高能中子辐射对线虫的剂量效应研究

本文研究了高能中子辐射对秀丽隐杆线虫(Caenorhabditis elegans)剂量效应并讨论了高能中子辐射的相对生物学效应。雌雄同体的线虫随机分为对照组和10个不同剂量梯度的照射组,分别为1 047、476、199、89、18.2、8.4、1.83、0.351、0.171和0.087 Gy。不同剂量梯度的线虫距离中子源的距离不同,但是照射时间相同。线虫经过单次高能中子全身照射后,分别于当天将线虫转入新皿进行产卵率、寿命的后续检测以及24小时后将线虫转入新皿进行生殖细胞凋亡的检测。结果表明,随着剂量的增加,产卵量呈现总体下降的趋势,特别是1.83 Gy对线虫子代数的影响很大,大于89 Gy照射后线虫停止产卵;寿命呈现随辐射剂量上升而下降的趋势,尤其是1.83 Gy对线虫寿命的缩短效应明显;大于8.4 Gy剂量中子照射时,生殖细胞凋亡随剂量的升高而显著上升。以上结果说明,高能中子辐射对线虫具有剂量效应,但是在低剂量辐射时可能有更强的损伤效应,为中子低剂量辐射防护提供了科学依据。本文同时讨论了以中子照射数据与前人γ射线照射实验结果相对比的结果,计算得出HINEG高能中子辐射的相对生物效应是1.25,表明在相近吸收剂量的γ射线与中子照射下两者生物学效应差异,提示了品质因数(Q值)与ICRP出版物的差异以及完善参考动物数据库的必要性。     

Angle and energy characteristics of neutrons produced by a high-energy ion beam

Translated from Atomnaya Énergiya, Vol. 66, No. 3, pp. 213–215, March, 1989.     

Numerical simulation of high-energy neutron radiation effect of scintillation fiber

Due to their low cost,flexibility,and convenience for long distance data transfer,plastic scintillation fibers (PSF) have been increasingly used in building detectors or sensors for detecting various radiations and imaging.In this paper,GEANT4 Monte Carlo simulation tool was used to obtain some radiation effects of PSF under high-energy neutron irradiation.BCF-20,a plastic fiber material,produced by Saint-Gobain,was used in the simulation.The fiber consists of a core scintillating material of polystyrene and an acrylic outer cladding.Incident neutrons produce energy deposition in fiber through neutron induced recoil proton events.The relationships between energy deposition efficiency and fiber length,fiber radius and incident neutron energy are presented.The variation with those parameters and parameter selection are also analyzed.     

Dosimeter characteristics of neutron track detectors used on high-energy accelerators

Conclusions Experience gathered in recording neutrons with the aid of polymer track detectors on calibrated neutron sources and around the 70 GeV proton synchrotron has shown that detectors making use of fissile nuclides in combination with polyethylene terephthalate track detectors and spark counting of the tracks are suitable and promising for their large scale use as measuring means of dosimetric characteristics of the neutron fields in a high-energy accelerator. They can be used to build an albedo-track dosimeter in which²³⁵U is the albedo detector and²³⁷Np,²³⁸U, and²³²Th are used as the threshold detector. Also a nitrate cellulose film without a converter can be used as a threshold detector but there the measurement error is 2–3 times greater than in the detectors making use of fissile nuclides because the film sensitivity has a considerable (30%) spread even to monochromatic neutrons. In addition, a detector based on²⁰⁹Bi can be used for spectrometric measurements of high-energy neutron spectra.The results of the present work will be of interest for an experimental verification of methods used to calculate the dose-dependent sensitivity of fissile-nuclide detectors and to develop promising types of personnel dosimeters.Translated from Atomnaya Énergiya, Vol. 69, No. 3, pp. 167–171, September, 1990.     

Use of moderate- and high-energy proton beams for laser pumping

Institute of Nuclear Research, Academy of Sciences of the USSR. Institute of General Physics, Academy of Sciences of the USSR. Translated from Atomnaya Énergiya, Vol. 71, No. 5, pp. 436–443, November, 1991.     

