[en] A spherical energy filter (SEF) was constructed and matched to a MAT-261 mass spectrometer for analyses of very low abundance isotopes. The SEF is a 150-mm mean radius, 90⁰ spherical electrostatic sector, and is located behind the magnet sector using a C configuration. The abundance sensitivity of the modified mass spectrometer, which was measured using a NBS natural uranium sample by both ion counting and current integrating multipliers, was less than 0.13 ppm (unit mass separation at A = 238)

[en] A charge-collection method for measuring the flux of pulsed fast neutrons in current mode has been developed, which is based on the well-known recoil-proton method combined with ion-induced secondary electron emission from solid surfaces. The detection unit consists of four elements: an n-p converter, an absorber, a collector, and a rear insulator. The assembly does not require vacuum for operation. Recoil protons from the n-p converter and the secondary electrons induced by the passing protons on the interface of the absorber and the collector contribute to the detector output signal. By properly choosing the materials and the combination of the absorber and the collector, the fraction of secondary electrons in the output signal can be determined experimentally. This detection concept allows one to design a medium type of fast-neutron detector for measurements of extremely intense pulsed neutron flux with a number of advantages over the existing systems

[en] A method of efficiency calibration for the measurement of ⁸⁸Kr and ¹³⁸Xe by HPGe γ spectrometer was proposed in the present paper. The efficiency calibration of their decay daughters ⁸⁸Rb and ¹³⁸Cs were first conducted by utilizing of their liquid sources, then the calibration measurements of ⁸⁸Kr and ⁸⁸Rb or ¹³⁸Xe and ¹³⁸Cs were be carried out by prepared homogeneous sources of ⁸⁸Kr-⁸⁸Rb and ¹³⁸Xe- ¹³⁸Cs. The calibrated efficiency of ⁸⁸Kr and ¹³⁸Xe can be obtained by using the decay relationship between ⁸⁸Kr and ⁸⁸Rb or ¹³⁸Xe and ¹³⁸Cs. Obviously, the key for the efficiency calibration is how to achieve the homogeneous sources. The fission product gases were obtained by irradiating quantitative U₃O₈(90% ²³⁵U ) filled in a quartz glass ampoule. Due to the adsorption or sedimentation, their solid decay daughters. will be not homogeneous in the source cell if the fission product gasses were directly filled into the vacua ted cell. In order to prepare homogeneous calibration sources, granules of stearic acid was used in this work. Source cell was first filled up with stearic acid, and then the fission product gases were charged into it. The apparatus for preparation of the calibration sources was showed in Fig.1. Xenon and krypton are not adsorbed on stearic acid, therefore the homogeneous sources of ⁸⁸Kr-⁸⁸Rb and ¹³⁸Xe-¹³⁸Cs can be prepared. The results of the experiment demonstrate that the method is feasible and successful.

[en] A method of efficiency calibration for the measurement of ⁸⁸Kr and ¹³⁸Xe by HPGe γ-spectrometer is proposed in the present paper. The question for the efficient calibration is, how to achieve homogeneous sources of ⁸⁸Kr-⁸⁸Rb and ¹³⁸Xe-¹³⁸Cs. The fission product gases were obtained by irradiating a precisely measured amount of U₃O₈ (90% ²³⁵U) filled in a quartz glass ampoule. Source cell was first filled up with stearic acid, and then the fission product gases were charged into it. Xenon and krypton are not adsorbed on stearic acid, therefore, homogeneous sources of ⁸⁸Kr-⁸⁸Rb and ¹³⁸Xe-¹³⁸Cs can be prepared. The results of the experiment demonstrate that the method is feasible and successful. (author)

[en] The excitation of CO₂-N₂-He gas mixtures by means of microwaves (μ = 2.45 GHz) leading to laser action is possible. In order to avoid hot boundary layers near the discharge wall a proper distribution of the gas flow and the microwave field must be chosen. Additionally an ignition setup is necessary to achieve a homogeneous glow in the discharge tube. In this paper ignition and permanent maintenance of a microwave discharge as well as the kinetic processes leading to laser action are studied on a theoretical base. The theoretical data are compared with experimental ones obtained from an ignition experiment and CO₂-laser devices of 0.3 or 1 kW cw output power, respectively. Examples for continuous and pulsed laser operation are given

[en] The effect of ion implantation including ion species (N₂⁺ and C₃H₈⁺) and the fluences (1x10¹⁴-5x10¹⁵ ions/cm²) on the surface energy of ultrahigh molecular weight polyethylene (UHMWPE) were investigated. The total surface energy increases significantly after implanting with the fluence of 1x10¹⁴ ions/cm² regardless of ion species, then, the total surface energy slightly increases for N₂⁺ implanted UHMWPE and decreases slightly for C₃H₈⁺ implanted UHMWPE with a further increase of fluence. The structural changes of UHMWPE with different fluence for different ion species are very similar. The linear chains of UHMWPE are damaged and cross linking is generated after implantation. As the fluence increases, the polymer surface becomes more disordered, and the surface becomes hydrogenated amorphous carbon when the fluence exceeds 1x10¹⁵ ions/cm². The surface roughness increases with the increase of the fluence regardless of ion implantation species

