4.5 Article

How Excitation Conditions Alter the Afterglow Characteristics of CsI:Tl,Sm Microcolumnar Films

期刊

IEEE TRANSACTIONS ON NUCLEAR SCIENCE
卷 66, 期 10, 页码 2229-2232

出版社

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/TNS.2019.2935878

关键词

Afterglow suppression; codoped; computed tomography; CsI:Tl; high-speed radiography; microcolumnar scintillator

资金

  1. U.S. Department of Energy [DOE SC0006329]

向作者/读者索取更多资源

Combining high light output with the microcolumnar structure, the CsI:Tl films significantly reduce the need for painful tradeoff between thickness (hence, stopping power) and spatial resolution. But both films and monocrystals share two important deficiencies that hinder their use in many high-speed imaging and computed tomography applications: a persistent afterglow and hysteresis. These properties receive the primary attention of this investigation. In our earlier work, we reported that codoping with Sm2+ brings about a significant reduction in the afterglow of CsI:Tl. Here, focusing on the microcolumnar films, we examine this afterglow-suppressive effect over a wide range of exposure times, from milliseconds to seconds, and at temperatures between 0 degrees C and 60 degrees C. Our measurements reveal well-defined dependences on both parameters. At room temperature (20 degrees C), defined as the normal operating condition, a 10-ms X-ray pulse leaves an afterglow from the standard (Sm-free) CsI:Tl of about 1% at 2 ms after the end of the pulse, changing little as a function of pulselength. Doping with Sm2+, however, reduces that afterglow by at least an order of magnitude, although somewhat less so after longer (100 and 1000 ms) pulses. When we change the temperature, however, we find markedly different behavior. Here, we find that a temperature increase of only 60 degrees, without changing the pulselength, cuts the afterglow of standard CsI:Tl films by a factor of 20. However, films of codoped CsI:Tl,Sm, whose afterglow has already been suppressed by the presence of Sm2+, show much less change as a function of either temperature or pulse duration. It is the presence of Sm2+ that makes the biggest difference. As for hysteresis, we again see an improvement, with the performance of the codoped CsI:Tl,Sm films bettering that of the standard (Sm-free) films. After an exposure of 300 mR, the change in light output falls to within 1% of the original after 1 min, whereas standard CsI:Tl films require 30 min to reach the same level.

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