纯碘化铯(CsI)晶体的发光与光衰减特性研究

Luminescence and Decay Time Properties of Pure CsI Crystals

纯碘化铯晶体是一种具有快衰减闪烁特性的新型辐射探测材料,在伽马射线、中子和其它辐射探测技术中有重要的应用前景。本研究以Bridgman法所生长的纯碘化铯为对象,分别研究了该晶体的透射光谱以及在紫外光、连续X射线、脉冲X射线和宇宙射线激发下的发射光谱、时间响应特性和沿晶体生长方向不同部位的光输出分布特点。实验测得晶体的吸收边为240 nm,激发和发射波长分别位于241 nm和318 nm,发光衰减时间分别为2~3 ns和18~25 ns。以尺寸为30 mm×30 mm×200 mm的晶体籽晶端和尾端与PMT耦合所测得的光输出分别是143 p.e/Me V和127 p.e./Me V,尽管晶体两端的光输出存在12.6%的差异,但没有观察到衰减时间长于100 ns的慢分量。这些性能进一步证明纯碘化铯晶体具有作为快闪烁体的优势。

Pure CsI crystal is a kind of fast scintillators which can be used to detect γ-rays, neutrons as well as other radiation. Optical transmission and luminescence properties of pure CsI crystal grown with Vertical Bridgman method were measured under the excitation of UV, continuous X-ray, pulse X-ray as well as cosmic rays at room temperature. Cut-off edge of the grown CsI crystal reaches 240 nm, which is the shortest among the literature reported previously. Excitation and emission wavelength are 241 nm and 318 nm, respectively. The decay times of the fast intrinsic luminescence can be fitted into two components, 2-3 nm and 18-25 nm under the excitation of X-ray or cosmic rays. The light outputs measured from the crystal with size of 30 mm×30 mm× 200 mm are 143 p.e/MeV and 127 p.e./MeV as its seed end and tail end were coupled with PMT, respectively. Even though the non-uniformity （12.6%） exists along the growth direction of the crystal, no significant slow component longer than 100 ns are observed. All of these properties prove that the pure CsI crystal is a promising fast scintillator.