For prompt physical diagnosis, several types of subnanosecond current mode detectors have been developed, including scintillator detectors with large linear output current, GaAs:Cr and InP:Fe photoconductor detectors(PCD), and X-ray diodes(XRD), etc. The characteristic of scintillation light of BaF2 crystal doped with La and of plastic scintillator ST1422 with slow component quencher are described. As for the photoconductor detectors, the main performance of neutron damaged GaAs:Cr and InP:Fe were studied. In addition, the spectral response of an XRD with coaxial leading-out end was also studied. These detectors have been successfully applied to nuclear test diagnosis and ICF research.
Vol.10, No.3
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686
Research article 01 Aug 1999
WEN Shu-Huai，YANG Jian-Lun，YANG Hong-Qiong，TANG Zheng-Yuan，WANG Gen-Xing，CHEN Jin-Xiu，SUN Ke-Xi，XU Rong-Kun
keyword：Prompt physical process diagnostic；Subnanosecond techniques；Scintillator detector；Photoconductor detector；
Research article 01 Aug 1999
LI Bin，ZHANG Yi，OUYANG Zhenqian，HU Jun，HUANG Yibo，LI Minqian
A modified "dynamic molecular combing" (DMC) technique used for stretching double-stranded DNA is reported. DNA molecules were stretched on the silanized mica surface by this technique, its speed being precisely controlled with a computer. This approach combined the precise DNA stretching method with high resolution AFM imaging at nanometer scale, thus making it useful for DNA alignment manipulation and subsequent gene research.
keyword：Atomic force microscopy；Dynamic molecular combing；Stretching DNA molecules；
Research article 01 Aug 1999
LI Guisheng，ZHANG Tianmei，LI Zongwei，SU Youwu，ZHANG Shumin
Neutron energy, fluence rate, angular distributions and dose equivalent rate distributions around the thick Be, Cu, Au targets bombarded by 50 MeV/u 18O-ion were measured using a threshold detector activation method. At the same time, the neutron yields of 18O-ion and the neutron emission rates in the forward direction were obtained approximately.
keyword：Neutron yield；Dose equivalent rate；Neutron distribution；18O-ion；Thick target；
Research article 01 Aug 1999
WU Lijun，HEI Tom K.，RANDER-PEHRSON Gerhard，WANG Shaohu，YU Zengliang
Columbia University microbeam was constructed in 1993 and finished by the end of 1995. It is well established and used routinely to irradiate cells in a highly localized spatial region with a defined number of a-particles. By using this probe, it is possible to study a number of radiobiological questions in ways that cannot be simulated by using conventional broad-field exposures. This report describes the development and current capabilities of the Columbia University microbeam, as well as the preliminary researches undertaken.
keyword：Irradiation；Single particle；Microbeam；Radiobiological effects；
Research article 01 Aug 1999
WANG Zixing，SHEN Shuifa，SHI Shuanghui，GU Jiahui，LIU Jingyi，ZHU Zhiyuan
The projected shell model is applied to the nucleus 129La. The present results of theoretical calculations about the one-quasiproton bands are compared with experimental data. The agreement with both the yrast πh11/2 band πg7/2 band is satisfactory. We also assign the πg7/2⊗ [vh11/2] 2 configuration with an oblate shape for one of bands in 129La.
keyword：Prolate shape；PSM (Projected shell model)；One-quasiproton band；
Research article 01 Aug 1999
ZHU Shaoping
A self-consistent kinetic simulation study of one dimensional collisional bounded plasma is presented. The formation of stable sheath potential is investigated. It is found that mass ratio of electron and ion not only affects the level of sheath potential, but also affects the ion temperature of system. It is clarified that the effects of secondary emission electron on both the total potential drop and the temperature are not important.
keyword：Bounded plasma；Plasma sheath potential；Kinetic simulation；
Research article 01 Aug 1999
SHU Xiaojian
A new kind of MOPA configuration to obtain a high power free-electron laser with very narrow line-width that can satisfy the requirements of some applications such as the laser isotope separation has been proposed, which is investigated by one-dimension simulations.
keyword：Free-electron laser；MOPA configuration；Laser isotope separation；
Research article 01 Aug 1999
ZHI Min
Filtering efficiency of the Chinese-made filter 1 has been measured by the double-filter method with only one set of measurement equipment. The β counts of the two filters are measured in turn for every 3 minutes, from which the decay constants are extracted to be 0.0131 min-1 and 0.0129 min-1 for the first and second filter respectively. After correcting the β counts of the second filter, the filtering efficiency of the filter is obtained to be (87.4±0.7)% in average.
