Comparison of semiconductor pixel array, phosphor plate, and track-etch detectors for alpha autoradiography
The need to locate "hot particles" during environmental radioactivity characterization benefits from autoradiography. Three detectors are compared for the evaluation of point-source alpha emitters. 238PuO 2 particles were used to compare a detector based on a pixel array, a phosphor imaging plate system, and a track-etch detector. The pixel-array detector is based on a charge injection device (CID) having nominally 14 μm sized pixels in a 7 mm × 9 mm array. Processing at a 30 frames per second rate allows real-time display of results. Background interference is minimal even in long-duration exposures. The phosphor imaging plate system is subject to background accumulation. Track overlap makes single-event discrimination and quantification impractical, but a large exposure area and ease of use are distinct advantages. A system having a pixel size of 50 μm was used. Track-etch detectors have the largest potential exposure area and best spatial resolution, the latter being limited by the amount of material etched, resolving power of the reading system, and the number of tracks recorded per source. Readout, however, can be time-consuming, and track overlap can make quantification difficult. The best apatial resolution, 10 μm, was obtained with the track-etch detector, with a precision in location of 1 μm. The phosphor plate system was capable of detecting 0.002 Bq sources in 2 d, whereas the track-etch and semiconductor pixel array were capable of detecting 0.0002 Bq sources in 2 d. The track-etch method was the most difficult, whereas the most rapid results were obtained with the real-time display of the semiconductor pixel array.