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Cross sections of the $^{12}$C(n, n+3α) reaction are of great significance in understanding the nuclear reaction mechanism and in the applications of nuclear technology. However, large differences (≈ 200%) exist in the $^{12}$C(n, n+3α) cross section data of measurements and evaluations. Using a single crystal chemical vapor deposited (sCVD) diamond detector as an active target, cross sections of the $^{12}$C(n, n+3α) and $^{12}$C(n, α0)9Be reactions were measured simultaneously in the neutron energy region of 9.50 – 14.67 MeV. The present cross sections of the $^{12}$C(n,α0)9Be reaction are consistent with the results of the latest measurement, which confirms the reliability of this work. The measurement results of the $^{12}$C(n, n+3α) reaction with uncertainties smaller than 15% contribute to effectively clarify the discrepancies of the measurements and evaluations. To our knowledge, this is the first time to measure the $^{12}$C(n, n+3α) cross sections using the diamond detector as an active target. Our method can be used in the future measurements to constrain the $^{12}$C(n, n+3α) excitation function in a much wider neutron energy region. R-matrix analysis was carried out for n+$^{12}$C system using the RAC code in the neutron energy region below 30 MeV. Systematic and reliable calculation results are obtained for various reaction channels.

The phoswich coincidence detector is used to verify the CTBT treaty by measuring radioxenon and as such needs to possess high detection sensitivity. However, residual xenon adsorbed onto the surface of β detectors greatly influences subsequent measurements of weak samples. In this study, we investigate the adsorption-desorption behavior of xenon on BC-404 scintillator surfaces with different coating thicknesses using the soaking method. The results present the desorption behavior of xenon on a BC-404 surface for the first time. The calculated adsorption capacity for an uncoated surface is consistent with that from previous studies. However, due to factors such as limitations in coating technology, the effectiveness of coating on reducing the “memory effect” of the detector was poor. The proposed method is suitable for studying the adsorption-desorption behavior of gases on solid surfaces due to its simplicity and flexibility.

A single crystal chemical vapor deposition (scCVD) diamond detector has been successfully employed for neutron measurements in the EAST (Experimental Advanced Superconducting Tokamak) plasmas. The scCVD diamond detector coated with a 5 μm 6LiF (95% 6Li enriched) layer was placed inside a polyethylene moderator to enhance the detection efficiency. The time-dependent neutron emission from deuteron plasmas during neutral beam injection (NBI) heating was obtained. The measured results are compared with that of fission chamber detectors, which always act as standard neutron flux monitors. The scCVD diamond detector exhibits good reliability, stability and the capability to withstand harsh radiation environments despite its low detection efficiency due to the small active volume.

A 2" × 2" BC501A liquid scintillation detector with a gain stabilization system is developed and applied to neutron and γ-ray measurement on the EAST tokamak. Energy calibration of a liquid scintillator using a fast coincidence method is presented and compared with the Monte Carlo simulation. Determination of the proton light output function of the BC501A is presented. Results from dedicated experiments with an Am-Be neutron source, γ source and quasi-monoenergetic neutron beams, and from measurements on EAST tokamak are presented and discussed.

The influence of an inert gas bubble inside EJ301 cylindrical cell on the response of the liquid scintillation detector to γ-rays and neutrons has been investigated. It is found experimentally that the response of the detector to radiation varies with the detector placement styles. The explanation proposed in this article is that this variation arises from the change of the light transmission process induced by the motion of the inner gas bubble. This assertion has been supported by the simulations of both radiation energy deposition and light transmission process inside the detector with the GEANT4 code. For the recommended detector placement style when the detector is placed horizontally, the variation of the response is smaller than 1.56%, which will increase to about 22% when the detector is placed facing down and the bubble lies between the scintillator and photomultiplier tube.

Neutron energy spectrometry diagnosis plays an important role in magnetic confinement fusion. A new neutron time-of-flight (TOF) spectrometer with double scintillators is designed and optimized for the EAST tokamak. A set of optimal parameters is obtained by Monte Carlo simulation, based on the GEANT4 and ROOT codes. The electronic setup of the measurement system is designed. The count rate capability is increased by introducing a flash ADC. The designed spectrometer with high resolution and efficiency is capable of being applied to fusion neutron diagnostics. Applications in mixed-energy and continuous energy neutron fields can also be considered.

An accurate energy calibration of a 5'' × 2'' BC501A liquid scintillator-based neutron detector by means of photon sources and the unfolding of pulse height spectra are described. The photon responses were measured with 22Na, 137Cs and 54Mn photon sources and simulated using the GRESP code, which was developed at the Physikalisch Technische Bundesanstalt in Germany. Pulse height spectra produced by three different photon sources were employed to investigate the effects of the unfolding techniques. It was found that the four unfolding codes of the HEPRO and UMG3.3 packages, including GRAVEL, UNFANA, MIEKE and MAXED, performed well with the test spectra and produced generally consistent results. They could therefore be used to obtain neutron energy spectra in tokamak experiments.

An attempt is made to improve the evaluation of the prompt fission neutron emission from 233U(n, f) reaction for incident neutron energies below 6 MeV. The multi-modal fission approach is applied to the improved version of Los Alamos model and the point by point model. The prompt fission neutron spectra and the prompt fission neutron as a function of fragment mass (usually named "sawtooth" data) υ(A) are calculated independently for the three most dominant fission modes (standard I, standard II and superlong), and the total spectra and υ(A) are synthesized. The multi-modal parameters are determined on the basis of experimental data of fission fragment mass distributions. The present calculation results can describe the experimental data very well, and the proposed treatment is thus a useful tool for prompt fission neutron emission prediction.

Low energy neutron induced fission of 235U is studied in the framework of the multi-modal fission model. The fission fragment properties, such as the yields, the average total kinetic energy distribution and the average neutron separation energy, are investigated for incident neutron energies from thermal to 6.0 MeV. The multi-modal fission approach is also used to evaluate the prompt fission neutron multiplicity and spectra for the neutron-induced fission of 235U with an improved version of the Los Alamos model for incident neutrons below the (n, nf) threshold. The three most dominant fission modes are taken into account. The model parameters are determined on the basis of experimental data. The calculated results are in good agreement with the experimental data.

The improved version of Los Alamos model with the multi-modal fission approach is used to analyse the prompt fission neutron spectrum and multiplicity for the neutron-induced fission of 237Np. The spectra of neutrons emitted from fragments for the three most dominant fission modes (standard I, standard II and superlong) are calculated separately and the total spectrum is synthesized. The multi-modal parameters contained in the spectrum model are determined on the basis of experimental data of fission fragment mass distributions. The calculated total prompt fission neutron spectrum and multiplicity are better agreement with the experimental data than those obtained from the conventional treatment of the Los Alamos model.

A relational nuclear database management and webbased services software system has been developed. Its objective is to allow users to access numerical and graphical representation of nuclear data and to easily reconstruct nuclear data in original standardized formats from the relational databases. It presents 9 relational nuclear libraries: 5 ENDF format neutron reaction databases (BROND, CENDL, ENDF, JEF and JENDL), the ENSDF database, the EXFOR database, the IAEA Photonuclear Data Library and the charged particle reaction data from the FENDL database. The computer programs providing support for database management and data retrievals are based on the Linux implementation of PHP and the MySQL software,and are platformindependent. The first version of this software was officially released in September 2001.