Differential cross sections for the 40 Ca(n,\( \alpha_{{0}}^{}\)) , \( (n,\alpha_{1,2})\) and \( (n,\alpha_{3,4,5})\) reactions are measured at neutron energies of 4.0, 4.5, 5.0, 5.5, 6.0 and 6.5MeV using a double-section gridded ionization chamber and two CaF2 samples. Monoenergetic neutrons were produced through the 2 H(d, n)3 He reaction with a deuterium gas target. A BF3 neutron counter was utilized to normalize the neutron flux among different measurements. The absolute value of neutron flux was calibrated using a 238U sample. Angle-integrated cross sections for the 40 Ca(n,\( \alpha_{{0}}^{}\)) , \( (n,\alpha_{1,2})\) and \( (n,\alpha_{3,4,5})\) reactions are obtained from the integration of the differential data. Model calculations are performed using the TALYS-1.6 code and general agreement is achieved between measurements and calculations. Then the total 40Ca(n,\( \alpha\))37Ar cross sections are derived from the angle-integrated cross sections combined with the code calculations. Present results are compared with existing measurements and evaluations.

Using two (238)U samples placed in a gridded ionization chamber and a parallel-plate fission chamber, fluence of monoenergetic fast neutrons was determined. Four runs of measurements were performed. Analysis showed that although the neutron fluences for the two (238)U samples differ by 20-33 times in the present work, the fluences at the position of the sample in the gridded ionization chamber determined by the two ways are in agreement within experimental uncertainties.

We have measured the (149)Sm(n,α)(146)Nd cross section at 4.5, 5.0, 5.5, 6.0, and 6.5 MeV. Measurements were performed at the 4.5 MV Van de Graaff accelerator of Peking University with monoenergetic neutrons produced via the (2)H(d,n)(3)He reaction using a deuterium gas target. Alpha particles were detected with a double-section gridded ionization chamber having two back-to-back (149)Sm(2)O(3) samples attached to the common cathode. Absolute neutron flux was measured using a small (238)U fission chamber and monitored by a BF(3) long counter. These are the first reported cross sections for this reaction at these energies, except at 6.0 eV, where our new data are in good agreement with our earlier result. The present results help to much better constrain the (149)Sm(n,α)(146)Nd cross section in a region where its energy dependence is changing fairly rapidly and there are large differences between evaluated nuclear data libraries.

Nuclear reactions of Zn-64(n,alpha)Ni-61 anti Zn-67(n,alpha)Ni-64 are important because they are gas production reactions and zinc is a reactor constituent element with a significant fraction. But the cross section data of these reactions are scanty because the residual nuclei Ni-61 and Ni-64 are stable and the commonly used activation method is not feasible. In the present work, differential cross sections and angleintegrated cross sections were measured for the Zn-64(n,alpha)Ni-61 reaction at neutron energies of 2.5, 4.0, 5.0, 5.5, and 6.0 MeV and cross sections of the Zn-67(n,alpha)Ni-64 reaction were measured at 4.0, 5.0, and 6.0 MeV. A twin gridded ionization chamber was employed as alpha particle detector. Experiments were performed at the 4.5 MV Van de Graaff accelerator of Peking University. Monoenergetic neutrons of 2.5 MeV were produced through the T(p, n)He-3 reaction with a solid Ti-T target, and those of other energies were produced through the D(d,n)He-3 reaction with a deuterium gas target. Absolute neutron fluxes were determined through the U-238(n, f) reaction and a BF3 long counter was used as the neutron flux monitor. Present results are compared with other measurements and evaluations.

Cross sections and forward/backward ratios in the laboratory reference system were measured for Nd-143(n, alpha)Ce-140 at, 4.0, 5.0, and 6.0 MeV, Sm-147(n, alpha)Nd-144 at 5.0 and 6.0 MeV, and Sm-149(n, alpha) Nd-146 at 6.0 MeV. A twin gridded ionization chamber and large-area back-to-back (Nd2O3)-Nd-143 and (Sm2O3)-Sm-147,149 samples were employed. Experiments were performed at the 4.5 MV Van de Graaff of Peking University, China. Fast neutrons were produced through the D(d,n)He-3 reaction by using a deuterium gas target. A small U-238 fission chamber was employed for absolute neutron flux determination and a BF3 long counter was used as neutron flux monitor. Present experimental data are compared with previous measurements, evaluations, and model calculations.

Cross sections of the 10B(n, α)7Li reaction (including the total, the "leaking" alpha, forward alpha and backward alpha parts) at En = 4.0 and 5.0 MeV were measured using an asymmetrical twin gridded ionization chamber and two back-to-back 10B samples. Measurements were performed at the 4.5 MV Van de Graaff accelerator of Peking University. Monoenergetic neutrons were produced through the 2H(d, n)3 He reaction with a deuterium gas target. Absolute neutron flux was determined by a 238U sample set inside the gridded ionization chamber and a BF3 long counter was employed as a neutron flux monitor and for normalization. The present results are compared with previous measurements and evaluations.

