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1、Evaluation the relative emission probabilities for 56Co and 66Ga,Yu Weixiang Lu Hanlin Huang XiaolongChina Nuclear Data CenterChina Institute of Atomic Energy, P.O. Box 275(41), Beijing 102413, Chinae-mail: ,Measurement:,A 136cm3 coaxial Ge(Li) detector connected to an ORTEC-919 data acquisition sys
2、tem operating on a PC is used in present work. Spectra were recorded by the front face of the detector 17.5cm far from the source,Full-energy peak efficiency,In the energy range from 100 to 2754keV, the primary standard radioactive sources with well-known activities were used to calibrate the absolu
3、te efficiencies of Ge(Li) detector. For example 24Na, 60Co, 54Mn, 65Zn, 137Cs and 133Ba were used to calibrate the efficiency curve in this region. At the same time, a mixed 125Sb+154Eu+155Eu multi-energy source produced by National Institute of Standards & Technology (NIST) with uncertainties in 0.
4、6%-1.3% was used. The I values used in the calibration were taken from the Table of Isotopes, Eighth Edition. The uncertainties (one standard deviation) of these sources are about 0.6-1.3%. The uncertainties of full-energy peak efficiency curve are about 1-2% in this region.,Full-energy peak efficie
5、ncy,Above 2754keV, there are no radioactive sources suitable for efficiency calibration. Therefore, nuclear reactions are commonly used. In present work, the efficiency curve is obtained by the calculated results using the EGS4 M-C code above 2754MeV, and calibrated at 6.13MeV using 19F(p,)16O react
6、ion at resonance energy point Ep=340keV.,Full-energy peak efficiency,Full-energy peak efficiency,Measurement:,By using the efficiency curve measured above，the new relative intensities were determined for the emitted -rays of 56Co and 66Ga. The final results are presented in Table 2 and 3, respective
7、ly. Its noted that our measurements are about 2% lower than other new measurements in high energy range.,Measured relative -ray intensities for 56Co,Measured relative -ray intensities for 66Ga,Standards -ray emission probabilities for 14N(n,)15N reaction,The main measurements of the -ray emission pr
8、obabilities for 14N(n,)15N reaction are T.J.Kennett et al., E.T.Jurney et al., H.Takayama and T.Belgya. The main difference among these measurements are from the level scheme. For example, the levels are 15, 19, 19 and 17, respectively and -rays are 28, 58, 64 and 55, respectively corresponding to t
9、hese measurements. Fig. 3 shows the comparison of the -ray emission probabilities. Its easy to find that the measurements of H.Takayama and E.T.Jurney et al. are in good agreement in 1.7-6MeV energy region. But the ratio of the -ray emission probabilities for Kennett/Jurney and Belgya/Jurney are exa
10、ctly reverse(see Fig.4).,Standards -ray emission probabilities for 14N(n,)15N reaction,Standards -ray emission probabilities for 14N(n,)15N reaction,Standards -ray emission probabilities for 14N(n,)15N reaction,From Fig.4 its easy to find that the measurements of Kennett are higher about 1.2% to 3.7
11、% than Jurneys in 2.54MeV and 68MeV range. To average of these two measurements simplely is not suitable for the standard for detector efficiency calibration. About 58 -rays were observed in the measurements of Jurney, but only 30 -rays of Kennett. In order to keep the intensity balance(I(in-out), t
12、he measured -ray emission probabilities of Kennett should be higher than Jurneys. We think that the -ray emission probabilities of Jurney are better than Kennett because the level scheme of Jurney is reasonable and complete.,Correction,G.Molnar calibrated the detector efficiency curve using 14N(n,)1
13、5N reaction, in which their -ray emission probabilities were from the measurements of T.J.Kennett et al. S.Raman calibrated the detector efficiency curve using 14N(n,)15N reaction, in which their -ray emission probabilities were from the average of measurements of T.J.Kennett et al. and E.T.Jurney e
14、t al. So its necessary to correct the measurements of S.Raman and G.Molnar using the -ray emission probabilities of Jurney above 2.5MeV. In present work the level scheme suggested by Jurney is adopted to correct the -rays intensities of 56Co and 66Ga.,Previous evaluation I for 56Co,The decay data of
15、 56Co were evaluated based on 33 measured data sets from 1965 to 2002 years by C.M.Baglin et al. in 2004. Firstly several measured values are statistical outliers(about 11%) according to the Chauvenet criterion. Secondly the measured data relied on linear extrapolations of the efficiency on a log-lo
16、g plot above 3MeV were excluded. The rest measured data were processed by several evaluation methods: weight average(WM), limitation of relative statistical weight average(LWM), normalized residuals method(NR) and Rajeval method(RA). At the same time, the whole measured data, the whole measured data
17、 except the exceed Chauvenet criterion value, were also processed by these evaluation methods. The recommended values are obtained from one of these processed values according to authors judgments. Its easy to find that the final recommended data are evaluated based on the whole measured data below 2598keV and 8 data sets above 2598keV.,
