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1.
A new system for performing radiation effects microscopy (REM) has been developed at Sandia National Laboratory in Albuquerque. This system combines two entirely new concepts in accelerator physics and nuclear microscopy. A radio frequency quadrupole (RFQ) linac is used to boost the energy of ions accelerated by a conventional Tandem Van de Graaff–Pelletron to velocities of 1.9 MeV/amu. The electronic stopping power for heavy ions is near a maximum at this velocity, and their range is 20 μm in Si. These ions therefore represent the most ionizing form of radiation in nature, and are nearly ideal for performing single event effects testing of integrated circuits. Unfortunately, the energy definition of the RFQ-boosted ions is rather poor ( a few %), which makes problematic the focussing of such ions to the submicron spots required for REM. To circumvent this problem, we have invented ion electron emission microscopy (IEEM). One can perform REM with the IEEM system without focussing or scanning the ion beam. This is because the position on the sample where each ion strikes is determined by projecting ion-induced secondary electrons at high magnification onto a single electron position sensitive detector. This position signal is then correlated with each REM event. The IEEM system is now mounted along the beam line in an axial geometry so that the ions pass right through the electron detector (which is annular), and all of the electrostatic lenses used for projection. The beam then strikes the sample at normal incidence which results in maximum ion penetration and removes a parallax problem experienced in an earlier system. Details of both the RFQ-booster and the new axial IEEM system are given together with some of the initial results of performing REM on Sandia-manufactured radiation hardened integrated circuits.  相似文献   

2.
The radiation hardness of polysiloxane based scintillators has been measured by ion beam induced luminescence (IBIL). The light intensity as a function of the irradiation fluence with an He+ beam at 1.8 MeV (1.0 μA/cm2) has been measured on undoped polymers synthesized with different amounts of phenyl units and on polysiloxanes doped with two different dye molecules (BBOT and Lumogen Violet) sensitizing the scintillation yield.  相似文献   

3.
4.
Monazite is a potential matrix for conditioning minor actinides arising from spent fuel reprocessing. The matrix behavior under irradiation must be investigated to ensure long-term containment performance. Monazite compounds were irradiated by gold and helium ions to simulate the consequences of alpha decay. This article describes the effects of such irradiation on the structural and macroscopic properties (density and hardness) of monazites LaPO4 and La0.73Ce0.27PO4. Irradiation by gold ions results in major changes in the material properties. At a damage level of 6.7 dpa, monazite exhibits volume expansion of about 8.1%, a 59% drop in hardness, and structure amorphization, although Raman spectroscopy analysis shows that the phosphate-oxygen bond is unaffected. Conversely, no change in the properties of these compounds was observed after He ion implantation. These results indicate that ballistic effects predominate in the studied dose range.  相似文献   

5.
A short review is presented concerning problems of ion beam processing of single crystalline silicon carbide. Emphasis is given to recent results on point defects, extended defects, amorphisation and recrystallisation, electrical activation of dopant atoms, and metallisation.  相似文献   

6.
本文采用氚离子束标记法,对茯苓聚糖进行了标记,放射性比活性达1.81—2.07TBq/mmol。药物动力学研究证明~3H-茯苓聚糖尿素液口服灌喂小白鼠,按一定时间在尾部静脉取血样作放射性分析。得到的药-时曲线适合于双定模型。  相似文献   

7.
Single crystals of z- and x-cut LiNbO3 were irradiated at room temperature and 15 K using He+- and Ar+-ions with energies of 40 and 350 keV and ion fluences between 5 × 1012 and 5 × 1016 cm−2. The damage formation investigated with Rutherford backscattering spectrometry (RBS) channeling analysis depends on the irradiation temperature as well as the ion species. For instance, He+-irradiation of z-cut material at 300 K provokes complete amorphization at 2.0 dpa (displacements per target atom). In contrast, 0.4 dpa is sufficient to amorphize the LiNbO3 in the case of Ar+-irradiation. Irradiation at 15 K reduces the number of displacements per atom necessary for amorphization. To study the etching behavior, 400 nm thick amorphous layers were generated via multiple irradiation with He+- and Ar+-ions of different energies and fluences. Etching was performed in a 3.6% hydrofluoric (HF) solution at 40 °C. Although the etching rate of the perfect crystal is negligible, that of the amorphized regions amounts to 80 nm min−1. The influence of the ion species, the fluence, the irradiation temperature and subsequent thermal treatment on damage and etching of LiNbO3 are discussed.  相似文献   

