Abstract: Neutron capture reaction is one of the neutron reactions and plays an important role in using reactor control rods and shell materials, designing nuclear device structures, and studying nuclear astrophysics S processes and element origins. The 4π BaF〈sub〉2〈/sub〉 detection device has advantages such as high time resolution, low neutron sensitivity, and high detection efficiency, thus making it suitable for measuring neutron radiation capture reaction cross-section data. In order to fill the gap in our neutron capture reaction data in the keV energy range and improve their accuracy, the Key Laboratory of Nuclear Data at the Chinese Institute of Atomic Energy (CIAE) has established a Gamma Total Absorption Facility (GTAF), which consists of 28 hexagonal BaF〈sub〉2〈/sub〉 crystals and 12 pentagonal BaF〈sub〉2〈/sub〉 crystals to form a spherical shell with an external diameter of 25 cm and an internal diameter of 10 cm, covering 95.2% of the solid angles. The Back-n beam line of the Chinese Spallation Neutron Source (CSNS) is a back-streaming white beam line that covers neutron energy ranging from a few eV to several hundred MeV, making it suitable for measuring neutron capture cross-sections. The reaction cross-section data of 〈sup〉197〈/sup〉Au is measured by using GTAF on the Back-n beam line. The measurement data are preliminarily background deducted through energy screening, PSD method, and crystal multiplicity screening. Subsequently, the background is analyzed and deducted based on the measurement data of 〈sup〉nat〈/sup〉C and empty samples, and the yield of 〈sup〉197〈/sup〉Au capture reaction is obtained. Resonance parameters are a set of parameters extracted from experimental data to describe the resonance curve, which can eliminate the influence of experimental conditions on resonance data and are more important than the cross-section obtained from experiments. The resonance energy, neutron resonance width, and gamma resonance width parameters of 〈sup〉197〈/sup〉Au at 1–100 eV are fitted by using the SAMMY program. From the comparison between the resonance curves obtained from experimental measurements and the resonance parameters obtained from fitting with the ENDF/B-VIII.0 database, it can follow that the experimental measurement results are in good agreement with the database, nevertheless, there exist some differences in the resonance parameter, which may be due to the GTAF energy resolution, Back-n neutron spectrum measurement accuracy, and the experimental background deduction method. Our next work is to identify the sources of difference.

Abstract: The back-streaming neutron beam line (Back-n) was built in the beginning of 2018, which is part of the China Spallation Neutron Source (CSNS). The Back-n is the first white neutron beam line in China, and its main application is for nuclear data measurement. For most of neutron-induced nuclear reaction measurements based on white neutron facilities, the beam of gamma rays accompanied with neutron beam is one of the most important experimental backgrounds. The back streaming neutron beam is transported directly from the spallation target to the experimental station without any moderator or shielding, the flux of the in-beam gamma rays in the experimental station is much larger than those of these facilities with neutron moderator and shielding. Therefore, it is necessary to consider the influence of in-beam gamma rays on the experimental results. Studies of the in-beam gamma rays are carried out at the back-n. Monte-Carlo simulation is employed to obtain the energy distribution and the time structure of the in-beam gamma rays. According to the simulation results, when the neutron flight time is longer than 1.0 μs the energy distribution of the in-beam gamma rays does not vary with flight time. Therefore, the time structure of these gamma rays can be measured without the correction of the detection efficiency. In this work, the time structure of the in-beam gamma rays in the low neutron energy region is measured by both direct and indirect methods. In the direct measurement, a 〈sup〉6〈/sup〉Li loaded ZnS(Ag) scintillator is located on the neutron beam line and the time of flight method is used to determine the time structure of neutrons and gamma rays. The gamma rays are separated from neutrons with pulse-shape discrimination. The black filter method is used to verify the particle discrimination results. In the indirect measurement, the C〈sub〉6〈/sub〉D〈sub〉6〈/sub〉 scintillation detectors are used to measure the gamma rays scattered off a Pb sample on the way of the neutron beam. The time structure of the in-beam gamma rays is derived from that of the scattered gamma rays. The experimental results are in good agreement with the simulations with the time-of-flight between 12 μs and 2.0 ms. Besides, according to the simulation results, the intensity of the in-beam gamma rays is 1.21 × 10〈sup〉6〈/sup〉 s〈sup〉–1〈/sup〉·cm〈sup〉–2〈/sup〉 in the center of the experimental station 2 of Back-n, which is 76.5 m away from the spallation target of CSNS.

