LaBr3晶体快定时性能的研究

Fast timing technique is widely applied in nuclei structure, nuclear reaction, nuclear medicine and nuclear astrophysics research areas, and so on. To be accompanied by the development of BaF2, LaBr3:Ce crystals with excellent timing, the radioactive half-life of the excited state could be measured to several picoseconds by means of the ultra-fast timing technique. At present, in the domestic nuclei structure experiment research, the excited state half-life can only be determined in hundreds of picoseconds via the slope method. In order to measure the excited state half-life in the range of a few picoseconds to dozens of picoseconds, a set of ultra-fast timing device will be developed to do research in the fast timing technique used in nuclei structure study. Compare to other scintillator crystals, LaBr3:Ce crystal has the state-of-the-art incomparable performance. It has the performances of high light output, short attenuation time, high energy resolution (< 3% FWHM) and excellent linear response in large dynamic energy range, perfect time resolution (100 ps FWHM), small performance variation affected by temperature, and so on. Therefore, LaBr3: Ce crystal will be used in the ultra-fast timing device. In this subject, with the help of the research in LaBr3:Ce, PMT and CFD timing performance and centroid-shift technique, a set of ultra-fast timing device will be developed to measure the ps scale of the excited state half-life, which helps the scientific researchers understand the nuclei structure and inspect nuclei models more intuitively and precisely.

快定时技术在核结构、核反应、核医学及核天体物理等研究领域都有很广泛的应用需求。随着BaF2、LaBr3:Ce等具有快衰减时间性能晶体的出现，利用超快定时技术能够测量短至几个ps的激发态寿命。目前，在国内核结构实验研究中，仅利用斜率法测量的激发态寿命在几百ps量级。为了测量寿命为几十-几ps的激发态，我们拟研制一套超快定时装置来研究快定时技术在核结构研究中的应用。LaBr3:Ce具有高光输出，短衰减时间，高能量分辨率（<3% FWHM）且在大动态围内线性响应好，时间分辨率高(100ps FWHM），性能受温度影响小等其它闪烁体难以比拟的性能。因此，拟研制的超快定时装置将采用LaBr3:Ce晶体。本课题，通过研究LaBr3:Ce、PMT和CFD的定时性能和重心移位技术，来研制一套超快定时装置，用来测量ps量级的激发态寿命，从而有助于科研人员更直观和准确的认识原子核结构和检验原子核模型。

快定时技术在核结构、核反应、核医学及核天体物理等研究领域都有很广泛的应用需求。随着BaF2、LaBr3:Ce等具有快衰减时间性能晶体的出现，利用超快定时技术能够测量短至几个ps的激发态寿命。目前，在国内核结构实验研究中，仅利用斜率法测量的激发态寿命在几百ps量级。LaBr3:Ce具有高光输出，短衰减时间，高能量分辨率（<3% FWHM）且在大动态围内线性响应好，时间分辨率高(100ps FWHM），性能受温度影响小等其它闪烁体难以比拟的性能。我们采用LaBr3:Ce晶体成功研制一了套超快定时装置，可以用它来测量核结构研究中寿命为几十ps到几百ps的激发态。快定时装置由尺寸为Φ40mm×25mm的LaBr3晶体和PMT XP20D0构成，该快定时装置对511keVgamma射线的符合时间分辨率约为220ps(FWHM)；对662keV gamma射线的能量分辨率为3.0%(FWHM)；结合斜率和中心移位技术测量152Eu的β+衰变子核152Gd的21+态的平均寿命为44.9±（5.1）ps，与其理论寿命46.7ps非常接近。因此利用该定时装置结合斜率和中心移位技术可以测量几十ps至几百ps范围内激发态的寿命，从而有助于科研人员更直观和准确的认识原子核结构和检验原子核模型。