快分子离子通过碳膜产生负离子的研究

本文介绍快分子离子在固体膜内的碰撞机制和负离子的产生,测量了不同能量的分子离子H~+_2、D~+_2通过碳膜产生的负离子并与原子离子产生的负离子作了比较,对结果进行了定性分析和讨论。     

Numerical study on the loss of fast ions produced by minority ion cyclotron resonance heating in EAST

The classical prompt loss of fast ions produced by minority ion cyclotron resonance heating(ICRH)is studied by a guiding center orbit following code in the Experimental Advanced Superconducting Tokamak(EAST).It is found that the loss of fast ions produced by ICRH mainly appears in both ends of the resonance layer,while the loss of fast ions in the middle resonance layer is very small.The dominant fast loss comes from trapped ions,rather than from passing ions.Controlling the location of resonance layer at the plasma core may be more beneficial to the EAST tokamak ICRH.In addition,the loss distribution of fast ions is studied.The results show that the fast ions are mainly lost near the midplane in the poloidal direction,but almost uniformly in the toroidal direction.Moreover,we investigate the dependence of fast ion loss on the ICRH power.The simulation results show that the loss fraction of fast ions in both ends of the resonance region increases with the ion cyclotron range of frequencies(ICRF)power,but barely affects the loss of fast ions in the middle region.     

Effects of fast ions produced by ICRF heating on the pressure at EAST

Ion cyclotron resonance heating(ICRH),which can produce fast ions,is an important auxiliary heating method at EAST.To analyze the effect of ICRH-induced fast ions on the plasma pressure at EAST,simulations are performed using TRANSP and TORIC codes.It is found that the ICRF-induced fast ion pressure cannot be negligible when the ICRF power is sufficiently high.The magnitude of the total ion pressure can be raised up to 60%of the total pressure as the input power rises above 3 MW.The pressure profile is also significantly modified when the resonant layer is changed.It is shown that by changing the wave frequency and antenna position,the total ion pressure profile can be broadened,which might provide an option for profile control at EAST.     

Startup scheme optimization and flow instability of natural circulation lead-cooled fast reactor SNCLFR-100

Owing to the inherent instability of the natural circulation system,flow instability can easily occur during the operation of a natural circulation lead-cooled fast reactor,especially during the startup phase.A compre-hensive startup scheme for SNCLFR-100,including pri-mary and secondary circuits,is proposed in this paper.It references existing more mature startup schemes in various reactor types.It additionally considers the restriction con-ditions on the power increase in other schemes and the characteristics of lead-based coolant.On this basis,the multi-scale coupling code ATHLET-OpenFOAM was used to study the flow instability in the startup phase under different power-step amplitudes and power duration times.The results showed that obvious flow instability phenom-ena were found in the different startup schemes,such as the short-term backflow phenomenon of the core at the initial time of the startup.Moreover,an obvious increase in the flow rate and temperature to the peak value at the later stage of a continuous power rise was observed,as well as continuous oscillations before reaching a steady state.It was determined that the scheme with smaller power-step amplitude and a longer power duration time requires more time to start the reactor.Nevertheless,it will be more conducive to the safe and stable startup of the reactor.     

Preliminary Results of Drift Instability by Fast Optical Images in KT-5D Toroidal Plasma

Drift instability in plasma generated by electron cyclotron resonance （ECR） in KT- 5D device was investigated by using a fast camera and Langmuir probes. The similarity between the distribution of light intensity from the images and the plasma pressure indicates a nearly linear relationship. The discharge images taken by the camera and the plasma parameters measured by the probes also indicate the existence of low frequency turbulent events with a time scale less than a few mini-seconds.     

Irradiation effects in polycarbonate induced by 2.1 GeV Kr ions

Polycarbonate foil stacks were irradiated with 2.1 GeV Kr ions under vacuum at room temperature. The modifications in chemical structure induced by the irradiation were studied by means of Fourier transform infrared (FTIR) and ultraviolet visible (UV/VIS) spectroscopies. FTIR measurements reveal that material degradations through bond breaking are the main effects. Alkyne end groups are produced by the irradiation. UV/VIS measurements indicate a shifting of the absorption edge from ultraviolet towards visible, and a strong increase of absorbance in the ultraviolet and visible regions. The changes in absorbance induced by the irradiation at wavelengths of 380 nm, 450 nm and 500 nm scale well with Sc"(Sc is electronic energy loss) where the value of n increases from 1.69 to 2.02 with increasing of the wavelength. The results are briefly discussed.     

