Measurements of neutron spallation cross sections of Co-59 and Cu-nat

Abstract

The neutron spallation cross sections were measured using quasi-monoenegetic neutrons in the energy range above 20 MeV. The experiments were performed at three cyclotron facilities of INS (Institute of Nuclear Study), TIARA (Takasaki Research Establishments, Japan Atomic energy Research Institute) and RIKEN (Institute of Physical and Chemical Research). The quasi-monoenergetic neutrons were produced by Li-7(p,n)Be-7 reaction. The neutron spectra were measured with the TOF (Time Of Flight) method using an organic liquid scintillator. The absolute neutron fluence was determined with the PRT (Proton Recoil counter Telescope) at TIARA and further with the Li activation method to detect the Be-7 activity from the Li-7(p,n)Be-7 reaction at RIKEN. The irradiation samples were Cu-nat and Co-59, and were located at 400 cm and 837 cm behind the Li-target. The cross sections were obtained by dividing the reaction rate with the peak neutron fluence, which is given by PRT or Li activation method, after correcting the contribution of low-energy neutron components. The cross sections of the Co-59(n,xn)Co-58,57,56,55, Co-59(n,sp)Fe-59, Co-59(n,sp)Mn-56,54,52, Cu-nat(n,sp)Mn-56,54,52, Cu-nat(n,sp)Co-61,60,58,56,55, Cu-nat(n,xn)Cu-64,61,60 and Cu-nat(n,sp)Ni-65 reactions were measured as a function of neutron energy.

20MeV以上のエネルギー領域の準単色中性子を用いて中性子破砕断面積を測定した。実験はINS(原子核研究所)、TIARA(日本原子力研究所イオン照射研究施設)、RIKEN(理化学研究所)の3の研究施設で行った。準単色中性子はLi-7(p,n)B-7反応により生成した。中性子スペクトルは有機液体シンチレータを用いてTOF(飛行時間)法により測定した。中性子フルエンスの絶対量はTIARAにおいてはPRT(陽子反跳型カウンターテレスコープ)により決定し、RIKENにおいてはLi-7(p,n)Be-7反応からのBe-7活性を検出するLi放射化法により決定した。照射サンプルはCu-natとCo-59でそれぞれLi標的の後方400cmと837cmの位置に置いた。断面積は低エネルギー中性子成分の寄与の補正を行った後、PRTやLi放射化法より与えられた中性子フルエンスのピーク値で反応率を割ることにより得られた。Co-59(n,xn)Co-58,57,56,55、Co-59(n,sp)Fe-59、Co-59(n,sp)Mn-56,54,52、Cu-nat(n,sp)Mn-56,54,52、Cu-nat(n,sp)Co-61,60,58,56,55、Cu-nat(n,xn)Cu-64,61,60、Cu-nat(n,sp)Ni-65反応の断面積が中性子エネルギーの関数として得られた。