Experimental cross section data of the {sup 67}Zn(n,{alpha}){sup 64}Ni reaction are very scanty because the residual nucleus {sup 64}Ni is stable and the commonly used activation method is not feasible. As a result, very large deviations (about 10 times) exist among different nuclear data libraries. In the present work, cross sections of the partial {sup 67}Zn(n,{alpha}{sub 0}){sup 64}Ni and total {sup 67}Zn(n,{alpha}){sup 64}Ni reactions are measured at neutron energies of 4.0 and 5.0 MeV for the first time, and those of 6.0 MeV are remeasured for consistency checking. A twin-gridded ionization chamber was used as the charged-particle detector and two enriched back-to-back-set {sup 67}Zn samples were adopted. Experiments were performed at the 4.5 MV Van de Graaff Accelerator of Peking University. Neutrons were produced through the {sup 2}H(d,n){sup 3}He reaction using a deuterium gas target. Absolute neutron flux was determined by counting the fission fragments from a {sup 238}U sample placed inside the gridded ionization chamber while a BF{sub 3} long counter was employed as neutron flux monitor. Present data are compared with results of previous measurements, evaluations, and talys code calculations.

Experimental cross section data of the {sup 67}Zn(n,{alpha}){sup 64}Ni reaction are very scanty because the residual nucleus {sup 64}Ni is stable and the commonly used activation method is not feasible. As a result, very large deviations (about 10 times) exist among different nuclear data libraries. In the present work, cross sections of the partial {sup 67}Zn(n,{alpha}{sub 0}){sup 64}Ni and total {sup 67}Zn(n,{alpha}){sup 64}Ni reactions are measured at neutron energies of 4.0 and 5.0 MeV for the first time, and those of 6.0 MeV are remeasured for consistency checking. A twin-gridded ionization chamber was used as the charged-particle detector and two enriched back-to-back-set {sup 67}Zn samples were adopted. Experiments were performed at the 4.5 MV Van de Graaff Accelerator of Peking University. Neutrons were produced through the {sup 2}H(d,n){sup 3}He reaction using a deuterium gas target. Absolute neutron flux was determined by counting the fission fragments from a {sup 238}U sample placed inside the gridded ionization chamber while a BF{sub 3} long counter was employed as neutron flux monitor. Present data are compared with results of previous measurements, evaluations, and talys code calculations.

We have measured the Sm-149(n,alpha)Nd-146 cross section at 6.0 MeV to be 0.12 +/- 0.018 mb. This is the first reported result for this cross section in the MeV region and so should be helpful for constraining nuclear data evaluations (which differ by a factor of 40 for this reaction at this energy) and for testing and improving nuclear models. The experiment was performed at the at the 4.5-MV Van de Graaff accelerator of Peking University. Neutrons were produced via the H-2(d,n)He-3 reaction using a deuterium gas target, and absolute neutron flux was determined with a small U-238 fission chamber. Alpha particles were detected using a two-section gridded ionization chamber in which two large-area (Sm2O3)-Sm-149 samples were placed back-to-back so that the cross section and forward/backward ratio were measured for nearly the entire 4 pi solid angle. The data were compared to statistical-model predictions using the code TALYS. Good agreement between the measured and theoretical cross sections could be obtained with a small modification of the alpha-optical potential parameters from their default values in TALYS. However, we were not able to reproduce the measured forward/backward ratio. In addition, using the previously reported Sm-147(n,alpha)Nd-144 cross section at 6.0 MeV together with our new result, good agreement was found between the measured and predicted cross-section ratio for these two isotopes. Finally, none of the existing evaluated data libraries are in agreement with our new data to within the experimental uncertainties.

Measurements of cross sections of the (95)Mo(n, alpha)(92)Zr reaction at E(n)=4.0, 5.0 and 6.0MeV were carried out at the 4.5MV Van de Graaff of Peking University, China. A twin gridded ionization chamber and two large-area (95)Mo samples were adopted. Fast neutrons were produced through the D(d, n)(3)He reaction by using a deuterium gas target. A small (238)U fission chamber was employed for absolute neutron flux determination. Present data are compared with existing evaluations and measurement.

Cross sections and forward/backward ratios in the laboratory reference system were measured for 143Nd(n, )140Ce reaction at 4.0, 5.0 and 6.0 MeV and for 147Sm(n, )144Nd reaction at 5.0 and 6.0 MeV. A twin-gridded ionization chamber and large area back-to-back 143Nd2O3 samples and 147Sm2O3 samples were employed. Experiments were performed at the 4.5 MV Van de Graaff of Peking University, China. Fast neutrons were produced through the D(d, n)3He reaction by using a deuterium gas target. A small 238U fission chamber was employed for absolute neutron flux determination and a BF3 long counter was used as neutron flux monitor. Present experimental data are compared with previous measurements, evaluations, and model calculations.

Cross sections and forward/backward ratios in the laboratory reference system were measured for the $^{143}\mathrm{Nd}(n,\ensuremath{\alpha})^{140}\mathrm{Ce}$ reaction at 4.0, 5.0, and 6.0 MeV and for the $^{147}\mathrm{Sm}(n,\ensuremath{\alpha})^{144}\mathrm{Nd}$ reaction at 5.0 and 6.0 MeV. A twin-gridded ionization chamber and large-area back-to-back $^{143}\mathrm{Nd}{}_{2}{\mathrm{O}}_{3}$ samples and $^{147}\mathrm{Sm}{}_{2}{\mathrm{O}}_{3}$ samples were employed. Experiments were performed at the 4.5 MV Van de Graaff accelerator of Peking University, China. Fast neutrons were produced through the $^{2}\mathrm{H}(d,n)^{3}\mathrm{He}$ reaction by using a deuterium gas target. A small $^{238}\mathrm{U}$ fission chamber was employed for absolute neutron flux determination, and a ${\mathrm{BF}}_{3}$ long counter was used as the neutron flux monitor. Present experimental data are compared with previous measurements, evaluations, and model calculations.