Infrared study of astrophysical ice analogues irradiated by swift nickel ions

Water, carbon oxide, carbon dioxide, and ammonia ices are known to be pervasive constituents of the solar system and the interstellar medium. These ices and ice-covered surfaces are exposed to bombardment by energetic projectiles like photons, electrons, and ions. Laboratory experiments have been carried out to study the effects of such irradiation. However, there is a clear lack of information about the interaction of heavy ion components of solar/stellar wind and galactic cosmic rays (e.g. Fe) with ices in the keV to GeV energy range. The objective of this work is to study the effects produced in astrophysical ices by highly charged nickel ions at relatively high energy (∼50-500 MeV) in the electronic energy loss regime, and to compare them with those produced by protons, photons, and electrons. Our results for CO₂ and CO indicate that sputtering induced by heavy ions can be an important mechanism to desorb molecules in astrophysical environments.     

活化法测量溅射Au原子的各向异性

溅射的空间分布和溅射率的研究不仅是检验各种溅射机制的重要手段而且与许多溅射的应用问题紧密相联。如利用溅射刻绘集成电路所需的复杂图样、单晶表面加工和薄靶制备技术等。此外一些分析技术也有赖于溅射的角分布和能量分布知识。 有关溅射理论的基础是由Sigmund在1969年提出的线性级联碰撞理论。根据他的理论引致的空间溅射角分布是余弦形状的对称分布,但一些实验表明这一理论与实验有明显的偏     

重离子辐照冬小麦诱变效应的研究

利用3.2—75MeV/u4个能量、2×108—12×108cm–24个剂量的O和C重离子处理3个冬小麦品种,1612研究其诱变效应。结果表明,M1代的生物损伤随剂量的增加而加大;8MeV/u能量的损伤要比高能75MeV/u时大;8MeV/u较易出现在高能75MeV/u离子和γ辐射中未见的条状叶绿素缺失损伤,此结果未见相关报导。M2代诱变效果显著,突变谱宽,有益突变(早熟、矮杆、穗形)频率明显高于γ射线,且较易诱发早抽穗性状变异。     

Ultrafast band-structure variations induced by fast Au ions in BeO

Auger-electron spectra associated with Be atoms in the pure metal lattice and in an oxide have been investigated for 1.8 MeV/u ¹²⁹Au⁴¹⁺ ions and 2.7 keV primary electrons. The excitation and local energy transfer by such fast primary particles in solids is dominated by electronic processes. The electron-induced spectrum is compared to calculated band-structure results and it is relatively well understood. For the heavy-ion case, however, we observe a significant variation of the Auger electron spectrum, related to a variation of the electronic band structure. This spectrum points to a formation of a metal-like meta-stable electronic density of states.     

Velocity effect of swift heavy ions in graphite studied by Raman spectroscopy

Highly oriented pyrolytic graphite (HOPG) samples were irradiated with swift heavy ions (Ar, Kr, Bi, U) of fluences between 10¹¹ and 10¹³ ions/cm² in energy range MeV-GeV. The irradiated samples were analyzed by Raman spectroscopy with laser wavelength of 532.2 nm. It is shown that the ratio between the integrated intensities of the disorder-induced D and the original G Raman bands which denotes the degree of the damage induced by ion irradiation increases as a function of ion fluence as well as the electronic energy loss. This agrees with the previous reports. However, quantitative analysis of the peak intensity at a fixed fluence discloses that ion velocity is also a significant parameter in determination of damage. The conclusion is that the extent of discontinuity of ion track may change with ion velocity besides the electronic energy loss. Considering the radial distribution of the energy deposited on the matter being velocity dependent, the energy density which combines the influence of the electronic energy loss and ion velocity may be more suitable for explaining the effect induced by swift heavy ions.     

MeV碳离子及碳团簇C2+注入PC膜的光吸收谱研究

研究了MeV碳离子及碳团簇C2 注入的聚碳酸酯(Polycarbonate,PC)膜.光吸收谱研究结果表明,离子注入在聚合物近表面产生了断键及缺陷,改变了PC的光吸收性质,在可见光区域有较明显的吸收,并且吸收边与注入离子的种类、能量和注量密切相关.X射线光电子谱(X-ray photoelectron spectroscopy,XPS)对PC的近表面结构和成分配比进行了分析,证实了以上的结论.     

高能氩离子在钇铁石榴石中引起的非晶化研究

用倾斜样品Ｘ射线学和饱和磁化强度测量，研究了９６０ＭｅＶ氩离子在多晶钇铁石榴（ＹＩＧ）Ｙ３Ｆｅ５Ｏ１２中引起的非晶化过程。分析结果表明，９６０Ｍｅ氩离子辐照引起ＹＩＧ晶态→非昌态转变是一个逐渐的过程，在这个过程中电子能损起主导作用但也需要一定的辐照剂量。     

Electron emission by highly charged neon and xenon ions on fusion-relevant tungsten and graphite surfaces

Here we report highly charged ⁴⁰Ne^q+ (q = 3-8) and ¹²⁹Xe^q+ (q = 10-30) ion-induced secondary electron emission on the tungsten and highly oriented pyrolytic graphite (HOPG) surfaces. The total secondary electron yield is measured as a function of the potential energy of incident ion. The experimental data is used to separate contributions of kinetic and potential electron yields. We estimate roughly 10% of ion’s potential energy is consumed in potential electron emission. The rest of the ion’s potential energy is responsible for the sputtering and material modification.     