中子发生器产额稳定性

中子发生器的应用是很广泛的,这是因为中子发生器具有独特的优点:如可关断性和单能性.但是,中子发生器的产额稳定性和开机重复率差,达不到元素分析的领域的要求,电子学自动控制是一种简便易行效果显著的好方法.     

Preparation and verification of mixed high-energy neutron crosssection library for ADS

An accelerator-driven subcritical system(ADS)is driven by an external spallation neutron source, which is generated from a heavy metal spallation target to maintain stable operation of the subcritical core, where the energy of the spallation neutrons can reach several hundred megaelectron volts. However, the upper neutron energy limit of nuclear cross-section databases, which are widely used in critical reactor physics calculations, is generally 20 MeV.This is not suitable for simulating the transport of highenergy spallation neutrons in the ADS. We combine the Japanese JENDL-4.0/HE high-energy evaluation database and the ADS-HE and ADS 2.0 libraries from the International Atomic Energy Agency and process all the data files for nuclides with energies greater than 20 MeV. We use the continuous pointwise cross-section program NJOY2016 to generate the ACE-formatted cross-section data library IMPC-ADS at multiple temperature points. Using the IMPC-ADS library, we calculate 10 critical benchmarks of the International Criticality Safety Benchmark Evaluation Project manual, the 14-MeV fixed-source problem of the Godiva sphere, and the neutron flux of the ADS subcritical core by MCNPX. To verify the correctness of the IMPCADS, the results were compared with those calculated using the ENDF/B-VII.0 library. The results showed thatthe IMPC-ADS is reliable in effective multiplication factor and neutron flux calculations, and it can be applied to physical analysis of the ADS subcritical reactor core.     

Neutron yield in fissile targets irradiated with high-energy protons

Translated from Atomnaya Énergiya, Vol. 64, No. 2, pp. 133–137, February, 1988.     

Double differential cross sections of neutron and proton emission in neutron induced reactions on Fe

The energy spectra and double differential cross sections of neutron and proton emissions for n+^54,56,57,58Fe reactions are studied at incident neutron energies below 200 MeV based on the nuclear theoretical models, which are based on pre-equilibrium and equilibrium reaction theories. Theoretical calculated results are compared with existing experimental data.     

Comparison of 16 MeV proton, 14 MeV neutron and fission neutron damage in copper

The irradiation damage structures produced in high-purity copper by a fluence of $\text{3 × 10}{}^{16}$ particles/cm² of 16 MeV protons, 14 MeV neutrons, and fission neutrons ($\text{E > 1 MeV}$) were studied by transmission electron microscopy. The damage consists of vacancy-and-interstitial clusters or sessile Frank dislocation loops oriented on {111} planes of the copper matrix, and ranges in size from 25 Å (lower limit of resolution) to 200Å in diameter. p]The size-density distributions of the clusters in the 14 MeV neutron and 16 MeV proton irradiated samples were virtually identical, and the average size of the clusters in these two groups of specimens was substantially larger than was the case for those in the fission-neutron-irradiated copper.     

Magnetic force microscopy studies on the magnetic ordering in organic materials induced by high-energy proton irradiation

In this study, ferromagnetic microstructures in highly oriented pyrolytic graphite and superparamagnetic spots in polyimide foils were created by 2.25 MeV proton microbeam irradiation and characterized using atomic and magnetic force microscopy. For this purpose, graphite samples were irradiated with cross-like patterns of 15 μm × 15 μm size using ion fluences in the range of (0.003–2.5) × 10¹⁸ cm⁻². The irradiated crosses showed strong magnetic signals and a complex domain structure in the magnetic images depending on the geometrical dimensions of the crosses. Furthermore, polyimide foils were irradiated with microspots and fluences in the range of (0.016–3.1) × 10¹⁹ cm⁻². Magnetic force microscopy shows very strong phase shifts in these irradiated areas.