Measurement of (n, f) and (n, xn) Cross Sections of Actinides with the Surrogate Reaction Method
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摘要: 对于某些中子反应截面，在直接测量上存在困难。为了获得那些对核能发展极其重要的核数据，人们提出替代反应法，即利用带电粒子代替中子进行反应，从而实现中子反应截面间接测量的方法。现有替代反应一般采用非弹激发、转移等周边反应，涉及的角动量远比中子反应的大，需要理论修正，这造成了一定的困难。有鉴于此，提出利用轻带电离子的俘获反应作为替代反应，其复合核自旋与中子反应的相当，有效避免了自旋修正的困难。根据这个思路，采用236U的（α，f）和（α，2n）反应作为替代反应，成功提取了239Pu的（n，f）和（n，2n）反应截面，与ENDFB7评价库数据在误差范围内符合较好，表明了替代反应法的优越性，可以在核数据测量中推广应用。
There are always difficulties in the direct measurement of reactions induced by neutron, in order to obtain the neutron induced nuclear reaction data which are extremely important for nuclear power development, the surrogate reaction method, which uses charged particles instead of neutron, was proposed. The existing surrogate reaction method generally chooses peripheral reaction as the surrogate reaction, such as inelastic scattering excitation or transfer reaction. As a result, the angular momentum involved is always far larger than the neutron induced reaction, which causes difficulties in the theoretical calculation. Because of this, we proposed to use light-ion capture reaction as the surrogate reaction, the compound nuclei spin is similar with that of the neutron induced reaction, so that the difficulties in spin correction can be effectively avoided. Based on this idea, the 239Pu(n, f) and (n, 2n) reaction cross sections were successfully extracted using 236U(α,f) and (α,2n) reactions as the surrogate reaction. The results coincide well with the data of ENDFB7 within the error range, which shows that the surrogate reaction method has its own superiority, and it can be applied in the measurement of nuclear data.Abstract: There are always difficulties in the direct measurement of reactions induced by neutron, in order to obtain the neutron induced nuclear reaction data which are extremely important for nuclear power development, the surrogate reaction method, which uses charged particles instead of neutron, was proposed. The existing surrogate reaction method generally chooses peripheral reaction as the surrogate reaction, such as inelastic scattering excitation or transfer reaction. As a result, the angular momentum involved is always far larger than the neutron induced reaction, which causes difficulties in the theoretical calculation. Because of this, we proposed to use light-ion capture reaction as the surrogate reaction, the compound nuclei spin is similar with that of the neutron induced reaction, so that the difficulties in spin correction can be effectively avoided. Based on this idea, the 239Pu(n, f) and (n, 2n) reaction cross sections were successfully extracted using 236U(α,f) and (α,2n) reactions as the surrogate reaction. The results coincide well with the data of ENDFB7 within the error range, which shows that the surrogate reaction method has its own superiority, and it can be applied in the measurement of nuclear data.-
Key words:
- neutron reaction /
- surrogate reaction /
- capture reaction /
- (n,f) cross section /
- (n,2n) cross section
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