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Co-Planar Electrodes for Radiation Detection

IB-1033

E.O. Lawrence Berkeley National Laboratory

APPLICATIONS OF TECHNOLOGY:

  • Environmental remediation
  • Radioactive waste monitoring
  • Diagnostic medical imaging
  • Nuclear safeguards
  • Industrial sensing
  • Materials analysis
  • All other applications that benefit from high resolution and highly position-sensitive gamma radiation detectors.

ADVANTAGES:

Berkeley National Laboratory's new coplanar electrode technique will improve performance in:

  • Room temperature compound semiconductor detectors
    This is the first charge sensing procedure that will enhance performance sufficiently to enable the fabrication of high resolution gamma-ray spectrometers.
  • Cryogenic Ge detectors
    Berkeley National Laboratory's technique will make cryogenic Ge detectors more radiation resistant
  • Gas and liquid ionization detectors
    Berkeley National Laboratory's coplanar electrodes will simplify fabrication of gas and liquid ionization detectors, making them less expensive to produce, more rugged, and more resistant to mechanical disturbances

ABSTRACT: Most ionization based radiation detectors--gas ion chambers, liquid ionization detectors, and compound semiconductor detectors--suffer from poor collection of charge carriers of one polarity type. As a result, detector energy resolution is severely degraded when a basic parallel electrode detector geometry is used. Traditionally, in gas and liquid detectors, a suspended grid electrode structure (Frisch grids) that preferentially senses the collection of one carrier type has been successfully employed to overcome this problem. However, this technique cannot be readily applied to semiconductor detectors because of difficulties in producing the required grid electrode structure inside the semiconductor crystals.

Paul Luke from Berkeley National Laboratory has developed a novel charge sensing technique that uses coplanar electrode structures in place of Frisch grids. Berkeley National Laboratory's new coplanar electrodes are easy to fabricate on semiconductor detectors, enabling good energy resolution despite poor hole collection. This enhancement of energy resolution is especially exciting for compound semiconductors such as CdTe, CdZnTe, HgI2 and GaAs. These detectors operate at room temperature and have long been under development as potential alternatives to expensive, cryogenic Ge gamma-ray detectors. Berkeley National Laboratory's new coplanar electrode technique will enhance room temperature semiconductor detector performance to levels that will make these detectors competitive, practical, high resolution spectrometers.

An additional feature of Berkeley National Laboratory's charge sensing technique is high position sensitivity, which results in the ability to perform imaging using simple pulse amplitude measurements. This is in contrast to conventional multi-element detector systems, which require a large number of space- and power-consuming amplifiers.

For the first time, Berkeley National Laboratory's new coplanar electrodes make it possible to produce room temperature semiconductor detectors with high resolution and high position sensitivity.

STATUS: U.S. Patent #5,530,249. Available for licensing

REFERENCE NUMBER: IB-1033

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