Verification of nuclear data for DT-neutron induced charged-particle emission reaction of light nuclei

Understanding of neutron induced charged-particle emission reactions is needed in the fusion reactor development especially when we strive toward a power generation plant. Emitted charged-particles cause material damage and a large amount of gas discharge. Moreover, a local nuclear heating occurs because the charged particles stop immediately in the material. Not only reaction cross section but also emission energy and angular differential information, namely double-differential cross section (DDX) is necessary to evaluate these physical quantities accurately. In particular, charged-particle emission DDX of first wall and blanket material highly exposed to incident neutron are indispensable. We recently developed an improved measurement technique for secondary emitted charged-particles using a pencil-beam neutron source. A systematic measurement is being carried out for light nuclei of which the measurement has not been performed sufficiently so far. We consider lithium, beryllium, carbon, oxygen, and fluorine as a high priority material for the measurement particularly since these are the composition materials of currently proposed fusion devices. The measurements for beryllium, carbon, and fluorine have already been completed and the measurement for Li-7 is planned at present. Obtained data in our measurement were compared with major three evaluated nuclear data libraries (JEFF-3.1, ENDF-B/VI, and JENDL-3.3). From the comparison, it is found that the evaluation of DDX for these materials is still insufficient in some libraries. The summary of the comparison study is the following: 1) As for beryllium, DDX for α-particle is stored in all libraries, and the agreement of the obtained result with ENDF is comparatively well. 2) As for carbon, there is a discrepancy of about 20% in the evaluation of α-particle production cross section, and DDX for α-particle is not stored in any libraries. 3) As for fluorine, the discrepancy of about 25% of proton production cross section is seen among the libraries, and our measurement supports the evaluation of ENDF. A remarkable difference is observed for proton emission DDX between the obtained result and JENDL, although the detailed DDX is stored only in JENDL. 4) As for Li-7, the total cross sections for triton production agree well with each other as expected, but the evaluations for other charged particles should be not enough. The verification based on the experiment in the future would be necessary. (author)