137 Cs γ射线空气比释动能率的国际关键比对

摘要

For the establishment of γray air kerma primary standard in 137 Cs and making it achieve the international equivalent ,a direct comparison for 137 Cs air kerma was car‐ried out in the 137 Cs radiation field of Bureau International des Poids et Mesures (BIPM ) between the National Institute of Metrology (NIM) and BIPM by using a graphite cavity ionization chamber .The comparison result is 0.996 7 with a combined standard uncer‐tainty of 0.21% .And an indirect comparison was also made using the same chamber calibrated by NIM and BIPM ,the result is 0.996 4 with a combined standard uncertain‐ty of 0.29% .The indirect comparison result is in good agreement with the direct com‐parison result and the relative error is about 3 × 10-4 .The results have been presented in BIPM key comparison database finally .%为建立我国137 Cs γ射线空气比释动能基准并使之达到国际等效，中国计量科学研究院（NIM ）采用石墨空腔电离室在国际计量局（BIPM ）137 Cs γ辐射场中开展了基准装置的直接比对，其比对结果为0畅9967，合成标准不确定度为0畅21％。同时采用校准同一电离室的方式开展了间接比对，得到的间接比对结果为0畅9964，合成标准不确定度为0畅29％，直接比对和间接比对相对偏差约为3×10－4，在不确定度范围内结果符合较好，该比对结果已进入国际计量局的关键比对数据库。