Verification of the surrogate ratio method
Verification of the surrogate ratio method
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替代比率法的验证
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
O. Iwamoto
中科院分区：
文献类型：
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作者：
S. Chiba;O. Iwamoto
研究了自旋和宇称分布差异对替代反应和中子诱发反应的影响。在不假设具体（示意性）自旋宇称分布，发现替代比方法可以用来确定中子裂变和俘获截面，如果（1）弱Weisskopf-Ewing条件（2）存在两个衰变核的自旋宇称分布几乎相等的替代反应，（3）中子诱发反应和替代反应的代表性自旋值之差不超过10 ensuremath {hbar}$。如果满足这些条件，我们不需要知道替代方法填充的自旋宇称分布。相反，我们应该只选择一对替代反应，这将填充类似的自旋宇称分布，使用具有类似结构的靶和具有类似反应机制的反应。对于铀区域的核，裂变和俘获通道的可测量精度估计分别为5%和10%。替代绝对法在测量裂变截面时应慎重。然而，将这种方法应用于俘获截面测量的希望不大，除非中子诱导反应和替代反应中的自旋宇称分布彼此相当接近（这是不可能的），或者可以从理论上校正这种差异。替代比方法也被证明是一个强大的方法，在破碎反应的存在下，不假设特定的破碎反应机制。
Effects of difference in the spin and parity distributions for the surrogate and neutron-induced reactions are investigated. Without assuming specific (schematic) spin-parity distributions, it was found that the surrogate ratio method can be employed to determine neutron fission and capture cross sections if (1) weak Weisskopf-Ewing condition (defined in this paper) is satisfied, (2) there exist two surrogate reactions whose spin-parity distributions of the decaying nuclei are almost equivalent, and (3) difference of the representative spin values between the neutron-induced and surrogate reactions is no much larger than $10ensuremath{hbar}$. If these conditions are satisfied, we need not know the spin-parity distributions populated by the surrogate method. Instead, we should just select a pair of surrogate reactions which will populate the similar spin-parity distributions, using targets having similar structure and reactions having the similar reaction mechanisms. Achievable accuracy is estimated to be around $5%$ and $10%$ for fission and capture channels, respectively, for nuclei of the Uranium region. The surrogate absolute method may be applicable to determination of fission cross sections with a caution. However, there will be little hope to apply this method for capture cross section measurements unless the spin-parity distributions in the neutron-induced and surrogate reactions are fairly close to each other (which is implausible) or the difference can be corrected theoretically. The surrogate ratio method was shown also to be a robust method in the presence of breakup reactions without assuming specific breakup reaction mechanisms.