  Scintillators play an important role in radiation detection and imaging.
Thallium-doped cesium iodide (CsI:Tl) and sodium iodide (NaI:Tl) are two of the
major scintillators that have been used for many applications for many decades.
In this paper we will present an improved scintillation performance of Bridgman
method grown CsI(Tl) and NaI(Tl) crystals developed by Xtallized Intelligence,
Inc. (XI, Inc.) and we will compare the performance with commercially available
CsI:Tl and NaI:Tl. In a preliminary testing using MicroFJ-60035-TSV silicon
photomultipliers (ON Semiconductor), the newly developed and improved
12.5x12.5x6 mm3 CsI:Tl crystal has shown an energy resolution of 4.8% (FWHM) at
662 keV, compared to 7.2% obtained by a commercially available CsI:Tl with a
size of 12.5x12.5x25 mm3. Energy resolution of 5.4% (FWHM) at 662 keV is
obtained for the newly improved NaI:Tl crystal, compared to 7% obtained by a
commercially available 1 in. dia. x 1 in. NaI(Tl). Comparison of the photo peak
channel locations shows that the improved CsI:Tl and NaI:Tl developed by XI,
Inc. have produced much larger signal amplitudes when compared to the
commercially available CsI(Tl) and NaI:Tl. Improved decay time constants are
presented as well.
