^(173)Lu和^(174g)Lu衰变数据的测量

Measurements of Decay Data of ^(173)Lu and ^(174g)Lu

^(175)Lu(n,2n)^(174m,g)Lu(n,2n)^(173)Lu反应在高能中子通量监测中具有重要作用,其产物的放射性活度通常用HPGe探测器测量,这就需要^(174m,g)Lu和173Lu的半衰期和γ射线发射率等衰变数据必须准确无误。在主要的评价核数据库中,只有ENDF/B 7.1和JEFF 3.1.1数据库给出了^(173)Lu和^(174)Lu的半衰期和γ射线的发射几率等衰变数据,其中^(173)Lu的γ射线发射几率ENDF/B 7.1库比JEFF 3.1.1库总体偏高,其他评价数据两个数据库非常一致。在中国原子能研究院的串列加速器上用20 Me V质子辐照金属Yb靶生产了含有^(173)Lu,^(174m,g)Lu的放射性溶液,用激光共振电离质谱(LRIMS)和热表面电离质谱(TIMS)两种同位素稀释法测定了该溶液中173Lu和174m,gLu核素浓度,然后制备测量源在HPGe探测器上进行了近7年的跟踪测量,发现^(173)Lu的半衰期为1.45 a,比目前评价的数据1.37 a高6.1%,636.1 ke Vγ射线发射几率的偏差最大,比ENDF/B 7.1的评价数据偏高7%。^(174g)Lu半衰期的测量结果 3.37 a,比评价数据3.31 a高约1.8%,174gLu 76.5 keV和1 241.8 ke Vγ射线的发射几率比ENDF/B 7.1的评价数据分别低1.87%和12.8%。

175Lu（n,2n）174m,gLu（n,2n）173Lu are important neutron reactions to monitor the high energy neutron fluxes and the residual nuclei,174m,gLu and 173Lu, are usually measured by a HPGe spectrometer conveniently so that the decay data such as half lives and gamma-ray emission probabilities of 174m,gLu and 173 Lu must be accurate. There are evaluated decay data only in ENDF/B 7.1 and JEFF 3.1.1 among the major evaluated nuclear data libraries, where the most data are almost same besides the gamma-ray emission probabilities of173 Lu are higher in ENDF/B 7.1 than that in JEFF 3.1.1. Yb metal as a target was irradiated by 20 MeV proton beams on a tandem accelerator in CIAE to produce174 m,gLu and173 Lu, and176 Lu isotopic dilution methods based upon a laser resonance ionization mass spectrometer（LRIMS） and a thermal surface ionization mass spectrometer（TIMS） were employed to determine the numbers of nuclides of174 Lu and173Lu in a solution containing the irradiated target. Several radioactive sources made from the solution had been measured by a HPGe detector during the past 7 years and the peak intensities of the characteristic gamma-rays from 174gLu and 173Lu were analyzed to determine the half lives and gamma-ray emission probabilities. According to the measurements, the half life of173 Lu is 1.45 a, which is about 6.1% longer than the evaluated 1.37 a, and the gamma-ray emission probabilities of 173Lu is also different from the evaluated data, especially the emission probability of 636.1 ke V gamma-ray of 173Lu is 7% higher than the value in ENDF/B 7.1. The half life of 174gLu is 3.37 a, about 1.8%longer than the evaluated 3.31 a, and the emission probabilities of 76.5 ke V and 1 241.8 ke V gamma-rays of 174Lu are 1.87% and 12.8% lower than the evaluated data in ENDF/B 7.1, respectively.