Measurement of transient neutral gas puff pressure in the NUDT_IPPTx by a fast ionization gauge

A gas injector was designed for the 400 J/pulse prototype of the planar inductive pulsed plasma thruster (IPPT) developed by the National University of Defense Technology (NUDT_IPPTx). As the gas puff distribution over the coil surface is critical to the NUDT_IPPTx functioning efficiently, a fast ionization gauge was developed to investigate the neutral gas pressure profiles to seek the critical time when the thruster is ignited. The gauge was calibrated for argon by using a capacitance manometer. Time-resolved pressure profiles have been acquired in the condition of the gas puff mass matching with the discharge energy and the drive coil parameters of the NUDT_IPPTx. It is demonstrated that the gas injector can supply a gas puff with a sufficiently steep (d_p/d_t ≈ 770 kPa s^-1 ) leading and trailing edge, and the gas puff can be compressed against the drive coil as expected. The critical ignition moment is considered to appear at some instant between 525 μs and 650μs after the valve trigger.     

快重离子在石墨中引起表面及体径迹的STM研究

用多种快重离子辐照高定向石墨（HOPG），借助扫描隧道显微镜（STM）系统地研究了表面及体内缺陷，结果表明，离子在表面及解理面上都形成了小丘状的缺陷，且在表面较容易形成，可以用非连续损伤径迹结构来对其进行解释。     

Assembling Stabilization of the Rayleigh-Taylor Instability by the Effects of Finite Larmor Radius and Sheared Axial Flow

The assembling stabilizing effect of the finite Larmor radius (FLR) and the sheared axial flow (SAF) on the Rayleigh-Taylor instability in Z-pinch implosions is studied by means of the incompressible finite Larmor radius magnetohydrodynamic (MHD) equations. The finite Larmor radius effects are introduced in the momentum equation with the sheared axial flow through an anisotropic ion stress tensor. In this paper a linear mode equation is derived that is valid for arbitrary kL, where k is the wave number and L is the plasma shell thickness. Numerical solutions are presented. The results indicate that the short-wavelength modes of the RayleighTaylor instability are easily stabilized by the individual effect of the finite Larmor radius or the sheared axial flow. The assembling effects of the finite Larmor radius and sheared axial flow can heavily mitigate the Rayleigh-Taylor instability, and the unstable region can be compressed considerably.     

中国实验快堆的安全特性

钠冷快堆因钠具有好的热物理特性而具有固有安全性,同时也因钠是活泼的碱金属,也难免会有钠的泄漏、钠火和钠水反应等工业事故.本文介绍了中国实验快堆利用钠冷快堆的固有安全性,装设了单靠自然循环和自然对流的事故余热导出系统等多项非能动安全系统及完善的能动安全系统,其安全性达到了第Ⅳ代先进核能系统的安全要求.对于大型快堆,因其保...     

Interface mixing induced by swift heavy ions at metal-oxide/silicon interfaces

It was observed previously that ceramic/ceramic bilayers were very sensitive with respect to the electronic stopping power S_e, i.e. strong interface mixing, scaling with , occurred if a threshold S_ec was exceeded. The threshold seemed to be determined by the higher track formation threshold of two constituents forming the bilayer. Although no track formation has been observed in crystalline Si even for Uranium projectiles, interface mixing was observed previously for some Si-multilayers.

In this paper we report on the interface mixing of NiO, Fe₂O₃, TiO₂ on Si due to irradiation with 90–350 MeV Ar-, Kr-, Xe- and Au-ions at 80 K at fluences up to 9E15 ions/cm². Interface mixing, analyzed by means of Rutherford Backscattering Spectrometry (RBS), is found for these bilayers, too. But the threshold for intermixing is significantly higher compared to the ceramic/ceramic bilayers. This observation could be an evidence for the threshold being determined by the Si-layer. In contrast to NiO/Si and Fe₂O₃/Si, where an usual random walk mixing Δσ² = kΦ was observed, the interface broadening Δσ² for TiO₂/Si is found to scale nonlinearly with the ion fluence, which indicates that mixing is driven by a chemical solid-state reaction. At higher fluences plateaus form at the low energy Ni-edge of the RBS spectra. The plateaus indicate phase formation. X-Ray diffraction spectra does not show any evidence for new crystalline phases.