Abstract: The data of neutron capture cross section are very important for the research of nuclear astrophysics, advanced nuclear energy development. Owing to the limitation of neutron source and detector, the experimental data of neutron capture cross section in an energy range of 1 eV–10 keV were almost blank in China. The first Chinese gamma-ray total absorption facility has been constructed in the key laboratory of nuclear data at China institute of atomic energy, which consists of 40 BaF〈sub〉2〈/sub〉 detector units. The BaF〈sub〉2〈/sub〉 crystal shell with a thickness of 15 cm and an inner radius of 10 cm covers 95.2% of the solid angle. On-line measurement method of neutron capture reaction cross section is established on the back-streaming white neutron source of China spallation neutron source by using the upgraded facility. The cross section of 〈sup〉197〈/sup〉Au neutron capture reaction is measured for the first time under the experimental condition of irregular 30 mm neutron beam spot. The measured position of resonance peak is well consistent with the relevant data of ENDF evaluation database, which verifies the reliability of the measurement device and measurement technology, and thus laying the foundation for the acquisition of high precision cross section in future.

Abstract: At present, there exist few proton-beam terminals for the detector calibration in the world. Meanwhile, most of these terminals provide monoenergetic protons. Back-n white neutron source from China Spallation Neutron Source(CSNS) was put into operation in 2018. Based on the white neutron flux ranging from 0.5 eV to 200 MeV from the CSNS Back-n white neutron source, continuous-energy protons involved in a wide energy spectrum can be acquired from the 〈sup〉1〈/sup〉H(n, el) reaction. Adopting this method, a new research platform for researches such as proton calibration is realized at CSNS. As hydrogen exists as gas at normal temperature and pressure, in the selecting of the proton-converting target, the hydrogen-rich compounds are preferential considered. Considering the reaction cross sections of the 〈sup〉1〈/sup〉H(n, el), 〈sup〉12〈/sup〉C(n, p)〈sup〉12〈/sup〉B, 〈sup〉12〈/sup〉C(n, d)〈sup〉11〈/sup〉B, 〈sup〉12〈/sup〉C(n, t)〈sup〉10〈/sup〉B, 〈sup〉12〈/sup〉C(n, 〈sup〉3〈/sup〉He)〈sup〉10〈/sup〉Be, 〈sup〉12〈/sup〉C(n, α)〈sup〉9〈/sup〉Be and 〈sup〉1〈/sup〉H(n, γ)〈sup〉2〈/sup〉H, polyethylene and polypropylene are suitable for serving as targets in this research. Based on a 3U PXIe, digitizers with 1 GSps sampling rate and 12 bit resolution are utilized to digitize and record the output signals of telescopes. The time and amplitude information of each signal are extracted from its recorded waveform. Proton fluxes can be calculated by using the neutron energy spectrum and the cross section of the 〈sup〉1〈/sup〉H(n, el) reaction. Using the γ-flash event as the starting time of the time-of-flight (TOF) and the time information of signal in detector as the stopping time, the kinematic energy of each secondary proton can be deduced from the TOF and the angle of the detector. A calibration experiment on three charged particle telescopes, with each telescope consisting of a silicon detector and a CsI(Tl) detector, is carried out on this research platform. The readout methods of the CsI(Tl) detectors in these three telescopes are different. In the calibration experiment, Δ〈i〉E-〈/i〉〈i〉E〈/i〉 two-dimensional spectra and amplitude-〈i〉E〈/i〉〈sub〉p〈/sub〉 two-dimensional spectra of these telescopes are obtained. Through comparing these particle identification spectra, the SiPM is chosen as the signal readout method for CsI(Tl) detectors in the charged particle telescopes. These researches provide experimental evidence for the construction of the charged particle telescope at Back-n, and also illustrate the feasibility of wide-energy spectrum proton calibration based on the Back-n white neutron source.

Abstract: The Chinese spallation neutron source was completed in May 2018 and then subsequently commissioned. The Back-streaming white neutron beam line can be used in neutron nuclear data measurement, neutron physics research, and nuclear technology. In these experiments, it is necessary to know the neutron energy spectrum, the neutron flux, and the neutron beam profile of the neutron beam. In this paper, we present the preliminary measurements of these parameters. The neutron energy spectrum and neutron flux are measured by the time-of-flight method with a fission chamber equipped with 〈sup〉235〈/sup〉U and 〈sup〉238〈/sup〉U samples and a 〈sup〉6〈/sup〉Li-Si detector. The neutron beam profile is measured by a scintillator-CMOS detection system. The preliminary experimental measurements of the beam line are obtained. Among them, the energy spectrum measurement range of white neutrons is from eV to more than 100 MeV, which also gives an uncertainty analysis; the neutron fluence rate gives the full power value of the two experimental halls; the collimated white neutron beam spot is given under a diameter of 60 mm. The future plan is also given. The results of these experimental parameters can serve as the foundation for the future nuclear data measurement and detector calibration experiments of the beam line.