8.
Synthesis and structural studies of nanocrystalline silicon grown in pulsed laser deposited SiOX films is reported. The effect of high energy heavy ion beam irradiation on these films is studied using 100 MeV Ag ions. The structural studies were carried out using micro Raman spectroscopy, GAXRD, FTIR, TEM, HRTEM, SAED and EDX. The occurrence of phase separation in non-stoichiometric silicon oxide by means of ion beam irradiation leading to the formation of silicon nanocrystals in the films is confirmed by the results. HRTEM results reveal the structure of silicon phase formed after ion beam treatment and the particle size can be controlled up to 2-3 nm. A detailed analysis by micro Raman and HRTEM studies suggest the presence of crystallite size distribution. The results of GAXRD and SAED confirm the formation of cubic phase of silicon with two different lattice parameters. The studies conclude that the size of the nanocrystals can be controlled by varying deposition and ion irradiation parameters.  相似文献   

9.
This work explored a potential new model dispersion fuel form consisting of an actinide material embedded in a radiation tolerant matrix that captures fission products (FPs) and is easily separated chemically as waste from the fuel material. To understand the stability of this proposed dispersion fuel form design, an idealized model system composed of a multilayer film was studied. This system consisted of a tri-layer structure of an MgO layer sandwiched between two HfO2 layers. HfO2 served as a surrogate fissile material for UO2 while MgO represented a stable, fissile product (FP) getter that is easily separated from the fissile material. This type of multilayer film structure allowed us to control the size of and spacing between each layer. The films were grown at room temperature by e-beam deposition on a Si(1 1 1) substrate and post-annealed annealing at a range of temperatures to crystallize the HfO2 layers. The 550 °C annealed sample was subsequently irradiated with 10 MeV Au3+ ions at a range of fluences from 5 × 1013 to 3.74 × 1016 ions/cm2. Separate single layer constituent films and the substrate were also irradiated at 5 × 1015 and 8 × 1014 and 2 × 1016, respectively. After annealing and irradiation, the samples were characterized using atomic force imaging techniques to determine local changes in microstructure and mechanical properties. All samples annealed above 550 °C cracked. From the AFM results we observed both crack healing and significant modification of the surface at higher fluences.  相似文献   

10.
This paper reports on the fabrication and characterization of a high purity monocrystalline diamond detector with buried electrodes realized by the selective damage induced by a focused 6 MeV carbon ion beam scanned over a pattern defined at the micrometric scale. A suitable variable-thickness mask was deposited on the diamond surface in order to modulate the penetration depth of the ions and to shallow the damage profile toward the surface. After the irradiation, the sample was annealed at high temperature in order to promote the conversion to the graphitic phase of the end-of range regions which experienced an ion-induced damage exceeding the damage threshold, while recovering the sub-threshold damaged regions to the highly resistive diamond phase. This process provided conductive graphitic electrodes embedded in the insulating diamond matrix; the presence of the variable-thickness mask made the terminations of the channels emerging at the diamond surface and available to be connected to an external electronic circuit. In order to evaluate the quality of this novel microfabrication procedure based on direct ion writing, we performed frontal Ion Beam Induced Charge (IBIC) measurements by raster scanning focused MeV ion beams onto the diamond surface. Charge collection efficiency (CCE) maps were measured at different bias voltages. The interpretation of such maps was based on the Shockley-Ramo-Gunn formalism.  相似文献   

11.
A computer code for the simulation of ion beam irradiation of nanostructures has been developed. The code simulates the transport of energetic ions through matter by means of a Monte Carlo algorithm, similar to the often-used TRIM code (Ziegler et al. (1985) [1]). New effects occur compared to bulk, when irradiating nanostructures, which are of the same size as the ion range or the damage cascade. To account for these effects, the target in our code does not consist of layers like in TRIM but can be defined as an arbitrary 3-dimensional structure. This allows to obtain more accurate 3D distributions of implanted ions and implantation damage for nanostructures, which cannot be described by a stack of layers. We demonstrate the functionality of the code by comparing simulations with ion beam implantation into nanowires.  相似文献   

12.
辐射化学是连接辐射物理与辐射生物学的时空桥梁,其理论、模型和实验方法对促进辐射生物学的研究和发展起到不可缺少的重要作用。辐射诱导的化学变化不仅是辐射生物学效应的早期事件,在辐射诱导的DNA损伤与修复、生物辐射敏感修饰剂、辐射诱导的活性氧分子代谢和功能等研究领域都扮演重要角色。随着辐射生物学效应研究朝着系统辐射生物学方向发展,辐射生物学效应发生机理的精确研究和定量描述更需要辐射化学的方法和手段支持。  相似文献   

13.
Because of their sensitivity to the electronic energy loss of swift heavy ions, we have investigated the high energy ion beam mixing of oxide layer systems. In this paper we present a summary of the results and first steps towards interpretation and modelling of the observed phenomena. As was also observed in the case of track formation, mixing was found to occur only if the electronic energy loss exceeds a threshold value. The threshold is determined by the less sensitive material, which is a clear hint that both sides of the interface must have been molten, to enable for effective interdiffusion. This interpretation is supported by the estimated interdiffusion constants which indeed lie in the range known for liquid state diffusion.  相似文献   

