Characterization of the radiation hardness of PbWO4 crystals for the POKER calorimeter

For the construction of the POKER calorimeter, some PbWO4 crystals were purchased by Crytur. All the crystals were characterized in terms of radiation hardness at the Strahlenzentrum facility at Gießen (Germany). The test evaluates the damage induced by the crystals' exposure to an intense gamma source (constituted by an array of 60Co sources). Longitudinal optical transmittance was measured before and after the exposure, to quantify the damage. This dataset contains the data of the radiation hardness measurements performed on two sets of PbWO4 crystals: one including 20x20x220 mm^3 crystals and the other one including 20x20x200 cm^3 crystals. The files are in csv format and divided by data taking days (the legend can be found in the file Cristalli.csv). Each csv file shows two columns for each crystals: one with the wavelength and one with the correspondent Transmittance. Each crystal was measured at least twice (before and after the exposure), and the measurements are labeled with the crystal code and the label "before" or "after". Some measurements were repeated (and then the measure is labeled with a corresponding number) to evaluate the systematics. From this dataset it is possible to calculate a parameter, dk, which quantifies the radiation damage. It is defined as d = L^-1 * ln(Tbef/Taf), where L is the crystals length, Tbef is the transmittance before the exposure and Taf is the transmittance after the exposure). To calculate the parameter, some fits were performed in a small wavelength range (415-425 nm), since the wavelength of our interest is 420 nm. This is done trough the attached code, called "dk_analysis.py", which is a python-based macro.为搭建POKER量能器，Crytur公司采购了一批钨酸铅（PbWO₄）晶体。所有晶体均在德国吉森的辐射中心（Strahlenzentrum）设施中完成了辐射硬度表征。本次测试通过将晶体暴露于由钴-60（⁶⁰Co）源阵列构成的强γ辐射源中，评估晶体所受的辐射损伤。通过在辐照前后测量晶体的纵向光透射率，实现对辐射损伤的量化。 本数据集包含两组钨酸铅晶体的辐射硬度测量数据：一组为20×20×220 mm³规格的晶体，另一组为20×20×200 cm³规格的晶体。所有数据文件均采用逗号分隔值（CSV）格式，按数据采集日期进行分组，分组说明详见Cristalli.csv文件。每个CSV文件为每颗晶体设置两列数据：一列对应波长，另一列对应相应的透射率。每颗晶体至少完成两次测量（辐照前后各一次），测量结果以晶体编号及标签“before”或“after”进行标注，分别代表辐照前与辐照后。为评估测量的系统误差，部分测量结果进行了重复测试，重复的测量结果会附带对应编号标签。 通过本数据集可计算得到用于量化辐射损伤的参数dk，其定义为：$d_k = L^{-1} cdot ln(T_{bef}/T_{af})$，其中$L$为晶体长度，$T_{bef}$为辐照前的透射率，$T_{af}$为辐照后的透射率。为计算该参数，需在415~425 nm的窄波长范围内进行拟合，这是因为本研究关注的特征波长为420 nm。该参数的计算过程可通过附件中的Python宏脚本“dk_analysis.py”完成。