Tracking of γ rays

Tracking of γ rays

ORNL researchers have taken the lead in developing the "signal decomposition" algorithm for GRETINA. This algorithm uses digital signal processing to determine the positions and energies of gamma-ray interactions occurring in the germanium crystals that make up the detector. Dramatic progress has been made over the past year, as can be seen in the GRETINA newsletter, pages 6-9. An example of the precision with which positions can be determined is illustrated in fig. 1 which shows two-dimensional projections for a collimated beam of gamma rays from a ¹³⁷Cs source directed into one of the GRETINA detectors. The RMS widths of the position distribution are 1.5 mm and 1.7 mm, for X and Y respectively. These widths are not corrected for the finite width of the collimated beam.

Fig 1 - The two-dimensional projections of the interaction sites inside a Ge crystal of a pencil-like beam of γ-rays from a collimated ¹³⁷Cs source.

Gamma-ray imaging based on similar algorithms has the potential to allow high-sensitivity imaging of gamma-ray sources. This could find dramatic application to medical imaging, in both improved PET scanners and development of single-gamma imagers. It could also be used in homeland-security applications, for example in tracking radioactive sources and in cargo imaging.

References

^*See the GRETINA project for more information on GRETINA and its community.