[en] Stilbene crystals are used as neutron detectors connected with photomultiplier tubes. An online acquisition method assembled by CAMAC standard plug-ins, NIM plug-ins, a neutron-γ (n-γ) discrimination plug-in named Canberra-2160A, and an offline acquisition method, assembled with an oscilloscope, were developed to obtain nuclear signals from neutron detectors. The online and offline acquisition methods collected pulse signals simultaneously while n-γ discrimination and measurement of deuterium-deuterium (DD) and deuterium-tritium (DT) neutron beam were carried out by both acquisition methods. The resulting n-γ discrimination, detection efficiency, and neutron spectra of varying stilbene crystal sizes were obtained. The neutron events accounted for approximately 80% of the total events in this radiation field formed by DD neutron beam and 50% for DT neutron beam. The results of n-γ discrimination of the two acquisition methods matched very well. The figures of merit (FoM) of n-γ discrimination obtained by the online acquisition method were 2.158 for the radiation field formed by DD neutron beam and 1.802 for DT when over 10⁵ pulses were used for analysis. The pulses acquired by the offline acquisition method were repeatedly used to obtain the best discrimination effects, neutron charge-amplitude spectrum, and pulse height spectrum after the particular waveform digitization process. It was shown that the offline acquisition method composed of stilbene crystals, a photomultiplier tube, and a digital oscilloscope could realize the same function and effect as the online acquisition method for monoenergetic neutron beam, but with fewer pulses. A feasible experimental method was obtained which have a good potential for the neutron flux monitoring of the pulsed-neutron radiation fields, in which the total number of events is small or the neutron propagation process is instantaneous.

[en] A new type of hybrid photon detector (HPD) based on SiC Schottky diode, with good radiation resistance and large sensitive area, has been constructed for either steady or pulsed light illumination. A series of experiments were carried out to examine its performance. As a result, the prototype SiC-HPD obtained a gain varying from 0 to 418, when the acceleration high voltage was up to 10 kV . In addition, the prototype SiC-HPD showed a nanoseconds time response with leading edge of 3.5 ns (FWHM $\sim <!--\; ???\; -->$ 16.6 ns) and a maximum output current around 0.65 A under long pulse irradiation. The results indicate that the SiC-HPD is a very promising detector with high gain, fast-time-response and high pulse linearity current for the radiation-field measurements.

[en] Angiogenesis is of great importance in bone tissue engineering, and has gained large attention in the recent 10 years. However, little research has been done on the effect of biodegradable materials, especially their degradation products on the angiogenesis process. Strontium-doped calcium polyphosphate (SCPP) has been proved to be able to promote osteoblasts growth in vitro before. In the present work, the interaction of endothelial cells (ECs) with the scaffold of SCPP was investigated to evaluate its potential influences on angiogenesis. The cell adhesion on SCPP scaffold as well as the angiogenic behaviors including proliferation, migration and tube-like structure (TLS) formation of ECs treated by its degradation products was tested. The results were compared with those of CPP group and physiological saline (negative control). As the results showed, the surface of SCPP could promote the adhesion and spreading of ECs. Ca²⁺ and Pi as well as Sr²⁺ were the main degradation products of SCPP. They did not inhibit but could promote the proliferation of ECs within 90 days. Moreover, they could induce the migration and TLS formation of ECs. Since SCPP bears the ability to improve the adhesion and angiogenic behaviors of endothelial cells, it might benefit angiogenesis and serve as a more promising scaffold for bone tissue engineering application. Besides, this work may provide a new method for in vitro evaluation of biodegradable materials' potential effects on angiogenesis

[en] The susceptibility of age-hardened nickel-based Alloy 718 to hydrogen embrittlement was studied by the controlled electrochemical charging combined with slow strain-rate tensile tests (SSRT) and advanced characterization techniques. We proposed some novel ideas of explaining hydrogen embrittlement mechanisms of the studied material in regard to two cracking morphologies: transgranular and intergranular cracking. It is for the first time to report that electrochemical charging alone could cause slip lines, surface and subsurface cracks on nickel-based superalloys. The formation of pre-damages was discussed by calculating the hydrogen concentration gradient and the internal stress generated during cathodic charging. Pre-damages were proved to result in transgranular cracks and lead to the evident reduction of mechanical properties. In addition, the STRONG (Slip Transfer Resistance of Neighbouring Grains) model was used to analyze the dependence of hydrogen-assisted intergranular cracking on the microscopic incompatibility of the grain boundaries. The results show that in the presence of hydrogen, grain boundaries with a lower dislocation slip transmission are more prone to cracking during loading and vice versa.