Abstract: The structure and magnetic properties of a series of rf sputtered ［Co(1.5nm)/V(dV)］20(0.5nm≤dV≤4nm)multilayers have been studied.The multilayers structure is found by X-ray diffraction,cross-section transmission electron microscopy,and high-resolution transmission electron microscopy to be polycrystalline with small individual columnar grains and has fairly strong fcc Co(111)and bcc V(110) texture in the film growth direction.The structural characterizations also show composition-modulated structure and severely alloyed effect.Ferromagnetic resonance measurements show relatively small g factors and 4π Meff values,which also indicates that multilayers are severely alloyed.Complicated spin wave resonance spectra were observed and analyzed.The evaluated small interlayer coupling constant shows the effect of weak exchange coupling between Co layers across V spacers.

Abstract: Transparent conductive oxide (TCO) films and transparent oxide semiconductor (TOS) films have been widely adopted in solar cells, flat panel displays, smart windows, and transparent flexible electronic devices due to their advantages of high transparency and good conductivity and so on. Most of TCO and TOS films are mainly derived from indium oxide, zinc oxide and tin oxide. Among these materials, the In element is toxic, rare and expensive for indium oxide film, which will cause environmental pollution; zinc oxide film is sensitive to acid or alkali etchants, resulting in a poor formation of film patterning; tin oxide film is not only non-toxic, eco-friendly, and cheap but also has good electrical properties and strong chemical stability. Thus, tin oxide has a great potential for developing the TCO and TOS films. At present, the film is prepared mainly by the vacuum deposition technique. The drawbacks of this technique are complex and expensive equipment system, high energy consumption, complicated process and high-cost production. However, compared with the vacuum deposition technique, the sol-gel method has attracted extensive attention because of its virtues such as simple process and low cost. In this paper, we review the development status and trend of TCO and TOS films. First, the structural characteristics, conductive mechanism, element doping theory and carrier scattering mechanism of tin oxide thin films are introduced. Then the principle of sol-gel method and correlative film fabrication techniques are illustrated. Subsequently, the application and development of tin oxide-based thin films prepared by sol-gel method in n-type transparent conductive films, thin-film transistors and p-type semiconductor films in recent years are described. Finally, current problems and future research directions are also pointed out.

Abstract: Copper is an alternative material for aluminum electrode to meet the stringent requirement for high mobility and low resistance-capacitance (RC) delay of amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistor (TFT) for next generation of display technology due to its intrinsic high conductivity. However, low bonding strength between copper layer and insulator/glass and easy diffusion into active layer restrict its application in the field of TFT. In this work, a 30 nm thin film of molybdenum is introduced into copper electrode to form a copper-molybdenum source/drain electrode of a-IGZO TFT, which not only inhibits the diffusion of copper, but also enhances the interfacial adhesion between electrode and substrate. The obtained Cu-Mo TFT possesses a high mobility of ～9.26 cm2·V-1·s-1 and a low subthreshold swing of 0.11 V/Decade. Moreover, it has shorter current transfer length(～0.2 μm), lower contact resistance (～1072 Ω), and effective contact resistance (～1×10-4Ω·cm2) than the pure copper electrode. Cu-Mo electrode with low contact resistance and high adhesion to substrates paves the way to the application of copper in high conductivity interconnection of a-IGZO TFT.

