Researchers at Wake Forest University (Winston-Salem, NC) and Fisk University (Nashville, TN) have analyzed the crucial role that electron and hole mobilities have in strontium iodide crystals doped with europium that are used as scintillators (often with photomultiplier tubes) to detect gamma radiation. The results should lead to improved detection systems for screening cargo containers at ports, airports, and border crossings, as well as better radiation detectors for medical diagnostics.
Richard Williams of Wake Forest and his team used 500 fs pulses of light at a 210 nm wavelength to excite electron-hole densities of up to 2 × 1020 cm-3; the idea was to span the range of excitation densities produced along the track of an energetic electron in the scintillator crystal. The scintillation at each local excitation density encountered along the electron track was isolated and measured, leading to the knowledge that the effects of electron mobility affected the nonlinearity of the scintillation response. Strontium iodide is expensive, but the material already performs much better than the most affordable detectors currently used, say the researchers. They believe that with refinements to the fabrication process, crystals of the needed quality and size can be grown and produced affordably.
Contact Richard Williams at [email protected].
