ZINC SULFIDE AS A SPECT SCINTILLATOR

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Zinc sulfide has long been known as an efficient scintillator: it was used in powder form by Rutherford for detection of alpha particles and continues to be used for that purpose. Under beta stimulation it is also superior: it is the universal blue phosphor of television screens. Powder scintillators, however, are unsatisfactory for gamma ray detectors because the thickness of powdered material needed to absorb gamma rays scatters the generated light so efficiently as to be virtually opaque. If zinc sulfide could be grown in the form of large transparent boules, it would permit gamma ray detection with high efficiency, particularly in the 80-300 keV range required for Single Photon Emission Computed Tomography (SPECT). We have developed a process for growth of large transparent boules of high band gap II-VI compounds. Preliminary results show that our undoped zinc sulfide boules are luminescent under UV stimulation. We propose to investigate growth of silver-doped zinc sulfide, aiming at maximum boule transparency and efficiency under gamma ray stimulation. We already have a commercial supporter, one of the leading companies in the scintillation field, that is eager to evaluate our boules with the object of commercial applications.