(p,p) non-Rutherford backscattering analysis of silicon carbide

In this paper, (p,p) non-Rutherford elastic backscattering (NBS) measurements with 1.6 MeV proton beams have been used to determine the areal density and C/Si stoichiometric ratio in 300–1000 nm SiC_x(H_y) films deposited on silicon substrates by Chemical Vapour Deposition (CVD) using two different gas sources, methane (CH₄) and ethylene (C₂H₄). At the same time, oxygen is also found in some of these samples. The results show that (p,p) NBS can be used to determine the areal density and C/Si ratio with a reasonable accuracy, especially when samples are thick or the terminal energy of the accelerator is low for analysis using a helium beam.     

Evaluation of non-Rutherford proton elastic scattering cross-section for magnesium

The experimental data available for magnesium (p,p) elastic scattering cross-section at angles and energies suitable for Ion Beam Analysis have been evaluated using the theoretical model approach together with additional measurements and benchmark experiments. The results obtained provide the evaluated differential cross-sections for magnesium (p,p) elastic scattering in the energy region up to 2.7 MeV.     

Evaluation of non-Rutherford proton elastic scattering cross section for silicon

The experimental data available for silicon (p,p) elastic scattering cross section have been reviewed. The analysis of the data was made using the theoretical model approach. The obtained results provide the evaluated differential cross sections for silicon (p,p) elastic scattering in the energy region up to 3.0 MeV.     

Evaluation of non-Rutherford proton elastic scattering cross section for nitrogen

The available experimental information on the proton elastic scattering from ¹⁴N in the energy range up to 5 MeV was compiled. The critical analysis of the revealed discrepancies was performed taking into account the applied experimental technique and possible error sources. Based on this, the apparently reliable experimental points were selected. Model calculations with comparison and fitting to the experimental data were used for parameterization of the cross section. The R-matrix theory was employed in the calculations, the phase shifts calculated for Saxon-Woods potential well being substituted for commonly used hard-sphere ones in order to take into account direct potential scattering. The result of the evaluation is that the required excitation functions for proton elastic scattering from nitrogen may be calculated for any scattering angle with reliability exceeding that for any individual measurement. The evaluated cross sections are provided by the SigmaCalc web site at www-nds.iaea.org/sigmacalc/.     

用于2.5MeV质子静电加速器ns脉冲装置的晶体管移相倍频器

本文介绍一个幅-相和相-幅特性均优良、能跟随加速器长期稳定运行的晶体管移相倍频器。它用于我所2.5MeV质子静电加速器ns脉冲装置的电子线路中。调节该器输出电压幅值和相位,能有效地控制频率为2MHz、宽度为10—20ns的脉冲束沿中心轨道横向偏转的张角大小和对称性。     

Determination of migration of ion-implanted helium in silica by proton backscattering spectrometry

Understanding the processes caused by ion implantation of light ions in dielectric materials such as silica is important for developing the diagnostic systems used in fusion and fission environments. Recently, it has been shown that ion-implanted helium is able to escape from SiO₂ films. To study this process in details, helium was implanted into the central part of a buried SiO₂ island up to a fluence of 4 × 10¹⁷ He/cm². The implanted helium could be detected in the SiO₂ island, if the oxide was insulated properly from the vacuum. The shape of the helium depth distributions was far from SRIM simulation because helium distributed in the whole 1 μm thick oxide layer. After the ion implantation, helium was observed only on the implanted spot. After nine months the implanted helium filled out the whole oxide island as it was expected from the high diffusivity.     

Co掺杂ZnO的快中子辐射损伤研究

用中子发生器上D-D反应的2.5MeV中子辐照Co掺杂ZnO和对照样品纯ZnO单晶。室温下测量了样品的X射线衍射谱、光致发光谱和透射光谱。结果表明,快中子辐照后的纯ZnO单晶中引入了氧空位(VO)和氧错位(OZn)缺陷,且有少量的锌填隙(Zni)和氧填隙(Oi)缺陷。Co掺杂ZnO中存在的Co以及钴氧化物纳米团簇由于快中子轰击而分解消失。快中子与替代Zn2+的Co2+的碰撞导致大量的Co2+离开ZnO晶格点位,导致Co掺杂ZnO中引入钴填隙杂质和锌空位(VZn)缺陷。中子辐照后的所有样品依然呈纤锌矿结构并沿c轴高度择优取向。表明纯ZnO和掺Co氧化锌半导体材料具有良好的抗辐照性能,在空间器件方面具有应用潜力,且有助于在ZnO点缺陷方面的研究。     