keyword：Double-filter method；Single set measuring system；Filtering efficiency；
Research article 01 Aug 1999
GUO Jiangfeng，SUN Jinhe，YE Qingfu
The reason why chlorsulfuron (2-chloro-N-[4-methoxy-6-methy1-1,3,5-triazin-2-yl)amino] carbonyl]benzenesulfonamide)bound residues can still make an injury to rotational crops is still kept unknown. The experiment was conducted under laboratory conditions to determine the dynamics of extractable and non-extractable (bound) residues of chlorsulfuron in soil, and the distribution of chlorsulfuron bound residues in organic matter fractions. The results showed that extractable 14C-residues decreased to 25.12% of applied chlorsulfuron over an incubation period of 150 days; this in turn, the formation of bound residues increased to 47.07% of the applied. The proportions of 14C-bound residues in soil organic matter fractions increase in order of: humic acid (HA)﹤humin﹤fulvic acid(FA), most of bound residues existed in FA fraction, however, the amount of bound residues in humin fraction increase with incubation time. The fact that most of bound residues existed in water-soluble FA fraction is tentatively regarded as one of major reasons why 14C-chlorsulfuron bound residues can still make an injury to rotational crops.
keyword：Humic acid；Chlorsulfuron；Bound residues；Soil organic matter；Fulvic acid；Humin；
Research article 01 Aug 1999
BAO Jinsong，SHU Qingyao，BERGMAN Christine，XIA Yingwu，McCLUNG Anna
The effect of γ irradiation on the cooked rice texture and amylopectin structure is studied with three varieties (Zhefu 504, Zhefu 802 and Zaogeng T2) subjected to 4kGy, 8kGy and 12kGy irradiation. The results indicate that irradiation has significant effect on the texture of the cooked rice; the hardness, cohesiveness, gumminess and chewiness reduce significantly with the increase of the irradiation dose. Irradiation also affects the chain length distribution of the amylopectin, the side-chains of amylopectin of Zhefu 504 with the 12≥DP, Zhefu 802 with 24≥DP≥13 and Zaogeng T2 with 24≥DP≥13 and 36≥DP≥25 are broken.
keyword：γ-irradiation；Cooked rice texture；Amylopectin structure；
Research article 01 Aug 1999
CAI Xichen，WEI Zengquan，LI Wenjian，LIANG Jianping，LI Qiang
Some methods of capillary gas chromatography, such as GC, GC-MS, GC-FT-IR, are used to analyze the products of thymine irradiated by 18O8+ ion beam in N2O saturated aqueous solution. From the results of GC-MS the molecular weight of products can be determined, and from the results of GC-FT-IR some molecular structure information of products can be obtained. By this way the products, 5,6-Dihydrothymine, 5-Hydroxyl-5-Methylhydantoin, 5-Hydroxyl-6-Hydrothymine, 5-Hydro-6-Hydroxylthymine, 5-Hydroxymethyluracil, Trans-Thymine glycol, Cis-Thymine glycol and dimers are determined without separation of them from samples. Though these products are as same as those products of thymine irradiated by γ rays in N2O saturated aqueous solution, the mechanism of thymine irradiated by heavy ion beam in aqueous solution is different from that by γ rays. The main products of thymine irradiated by 18O8+ ion beam in N2O saturated aqueous solution are hydroxyl adducts at 5-6 band of thymine, while the main products of thymine irradiated by γ ray in N2O saturated aqueous solution are dimers of thymine.
keyword：Irradiation；Thymine；Heavy ion beam；
Research article 01 Aug 1999
SUN Kexia，ZHANG Mingyuan，CHEN Xuejun
An investigation on phase distribution in air-water two-phase flow in horizontal circular channel was conducted by using the double-sensor resistivity probe. The variations of phase distribution with variations of gas and liquid volumetric fluxes were analyzed and the present data were compared with some of other researcher's data and existing models. It was found there exists more complicated phase distribution pattern in horizontal flow system than in vertical flow. The radial local void fraction profiles are similar at the same measurement angle with various gas and liquid flow rates. However, an asymmetric profile can be observed at a given slice of the pipe cross-section.
keyword：Gas-liquid two-phase bubbly flow；Phase distribution；Double-sensor probe；
Research article 01 Aug 1999
LUO Wenyun，WANG Chuanshan
Fast neutron activation of nitrogen and oxygen contained in the explosives used for simulated mine samples has been preliminarily carried out in our laboratory. By spectroscopic analysis of characteristic γ-rays emitted from activated nitrogen and oxygen, mine can be identified almost instantly. This technique integrated with robotics would be a method for mine scavenging.
keyword：Fast neutron activation；Mine detection；Explosive；