Abstract: Exciplex-type organic light-emitting diodes (OLEDs) are research focus at present, because of their high-efficiency luminescence at low cost due to the reverse intersystem crossing (RISC, EX〈sub〉1〈/sub〉 ← EX〈sub〉3〈/sub〉). Their microscopic processes usually exhibit intersystem crossing (ISC, PP〈sub〉1〈/sub〉 → PP〈sub〉3〈/sub〉) process dominated by polar pairs, leading the magneto-electroluminescence [MEL, MEL = (ΔEL)/EL × 100%] effect values and the magneto-conductance [MC, MC = (Δ〈i〉I〈/i〉)/〈i〉I〈/i〉 × 100%] effect values to be both positive, the amplitude of MEL to be greater than that of MC at the same current, and the corresponding magnetic efficiency [M〈i〉η〈/i〉, M〈i〉η〈/i〉 = (Δ〈i〉η〈/i〉)/〈i〉η〈/i〉 × 100%] values to be also positive due to the linear relationship EL 〈inline-formula〉〈tex-math id="Z-20221116105031-1"〉\begin{document}$ \propto \eta\cdot I $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221116105031-1.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221116105031-1.png"/〉〈/alternatives〉〈/inline-formula〉 within general current (〈i〉I〈/i〉) range. Surprisingly, although the MEL value of the device coexisting with exciplex and electroplex is also greater than the MC value at low current, MEL value is less than MC value at high current. In other words, M〈i〉η〈/i〉 value of this device undergoes a conversion from positive to negative with current increasing. In this work, to find out the reason why M〈i〉η〈/i〉 value of exciplex-type OLED formed by TAPC and TPBi shows a negative value under high current and also to study the micro-dynamic evolution mechanism of spin-pair states in this device, three OLEDs are fabricated and their luminescence spectra and organic magnetic field effect curves are measured. The results indicate that the electroplex is produced in the exciplex-type OLED formed by TAPC and TPBi. Since the triplet exciton energy of monomers TAPC and TPBi is higher than those of triplet charge-transfer states of exciplex (CT〈inline-formula〉〈tex-math id="Z-20221107140615"〉\begin{document}${}_3^{\rm{ex}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140615.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140615.png"/〉〈/alternatives〉〈/inline-formula〉), and the CT〈inline-formula〉〈tex-math id="Z-20221107140631"〉\begin{document}${}_3^{\rm{ex}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140631.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140631.png"/〉〈/alternatives〉〈/inline-formula〉 energy is greater than the energy of triplet charge-transfer states of electroplex (CT〈inline-formula〉〈tex-math id="Z-20221107140638"〉\begin{document}${}_3^{\rm{el}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140638.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140638.png"/〉〈/alternatives〉〈/inline-formula〉), the CT〈inline-formula〉〈tex-math id="Z-20221107140644"〉\begin{document}${}_3^{\rm{ex}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140644.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140644.png"/〉〈/alternatives〉〈/inline-formula〉 energy can only be transferred to CT〈inline-formula〉〈tex-math id="Z-20221107140650"〉\begin{document}${}_3^{\rm{el}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140650.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140650.png"/〉〈/alternatives〉〈/inline-formula〉 through Dexter energy transfer (DET) process without other loss channels. The electroluminescence (EL) spectrum of this device shows that the luminescence intensity of exciplex is greater than that of electroplex, which indicates that the quantity of exciplex is more than that of electroplex. Besides, EL spectra at different currents prove that the formation rate of exciplex is faster than that of electroplex with current increasing. Owing to less quantity of exciplex at low current, the DET process from CT〈inline-formula〉〈tex-math id="Z-20221107140657"〉\begin{document}${}_3^{\rm{ex}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140657.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140657.png"/〉〈/alternatives〉〈/inline-formula〉 to CT〈inline-formula〉〈tex-math id="Z-20221107140702"〉\begin{document}${}_3^{\rm{el}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140702.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140702.png"/〉〈/alternatives〉〈/inline-formula〉 is too weak to facilitate the RISC process of charge-transfer states of electroplex (CT〈sup〉el〈/sup〉). Therefore, the low field amplitude of M〈i〉η〈/i〉 curve is positive at low current. The number of spin-pair states of exciplex increases with current increasing, which enhances the DET process. These processes of direct charge carriers trapped and energy transferred critically increase the number of CT〈inline-formula〉〈tex-math id="Z-20221107140712"〉\begin{document}${}_3^{\rm{el}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140712.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20221288_Z-20221107140712.png"/〉〈/alternatives〉〈/inline-formula〉 at high current, which greatly strengthens the RISC process of CT〈sup〉el〈/sup〉. Therefore, the low field amplitude of M〈i〉η〈/i〉 curve changes from positive to negative with current increasing. Furthermore, the M〈i〉η〈/i〉 curves of this device are measured when only exciplex exists and only electroplex exists in the employing filter, respectively. As expected, the results confirm the accuracy of the mechanism of the negative value of the total M〈i〉η〈/i〉 for this device. Obviously, this work contributes to the comprehension of the internal micro-physical mechanism in OLEDs and the law of interactions between excited states.