共查询到16条相似文献,搜索用时 0 毫秒
1.
L. L. Araujo P. L. Grande M. Behar J. H. R. dos Santos 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2002,190(1-4):79-83
In the present contribution, we report results on random stopping power and range straggling of 16O ions into amorphous Si target. The measurements were performed in a 300 keV–13.5 MeV energy interval by using the Rutherford backscattering technique together with a marker system. The present stopping results were compared with the TRIM predictions based on the Ziegler, Biersack and Littmark calculations, the theoretical values being always higher than the experimental ones. On the other hand, the calculated straggling data are compared with the Bohr predictions. For low energies, the calculated values over-estimate the experimental ones. For energies larger than 2 MeV, the experimental results became larger than the Bohr predictions. However, with increasing energies, the experimental results approach the Bohr values, and above 12 MeV a quite good theoretical experimental agreement was found. 相似文献
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110keV56Fe^1^+离子注入麦胚中的能量沉积分布 总被引:8,自引:3,他引:5
测量110KEv56Fe^1^+离子注入麦胚中的射程为257.1nm。根据测得的^5^6Fe^1^+离子相对浓度随深度的分布和注入离子的总面密度,求得了^5^6Fe^1^+离子绝对浓度随深度的分布。采用TRIM88程序计算得到了不同浓度上注入离子的阻止本领,从而求得了随深度的能量沉积分布。并讨论了细胞损伤的可能机理。 相似文献
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Helmut Paul 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(22):3421-3425
An overview is given of developments in the field of stopping power during the last few years, with particular emphasis on cases that seem to require further work. We discuss experimental results showing that stopping power for low energy protons, in metals and insulators, is not necessarily proportional to velocity. We mention that there is no discrepancy between the mean ionization potential derived from optical data or from stopping power. The problem of the stopping power of liquid water is discussed, considering both experiment and theory, and we find that recent experimental results and one of the theories are apparently too low. We discuss various types of theories for stopping power. We stress that in analyzing bulk backscattering spectra for stopping power, a low energy limit of validity must be stated. Using statistical analysis of experimental data for heavy ions in elemental solids, we find that the ATIMA and SRIM programs and the Hubert table are best in different regions of specific energy. 相似文献
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G. Kalliabakos S. Kossionides P. Misailides C. T. Papadopoulos R. Vlastou 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2000,170(3-4):467-473
A method for Cu and S profiling in patina layers was developed by applying a combination of nuclear reaction analysis (NRA) and Rutherford backscattering spectroscopy (RBS). The copper profiling was performed by using the 1327 keV γ-ray deexciting the third excited state to the ground state of 63Cu produced by the reaction 63Cu(p,p′γ)63Cu. For the determination of sulphur the 2230 keV γ-ray was used deexciting the first excited state to the ground state of 32S formed through the reaction 32S(p,p′γ)32S, which exhibits three sharp resonances at projectile energies 3.094, 3.195 and 3.379 MeV. The relevant cross-sections were measured in the energy range between 3.0 and 3.7 MeV in steps of 20 keV at 125° to the incident proton beam direction. The technique was tested using artificially produced and natural copper patina layers. Supporting information on the depth distribution of the constituent elements of the patina samples was obtained by p-RBS (Ep: 1.5 MeV, θ: 160°). 相似文献
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H. Erramli M. A. Misdaq G. Blondiaux 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2000,170(3-4):362-368
Charged particle activation analysis (CPAA) is able to analyze light elements such as carbon and oxygen at trace levels in semiconductor materials. This technique requires the knowledge of the stopping powers of these materials for channeled ions. The electronic energy loss for ions entering the crystal lattice in a random direction is well established. The electronic energy losses for protons, deuterons, 3He+ and 4He+ ions entering a 3.6 μm thick silicon single crystal along the 1 0 0 direction were measured by using the transmission of particles technique. Data obtained were compared with those obtained by other authors using theoretical and experimental methods. 相似文献
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Yanwen Zhang Gran Possnert 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2002,190(1-4):69-73
The mean stopping power of He, Be, C and Al in carbon has been studied in a continuous energy ranging from 100 to 800 keV per nucleon using a modified time of flight-energy elastic recoil detection analysis set-up. In order to eliminate the calibration problems of Si detectors associated with heavy ions, the time of flight section was used to measure recoil energy both before entering and after passing through the stopping foil. Consequently, the energy dependence of the stopping power was achieved with high precision. The effect of the foil thickness on the mean stopping power was investigated by tilting the stopping foil at different angles to the incoming particles to increase the effective foil thickness up to 22%. The stopping curves obtained at different tilting angles show a similar energy dependence with scattering less than 0.8% from each other, and no obvious thickness dependence is observed. Both the stopping power and the energy dependence are in good agreement with the literature data. Comparing with semi-empirical SRIM prediction, considerable discrepancies up to 6%, 10% and 8% in stopping values for Be, C and Al, respectively, are observed. 相似文献