Proton elastic scattering cross sections of carbon,nitrogen and silicon for backscattering analysis in the energy range 0.7—2.5 MeV

Differential elastic scattering cross sections of 0.7—2.5 MeV protons for carbon, nitrogen and silicon have been determined at a scattering angle θ = 170°. Results from previous measurements near θ = 170° show large variations, of the order of 10–30% in the nonresonant regions. The purpose of the present investigations is to tabulate cross section data for backscattering analysis at a single scattering angle for many elements. Proton backscattering in the non-Rutherford energy region is more sensitive in the detection of C, N and many other light elements than other ion beam methods when a high background from the matrix is absent. Proton backscattering by using the present scattering cross sections and computer data analysis are outlined. The possible interference from other nuclear reactions is considered.     

Trace-impurity detection by Rutherford backscattering and nuclear resonance reactions

The use of a multisegment annular Si detector together with a multiline electronic processing system has led to an improvement of the detection limit in Rutherford backscattering spectrometry by about two orders of magnitude as compared to the standard single-line arrangement. With regard to nuclear reaction analysis, using particle/γ-ray resonance processes, similar large enhancements have been realized by an effective background-suppression system eliminating environmental and cosmic radiation. The present state of both experimental facilities will be demonstrated and compared with other trace-element detection techniques.     

Backscattering of 7Li-ions from oxygen below 6.25 MeV

Differential scattering cross sections for ⁷Li-ion scattering from oxygen between 2.75 and 6.25 MeV at a laboratory detection angle 170° have been determined. Rutherford scattering was observed below 3 MeV. Above 3.50 MeV the cross sections were found to vary from 1.07 to 0.18 of the Rutherford value. No sharp resonances were detected, ⁷Li-induced charged particle thick target reaction yields from carbon were investigated. From the point of view of Li-ion backscattering analysis, these reaction yields will cause significant interference above 5 MeV whenever major amounts of carbon are present in the sample under study.     

Quantitative microanalysis of matrix elements in biological samples by MeV proton scattering

A computer program, HCNO-MAP, has been specially designed to evaluate data from the analysis of biological samples done with a scanning nuclear microprobe. It produces quantitative maps of the elements ¹H, ¹²C, ¹⁴N and ¹⁶O from spectra of elastically backscattered and forward-scattered protons, at a speed of 0.3–0.4 s/pixel on a microVAX-II computer. Algorithms for the automatic evaluation used in the program are described. Results from analyses of plastic foils show that the program is capable of handling poor pulse statistics. A quantitative map of ¹²C in a cross section of a rootlet is presented.     

Measurement of spatial resolution of 11 MeV proton radiography

Proton radiography experiment with a Zumbro lens system was carried out on an 11 MeV proton cyclotron.The experimental results show that the image blurring is improved markedly. Clear images and good spatial resolution of the density step edges are obtained, which is important for hydrotest experiments, and the spatial resolution can achieve ~100 μm.     

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.     

Improvement of photonuclear reaction model below 140 MeV in the PHITS code

The photonuclear reaction model in the particle and heavy ion transport code system (PHITS) code is improved for incident photon energies below 140 MeV. Japanese Evaluated Nuclear Data Library (JENDL) Photonuclear Data File 2004 (JENDL/PD-2004) is adopted to determine the total reaction cross section. The statistical decay model after excitation of the nucleus in PHITS is improved by modifying the decay widths for light nuclei under the isospin selection rule to reasonably reproduce the proton and neutron emission in the de-excitation process. The quasideuteron disintegration process is newly introduced into PHITS to handle the photonuclear reaction up to 140 MeV of incident photon energy. The accuracy of the improvements was verified by comparison with the experimental literature data. The improved PHITS can contribute to various practical applications such as neutron dose estimation in X-ray therapy.     

Characterization of optical coatings by Rutherford backscattering spectrometry and elastic recoil detection analysis

The thicknesses of optical coatings vary between a few hundred Å and a few μm. Ion-beam techniques are ideally suited for probing this thickness range and in this work we discuss the use of Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA) for characterizing optical coatings such as ZnS, YF₃,Y₂O₃, C and Ge on silicon and germanium substrates. A general evaluation of the favourable features as well as the limitations of RBS and ERDA ion beam analysis for characterizing optical coatings is given.     

一台2.5MeV电子辐照加速器系统的屏蔽

介绍了一台能量2．5MeV、流强40mA、功率100kW的电子辐照加速器系统的屏蔽设计。实际测量结果表明：屏蔽外的辐射水平低于国家标准规定的限值,设计是合理的。