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A method for measuring (n,α) reaction cross sections of the gas sample induced by fast neutrons using a gridded ionization chamber (GIC) was established. There are several advantages using the GIC to measure gas samples. With this method, the (n,α) reaction cross sections of inert gases which are hard to exist as a solid can be measured. And the (n,α) reaction cross section for α particle emitting in all directions can be directly measured by using the gas sample. Furthermore, compared with using solid samples, using gas samples have far more nuclei in the measurement samples. Therefore, it is feasible to use neutron source with a better energy resolution to measure the resonance cross sections with gas sample. However, there are many problems to be solved when measuring (n,α) reaction cross section of gas sample by using the GIC. On the one hand, the nuclear reaction event will be affected by the wall effect, when the nuclear reaction is generated near the electrodes of the GIC or at the edge of the electric field. The wall effect will cause the measured event to locate outside the event area which cannot be counted. Not only is the number of nuclei of the gas samples involved in the (n,α) reaction difficult to determine, but the number of events, which are affected by the background or located below the threshold, is also difficult to count. On the other hand, the neutron fluence involved in the measurement of (n,α) reaction cross section of gas sample is difficult to measure. Aiming at solving the problems of the determination of the sample nuclei number, the measurement of neutron fluence, and the selection of events, which are all difficult for the gas sample, this method included three steps: First, simulation calculation was performed to select a suitable effective volume of the gas samples, so that the event is free of background and easy to be counted. Second, the neutron collimator and the timing information of cathode and anode signals were used to select and count the events generated in the effective volume of the gas sample. Third, combining the fission fragment measurement of the 238U(n,f) reaction and the simulation based on SuperMC, the neutron fluence through the effective volume was obtained. Measurements of relative cross sections of the 14N(n,α0) reaction using gas sample were performed at En=471, 487, 500, 512, 529, and 545 MeV. The results are in good agreement with those of ENDF/BⅧ.0 which verified the present measurement method.

With the rapid advancements in computer vision, using deep learning for strawberry disease recognition has emerged as a new trend. However, traditional identification methods heavily rely on manual discernment, consuming valuable time and imposing significant financial losses on growers. To address these challenges, this paper presents BerryNet-Lite, a lightweight network designed for precise strawberry disease identification. First, a comprehensive dataset, encompassing various strawberry diseases at different maturity levels, is curated. Second, BerryNet-Lite is proposed, utilizing transfer learning to expedite convergence through pre-training on extensive datasets. Subsequently, we introduce expansion convolution into the receptive field expansion, promoting more robust feature extraction and ensuring accurate recognition. Furthermore, we adopt the efficient channel attention (ECA) as the attention mechanism module. Additionally, we incorporate a multilayer perceptron (MLP) module to enhance the generalization capability and better capture the abstract features. Finally, we present a novel classification head design approach which effectively combines the ECA and MLP modules. Experimental results demonstrate that BerryNet-Lite achieves an impressive accuracy of 99.45%. Compared to classic networks like ResNet34, VGG16, and AlexNet, BerryNet-Lite showcases superiority across metrics, including loss value, accuracy, precision, F1-score, and parameters. It holds significant promise for applications in strawberry disease identification. [ABSTRACT FROM AUTHOR]

With more accurate measurement method for gas samples, cross sections of the 14N(n,α0,1)11B reactions were measured at 24 energy points in the 4.5–11.5 MeV neutron energy region based on the 4.5 MV Van de Graaff accelerator at Peking University and the HI-13 tandem accelerator of China Institute of Atomic Energy (CIAE). The average neutron fluence (Φ) through the gas sample was obtained through the combination of a highly enriched 238U3O8 sample and the simulation based on SuperMC. The cross sections of the 14N(n,α0)11B reaction measured using the gas sample and the solid samples are in agreement with each other. R-matrix analysis was carried out for the n + 14N system using code RAC in the neutron energy region below 30 MeV. A possible valley structure in both the excitation functions of the 14N(n,α0,1)11B reactions in the 10–11 MeV neutron energy region was found for the first time. [ABSTRACT FROM AUTHOR]

Accurate cross section of the 232Th(n, f) reaction are demanded in the design of advanced nuclear systems and in the development of fission theory. However, the existing measurement data are relatively sparse comparing with those of the 238U(n, f) reaction, with big uncertainties and obvious discrepancies. Furthermore, analysis shows that systematic deviations exist between the results measured with mono-energetic neutron sources and white neutron sources, which is the main reason for the differences among different evaluation libraries. This work is dedicated to the clarification of this discrepancy. Based on mono-energetic d-d neutron sources and using back-to-back Th/238U samples, cross section of the 232Th(n, f) reaction were measured at 12 energies in the 4.2–11.5 MeV region. Elaborated measures were taken in the measurement procedure including the exchange of the forward and the backward direction of the samples, as well as in the data processing containing the correction of interference fission counts from low-energy neutrons and the detailed Monte Carlo simulations for the determination of detection efficiencies for fission events. In addition, theoretical analysis was also performed using TALYS-1.9 and UNF codes. The present results agree with existing measurement data using white neutron sources, showing that previous cross section of the 232Th(n, f) reaction measured using mono-energetic neutron sources are systematically overestimated on average. The present results are in accordance with the latest measurement data of Michalopoulou et al., which is helpful in the improvement of nuclear data evaluations of the 232Th(n, f) reaction. [ABSTRACT FROM AUTHOR]