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Annu Sharma Shyam Kumar S. K. Sharma P. K. Diwan N. Nath V. K. Mittal S. Ghosh D. K. Avasthi 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2000,170(3-4):323-328
The stopping powers of Mylar for several heavy ions covering Z=11 to 29 in the energy range 0.3 to 2.3 MeV/n have been measured using the elastic recoil detection technique and twin detector system. The technique provided a unique method to generate a variety of variable energy ion species utilizing a fixed energy 140 MeV Ag13+ primary beam from the Pelletron accelerator facility at Nuclear Science Center, New Delhi, India. Most of these measurements are new. The experimentally measured stopping power values have been compared with those calculated using LSS theory, Ziegler et al. formulation and Northcliffe and Schilling tabulations. Merits and demerits of these formulations are highlighted. Stopping power calculations using the Hubert et al. formulation have been extended successfully beyond its recommended range of validity, i.e. 2.5–500 MeV/n down to energies as low as 0.5 MeV/n. 相似文献
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Xifeng Qin Shuang LiFengxiang Wang Gang FuYi Liang 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(6):622-624
The range distribution for energetic 400 keV Er ions implanted in silicon-on-insulator (SOI) at room temperature were measured by means of Rutherford backscattering followed by spectrum analysis. The damage distribution and annealing behavior of implanted Er ions in SOI at the energy of 400 keV with dose of 5 × 1015 cm−2 were obtained by Rutherford backscattering technique. It has been found that the damage around the SOI surface had been almost removed after annealed in nitrogen atmosphere at 900 °C, and a lot of Er atoms segregate to the surface of sample with the recrystallization of surface Si of SOI sample after annealing at 900 °C. 相似文献
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Santiago Heredia-Avalos Rafael Garcia-Molina Isabel Abril 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2002,190(1-4):131-135
We have simulated the spatial evolution and energy loss of the fragments that result when swift molecular ions dissociate inside solid targets. In our calculations we have considered that these fragments undergo the following interactions: Coulomb repulsion (among like charged particles), stopping and wake forces (due to electronic excitations induced in the target), and nuclear scattering (with the target nuclei). We study the case of silicon targets irradiated with boron molecular or atomic ions; our results show that the main differences in the energy and spatial distributions of molecular fragments or atomic ions appear at shallow regions, and these tend to disappear at deeper depths. 相似文献
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Gintautas Dundulis Renatas Karalevicius Sigitas Rimkevicius Ronald F. Kulak Algirdas H. Marchertas 《Nuclear Engineering and Design》2006,236(2):201-210
The Ignalina NPP has a pressure suppression type of confinement, which is referred to as the accident localization system (ALS). The ALS prevents the release of the radioactive material from the NPP to the environment during a loss-of-coolant accident (LOCA). Ten water pools are located in the two ALS towers (five pools in each tower), which separate the dry well from the wet well. These water pools condense the accident-generated steam and prevent high overpressures in the compartments.The steam distribution device (SDD), with the vertical vent pipes (nozzles) that are inserted under the water of the condensing pools, connects the dry well and the wet well. In case of an accident, these components must be capable of withstanding the dynamic loads generated by a LOCA for successful pressure suppression function.This paper presents the transient analysis of the SDD and their connections to the vertical steam corridors following a LOCA. A thermo-hydraulic analysis of the SDD was performed using the state-of-the-art COCOSYS code to determine pressure and temperature histories resulting from a LOCA. The finite element code NEPTUNE was used to evaluate the structural integrity of the SDD and its supporting reinforced concrete wall. Results show that, although portions of the SDD undergo plastic response and the outside surface of the vertical steam corridor reinforced concrete wall cracks, the structural integrity of the SDD and wall are maintained during a LOCA. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(11):687-694
Two-dimensional current distribution in two regions—resistive electrode and plasma—are studied to optimize the shape of the resistive electrode in the MHD generator. Numerical computations are made for an example of potassium-seeded argon in non-equilibrium. As a first step, the performance is analyzed on an electrode of rectangular shape, and calculations performed more quantitatively than in the previous work by Maxwell et al. reveal that better uniformity is obtained for the current distribution along the electrode surface by increasing the thickness and resistivity of the electrode. The uniformity is found to improve also when the load current is increased. To diminish the power loss produced in the resistive layer, the electrode shape is optimized by eliminating from the rectangular resistive electrode the portion that produces the power loss. The electrode thus optimized in shape has an effective internal resistance that is independent of the value of the resistivity of the resistive layer. Consequently, in the optimized electrode, the power loss is independent of the uniformity of current distribution along the electrode surface, whereas it depends on the uniformity when a rectangular-shaped electrode is used. 相似文献