14.
低能电子束循环辐射硫化天然橡胶乳液   总被引:2,自引:0,他引:2  
应用250keV低能电子束循环辐射硫化二丙烯酸壬酯(1,9-nonanedilo diacrylate,NDDA)敏化的天然橡胶乳液,探讨了影响低能电子束循环辐射硫化天然橡胶乳液的因素。结果表明,提高电子束束流,可缩短辐射硫化时间;40%的天然橡胶乳液更适合低能电子束的辐射硫化;适当提高循环乳液的重量有利于辐射硫化乳液的质量控制。  相似文献   

15.
To elucidate the underlying physics of ion beam assisted deposition (IBAD), irradiation damage effects in magnesia (MgO) and yttria-stabilized zirconia (YSZ) were investigated. Ion irradiations were performed on MgO and YSZ single crystals of three low-index crystallographic orientations using 100 and 150 keV Ar+ ions over a fluence range from 1 × 1014 to 5 × 1016 Ar/cm2. Damage accumulation was analyzed using Rutherford backscattering spectrometry combined with ion channeling. Damage evolution with increasing ion fluence proceeded via several characteristic stages and the total damage exhibited a strong dependence on crystallographic orientation. For both MgO and YSZ, damage anisotropy was maximal at a stage when the damage saturated, with the (1 1 0) crystallographic orientation being the most radiation damage resistant. The Ion/Atom ratio deposition parameter reported for IBAD of MgO and YSZ films was found to correlate with the damage plateau stage described above. Finally, the role of the Ion/Atom ratio is discussed in terms of radiation damage anisotropy mechanism.  相似文献   

16.
陈昌明  潘浩昌 《核技术》1999,22(2):65-68
将组合技术和离子束技术结合起来。用于硅基发光材料的研究。用组合离子束技术在硅基材料上制备了64个直径为2mm的单元-材料芯片,并对硅基材料芯片各进行了卢瑟辐背散射,质子弹性散射和扫描阴极射一发光特性分析。  相似文献   

17.
电子束辐射加工吸收剂量标准的测量系统   总被引:4,自引:0,他引:4  
张利民  顾继青 《核技术》1995,18(4):238-246
  相似文献   

18.
In order to develop the hydrogels meant for the drug delivery, we have prepared psyllium-N-vinylpyrrolidone (NVP) based hydrogels by radiation induced crosslinking. Polymers were characterized with SEMs, FTIR and swelling studies. Swelling of the hydrogels was studied as a function of monomer concentration, total radiation dose, temperature, pH and [NaCl] of the swelling medium. The swelling kinetics of the hydrogels and release dynamics of anticancer model drug (5-fluorouracil) from the hydrogels have been carried out for the evaluation of swelling and drug release mechanism. It has been observed that diffusion exponent ‘n’ have 0.8, 0.9, 0.8 and gel characteristics constant ‘k’ have 9.22 × 10−3, 2.06 × 10−3, 11.72 × 10−3 values for the release of drug from the drug loaded hydrogels in distilled water, pH 2.2 buffer and pH 7.4 buffer, respectively. The present study shows that the release of drug from the hydrogels occurred through Non-Fickian diffusion mechanism.  相似文献   

19.
Unique data for Australia on the concentration of selected metals in fine particle ambient air pollution is presented for urban, industrial and rural sites along 300 km section of the eastern coast line of Australia around Sydney. IBA techniques were used to determine over 25 different chemical species in the air including, H, C, N, O, F, Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Br, Se and Pb. This included many trace metals at concentrations around 1 ng/m3 of air sampled.  相似文献   

20.
Spectroscopic investigations were carried out on electron beam irradiated sodium barium borosilicate glasses, which is the base glass for immobilization of nuclear high level radioactive waste, generated from the research reactors at Bhabha Atomic Research Centre, Trombay. This was done in order to access the defects generated in it under long term irradiation. Electron paramagnetic resonance was used to identify the defect centers generated in the borosilicate glass after irradiation. In addition, positron annihilation spectroscopy and infrared investigations were done on the samples to evaluate the radiation induced changes in the glass. It was found that, boron-oxygen and silicon based hole centers along with E′ centers are getting formed in the glass after irradiation due to the breaking of the SiO bonds at regular tetrahedron sites of SiOSi. The positron annihilation spectroscopy data gave an idea regarding the free volume size and fraction of the glasses before and after irradiation. It was seen that, after irradiation the free volume size in the glass increased with creation of additional sites. Microwave power variation and temperature variation studies suggested the formation of at least five different radicals in the irradiated glasses. The spin Hamiltonian parameter of all the radical species were determined by computer simulation. An electron paramagnetic resonance spin counting technique was employed to evaluate the defect concentration in the glasses after irradiation.  相似文献   

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