applications: Six in process

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