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《核技术(英文版)》2016,(4):86-92
The applications of carbon ion beam in tumor therapy have attracted more attention in recent years.Monte Carlo simulation is an important approach to obtain accurate radiotherapy parameters. In this work, a400 Me V/u carbon ion beam incident on water phantom was simulated with Gate/Geant4 tools. In methods, the authors set up a carbon ion beam source according to the experiment parameters of Haettner, defined the geometries and materials, set up the physics processes, and designed the means of information collection. In results,the authors obtained the longitudinal dose distribution, the lateral dose distribution, and the relative uncertainty of dose. The dose contributions of all kinds of fragments were calculated detailedly and compared with the Francis results. This work is helpful for people's understanding of the dose distributions produced by carbon ion beam and fragments in water. The simulation method is also significative for radiotherapy treatment planning of carbon ion beam, and it is easy to extend. For obtaining a special result, we may change the particle energy, particle type,target material, target geometry, physics process, detector,etc. 相似文献
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F. Revents L. Batet C. Llopis C. Pretel M. Salvat I. Sol 《Nuclear Engineering and Design》2007,237(1):54-63
Extensive technical literature exists aimed at establishing the requirements needed to qualify a Nuclear Power Plant model. Most of this literature is focused on qualifying a model for licensing uses. Less documentation is available nowadays on the requirements needed when an Integral Plant Model is used for supporting plant operation and control of an actual commercial facility, while fulfilling its goals of safety and competitiveness. For the last 15 years the Technical University of Catalonia (UPC) has been working in this field along with Asociación Nuclear Ascó–Vandellòs (ANAV), which is a utility that presently runs three operating PWRs. The paper develops an advanced qualification process (AQP) of plant models for operation support, introduces the concept of plant configuration and explains how this activity complements other usual validation tasks. 相似文献
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To estimate the success criteria of an operator's action time for a probabilistic safety/risk assessment (PSA/PRA) of a nuclear power plant, the information from a safety analysis report (SAR) and/or that by using a simplified simulation code such as the MAAP code has been used in a conventional PSA. However, the information from these is often too conservative to perform a realistic PSA for a risk-informed application. To reduce the undue conservatism, the use of a best-estimate thermal hydraulic code has become an essential issue in the latest PSA and it is now recognized as a suitable tool. In the same context, the ‘ASME PRA standard’ also recommends the use of a best-estimate code to improve the quality of a PSA. In Korea, a platform to use a best-estimate thermal hydraulic code called the MARS code has been developed for the PSA of the Korea standard nuclear power plant (KSNP). This study has proposed an estimation method for an operator's action time by using the MARS platform. The typical example case is a small break loss of coolant accident without the high pressure safety injection system, which is one of the most important accident sequences in the PSA of the KSNP. Under the given accident sequence, the operator has to perform a recovery action known as a fast cooldown operation. This study focuses on two aspects regarding an operator's action; one is how they can operate it under some restrictions; the other is how much time is available to mitigate this accident sequence. To assess these aspects, this study considered: (1) the operator's action model and (2) the starting time of the operation. To show an effect due to an operator's action, three kinds of control models (the best-fitting, the conservative, and the proportional-integral) have been assessed. This study shows that the developed method and the platform are useful tools for this type of problem and they can provide a valuable insight related to an operator's actions. 相似文献
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J. Birchley T. Haste H. Bruchertseifer R. Cripps S. Güntay B. Jckel 《Nuclear Engineering and Design》2005,235(15):1607-1633
Phébus-FP is a multi-national collaborative programme comprising four integral and one debris bed melting and fission product release experiments. The integral experiments simulate the heat-up, degradation and fission product release and transport, thermal hydraulic response, aerosol behaviour and iodine chemistry in the containment. The total programme, including interpretation effort, runs from 1993 to ca. 2007. The experiments demonstrated new characteristics of core degradation, fission product and iodine chemistry and accident integral behaviour. PSI has participated extensively through planning support, interpretation of data from the experiments and analyses of the results to establish confidence in the models being used for plant application. A significant part of the PSI effort was performed to interpret the significance of silver iodide as an effective retention agent under typical reactor conditions. The conclusions are of an interim nature, since the data reduction and interpretation are not yet complete. The significance of the Phébus results for plant safety will be fully realised only after successful benchmarking of the computer codes against Phébus, and application to plant sequences. Such work remains in progress within the Phébus project and in various national programmes. 相似文献